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Sample records for 13c hyperfine structure

  1. Hyperfine structure in the J = 1-0 transitions of DCO^+, DNC, and HN13C: astronomical observations and quantum-chemical calculations

    NASA Astrophysics Data System (ADS)

    van der Tak, F. F. S.; Müller, H. S. P.; Harding, M. E.; Gauss, J.

    2009-11-01

    Context: Knowledge of the hyperfine structure of molecular lines is useful for estimating reliable column densities from observed emission, and essential for the derivation of kinematic information from line profiles. Aims: Deuterium bearing molecules are especially useful in this regard, because they are good probes of the physical and chemical structure of molecular cloud cores on the verge of star formation. However, the necessary spectroscopic data are often missing, especially for molecules which are too unstable for laboratory study. Methods: We have observed the ground-state (J = 1{-}0) rotational transitions of DCO^+, HN13C and DNC with the IRAM 30 m telescope toward the dark cloud LDN 1512 which has exceptionally narrow lines permitting hyperfine splitting to be resolved in part. The measured splittings of 50-300 kHz are used to derive nuclear quadrupole and spin-rotation parameters for these species. The measurements are supplemented by high-level quantum-chemical calculations using coupled-cluster techniques and large atomic-orbital basis sets. Results: We find eQq = + 151.12 (400) kHz and CI = -1.12 (43) kHz for DCO^+, eQq = 272.5 (51) kHz for HN13C, and eQq(D) =265.9 (83) kHz and eQq(N) = 288.2 (71) kHz for DNC. The numbers for DNC are consistent with previous laboratory data, while our constants for DCO+ are somewhat smaller than previous results based on astronomical data. For both DCO+ and DNC, our results are more accurate than previous determinations. Our results are in good agreement with the corresponding best theoretical estimates, which amount to eQq = 156.0 kHz and CI = -0.69 kHz for DCO^+, eQq = 279.5 kHz for HN13C, and eQq(D) = 257.6 kHz and eQq(N) = 309.6 kHz for DNC. We also derive updated rotational constants for HN13C: B = 43 545.6000 (47) MHz and D = 93.7 (20) kHz. Conclusions: The hyperfine splittings of the DCO^+, DNC and HN13C J = 1{-}0 lines range over 0.47-1.28 km s-1, which is comparable to typical line widths in pre

  2. Characterization of hyperfine interaction between an NV electron spin and a first-shell 13C nuclear spin in diamond

    NASA Astrophysics Data System (ADS)

    Rao, K. Rama Koteswara; Suter, Dieter

    2016-08-01

    The nitrogen-vacancy (NV) center in diamond has attractive properties for a number of quantum technologies that rely on the spin angular momentum of the electron and the nuclei adjacent to the center. The nucleus with the strongest interaction is the 13C nuclear spin of the first shell. Using this degree of freedom effectively hinges on precise data on the hyperfine interaction between the electronic and the nuclear spin. Here, we present detailed experimental data on this interaction, together with an analysis that yields all parameters of the hyperfine tensor, as well as its orientation with respect to the atomic structure of the center.

  3. Computational and ESR studies of electron attachment to decafluorocyclopentane, octafluorocyclobutane, and hexafluorocyclopropane: electron affinities of the molecules and the structures of their stable negative ions as determined from 13C and 19F hyperfine coupling constants.

    PubMed

    ElSohly, Adel M; Tschumper, Gregory S; Crocombe, Richard A; Wang, Jih Tzong; Williams, Ffrancon

    2005-08-01

    High-resolution ESR spectra of the ground-state negative ions of hexafluorocyclopropane (c-C3F6*-), octafluorocyclobutane (c-C4F8*-), and decafluorocyclopentane (c-C5F10*-) are reported and their isotropic 19F hyperfine coupling constants (hfcc) of 198.6 +/- 0.4 G, 147.6 +/- 0.4 G, and 117.9 +/- 0.4 G, respectively, are in inverse ratio to the total number of fluorine atoms per anion. Together with the small value of 5.2 +/- 0.4 G determined for the isotropic 13C hfcc of c-C4F8*-, these results indicate that in each case the singly occupied molecular orbital (SOMO) is delocalized over the equivalent fluorines and possesses a nodal plane through the carbon atoms of a time-averaged D(nh) structure. A series of quantum chemical computations were carried out to further characterize these anions and their neutral counterparts. Both the B3LYP density functional and second-order Møller-Plesset perturbation theory (MP2) indicate that c-C3F6*- adopts a D(3h) geometry and a (2)A2'' ground electronic state, that c-C4F8*- adopts a D(4h) geometry and a (2)A2u ground electronic state, and that c-C5F10*- adopts a C(s) structure and a (2)A' electronic state. Moreover, the 19F hyperfine coupling constants computed with the MP2 method and a high quality triple-zeta basis set are within 1% of the experimental values. Also, the values computed for the 13C hfcc of c-C4F8*- are consistent with the experimental value of 5.2 G. Therefore, in keeping with the ESR results, these negative ions derived from first-row elements can be characterized as pi* species. In addition, the hypervalency of these perfluorocycloalkane radical anions has been clarified.

  4. Tungsten monocarbide, WC: pure rotational spectrum and 13C hyperfine interaction.

    PubMed

    Wang, Fang; Steimle, Timothy C

    2012-01-28

    The J = 1→2 pure rotational transitions in the X(3)Δ(1)(ν = 0) state of (186)W(12)C and (184)W(12)C were recorded using a pump/probe microwave optical double resonance (PPMODR) technique and analyzed to give fine structure parameters. The field-free [17.6]2←X(3)Δ(1) (1, 0) bands of the W(13)C isotopologues were recorded using laser induced fluorescence and analyzed to produce the (13)C(I = 1/2) magnetic hyperfine parameter. Bonding in the [17.6]2(ν = 1) and X(3)Δ(1)(ν = 0) states is discussed and a comparison of the experimentally determined properties of the X(3)Δ(1)(ν = 0) state with those predicted as a prelude to the electron electric dipole moment (eEDM) measurements [J. Lee, E. R. Meyer, R. Paudel, J. L. Bohn, and A. E. Leanhardt, J. Mod. Opt. 56, 2005 (2009)] is given.

  5. Tungsten monocarbide, WC: Pure rotational spectrum and 13C hyperfine interaction

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Steimle, Timothy C.

    2012-01-01

    The J = 1 → 2 pure rotational transitions in the X3Δ1(v = 0) state of 186W12C and 184W12C were recorded using a pump/probe microwave optical double resonance (PPMODR) technique and analyzed to give fine structure parameters. The field-free [17.6]2← X3Δ1 (1, 0) bands of the W13C isotopologues were recorded using laser induced fluorescence and analyzed to produce the 13C(I = 1/2) magnetic hyperfine parameter. Bonding in the [17.6]2(v = 1) and X3Δ1(v = 0) states is discussed and a comparison of the experimentally determined properties of the X3Δ1(v = 0) state with those predicted as a prelude to the electron electric dipole moment (eEDM) measurements [J. Lee, E. R. Meyer, R. Paudel, J. L. Bohn, and A. E. Leanhardt, J. Mod. Opt. 56, 2005 (2009), 10.1080/09500340903349930] is given.

  6. {sup 13}C-{sup 1}H and {sup 13}C-{sup 13}C spin couplings in [2`-{sup 13}C]2`-deoxyribonucleosides: Correlations with molecular structure

    SciTech Connect

    Bandyopadhyay, T.; Stripe, W.A.; Carmichael, I.; Serianni, A.S.; Wu, J.

    1997-02-19

    2`-Deoxyribonucleosides (2`-deoxyadenosine (1), 2`-depoxycytidine (2), thymidine (3)) singly enriched with {sup 13}C at C2` have been prepared and used to obtain one-, two-, and three-bond {sup 13}C-{sup 1}H and {sup 13}C-{sup 13}C spin-coupling constants involving C2`. Spin couplings in 1-3 involving C1` and C2`are also compared to corresponding values in ribonucleosides in order to assess the effects of nucleoside structure and conformation on J values within the furanose ring. {sup 1}J{sub C2`,H2`R} and {sup 1}J{sub C2`,H2`S} in 1-3 and {sup 1}J{sub C2`,H2`} in ribonucleosides depend on C-H bond orientation: {sup 1}J{sub C1`,H1`} in 1-3 and in ribonucleosides exhibits a similar dependence. The latter couplings appear to be essentially unaffected by N-glycoside torsion. {sup 1}J{sub CC} values depend on the number and distribution of electronegative substituents on the C-C fragment. A modified projection curve is proposed to aid in the interpretation of {sup 2}J{sub C2`,H1`} values; the presence of N substitution at C1` caused a shift to more negative couplings relative to the O-substituted analog. In contrast, {sup 2}J{sub C1`,H2`} is essentially unaffected by the same change in the electronegative substituent at C1`. {sup 2}J{sub CC} values within the furanose ring are determined buy two coupling pathways; in one case (i.e., {sup 2}J{sub C1`,C3`}), the observed coupling is shown to be the algebraic sum of the two couplings arising from each pathway. 41 refs., 4 figs., 2 tabs.

  7. NMR structure analysis of uniformly 13C-labeled carbohydrates.

    PubMed

    Fontana, Carolina; Kovacs, Helena; Widmalm, Göran

    2014-06-01

    In this study, a set of nuclear magnetic resonance experiments, some of them commonly used in the study of (13)C-labeled proteins and/or nucleic acids, is applied for the structure determination of uniformly (13)C-enriched carbohydrates. Two model substances were employed: one compound of low molecular weight [(UL-(13)C)-sucrose, 342 Da] and one compound of medium molecular weight ((13)C-enriched O-antigenic polysaccharide isolated from Escherichia coli O142, ~10 kDa). The first step in this approach involves the assignment of the carbon resonances in each monosaccharide spin system using the anomeric carbon signal as the starting point. The (13)C resonances are traced using (13)C-(13)C correlations from homonuclear experiments, such as (H)CC-CT-COSY, (H)CC-NOESY, CC-CT-TOCSY and/or virtually decoupled (H)CC-TOCSY. Based on the assignment of the (13)C resonances, the (1)H chemical shifts are derived in a straightforward manner using one-bond (1)H-(13)C correlations from heteronuclear experiments (HC-CT-HSQC). In order to avoid the (1) J CC splitting of the (13)C resonances and to improve the resolution, either constant-time (CT) in the indirect dimension or virtual decoupling in the direct dimension were used. The monosaccharide sequence and linkage positions in oligosaccharides were determined using either (13)C or (1)H detected experiments, namely CC-CT-COSY, band-selective (H)CC-TOCSY, HC-CT-HSQC-NOESY or long-range HC-CT-HSQC. However, due to the short T2 relaxation time associated with larger polysaccharides, the sequential information in the O-antigen polysaccharide from E. coli O142 could only be elucidated using the (1)H-detected experiments. Exchanging protons of hydroxyl groups and N-acetyl amides in the (13)C-enriched polysaccharide were assigned by using HC-H2BC spectra. The assignment of the N-acetyl groups with (15)N at natural abundance was completed by using HN-SOFAST-HMQC, HNCA, HNCO and (13)C-detected (H)CACO spectra.

  8. NMR structure analysis of uniformly 13C-labeled carbohydrates.

    PubMed

    Fontana, Carolina; Kovacs, Helena; Widmalm, Göran

    2014-06-01

    In this study, a set of nuclear magnetic resonance experiments, some of them commonly used in the study of (13)C-labeled proteins and/or nucleic acids, is applied for the structure determination of uniformly (13)C-enriched carbohydrates. Two model substances were employed: one compound of low molecular weight [(UL-(13)C)-sucrose, 342 Da] and one compound of medium molecular weight ((13)C-enriched O-antigenic polysaccharide isolated from Escherichia coli O142, ~10 kDa). The first step in this approach involves the assignment of the carbon resonances in each monosaccharide spin system using the anomeric carbon signal as the starting point. The (13)C resonances are traced using (13)C-(13)C correlations from homonuclear experiments, such as (H)CC-CT-COSY, (H)CC-NOESY, CC-CT-TOCSY and/or virtually decoupled (H)CC-TOCSY. Based on the assignment of the (13)C resonances, the (1)H chemical shifts are derived in a straightforward manner using one-bond (1)H-(13)C correlations from heteronuclear experiments (HC-CT-HSQC). In order to avoid the (1) J CC splitting of the (13)C resonances and to improve the resolution, either constant-time (CT) in the indirect dimension or virtual decoupling in the direct dimension were used. The monosaccharide sequence and linkage positions in oligosaccharides were determined using either (13)C or (1)H detected experiments, namely CC-CT-COSY, band-selective (H)CC-TOCSY, HC-CT-HSQC-NOESY or long-range HC-CT-HSQC. However, due to the short T2 relaxation time associated with larger polysaccharides, the sequential information in the O-antigen polysaccharide from E. coli O142 could only be elucidated using the (1)H-detected experiments. Exchanging protons of hydroxyl groups and N-acetyl amides in the (13)C-enriched polysaccharide were assigned by using HC-H2BC spectra. The assignment of the N-acetyl groups with (15)N at natural abundance was completed by using HN-SOFAST-HMQC, HNCA, HNCO and (13)C-detected (H)CACO spectra. PMID:24771296

  9. Structure of B sub 13 C sub 2

    SciTech Connect

    Bylander, D.M.; Kleinman, L. )

    1991-01-15

    By comparing calculated lattice constants with x-ray data as well as by comparison of calculated free energies, we find that the correct structure of B{sub 13}C{sub 2} is B{sub 12}(CBC) rather than B{sub 11}C(BBC), as had been suggested. We also show that B{sub 12}C{sub 3} is stable against 13B{sub 12}C{sub 3}{r arrow}12B{sub 13}C{sub 2}+15C as is B{sub 13}C{sub 2} against 3B{sub 13}C{sub 2}{r arrow}2B{sub 12}C{sub 3}+15B.

  10. Analysis of hyperfine structure in photoassociation spectra

    NASA Astrophysics Data System (ADS)

    Bergeman, T.

    2008-05-01

    The low Doppler width in photoassociation spectra from cold atoms makes hyperfine structure clearly visible, especially with heavier alkali atoms. Recently the focus has been on photoassociation to weakly bound dimers [1,2]. However there are also useful data on somewhat more deeply bound levels [2] for which a different coupling scheme is appropriate. Following [3], we use a F = J + I representation, and develop a transformation between this and the usual case e representation which applies at asymptotically large internuclear distance. We hope to model and assign hyperfine structure in φ = 1 states, using appropriate ground and excited state wavefunctions. To obtain eigenvalues from very large DVR matrices, we use a ``stepwise diagonalization'' procedure, which appears to be more efficient than standard sparse matrix methods. [1] E. Tiesinga et al. PRA 71, 052703 (2005); K. M. Jones et al, RMP 78, 483 (2006). [2] Data on Rb2 from J. Qi, D. Wang, Y. Huang, H. Pechkis, E. Eyler, P. Gould, W. C. Stwalley, C. C. Tsai and D.J. Heinzen; Data on RbCs from A. J. Kerman, J. M. Sage, S. Sainis and D. DeMille. [3] B. Gao, PRA 54, 2022 (1996).

  11. Quantum Theory of Hyperfine Structure Transitions in Diatomic Molecules.

    ERIC Educational Resources Information Center

    Klempt, E.; And Others

    1979-01-01

    Described is an advanced undergraduate laboratory experiment in which radio-frequency transitions between molecular hyperfine structure states may be observed. Aspects of the quantum theory applied to the analysis of this physical system, are discussed. (Authors/BT)

  12. Topological Constraints on Chain-Folding Structure of Semicrystalline Polymer as Studied by 13C-13C Double Quantum NMR

    NASA Astrophysics Data System (ADS)

    Hong, Youlee; Miyoshi, Toshikazu

    Chain-folding process is a prominent feature of long polymer chains during crystallization. Over the last half century, much effort has been paid to reveal the chain trajectory. Even though various chain-folding models as well as theories of crystallization at molecule levels have been proposed, they could be not reconciled due to the limited experimental evidences. Recent development of double quantum NMR with selective isotope labeling identified the chain-trajectory of 13C labeled isotactic poly(1-butene). The systematic experiments covered a wide range of parameters, i.e. kinetics, concentration, and molecular weight (Mw) . It was demonstrated that i) adjacent re-entry site was invariant as a function of crystallization temperature (Tc) , concentration, andMw, ii) long-range order of adjacent re-entry sequence is independence of kinetics at a given concentration while it decreased with increasing the polymer concentration at a given Tc due to the increased interruption between the chains, and iii) high Mw chains led to the multilayer folded structures in single crystals, but the melt state induced the identical short adjacent sequences of long and short polymer over a wide range of Tc due to the entanglements. The behaviors indicated that the topological restriction plays significant roles in the chain-folding process rather than the kinetics. The proposed framework to control the chain-folding structure presents a new perspective into the chain organization by either the intra- or inter-chain interaction. National Science Foundation Grants DMR-1105829 and 1408855.

  13. Spin-torsion effects in the hyperfine structure of methanol

    SciTech Connect

    Coudert, L. H. Gutlé, C.; Huet, T. R.; Grabow, J.-U.; Levshakov, S. A.

    2015-07-28

    The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.

  14. Coal structure at reactive sites by sup 1 H- sup 13 C- sup 19 F double cross polarization (DCP)/MAS sup 13 C NMR spectroscopy

    SciTech Connect

    Hagaman, E.W.; Woody, M.C. )

    1989-01-01

    The solid state NMR technique, {sup 1}H-{sup 13}C-{sup 31}P double cross polarization (DCP)/MAS {sup 13}C-NMR spectroscopy, uses the direct dipolar interaction between {sup 13}C-{sup 31}P spin pairs in organophosphorus substances to identify the subset of carbons within a spherical volume element of 0.4 nm radius centered on the {sup 31}P atom. In combination with chemical manipulation of coals designed to introduce phosphorus containing functionality into the organic matrix, the NMR experiment becomes a method to examine selectively the carbon bonding network at the reactive sites in the coal. This approach generates a statistical structure description of the coal at the reaction centers in contrast to bulk carbon characterization using conventional {sup 1}H-{sup 13}C CP/MAS {sup 13}C NMR spectroscopy. 3 refs.

  15. Detection of the quadrupole hyperfine structure in HCNH(+)

    NASA Technical Reports Server (NTRS)

    Ziurys, L. M.; Apponi, A. J.; Yoder, J. T.

    1992-01-01

    We report the first measurement of the electric quadrupole hyperfine structure of HCNH(+). The J = 1-0 transition of this interstellar molecular ion was observed toward the cold, dark cloud TMC-1, using the NRAO 12 m telescope at 74 GHz. The three hyperfine components of this transition were clearly detected and resolved, enabling the first experimental determination of the quadrupole coupling constant eqQ of HCNH(+). The value of this constant is calculated to be eqQ = -0.49 +/- 0.07 MHz. The column density of HCNH(+) toward TMC-1 was found to be N(tot) about 2.8 x 10 exp 13/sq cm, corresponding to a fractional abundance relative to H2 of f about 3 x 10 exp -9. This abundance is at least one order of magnitude higher than the predictions of ion-molecule chemistry. Detection of the hyperfine structure clearly establishes the presence of HCNH(+) in interstellar space.

  16. The NH2D hyperfine structure revealed by astrophysical observations

    NASA Astrophysics Data System (ADS)

    Daniel, F.; Coudert, L. H.; Punanova, A.; Harju, J.; Faure, A.; Roueff, E.; Sipilä, O.; Caselli, P.; Güsten, R.; Pon, A.; Pineda, J. E.

    2016-02-01

    Context. The 111-101 lines of ortho- and para-NH2D (o/p-NH2D) at 86 and 110 GHz, respectively, are commonly observed to provide constraints on the deuterium fractionation in the interstellar medium. In cold regions, the hyperfine structure that is due to the nitrogen (14N) nucleus is resolved. To date, this splitting is the only one that is taken into account in the NH2D column density estimates. Aims: We investigate how including the hyperfine splitting caused by the deuterium (D) nucleus affects the analysis of the rotational lines of NH2D. Methods: We present 30 m IRAM observations of the above mentioned lines and APEX o/p-NH2D observations of the 101-000 lines at 333 GHz. The hyperfine patterns of the observed lines were calculated taking into account the splitting induced by the D nucleus. The analysis then relies on line lists that either neglect or include the splitting induced by the D nucleus. Results: The hyperfine spectra are first analyzed with a line list that only includes the hyperfine splitting that is due to the 14N nucleus. We find inconsistencies between the line widths of the 101-000 and 111-101 lines, the latter being larger by a factor of ~1.6 ± 0.3. Such a large difference is unexpected because the two sets of lines probably originate from the same region. We next employed a newly computed line list for the o/p-NH2D transitions where the hyperfine structure induced by both nitrogen and deuterium nuclei was included. With this new line list, the analysis of the previous spectra leads to compatible line widths. Conclusions: Neglecting the hyperfine structure caused by D leads to overestimating the line widths of the o/p-NH2D lines at 3 mm. The error for a cold molecular core is about 50%. This error propagates directly to the column density estimate. We therefore recommend to take the hyperfine splittings caused by both the 14N and D nuclei into account in any analysis that relies on these lines. Based on observations carried out with the IRAM

  17. Rotational spectrum and carbon-13 hyperfine structure of the C3H, C5H, C6H, and C7H radicals.

    PubMed

    McCarthy, M C; Thaddeus, P

    2005-05-01

    By means of Fourier transform microwave spectroscopy of a supersonic molecular beam, we have detected the singly substituted carbon-13 isotopic species of C(5)H, C(6)H, and C(7)H. Hyperfine structure in the rotational transitions of the lowest-energy fine structure component ((2)Pi(12) for C(5)H and C(7)H, and (2)Pi(32) for C(6)H) of each species was measured between 6 and 22 GHz, and precise rotational, centrifugal distortion, Lambda-doubling, and (13)C hyperfine coupling constants were determined. In addition, resolved hyperfine structure in the lowest rotational transition (J = 32-->12) of the three (13)C isotopic species of C(3)H was measured by the same technique. By combining the centimeter-wave measurements here with previous millimeter-wave data, a complete set of (13)C hyperfine coupling constants were derived to high precision for each isotopic species. Experimental structures (r(0)) have been determined for C(5)H and the two longer carbon-chain radicals, and these are found to be in good agreement with the predictions of high-level coupled-cluster calculations. C(3)H, C(5)H, and C(7)H exhibit a clear alternation in the magnitude and sign of the (13)C hyperfine coupling constants along the carbon-chain backbone. Because the electron spin density is nominally zero at the central carbon atom of C(3)H, C(5)H, and C(7)H, and at alternating sets of carbon atoms of C(5)H and C(7)H, owing to spin polarization, almost all of the (13)C coupling constants at these atoms are small in magnitude and negative in sign. Spin-polarization effects are known to be important for the Fermi-contact (b(F)) term, but prior to the work here they have generally been neglected for the hyperfine terms a, c, and d.

  18. Theoretical study of hyperfine structure constants of Ga isotopes

    NASA Astrophysics Data System (ADS)

    Wang, Q. M.; Li, J. G.; Fritzsche, S.; Godefroid, M.; Chang, Z. W.; Dong, C. Z.

    2012-11-01

    The hyperfine structure constants for the ground 4s24p 2P°3/2 and lowest excited states 4s25s 2S1/2 of 71Ga are calculated using the GRASP2K package based on the multi-configuration Dirac-Hartree-Fock method. Furthermore, the magnetic dipole (μ) and the electric quadrupole (Q) moments of the Ga isotopes from 67Ga to 81Ga are derived.

  19. Deuterium hyperfine structure in interstellar C3HD.

    PubMed

    Bell, M B; Watson, J K; Feldman, P A; Matthews, H E; Madden, S C; Irvine, W M

    1987-05-22

    The deuterium nuclear quadrupole hyperfine structure of the transition 1(10)-1(01) of the ring molecule cyclopropenylidene-d1 (C3HD) has been observed in emission from interstellar molecular clouds. The narrowest linewidths (approximately 7 kHz) so far observed are in the cloud L1498. The derived D coupling constants Xzz = 186.9(1.4) kHz, eta=0.063(18) agree well with correlations based on other molecules.

  20. First Optical Hyperfine Structure Measurement in an Atomic Anion

    SciTech Connect

    Fischer, A.; Canali, C.; Warring, U.; Kellerbauer, A.; Fritzsche, S.

    2010-02-19

    We have investigated the hyperfine structure of the transition between the 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2}{sup e} ground state and the 5d{sup 6}6s{sup 2}6p {sup 6}D{sub J}{sup o} excited state in the negative osmium ion by high-resolution collinear laser spectroscopy. This transition is unique because it is the only known electric-dipole transition in atomic anions and might be amenable to laser cooling. From the observed hyperfine structure in {sup 187}Os{sup -} and {sup 189}Os{sup -} the yet unknown total angular momentum of the bound excited state was found to be J=9/2. The hyperfine structure constants of the {sup 4}F{sub 9/2}{sup e} ground state and the {sup 6}D{sub 9/2}{sup o} excited state were determined experimentally and compared to multiconfiguration Dirac-Fock calculations. Using the knowledge of the ground and excited state angular momenta, the full energy level diagram of {sup 192}Os{sup -} in an external magnetic field was calculated, revealing possible laser cooling transitions.

  1. Hyperfine structure and isotope shift study in singly ionized lead

    NASA Astrophysics Data System (ADS)

    Wąsowicz, T. J.; Drozdowski, R.; Kwela, J.

    2005-12-01

    Hyperfine structure and isotope shifts in five optical transitions: 424.5 nm (6s^25f ^2textrm{F}_{7/2} 6s^26d^2 textrm{D}_{5/2}), 537.2 nm (6s^25f ^2textrm{F}_{7/2} 6s6p^2 ^4textrm{P}_{5/2}), 554.5 nm (6s^27d ^2textrm{D}_{5/2} 6s^27p ^2textrm{P}_{3/2}), 560.9 nm (6s^27p^2 textrm{P}_{3/2} 6s^27s ^2textrm{S}_{1/2}) and 666.0 nm (6s^27p ^2textrm{P}_{1/2} 6s^27s ^2textrm{S}_{1/2}) of Pb II have been measured. As a light source the discharge tube was used. The hyperfine structure measurements were performed using metallic isotope 207Pb. For isotope shifts measurements natural lead was used. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with a CCD camera used as a detector. In the analysis of the spectra a computer simulation technique was used. The hyperfine structure observations yielded the splitting constants A for seven levels of Pb II. The isotope shift studies enabled to separate the mass and the field shifts and to determine values of changes of the mean square nuclear charge radii.

  2. Chain-Folding Structures of a Semi-crystalline Polymer in Bulk and Single Crystals Elucidated by 13C-13C Double Quantum NMR

    NASA Astrophysics Data System (ADS)

    Hong, You-Lee; Miyoshi, Toshikazu

    2014-03-01

    Semi-crystalline polymers are crystallized as folded chains in thin lamellae of ca. 5-20 nm from random coils in the melt and solution states. However, understanding of detailed chain-folding structure and crystallization mechanism are still challenging issue due to various experimental limitations. We recently developed a new strategy using 13C-13C double-quantum (DQ) NMR with selectively 13C isotope labeled isotactic poly(1-butene) form I to investigate chain-trajectory in solution and melt grown crystals at various Tcs. This new method can determine the re-entrance sites, the successive folding number (n) , and the fractions (F) of chain-folding in a wide Tc range. In melt grown crystals at Tc = 95 °C, a comparison of experimental and simulated DQ efficiency determined that the polymer chains alternatively change chain-folding directions and the stems tightly pack via intramolecular interactions, and the fraction (F) of adjacent re-entry structure ranges from 70% at n = 4 to 100% at mixed structures of n = 1 and 2. Furthermore, DQ efficiency is independent of Tc in bulk crystals. This means chain-folding do not change in a wide Tcs. DMR-1105829.

  3. Analysis of defect structure in silicon. Characterization of samples from UCP ingot 5848-13C

    NASA Technical Reports Server (NTRS)

    Natesh, R.; Guyer, T.; Stringfellow, G. B.

    1982-01-01

    Statistically significant quantitative structural imperfection measurements were made on samples from ubiquitous crystalline process (UCP) Ingot 5848 - 13 C. Important trends were noticed between the measured data, cell efficiency, and diffusion length. Grain boundary substructure appears to have an important effect on the conversion efficiency of solar cells from Semix material. Quantitative microscopy measurements give statistically significant information compared to other microanalytical techniques. A surface preparation technique to obtain proper contrast of structural defects suitable for QTM analysis was perfected.

  4. Synthesis of D-[U-{sup 13}C]Glucal, D-[U-{sup 13}C] Galactal, and L-[U-{sup 13}C]Fucose for NMR structure studies of oligosaccharides

    SciTech Connect

    Wu, R.; Unkefer, C.J.; Silks, L.A. III

    1996-12-31

    The role of carbohydrates is well recognized in a variety of important biological phenomena such as cell surface recognition. Recent advances in carbohydrate chemistry, including the development of solid phase synthesis methods, have helped to provide significant quantities of material by offering general protocols for synthesis of well-defined, pure material. However, the study of the solution structure of oligosaccharides by nuclear magnetic resonance techniques have been hampered by the lack of enriched {sup 13}C material. In an effort to help alleviate this situation, we have been interested in the construction of the title compounds from a single economical carbon source, D-[U-{sup 13}C]glucose. Details of the syntheses will be provided.

  5. Microsolvation of methylmercury: structures, energies, bonding and NMR constants ((199)Hg, (13)C and (17)O).

    PubMed

    Flórez, Edison; Maldonado, Alejandro F; Aucar, Gustavo A; David, Jorge; Restrepo, Albeiro

    2016-01-21

    Hartree-Fock (HF) and second order perturbation theory (MP2) calculations within the scalar and full relativistic frames were carried out in order to determine the equilibrium geometries and interaction energies between cationic methylmercury (CH3Hg(+)) and up to three water molecules. A total of nine structures were obtained. Bonding properties were analyzed using the Quantum Theory of Atoms In Molecules (QTAIM). The analyses of the topology of electron densities reveal that all structures exhibit a partially covalent HgO interaction between methylmercury and one water molecule. Consideration of additional water molecules suggests that they solvate the (CH3HgOH2)(+) unit. Nuclear magnetic shielding constants σ((199)Hg), σ((13)C) and σ((17)O), as well as indirect spin-spin coupling constants J((199)Hg-(13)C), J((199)Hg-(17)O) and J((13)C-(17)O), were calculated for each one of the geometries. Thermodynamic stability and the values of NMR constants correlate with the ability of the system to directly coordinate oxygen atoms of water molecules to the mercury atom in methylmercury and with the formation of hydrogen bonds among solvating water molecules. Relativistic effects account for 11% on σ((13)C) and 14% on σ((17)O), which is due to the presence of Hg (heavy atom on light atom, HALA effect), while the relativistic effects on σ((199)Hg) are close to 50% (heavy atom on heavy atom itself, HAHA effect). J-coupling constants are highly influenced by relativity when mercury is involved as in J((199)Hg-(13)C) and J((199)Hg-(17)O). On the other hand, our results show that the values of NMR constants for carbon and oxygen, atoms which are connected through mercury (C-HgO), are highly correlated and are greatly influenced by the presence of water molecules. Water molecules introduce additional electronic effects to the relativistic effects due to the mercury atom. PMID:26670708

  6. Microsolvation of methylmercury: structures, energies, bonding and NMR constants ((199)Hg, (13)C and (17)O).

    PubMed

    Flórez, Edison; Maldonado, Alejandro F; Aucar, Gustavo A; David, Jorge; Restrepo, Albeiro

    2016-01-21

    Hartree-Fock (HF) and second order perturbation theory (MP2) calculations within the scalar and full relativistic frames were carried out in order to determine the equilibrium geometries and interaction energies between cationic methylmercury (CH3Hg(+)) and up to three water molecules. A total of nine structures were obtained. Bonding properties were analyzed using the Quantum Theory of Atoms In Molecules (QTAIM). The analyses of the topology of electron densities reveal that all structures exhibit a partially covalent HgO interaction between methylmercury and one water molecule. Consideration of additional water molecules suggests that they solvate the (CH3HgOH2)(+) unit. Nuclear magnetic shielding constants σ((199)Hg), σ((13)C) and σ((17)O), as well as indirect spin-spin coupling constants J((199)Hg-(13)C), J((199)Hg-(17)O) and J((13)C-(17)O), were calculated for each one of the geometries. Thermodynamic stability and the values of NMR constants correlate with the ability of the system to directly coordinate oxygen atoms of water molecules to the mercury atom in methylmercury and with the formation of hydrogen bonds among solvating water molecules. Relativistic effects account for 11% on σ((13)C) and 14% on σ((17)O), which is due to the presence of Hg (heavy atom on light atom, HALA effect), while the relativistic effects on σ((199)Hg) are close to 50% (heavy atom on heavy atom itself, HAHA effect). J-coupling constants are highly influenced by relativity when mercury is involved as in J((199)Hg-(13)C) and J((199)Hg-(17)O). On the other hand, our results show that the values of NMR constants for carbon and oxygen, atoms which are connected through mercury (C-HgO), are highly correlated and are greatly influenced by the presence of water molecules. Water molecules introduce additional electronic effects to the relativistic effects due to the mercury atom.

  7. Double cross polarization /sup 13/C-NMR experiment in solid fossil fuel structure analysis

    SciTech Connect

    Hagaman, E.W.; Woody, M.C.

    1988-01-01

    The Double Cross Polarization /sup 13/C-MAS/NMR experiment has been used to derive a new operational classification of solid fossil fuels based on chemical reactivity. The method requires labeling reactive sites in the organic matrix with a magnetically active isotope not present in the precursor material, and using the local, isolated dipole-dipole interaction between this nucleus and nearby /sup 13/C nuclei to detect via cross polarization the carbon centers in the vicinity of the label. The technique is a marriage of chemistry and spectroscopy and the information content of the DCP spectra is defined by both partners. /sup 1/H-/sup 13/C-/sup 31/P DCP/MAS /sup 13/C-NMR spectroscopy has been used to statistically describe phenolic ortho-substitution patterns of coals via their aryl phosphinate or phosphate derivatives. In these applications of DCP NMR the new, detailed structure and/or reactivity information is realized by detection of carbon resonances one or more bonds removed from the reaction center, but in a volume element of intramolecular dimensions. To the extent that intermolecular contributions to the spectrum are detected, and not recognized as such, the structure/reactivity correlation is weakened. Direct substitution of phosphorus on the aromatic rings in the organic matrix of the coal is not readily accomplished. This environment potentially can be labeled with fluorine in a selective fashion using newly developed reagents. The possibility of determining the changes in average ring substitution patterns as a function of chemical treatment or coal diagenesis emerges. Recent developments in the field of DCP /sup 13/C NMR are presented.

  8. Measurement of isotope shifts and hyperfine structure in Zr II

    NASA Astrophysics Data System (ADS)

    Rosner, S. D.; Holt, R. A.

    2016-06-01

    We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the isotope shifts (IS) of 51 optical transitions in the wavelength range 420.6-461.4 nm and the hyperfine structures (hfs) of 11 even parity and 30 odd parity levels in Zr II. The IS and many of the hfs measurements are the first for these transitions and levels. These atomic data are very important for astrophysical studies of chemical abundances, allowing correction for saturation and the effects of blended lines. They also provide important constraints on stellar diffusion modeling and provide a benchmark for theoretical atomic structure calculations.

  9. Dynamic polarizabilities and hyperfine-structure constants for Sc2 +

    NASA Astrophysics Data System (ADS)

    Dutta, Narendra Nath; Roy, Sourav; Deshmukh, P. C.

    2015-11-01

    In this work, we calculate dynamic polarizabilities and hyperfine-structure A and B constants of a few low-lying states for Sc2 +. The sum-over-states technique is applied to calculate the polarizabilities of the 3 d 2D3 /2 ,3 d 2D5 /2 , and 4 s 2S1 /2 states. The most important and correlation sensitive part of the sum is calculated using a highly correlated relativistic coupled-cluster theory. The remaining part of the sum is calculated using a lower-order many-body perturbation theory and the Dirac-Fock theory. Present dynamic polarizabilities are important to investigate the Stark shifts in the 4 s 2S1 /2 - 3 d 2D5 /2 and 4 s 2S1 /2 - 3 d 2D3 /2 clock transitions of Sc2 +. Magic wavelengths for zero Stark shifts corresponding to these transitions are found in the vacuum-ultraviolet region. The coupled-cluster theory is used to estimate the hyperfine A and B constants with a very high accuracy.

  10. 13C solid-state NMR analysis of heterogeneous structure of beeswax in native state

    NASA Astrophysics Data System (ADS)

    Kameda, Tsunenori

    2005-12-01

    I investigated the molecular structure of natural wax from Japanese bees (Apis cerana japonica) in its native state (neither purified nor recrystallized) by 13C and 1H solid-state NMR. Two strong 13C peaks at 32.9 and 34.0 ppm were attributed to signals from internal-chain methylene carbons [int-(CH2)] in two types of crystal form. The peak at 32.9 ppm was assigned to an orthorhombic crystal form, and that at 34.0 ppm was assigned to a triclinic or monoclinic form. In both crystalline regions, bi-exponential decay of 13C spin-lattice relaxation [T1(C)] for the crystalline peaks due to chain diffusion was observed. 1H spin-lattice relaxation [T1(H)] values for protons of the CH3 group and for int-(CH2) in the crystalline and amorphous regions were identical; this was interpreted as being due to averaging of the T1(H) relaxation rates via spin diffusion. In contrast, although the T_{{1}_{\\rho}}(H) decay curves for protons of the CH3 group and for int-(CH2) in the amorphous and orthorhombic forms were almost identical, those of the triclinic or monoclinic forms were different. This unhomogeneous character of T_{{1}_{\\rho}}(H) was interpreted as resulting from differences in the molecular composition of each crystal form. Moreover, two components with long and short 1H spin-spin relaxation [T2(H)] values, arising from the mobile and rigid phases, respectively, were observed at above about -30 °C.

  11. Improved Carbohydrate Structure Generalization Scheme for (1)H and (13)C NMR Simulations.

    PubMed

    Kapaev, Roman R; Toukach, Philip V

    2015-07-21

    The improved Carbohydrate Structure Generalization Scheme has been developed for the simulation of (13)C and (1)H NMR spectra of oligo- and polysaccharides and their derivatives, including those containing noncarbohydrate constituents found in natural glycans. Besides adding the (1)H NMR calculations, we improved the accuracy and performance of prediction and optimized the mathematical model of the precision estimation. This new approach outperformed other methods of chemical shift simulation, including database-driven, neural net-based, and purely empirical methods and quantum-mechanical calculations at high theory levels. It can process structures with rarely occurring and noncarbohydrate constituents unsupported by the other methods. The algorithm is transparent to users and allows tracking used reference NMR data to original publications. It was implemented in the Glycan-Optimized Dual Empirical Spectrum Simulation (GODESS) web service, which is freely available at the platform of the Carbohydrate Structure Database (CSDB) project ( http://csdb.glycoscience.ru). PMID:26087011

  12. The Hyperfine Structure of Aluminum Monoxide, AlO

    NASA Astrophysics Data System (ADS)

    Breier, A.; Büchling, Thomas; Giesen, Thomas; Gauss, Jürgen

    2014-06-01

    Small metal-containing molecules were produced in a laser ablation supersonic jet apparatus. The products were investigated by means of millimeter/submillimeter wave spectroscopy and optical spectra were recorded with a high-resolution grating spectrometer (HR2000+, OceanOptics). This method has been applied to study AlO produced from laser ablation of solid aluminum seeded in helium-buffer gas enriched with 2% of nitrogenous oxide. The adiabatically expanding dilute gas mixture is probed by monochromatic radiation of frequencies up to 400 GHz (WR2.8x3,Virginia Diodes Inc.). The measurements reveal the hyperfine structure of a linear molecule in Hund's case bβ S due to the nuclear spin of aluminum. With the present measurements, new high accurate line positions for future astronomical observations and more accurate molecular parameters are available. The new data were compared to high level ab initio calculations performed by the group of J. Gauss.

  13. Hyperpolarized 13C NMR lifetimes in the liquid-state: relating structures and T1 relaxation times

    NASA Astrophysics Data System (ADS)

    Parish, Christopher; Niedbalski, Peter; Hashami, Zohreh; Fidelino, Leila; Kovacs, Zoltan; Lumata, Lloyd

    Among the various attempts to solve the insensitivity problem in nuclear magnetic resonance (NMR), the physics-based technique dissolution dynamic nuclear polarization (DNP) is probably the most successful method of hyperpolarization or amplifying NMR signals. Using this technique, liquid-state NMR signal enhancements of several thousand-fold are expected for low-gamma nuclei such as carbon-13. The lifetimes of these hyperpolarized 13C NMR signals are directly related to their 13C spin-lattice relaxation times T1. Depending upon the 13C isotopic location, the lifetimes of hyperpolarized 13C compounds can range from a few seconds to minutes. In this study, we have investigated the hyperpolarized 13C NMR lifetimes of several 13C compounds with various chemical structures from glucose, acetate, citric acid, naphthalene to tetramethylallene and their deuterated analogs at 9.4 T and 25 deg C. Our results show that the 13C T1s of these compounds can range from a few seconds to more than 60 s at this field. Correlations between the chemical structures and T1 relaxation times will be discussed and corresponding implications of these results on 13C DNP experiments will be revealed. US Dept of Defense Award No. W81XWH-14-1-0048 and Robert A. Welch Foundation Grant No. AT-1877.

  14. Study of Nuclear Structure of 13C and 20Ne by Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Lombardo, I.; Campajola, L.; Dell'Aquila, D.; La Commara, M.; Ordine, A.; Rosato, E.; Spadaccini, G.; Vigilante, M.

    2014-12-01

    We report some recent experimental results on the spectroscopy of 13C and 20Ne nuclei by means of low energy nuclear reactions carried out with high resolution electrostatic accelerators. In the case of 13C we investigated the possible existence of a-cluster states above the a emission threshold by means of low energy elastic resonant scattering α+9Be in direct kinematics. Excitation functions show the presence of various resonances that have been reproduced by R-matrix fit. We studied also the structure of 20Ne by means of the 19F(p,α0) reaction at sub-barrier energies. The spectroscopy of 20Ne excited states in the region Ex ≈ 13.5-14.0 MeV can be probed by analyzing experimental angular distributions and excitation functions. This reaction plays an important role also in the CNOF cycle and is an important ingredient to describe hydrogen-induced destruction of fluorine in massive stars. For this reason we investigated the trend of S-factor, that has been compared with results previously reported in the literature.

  15. Zeeman effects in the hyperfine structure of atomic iodine photodissociation laser emission.

    NASA Technical Reports Server (NTRS)

    Hwang, W. C.; Kasper, J. V. V.

    1972-01-01

    Observation of hyperfine structure in laser emission from CF3I and C2F5I photodissociation lasers. Constant magnetic fields affect the time behavior of the emission by changing the relative gains of the hyperfine transitions. Time-varying fields usually present in photodissociation lasers further complicate the emission.

  16. New experimental constraints on polarizability corrections to hydrogen hyperfine structure

    SciTech Connect

    Vahagn Nazaryan; Carl Carlson; Keith Griffioen

    2006-04-01

    We present a state-of-the-art evaluation of the polarizability corrections--the inelastic nucleon corrections--to the hydrogen ground-state hyperfine splitting using analytic fits to the most recent data. We find a value {Delta}{sub pol} = 1.3 {+-} 0.3 ppm. This is 1-2 ppm smaller than the value of {Delta}{sub pol} deduced using hyperfine splitting data and elastic nucleon corrections obtained from modern form factor fits.

  17. Hyperfine Structure in Rotational Spectra of Deuterated Molecules: the Hds and ND_3 Case Studies

    NASA Astrophysics Data System (ADS)

    Cazzoli, Gabriele; Puzzarini, Cristina

    2016-06-01

    The determination of hyperfine parameters (quadrupole-coupling, spin-spin coupling, and spin-rotation constants) is one of the aims of high-resolution rotational spectroscopy. These parameters are relevant not only from a spectroscopic point of view, but also from a physical and/or chemical viewpoint, as they might provide detailed information on the chemical bond, structure, etc. In addition, the hyperfine structure of rotational spectra is so characteristic that its analysis may help in assigning the spectra of unknown species. In astronomical observations, hyperfine structures of rotational spectra would allow us to gain information on column densities and kinematics, and the omission of taking them into account can lead to a misinterpretation of the line width of the molecular emission lines. Nevertheless, the experimental determination of hyperfine constants can be a challenge not only for actual problems in resolving hyperfine structures themselves, but also due to the lack of reliable estimates or the complexity of the hyperfine structure itself. It is thus important to be able to rely on good predictions for such parameters, which can nowadays be provided by quantum-chemical calculations. In fact, the fruitful interplay of experiment and theory will be demonstrated by means of two study cases: the hypefine structure of the rotational spectra of HDS and ND_3. From an experimental point of view, the Lamb-dip technique has been employed to improve the resolving power in themillimeter- and submillimeterwave frequency range by at least one order of magnitude, thus making it possible to perform sub-Doppler measurements as well as to resolve narrow hyperfine structures. Concerning theory, it will be demonstrated that high-level calculations can provide quantitative estimates for hyperfine parameters (quadrupole coupling constants, spin-rotation tensors, spin-spin couplings, etc.) and shown how theoretical predictions are often essential for a detailed analysis of

  18. Effect of nuclear hyperfine structure on microwave spectral pressure broadening

    NASA Astrophysics Data System (ADS)

    Green, Sheldon

    1988-06-01

    The spectral pressure broadening formalism of Ben-Reuven [Phys. Rev. 145, 7 (1966)] is applied to rotational transitions of a closed-shell linear molecule with nuclear quadrupole hyperfine structure (hfs) due to a nucleus of spin I. If, as expected, nuclear spin does not affect molecular collision dynamics, generalized pressure broadening cross sections can be expressed in terms of the spin-free collisional S matrices. For the three hfs components of the lowest j=0-1 rotational transition, the line shape is a simple sum of three noninterfering Lorentzians each of which has the same width and shift as would be expected in the absence of nuclear spin. For higher rotational transitions, however, the line shape is no longer so simple; in general, each hfs component is described by a different width and shift, and collisions transfer intensity among them. Numerical results for HCN broadened by He atoms are presented using both the accurate close coupling (CC) collision formalism and also the infinite order sudden (IOS) approximation. For the case that broadening is very large compared with the hfs splittings it is shown (numerically, within the IOS approximation) that the line shape is nearly (but not exactly, except for j=0-1 as noted above) a Lorentzian with the same width as would be expected in the absence of nuclear spin.

  19. ISOTROPIC INELASTIC COLLISIONS IN A MULTITERM ATOM WITH HYPERFINE STRUCTURE

    SciTech Connect

    Belluzzi, Luca; Landi Degl’Innocenti, Egidio; Bueno, Javier Trujillo

    2015-10-10

    A correct modeling of the scattering polarization profiles observed in some spectral lines of diagnostic interest, the sodium doublet being one of the most important examples, requires taking hyperfine structure (HFS) and quantum interference between different J-levels into account. An atomic model suitable for taking these physical ingredients into account is the so-called multiterm atom with HFS. In this work, we introduce and study the transfer and relaxation rates due to isotropic inelastic collisions with electrons, which enter the statistical equilibrium equations (SEE) for the atomic density matrix of this atomic model. Under the hypothesis that the electron–atom interaction is described by a dipolar operator, we provide useful relations between the rates describing the transfer and relaxation of quantum interference between different levels (whose numerical values are in most cases unknown) and the usual rates for the atomic level populations, for which experimental data and/or approximate theoretical expressions are generally available. For the particular case of a two-term atom with HFS, we present an analytical solution of the SEE for the spherical statistical tensors of the upper term, including both radiative and collisional processes, and we derive the expression of the emission coefficient in the four Stokes parameters. Finally, an illustrative application to the Na i D{sub 1} and D{sub 2} lines is presented.

  20. Relativistic Calculating the Spectral Lines Hyperfine Structure Parameters for Heavy Ions

    SciTech Connect

    Khetselius, O. Yu.

    2008-10-22

    The energies and constants of the hyperfine structure, derivatives of the one-electron characteristics on nuclear radius, nuclear electric quadrupole, magnetic dipole moments for some Li-like multicharged ions are calculated.

  1. Calculation of the hyperfine structure of the superheavy elements Z=119 and Z=120{sup +}

    SciTech Connect

    Dinh, T. H.; Dzuba, V. A.; Flambaum, V. V.

    2009-10-15

    The hyperfine-structure constants of the lowest s and p{sub 1/2} states of superheavy elements Z=119 and Z=120{sup +} are calculated using ab initio approach. Core polarization and dominating correlation effects are included to all orders. Breit and quantum electrodynamic effects are also considered. Similar calculations for Cs, Fr, Ba{sup +}, and Ra{sup +} are used to control the accuracy. The dependence of the hyperfine-structure constants on the nuclear radius is discussed.

  2. Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization.

    PubMed

    Germann, Matthias; Willitsch, Stefan

    2016-07-28

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization. PMID:27475368

  3. Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization.

    PubMed

    Germann, Matthias; Willitsch, Stefan

    2016-07-28

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization.

  4. Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization

    NASA Astrophysics Data System (ADS)

    Germann, Matthias; Willitsch, Stefan

    2016-07-01

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization.

  5. Unraveling the 13C NMR Chemical Shifts in Single-Walled Carbon Nanotubes: Dependence on Diameter and Electronic Structure

    SciTech Connect

    Engtrakul, C.; Irurzun, V. M.; Gjersing, E. L.; Holt, J. M.; Larsen, B. A.; Resasco, D. E.; Blackburn, J. L.

    2012-03-14

    The atomic specificity afforded by nuclear magnetic resonance (NMR) spectroscopy could enable detailed mechanistic information about single-walled carbon nanotube (SWCNT) functionalization as well as the noncovalent molecular interactions that dictate ground-state charge transfer and separation by electronic structure and diameter. However, to date, the polydispersity present in as-synthesized SWCNT populations has obscured the dependence of the SWCNT {sup 13}C chemical shift on intrinsic parameters such as diameter and electronic structure, meaning that no information is gleaned for specific SWCNTs with unique chiral indices. In this article, we utilize a combination of {sup 13}C labeling and density gradient ultracentrifugation (DGU) to produce an array of {sup 13}C-labeled SWCNT populations with varying diameter, electronic structure, and chiral angle. We find that the SWCNT isotropic {sup 13}C chemical shift decreases systematically with increasing diameter for semiconducting SWCNTs, in agreement with recent theoretical predictions that have heretofore gone unaddressed. Furthermore, we find that the {sup 13}C chemical shifts for small diameter metallic and semiconducting SWCNTs differ significantly, and that the full-width of the isotropic peak for metallic SWCNTs is much larger than that of semiconducting nanotubes, irrespective of diameter.

  6. On the observability of optically thin coronal hyperfine structure lines

    SciTech Connect

    Chatzikos, M.; Ferland, G. J.; Williams, R. J. R.; Fabian, A. C.

    2014-06-01

    We present CLOUDY calculations for the intensity of coronal hyperfine lines in various environments. We model indirect collisional and radiative transitions, and quantify the collisionally excited line emissivity in the density-temperature phase space. As an observational aid, we also express the emissivity in units of that in the 0.4-0.7 keV band. For most hyperfine lines, knowledge of the X-ray surface brightness and the plasma temperature is sufficient for rough estimates. We find that the radiation fields of both Perseus A and Virgo A can enhance the populations of highly ionized species within 1 kpc. They can also enhance line emissivity within the cluster core. This could have implications for the interpretation of spectra around bright active galactic nuclei. We find the intensity of the {sup 57}Fe XXIV λ3.068 mm line to be about two orders of magnitude fainter than previously thought, at ∼20 μK. Comparably bright lines may be found in the infrared. Finally, we find the intensity of hyperfine lines in the Extended Orion Nebula to be low, due to the shallow sightline. Observations of coronal hyperfine lines will likely be feasible with the next generation of radio and submillimeter telescopes.

  7. Galactic chemical evolution and solar s-process abundances: Dependence on the {sup 13}C-pocket structure

    SciTech Connect

    Bisterzo, S.; Travaglio, C.; Gallino, R.; Wiescher, M.; Käppeler, F. E-mail: sarabisterzo@gmail.com

    2014-05-20

    We study the s-process abundances (A ≳ 90) at the epoch of the solar system formation. Asymptotic giant branch yields are computed with an updated neutron capture network and updated initial solar abundances. We confirm our previous results obtained with a Galactic chemical evolution (GCE) model: (1) as suggested by the s-process spread observed in disk stars and in presolar meteoritic SiC grains, a weighted average of s-process strengths is needed to reproduce the solar s distribution of isotopes with A > 130; and (2) an additional contribution (of about 25%) is required in order to represent the solar s-process abundances of isotopes from A = 90 to 130. Furthermore, we investigate the effect of different internal structures of the {sup 13}C pocket, which may affect the efficiency of the {sup 13}C(α, n){sup 16}O reaction, the major neutron source of the s process. First, keeping the same {sup 13}C profile adopted so far, we modify by a factor of two the mass involved in the pocket; second, we assume a flat {sup 13}C profile in the pocket, and we test again the effects of the variation of the mass of the pocket. We find that GCE s predictions at the epoch of the solar system formation marginally depend on the size and shape of the {sup 13}C pocket once a different weighted range of {sup 13}C-pocket strengths is assumed. We obtain that, independently of the internal structure of the {sup 13}C pocket, the missing solar system s-process contribution in the range from A = 90 to 130 remains essentially the same.

  8. 1H and 13C NMR characterization and secondary structure of the K2 polysaccharide of Klebsiella pneumoniae strain 52145.

    PubMed

    Corsaro, Maria Michela; De Castro, Cristina; Naldi, Teresa; Parrilli, Michelangelo; Tomás, Juan M; Regué, Miguel

    2005-09-26

    The complete (1)H and (13)C NMR characterization of the tetrasaccharide repeating unit from the K2 polysaccharide of Klebsiella pneumoniae strain 52145 is reported. [chemical structure] In addition a model for its secondary structure was suggested on the basis of dynamic and molecular calculations.

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

    PubMed

    Luo, Wenbin; Yao, Xiaolan; Hong, Mei

    2005-05-01

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

  10. A computer-assisted structural analysis of regular polysaccharides on the basis of 13C-n.m.r. data.

    PubMed

    Lipkind, G M; Shashkov, A S; Knirel, Y A; Vinogradov, E V; Kochetkov, N K

    1988-04-01

    A computerised approach to the structural analysis of unbranched regular polysaccharides is described, which is based on an evaluation of the 13C-n.m.r. spectra for all possible primary structures within the additive scheme starting from the chemical shifts of the 13C resonances of the constituent monosaccharides and the average values of the glycosylation effects. The analysis reveals a structure (or structures), the evaluated spectrum of which resembles most closely that observed. The approach has been verified by using a series of bacterial polysaccharides of known structure and, in combination with methylation analysis data, for the determination of the presently unknown structures of the O-specific polysaccharides from Salmonella arizonae O59 and O63, and Proteus hauseri O19.

  11. Hyperfine structure of the 4f85d6s2 configuration of the Tb atom

    NASA Astrophysics Data System (ADS)

    Furmann, B.; Stefanska, D.; Krzykowski, A.

    2015-09-01

    In this work, A and B hyperfine structure constants of electronic levels belonging to the configuration 4f85d6s2 of the terbium atom are presented, obtained via investigation of the hyperfine structure of 42 spectral lines, performed with the method of laser-induced fluorescence (LIF) in a hollow cathode discharge. Results for 14 of the investigated levels belonging to the configuration 4f85d6s2 were obtained for the first time. Also results concerning the hyperfine structure of 29 levels, involved in the transitions as upper levels, are presented. For these levels, almost all the results were obtained for the first time. On the basis of the results obtained within this work and those known from the literature, parametrization of the hyperfine structure was performed. The determined values of one-electron parameters for configuration 4f85d6s2 were compared to the values known from literature, determined so far on the basis of a much lower number of electronic levels. Values of relativistic radial integrals of the hyperfine structure for electrons 4f and 5d of the configuration 4f85d6s2 were calculated with the use of the MCDF code. The comparison of radial integrals calculated semi-empirically with those determined with MCDF method yielded an estimate of the values of configuration interaction parameters in the case of both magnetic dipole and electric quadrupole interactions of the terbium atom.

  12. Structural Characterization of Humic Materials Using ^13C NMR Techniques: A Comparison of Solution- and Solid-State Methods

    NASA Astrophysics Data System (ADS)

    Clewett, Catherine; Alam, Todd; Osantowski, Eric; Pullin, Michael

    2011-10-01

    The analysis of the carbon type distribution and chemical structure of natural organic matter (NOM) by ^13C NMR spectroscopy is an important technique for understanding its origins and reactivity. While prior work has used solution-state NMR techniques, solid-state NMR has the potential to provide this information using less instrument time and sample manipulation, while providing an array of advanced filtering techniques. Analyses of four isolated humic materials with ^13C solid-state magic angle spinning (MAS) NMR techniques are described, including three commercially available samples and one fulvic acid sample isolated from the Rio Grande in New Mexico. This study demonstrates the utility of solid-state ^13C NMR for aquatic NOM structural characterization, comparing these results to the existing solution-state determinations. The solid-state ^13C MAS NMR results are used to determine % carbon distribution, estimates of elemental composition (%C, %H, %(O+N)), aromatic fraction (fa), nonprotonated aromatic fraction (faN), an estimate of aromatic cluster size, and ratio of sp^2 to sp^3 carbons. A Gaussian deconvolution method is introduced that allows for a detailed analysis of carbon type.

  13. Hyperfine structure of the hydroxyl free radical (OH) in electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Maeda, Kenji; Wall, Michael L.; Carr, Lincoln D.

    2015-05-01

    We investigate single-particle energy spectra of the hydroxyl free radical (OH) in the lowest electronic and rovibrational level under combined static electric and magnetic fields, as an example of heteronuclear polar diatomic molecules. In addition to the fine-structure interactions, the hyperfine interactions and centrifugal distortion effects are taken into account to yield the zero-field spectrum of the lowest 2Π3 / 2 manifold to an accuracy of less than 2kHz. We also examine level crossings and repulsions in the hyperfine structure induced by applied electric and magnetic fields. Compared to previous work, we found more than 10 percent reduction of the magnetic fields at level repulsions in the Zeeman spectrum subjected to a perpendicular electric field. In addition, we find new level repulsions, which we call Stark-induced hyperfine level repulsions, that require both an electric field and hyperfine structure. It is important to take into account hyperfine structure when we investigate physics of OH molecules at micro-Kelvin temperatures and below. This research was supported in part by AFOSR Grant No.FA9550-11-1-0224 and by the NSF under Grants PHY-1207881 and NSF PHY-1125915. We appreciate the Aspen Center for Physics, supported in part by the NSF Grant No.1066293, for hospitality.

  14. Variable-temperature 13C solid-state NMR study of the molecular structure of honeybee wax and silk.

    PubMed

    Kameda, Tsunenori; Tamada, Yasushi

    2009-01-01

    To elucidate the native-state crystal structure of beeswax from the Japanese bee, Apis cerana japonica, we determined the relationship between temperature and the 13C solid-state nuclear magnetic resonance (NMR) chemical shift of methylene carbon of beeswax, with comparison to n-alkanes and polyethylene in the orthorhombic, monoclinic, or triclinic crystal form. Variable-temperature 13C solid-state NMR observations of n-alkanes and polyethylene revealed that the chemical shifts of methylene carbon in the orthorhombic crystal form increased linearly with increasing temperature, that of the triclinic form decreased, and that of the monoclinic form was unaltered. These relations were compared with results of variable-temperature 13C solid-state NMR observation of beeswax. Results clarified that the two crystal forms comprising the beeswax in the native state are orthorhombic and monoclinic. The variable-temperature 13C solid-state NMR observations were also applied to interpret the differential scanning calorimetry (DSC) curve of beeswax. They were used to clarify the structural changes of beeswax for widely various temperatures. For beeswax secreted by the Japanese bee, the transition from the orthorhombic form to the rotator phase occurred at 36 degrees C, that is from the crystalline to the intermediate state at 45 degrees C. Moreover, the variable-temperature 13C solid-state NMR spectrum of honeybee silk in the native state was observed. Results demonstrated that the secondary structures of honeybee silk proteins in the native state comprised coexisting alpha-helix and beta-sheet conformations and that the amount of alpha-helices was greater. The alpha-helix content of honeybee silk was compared with that of hornet silk produced by Vespa larvae.

  15. Fine- and hyperfine-structure effects in molecular photoionization. II. Resonance-enhanced multiphoton ionization and hyperfine-selective generation of molecular cations

    NASA Astrophysics Data System (ADS)

    Germann, Matthias; Willitsch, Stefan

    2016-07-01

    Resonance-enhanced multiphoton ionization (REMPI) is a widely used technique for studying molecular photoionization and producing molecular cations for spectroscopy and dynamics studies. Here, we present a model for describing hyperfine-structure effects in the REMPI process and for predicting hyperfine populations in molecular ions produced by this method. This model is a generalization of our model for fine- and hyperfine-structure effects in one-photon ionization of molecules presented in Paper I [M. Germann and S. Willitsch, J. Chem. Phys. 145, 044314 (2016)]. This generalization is achieved by covering two main aspects: (1) treatment of the neutral bound-bound transition including the hyperfine structure that makes up the first step of the REMPI process and (2) modification of our ionization model to account for anisotropic populations resulting from this first excitation step. Our findings may be used for analyzing results from experiments with molecular ions produced by REMPI and may serve as a theoretical background for hyperfine-selective ionization experiments.

  16. DFT study of molecular structures and 13C NMR parameters of two fluorinated biphenyls and their η6-tricarbonylchromium complexes

    NASA Astrophysics Data System (ADS)

    Gryff-Keller, Adam; Szczeciński, Przemysław

    2015-07-01

    The molecular structures of 2,2‧-difluoro-6,6‧-dimethylbiphenyl, 4,5-difluoro-9,10-dihydrophenanthrene and of their η6-tricarbonylchromium complexes have been discussed in the light of the results of molecular energy calculations. Also the isotropic magnetic shielding constants and carbon-fluorine spin-spin coupling constants for these objects have been calculated and compared with the experimental values of 13C NMR chemical shifts and J constants. The calculational methods used were: DFT/BHandH/6-311++G(2d,p) and/or DFT/B3LYP/6-311++G(2d,p). It has been confirmed that experimental 13C NMR chemical shifts for η6-arene tricarbonylchromium complexes can be satisfactorily predicted using both methods, although the method exploiting BHandH functional is not able to reproduce the 13C NMR chemical shifts of Cr(CO)3 carbon atoms. On the other hand, this method provides the J(13C, 19F) values which are close to the experimental ones.

  17. Electronic Properties and 13C NMR Structural Study of Y3N@C88

    PubMed Central

    Fu, Wujun; Zhang, Jianyuan; Champion, Hunter; Fuhrer, Tim; Azuremendi, Hugo; Zuo, Tianming; Zhang, Jianfei; Harich, Kim; Dorn, Harry C.

    2011-01-01

    In this paper we report the synthesis, purification, 13C NMR and other characterization studies of Y3N@C88. The 13C NMR, UV-vis and chromatographic data suggest an Y3N@C88 having IPR allowed cage with D2(35)-C88 symmetry. In earlier density functional theory (DFT) computational and X-ray crystallographic studies, it was reported that lanthanide (A3N)6+ clusters are stabilized in D2(35)-C88 symmetry cages and have reduced HOMO-LUMO gaps relative to other trimetallic nitride endohedral metallofullerene cage systems, for example, A3N@C80. In this paper, we report that the non-lanthanide (Y3N)6+ cluster in the D2(35)-C88 cage exhibits a HOMO-LUMO gap consistent with other lanthanide A3N@C88 molecules based on electrochemical measurements and DFT computational study. These results suggests that the reduced HOMO-LUMO gap of A3N@C88 systems is a property dominated by the D2(35)-C88 carbon cage and not f-orbital lanthanide electronic metal cluster (A3N)6+ orbital participation. PMID:21506556

  18. Partial 13C isotopic enrichment of nucleoside monophosphates: useful reporters for NMR structural studies

    PubMed Central

    Kishore, Anita I.; Mayer, Michael R.; Prestegard, James H.

    2005-01-01

    Analysis of the 13C isotopic labeling patterns of nucleoside monophosphates (NMPs) extracted from Escherichia coli grown in a mixture of C-1 and C-2 glucose is presented. By comparing our results to previous observations on amino acids grown in similar media, we have been able to rationalize the labeling pattern based on the well-known biochemistry of nucleotide biosynthesis. Except for a few notable absences of label (C4 in purines and C3′ in ribose) and one highly enriched site (C1′ in ribose), most carbons are randomly enriched at a low level (an average of 13%). These sparsely labeled NMPs give less complex NMR spectra than their fully isotopically labeled analogs due to the elimination of most 13C–13C scalar couplings. The spectral simplicity is particularly advantageous when working in ordered systems, as illustrated with guanosine diphosphate (GDP) bound to ADP ribosylation factor 1 (ARF1) aligned in a liquid crystalline medium. In this system, the absence of scalar couplings and additional long-range dipolar couplings significantly enhances signal to noise and resolution. PMID:16254075

  19. Hyperfine-structure studies of Nb ii: Experimental and relativistic configuration-interaction results

    NASA Astrophysics Data System (ADS)

    Young, L.; Hasegawa, S.; Kurtz, C.; Datta, Debasis; Beck, Donald R.

    1995-05-01

    We report an experimental and theoretical study of the hyperfine structure (hfs) in various metastable states in 93Nb ii. Hyperfine structures of five levels in Nb ii have been measured using a combination of the laser-rf double resonance and laser-induced fluorescence methods in a collinear laser-ion-beam geometry. Theoretically, for J=2, a multireference calculation of energies and hfs based on a relativistic configuration-interaction methodology of the lowest ten levels in the (4d+5s)4 manifold is reported. The average energy error is 450 cm-1. Many of the hyperfine constants show large changes from the Dirac-Fock values and the magnetic dipole constant has a 4% accuracy for the one J=2 level measured. We have also identified all the core-valence and core-core effects that dominate the energy differences and hfs.

  20. A 13C NMR study of the structure of four cinnamic acids and their methyl esters

    NASA Astrophysics Data System (ADS)

    Silva, A. M. S.; Alkorta, I.; Elguero, J.; Silva, V. L. M.

    2001-09-01

    The 13C NMR spectra, both in DMSO solution and in the solid state of four cinnamic acids ( p-methoxy, p-hydroxy, p-methyl, p-chloro) and their corresponding methyl esters have been recorded. The two main results in the solid state are: (i) the only significant difference between acids and esters chemical shifts concerns the CO group which, on average, appears at 173 ppm in the acids and 168 ppm in the esters; (ii) the signals of the ortho and meta carbons both in the acids and the esters are splitted. The two 'anomalies' disappear in DMSO solution. These observations can be rationalized using simple GIAO/B3LYP/6-31G ∗ calculations.

  1. Chemical structural studies of natural lignin by dipolar dephasing solid-state 13C nuclear magnetic resonance

    USGS Publications Warehouse

    Hatcher, P.G.

    1987-01-01

    Two natural lignins, one from a gymnosperm wood the other from angiosperm wood, were examined by conventional solid-state and dipolar dephasing 13C nuclear magnetic resonance (NMR) techniques. The results obtained from both techniques show that the structure of natural lignins is consistent with models of softwood and hardwood lignin. The dipolar dephasing NMR data provide a measure of the degree of substitution on aromatic rings which is consistent with the models. ?? 1987.

  2. Observation of molecular hyperfine structure in the extreme ultraviolet: The HF C-X spectrum.

    PubMed

    Philippson, Jeffrey N; Shiell, Ralph C; Reinhold, Elmar; Ubachs, Wim

    2008-11-01

    Clearly resolved hyperfine structure has been observed in the extreme ultraviolet (XUV) spectra of the C (1)Pi, v=0-X (1)Sigma(+), v=0 transition of H(19)F obtained through 1 XUV+1 UV resonance enhanced multiphoton ionization spectroscopy. The hyperfine splitting within the R-branch lines shows significant perturbations, which we attribute to mixing with the rotational levels of the nearby v=29 level of the B (1)Sigma(+) ion-pair state. A deperturbation analysis quantitatively explains the apparent variation of the fluorine magnetic hyperfine parameter a(F), for which a value of 4034(83) MHz was obtained by averaging over the values derived from the R(0)-R(4) lines, after correcting for the effects of the perturbations.

  3. {sup 13}C-NMR study on the structure of isolated Sc{sub 2}@C{sub 84} metallofullerene

    SciTech Connect

    Yamamoto, Etsuji; Tansho, Masataka; Tomiyama, Tetsuo; Shinohara, Hisanori; Kawahara, Hironori; Kobayashi, Yuji

    1996-03-06

    Here we report the first {sup 13}C-NMR results on the metallofullerene, Sc{sub 2}@C{sub 84}, which determines an isomer cage structure for the metallofullerene. The Sc{sub 2}@C{sub 84} fullerene was separated and isolated from the various hollow fullerenes (C{sub 60}-C{sub 110}) and other scandium metallofullerenes by the multistage high-performance liquid chromatography (HPLC) method by using two complementary types of HPLC columns. The purity of Sc{sub 2}@C{sub 84} relative to other fullerenes was more than 99.9%. {sup 13}C-NMR measurements were made using a 600 MHz NMR (JEOL JNM-A600) at room temperature in CS{sub 2} solvent. 30 refs., 3 figs.

  4. Hyperfine structure constants for singly ionized manganese (Mn II) using Fourier transform spectroscopy

    NASA Astrophysics Data System (ADS)

    Townley-Smith, Keeley; Nave, Gillian; Pickering, Juliet C.; Blackwell-Whitehead, Richard J.

    2016-09-01

    We expand on the comprehensive study of hyperfine structure (HFS) in Mn II conducted by Holt et al. (1999) by verifying hyperfine magnetic dipole constants (A) for 20 levels previously measured by Holt et al. (1999) and deriving A constants for 47 previously unstudied levels. The HFS patterns were measured in archival spectra from Fourier transform (FT) spectrometers at Imperial College London and the National Institute of Standards and Technology. Analysis of the FT spectra was carried out in XGREMLIN. Our A constant for the ground level has a lower uncertainty by a factor of 6 than that of Blackwell-Whitehead et al.

  5. Investigations of hyperfine and isotope structures in optical spectra of crystals with rare-earth ions

    NASA Astrophysics Data System (ADS)

    Popova, M. N.

    2015-10-01

    This is a review of works on hyperfine and isotope structures in the spectra of rare-earth ions in crystals that have been performed at the Laboratory of Fourier Spectroscopy of the Institute for Spectroscopy, Russian Academy of Sciences. The applicability of these studies to the development of optical quantum memory is discussed.

  6. Pursuing structure in microcrystalline solids with independent molecules in the unit cell using 1H–13C correlation data

    PubMed Central

    Harper, James K.; Strohmeier, Mark; Grant, David M.

    2007-01-01

    The 1H–13C solid-state NMR heteronuclear correlation (HETCOR) experiment is demonstrated to provide shift assignments in certain powders that have two or more structurally independent molecules in the unit cell (i.e. multiple molecules per asymmetric unit). Although this class of solids is often difficult to characterize using other methods, HETCOR provides both the conventional assignment of shifts to molecular positions and associates many resonances with specific molecules in the asymmetric unit. Such assignments facilitate conformational characterization of the individual molecules of the asymmetric unit and the first such characterization solely from solid-state NMR data is described. HETCOR offers advantages in sensitivity over prior methods that assign resonances in the asymmetric unit by 13C–13C correlations and therefore allows shorter average analysis times in natural abundance materials. The 1H–13C analysis is demonstrated first on materials with known shift assignments from INADEQUATE data (santonin and Ca(OAc)2 phase I) to verify the technique and subsequently is extended to a pair of unknown solids: (+)-catechin and Ca(OAc)2 phase II. Sufficient sensitivity and resolution is achieved in the spectra to provide assignments to one of the specific molecules of the asymmetric unit at over 54% of the sites. PMID:17869558

  7. 13C, 2h NMR studies of structural and dynamical modifications of glucose-exposed porcine aortic elastin.

    PubMed

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

    2015-04-01

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

  8. 13C, 2H NMR Studies of Structural and Dynamical Modifications of Glucose-Exposed Porcine Aortic Elastin

    PubMed Central

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

    2015-01-01

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

  9. Use of solid-state 13C NMR in structural studies of humic acids and humin from Holocene sediments

    USGS Publications Warehouse

    Hatcher, P.G.; VanderHart, D.L.; Earl, W.L.

    1980-01-01

    13C NMR spectra of solid humic substances in Holocene sediments have been obtained using cross polarization with magic-angle sample spinning techniques. The results demonstrate that this technique holds great promise for structural characterizations of complex macromolecular substances such as humin and humic acids. Quantifiable distinctions can be made between structural features of aquatic and terrestrial humic substances. The aliphatic carbons of the humic substances are dominant components suggestive of input from lipid-like materials. An interesting resemblance is also noted between terrestrial humic acid and humin spectra. ?? 1980.

  10. Hyperfine Structure Study of Several Lines of 207Pb I

    NASA Astrophysics Data System (ADS)

    Wasowicz, T. J.; Drozdowski, R.; Kwela, J.

    2005-01-01

    The hfs splitting of four lines from the array 6p7s → 6p2 as well as two lines from the array 6p8s → 6p2 of Pb I have been analyzed. A discharge tube containing metallic isotope 207Pb was used as a light source. Our experiment yields hyperfine splitting constants A for some levels of the configurations 6p2 and 6p7s: A(6p2 1D2) = (20.99 ± 0.43) mK, A(6p2 3P2) = (91.37 ± 0.34) mK, A(6p7s 3P1) = (294.16 ± 0.93) mK, A(6p7s 1P1) = (16.45 ± 0.95) mK and A = (202.04 ± 0.48) mK for the level 6p8s 3P1. Our results are compared with recent theory and other experiments.

  11. Hydrothermal carbon from biomass: structural differences between hydrothermal and pyrolyzed carbons via 13C solid state NMR.

    PubMed

    Falco, Camillo; Perez Caballero, Fernando; Babonneau, Florence; Gervais, Christel; Laurent, Guillaume; Titirici, Maria-Magdalena; Baccile, Niki

    2011-12-01

    The objective of this paper is to better describe the structure of the hydrothermal carbon (HTC) process and put it in relationship with the more classical pyrolytic carbons. Indeed, despite the low energetic impact and the number of applications described so far for HTC, very little is known about the structure, reaction mechanism, and the way these materials relate to coals. Are HTC and calcination processes equivalent? Are the structures of the processed materials related to each other in any way? Which is the extent of polyaromatic hydrocarbons (PAH) inside HTC? In this work, the effect of hydrothermal treatment and pyrolysis are compared on glucose, a good model carbohydrate; a detailed single-quantum double-quantum (SQ-DQ) solid state (13)C NMR study of the HTC and calcined HTC is used to interpret the spectral region corresponding to the signal of furanic and arene groups. These data are compared to the spectroscopic signatures of calcined glucose, starch, and xylose. A semiquantitative analysis of the (13)C NMR spectra provides an estimation of the furanic-to-arene ratio which varies from 1:1 to 4:1 according to the processing conditions and carbohydrate employed. In addition, we formulate some hypothesis, validated by DFT (density functional theory) modeling associated with (13)C NMR chemical shifts calculations, about the possible furan-rich structural intermediates that occur in the coalification process leading to condensed polyaromatic structures. In combination with a broad parallel study on the HTC processing conditions effect on glucose, cellulose, and raw biomass (Falco, C.; Baccile, N.; Titirici, M.-M. Green Chem., 2011, DOI: 10.1039/C1GC15742F), we propose a broad reaction scheme and in which we show that, through HTC, it is possible to tune the furan-to-arene ratio composing the aromatic core of the produced HTC carbons, which is not possible if calcination is used alone, in the temperature range below 350 °C. PMID:22050004

  12. Structure of /sup 13/C studied by pion scattering near the (3,3) resonance

    SciTech Connect

    Seestrom-Morris, S.J.

    1981-09-01

    Good resolution (..pi../sup +/,..pi../sup +/') and (..pi../sup -/,..pi../sup -/') data were obtained for many states in /sup 13/C using the Energetic Pion Channel and Spectrometer at the Los Alamos Meson Physics Facility. Differential cross sections were measured for angles between 20/sup 0/ and 105/sup 0/ at an incident pion energy of 162 MeV for the elastic scattering as well as for states at excitation energies of 3.09, 3.68, 3.85, 7.55, 8.86, 9.5, 11.82, 16.05, 17.92, 21.37, and 21.6 MeV. Excitation functions were measured at momentum transfers of q = 1.1 h fm /sup -1/ and q = 1.4 h fm/sup -1/, for energies between 100 and 300 MeV. A sigma(..pi../sup -/)/sigma(..pi../sup +/) ratio of 9:1 was observed for the first time, indicating a pure neutron particle-hole excitation of a high spin state (J/sup ..pi../ = 9/2/sup +/). Strikingly different energy dependences were found for ..delta..S = 0 and ..delta..S = 1 transitions. Data for all states were compared with the microscopic model calculations of Lee and Kurath. Very good agreement was found between experiment and theory for the strongly excited states and the 9/2/sup +/ state at 9.5 MeV, in sharp contrast to the disagreement for weak transitions. The excitation function data and comparisons with the microscopic model calculations were used to identify the states at 16.05, 17.92, 21.37, and 21.6 MeV as either 7/2/sup +/ or 9/2/sup +/ states. The elastic scattering data were analyzed with an optical modeland the results were found to be consistent with neutron and proton distributions having equal rms radii. The optical potentials generated were used in a collective model analysis of the 3/2/sup -/ (3.68 MeV) and 5/2/sup -/ (7.55 MeV) states. The reduced transition probabilities (B(E2)) derived from the proton parts of the transition strength are in agreement with those determined from electromagnetic measurements.

  13. Precision Hyperfine Structure of 2;^3P State of ^3He with External Magnetic

    NASA Astrophysics Data System (ADS)

    Wu, Qixue; Drake, G. W. F.

    2007-06-01

    The theory of the Zeeman effect can be used to extrapolate precise measurements for the fine structure or the hyperfine structure to zero-field strength. In the present work, the hyperfine structure of 2;^3P state of ^3He with external magnetic fields is precisely calculated. The values of the fields for 32 crossings and five anticrossings of the magnetic sublevels are theoretically predicted for magnetic field strengths up to 1 Tesla. The results are compared with experimental work. We include the linear terms, diamagnetic terms, and the 2̂ relativistic correction terms in the Zeeman Hamiltonian. All related matrix elements are calculated with high accuracy by the use of double basis set Hylleraas type variational wave functions[1,2].[1] Z. -C. Yan and G.W.F. Drake, Phys. Rev. A 50, R1980 (1994).[2] Q. Wu and G.W.F. Drake, J. Phys. B 40, 393 (2007).

  14. Structural characterization of ion-vapor deposited hydrogenated amorphous carbon coatings by solid state {sup 13}C nuclear magnetic resonance

    SciTech Connect

    Xu, Jiao; Kato, Takahisa; Watanabe, Sadayuki; Hayashi, Hideo; Kawaguchi, Masahiro

    2014-01-07

    In the present study, unique structural heterogeneity was observed in ion-vapor deposited a-C:H coatings by performing {sup 13}C MAS and {sup 1}H-{sup 13}C CPMAS experiments on solid state nuclear magnetic resonance devices. Two distinct types of sp{sup 2} C clusters were discovered: one of them denoted as sp{sup 2} C′ in content of 3–12 at. % was non-protonated specifically localized in hydrogen-absent regions, while the other dominant one denoted as sp{sup 2} C″ was hydrogenated or at least proximate to proton spins. On basis of the notably analogous variation of sp{sup 2} C′ content and Raman parameters as function of substrate bias voltage in the whole range of 0.5 kV–3.5 kV, a model of nano-clustering configuration was proposed that the sp{sup 2} C′ clusters were embedded between sp{sup 2} C″ clusters and amorphous sp{sup 3} C matrix as trapped interfaces or boundaries where the sp{sup 2} carbon bonds were highly distorted. Continuous increase of bias voltage would promote the nano-clustering and re-ordering of dominant sp{sup 2} C″ clusters, thus results in a marked decrease of interspace and a change of the content of sp{sup 2} C′ clusters. Further investigation on the {sup 13}C magnetization recovery showed typical stretched-exponential approximation due to the prominent presence of paramagnetic centers, and the stretched power α varied within 0.6–0.9 from distinct types of sp{sup 2} C clusters. Differently, the magnetization recovery of {sup 1}H showed better bi-exponential approximation with long and short T{sub 1}(H) fluctuated within 40–60 ms and 0.1–0.3 ms approximately in content of 80% ± 5% and 20% ± 5%, respectively, varying with various bias voltages. Meanwhile, the interrupted {sup 13}C saturation recovery with an interval of short T{sub 1}(H) showed that most of quick-relaxing protons were localized in sp{sup 2} C″ clusters. Such a short T{sub 1}(H) was only possibly resulted from a relaxation mechanism

  15. Synthesis and biosynthesis of {sup 13}C-, {sup 15}N-labeled deoxynucleosides useful for biomolecular structural determinations

    SciTech Connect

    Ashburn, D.A.; Garcia, K.; Hanners, J.L.; Silks, L.A. III; Unkefer, C.J.

    1994-12-01

    Currently, there is a great emphasis on elucidating the structure, function, and dynamics of DNA. Much of the research involved in this study uses nuclear magnetic resonance (NMR) spectroscopy. Effective use of NMR spectroscopy for DNA molecules with mw > 10,000 requires stable isotope enrichment. We present strategies for site-specific isotopic labeling of the purine bases adenosine and guanosine and the biosynthesis of (U-{sup 13}C, {sup 15}N) DNA from methylotropic bacteria. With commercially available 6-chloropurine, an effective two-step route leads to 2{prime}-deoxy-(amino-{sup 15}N)adenosine (dA). The resulting d(amino-{sup 15}N)A is used in a series of reactions to synthesize 2{prime}-deoxy-(2-{sup 13}C,1,amino-{sup 15}N{sub 2})guanosine or any combination thereof. An improved biosynthesis of labeled DNA has been accomplished using Methylobacterium extorquens AS1. Each liter of growth medium contains 4 g of methanol to yield 1 g of lyophilized cells. As much as 200 mg of RNA per liter of culture has been obtained. We are currently developing large-scale isolation protocols. General synthetic pathways to oligomeric DNA will be presented.

  16. Homonuclear dipolar recoupling techniques for structure determination in uniformly 13C-labeled proteins.

    PubMed

    Ladizhansky, Vladimir

    2009-11-01

    In solid-state NMR magic angle spinning is often used to remove line broadening associated with anisotropic interactions, such as chemical shift anisotropy and dipolar couplings. Dipolar recoupling refers to sequences of pulses designed to reintroduce dipolar interactions that are otherwise averaged by magic angle spinning. One of the key applications of homonuclear (and heteronuclear) dipolar recoupling is for the purpose of protein structure determination. Recoupling experiments, originally designed for applications in spin-pair labeled samples, have been revised in recent years for applications in samples with extensive or uniform incorporation of isotopic labels. In these samples multiple internuclear distances can in principle be probed simultaneously, but the dipolar truncation effects (i.e. attenuation of the effects of weak couplings by strong ones) circumvent such measurements. In this article we review some of the recent developments in homonuclear recoupling methods that allow overcoming this problem.

  17. 13C direct detected COCO-TOCSY: A tool for sequence specific assignment and structure determination in protonless NMR experiments

    NASA Astrophysics Data System (ADS)

    Balayssac, Stéphane; Jiménez, Beatriz; Piccioli, Mario

    2006-10-01

    A novel experiment is proposed to provide inter-residue sequential correlations among carbonyl spins in 13C detected, protonless NMR experiments. The COCO-TOCSY experiment connects, in proteins, two carbonyls separated from each other by three, four or even five bonds. The quantitative analysis provides structural information on backbone dihedral angles ϕ as well as on the side chain dihedral angles of Asx and Glx residues. This is the first dihedral angle constraint that can be obtained via a protonless approach. About 75% of backbone carbonyls in Calbindin D 9K, a 75 aminoacid dicalcium protein, could be sequentially connected via a COCO-TOCSY spectrum. 49 3J values were measured and related to backbone ϕ angles. Structural information can be extended to the side chain orientation of aminoacids containing carbonyl groups. Additionally, long range homonuclear coupling constants, 4JCC and 5JCC, could be measured. This constitutes an unprecedented case for proteins of medium and small size.

  18. Hyperfine structure and isotope shifts in 733.2 nm mixed forbidden line of Pb I

    NASA Astrophysics Data System (ADS)

    Wąsowicz, T. J.; Drozdowski, R.; Kwela, J.

    2007-05-01

    Studies of the hyperfine structure and isotope shifts in 733.2 nm mixed (M1+E2) multipole line of Pb I are presented. As a light source the electrodeless discharge tube was used. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with a CCD camera used as a detector. In the analysis of the spectra a computer simulation technique was used. The experiments with the isotope 207Pb yielded the hyperfine structure splitting constant A for the 3P1 and 1D2 levels of the 6s26p2 ground configuration. In the experiment with natural lead the isotope shifts between four stable isotopes (204, 206, 207, 208) were measured.

  19. A new global operator for two-particle delta functions. [hyperfine structure of muonic helium

    NASA Technical Reports Server (NTRS)

    Drachman, R. J.

    1981-01-01

    A new type of global operator to be used in evaluating matrix elements of two-particle delta functions is introduced. It is based, like the Trivedi one-particle operator, on the Poisson equation and is easier to apply than the method of Hiller, Sucher and Feinberg. After a test in the helium isoelectronic sequence, the new method is applied successfully to the interesting problem of hyperfine structure in muonic helium.

  20. Hyperfine structure and isotope shifts of transitions in neutral and singly ionized ytterbium

    NASA Technical Reports Server (NTRS)

    Berends, R. W.; Maleki, L.

    1992-01-01

    The present experimental investigation of the hyperfine structure and isotopic shifts of transitions in neutral and singly-ionized Yb, which constitute a system of some interest to microwave-frequency standards, used counterpropagating pump and probe laser beams directed through a hollow-cathode discharge lamp. The results obtained are in agreement with previous measurements except in the case of the Yb-173(+) 6 2P0 sub 3/2 state, which is more accurately determined.

  1. The {sup 13}C-pocket structure in AGB models: constraints from zirconium isotope abundances in single mainstream SiC grains

    SciTech Connect

    Liu, Nan; Davis, Andrew M.; Pellin, Michael J.; Gallino, Roberto; Bisterzo, Sara; Savina, Michael R.

    2014-06-20

    We present postprocess asymptotic giant branch (AGB) nucleosynthesis models with different {sup 13}C-pocket internal structures to better explain zirconium isotope measurements in mainstream presolar SiC grains by Nicolussi et al. and Barzyk et al. We show that higher-than-solar {sup 92}Zr/{sup 94}Zr ratios can be predicted by adopting a {sup 13}C-pocket with a flat {sup 13}C profile, instead of the previous decreasing-with-depth {sup 13}C profile. The improved agreement between grain data for zirconium isotopes and AGB models provides additional support for a recent proposal of a flat {sup 13}C profile based on barium isotopes in mainstream SiC grains by Liu et al.

  2. HYPERFINE STRUCTURE CONSTANTS OF ENERGETICALLY HIGH-LYING LEVELS OF ODD PARITY OF ATOMIC VANADIUM

    SciTech Connect

    Güzelçimen, F.; Yapıcı, B.; Demir, G.; Er, A.; Öztürk, I. K.; Başar, Gö.; Kröger, S.; Tamanis, M.; Ferber, R.; Docenko, D.; Başar, Gü. E-mail: sophie.kroeger@htw-berlin.de

    2014-09-01

    High-resolution Fourier transform spectra of a vanadium-argon plasma have been recorded in the wavelength range of 365-670 nm (15,000-27,400 cm{sup –1}). Optical bandpass filters were used in the experimental setup to enhance the sensitivity of the Fourier transform spectrometer. In total, 138 atomic vanadium spectral lines showing resolved or partially resolved hyperfine structure have been analyzed to determine the magnetic dipole hyperfine structure constants A of the involved energy levels. One of the investigated lines has not been previously classified. As a result, the magnetic dipole hyperfine structure constants A for 90 energy levels are presented: 35 of them belong to the configuration 3d {sup 3}4s4p and 55 to the configuration 3d {sup 4}4p. Of these 90 constants, 67 have been determined for the first time, with 23 corresponding to the configuration 3d {sup 3}4s4p and 44 to 3d {sup 4}4p.

  3. Recalcitrance and structural analysis by water-only flowthrough pretreatment of (13)C enriched corn stover stem.

    PubMed

    Foston, Marcus; Trajano, Heather L; Samuel, Reichel; Wyman, Charles E; He, Jian; Ragauskas, Arthur J

    2015-12-01

    This study presents high temperature water-only continuous flowthrough pretreatment coupled with nuclear magnetic resonance (NMR) as a promising analytical tool to examine the plant cell wall, to understand its recalcitrance (i.e., cell wall resistance to deconstruction), and to probe the chemistry occurring during batch pretreatment of biomass. (13)C-enriched corn stover stems were pretreated at 170°C for 60min with a hot-water flow rate of 20mL/min to control fractionation of the cell wall. This approach helped elucidate the nature of plant cell wall chemical recalcitrance and biomass pretreatment chemistry by tracking cell wall fragmentation as a function of time. Fractions of the reactor effluent were collected in a time-resolved fashion and characterized by various NMR techniques to determine the degree and sequence of fragments released, as well as, the chemical composition, molecular structure, and relative molecular weight of those released fragments.

  4. 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.

  5. Methyl [13C]glucopyranosiduronic acids: effect of COOH ionization and exocyclic structure on NMR spin-couplings.

    PubMed

    Zhang, Wenhui; Hu, Xiaosong; Carmichael, Ian; Serianni, Anthony S

    2012-11-01

    Methyl α- and β-D-glucopyranuronides singly labeled with (13)C at C1-C6 were prepared from the corresponding (13)C-labeled methyl D-glucopyranosides, and multiple NMR J-couplings (J(HH), J(CH), and J(CC)) were measured in their protonated and ionized forms in aqueous ((2)H(2)O) solution. Solvated density functional theory (DFT) calculations of J-couplings in structurally related model compounds were performed to determine how well the calculated J-couplings matched the experimental values in saccharides bearing an ionizable substituent. Intraring J(HH) values in both uronide anomers, including (3)J(H4,H5), are unaffected by solution pD, and COOH ionization exerts little effect on J(CH) and J(CC) except for (1)J(C1,H1), (1)J(C4,H4), (1)J(C5,H5), (1)J(C5,C6), and (2)J(C3,C5), where changes of up to 5 Hz were observed. Some of these changes are associated with changes in bond lengths upon ionization; in general, better agreement between theory and experiment was observed for couplings less sensitive to exocyclic C-O bond conformation. Titration of (1)H and (13)C chemical shifts, and some J-couplings, yielded a COOH pK(a) of 3.0 ± 0.1 in both anomers. DFT calculations suggest that substituents proximal to the exocyclic COOH group (i.e., the C4-O4 bond) influence the activation barrier to C5-C6 bond rotation due to transient intramolecular H-bonding. A comparison of J-couplings in the glucopyranuronides to corresponding J-couplings in the glucopyranosides showed that more pervasive changes occur upon conversion from a COOH to a CH(2)OH substituent at C6 than from COOH ionization within the uronides. Twelve J-couplings are affected, with the largest being (1)J(C5,C6) (∼18 Hz larger in the uronides), followed by (2)J(C6,H5) (∼2.5 Hz more negative in the uronides).

  6. 13C-labeled oligosaccharides in breastfed infants' urine: individual-, structure- and time-dependent differences in the excretion.

    PubMed

    Dotz, Viktoria; Rudloff, Silvia; Blank, Dennis; Lochnit, Günter; Geyer, Rudolf; Kunz, Clemens

    2014-02-01

    Human milk oligosaccharides (HMOs) have been paid much attention due to their beneficial effects observed in vitro, e.g., prebiotic, anti-infective and anti-inflammatory properties. However, in vivo investigations with regard to HMO metabolism and functions are rare. The few data available indicate that HMOs are absorbed to a low extent and excreted via urine without noteworthy modifications, whereas the major proportion reaches infant's colon undigested. Via intrinsic (13)C-labeling of HMOs during their biosynthesis in the mammary gland of 10 lactating women, we were able to follow the fate of (13)C-labeled oligosaccharides (OSs) from their secretion in milk to the excretion in the urine of their breastfed infants. To a certain extent, we could therefore discriminate between original HMOs and non-labeled OSs derived from degradation of HMOs or endogenous glycoconjugates. By means of our novel, rapid, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based approach, we found a homogeneous time pattern of isotopomer enrichment in milk among all subjects and between single OS species. In contrast, the time curves from infants' urine varied strongly between individuals and OS species, though the overall MALDI-TOF MS profile resembled those of the mothers' milk. Our data suggest that neutral HMOs might be processed and/or utilized differentially after or upon absorption from the gut, as deduced from their structure-dependent variation in the extent of tracer enrichment and in the retention times in infant's organism. This sheds new light on the role of HMOs within infant's body, beyond the intestine and its microbiota alone.

  7. Major Groove Width Variations in RNA Structures Determined by NMR and Impact of 13C residual chemical shift anisotropy and 1H-13C residual dipolar coupling on refinement

    PubMed Central

    Tolbert, Blanton S; Miyazaki, Yasuyuki; Barton, Shawn; Kinde, Benyam; Starck, Patrice; Singh, Rashmi; Bax, Ad

    2010-01-01

    Ribonucleic acid structure determination by NMR spectroscopy relies primarily on local structural restraints provided by 1H-1H NOEs and J-couplings. When employed loosely, these restraints are broadly compatible with A- and B-like helical geometries and give rise to calculated structures that are highly sensitive to the force fields employed during refinement. A survey of recently reported NMR structures reveals significant variations in helical parameters, particularly the major groove width. Although helical parameters observed in high-resolution X-ray crystal structures of isolated A-form RNA helices are sensitive to crystal packing effects, variations among the published X-ray structures are significantly smaller than those observed in NMR structures. Here we show that restraints derived from aromatic 1H-13C residual dipolar couplings (RDCs) and residual chemical shift anisotropies (RCSAs) can overcome NMR restraint and force field deficiencies and afford structures with helical properties similar to those observed in high-resolution X-ray structures. PMID:20549304

  8. Molecular structure and vibrational bands and 13C chemical shift assignments of both enmein-type diterpenoids by DFT study

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Wu, Yi fang; Wang, Xue liang

    2014-01-01

    We report here theoretical and experimental studies on the molecular structure and vibrational and NMR spectra of both natural enmein type diterpenoids molecule (6, 7-seco-ent-kaurenes enmein type), isolated from the leaves of Isodon japonica (Burm.f.) Hara var. galaucocalyx (maxin) Hara. The optimized geometry, total energy, NMR chemical shifts and vibrational wavenumbers of epinodosinol and epinodosin have been determined using B3LYP method with 6-311G (d,p) basis set. A complete vibrational assignment is provided for the observed IR spectra of studied compounds. The calculated wavenumbers and 13C c.s. are in an excellent agreement with the experimental values. Quantum chemical calculations at the B3LYP/6-311G (d,p) level of theory have been carried out on studied compounds to obtain a set of molecular electronic properties (MEP,HOMO, LUMO and gap energies ΔEg). Electrostatic potential surfaces have been mapped over the electron density isosurfaces to obtain information about the size, shape, charge density distribution and chemical reactivity of the molecules.

  9. Recalcitrance and structural analysis by water-only flowthrough pretreatment of 13C enriched corn stover stem

    DOE PAGES

    Foston, Marcus B.; Trajanob, Heather L.; Samuel, Reichel; Wyman, Charles E.; He, Jian; Ragauskas, Arthur J.

    2015-08-28

    Here, this study presents high temperature water-only continuous flowthrough pretreatment coupled with nuclear magnetic resonance (NMR) as a promising analytical tool to examine the plant cell wall, to understand its recalcitrance (i.e., cell wall resistance to deconstruction), and to probe the chemistry occurring during batch pretreatment of biomass. 13C-enriched corn stover stems were pretreated at 170 °C for 60 min with a hot-water flow rate of 20 mL/min to control fractionation of the cell wall. This approach helped elucidate the nature of plant cell wall chemical recalcitrance and biomass pretreatment chemistry by tracking cell wall fragmentation as a function ofmore » time. Fractions of the reactor effluent were collected in a time-resolved fashion and characterized by various NMR techniques to determine the degree and sequence of fragments released, as well as, the chemical composition, molecular structure, and relative molecular weight of those released fragments.« less

  10. Molecular structure and vibrational bands and 13C chemical shift assignments of both enmein-type diterpenoids by DFT study.

    PubMed

    Wang, Tao; Wu, Yi fang; Wang, Xue liang

    2014-01-01

    We report here theoretical and experimental studies on the molecular structure and vibrational and NMR spectra of both natural enmein type diterpenoids molecule (6, 7-seco-ent-kaurenes enmein type), isolated from the leaves of Isodon japonica (Burm.f.) Hara var. galaucocalyx (maxin) Hara. The optimized geometry, total energy, NMR chemical shifts and vibrational wavenumbers of epinodosinol and epinodosin have been determined using B3LYP method with 6-311G (d,p) basis set. A complete vibrational assignment is provided for the observed IR spectra of studied compounds. The calculated wavenumbers and 13C c.s. are in an excellent agreement with the experimental values. Quantum chemical calculations at the B3LYP/6-311G (d,p) level of theory have been carried out on studied compounds to obtain a set of molecular electronic properties (MEP,HOMO, LUMO and gap energies ΔEg). Electrostatic potential surfaces have been mapped over the electron density isosurfaces to obtain information about the size, shape, charge density distribution and chemical reactivity of the molecules. PMID:24013676

  11. Ground state hyperfine splitting in 6,7Li atoms and the nuclear structure.

    PubMed

    Puchalski, Mariusz; Pachucki, Krzysztof

    2013-12-13

    Relativistic and QED corrections are calculated for a hyperfine splitting of the 2S1/2 ground state in 6,7Li atoms with a numerically exact account for electronic correlations. The resulting theoretical predictions achieve such a precision level that, by comparison with experimental values, they enable determination of the nuclear properties. In particular, the obtained results show that the 7Li nucleus, having a charge radius smaller than 6Li, has about a 40% larger Zemach radius. Together with known differences in the electric quadrupole and magnetic dipole moments, this calls for a deeper understanding of the Li nuclear structure.

  12. Sensitivity of hyperfine structure to nuclear radius and quark mass variation

    SciTech Connect

    Dinh, T. H.; Dunning, A.; Dzuba, V. A.; Flambaum, V. V.

    2009-05-15

    To search for the temporal variation in the fundamental constants, one needs to know dependence of atomic transition frequencies on these constants. We study the dependence of the hyperfine structure of atomic s levels on nuclear radius and, via radius, on quark masses. An analytical formula has been derived and tested by the numerical relativistic Hartree-Fock calculations for Rb, Cd{sup +}, Cs, Yb{sup +}, and Hg{sup +}. The results of this work allow the use of the results of past and future atomic clock experiments and quasar spectra measurements to put constraints on time variation in the quark masses.

  13. Changes in microbial structure and functional communities at different soil depths during 13C labelled root litter degradation

    NASA Astrophysics Data System (ADS)

    Sanaullah, Muhammad; Baumann, Karen; Chabbi, Abad; Dignac, Marie-France; Maron, Pierre-Alain; Kuzyakov, Yakov; Rumpel, Cornelia

    2014-05-01

    Soil organic matter turnover depends on substrate quality and microbial activity in soil but little is known about how addition of freshly added organic material modifies the diversity of soil microbial communities with in a soil profile. We took advantage of a decomposition experiment, which was carried out at different soil depths under field conditions and sampled litterbags with 13C-labelled wheat roots, incubated in subsoil horizons at 30, 60 and 90 cm depth for up to 36 months. The effect of root litter addition on microbial community structure, diversity and activity was studied by determining total microbial biomass, PLFA signatures, molecular tools (DNA genotyping and pyrosequencing of 16S and 18S rDNAs) and extracellular enzyme activities. Automated ribosomal intergenic spacer analysis (ARISA) was also carried out to determine the differences in microbial community structure. We found that with the addition of root litter, total microbial biomass as well as microbial community composition and structure changed at different soil depths and change was significantly higher at top 30cm soil layer. Moreover, in the topsoil, population of both gram-positive and gram-negative bacteria increased with root litter addition over time, while subsoil horizons were relatively dominated by fungal community. Extra-cellular enzyme activities confirmed relatively higher fungal community at subsoil horizons compared with surface soil layer with bacteria dominant microbial population. Bacterial-ARISA profiling illustrated that the addition of root litter enhanced the abundance of Actinobacteria and Proteobacteria, at all three soil depths. These bacteria correspond to copiotrophic attributes, which can preferentially consume of labile soil organic C pools. While disappearance of oligotrophic Acidobacteria confirmed the shifting of microbial communities due to the addition of readily available substrate. We concluded that root litter mixing altered microbial community

  14. On the hyperfine structures of the ground state(s) in the 6Li and 7Li atoms

    NASA Astrophysics Data System (ADS)

    Frolov, A. M.

    2016-06-01

    The hyperfine structure of the ground 22 S-states of the three-electron atoms and ions is investigated. By using our recent numerical values for the doublet electron density at the atomic nucleus, we determine the hyperfine structure of the ground (doublet) 22 S-state(s) in the 6Li and 7Li atoms. Our predicted values (228.2058 and 803.5581 MHz, respectively) agree well with the experimental values 228.20528(8) MHz (6Li) and 803.50404(48) MHz (7Li [R.G. Schlecht and D.W. McColm, Phys. Rev. 142, 11 (1966)]). The hyperfine structures of a number of lithium isotopes with short lifetimes, including 8Li, 9Li, and 11Li atoms are also predicted. The same method is used to obtain the hyperfine structures of the three-electron 7Be+ and 9Be+ ions in their ground 22 S-states. Finally, we conclude that our approach can be generalized to describe the hyperfine structure in the triplet n 3 S-states of the four-electron atoms and ions.

  15. First principles investigation of electronic structures and hyperfine properties of semiconductors and high-[Tc] superconductors

    SciTech Connect

    Sulaiman, S.B.

    1992-01-01

    The first principles Unrestricted Hartree-Fock Cluster procedure has been applied to investigate the electronic structures and associated hyperfine properties of several categories for solid systems. The first category is concerned with the location and nuclear quadrupole interactions (NQI) of fluorine impurity centers in crystalline silicon (c-Si). The Time Differential Perturbed Angular Distribution experiments show that when excited nuclear static fluorine ([sup 19]F*) is implanted into c-Si, two [sup 19]F* centers are formed characterized by two unique axially symmetric electric field gradients (efg). Models have been examined to determine the stable [sup 19]F* sites in the bulk c-Si. The two models, IB and AB, are also able to explain the experimental [sup 19]F* NQI data in crystalline germanium where two centers with axially symmetric efg are observed. The experimental trends of [sup 19]F* NQI are well reproduced by the investigation using the IB and AB models. The second category of the systems investigated deals with the NQI and magnetic hyperfine interaction of [sup 63]Cu in La[sub 2]CuO[sub 4] and YBa[sub 2]Cu[sub 3]O[sub 6] as well as the NQI of [sup 139]La and [sup 135]Ba in the former and the latter compounds respectively. In the third category, the author investigates the possible stable sites of the Muon Spin Rotation ([mu]SR) probe atom, positive muon ([mu][sup +]) in La[sub 2]CuO[sub 4], and the hyperfine field (H[sub hyp]) at [mu][sup +] site in the antiferromagnetic phase of the system. The most stable [mu][sup +] site is at (0.121a, 0.0, 0.110c) of the tetragonal La[sub 2]CuO[sub 4] unit cell. The value of H[sub hyp] at this site is in reasonable order of magnitude with the observed one.

  16. Theory of structure and hyperfine properties of anomalous muonium in elemental semiconductors: Diamond, silicon, and germanium

    SciTech Connect

    Sahoo, N.; Sulaiman, S. B.; Mishra, K. C.; Das, T. P.

    1989-06-15

    A number of possible models for the anomalous muonium (Mu/sup */)center in the elemental semiconductors diamond, silicon, and germanium areinvestigated in detail, both with respect to their stabilities and abilities toexplain the extensive available experimental hyperfine-interaction data, thelatter being the major focus of the present work. Using the unrestrictedHartree-Fock cluster procedure, the electronic structures and potential-energycurves associated with muon positions are obtained for the different models.The results are utilized to obtain hyperfine properties associated with themuon and its neighboring nuclei, including vibrational effects associated withthe muon. Our results show that stability considerations favor both thevacancy-associated (VA) and bond-centered (BC) models for Mu/sup */.The VA model explains all the experimentally observed features of the muonhyperfine properties and provides reasonably good quantitative agreement withexperiment. However, questions remain regarding its formation and ability toexplain level-crossing resonance (LCR) data. On the other hand, although the BCmodel appears to explain the experimental features from LCR measurements, inits present form, it seriously overestimates the strengths of the muonhyperfine interactions as compared to experiment, by more than an order ofmagnitude in some cases. Additionally, it does not explain the trend fromdiamond through germanium. On the basis of the results in this paper for the VAand BC models, the direction for future investigations for understanding thenature of the Mu/sup */ center is commented on.

  17. The theory of the Bohr-Weisskopf effect in the hyperfine structure

    NASA Astrophysics Data System (ADS)

    Karpeshin, F. F.; Trzhaskovskaya, M. B.

    2015-09-01

    Description of the Bohr-Wesskopf effect in the hyperfine structure of few-electron heavy ions is a challenging problem, which can be used as a test of both QED and atomic calculations. However, for twenty years the research has actually been going in a wrong direction, aimed at fighting the Bohr-Weisskopf effect through its cancellation in specific differences. Alternatively, we propose the constructive model-independent way, which enables the nuclear radii and their momenta to be retrieved from the hyper-fine splitting (HFS). The way is based on analogy of HFS to internal conversion coefficients, and the Bohr-Weisskopf effect - to the anomalies in the internal conversion coefficients. It is shown that the parameters which can be extracted from the data are the even nuclear momenta of the magnetization distribution. The radii R2 and - for the first time - R4 are obtained in this way by analysis of the experimental HFS values for the H- and Li-like ions of 209Bi. The critical prediction concerning the HFS for the 2p1/2 state is made. The present analysis shows high sensitivity of the method to the QED effects, which offers a way of precision test of QED. Experimental recommendations are given, which are aimed at retrieving data on the HFS values for a set of a few-electron configurations of each atom.

  18. Hyperfine structure in 229gTh3+ as a probe of the 229gTh→ 229mTh nuclear excitation energy.

    PubMed

    Beloy, K

    2014-02-14

    We identify a potential means to extract the 229gTh→ 229mTh nuclear excitation energy from precision microwave spectroscopy of the 5F(5/2,7/2) hyperfine manifolds in the ion 229gTh3+. The hyperfine interaction mixes this ground fine structure doublet with states of the nuclear isomer, introducing small but observable shifts to the hyperfine sublevels. We demonstrate how accurate atomic structure calculations may be combined with the measurement of the hyperfine intervals to quantify the effects of this mixing. Further knowledge of the magnetic dipole decay rate of the isomer, as recently reported, allows an indirect determination of the nuclear excitation energy.

  19. High-precision hyperfine structure measurement in slow atomic ion beams by collinear laser-rf double resonance

    SciTech Connect

    Amarjit Sen, Childs, W.J.; Goodman, L.S.

    1987-01-01

    A new collinear laser-ion beam apparatus for slow ions (1 to 1.5 keV) has been built for measuring the hyperfine structure of metastable levels of ions with laser-rf double resonance technique. Narrow linewidths of approx.60 kHz (FWHM) have been observed for the first time in such systems. As a first application the hyperfine structure of the 4f/sup 7/(/sup 8/S/sup 0/)5d /sup 9/D/sub J//sup 0/ metastable levels of /sup 151,153/Eu/sup +/ has been measured with high precision. 10 refs., 8 figs.

  20. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: A combined experimental and density functional methods

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Wang, Xueliang

    2015-01-01

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method.

  1. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: a combined experimental and density functional methods.

    PubMed

    Wang, Tao; Wang, Xueliang

    2015-01-25

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method. PMID:25123947

  2. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: a combined experimental and density functional methods.

    PubMed

    Wang, Tao; Wang, Xueliang

    2015-01-25

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method.

  3. 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.

  4. Structural analyses of experimental 13C edited amide I' IR and VCD for peptide β-sheet aggregates and fibrils using DFT-based spectral simulations.

    PubMed

    Welch, William R W; Keiderling, Timothy A; Kubelka, Jan

    2013-09-12

    In the preceding paper, computational models based on density functional theory (DFT) were presented to characterize the sensitivity of vibrational spectroscopic methods (IR, VCD, and Raman) to structural features of β-sheets. Isotopically edited amide I' IR for peptides labeled with (13)C in multiple different sites provides the most structurally distinct signatures of strand alignment, while VCD is sensitive to the sheet twist and intersheet stacking. In this report, we simulate the IR and VCD spectra for models approximating structures of four β-sheet forming peptides previously experimentally studied using these methods with (13)C isotopic editing. Various register alignments are tested. Agreement with experiment is evaluated based on frequency shifts of both the (12)C and (13)C IR amide I' signals, relative intensity patterns, and VCD spectra where available. While for the simulation of IR spectra canonical planar sheets provide a sufficient model system, for VCD simulation twisted, stacked sheets are required in order to reproduce strong couplet-like amide I' VCD. Effects of the solvent (water) and amino acid side chains are also tested by using a simplified, electrostatic solvent model and atomic partial charges for the side chains. Very good agreement with experimental spectra is obtained, particularly for the relative (12)C and (13)C band frequencies. All four peptide models are shown to be antiparallel as had previously been assumed. However, in some cases our simulations are consistent with different register alignment of strands than originally proposed.

  5. Application of Nitrogen and Carbon Stable Isotopes (δ15N and δ13C) to Quantify Food Chain Length and Trophic Structure

    PubMed Central

    Perkins, Matthew J.; McDonald, Robbie A.; van Veen, F. J. Frank; Kelly, Simon D.; Rees, Gareth; Bearhop, Stuart

    2014-01-01

    Increasingly, stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ15N, and carbon range (CR) using δ13C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ15N or δ13C from source to consumer) between trophic levels and among food chains. δ15N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ13C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ13C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of ecological systems

  6. Application of nitrogen and carbon stable isotopes (δ(15)N and δ(13)C) to quantify food chain length and trophic structure.

    PubMed

    Perkins, Matthew J; McDonald, Robbie A; van Veen, F J Frank; Kelly, Simon D; Rees, Gareth; Bearhop, Stuart

    2014-01-01

    Increasingly, stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ(15)N, and carbon range (CR) using δ(13)C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ(15)N or δ(13)C from source to consumer) between trophic levels and among food chains. δ(15)N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ(13)C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ(13)C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of

  7. Hyperfine structure measurement of 87Rb atoms injected into superfluid helium as highly energetic ion beam

    NASA Astrophysics Data System (ADS)

    Imamura, Kei; Furukawa, Takeshi; Yang, Xiaofei; Fujita, Tomomi; Wakui, Takashi; Mitsuya, Yousuke; Hayasaka, Miki; Ichikawa, Yuichi; Hatakeyama, Atsushi; Kobayashi, Tohru; Odashima, Hitoshi; Ueno, Hideki; Matsuo, Yukari; Orochi Collaboration

    2014-09-01

    We have developed a new nuclear laser spectroscopy technique that is called OROCHI (Optical RI-atoms Observation in Condensed Helium as Ioncatcher). In OROCHI, highly energetic ion beam is injected into superfluid helium (He II) and is trapped as atoms. Hyperfine structure (HFS) and Zeeman splitting of trapped atoms is measured using laser-microwave (MW)/radiofrequency (RF) double resonance method. We deduce nuclear moments and spin values from the measured splittings, respectively So far, we measured Zeeman splitting of 84-87Rb atoms To evaluate the validity of the OROCHI method, it is necessary to investigate the following two points not only for Zeeman but also for HFS splitings. (i) What is the accuracy in frequency in our measurement? (ii) How high beam intensity is necessary to observe resonance spectra? For this purpose we conducted online experiment using 87Rb beam and measured the HFS splitting of injected 87Rb atoms in He II.

  8. Precision hyperfine structure spectroscopy of Be isotopes at SLOWRI prototype and prospects of SLOWRI at RIKEN

    SciTech Connect

    Wada, M.; Takamine, A.; Okada, K.; Sonoda, T.; Schury, P.; Kanai, Y.; Kojima, T. M.; Yamazaki, Y.; Yoshida, A.; Kubo, T.; Iimura, H.; Katayama, I.; Ohtani, S.; Wollnik, H.; Schuessler, H. A.

    2009-05-04

    Precision atomic spectroscopy experiments for Be isotopes have been carried out at the prototype universal slow RI-beam (SLOWRI) setup at RIKEN. Radioactive Be ions produced at 1 GeV were decelerated and thermlized in an RF-carpet ion guide. The thermalized ions were transferred to an ion trap where laser cooling was used to reduce the ion energy to the order of 1 {mu}eV. Laser microwave double resonance spectroscopy was performed for the hyperfine structure measurements of trapped and laser cooled {sup 7}Be{sup +} and {sup 11}Be{sup +} ions. Measurements of the S{sub 1/2}{yields}P{sub 1/2},P{sub 3/2} transition frequencies of {sup 7,9,10,11}Be{sup +} ions are also in progress. These results are briefly discussed. Future prospects for expanding the capability of SLOWRI is also discussed.

  9. Hyperfine structure in stellar spectral lines: a little nothing, a help, or a troublemaker?

    NASA Astrophysics Data System (ADS)

    Huehnermann, H.

    Hyperfine structure is common in spectral lines. Hfs splits lines due to nuclear moments and shifts lines of different isotopes (IS). Both effects, even if they are small compared with the line- and instrumental-width, broaden and shift the lines and alter their shape and may lead to erroneous interpretations of spectra of astrophysical interest. The IS permits in principle the observation of isotope abundances (e.g. for H-D) but - if unresolved - shifts lines particularly if intensities are strongly affected by absorption (a fake Doppler shift, especially of interstellar lines). The hfs-splitting and its influence on spectral-lines is investigated with a momentum analysis of the hfs and the line-profile, and of the convolved curve. It is found that the hfs can be misinterpretated as Doppler broadening. In optically dense media (e.g. in stellar interior) hfs and IS may decrease the average transparency.

  10. Intra-annual variability of anatomical structure and δ13C values within tree rings of spruce and pine in alpine, temperate and boreal Europe

    PubMed Central

    Vaganov, Eugene A.; Skomarkova, Marina V.; Knohl, Alexander; Brand, Willi A.; Roscher, Christiane

    2009-01-01

    Tree-ring width, wood density, anatomical structure and 13C/12C ratios expressed as δ13C-values of whole wood of Picea abies were investigated for trees growing in closed canopy forest stands. Samples were collected from the alpine Renon site in North Italy, the lowland Hainich site in Central Germany and the boreal Flakaliden site in North Sweden. In addition, Pinus cembra was studied at the alpine site and Pinus sylvestris at the boreal site. The density profiles of tree rings were measured using the DENDRO-2003 densitometer, δ13C was measured using high-resolution laser-ablation-combustion-gas chromatography-infra-red mass spectrometry and anatomical characteristics of tree rings (tracheid diameter, cell-wall thickness, cell-wall area and cell-lumen area) were measured using an image analyzer. Based on long-term statistics, climatic variables, such as temperature, precipitation, solar radiation and vapor pressure deficit, explained <20% of the variation in tree-ring width and wood density over consecutive years, while 29–58% of the variation in tree-ring width were explained by autocorrelation between tree rings. An intensive study of tree rings between 1999 and 2003 revealed that tree ring width and δ13C-values of whole wood were significantly correlated with length of the growing season, net radiation and vapor pressure deficit. The δ13C-values were not correlated with precipitation or temperature. A highly significant correlation was also found between δ13C of the early wood of one year and the late wood of the previous year, indicating a carry-over effect of the growing conditions of the previous season on current wood production. This latter effect may explain the high autocorrelation of long-term tree-ring statistics. The pattern, however, was complex, showing stepwise decreases as well as stepwise increases in the δ13C between late wood and early wood. The results are interpreted in the context of the biochemistry of wood formation and its linkage

  11. Fermentation and Cost-Effective 13C/15N Labeling of the Nonribosomal Peptide Gramicidin S for Nuclear Magnetic Resonance Structure Analysis

    PubMed Central

    Berditsch, Marina; Afonin, Sergii; Steineker, Anna; Orel, Nataliia; Jakovkin, Igor; Weber, Christian

    2015-01-01

    Gramicidin S (GS) is a nonribosomally synthesized decapeptide from Aneurinibacillus migulanus. Its pronounced antibiotic activity is attributed to amphiphilic structure and enables GS interaction with bacterial membranes. Despite its medical use for over 70 years, the peptide-lipid interactions of GS and its molecular mechanism of action are still not fully understood. Therefore, a comprehensive structural analysis of isotope-labeled GS needs to be performed in its biologically relevant membrane-bound state, using advanced solid-state nuclear magnetic resonance (NMR) spectroscopy. Here, we describe an efficient method for producing the uniformly 13C/15N-labeled peptide in a minimal medium supplemented by selected amino acids. As GS is an intracellular product of A. migulanus, we characterized the producer strain DSM 5759 (rough-convex phenotype) and examined its biosynthetic activity in terms of absolute and biomass-dependent peptide accumulation. We found that the addition of either arginine or ornithine increases the yield only at very high supplementing concentrations (1% and 0.4%, respectively) of these expensive 13C/15N-labeled amino acids. The most cost-effective production of 13C/15N-GS, giving up to 90 mg per gram of dry cell weight, was achieved in a minimal medium containing 1% 13C-glycerol and 0.5% 15N-ammonium sulfate, supplemented with only 0.025% of 13C/15N-phenylalanine. The 100% efficiency of labeling is corroborated by mass spectrometry and preliminary solid-state NMR structure analysis of the labeled peptide in the membrane-bound state. PMID:25795666

  12. Fermentation and Cost-Effective 13C/15N Labeling of the Nonribosomal Peptide Gramicidin S for Nuclear Magnetic Resonance Structure Analysis.

    PubMed

    Berditsch, Marina; Afonin, Sergii; Steineker, Anna; Orel, Nataliia; Jakovkin, Igor; Weber, Christian; Ulrich, Anne S

    2015-06-01

    Gramicidin S (GS) is a nonribosomally synthesized decapeptide from Aneurinibacillus migulanus. Its pronounced antibiotic activity is attributed to amphiphilic structure and enables GS interaction with bacterial membranes. Despite its medical use for over 70 years, the peptide-lipid interactions of GS and its molecular mechanism of action are still not fully understood. Therefore, a comprehensive structural analysis of isotope-labeled GS needs to be performed in its biologically relevant membrane-bound state, using advanced solid-state nuclear magnetic resonance (NMR) spectroscopy. Here, we describe an efficient method for producing the uniformly (13)C/(15)N-labeled peptide in a minimal medium supplemented by selected amino acids. As GS is an intracellular product of A. migulanus, we characterized the producer strain DSM 5759 (rough-convex phenotype) and examined its biosynthetic activity in terms of absolute and biomass-dependent peptide accumulation. We found that the addition of either arginine or ornithine increases the yield only at very high supplementing concentrations (1% and 0.4%, respectively) of these expensive (13)C/(15)N-labeled amino acids. The most cost-effective production of (13)C/(15)N-GS, giving up to 90 mg per gram of dry cell weight, was achieved in a minimal medium containing 1% (13)C-glycerol and 0.5% (15)N-ammonium sulfate, supplemented with only 0.025% of (13)C/(15)N-phenylalanine. The 100% efficiency of labeling is corroborated by mass spectrometry and preliminary solid-state NMR structure analysis of the labeled peptide in the membrane-bound state.

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

    SciTech Connect

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

    2013-11-13

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

  14. /sup 13/C-/sup 13/C spin-spin coupling in structural investigations. VII. Substitution effects and direct carbon-carbon constants of the triple bond in acetyline derivatives

    SciTech Connect

    Krivdin, L.B.; Proidakov, A.G.; Bazhenov, B.N.; Zinchenko, S.V.; Kalabin, G.A.

    1989-01-10

    The effects of substitution on the direct /sup 13/C-/sup 13/C spin-spin coupling constants of the triple bond were studied in 100 derivatives of acetylene. It was established that these parameters exhibit increased sensitivity to the effect of substituents compared with other types of compounds. The main factor which determines their variation is the electronegativity of the substituting groups, and in individual cases the /pi/-electronic effects are appreciable. The effect of the substituents with an element of the silicon subgroup at the /alpha/ position simultaneously at the triple bond or substituent of the above-mentioned type and a halogen atom.

  15. Investigation of hyperfine structure of several major lines in PbI and PbII

    NASA Astrophysics Data System (ADS)

    Wasowicz, T. J.; Drozdowski, R.; Kwela, J.

    2005-06-01

    Hyperfine structure of several lines in neutral and singly ionized lead have been measured. The discharge tube containing metallic isotope 207Pb was used as a light source. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with CCD camera used as a detector. In the analysis of the spectra we used a computer simulation technique. Our experiment yields the following hyperfine splitting constants A: A(6p2 1D2)=(20.69 +/-0.21) mK, A(6p2 3P2)=(91.37+/-0.34) mK A(6p7s 1P1)=(16.45+/-0.95) mK, A(6p7s 3P1)=(293.93+/-0.56) mK, A(6p6d 3F2)=(103.22+/-0.31) mK, A(6p6d 3F3)=(69.12+/-0.28) mK, A(6p8s 3P1)=(202.04+/-0.48) mK, A(6p8p 3P1)=(224.26+/-1.37) mK, A(6p8p 3D2)=(108.02+/-1.14) mK, A(6p7d 3D1)=(-100.86+/-0.53) mK for the levels of PbI and A(6s2 7s 2S1/2)=(352.1+/-1.7) mK, A(6s2 7p 2P3/2)=(13.6+/-1.3) mK, A(6s2 7p 2P1/2)=(70.8+/-1.1) mK for the levels of Pb II. Our results are compared with recent theory and other experiments.

  16. Configurational order-disorder induced metal-nonmetal transition in B13C2 studied with first-principles superatom-special quasirandom structure method

    NASA Astrophysics Data System (ADS)

    Ektarawong, A.; Simak, S. I.; Hultman, L.; Birch, J.; Alling, B.

    2015-07-01

    Due to a large discrepancy between theory and experiment, the electronic character of crystalline boron carbide B13C2 has been a controversial topic in the field of icosahedral boron-rich solids. We demonstrate that this discrepancy is removed when configurational disorder is accurately considered in the theoretical calculations. We find that while the ordered ground state B13C2 is metallic, the configurationally disordered B13C2 , modeled with a superatom-special quasirandom structure method, goes through a metal to nonmetal transition as the degree of disorder is increased with increasing temperature. Specifically, one of the chain-end carbon atoms in the CBC chains substitutes a neighboring equatorial boron atom in a B12 icosahedron bonded to it, giving rise to a B11Ce (BBC) unit. The atomic configuration of the substitutionally disordered B13C2 thus tends to be dominated by a mixture between B12(CBC) and B11Ce (BBC). Due to splitting of valence states in B11Ce (BBC), the electron deficiency in B12(CBC) is gradually compensated.

  17. Redox-dependent structure change and hyperfine nuclear magnetic resonance shifts in cytochrome c

    SciTech Connect

    Feng, Yiquing; Roder, H.; Englander, S.W. )

    1990-04-10

    Proton nuclear magnetic resonance assignments for reduced and oxidized equine cytochrome c show that many individual protons exhibit different chemical shifts in the two protein forms, reflecting diamagnetic shift effects due to structure change, and in addition contact and pseudocontact shifts that occur only in the paramagnetic oxidized form. To evaluate the chemical shift differences for structure change, the authors removed the pseudocontact shift contribution by a calculation based on knowledge of the electron spin g tensor. The g-tensor calculation, when repeated using only 12 available C{sub {alpha}}H proton resonances for cytochrom c from tuna, proved to be remarkably stable. The derived g tensor was then used together with spatial coordinates for the oxidized form to calculate the pseudocontact shift contribution to proton resonances at 400 identifiable sites throughout the protein, so that the redox-dependent chemical shift discrepancy, could be evaluated. Large residual changes in chemical shift define the Fermi contact shifts, where are found as expected to be limited to the immediate covalent structure of the heme and its ligands and to be asymmetrically distributed over the heme. The chemical shift discrepancies observed appear in the main to reflect structure-dependent diamagnetic shifts rather than hyperfine effects due to displacements in the pseudocontact shift field. Although 51 protons in 29 different residues exhibit significant chemical shift changes, the general impressions one of small structural adjustments to redox-dependent strain rather than sizeable structural displacements or rearrangements.

  18. Food web structure in two counter-rotating eddies based on δ15N and δ13C isotopic analyses

    NASA Astrophysics Data System (ADS)

    Waite, A. M.; Muhling, B. A.; Holl, C. M.; Beckley, L. E.; Montoya, J. P.; Strzelecki, J.; Thompson, P. A.; Pesant, S.

    2007-04-01

    We measured the natural inventories of nitrogen and carbon stable isotopes within various ecosystem fractions of two counter-rotating eddies associated with the poleward Leeuwin Current (LC), off Western Australia. Isotopic signatures ( δ15N and δ13C) were used as proxies for trophic transformation of inorganic and organic matter and are the basis for our discussion on food web functions in the two eddies. We present the first measurements of dissolved inorganic nitrogen (DIN) isotopic composition for the eastern Indian Ocean. We show that the large autotrophs (sampled within the >5-μm and >20-μm fractions of particulate organic matter (POM)), including a distinctive diatom population in the warm-core (WC) eddy, are likely to have taken up sources of DIN which were primarily nitrate, while the picoplankton are likely to have assimilated a large fraction of recycled ammonium. We show that phytoplankton in the cold-core (CC) eddy had distinctly more enriched δ15N signatures than in the WC eddy, probably due to the higher vertical fluxes of nitrate into the CC eddy. A clear negative correlation between mixed-layer depth and δ15N in POM across both eddies also supports the role of vertical nitrate fluxes in determining the primary δ15N signature of the autotrophs. Within the WC eddy, there was a significant δ13C-enrichment in comparison to the CC eddy across all size fractions of the mesozooplankton community, which, in combination with a low C:N molar ratio the >200- and >500-μm mesozooplankton size fractions, suggests a healthier mesozooplankton community, with greater lipid storage, in the WC eddy. This is consistent with the greater productivity and biomass of large diatoms in the WC eddy. Larval fish from the WC eddy also had an enriched δ13C signature compared to those from the CC eddy. The WC eddy had higher production rates than the CC eddy, and harboured a physiologically healthier population of zooplankton. Paradoxically, this seemed to occur

  19. Design and operation of a continuous 13C and 15N labeling chamber for uniform or differential, metabolic and structural, plant isotope labeling.

    PubMed

    Soong, Jennifer L; Reuss, Dan; Pinney, Colin; Boyack, Ty; Haddix, Michelle L; Stewart, Catherine E; Cotrufo, M Francesca

    2014-01-16

    Tracing rare stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes and soil organic matter formation to small-scale stable-isotope biomarker probing. Coupling multiple stable isotopes such as (13)C with (15)N, (18)O or (2)H has the potential to reveal even more information about complex stoichiometric relationships during biogeochemical transformations. Isotope labeled plant material has been used in various studies of litter decomposition and soil organic matter formation(1-4). From these and other studies, however, it has become apparent that structural components of plant material behave differently than metabolic components (i.e. leachable low molecular weight compounds) in terms of microbial utilization and long-term carbon storage(5-7). The ability to study structural and metabolic components separately provides a powerful new tool for advancing the forefront of ecosystem biogeochemical studies. Here we describe a method for producing (13)C and (15)N labeled plant material that is either uniformly labeled throughout the plant or differentially labeled in structural and metabolic plant components. Here, we present the construction and operation of a continuous (13)C and (15)N labeling chamber that can be modified to meet various research needs. Uniformly labeled plant material is produced by continuous labeling from seedling to harvest, while differential labeling is achieved by removing the growing plants from the chamber weeks prior to harvest. Representative results from growing Andropogon gerardii Kaw demonstrate the system's ability to efficiently label plant material at the targeted levels. Through this method we have produced plant material with a 4.4 atom%(13)C and 6.7 atom%(15)N uniform plant label, or material that is differentially labeled by up to 1.29 atom%(13)C and 0.56 atom%(15)N in its metabolic and structural components (hot water extractable and hot water

  20. Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

    PubMed Central

    Soong, Jennifer L; Reuss, Dan; Pinney, Colin; Boyack, Ty; Haddix, Michelle L; Stewart, Catherine E; Cotrufo, M. Francesca

    2014-01-01

    Tracing rare stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes and soil organic matter formation to small-scale stable-isotope biomarker probing. Coupling multiple stable isotopes such as 13C with 15N, 18O or 2H has the potential to reveal even more information about complex stoichiometric relationships during biogeochemical transformations. Isotope labeled plant material has been used in various studies of litter decomposition and soil organic matter formation1-4. From these and other studies, however, it has become apparent that structural components of plant material behave differently than metabolic components (i.e. leachable low molecular weight compounds) in terms of microbial utilization and long-term carbon storage5-7. The ability to study structural and metabolic components separately provides a powerful new tool for advancing the forefront of ecosystem biogeochemical studies. Here we describe a method for producing 13C and 15N labeled plant material that is either uniformly labeled throughout the plant or differentially labeled in structural and metabolic plant components. Here, we present the construction and operation of a continuous 13C and 15N labeling chamber that can be modified to meet various research needs. Uniformly labeled plant material is produced by continuous labeling from seedling to harvest, while differential labeling is achieved by removing the growing plants from the chamber weeks prior to harvest. Representative results from growing Andropogon gerardii Kaw demonstrate the system's ability to efficiently label plant material at the targeted levels. Through this method we have produced plant material with a 4.4 atom%13C and 6.7 atom%15N uniform plant label, or material that is differentially labeled by up to 1.29 atom%13C and 0.56 atom%15N in its metabolic and structural components (hot water extractable and hot water residual components

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

    SciTech Connect

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

    2012-07-08

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

  2. 13C-1H dipolar-driven 13C-13C recoupling without 13C rf irradiation in nuclear magnetic resonance of rotating solids

    NASA Astrophysics Data System (ADS)

    Takegoshi, K.; Nakamura, Shinji; Terao, Takehiko

    2003-02-01

    the spinning speed. Further, we showed that the efficiency of the second-order DARR recoupling is not significantly less than that of the first-order DARR. Among the 13C-1H recoupling methods examined, CW irradiation at the n=1 rotary-resonance condition is superior for DARR because it gives a larger 13C-1H dipolar broadening, leading to broadband recoupling. We showed that a broadband-recoupling experiment with the first and the second-order DARR by CW irradiation at the n=1 rotary-resonance condition is applicable to signal assignment as well as structural determination of a multiply/uniformly 13C labeled molecule as demonstrated by two-dimensional 13C-13C DARR polarization-transfer experiments of uniformly 13C, 15N-labeled glycylisoleucine.

  3. Structural studies of pyrido[1,2- c]pyrimidine derivatives by 13C CPMAS NMR, X-ray diffraction and GIAO/DFT calculations

    NASA Astrophysics Data System (ADS)

    Pisklak, Maciej; Król, Marek; Herold, Franciszek; Wolska, Irena; Wawer, Iwona

    2008-12-01

    New 1-aryl- or 1-heteroaryl-piperazinylbutyl derivatives with pyrido[1,2- c]pyrimidine imide moiety, with the expected higher selectivity to 5-HT 1A receptors, have been synthesized. Five hydrochlorides and one base were studied by solid-state 13C CPMAS NMR spectroscopy. 13C chemical shifts indicated that the piperazine ring nitrogen N-1 was protonated. The crystal structure of the base (with 4'F, 3″-CF 3 substituents) was determined by X-ray crystallography. The pyridopyrimidine fragment is essentially planar, and aromatic substituent at C4 is twisted by 59.0°. The crystals are stabilized mainly by the C dbnd O…H sbnd C interactions. The analysis was completed by theoretical calculations of the shielding constants at the GIAO/DFT (B3LYP/6-311+G ∗∗) level.

  4. Microscopic structure of heterogeneous lipid-based formulations revealed by 13C high-resolution solid-state and 1H PFG NMR methods.

    PubMed

    Guillermo, Armel; Gerbaud, Guillaume; Bardet, Michel

    2010-03-01

    Lipid-based formulations such as lip glosses that are very alike on the base of their components may have significant differences in their expected macroscopic properties as cosmetics. To differentiate such formulations, high-resolution (13)C NMR was performed under magic angle spinning to investigate the properties at both molecular and microscopic levels. Temperature studies were carried out and no polymorphism in the solid domains could be evidenced after the thermal treatment performed for obtaining the commercial lip glosses. (13)C NMR spectra also showed that some waxes remain partially solubilized in the oils of formulations. The microscopic structure of the wax-oil liquid domains was worked out on the basis of restricted diffusion properties obtained with proton pulsed-field gradient NMR. Changing a single wax component, in two identical formulations, yields significant morphological differences. In the first one the liquid phase appears as a continuum whereas in the second one, the liquid phase is fractionated into micrometric droplets.

  5. Wavelengths, energy levels and hyperfine structure of Mn II and Sc II.

    NASA Astrophysics Data System (ADS)

    Nave, Gillian; Pickering, Juliet C.; Townley-Smith, Keeley I. M.; Hala, .

    2015-08-01

    For many decades, the Atomic Spectroscopy Groups at the National Institute of Standards and Technology (NIST) and Imperial College London (ICL) have measured atomic data of astronomical interest. Our spectrometers include Fourier transform (FT) spectrometers at NIST and ICL covering the region 1350 Å to 5.5 μm and a 10.7-m grating spectrometer at NIST covering wavelengths from 300 - 5000 Å. Sources for these spectra include high-current continuous and pulsed hollow cathode (HCL) lamps, Penning discharges, and sliding spark discharges. Recent work has focused on the measurement and analysis of wavelengths, energy levels, and hyperfine structure (HFS) constants for iron-group elements. The analysis of FT spectra of Cr I, Mn I, and Mn II is being led by ICL and is described in a companion poster [1]. Current work being led by NIST includes the analysis of HFS in Mn II, analysis of Mn II in the vacuum ultraviolet, and a comprehensive analysis of Sc II.Comprehensive HFS constants for Mn II are needed for the interpretation of stellar spectra and incorrect abundances may be obtained when HFS is omitted. Holt et al. [2] have measured HFS constants for 59 levels of Mn II using laser spectroscopy. We used FT spectra of Mn/Ni and Mn/Cu HCLs covering wavelength ranges from 1350 Å to 5.4 μm to confirm 26 of the A constants of Holt et al. and obtain values for roughly 40 additional levels. We aim to obtain HFS constants for the majority of lines showing significant HFS that are observed in chemically-peculiar stars.Spectra of Sc HCLs have been recorded from 1800 - 6700 Å using a vacuum ultraviolet FT spectrometer at NIST. Additional measurements to cover wavelengths above 6700 Å and below 1800 Å are in progress. The spectra are being analyzed by NIST and Alighar Muslim University, India in order to derive improved wavelengths, energy levels, and hyperfine structure parameters.This work was partially supported by NASA, the STFC and PPARC (UK), the Royal Society of the UK

  6. Solid state {sup 1}H and {sup 13}C NMR structural investigation of a poly(ethylene oxide) hydrogel

    SciTech Connect

    Badiger, M.V.; Graham, N.B.; Law, R.V.; Snape, C.E.

    1993-12-31

    A cross-linked poly (ethylene oxide)/polyurethane hydrogel cross-linked with 1,2,6 hexane-triol and designated PEG4050/1HT [measured M{sup n} of 4050 for poly (ethylene oxide) glycol (PEG) and a mole ratio of 1:1 for the PEG to the 1,2,6 hexane-triol] has been characterized by high resolution {sup 1}H and {sup 13}C NMR. {sup 1}H thermal (T{sub 1}) and rotating frame (T{sub 1{rho}}) and {sup 13}CT{sub 1} relaxation times were determined for the powdered dry and swollen hydrogel with the standard variants of the cross-polarization pulse sequence which was used in conjunction with magic-angle spinning (MAS). The rotating frame relaxation measurements confirmed that crystalline and amorphous regions were present in the dry hydrogel but showed unabiguously that the crystalline regions are confined to the poly (ethylene oxide) chains, Upon hydration, there is a decrease in the cross polarization efficiency from the enhanced mobility by the poly (ethylene oxide) chains are affected to a much greater extent that the urethane and hexane segments, the characteristic time constant, T{sub CH} increasing by more than order of magnitude compared to no more than a factor of two for the latter. Clearly, the hydration involves hydrogen bonding between the water and principally the oxygens in the poly (ethylene oxide) chains. The {sup 1}H MAS spectra of the dry and hydrated samples confirmed that considerable averaging of the dipolar interactions occurs on hydration to give a well-resolved spectrum.

  7. Hyperfine structure effects in Doppler-broadening thermometry on water vapor at 1.4 μm

    NASA Astrophysics Data System (ADS)

    Domenica De Vizia, Maria; Odintsova, Tatyana; Gianfrani, Livio

    2016-04-01

    This article builds upon a previous work dealing with the budget of uncertainties associated to our recent determination of the Boltzmann constant by means of Doppler broadening thermometry. We report on the outcomes of theoretical calculations and numerical simulations aimed to precisely quantify the influence of the unresolved hyperfine structure of a given ortho component of the \\text{H}218 O spectrum at 1.4 μm on the measurement of the Doppler width of the line itself. We have found that, if the hyperfine structure of the {{4}4,1}\\to {{4}4,0} line of the {ν1}+{ν3} band was ignored, the spectroscopic measurement of the Boltzmann constant would be affected by a relative systematical deviation of 4\\cdot {{10}-8} .

  8. Anomalous magnetic hyperfine structure of the 229Th ground-state doublet in muonic atoms

    NASA Astrophysics Data System (ADS)

    Tkalya, E. V.

    2016-07-01

    The magnetic hyperfine (MHF) splitting of the ground and low-energy 3 /2+(7.8 ±0.5 eV) levels in the 229Th nucleus in the muonic atom (μ1S1 /2 -229Th) * is calculated considering the distribution of the nuclear magnetization in the framework of the collective nuclear model with wave functions of the Nilsson model for the unpaired neutron. It is shown that (a) deviation of the MHF structure of the isomeric state exceeds 100% from its value for a pointlike nuclear magnetic dipole (the order of sublevels is reversed); (b) partial inversion of levels of the 229Th ground-state doublet and spontaneous decay of the ground state to the isomeric state occur; (c) the E 0 transition, which is sensitive to differences in the mean-square charge radii of the doublet states, is possible between mixed sublevels with F =2 ; and (d) MHF splitting of the 3 /2+ isomeric state may be in the optical range for certain values of the intrinsic gK factor and a reduced probability of a nuclear transition between the isomeric and the ground states.

  9. Structural, optical, hyperfine and magnetization studies of ZnO encapsulated α-Fe nanoparticles

    SciTech Connect

    Rathore, A.K.; Pati, S.P.; Roychowdhury, A.; Das, D.

    2014-12-15

    We report the successful preparation and characterization of magnetic-fluorescent nanoparticles (NPs) by overcoming the difficulty of handling α-Fe nanoparticles that are less stable and have high affinity to get oxidized in air even at room temperature. Nanocrystalline α-Fe particles embedded by ZnO have been synthesized by a two step chemical route. Concentration of α-Fe has been varied as 15, 30 and 50 wt% of the sample. Detailed investigations on structural, hyperfine, optical and magnetic characteristics have been carried out. X-ray diffraction, transmission electron microscopy and fourier transform infrared spectroscopy studies have been used to confirm the coexistence of Fe and ZnO phases in the nanocomposites (NCs). The presence of α-Fe is also confirmed by Mössbauer spectroscopy. However, other forms of iron are also detected in the sample. UV–vis spectrum of nanocomposites shows a red shift with respect to the pristine ZnO which is attributed to the electron transfer between Fe and ZnO that provides support to the formation of the Fe- ZnO NC. The photoluminescence (PL) spectra of Fe-ZnO nanocomposites exhibit blue shift of the UV and weaker visible emission lines compared to the pristine ZnO. Nanocomposites are found to be magnetically soft having high saturation magnetization with very low remanence. Low temperature coercivity enhancement due to freezing of uncompensated surface spins is also found in all samples.

  10. MODELING MOLECULAR HYPERFINE LINE EMISSION

    SciTech Connect

    Keto, Eric; Rybicki, George

    2010-06-20

    In this paper, we discuss two approximate methods previously suggested for modeling hyperfine spectral line emission for molecules whose collisional transition rates between hyperfine levels are unknown. Hyperfine structure is seen in the rotational spectra of many commonly observed molecules such as HCN, HNC, NH{sub 3}, N{sub 2}H{sup +}, and C{sup 17}O. The intensities of these spectral lines can be modeled by numerical techniques such as {Lambda}-iteration that alternately solve the equations of statistical equilibrium and the equation of radiative transfer. However, these calculations require knowledge of both the radiative and collisional rates for all transitions. For most commonly observed radio frequency spectral lines, only the net collisional rates between rotational levels are known. For such cases, two approximate methods have been suggested. The first method, hyperfine statistical equilibrium, distributes the hyperfine level populations according to their statistical weight, but allows the population of the rotational states to depart from local thermal equilibrium (LTE). The second method, the proportional method, approximates the collision rates between the hyperfine levels as fractions of the net rotational rates apportioned according to the statistical degeneracy of the final hyperfine levels. The second method is able to model non-LTE hyperfine emission. We compare simulations of N{sub 2}H{sup +} hyperfine lines made with approximate and more exact rates and find that satisfactory results are obtained.

  11. Secondary structure and side-chain sup 1 H and sup 13 C resonance assignments of calmodulin in solution by heteronuclear multidimensional NMR spectroscopy

    SciTech Connect

    Ikura, Mitsuhiko; Spera, S.; Barbato, G.; Kay, L.E.; Bax, A. ); Krinks, M. )

    1991-09-24

    Heteronuclear 2D and 3D NMR experiments were carried out on recombinant Drosophila calmodulin (CaM), a protein of 148 residues and with molecular mass of 16.7 kDa, that is uniformly labeled with {sup 15}N and {sup 13}C to a level of > 95%. Nearly complete {sup 1}H and {sup 13}C side-chain assignments for all amino acid residues are obtained by using the 3D HCCH-COSY and HCCH-TOCSY experiments that rely on large heteronuclear one-bond scalar couplings to transfer magnetization and establish through-bond connectivities. The secondary structure of this protein in solution has been elucidated by a qualitative interpretation of nuclear Overhauser effects, hydrogen exchange data, and {sup 3}J{sub HNH{alpha}} coupling constants. A clear correlation between the {sup 13}C{alpha} chemical shift and secondary structure is found. The secondary structure in the two globular domains of Drosophila CaM in solution is essentially identical with that of the X-ray crystal structure of mammalian CaM which consists of two pairs of a helix-loop-helix motif in each globular domain. The existence of a short antiparallel {beta}-sheet between the two loops in each domain has been confirmed. The eight {alpha}-helix segments identified from the NMR data are located at Glu-6 to Phe-19, thr-29 to Ser-38, Glu-45 to Glu-54, Phe-65 to Lys-77, Glu-82 to Asp-93, Ala-102 to Asn-111, Asp-118 to Glu-127, and Tyr-138 to Thr-146. Although the crystal structure has a long central helix from Phe-65 to Phe-92 that connects the two globular domains, NMR data indicate that residues Asp-78 to Ser-81 of this central helix adopt a nonhelical conformation with considerable flexibility.

  12. 13C CP/MAS NMR Studies of Hemoprotein Models with and without an Axial Hindered Base: (13)C Shielding Tensors and Comparison with Hemoproteins and X-ray Structural Data.

    PubMed

    Gerothanassis, I. P.; Momenteau, M.; Barrie, P. J.; Kalodimos, C. G.; Hawkes, G. E.

    1996-04-24

    13C cross-polarization magic-angle-spinning (CP/MAS) NMR spectra of several carbonmonoxide (93-99% (13)C enriched) hemoprotein models with 1,2-dimethylimidazole (1,2-diMeIm) and 1-methylimidazole (1-MeIm) as axial ligands are reported. This enables the (13)CO spinning sideband manifold to be measured and hence the principal components of the (13)CO chemical shift tensor to be obtained. Negative polar interactions in the binding pocket of the cap porphyrin model and inhibition of Fe-->CO back-donation result in a reduction in shielding anisotropy; on the contrary, positive distal polar interactions result in an increase in the shielding anisotropy and asymmetry parameter in some models. It appears that the axial hindered base 1,2-dimethylimidazole has little direct effect on the local geometry at the CO site, despite higher rates of CO desorption being observed for such complexes. This suggests that the mechanism by which steric interactions are released for the 1,2-diMeIm complexes compared to 1-MeIm complexes does not involve a significant increase in bending of the Fe-C-O unit. The asymmetry of the shielding tensor of all the heme model compounds studied is smaller than that found for horse myoglobin and rabbit hemoglobin.

  13. Hyperfine structure of the ground state of para- D2+ by high-resolution Rydberg-state spectroscopy and multichannel quantum defect theory

    NASA Astrophysics Data System (ADS)

    Cruse, H. A.; Jungen, Ch.; Merkt, F.

    2008-04-01

    The hyperfine structure of transitions between n=51-53d and n=54-57f Rydberg states belonging to series converging on the XΣ2g+ (v+=0,N+=1) , ground state of para- D2+ has been measured at an experimental resolution of about 1 MHz by millimeter-wave spectroscopy and assigned on the basis of combination differences. A map of the hyperfine structure of these Rydberg states has been determined. The analysis of the hyperfine structure of the nf series by multichannel quantum defect theory has confirmed the experimental assignments and enabled the derivation of the hyperfine structure of the ground state of para- D2+ with a precision of better than 1 MHz.

  14. Rotational Spectroscopy of CF_2ClCCl_3 and Analysis of Hyperfine Structure from Four Quadrupolar Nuclei

    NASA Astrophysics Data System (ADS)

    Kisiel, Zbigniew; Bialkowska-Jaworska, Ewa; Uriarte, Iciar; Basterretxea, Francisco J.; Cocinero, Emilio J.

    2016-06-01

    CF_2ClCCl_3 has recently been identified among several new ozone- depleting substances in the atmosphere. There are no literature reports concerning rotational spectroscopy of this molecule, although we were recently able to report its first chirped pulse, supersonic expansion spectrum. CF_2ClCCl_3 has a rather small dipole moment so that the spectrum is weak and each transition displays very complex nuclear quadrupole hyperfine structure resulting from the presence of four chlorine nuclei. We have presently been able to carry out a complete analysis of the hyperfine structure by combining the information from chirped pulse spectra with dedicated higher resolution measurements made with a cavity supersonic expansion instrument. The hyperfine analysis was carried out with Pickett's SPFIT/SPCAT package and the sizes of Hamiltonian matrices are sufficiently large to require the use of 64-bit compilation of these programs (made available for both Windows and Linux systems on the PROSPE website). The resulting fit is to within experimental accuracy and is supported by ab initio calculations. The precise values of off-diagonal hyperfine constants for all nuclei lead to useful angular information that is complementary to direct structural information from moments of inertia. J.C.Laube, M.J.Newland, C.Hogan, et al., Nature Geoscience 7, 266 (2014). Z.Kisiel, E.Białkowska-Jaworska, L.Pszczółkowski, I.Uriarte, P.Ejica, F.J.Basterretxea, E.J.Cocinero, 70th ISMS, Champaign-Urbana, Illinois, RF-11 (2015). Z.Kisiel, E.Białkowska-Jaworska, L.Pszczółkowski, J.Chem.Phys. 109, 10263 (1998).

  15. Glucuronoxylomannan of Cryptococcus neoformans serotype B: structural analysis by gas-liquid chromatography-mass spectrometry and 13C-nuclear magnetic resonance spectroscopy.

    PubMed

    Turner, S H; Cherniak, R

    1991-04-01

    The major extracellular polysaccharide (glucuronoxylomannan, GXM) from six strains of Cryptococcus neoformans serotype B was characterized by gas-liquid chromatography (g.l.c.), g.l.c.-mass spectrometry (g.l.c.-m.s.), and nuclear magnetic resonance (n.m.r.) spectroscopy. Ultrasonic irradiation (u.i.) was used to reduce the mol.wt. of native GXM from 9.75 x 10(5) to 1.15 x 10(5) without apparent change in its composition (GXM-S). The Xylp:Manp:GlcpA molar ratio of the GXM and GXM-S from the six strains of C. neoformans serotype B is approximately 3.5:3.0:0.6. GXM-S was O-deacetylated (GXM-D) by treatment with NH4OH. The 13C-n.m.r. analysis of GXM-D gave spectra that served as characteristic fingerprints of the structure and also facilitated the assignment of the anomeric carbon resonances to specific structural moieties present in GXM-D. The GXM-D from each serotype B strain was found to be similar by 13C-n.m.r. spectroscopy. The structure contains a linear (1----3)-alpha-D-Manp backbone substituted with 2-O-beta-GlcpA and 2-O-beta-Xylp. beta-Xylp is also O-4 linked to the Manp substituted with GlcpA. In addition, a model for the disposition of the Xylp and GlcpA side chain substituents along the mannopyranan backbone is proposed, based upon results from the combination of g.l.c.-m.s. and 13C-n.m.r. spectroscopy. PMID:1773425

  16. Dipolar-dephasing 13C NMR studies of decomposed wood and coalified xylem tissue: Evidence for chemical structural changes associated with defunctionalization of lignin structural units during coalification

    USGS Publications Warehouse

    Hatcher, P.G.

    1988-01-01

    A series of decomposed and coalified gymnosperm woods was examined by conventional solid-state 13C nuclear magnetic resonance (NMR) and by dipolar-dephasing NMR techniques. The results of these NMR studies for a histologically related series of samples provide clues as to the nature of codification reactions that lead to the defunctionalization of lignin-derived aromatic structures. These reactions sequentially involve the following: (1) loss of methoxyl carbons from guaiacyl structural units with replacement by hydroxyls and increased condensation; (2) loss of hydroxyls or aryl ethers with replacement by hydrogen as rank increases from lignin to high-volatile bituminous coal; (3) loss of alkyl groups with continued replacement by hydrogen. The dipolar-dephasing data show that the early stages of coalification in samples examined (lignin to lignite) involve a decreasing degree of protonation on aromatic rings and suggest that condensation is significant during coalification at this early stage. An increasing degree of protonation on aromatic rings is observed as the rank of the sample increases from lignite to anthracite.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  18. Carbanion substituent effects on 1-disubstituted 4-(4'-pyridyl)pyridinium methylide structures using 13C NMR spectroscopy and DFT method

    NASA Astrophysics Data System (ADS)

    Depature, Ludovic; Surpateanu, Gheorghe

    2003-11-01

    The structure of 1-disubstituted 4-(4'-pyridyl)pyridinium methylides or 4,4'-bipyridinium monoylides ( 2- 5) with a wide range of carbanion substituents, were determined using 13C NMR signals in dimethylsufoxide (DMSO- d6) solution. For the first time, we developed a systematic determination of 13C NMR chemical shifts of the ylidic carbon using a long-range correlated ( 1H- 13C) HMBC experiments. The chemical shift values are discussed in terms of magnetic and/or electronic effects of the ylidic carbon substituents. From the extracted NMR parameters and the results of accompanying quantum chemical DFT calculations for a three-dimensional (3D)-structure representation, we found a long distance electronic effect where the aromatic heterocycle C2C6 and C4 centers are perturbed according to the electron acceptor strengths of ylidic carbon substituents in all monoylides ( 2- 5c) capable to stabilize in a planar conformation. No significant perturbation on C2C6 and C4 centers are found in all other monoylides ( 2- 5a, b) that adopted a non-planar conformation. Good similar linear dependences of the chemical shift variation Δ (calculated by the differences of analogous C2C6 and C4 chemical shifts in non-planar and planar monoylides) with the ylidic carbon chemical shifts modulated by the strength of electron acceptor substituents pointed out the resonance interaction or the delocalization phenomena of the ylidic carbon charge on the heterocycle.

  19. Structural Modification and Bioavailability of Starch Components As Related to the Extent of Maillard Reaction: An Enzymatic Degradation and a Solid-State (13)C CPMAS NMR Study.

    PubMed

    Pizzoferrato; Paci; Rotilio

    1998-02-16

    Starch and starch components, amylose and amylopectin, from potato, have been studied in order to understand the modifications, induced by different levels of the Maillard reaction occurring in the presence of amino acids (L-lysine in this study), in the macromolecular structure and digestibility. Structural characterization was performed by (13)C CPMAS NMR, and differences in the bioavailability of these polymers were studied by enzymatic degradation kinetics. Results obtained reveal that changes are induced by the Maillard reaction, whose occurrence has been verified and measured by the furosine (epsilon-N-2-furoylmethyl-L-lysine) evaluation, on the macromolecular structure of starchy materials and on their enzymatic susceptibility. Lysine seems to act as a disordering agent; a loss of crystallinity is evident for starch and amylopectin and, in particular, for amylose. Finally, within the same sample, as the lysine concentration increases, the polymer digestibility decreases, confirming that structural organization is not the only determinant of starch digestibility. PMID:10554259

  20. Hyperfine structure constants of singly ionized manganese obtained from analysis of Fourier Transform spectra

    NASA Astrophysics Data System (ADS)

    Townley-Smith, Keeley; Nave, Gillian; Imperial College London

    2016-01-01

    There is an on-going project in the Atomic Spectroscopy Group at NIST to obtain comprehensive spectral data for all of the singly ionized iron group elements and acquire more accurate energy levels, wavelengths and hyperfine structure (HFS) constants. The heavy abundance of the iron group elements and their contributions to a wide range of stellar spectra makes them of interest for astrophysical observations.Existing spectroscopic data for Mn are insufficient to model spectra obtained from HgMn stars such as HD 175640. Since manganese has an odd number of nucleons, its spectral lines generally exhibit HFS, a relativistic effect due to interaction between the magnetic moment of the nucleus and the orbiting electrons. If proper treatment of line broadening effects such as HFS is not taken, there is a poor fit of the lines in stellar spectra, leading to an overestimate of the abundance of Mn. The abnormally high abundance of manganese in HgMn stars means both weak and strong transitions are important. Weak lines may not be observed in the laboratory, but HFS constants for them can be derived from stronger transitions that combine with the two levels involved in the weak transition.Holt et al. (1999) measured HFS constants for 56 energy levels using laser spectroscopy. We have analyzed Fourier Transform spectra of a high current Mn/Ni hollow cathode lamp to obtain magnetic dipole A constants levels of Mn II. The A constants of Holt et al. (1999, MNRAS 306, 1007) for the z5P, z7P2, a5P and z5F levels were the starting point for our analysis, from which we derived A constants for 71 energy levels, including 51 previously unstudied levels. Our A constant for the a7S3 ground level differs by 5x10-4 cm-1 from that of Blackwell-Whitehead et al. (2005, ApJS 157, 402) and has a factor of 6 lower uncertainty.

  1. Hyperfine field and magnetic structure in the B phase of CeCoIn5

    SciTech Connect

    Graf, Matthias J; Curro, Nicholas J; Young, Ben - Li; Urbano, Ricardo R

    2009-01-01

    We re-analyze Nuclear Magnetic Resonance (NMR) spectra observed at low temperatures and high magnetic fields in the field-induced B-phase of CeCoIn{sub 5}. The NMR spectra are consistent with incommensurate antiferromagnetic order of the Ce magnetic moments. However, we find that the spectra of the In(2) sites depend critically on the direction of the ordered moments, the ordering wavevector and the symmetry of the hyperfine coupling to the Ce spins. Assuming isotropic hyperfine coupling, the NMR spectra observed for H {parallel} [100] are consistent with magnetic order with wavevector Q = {pi}(1+{delta}/a, 1/a, 1/c) and Ce moments ordered antiferromagnetically along the [100] direction in real space. If the hyperfine coupling has dipolar symmetry, then the NMR spectra require Ce moments along the [001] direction. The dipolar scenario is also consistent with recent neutron scattering measurements that find an ordered moment of 0.15{micro}{sub B} along [001] and Q{sub n} = {pi}(1+{delta}/a, 1+{delta}c, 1/c) with incommensuration {delta} = 0.12 for field H {parallel} [1{bar 1}0]. Using these parameters, we find that the hyperfine field is consistent with both experiments. We speculate that the B phase of CeCoIn{sub 5} represents an intrinsic phase of modulated superconductivity and antiferromagnetism that can only emerge in a highly clean system.

  2. New structural information on a humic acid from two-dimensional 1H-13C correlation solid-state nuclear magnetic resonance.

    PubMed

    Mao, J D; Xing, B; Schmidt-Rohr, K

    2001-05-15

    New information on the chemical structure of a peat humic acid has been obtained using a series of two-dimensional 1H-13C heteronuclear correlation solid-state NMR (HETCOR) experiments with different contact times and with spectral editing by dipolar dephasing and 13C transverse relaxation filtering. Carbon-bonded methyl groups (C-CH3) are found to be near both aliphatic and O-alkyl but not aromatic groups. The spectra prove that most OCH3 groups are connected directly with the aromatic rings, as is typical in lignin. As a result, about one-third of the aromatic C-O groups is not phenolic C-OH but C-OCH3. Both protonated and unprotonated anomeric O-C-O carbons are identified in the one- and two-dimensional spectra. COO groups are found predominantly in OCHn-COO environments, but some are also bonded to aromatic rings and aliphatic groups. All models of humic acids in the literature lack at least some of the features observed here. Compositional heterogeneity was studied by introducing 1H spin diffusion into the HETCOR experiment. Comparison with data for a synthetic polymer, polycarbonate, indicates that the separation between O-alkyl and aromatic groups in the humic acid is less than 1.5 nm. However, transverse 13C relaxation filtering under 1H decoupling reveals heterogeneity on a nanometer scale, with the slow-relaxing component being rich in lignin-like aromatic-C-O-CH3 moieties and poor in COO groups.

  3. Structural characterization and molecular order of rodlike mesogens with three- and four-ring core by XRD and 13C NMR spectroscopy.

    PubMed

    Reddy, M Kesava; Reddy, K Subramanyam; Yoga, K; Prakash, M; Narasimhaswamy, T; Mandal, A B; Lobo, Nitin P; Ramanathan, K V; Rao, D S Shankar; Prasad, S Krishna

    2013-05-01

    Structural characterizations using XRD and (13)C NMR spectroscopy of two rodlike mesogens consisting of (i) three phenyl ring core with a polar cyano terminal and (ii) four phenyl ring core with flexible dodecyl terminal chain are presented. The three-ring-core mesogen with cyano terminal exhibits enantiotropic smectic A phase while the four-ring mesogen reveals polymesomorphism and shows enantiotropic nematic, smectic C, and tilted hexatic phases. The molecular organization in the three-ring mesogen is found to be partial bilayer smectic Ad type, and the interdigitation of the molecules in the neighboring layers is attributed to the presence of the polar terminal group. For the four-ring mesogen, the XRD results confirm the existence of the smectic C and the tilted hexatic mesophases. A thermal variation of the layer spacing across the smectic C phase followed by a discrete jump at the transition to the tilted hexatic phase is also observed. The tilt angles have been estimated to be about 45° in the smectic C phase and about 40° in tilted hexatic phase. (13)C NMR results indicate that in the mesophase the molecules are aligned parallel to the magnetic field. From the (13)C-(1)H dipolar couplings determined from the 2D experiments, the overall order parameter for the three-ring mesogen in its smectic A phase has been estimated to be 0.72 while values ranging from 0.88 to 0.44 have been obtained for the four-ring mesogen as it passes from the tilted hexatic to the nematic phase. The orientations of the different rings of the core unit with respect to each other and also with respect to the long axis of the molecule have also been obtained. PMID:23627902

  4. Fingerprints of molecular structure and hydrogen bonding effects in the /sup 13/C NMR spectra of monosaccharides with partially deuterated hydroxyls

    SciTech Connect

    Reuben, J.

    1984-10-17

    A new NMR approach to structure elucidation of carbohydrates in solution is presented. Examined in detail are the isotopic multiplets in /sup 13/C NMR spectra that result from partial deuteration of the hydroxyls for a series of monosaccharides and some of their deoxy and methyl glycoside derivatives in Me/sub 2/SO-d/sub 6/ solutions. Chemical shift and isotope effect data are presented for the pyranose and furanose forms of aldopentoses, aldohexoses, and ketohexoses. The results show that the magnitude of the ..gamma.. effect resulting from deuteration of a hydroxyl on a vicinal carbon atoms is sensitive to the relative geometric relationship, cis or trans, of the hydroxyls in vicinal diol arrays. Thus, the multiplet pattern for carbons 3 and 4 of the pyranose ring can serve as a fingerprint of molecular structure at the pentopyranose level. The aldopentoses and ketohexoses are amenable to structural analysis by this simple approach. Ambiguity will arise for pairs of aldohexoses related to each other by epimerization at C5. Intramolecular hydrogen bonding between the hydroxyls at C2 and C4 in ..cap alpha..-D-talopyranose gives rise to some unusual effects. A mechanism involving isotopic perturbation of the equilibrium between the hydrogen-bonded structures O4-H...O2-H and O2-H...O4-H is suggested as the possible source of these effects. Similarly, the extra splitting observed in the /sup 13/C resonance of C3 of ..beta..-D-fucofuranose are rationalized in terms of an equilibrium between the hydrogen-bonded structures C5-O5-H...O3-H and Cl-O1-H...O3-H. The approach of isotopic multiplets appears to be uniquely suited for the study of such structures.

  5. Structural study of humic acids during composting of activated sludge-green waste: elemental analysis, FTIR and 13C NMR.

    PubMed

    Amir, Soumia; Jouraiphy, Abdelmajid; Meddich, Abdelilah; El Gharous, Mohamed; Winterton, Peter; Hafidi, Mohamed

    2010-05-15

    The humic acids extracted from a compost of activated sludge at different stages of maturity were characterized by various chemical techniques. Elemental analysis showed the reduction of H, and the H/C and C/N ratios and an increase in the proportion of N and S. At the end of composting C% and O% presented the same values as initially, although they increased in the intermediate stage. Based on the ratios of FTIR absorbance it was shown that the end product was enriched in etherified and peptidic compounds absorbing at 1384, 1034 and 1544 cm(-1). The alkyl and other N-rich and oxidized recalcitrant structures compose the new humic polymers produced during composting. In principal components analysis, the first axis, PC1: 49.75% considers the variability between structures in decomposition from the other parameters that concern the stable new humic polymers formed after composting. PC2 (40.5%) shows a negative correlation between (aromatic carbon, FA level) and (aliphatic carbon, HA level) during composting. PMID:20106591

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

    NASA Astrophysics Data System (ADS)

    Kalsbeek, Nicoline; Schaumburg, Kjeld; Larsen, Sine

    1993-10-01

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

  7. Analysis of the Rotational Structure in the High-Resolution Infrared Spectrum of trans-Hexatriene-1-13C1; a Semiexperimental Equilibrium Structure for the C6 Backbone for trans-Hexatriene

    SciTech Connect

    Craig, Norman C.; Tian, Hengfeng; Blake, Thomas A.

    2012-03-29

    trans-Hexatriene-1-13C1 (tHTE-1-13C1) has been synthesized, and its high-resolution (0.0015 cm-1) infrared spectrum has been recorded. The rotational structure in the C-type bands for v26 at 1011 cm-1 and v30 at 894 cm-1 has been analyzed. To the 1458 ground state combination differences from these bands, ground state rotational constants were fitted to a Watson-type Hamiltonian to give A0 = 0.8728202(9), B0 = 0.0435868(4), and C0 = 0.0415314(2) cm-1. Upper state rotational constants for the v30 band were also fitted. Predictions of the ground state rotational constants for t-HTE-1-13C1 from a B3LYP/cc-pVTZ model with scale factors based on the normal species were in excellent agreement with observations. Similar good agreement was found between predicted and observed ground state rotational constants for the three 13C1 isotopologues of cis-hexatriene (cHTE), as determined from microwave spectroscopy. Equilibrium rotational constants for tHTE and its three 13C1 isotopologues, of which two were predicted, were used to find a semiexperimental equilibrium structure for the C6 backbone of tHTE. This structure shows increased structural effects of pi-electron delocalization in comparison with butadiene.

  8. Chemical and nanometer-scale structure of kerogen and its change during thermal maturation investigated by advanced solid-state 13C NMR spectroscopy

    USGS Publications Warehouse

    Mao, J.; Fang, X.; Lan, Y.; Schimmelmann, A.; Mastalerz, Maria; Xu, L.; Schmidt-Rohr, K.

    2010-01-01

    We have used advanced and quantitative solid-state nuclear magnetic resonance (NMR) techniques to investigate structural changes in a series of type II kerogen samples from the New Albany Shale across a range of maturity (vitrinite reflectance R0 from 0.29% to 1.27%). Specific functional groups such as CH3, CH2, alkyl CH, aromatic CH, aromatic C-O, and other nonprotonated aromatics, as well as "oil prone" and "gas prone" carbons, have been quantified by 13C NMR; atomic H/C and O/C ratios calculated from the NMR data agree with elemental analysis. Relationships between NMR structural parameters and vitrinite reflectance, a proxy for thermal maturity, were evaluated. The aromatic cluster size is probed in terms of the fraction of aromatic carbons that are protonated (???30%) and the average distance of aromatic C from the nearest protons in long-range H-C dephasing, both of which do not increase much with maturation, in spite of a great increase in aromaticity. The aromatic clusters in the most mature sample consist of ???30 carbons, and of ???20 carbons in the least mature samples. Proof of many links between alkyl chains and aromatic rings is provided by short-range and long-range 1H-13C correlation NMR. The alkyl segments provide most H in the samples; even at a carbon aromaticity of 83%, the fraction of aromatic H is only 38%. While aromaticity increases with thermal maturity, most other NMR structural parameters, including the aromatic C-O fractions, decrease. Aromaticity is confirmed as an excellent NMR structural parameter for assessing thermal maturity. In this series of samples, thermal maturation mostly increases aromaticity by reducing the length of the alkyl chains attached to the aromatic cores, not by pronounced growth of the size of the fused aromatic ring clusters. ?? 2010 Elsevier Ltd. All rights reserved.

  9. Solution Structures of the Prototypical 18 kDa Translocator Protein Ligand, PK 11195, Elucidated with 1H/13C NMR Spectroscopy and Quantum Chemistry

    PubMed Central

    2012-01-01

    Eighteen kilodalton translocator protein (TSPO) is an important target for drug discovery and for clinical molecular imaging of brain and peripheral inflammatory processes. PK 11195 [1a; 1-(2-chlorophenyl)-N-methyl-(1-methylpropyl)-3-isoquinoline carboxamide] is the major prototypical high-affinity ligand for TSPO. Elucidation of the solution structure of 1a is of interest for understanding small-molecule ligand interactions with the lipophilic binding site of TSPO. Dynamic 1H/13C NMR spectroscopy of 1a revealed four quite stable but interconverting rotamers, due to amide bond and 2-chlorophenyl group rotation. These rotamers have been neglected in previous descriptions of the structure of 1a and of the binding of 1a to TSPO. Here, we used quantum chemistry at the level of B3LYP/6-311+G(2d,p) to calculate 13C and 1H chemical shifts for the rotamers of 1a and for the very weak TSPO ligand, N-desmethyl-PK 11195 (1b). These data, plus experimental NMR data, were then used to characterize the structures of rotamers of 1a and 1b in organic solution. Energy barriers for both the amide bond and 2′-chlorophenyl group rotation of 1a were determined from dynamic 1H NMR to be similar (ca.17 to 18 kcal/mol), and they compared well with those calculated at the level of B3LYP/6-31G*. Furthermore, the computed barrier for Z to E rotation is considerably lower in 1a(18.7 kcal/mol) than in 1b (25.4 kcal/mol). NMR (NOE) unequivocally demonstrated that the E rotamer of 1a is the more stable in solution by about 0.4 kcal/mol. These detailed structural findings will aid future TSPO ligand design and support the notion that TSPO prefers to bind ligands as amide E-rotamers. PMID:22860199

  10. Frequency tuning of the optical delay in cesium D{sub 2} line including hyperfine structure

    SciTech Connect

    Anderson, Monte D.; Perram, Glen P.

    2010-03-15

    The frequency dependence of optical delays in both the wings and core of the cesium 6 {sup 2}S{sub 1/2}-6 {sup 2}P{sub 3/2} transition have been observed and modeled with a Voigt line shape convolved with the six hyperfine components. Tunable delays of 0-37 ns are achieved by tuning the laser frequency through resonance at various vapor pressures of 0.15-5.28 mTorr.

  11. Site-specific thermodynamic stability and unfolding of a de novo designed protein structural motif mapped by 13C isotopically edited IR spectroscopy.

    PubMed

    Kubelka, Ginka S; Kubelka, Jan

    2014-04-23

    The mechanism of protein folding remains poorly understood, in part due to limited experimental information available about partially folded states. Isotopically edited infrared (IR) spectroscopy has emerged as a promising method for studying protein structural changes with site-specific resolution, but its full potential to systematically probe folding at multiple protein sites has not yet been realized. We have used (13)C isotopically edited IR spectroscopy to investigate the site-specific thermal unfolding at seven different locations in the de novo designed helix-turn-helix protein αtα. As one of the few stable helix-turn-helix motifs, αtα is an excellent model for studying the roles of secondary and tertiary interactions in folding. Circular dichroism (CD) experiments on the full αtα motif and its two peptide fragments show that interhelical tertiary contacts are critical for stabilization of the secondary structure. The site-specific thermal unfolding probed by (13)C isotopically edited IR is likewise consistent with primarily tertiary stabilization of the local structure. The least thermally stable part of the αtα motif is near the turn where the interhelical contacts are rather loose, while the motif's center with best established core packing has the highest stability. Similar correlation between the local thermal stability and tertiary contacts was found previously for a naturally occurring helix-turn-helix motif. These results underline the importance of native-like tertiary stabilizing interactions in folding, in agreement with recent state-of-the art folding simulations as well as simplified, native-centric models.

  12. Food web structure of the epibenthic and infaunal invertebrates on the Catalan slope (NW Mediterranean): Evidence from δ 13C and δ 15N analysis

    NASA Astrophysics Data System (ADS)

    Fanelli, E.; Papiol, V.; Cartes, J. E.; Rumolo, P.; Brunet, C.; Sprovieri, M.

    2011-01-01

    The food-web structure of the epibenthic and infaunal invertebrates on the continental slope of the Catalan Sea (Balearic basin, NW Mediterranean) was investigated using carbon and nitrogen stable isotopes on a total of 34 species, and HPLC pigment analyses for three key species. Samples were collected close to Barcelona (NE Iberian Peninsula), between 650 and 800 m depth and between February 2007 and February 2008. Mean δ 13C values ranged from -21.0‰ (small Calocaris macandreae and Amphipholis squamata) to -14.5‰ ( Sipunculus norvegicus). Values of δ 15N ranged from 4.0‰ ( A. squamata) to 12.1‰ ( Molpadia musculus). The stable isotope ratios of benthic fauna displayed a continuum of values (e.g. δ 15N range of 8‰), confirming a wide spectrum of feeding strategies (from active suspension feeders to predators) and complex food webs. According to the available information on diets of benthic fauna, the lowest values were found for surface deposit feeders (small C. macandrae and the two ophiuroids A. squamata and Amphiura chiajei) and active suspension feeders ( Abra longicallus and Scalpellum scalpellum) feeding on different sizes of particulate organic matter (POM), among which small particles may exhibit lower δ 15N. High annual mean δ 15N values were found among sub-surface deposit feeders, exploiting refractory or frequently recycled organic matter that is enriched in δ 15N. Carnivorous polychaetes ( Nephtys spp., Oenonidae and Polynoidae) and large decapods ( Geryon longipes and Paromola cuvieri) also displayed high δ 15N values. δ 13C ranges were particularly wide among surface deposit feeders (ranging from -21.0‰ to -16.4‰), suggesting exploitation of POM of both terrigenous and oceanic origins. Correlation between δ 13C and δ 15N was generally weak, indicating multiple carbon sources, likely due to the consumption of different kinds of sinking particles (e.g. marine snow, phytodetritus, etc.), sedimented and frequently recycled POM

  13. Hyperfine-induced hysteretic funnel structure in spin blockaded tunneling current of coupled vertical quantum dots at low magnetic field

    SciTech Connect

    Leary, A.; Wicha, A.; Harack, B.; Coish, W. A.; Hilke, M.; Yu, G.; Gupta, J. A.; Payette, C.; Austing, D. G.

    2013-12-04

    We outline the properties of the hyperfine-induced funnel structure observed in the two-electron spin blockade region of a weakly coupled vertical double quantum dot device. Hysteretic steps in the leakage current occur due to dynamic nuclear polarization when either the bias voltage or the magnetic field is swept up and down. When the bias voltage is swept, an intriguing ∼3 mT wide cusp near 0 T appears in the down-sweep position, and when the magnetic field is swept, the current at 0 T can be switched from 'low' to 'high' as the bias is increased.

  14. New organic single crystal of (benzylthio)acetic acid: Synthesis, crystal structure, spectroscopic (ATR-FTIR, 1H and 13C NMR) and thermal characterization

    NASA Astrophysics Data System (ADS)

    Sienkiewicz-Gromiuk, Justyna; Tarasiuk, Bogdan; Mazur, Liliana

    2016-04-01

    (Benzylthio)acetic acid (Hbta) was synthesized with 78% yield from benzyl chloride and thiourea as substrates. Well-shaped crystals of Hbta were grown by slow solvent evaporation technique from pure methanol. The compound was investigated by single-crystal X-ray and powder diffraction techniques and was also characterized by other analytical methods, like ATR-FTIR, 1H and 13C NMR and TG/DSC. The acid molecule adopts bent conformation in the solid state. The crystal structure of Hbta is stabilized by numerous intermolecular interactions, including O-H···O, C-H···O, C-H···S and C-H···π contacts. Thermal decomposition of the obtained material takes place above 150 °C.

  15. 1H, 13C and 15N resonance assignments and secondary structure analysis of CmPI-II, a serine protease inhibitor isolated from marine snail Cenchritis muricatus.

    PubMed

    Cabrera-Muñoz, Aymara; Rojas, Laritza; Alonso-del-Rivero Antigua, Maday; Pires, José Ricardo

    2016-04-01

    A protease inhibitor (CmPI-II) (UNIPROT: IPK2_CENMR) from the marine mollusc Cenchritis muricatus, has been isolated and characterized. It is the first member of a new group (group 3) of non-classical Kazal-type inhibitors. CmPI-II is a tight-binding inhibitor of serine proteases: trypsin, human neutrophil elastase (HNE), subtilisin A and pancreatic elastase. This specificity is exceptional in the members of Kazal-type inhibitor family. Several models of three-dimensional structure of CmPI-II have been constructed by homology with other inhibitors of the family but its structure has not yet been solved experimentally. Here we report the (1)H, (15)N and (13)C chemical shift assignments of CmPI-II as basis for NMR structure determination and interaction studies. Secondary structure analyses deduced from the NMR chemical shift data have identified three β-strands β1: residues 14-19, β2: 23-35 and β3: 43-45 and one helix α1: 28-37 arranged in the sequential order β1-β2-α1-β3. These secondary structure elements suggest that CmPI-II adopts the typical scaffold of a Kazal-type inhibitor. PMID:26547437

  16. Structural determination of complex natural products by quantum mechanical calculations of (13)C NMR chemical shifts: development of a parameterized protocol for terpenes.

    PubMed

    de Albuquerque, Ana Carolina Ferreira; Ribeiro, Daniel Joras; de Amorim, Mauro Barbosa

    2016-08-01

    Nuclear magnetic resonance (NMR) spectroscopy is one of the most important tools for determining the structures of organic molecules. Despite the advances made in this technique, revisions of erroneously established structures for natural products are still commonly published in the literature. In this context, the prediction of chemical shifts through ab initio and density functional theory (DFT) calculations has become a very powerful tool for assisting with the structural determination of complex organic molecules. In this work, we present the development of a protocol for (13)C chemical shift calculations of terpenes, a class of natural products that are widely distributed among plant species and are very important due to their biological and pharmacological activities. This protocol consists of GIAO-DFT calculations of chemical shifts and the application of a parameterized scaling factor in order to ensure accurate structural determination of this class of natural products. The application of this protocol to a set of five terpenes yielded accurate calculated chemical shifts, showing that this is a very attractive tool for the calculation of complex organic structures such as terpenes. PMID:27424297

  17. New insights into the structure and chemistry of Titan's tholins via 13C and 15N solid state nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Derenne, S.; Coelho, C.; Anquetil, C.; Szopa, C.; Quirico, E.; Bonhomme, C.

    2012-09-01

    Titan, the largest moon of Saturn, is characterized by a dense atmosphere, mainly composed of N2 (ca. 97 %) and CH4 (ca. 2 %). In the upper atmosphere, methane and nitrogen molecules undergo dissociation under the influence of solar UV radiation and electron impacts, followed by recombination reactions leading to a large variety of organic molecules. Some of these compounds form a thick, orange-coloured haze composed of solid organic aerosols that subsequently fall to the surface or remain in suspension in the atmosphere. To gain insight into the chemical composition and structural nature of these complex organic compounds, analogous materials, termed Titan's tholins, are produced in the laboratory, in particular using plasma discharge in gaseous N2 - CH4 mixtures with similar proportions as in Titan's atmosphere. Titan's tholins have been analysed using a wide variety of techniques which provided a wealth of information about potential functional groups and structural building blocks present within the tholin samples. Taken together, the results converge on a structure based on a CxHyNz chemistry that can contain a variety of C-C, C-N, N-H etc single or multiple bonds. It is now necessary to build on that information to refine the chemical and structural models for the Titan's tholins. Here we used solid state NMR techniques to investigate the carbon and nitrogen bonding environments in a 13C- and 15Nenriched sample.

  18. 1H, 15N, and 13C resonance assignments and secondary structure of the SWIRM domain of human BAF155, a chromatin remodeling complex component.

    PubMed

    Moon, Sunjin; Shin, Joon; Lee, Dongju; Seong, Rho H; Lee, Weontae

    2013-10-01

    Mammalian SWI/SNF complexes are evolutionary conserved, ATP-dependent chromatin remodeling units. BAF155 in the SWI/SNF complex contains several highly conserved domains, including SANT, SWIRM, and leucine zipper domains. The biological roles of the SWIRM domain remain unclear; however, both structural and biochemical analyses of this domain have suggested that it could mediate protein-protein or protein-DNA interactions during the chromatin remodeling process. The human BAF155 SWIRM domain was cloned into the Escherichia coli expression vector pMAL-c2X and purified using affinity chromatography for structural analysis. We report the backbone (1)H, (15)N, and (13)C resonance assignments and secondary structure of this domain using nuclear magnetic resonance (NMR) spectroscopy and the TALOS+ program. The secondary structure consists of five α-helices that form a typical histone fold for DNA interactions. Our data suggest that the BAF155 SWIRM domain interacts with nucleosome DNA (Kd = 0.47 μM).

  19. Analysis of the rotational structure in the high-resolution infrared spectrum of trans-hexatriene-1-13C1: a semiexperimental equilibrium structure for the C6 backbone of trans-hexatriene.

    PubMed

    Craig, Norman C; Tian, Hengfeng; Blake, Thomas A

    2012-03-29

    trans-Hexatriene-1-(13)C(1) (tHTE-1-(13)C(1)) has been synthesized, and its high-resolution (0.0015 cm(-1)) infrared spectrum has been recorded. The rotational structure in the C-type bands for ν(26) at 1011 cm(-1) and ν(30) at 894 cm(-1) has been analyzed. To the 1458 ground state combination differences from these bands, ground state rotational constants were fitted to a Watson-type Hamiltonian to give A(0) = 0.8728202(9), B(0) = 0.0435868(4), and C(0) = 0.0415314(2) cm(-1). Upper state rotational constants for the ν(30) band were also fitted. Predictions of the ground state rotational constants for tHTE-1-(13)C(1) from a B3LYP/cc-pVTZ model with scale factors based on the normal species were in excellent agreement with observations. Similar good agreement was found between predicted and observed ground state rotational constants for the three (13)C(1) isotopologues of cis-hexatriene, as determined from microwave spectroscopy. Equilibrium rotational constants for tHTE and its three (13)C(1) isotopologues, of which two were predicted, were used to find a semiexperimental equilibrium structure for the C(6) backbone of tHTE. This structure shows increased structural effects of π-electron delocalization in comparison with butadiene and some differences from the cis isomer of HTE. Structures predicted with the MP2/cc-pVTZ model are also compared.

  20. Multiconfiguration Dirac-Hartree-Fock calculations of excitation energies, oscillator strengths, and hyperfine structure constants for low-lying levels of Sm I

    NASA Astrophysics Data System (ADS)

    Zhou, Fuyang; Qu, Yizhi; Li, Jiguang; Wang, Jianguo

    2015-11-01

    The multiconfiguration Dirac-Hartree-Fock method was employed to calculate the total and excitation energies, oscillator strengths, and hyperfine structure constants for low-lying levels of Sm i. In the first-order perturbation approximation, we systematically analyzed correlation effects from individual electrons and electron pairs. It was found that the core correlations are of importance for the physical quantities concerned. Based on the analysis, the important configuration state wave functions were selected to constitute atomic state wave functions. By using this computational model, our excitation energies, oscillator strengths, and hyperfine structure constants are in better agreement with experimental values than earlier theoretical works.

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

    PubMed

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

    2001-08-01

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

  2. Optimization of {sup 1}H and {sup 13}C NMR methods for structural characterization of acetone and pyridine soluble/insoluble fractions of a coal tar pitch

    SciTech Connect

    Trevor J. Morgan; Anthe George; David B. Davis; Alan A. Herod; Rafael Kandiyoti

    2008-05-15

    {sup 1}H and {sup 13}C high-resolution liquid-state NMR methods were used for the quantitative characterization of different molecular weight fractions of a coal tar pitch (CTP). Three fractions were studied: pitch acetone solubles (PAS), pitch pyridine soluble-acetone insolubles (PPS), and pitch pyridine insolubles (PPI). Standard liquid-state NMR methods were modified and calibrated for use with undeuterated quinoline or undeuterated 1-methyl-2-pyrrolidinone (NMP) as the solvent. This made it possible to calculate the average structural parameters for the higher molecular weight (MW) fractions of the coal tar pitch. Quantitative comparisons of structural differences between the solubility-separated fractions of the pitch are reported. The aromaticity and the average number of aromatic rings per polynuclear aromatic structure were both found to decrease with increasing solubility. Similarly, pericondensed and all other quaternary carbon species were found to decrease with increasing solubility. This suggests that 'continental' type structures become more dominant as the solvent solubility of these coal derived fractions diminishes. The estimated average number of aromatic rings ranged from 1 to 2 rings in the PAS fraction, 4 to 21 rings in the PPS fraction, and 11 to 210 rings in the PPI fraction. These ring-numbers were directly related to the number average molecular mass (M{sub n}) assigned to the particular fraction in the average structural parameter (ASP) calculations. The lower-limit of the M{sub n} values was derived from the ASP calculations as 200, 450, and 6200 u for the PAS, PPS, and PPI fractions, respectively. 66 refs., 7 figs., 15 tabs.

  3. 1H, 13C and 15N resonance assignments and secondary structure analysis of translation initiation factor 1 from Pseudomonas aeruginosa

    PubMed Central

    Bernal, Alejandra; Hu, Yanmei; Palmer, Stephanie O.; Silva, Aaron; Bullard, James; Zhang, Yonghong

    2016-01-01

    Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen and a primary cause of infection in humans. P. aeruginosa can acquire resistance against multiple groups of antimicrobial agents, including β-lactams, aminoglycosides and fluoroquinolones, and multidrug resistance is increasing in this organism which makes treatment of the infections difficult and expensive. This has led to the unmet need for discovery of new compounds distinctly different from present antimicrobials. Protein synthesis is an essential metabolic process and a validated target for the development of new antibiotics. Translation initiation factor 1 from P. aeruginosa (Pa-IF1) is the smallest of the three initiation factors that acts to establish the 30S initiation complex to initiate translation during protein biosynthesis, and its structure is unknown. Here we report the 1H, 13C and 15N chemical shift assignments of Pa-IF1 as the basis for NMR structure determination and interaction studies. Secondary structure analyses deduced from the NMR chemical shift data have identified five β-strands with an unusually extended β-strand at the C-terminal end of the protein and one short α-helix arranged in the sequential order β1–β2–β3–α1–β4–β5. This is further supported by 15N–{1H} hetero NOEs. These secondary structure elements suggest the Pa-IF1 adopts the typical β-barrel structure and is composed of an oligomer-binding motif. PMID:26983940

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

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-01

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

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

    PubMed

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-28

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

  6. Synthesis Of [2h, 13c] And [2h3, 13c]Methyl Aryl Sulfides

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2004-03-30

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2,.sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms. The present invention is also directed to the labeled compounds of [.sup.2 H.sub.1, .sup.13 C]methyl iodide and [.sup.2 H.sub.2, .sup.13 C]methyl iodide.

  7. Where Millimeter Wave Spectra are Sensitive to Small Electric Fields: High Rydberg States of Xenon and Their Hyperfine Structures

    NASA Astrophysics Data System (ADS)

    Schäfer, Martin; Raunhardt, Matthias; Merkt, Frédéric

    2009-06-01

    In the range 0-45 cm^{-1} below the ionization limit, the separation between adjacent electronic states (Rydberg states with principal quantum number n>50) of atoms and molecules is smaller than 2 cm^{-1}. In order to resolve the fine or hyperfine structure of these states, it is necessary to combine high-resolution vacuum ultraviolet (VUV) laser radiation, which is required to access the Rydberg states from the ground state, with millimeter wave radiation. Such double-resonance experiments have been used to study the hyperfine structure of high Rydberg states of ^{83}Kr, H_2 or D_2. Millimeter wave transitions (240-350 GHz) between nℓ (52≤ n≤64, ℓ≤3) Rydberg states of different xenon isotopes were detected by pulsed field ionization followed by mass-selective detection of the cations. Because of the high polarizability of high-n Rydberg states (∝ n^7, ˜10^4 MHz cm^{2} V^{-2} for n≈ 50), it is necessary to reduce the electric stray fields to values of the order of mV/cm (or less) in order to minimize the (quadratic) Stark shift of the millimeter wave transitions. Some p and d Rydberg states of Xe are nearly degenerate and efficiently mixed by small stray fields, making it possible to observe transitions forbidden by the Δℓ=±1 selection rule or transitions exhibiting a linear Stark effect, which is typical for the degenerate high-ℓ Rydberg states. Multichannel quantum defect theory (MQDT) was used to analyze the millimeter wave data and to determine the hyperfine structures of the ^2P_{3/2} ground electronic states of ^{129}Xe^+ and ^{131}Xe^+. C. Fabre, P. Goy, S. Haroche, J. Phys. B: Atom. Mol. Phys. 10, L183-189 (1977). F. Merkt, A. Osterwalder, Int. Rev. Phys. Chem. 21, 385-403 (2002). M. Schäfer, M. Andrist, H. Schmutz, F. Lewen, G. Winnewisser, F. Merkt, J. Phys. B: At. Mol. Opt. Phys. 39, 831-845 (2006) M. Schäfer, F. Merkt, Phys. Rev. A, 74, 062506 (2006). A. Osterwalder, A. Wüest, F. Merkt, Ch. Jungen, J. Chem. Phys., 121, 11810

  8. Crystal structure and theoretical study of IR and 1H and 13C NMR spectra of cordatin, a natural product with antiulcerogenic activity

    NASA Astrophysics Data System (ADS)

    Brasil, Davi S. B.; Alves, Cláudio N.; Guilhon, Giselle M. S. P.; Muller, Adolfo H.; Secco, Ricardo De S.; Peris, Gabriel; Llusar, Rosa

    Cordatin is a furan diterpenoid with a clerodane skeleton isolated from Croton palanostigma Klotzsch (Euphorbiaceae). This natural product shows significant antiulcerogenic activity, similar to cimetidine (Tagamet®), a compound used for the treatment of peptic ulcers. The crystal structure of cordatin was obtained by X-ray diffraction and its geometrical parameters were compared with theoretical calculations at the B3LYP theory level. The IR and NMR (1H and 13C chemical shifts and coupling constants) spectra were obtained and compared with the theoretical calculations. The B3LYP theory level, with the 6-31G(d,p) and 6-311G(d,p) basis set, provided IR absorption values close to the experimental data. Moreover, theoretical NMR parameters obtained in both gas phase and chloroform solvent at the B3PW91/DGDZVP, B3LYP/6-311+G(2d,p), and B3PW91/6-311+G(2d,p) levels showed good correlations with the experimental results.

  9. Syntheses, structures, and 1H, 13C{1H} and 119Sn{1H} NMR chemical shifts of a family of trimethyltin alkoxide, amide, halide and cyclopentadienyl compounds

    DOE PAGES

    Lichtscheidl, Alejandro G.; Janicke, Michael T.; Scott, Brian L.; Nelson, Andrew T.; Kiplinger, Jaqueline L.

    2015-08-21

    The synthesis and full characterization, including Nuclear Magnetic Resonance (NMR) data (1H, 13C{1H} and 119Sn{1H}), for a series of Me3SnX (X = O-2,6-tBu2C6H3 (1), (Me3Sn)N(2,6-iPr2C6H3) (3), NH-2,4,6-tBu3C6H2 (4), N(SiMe3)2 (5), NEt2, C5Me5 (6), Cl, Br, I, and SnMe3) compounds in benzene-d6, toluene-d8, dichloromethane-d2, chloroform-d1, acetonitrile-d3, and tetrahydrofuran-d8 are reported. The X-ray crystal structures of Me3Sn(O-2,6-tBu2C6H3) (1), Me3Sn(O-2,6-iPr2C6H3) (2), and (Me3Sn)(NH-2,4,6-tBu3C6H2) (4) are also presented. As a result, these compiled data complement existing literature data and ease the characterization of these compounds by routine NMR experiments.

  10. Spatial and temporal dynamics of size-structured photosynthetic parameters (PAM) and primary production (13C) of pico- and nano-phytoplankton in an atoll lagoon.

    PubMed

    Lefebvre, Sébastien; Claquin, Pascal; Orvain, Francis; Véron, Benoît; Charpy, Loïc

    2012-01-01

    Atoll lagoons display a high diversity of trophic states due mainly to their specific geomorphology, and probably to their level and mode of human exploitation. We investigated the functioning of the Ahe atoll lagoon, utilized for pearl oyster farming, through estimations of photosynthetic parameters (pulse amplitude modulation fluorometry) and primary production ((13)C incorporation) measurements of the size structured phytoplankton biomass (<2 μm and >2 μm). Spatial and temporal scales of variability were surveyed during four seasons, over 16 months, at four sites within the lagoon. While primary production (P) was dominated by the picophytoplankton, its biomass specific primary productivity (P(B)) was lower than in other atoll lagoons. The variables size fraction of the phytoplankton, water temperature, season, the interaction term station*fraction and site, explained significantly the variance of the data set using redundancy analysis. No significant trends over depth were observed in the range of 0-20 m. A clear spatial pattern was found which was persistent over the seasons: south and north sites were different from the two central stations for most of the measured variables. This pattern could possibly be explained by the existence of water cells showing different water residence time within the lagoon. Photoacclimation strategies of the two size fractions differed through their light saturation coefficient (higher for picophytoplankton), but not through their maximum photosynthetic capacity (ETR(max)). Positive linear relationships between photosynthetic parameters indicated that their dynamic was independent of light availability in this ecosystem, but most probably dependent on nutrient availability and/or rapid changes in the community structure. Spatial and temporal patterns of the measured processes are then further discussed in the context of nutrient availability and the possible role of cultured oysters in nutrient recycling. PMID:22640918

  11. Nuclear Hyperfine Structure in the Donor – Acceptor Complexes (CH3)3N-BF3 and (CH)33N-B(CH3)3

    EPA Science Inventory

    The donor-acceptor complexes (CH3)3N-BF3 and (CH3)3N-B(CH3)3 have been reinvestigated at high resolution by rotational spectroscopy in a supersonic jet. Nuclear hyperfine structure resulting from both nitrogen and boron has been resolved and quadrupole coupling constants have bee...

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

    USGS Publications Warehouse

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

    2011-01-01

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

  13. Design and operation of a continuous 13C and 15N labeling chamber for uniform or differential, metabolic and structural, plant tissue isotope labeling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tracing heavy stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes and soil organic matter formation to small-scale stable-isotope biomarker probing. Coupling multiple stable isotopes such as 13C with 15N, 18O o...

  14. A Discovery-Based Hydrochlorination of Carvone Utilizing a Guided-Inquiry Approach to Determine the Product Structure from [superscript 13]C NMR Spectra

    ERIC Educational Resources Information Center

    Pelter, Michael W.; Walker, Natalie M.

    2012-01-01

    This experiment describes a discovery-based method for the regio- and stereoselective hydrochlorination of carvone, appropriate for a 3-h second-semester organic chemistry laboratory. The product is identified through interpretation of the [superscript 13]C NMR and DEPT spectra are obtained on an Anasazi EFT-60 at 15 MHz as neat samples. A…

  15. Shifts in Ross Sea food web structure as indicated by δ15N and δ13C values of fossil Antarctic seals

    NASA Astrophysics Data System (ADS)

    Leopold, A.; Brault, E.; McMahon, K.

    2013-12-01

    As climate change continues to mount, there is a growing need for understanding its effects on biological-physical interactions of marine ecosystems. Assessing the effects of anthropogenic activities on the coastal marine ecosystem involves understanding the underlying mechanisms driving these changes as well as establishing baselines of the natural system. Preliminary findings have indicated shifts in bulk carbon (C) and nitrogen (N) isotopic values of southern elephant seal (Mirounga leonina) samples, collected in the Dry Valleys of Antarctica in the Ross Sea region, over approximately the last 7,000 years. These shifts could result from 1) seals changing their foraging location and/or diet over this time, 2) climate change-induced shifts in the biogeochemistry at the base of the food web, or 3) some combination of both processes. We explored the patterns of long-term change in Ross Sea food web structure by examining the stable isotope values of three top predators in this system, Weddell seals (Leptonychotes weddellii), leopard seals (Hydrurga leptonyx), and crabeater seals (Lobodon carcinophagus). Fossil seal samples were collected in the Dry Valleys during the austral summer of 2012/13 and then analyzed for bulk C and N isotopes via an elemental analyzer/isotope-ratio mass spectrometer (EA/IRMS). Our initial findings indicate that C isotopic values of fossil seal samples from Weddell, leopard, and crabeater seals were more enriched than isotopic values of modern seals of the same species (e.g., δ13C = -22.79 × 0.92 ‰ and -26.71 × 0.50 ‰ for fossil and modern crabeater seals, respectively). Given the relatively consistent diet of crabeater seals, these findings suggest a shift in baseline food web structure occurred over the last 10,000 years, either through changes in foraging location or local shifts in biogeochemistry. For all species, N isotopic values are widely variable (e.g., 7.28 to 16.0 δ15N ‰ for the Weddell seal), which may be a result of

  16. Precision Measurement of the Hyperfine Structure of Laser-Cooled Radioactive {sup 7}Be{sup +} Ions Produced by Projectile Fragmentation

    SciTech Connect

    Okada, K.; Wada, M.; Nakamura, T.; Takamine, A.; Schury, P.; Ishida, Y.; Sonoda, T.; Kanai, Y.; Kojima, T. M.; Lioubimov, V.; Ogawa, M.; Yamazaki, Y.; Yoshida, A.; Kubo, T.; Katayama, I.; Ohtani, S.; Wollnik, H.; Schuessler, H. A.

    2008-11-21

    The ground state hyperfine splitting of {sup 7}Be{sup +} has been measured by laser-microwave double-resonance spectroscopy in the online rf trap of RIKEN's slow RI-beam facility. Be ions produced by projectile fragmentation of {sup 13}C at {approx_equal}1 GeV were thermalized in a rf ion guide gas cell and subsequently laser cooled in the ion trap to {approx_equal}1 {mu}eV. This 10{sup 15}-fold reduction of the kinetic energy allows precision spectroscopy of these ions. A magnetic hfs constant of A=-742.772 28(43) MHz was measured for {sup 7}Be{sup +}, from which a nuclear magnetic moment of {mu}{sub I}=-1.399 28(2){mu}{sub N} was deduced.

  17. Acid-base interactions and secondary structures of poly-L-lysine probed by 15N and 13C solid state NMR and Ab initio model calculations.

    PubMed

    Dos, Alexandra; Schimming, Volkmar; Tosoni, Sergio; Limbach, Hans-Heinrich

    2008-12-11

    The interactions of the 15N-labeled amino groups of dry solid poly-L-lysine (PLL) with various halogen and oxygen acids HX and the relation to the secondary structure have been studied using solid-state 15N and 13C CPMAS NMR spectroscopy (CP = cross polarization and MAS = magic angle spinning). For comparison, 15N NMR spectra of an aqueous solution of PLL were measured as a function of pH. In order to understand the effects of protonation and hydration on the 15N chemical shifts of the amino groups, DFT and chemical shielding calculations were performed on isolated methylamine-acid complexes and on periodic halide clusters of the type (CH3NH3(+)X(-))n. The combined experimental and computational results reveal low-field shifts of the amino nitrogens upon interaction with the oxygen acids HX = HF, H2SO4, CH3COOH, (CH3)2POOH, H3PO4, HNO3, and internal carbamic acid formed by reaction of the amino groups with gaseous CO2. Evidence is obtained that only hydrogen-bonded species of the type (Lys-NH2***H-X)n are formed in the absence of water. 15N chemical shifts are maximum when H is located in the hydrogen bond center and then decrease again upon full protonation, as found for aqueous solution at low pH. By contrast, halogen acids interact in a different way. They form internal salts of the type (Lys-NH3(+)X(-))n via the interaction of many acid-base pairs. This salt formation is possible only in the beta-sheet conformation. By contrast, the formation of hydrogen-bonded complexes can occur both in beta-sheet domains as well as in alpha-helical domains. The 15N chemical shifts of the protonated ammonium groups increase when the size of the interacting halogen anions is increased from chloride to iodide and when the number of the interacting anions is increased. Thus, the observed high-field 15N shift of ammonium groups upon hydration is the consequence of replacing interacting halogen atoms by oxygen atoms.

  18. S100A13-C2A binary complex structure-a key component in the acidic fibroblast growth factor for the non-classical pathway

    SciTech Connect

    Mohan, Sepuru K.; Rani, Sandhya G.; Kumar, Sriramoju M.; Yu Chin

    2009-03-13

    pathway, we have studied the interactions of S100A13 with C2A by {sup 1}H-{sup 15}N HSQC titration and 3D-filtered NOESY experiments. We characterized the binary complex structure of S100A13-C2A by using a variety of multi-dimensional NMR experiments. This complex acts as a template for FGF-1 dimerization and multiprotein complex formation.

  19. Structure and equilibria of Ca 2+-complexes of glucose and sorbitol from multinuclear ( 1H, 13C and 43Ca) NMR measurements supplemented with molecular modelling calculations

    NASA Astrophysics Data System (ADS)

    Pallagi, A.; Dudás, Cs.; Csendes, Z.; Forgó, P.; Pálinkó, I.; Sipos, P.

    2011-05-01

    Ca 2+-complexation of D-glucose and D-sorbitol have been investigated with the aid of multinuclear ( 1H, 13C and 43Ca) NMR spectroscopy and ab initio quantum chemical calculations. Formation constants of the forming 1:1 complexes have been estimated from one-dimensional 13C NMR spectra obtained at constant ionic strength (1 M NaCl). Binding sites were identified from 2D 1H- 43Ca NMR spectra. 2D NMR measurements and ab initio calculations indicated that Ca 2+ ions were bound in a tridentate manner via the glycosidic OH, the ethereal oxygen in the ring and the OH on the terminal carbon for the α- and β-anomers of glucose and for sorbitol simultaneous binding of four hydroxide moieties (C1, C2, C4 and C6) was suggested.

  20. Carbon flow and trophic structure of an Antarctic coastal benthic community as determined by δ 13C and δ 15N

    NASA Astrophysics Data System (ADS)

    Gillies, C. L.; Stark, J. S.; Johnstone, G. J.; Smith, S. D. A.

    2012-01-01

    Stable isotopes of carbon and nitrogen were used to determine the different carbon pathways and trophic assemblages amongst coastal benthic fauna of the Windmill Islands, East Antarctica. Macroalgae, pelagic POM, sediment POM and sea ice POM had well-separated δ 13C signatures, which ranged from -36.75‰ for the red alga Phyllophora antarctica, to -10.35‰ for sea ice POM. Consumers were also well separated by δ 13C, ranging from -21.42‰ for the holothurian Staurocucumis sp. up to -7.47‰ for the urchin Sterechinus neumayeri. Analysis of δ 13C and δ 15N revealed distinct groups for suspension feeders, grazer/herbivores and deposit feeders, whilst predators and predator/scavengers showed less grouping. Consumers spanned a δ 15N range of 8.71‰, equivalent to four trophic levels, although δ 15N ratios amongst consumers were continuous, rather than grouped into discrete trophic levels. The study has built a trophic model for the Windmill Islands and summarises three main carbon pathways utilised by the benthos: (1) pelagic POM; (2) macroalgae/epiphytic/benthic diatoms and (3) sediment POM/benthic diatoms. The movement of carbon within the coastal benthic community of the Windmill Islands is considered complex, and stable isotopes of carbon and nitrogen were valuable tools in determining specific feeding guilds and in tracing carbon flow, particularly amongst lower-order consumers.

  1. The rotational spectrum of the CCP (X 2Pi(r)) radical and its 13C isotopologues at microwave, millimeter, and submillimeter wavelengths.

    PubMed

    Halfen, D T; Sun, M; Clouthier, D J; Ziurys, L M

    2009-01-01

    The pure rotational spectrum of CCP (X (2)Pi(r)) has been measured at microwave, millimeter, and submillimeter wavelengths (17-545 GHz), along with its (13)C isotopologues ((13)C(13)CP, C(13)CP, and (13)CCP). The spectra of these species were recorded using a combination of millimeter/submillimeter direct absorption methods and Fourier transform microwave (FTMW) techniques. The phosphorus dicarbides were created in the gas phase from the reaction of red phosphorus and acetylene or methane in argon in an ac discharge for the direct absorption experiments, and using PCl(3) as the phosphorus source in a pulsed dc nozzle discharge for the FTMW measurements. A total of 35 rotational transitions were recorded for the main isotopologue, and between 2 and 8 for the (13)C-substituted species. Both spin-orbit components were identified for CCP, while only the Omega = 12 ladder was observed for (13)C(13)CP, C(13)CP, and (13)CCP. Hyperfine splittings due to phosphorus were observed for each species, as well as carbon-13 hyperfine structure for each of the (13)C-substituted isotopologues. The data were fitted with a Hund's case (a) Hamiltonian, and rotational, fine structure, and hyperfine parameters were determined for each species. The r(m)(1) bond lengths established for CCP, r(C-C) = 1.289(1) A and r(C-P) = 1.621(1) A, imply that there are double bonds between both the two carbon atoms and the carbon and phosphorus atoms. The hyperfine constants suggest that the unpaired electron in this radical is primarily located on the phosphorus nucleus, but with some electron density also on the terminal carbon atom. There appears to be a minor resonance structure where the unpaired electron is on the nucleus of the end carbon. The multiple double bond structure forces the molecule to be linear, as opposed to other main group dicarbides, such as SiC(2), which have cyclic geometries.

  2. 13 C solid-state NMR study of the 13 C-labeled peptide, (E)8 GGLGGQGAG(A)6 GGAGQGGYGG as a model for the local structure of Nephila clavipes dragline silk (MaSp1) before and after spinning.

    PubMed

    Yazawa, Koji; Yamaguchi, Erika; Knight, David; Asakura, Tetsuo

    2012-06-01

    We prepared the water soluble model peptide, (E)(8) GGLGGQGAG(A)(6) GGAGQGGYGG, to throw light on the local structure of spidroin 1 (MaSpl) protein in spider dragline silk of Nephila clavipes before and after spinning. Solution (13) C NMR showed that the conformation of the peptide in aqueous solution was essentially random coil. Solid-state NMR was used to follow conformation-dependent (13) C chemical shifts in (13) C selectively labeled versions of the peptide. The peptide lyophilized from an aqueous solution at neutral pH (hereafter referred to as "without acid treatment)"was used to mimic the state of the spidroin stored in the spider's silk gland while the peptide precipitated from the acidic solution ("with acid treatment") was used to simulate the role of acid treatment in inducing conformation change in the natural spinning process. In without acid treatment, the fraction of random coil conformation was lowest in the N-terminal region (residues 15-18) when compared with the C-terminus. The conformational change produced by the acid treatment occurred in the sequence, G(15) AG(A)(6) GGAG(27), interposed between pairs of Gly residues pairs, Gly(12,13), and Gly(29,30). The acid treated peptide showed a remarkable decrease in the fraction of random coil conformation from A(20) to A(23) in the poly-Ala region when compared with the peptide without acid treatment. These observations taken together suggest that the peptide can be used as a model for studying the localization of the conformation change in spider silk fibroin in the natural spinning and the role of acid treatment in this process.

  3. sup 13 C-enriched ribonucleosides: Synthesis and application of sup 13 C- sup 1 H and sup 13 C- sup 13 C spin-coupling constants to assess furanose and N-glycoside bond conformations

    SciTech Connect

    Kline, P.C.; Serianni, A.S. )

    1990-09-26

    Adenosine (1), cytidine (2), guanosine (3), and uridine (4) have been prepared chemically with {sup 13}C enrichment (99 atom %) at C1{prime} and C2{prime} of the ribose ring. Reliable synthetic protocols have been developed to permit access to millimole quantities of labeled ribonucleosides required for structural studies of stable isotopically labeled oligonucleotides and for in vivo metabolism studies. High-resolution {sup 1}H and {sup 13}C NMR spectra of the enriched ribonucleosides have been obtained, and {sup 13}C-{sup 13}C and {sup 13}C-{sup 1}H spin-coupling constants have been measured for pathways within the {beta}-D-ribofuranose ring and across the N-glycoside bond. Related couplings were determined in methyl {alpha}- and {beta}-D-riboruanosides (5,6), and in two conformationally constrained nucleosides, 2,2{prime}-anhydro-(1-{beta}-D-arabinofuranosyl)uracil (7) and 2{prime},3{prime}-O-isopropylidene-2,5{prime}-O-cyclouridine (8). The latter data were used to construct a crude Karplus curve for the {sup 13}C-C-N-{sup 13}C coupling pathway across the N-glycoside bond in 1-4. {sup 1}H-{sup 1}H, {sup 13}C-{sup 1}H, and {sup 13}C-{sup 13}C coupling data are used to evaluate current models describing the conformational dynamics of 1-4 in aqueous solution.

  4. Introducing NMR to a General Chemistry Audience: A Structural-Based Instrumental Laboratory Relating Lewis Structures, Molecular Models, and [superscript 13]C NMR Data

    ERIC Educational Resources Information Center

    Pulliam, Curtis R.; Pfeiffer, William F.; Thomas, Alyssa C.

    2015-01-01

    This paper describes a first-year general chemistry laboratory that uses NMR spectroscopy and model building to emphasize molecular shape and structure. It is appropriate for either a traditional or an atoms-first curriculum. Students learn the basis of structure and the use of NMR data through a cooperative learning hands-on laboratory…

  5. 13C CPMAS NMR study of the structure of p- t-butylcalix[4]arene-alkylbenzene clathrates in the solid state

    NASA Astrophysics Data System (ADS)

    Yamanobe, Takeshi; Nakamura, Ichinari; Hibino, Kazunobu; Komoto, Ta-i.; Kurosu, Hiromichi; Ando, Isao; Nakamoto, Yoshiaki; Ishida, Shin-ichiro

    1995-08-01

    The NMR chemical shifts measured by the 13C CPMAS method for clathrates of p- t-butylcalix[4]arenes including mobile alkylbenzenes in the solid state revealed that the alkyl groups of the guest molecules are located in the cavity of p- t-butylcalix[4]arene, depending on the size of the alkyl group. It was found that n-alkylbenzenes are easily incorporated into p- t-butylcalix[4]arene in the order of toluene > ethylbenzene ⩾ n-propylbenzene. For isopropylbenzene, the bulky isopropyl group prevents incorporation into the cavity of the host molecule.

  6. Hyperfine structure of the 4{f}^{8}5{d}^{2}6s configuration in the Tb atom

    NASA Astrophysics Data System (ADS)

    Furmann, B.; Stefanska, D.; Krzykowski, A.

    2016-01-01

    Within this work new experimental results concerning the hyperfine structure (hfs) in the terbium atom are presented. Hfs constants A and B for eight levels belonging to the even-parity configuration 4{f}85{d}26s were determined, based on the results of measurements performed using the laser-induced fluorescence method in a hollow cathode discharge at 18 spectral lines. The configuration 4{f}85{d}26s in the terbium atom was hitherto very scarcely investigated; for seven of the levels examined within this work results concerning the hfs were obtained for the first time. As a by-product, hfs constants for 12 odd-parity levels, involved as upper levels in the transitions investigated, were also determined. A preliminary attempt at a semi-empirical analysis of Tb I hfs on a multi-configuration basis, based on the results of this work, yielded a value of the one-electron {a}6s10 parameter as well as the respective radial integral {< {r}-3> }6s10, which can be compared with the values along the lanthanide elements series reported in the literature. More conclusive results can certainly be obtained once the experimental database for Tb I becomes more extensive.

  7. Energy, fine structure, hyperfine structure, and radiative transition rates of the high-lying multi-excited states for B-like neon

    NASA Astrophysics Data System (ADS)

    Zhang, Chun Mei; Chen, Chao; Sun, Yan; Gou, Bing Cong; Shao, Bin

    2015-04-01

    The Rayleigh-Ritz variational method with multiconfiguration interaction wave functions is used to obtain the energies of high-lying multi-excited quartet states 1 s 22 s2 pnl and 1 s 22 p 2 nl 4Pe,o ( n ≥ 2) in B-like neon, including the mass polarization and relativistic corrections. The fine structure and hyperfine structure of the excited quartet states for this system are investigated. Configuration structures of the high-lying multi-excited series are further identified by relativistic corrections and fine structure splittings. The transition rates and wavelengths are also calculated. Calculated wavelengths include the quantum electrodynamic effects. The results are compared with other theoretical and experimental data in the literature.

  8. Spin--rotation and hyperfine structure in the X sup 2. Sigma. sup + state of yttrium monosulfide by molecular-beam laser-radio-frequency double resonance

    SciTech Connect

    Azuma, Y.; Childs, W.J. )

    1990-12-15

    The molecular-beam laser-radio-frequency double-resonance method has been used to measure the spin--rotation and magnetic hyperfine structure of yttrium monosulfide (YS) in its {ital X} {sup 2}{Sigma}{sup +} electronic ground state. The spin--rotation constant {gamma} is found to be positive, unlike that of YO. The Fermi contact and dipolar hyperfine interactions (due to the spin {ital I}=1/2 of {sup 89}Y) are found to be rather close to the corresponding quantities in YO. The contact hfs constant {ital b} in the excited {ital B} {sup 2}{Sigma}{sup +} state of YS was determined by combining the directly measured {ital X} {sup 2}{Sigma}{sup +} splitting information with {ital B}--{ital X} optical hfs observations.

  9. sup 15 N and sup 13 C NMR studies of ligands bound to the 280,000-dalton protein porphobilinogen synthase elucidate the structures of enzyme-bound product and a Schiff base intermediate

    SciTech Connect

    Jaffe, E.K.; Rajagopalan, J.S. ); Markham, G.D. )

    1990-09-11

    Porphobilinogen synthase (PBGS) catalyzes the asymmetric condensation of two molecules of 5-aminolevulinic acid (ALA). Despite the 280,000-dalton size of PBGS, much can be learned about the reaction mechanism through {sup 13}C and {sup 15}N NMR. The authors knowledge, these studies represent the largest protein complex for which individual nuclei have been characterized by {sup 13}C or {sup 15}N NMR. Here they extend their {sup 13}C NMR studies to PBGS complexes with (3,3-{sup 2}H{sub 2},3-{sup 13}C)ALA and report {sup 15}N NMR studies of ({sup 15}N)ALA bound to PBGS. As in their previous {sup 13}C NMR studies, observation of enzyme-bound {sup 15}N-labeled species was facilitated by deuteration at nitrogens that are attached to slowly exchanging hydrogens. For holo-PBGS at neutral pH, the NMR spectra reflect the structure of the enzyme-bound product porphobilinogen (PBG), whose chemical shifts are uniformly consistent with deprotonation of the amino group whose solution pK{sub a} is 11. Despite this local environment, the protons of the amino group are in rapid exchange with solvent. For methyl methanethiosulfonate (MMTS) modified PBGS, the NMR spectra reflect the chemistry of an enzyme-bound Schiff base intermediate that is formed between C{sub 4} of ALA and an active-site lysine. The {sup 13}C chemical shift of (3,3-{sup 2}H{sub 2},3-{sup 13}C)ALA confirms that the Schiff base is an imine of E stereochemistry. By comparison to model imines formed between ({sup 15}N)ALA and hydrazine or hydroxylamine, the {sup 15}N chemical shift of the enzyme-bound Schiff base suggests that the free amino group is an environment resembling partial deprotonation. Deprotonation of the amino group would facilitate formation of a Schiff base between the amino group of the enzyme-bound Schiff base and C{sub 4} of the second ALA substrate. This is the first evidence supporting carbon-nitrogen bond formation as the initial site of interaction between the two substrate molecules.

  10. Distinguishing tautomerism in the crystal structure of (Z)-N-(5-ethyl-2,3-di-hydro-1,3,4-thiadiazol-2-ylidene) -4-methylbenzenesulfonamide using DFT-D calculations and {sup 13}C solid-state NMR

    SciTech Connect

    Li, Xiaozhou; Bond, Andrew D.; Johansson, Kristoffer E.; Van de Streek, Jacco

    2014-08-01

    The crystal structure of (Z)-N-(5-ethyl-2,3-di-hydro-1,3,4-thiadiazol-2-ylidene) -4-methylbenzenesulfonamide contains an imine tautomer, rather than the previously reported amine tautomer. The tautomers can be distinguished using dispersion-corrected density functional theory calculations and by comparison of calculated and measured {sup 13}C solid-state NMR spectra. The crystal structure of the title compound, C{sub 11}H{sub 13}N{sub 3}O{sub 2}S{sub 2}, has been determined previously on the basis of refinement against laboratory powder X-ray diffraction (PXRD) data, supported by comparison of measured and calculated {sup 13}C solid-state NMR spectra [Hangan et al. (2010 ▶). Acta Cryst. B66, 615–621]. The mol@@ecule is tautomeric, and was reported as an amine tautomer [systematic name: N-(5-ethyl-1,3,4-thia@@diazol-2-yl)-p-toluene@@sulfonamide], rather than the correct imine tautomer. The protonation site on the mol@@ecule’s 1,3,4-thia@@diazole ring is indicated by the inter@@molecular contacts in the crystal structure: N—H⋯O hydrogen bonds are established at the correct site, while the alternative protonation site does not establish any notable inter molecular inter@@actions. The two tautomers provide essentially identical Rietveld fits to laboratory PXRD data, and therefore they cannot be directly distinguished in this way. However, the correct tautomer can be distinguished from the incorrect one by previously reported qu@@anti@@tative criteria based on the extent of structural distortion on optimization of the crystal structure using dispersion-corrected density functional theory (DFT-D) calculations. Calculation of the {sup 13}C SS-NMR spectrum based on the correct imine tautomer also provides considerably better agreement with the measured {sup 13}C SS-NMR spectrum.

  11. The hyperfine structure in the rotational spectra of D2(17)O and HD(17)O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen.

    PubMed

    Puzzarini, Cristina; Cazzoli, Gabriele; Harding, Michael E; Vázquez, Juana; Gauss, Jürgen

    2015-03-28

    Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing (17)O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined (17)O spin-rotation constants of D2 (17)O and HD(17)O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H2 (17)O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)].

  12. Molecular organization in the native state of woody tissue: Studies of tertiary structure using the Raman microprobe Solid State [sup 13]C NMR and biomimetic tertiary aggregates

    SciTech Connect

    Atalla, R.H.

    1992-01-01

    A number of new approaches to the study of native wood tissue complementary to our earlier Raman spectroscopy including solid state [sup 13]C NMR and X-ray diffractometry. A wide variety of native cellulosic tissues were examined which led to the generation of biomimetic tertiary aggregates which simulate states of aggregation characteristic of cell walls. We have also explored charge transport characteristics of lignified tissue. Our Raman spectroscopic studies have advanced our understanding of key spectral features and confirmed the variability of the patterns of orientation of lignin reported earlier. A major effort was dedicated to assessing the contributions of electronic factors such as conjugation and the resonance Raman effect to enhancement of the spectra features associated with lignin. We have now established a solid foundation for spectral mapping of different regions in cell walls.

  13. Calculation of vibrational branching ratios and hyperfine structure of 24Mg19F and its suitability for laser cooling and magneto-optical trapping

    NASA Astrophysics Data System (ADS)

    Xu, Liang; Yin, Yanning; Wei, Bin; Xia, Yong; Yin, Jianping

    2016-01-01

    More recently, laser cooling of the diatomic radical magnesium monofluoride (24Mg19F ) is being experimentally preformed [Appl. Phys. Express 8, 092701 (2015), 10.7567/APEX.8.092701 and Opt. Express 22, 28645 (2014), 10.1364/OE.22.028645] and was also studied theoretically [Phys. Rev. A 91, 042511 (2015), 10.1103/PhysRevA.91.042511]. However, some important problems still remain unsolved, so, in our paper, we perform further theoretical study for the feasibility of laser cooling and trapping the 24Mg19F molecule. At first, the highly diagonal Franck-Condon factors of the main transitions are verified by the closed-form approximation, Morse approximation, and Rydberg-Klein-Rees inversion methods, respectively. Afterwards, we investigate the lower X 2Σ1/2 + hyperfine manifolds using a quantum effective Hamiltonian approach and obtain the zero-field hyperfine spectrum with an accuracy of less than 30 kHz ˜5 μ K compared with the experimental results, and then find out that one cooling beam and one or two repumping beams with their first-order sidebands are enough to implement an efficient laser slowing and cooling of 24Mg19F . Meanwhile, we also calculate the accurate hyperfine structure magnetic g factors of the rotational state (X 2Σ1/2 +,N =1 ) and briefly discuss the influence of the external fields on the hyperfine structure of 24Mg19F as well as its possibility of preparing three-dimensional magneto-optical trapping. Finally we give an explanation for the difference between the Stark and Zeeman effects from the perspective of parity and time reversal symmetry. Our study shows that, besides appropriate excitation wavelengths, the short lifetime for the first excited state A 2Π1 /2 , and lighter mass, the 24Mg19F radical could be a good candidate molecule amenable to laser cooling and magneto-optical trapping.

  14. A Initio Mr-Rci Calculations of ((n - 1)D + Ns)(n) Atomic Bound States: Application to Hyperfine Structure and Electron Affinity Studies.

    NASA Astrophysics Data System (ADS)

    Datta, Debasis

    Systematic inclusion of many-body effects in open d and f subshell atoms has long been known as a formidable challenge in atomic structure theory. Due to the presence of competing relativistic effects in such systems, an appropriate theoretical approach needs to incorporate electron correlation within the framework of the Special Theory of Relativity. To this aim, the Relativistic Configuration Interaction methodology as developed by Beck and others has been extended and applied to multi-reference situations in ((n - 1)d + ns) ^{rm N} type valence configurations. Specific focus has been on the hyperfine structure and electron affinity studies of the transition metal ions and the rare earths respectively. Energies and magnetic dipole and electric quadrupole hyperfine structure constants of all the fifteen Zr II (4d + 5s)^3 J = 0.5, 1.5 levels and the twenty one Nb II (4d + 5s)^4 J = 2 levels have been determined with unprecedented accuracies. The average errors in energy are 0.087 eV and 0.050 eV for Zr II J = 3/2 & 1/2 respectively while that for the ten bottom levels of Nb II J = 2 is 0.055 eV. For the levels known experimentally, the corresponding errors in magnetic dipole hyperfine structure constants are 9.2%, 31.8% and 3.8%. Quite a few of the many-body hyperfine constant values exhibit striking improvements over the Multi-Configurational Dirac Fock values. A new value of nuclear quadrupole moment has also been predicted for Zr II. In all cases certain previous level assignments have been corrected and five previously unknown levels have been identified in Nb II. The rigorous systematics of the many-body effects important for the energy level and hyperfine structure of these systems has been presented including core-valence and core-core effects. Contrary to the conventional wisdom and theoretical predictions of the last decade, the attachment of an f electron has been discarded as the most likely mechanism for the formation of Lanthanide and Actinide negative

  15. Laser-Induced Optical Pumping Measurements of Cross Section for Fine- and Hyperfine-Structure Transitions in Sodium Induced by Collisions with Helium and Argon Atoms

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Sung, C. C.

    1999-01-01

    Optical pumping of the ground states of sodium can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc., which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections lor DELTA.F transitions of the P(sub 3/2) state induced by collisions with helium and argon atoms, for a range of values assumed for the P(sub 1/2), DELTA.F cross sections. The hyperfine cross sections measured using this method, which to our knowledge is novel, are compared with cross sections for transitions involving polarized magnetic substates m(sub F) measured previously using polarization sensitive absorption. Also, fine-structure transition cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping.

  16. Laser Induced Optical Pumping Measurements of Cross Sections for Fine and Hyperfine Structure Transitions in Sodium Induced by Collisions with Helium Argon Atoms

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Sung, C. C.

    1998-01-01

    Optical pumping of the ground states of sodium can radically alter the shape of the laser induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc., which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections for (Delta)F transitions of the P(sub 3/2) state induced by collisions with helium and argon atoms, for a range of values assumed for the P(sub 1/2), (Delta)F cross sections. The hyperfine cross sections measured using this method, which is thought to be novel, are compared with cross sections for transitions involving polarized magnetic substates, m(sub F), measured previously using polarization sensitive absorption. Also, fine structure transition ((Delta)J) cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping.

  17. Polarization quantum beat spectroscopy of HCF(A1A"). I. 19F and 1H hyperfine structure and Zeeman effect.

    PubMed

    Fan, Haiyan; Ionescu, Ionela; Xin, Ju; Reid, Scott A

    2004-11-01

    To further investigate the (19)F and (1)H nuclear hyperfine structure and Zeeman effect in the simplest singlet carbene, HCF, we recorded polarization quantum beat spectra (QBS) of the pure bending levels 2(0) (n) with n = 0-7 and combination bands 1(0) (1)2(0) (n) with n = 1-6 and 2(0) (n)3(0) (1) with n = 0-3 in the HCF A(1)A(")<--X(1)A(') system. The spectra were measured under jet-cooled conditions using a pulsed discharge source, both at zero field and under application of a weak magnetic field (<30 G). Analysis yielded the nuclear spin-rotation constants C(aa) and weak field Lande g(aa) factors. Consistent with a two-state model, the majority of observed vibrational levels exhibit a linear correlation of C(aa) and g(aa), and our analysis yielded effective (a) hyperfine constants for the (19)F and (1)H nuclei (in MHz) of 728(23) and 55(2), respectively. The latter was determined here owing to the high resolving power of QBS. The vibrational state selectivity of the (19)F hyperfine constants is discussed, and we suggest that the underlying Renner-Teller interaction may play an important role.

  18. Synthesis Of [2h, 13c]M [2h2m 13c], And [2h3,, 13c] Methyl Aryl Sulfones And Sulfoxides

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.; Schmidt, Jurgen G.

    2004-07-20

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfones and [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfoxides, wherein the .sup.13 C methyl group attached to the sulfur of the sulfone or sulfoxide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing methyl aryl sulfones and methyl aryl sulfoxides.

  19. Realistic models of stochastically varying hyperfine interactions caused by vacancy diffusion in L12-structured compounds

    NASA Astrophysics Data System (ADS)

    Castle, J. R.; Zacate, M. O.; Evenson, W. E.

    2013-05-01

    Perturbed angular correlation spectroscopy (PAC) is an attractive method for fundamental studies of diffusion because of the possibility to observe directly atomic scale defects involved in a diffusion process. Previous work investigated under what experimental conditions one could observe a contribution to a PAC spectrum that clearly could be attributed to a vacancy in L12-structured compounds for the special case of self-diffusion. This has since been extended in the present work to consider the case of impurity diffusion and to explore whether or not distant vacancies or configurations with multiple vacancies affect PAC spectra significantly.

  20. NMR study of non-structural proteins--part I: (1)H, (13)C, (15)N backbone and side-chain resonance assignment of macro domain from Mayaro virus (MAYV).

    PubMed

    Melekis, Efstathios; Tsika, Aikaterini C; Lichière, Julie; Chasapis, Christos T; Margiolaki, Irene; Papageorgiou, Nicolas; Coutard, Bruno; Bentrop, Detlef; Spyroulias, Georgios A

    2015-04-01

    Macro domains are ADP-ribose-binding modules present in all eukaryotic organisms, bacteria and archaea. They are also found in non-structural proteins of several positive strand RNA viruses such as alphaviruses. Here, we report the high yield expression and preliminary structural analysis through solution NMR spectroscopy of the macro domain from New World Mayaro Alphavirus. The recombinant protein was well-folded and in a monomeric state. An almost complete sequence-specific assignment of its (1)H, (15)N and (13)C resonances was obtained and its secondary structure determined by TALOS+.

  1. Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative (1)H and (13)C NMR chemical shifts.

    PubMed

    Marekha, Bogdan A; Kalugin, Oleg N; Bria, Marc; Idrissi, Abdenacer

    2015-09-21

    Mixtures of ionic liquids (ILs) with polar aprotic solvents in different combinations and under different conditions (concentration, temperature etc.) are used widely in electrochemistry. However, little is known about the key intermolecular interactions in such mixtures depending on the nature of the constituents and mixture composition. In order to systematically address the intermolecular interactions, the chemical shift variation of (1)H and (13)C nuclei has been followed in mixtures of imidazolium ILs 1-n-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4), 1-n-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6), 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate (BmimTfO) and 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimTFSI) with molecular solvent acetonitrile (AN) over the entire composition range at 300 K. The concept of relative chemical shift variation is proposed to assess the observed effects on a unified and unbiased scale. We have found that hydrogen bonds between the imidazolium ring hydrogen atoms and electronegative atoms of anions are stronger in BmimBF4 and BmimTfO ILs than those in BmimTFSI and BmimPF6. Hydrogen atom at position 2 of the imidazolium ring is substantially more sensitive to interionic hydrogen bonding than those at positions 4-5 in the case of BmimTfO and BmimTFSI ILs. These hydrogen bonds are disrupted upon dilution in AN due to ion dissociation which is more pronounced at high dilutions. Specific solvation interactions between AN molecules and IL cations are poorly manifested.

  2. The Semiquinone at the Qi Site of the bc1 Complex Explored Using HYSCORE Spectroscopy and Specific Isotopic Labeling of Ubiquinone in Rhodobacter sphaeroides via 13C Methionine and Construction of a Methionine Auxotroph

    PubMed Central

    2015-01-01

    Specific isotopic labeling at the residue or substituent level extends the scope of different spectroscopic approaches to the atomistic level. Here we describe 13C isotopic labeling of the methyl and methoxy ring substituents of ubiquinone, achieved through construction of a methionine auxotroph in Rhodobacter sphaeroides strain BC17 supplemented with l-methionine with the side chain methyl group 13C-labeled. Two-dimensional electron spin echo envelope modulation (HYSCORE) was applied to study the 13C methyl and methoxy hyperfine couplings in the semiquinone generated in situ at the Qi site of the bc1 complex in its membrane environment. The data were used to characterize the distribution of unpaired spin density and the conformations of the methoxy substituents based on density functional theory calculations of 13C hyperfine tensors in the semiquinone of the geometry-optimized X-ray structure of the bc1 complex (Protein Data Bank entry 1PP9) with the highest available resolution. Comparison with other proteins indicates individual orientations of the methoxy groups in each particular case are always different from the methoxy conformations in the anion radical prepared in a frozen alcohol solution. The protocol used in the generation of the methionine auxotroph is more generally applicable and, because it introduces a gene deletion using a suicide plasmid, can be applied repeatedly. PMID:25184535

  3. Production of Hydrolysable Tannin-Like Structures During the Microbial Demethylation of lignin: An Assessment Using13C-Labeled Tetramethylammonium Hydroxide Thermochemolysis.

    NASA Astrophysics Data System (ADS)

    Filley, T.; Blanchette, R.; Nierop, K.; Gamblin, D.

    2003-12-01

    Phenolic compounds in soils are important mediators of microbial activity, metal mobility, soil redox, and soil organic matter building processes. Direct tannin input and the microbial decomposition of lignin in litter and soil are important contributors to this pool of phenols. The ability to accurately assess the relative differences in lignin decay (which are initiated by demethylation and side chain oxidation) among synapyl, coniferyl, and p-coumaryl components of detrital lignin requires the ability to determine microbial demethylation within the complex soil residues. Differentiating between hydrolysable tannins and contributions from advanced lignin decay can be problematic for many of the most common molecular techniques such as alkaline CuO oxidation, pyrolysis GC, and tetramethylammonium hydroxide thermochemolysis because of either the masking effects of derivatizing agents, oxidative damage to ortho-phenols or low volatility of lignin monomers. In this study we investigate lignin demethylation and polyhydroxyl-aromatic production in BC and C horizons of sandy forest soils dominated by oak, the A horizon from a red spruce forest, and controlled microbial inoculation studies of woody tissue using in-line 13C-labeled tetramethylammonium hydroxide thermochemolysis. Both white-rot and brown-rot decay resulted in syringyl demethylation, with the latter exhibiting more aggressive demethylation chemistry, while coniferyl monomer demethylation was essentially restricted to brown-rot decay. In a typical brown-rot sequence demethylation of syringyl components occurs more rapidly than coniferyl units within the same tissue and lower molecular weight fragments are likewise more demethylated than lignin monomers containing the full glycerol side chain. Demethylation of both methoxyl groups in the syringyl monomer is evident in soil horizons as well as laboratory inoculations. The latter may suggest demethylation after lignin depolymerization. Low molecular weight

  4. Canopy structure and atmospheric flows in relation to the δ13C of respired CO2 in a subalpine coniferous forest

    USGS Publications Warehouse

    Schaeffer, Sean M.; Anderson, Dean E.; Burns, Sean P.; Monson, Russell K.; Sun, Jielun; Bowling, David R.

    2008-01-01

    Stable isotopes provide insight into ecosystem carbon cycling, plant physiological processes, atmospheric boundary-layer dynamics, and are useful for the integration of processes over multiple scales. Of particular interest is the carbon isotope content (δ13C) of nocturnal ecosystem-respired CO2 (δR). Recent advances in technology have made it possible to continuously examine the variation in δR within a forest canopy over relatively long time-scales (months–years). We used tunable diode laser spectroscopy to examine δR at within- and below-canopy spatial locations in a Colorado subalpine forest (the Niwot Ridge AmeriFlux site). We found a systematic pattern of increased δR within the forest canopy (δR-c) compared to that near the ground (δR-g). Values of δR-c were weakly correlated with the previous day's mean maximum daytime vapor pressure deficit (VPD). Conversely, there was a negative but still weak correlation between δR-g and time-lagged (0–5 days) daily mean soil moisture. The topography and presence of sustained nightly drainage flows at the Niwot Ridge forest site suggests that, on nights with stable atmospheric conditions, there is little mixing of air near the ground with that in the canopy. Atmospheric stability was assessed using thresholds of friction velocity, stability above the canopy, and bulk Richardson number within the canopy. When we selectively calculated δR-g and δR-c by removing time periods when ground and canopy air were well mixed, we found stronger correlations between δR-c and VPD, and δR-g and soil moisture. This suggests that there may be fundamental differences in the environmental controls on δR at sub-canopy spatial scales. These results may help explain the wide variance observed in the correlation of δR with different environmental parameters in other studies.

  5. Control of coherence among the spins of a single electron and the three nearest neighbor {sup 13}C nuclei of a nitrogen-vacancy center in diamond

    SciTech Connect

    Shimo-Oka, T.; Miwa, S.; Suzuki, Y.; Mizuochi, N.; Kato, H.; Yamasaki, S.; Jelezko, F.

    2015-04-13

    Individual nuclear spins in diamond can be optically detected through hyperfine couplings with the electron spin of a single nitrogen-vacancy (NV) center; such nuclear spins have outstandingly long coherence times. Among the hyperfine couplings in the NV center, the nearest neighbor {sup 13}C nuclear spins have the largest coupling strength. Nearest neighbor {sup 13}C nuclear spins have the potential to perform fastest gate operations, providing highest fidelity in quantum computing. Herein, we report on the control of coherences in the NV center where all three nearest neighbor carbons are of the {sup 13}C isotope. Coherence among the three and four qubits are generated and analyzed at room temperature.

  6. Reanalysis and extension of the MnH A7Π- X7Σ + (0, 0) band: Fine structure and hyperfine-induced rotational branches

    NASA Astrophysics Data System (ADS)

    Varberg, Thomas D.; Gray, Jeffrey A.; Field, Robert W.; Merer, Anthony J.

    1992-12-01

    The A7Π- X7Σ + (0, 0) band of MnH at 568 nm has been recorded by laser fluorescence excitation spectroscopy. The original rotational analysis of Nevin [ Proc. R. Irish Acad.48A, 1-45 (1942); 50A, 123-137 (1945)] has been extended with some corrections at low J. Systematic internal hyperfine perturbations in the X7Σ + state, caused by the Δ N = 0, Δ J = ±1 matrix elements of the 55Mn hyperfine term in the Hamiltonian, have been observed in all seven electron spin components over the entire range of N″ studied. These perturbations destroy the "goodness" of J″ as a quantum number, giving rise to hyperfine-induced Δ J = ±2 rotational branches and to observable energy shifts of the most severely affected levels. The A7Π state, with A = 40.5 cm -1 and B = 6.35 cm -1, evolves rapidly from Hund's case ( a) to case ( b) coupling, which produces anomalous branch patterns at low J. A total of 156 rotational branches have been identified and fitted by least squares to an effective Hamiltonian, providing precise values for the rotational and fine structure constants. Values of the principal constants determined in the fit are (1σ errors in units of the last digit are listed in parentheses): The fine structures of the A7Π and X7Σ + states confirm the assignment of the A ← X transition as Mn 4 pπ ← 4 sσ in the presence of a spectator, nonbonding Mn 3 d5 ( 6S) open core.

  7. Biosynthetic uniform 13C,15N-labelling of zervamicin IIB. Complete 13C and 15N NMR assignment.

    PubMed

    Ovchinnikova, Tatyana V; Shenkarev, Zakhar O; Yakimenko, Zoya A; Svishcheva, Natalia V; Tagaev, Andrey A; Skladnev, Dmitry A; Arseniev, Alexander S

    2003-01-01

    Zervamicin IIB is a member of the alpha-aminoisobutyric acid containing peptaibol antibiotics. A new procedure for the biosynthetic preparation of the uniformly 13C- and 15N-enriched peptaibol is described This compound was isolated from the biomass of the fungus-producer Emericellopsis salmosynnemata strain 336 IMI 58330 obtained upon cultivation in the totally 13C, 15N-labelled complete medium. To prepare such a medium the autolysed biomass and the exopolysaccharides of the obligate methylotrophic bacterium Methylobacillus flagellatus KT were used. This microorganism was grown in totally 13C, 15N-labelled minimal medium containing 13C-methanol and 15N-ammonium chloride as the only carbon and nitrogen sources. Preliminary NMR spectroscopic analysis indicated a high extent of isotope incorporation (> 90%) and led to the complete 13C- and 15N-NMR assignment including the stereospecific assignment of Aib residues methyl groups. The observed pattern of the structurally important secondary chemical shifts of 1H(alpha), 13C=O and 13C(alpha) agrees well with the previously determined structure of zervamicin IIB in methanol solution. PMID:14658801

  8. Structural, magnetic and hyperfine properties of single-phase SrFe12O19 nanoparticles prepared by a sol-gel route

    NASA Astrophysics Data System (ADS)

    Das, A.; Roychowdhury, A.; Pati, S. P.; Bandyopadhyay, S.; Das, D.

    2015-02-01

    Single-phase nanocrystalline strontium hexaferrite (SrFe12O19) powders have been synthesized by a sol-gel method and their structural, magnetic and hyperfine properties are discussed. The optimum annealing temperature of the as-prepared gel for formation of the single-phase SrFe12O19 structure has been found to be 800 °C. X-ray diffraction and Fourier transform infrared studies confirmed formation of the hexaferrite phase. The cation distribution at crystallographic inequivalent sites of the hexaferrite structure has been examined by 57Fe Mössbauer spectroscopy and found to be identical to that reported earlier. Single-phase SrFe12O19 nanoparticles (NPs) showed a magnetic hysteresis loop with high coercivity and saturation magnetization denoting an irreversible magnetization character. The temperature dependent magnetization measurements reveal a difference between the zero-field-cooled and field-cooled curves throughout the measurement range 5-300 K that is attributed to superparamagnetic relaxation of finer hexaferrite particles and disordered spins at the surface of the NPs. Both hyperfine and magnetic studies confirm that magnetic anisotropy plays a crucial role in hexaferrite NPs.

  9. POLARIZED SCATTERING OF LIGHT FOR ARBITRARY MAGNETIC FIELDS WITH LEVEL-CROSSINGS FROM THE COMBINATION OF HYPERFINE AND FINE STRUCTURE SPLITTINGS

    SciTech Connect

    Sowmya, K.; Nagendra, K. N.; Sampoorna, M.; Stenflo, J. O. E-mail: knn@iiap.res.in E-mail: stenflo@astro.phys.ethz.ch

    2015-12-01

    Interference between magnetic substates of the hyperfine structure states belonging to different fine structure states of the same term influences the polarization for some of the diagnostically important lines of the Sun's spectrum, like the sodium and lithium doublets. The polarization signatures of this combined interference contain information on the properties of the solar magnetic fields. Motivated by this, in the present paper, we study the problem of polarized scattering on a two-term atom with hyperfine structure by accounting for the partial redistribution in the photon frequencies arising due to the Doppler motions of the atoms. We consider the scattering atoms to be under the influence of a magnetic field of arbitrary strength and develop a formalism based on the Kramers–Heisenberg approach to calculate the scattering cross section for this process. We explore the rich polarization effects that arise from various level-crossings in the Paschen–Back regime in a single scattering case using the lithium atomic system as a concrete example that is relevant to the Sun.

  10. Pulsed polarization transfer for 13C NMR in solids

    NASA Astrophysics Data System (ADS)

    Bax, Ad; Szeverenyi, Nikolaus M.; Maciel, Gary E.

    A new pulsed polarization transfer experiment method is described for the polarization of 13C spins in a solid by magnetization transfer from protons. The method is directly analogous to the INEPT sequence for liquids introduced by Freeman and Morris. As polarization is transferred in PPT between individual 1H 13C pairs, rather than between spin reservoirs, different opportunities exist for structurally selective experiments. Results on p-diethoxybenzene and coronene are presented.

  11. The Fourier transform microwave spectrum of the arsenic dicarbide radical (CCAs: X (2)Pi(1/2)) and its (13)C isotopologues.

    PubMed

    Sun, M; Clouthier, D J; Ziurys, L M

    2009-12-14

    The pure rotational spectrum of the CCAs radical in its ground electronic and spin state, X (2)Pi(12), has been measured using Fourier transform microwave techniques in the frequency range of 12-40 GHz. This species was created in a supersonic expansion from a reaction mixture of AsCl(3) and C(2)H(2) or CH(4) diluted in high pressure argon, using a pulsed nozzle containing a dc discharge source. Three rotational transitions were measured for the main isotopologue, (12)C(12)CAs, in the Omega=12 ladder; both lambda-doubling and arsenic (I=32) hyperfine interactions were observed in these spectra. In addition, two to four rotational transitions were recorded for the (13)C(13)CAs, (13)C(12)CAs, and (12)C(13)CAs species. In these three isotopologues, hyperfine splittings were also resolved arising from the (13)C nuclei (I=12), creating complex spectral patterns. The CCAs spectra were analyzed with a case (a) Hamiltonian, and effective rotational, lambda-doubling, and arsenic and carbon-13 hyperfine constants were determined for the Omega=12 ladder. From the effective rotational constants of the four isotopologues, an r(m) ((1)) structure has been derived with r(C-C)=1.287 A and r(C-As)=1.745 A. These bond lengths indicate that the predominant structure for arsenic dicarbide is C=C=As, with some contributing C[Triple Bond]C and C[Triple Bond]As triple bond characters. The hyperfine constants established in this work indicate that about 23 of the unpaired electron density lies on the arsenic atom, with the remaining percentage on the terminal carbon. The value of the arsenic quadrupole coupling constant (eqQ=-202 MHz) suggests that the As-C bond has a mixture of covalent and ionic characters, consistent with theoretical predictions that both pi backbonding and electron transfer play a role in creating a linear, as opposed to a cyclic, structure for certain heteroatom dicarbides.

  12. Structure and reactivity of lithium amides. /sup 6/Li, /sup 13/C, and /sup 15/N NMR spectroscopic studies and colligative measurements of lithium diphenylamide and lithium diphenylamide-lithium bromide complex solvated by tetrahydrofuran

    SciTech Connect

    DePue, J.S.; Collum, D.B.

    1988-08-03

    /sup 6/Li, /sup 13/C, and /sup 15/N NMR spectroscopic studies of lithium diphenylamide in THF/hydrocarbon solutions (THF = tetrahydrofuran) detected two different species. /sup 6/Li and /sup 15/N NMR spectroscopic studies of (/sup 6/Li, /sup 15/N)lithium diphenylamide showed the species observed at low THF concentrations to be a cyclic oligomer. Structural analogies provided strong support for a dimer while colligative measurements at 0/degrees/C indicated the dimer to be di- or trisolvated. On the basis of the observed mass action effects, the species appearing at intermediate THF concentrations is assigned as a contact or solvent-separated ion-paired monomer. Lithium diphenylamide forms a 1:1 adduct with lithium bromide at low THF concentrations. A combination of /sup 6/Li-/sup 15/N double labeling studies and colligative measurements supports a trisolvated cyclic mixed dimer structure. Although detailed spectroscopic studies at elevated THF concentrations were precluded by high fluctionality, the similarity of the /sup 13/C chemical shifts of lithium diphenylamide in the presence and absence of lithium bromide provide indirect evidence that the mixed dimer undergoes a THF concentration dependent dissociation to the monomeric amide and free lithium bromide. 24 references, 9 figures, 2 tables.

  13. Defining fish community structure in Lake Winnipeg using stable isotopes (δ(13)C, δ(15)N, δ(34)S): implications for monitoring ecological responses and trophodynamics of mercury & other trace elements.

    PubMed

    Ofukany, Amy F A; Wassenaar, Leonard I; Bond, Alexander L; Hobson, Keith A

    2014-11-01

    The ecological integrity of freshwater lakes is influenced by atmospheric and riverine deposition of contaminants, shoreline development, eutrophication, and the introduction of non-native species. Changes to the trophic structure of Lake Winnipeg, Canada, and consequently, the concentrations of contaminants and trace elements measured in tissues of native fishes, are likely attributed to agricultural runoff from the 977,800 km(2) watershed and the arrival of non-native zooplankters and fishes. We measured δ(13)C, δ(15)N, and δ(34)S along with concentrations of 15 trace elements in 17 native fishes from the north and south basins of Lake Winnipeg in 2009 and 2010. After adjusting for differences in isotopic baseline values between the two basins, fishes in the south basin had consistently higher δ(13)C and δ(34)S, and lower δ(15)N. We found little evidence of biomagnification of trace elements at the community level, but walleye (Sander vitreus) and freshwater drum (Aplodinotus grunniens) had higher mercury and selenium concentrations with increased trophic position, coincident with increased piscivory. There was evidence of growth dilution of cobalt, copper, manganese, molybdenum, thallium, and vanadium, and bioaccumulation of mercury, which could be explained by increases in algal (and consequently, lake and fish) productivity. We conclude that the north and south basins of Lake Winnipeg represent very different communities with different trophic structures and trace element concentrations.

  14. Successful combination of computationally inexpensive GIAO 13C NMR calculations and artificial neural network pattern recognition: a new strategy for simple and rapid detection of structural misassignments.

    PubMed

    Sarotti, Ariel M

    2013-08-01

    GIAO NMR chemical shift calculations coupled with trained artificial neural networks (ANNs) have been shown to provide a powerful strategy for simple, rapid and reliable identification of structural misassignments of organic compounds using only one set of both computational and experimental data. The geometry optimization, usually the most time-consuming step in the overall procedure, was carried out using computationally inexpensive methods (MM+, AM1 or HF/3-21G) and the NMR shielding constants at the affordable mPW1PW91/6-31G(d) level of theory. As low quality NMR prediction is typically obtained with such protocols, the decision making was foreseen as a problem of pattern recognition. Thus, given a set of statistical parameters computed after correlation between experimental and calculated chemical shifts the classification was done using the knowledge derived from trained ANNs. The training process was carried out with a set of 200 molecules chosen to provide a wide array of chemical functionalities and molecular complexity, and the results were validated with a set of 26 natural products that had been incorrectly assigned along with their 26 revised structures. The high prediction effectiveness observed makes this method a suitable test for rapid identification of structural misassignments, preventing not only the publication of wrong structures but also avoiding the consequences of such a mistake.

  15. EFFECTS OF CLIMATE CHANGE ON LABILE AND STRUCTURAL CARBON IN DOUGLAS-FIR NEEDLES AS ESTIMATED BY DELTA 13C AND C AREA MEASUREMENTS

    EPA Science Inventory

    Isotopic measurements may provide new insights into levels in leaves of labile and structural carbon (C) under climate change. In a 4-year climate change experiment using Pseudotsuga menziesii (Douglas-fir) seedlings and a 2x2 factorial design in enclosed chambers (n=3), atmosph...

  16. Crystal structure and thermodynamic analysis of diagnostic mAb 106.3 complexed with BNP 5-13 (C10A)

    SciTech Connect

    Longenecker, Kenton L.; Ruan, Qiaoqiao; Fry, Elizabeth H.; Saldana, Sylvia C.; Brophy, Susan E.; Richardson, Paul L.; Tetin, Sergey Y.

    2010-09-02

    B-type natriuretic peptide (BNP) is a naturally secreted regulatory hormone that influences blood pressure and vascular water retention in human physiology. The plasma BNP concentration is a clinically recognized biomarker for various cardiovascular diseases. Quantitative detection of BNP can be achieved in immunoassays using the high-affinity monoclonal IgG1 antibody 106.3, which binds an epitope spanning residues 5-13 of the mature bioactive peptide. To understand the structural basis of this molecular recognition, we crystallized the Fab fragment complexed with the peptide epitope and determined the three-dimensional structure by X-ray diffraction to 2.1 {angstrom} resolution. The structure reveals the detailed interactions that five of the complementarity-determining regions make with the partially folded peptide. Thermodynamic measurements using fluorescence spectroscopy suggest that the interaction is enthalpy driven, with an overall change in free energy of binding, {Delta}G = -54 kJ/mol, at room temperature. The parameters are interpreted on the basis of the structural information. The kinetics of binding suggest a diffusion-limited mechanism, whereby the peptide easily adopts a bound conformation upon interaction with the antibody. Moreover, comparative analysis with alanine-scanning results of the epitope explains the basis of selectivity for BNP over other related natriuretic peptides.

  17. Using hyperfine structure to investigate perturbations between highly-excited states: the HF C-X spectrum

    NASA Astrophysics Data System (ADS)

    Philippson, Jeffrey; Shiell, Ralph; Reinhold, Elmar; Ubachs, Wim

    2009-05-01

    It has long been known that the B ^1&+circ; ion-pair state in HF is strongly perturbed by electronic Rydberg states [1]. We present a quantitative analysis of these perturbations through their effects on the fluorine orbital magnetic hyperfine parameter obtained from XUV spectra of the C ^1π, v=0-X ^1&+circ;, v=0 transition [2]. A λ-doubling interaction between the ground vibrational level of the C-state and the nearby v=29 level of the B-state produces an apparent rotational state dependence in the values of this parameter derived from the R-branch lines. This work demonstrates how insight into the extent of inter-state perturbations can be obtained from the variation of hyperfine parameters.[4pt] [1] A. E. Douglas and F. R. Greening, Can. J. Phys. 57, 1650 (1979).[0pt] [2] J. N. Philippson, R. C. Shiell, E. Reinhold and W. Ubachs, J. Chem. Phys. 129, 174310 (2008).

  18. High resolution spectroscopy of the Cs2 D 1Sigma u + -X 1Sigma g + transition and hyperfine structure

    NASA Astrophysics Data System (ADS)

    Kobayashi, Tooru; Usui, Takashi; Kumauchi, Takahiro; Baba, Masaaki; Ishikawa, Kiyoshi; Katô, Hajime

    1993-02-01

    The Doppler-free high resolution laser spectroscopy of Cs2 D 1Σu+-X 1Σg+ transition is extended up to v'=65. By comparing the spectral linewidth and the time-resolved fluorescence intensity, the line broadening observed for transitions to the D 1Σu+(v'=63,J'≤70) levels is identified as the lifetime broadening originating from the predissociation. Line splittings are observed for the D 1Σu+(v'=46,J'≥95)-X 1Σg+(v`= 1,J`) transitions and are identified as the hyperfine splitting due to a magnetic dipole interaction between nuclear spin and electron. The hyperfine splitting is attributed to mixing of the (2) 3Πu state, whose wave function changes from Hund's case (a) to case (b) at large J. The dependence of the electric dipole transition moment on the internuclear distance for the D 1Σu+-X 1Σg+ transition is determined by comparing the observed and calculated line intensities of the dispersed fluorescence.

  19. Use of dipolar 1H-15N and 1H-13C couplings in the structure determination of magnetically oriented macromolecules in solution.

    PubMed

    Tjandra, N; Omichinski, J G; Gronenborn, A M; Clore, G M; Bax, A

    1997-09-01

    Anisotropy of the molecular magnetic susceptibility gives rise to a small degree of alignment. The resulting residual dipolar couplings, which can now be measured with the advent of higher magnetic fields in NMR, contain information on the orientation of the internuclear vectors relative to the molecular magnetic susceptibility tensor, thereby providing information on long range order that is not accessible by any of the solution NMR parameters currently used in structure determination. Thus, the dipolar couplings constitute unique and powerful restraints in determining the structures of magnetically oriented macromolecules in solution. The method is demonstrated on a complex of the DNA-binding domain of the transcription factor GATA-1 with a 16 base pair oligodeoxyribonucleotide. PMID:9303001

  20. The electronic structure of the primary electron donor of reaction centers of purple bacteria at atomic resolution as observed by photo-CIDNP 13C NMR

    PubMed Central

    Daviso, Eugenio; Prakash, Shipra; Alia, A.; Gast, Peter; Neugebauer, Johannes; Jeschke, Gunnar; Matysik, Jörg

    2009-01-01

    Composed of the two bacteriochlorophyll cofactors, PL and PM, the special pair functions as the primary electron donor in bacterial reaction centers of purple bacteria of Rhodobacter sphaeroides. Under light absorption, an electron is transferred to a bacteriopheophytin and a radical pair is produced. The occurrence of the radical pair is linked to the production of enhanced nuclear polarization called photochemically induced dynamic nuclear polarization (photo-CIDNP). This effect can be used to study the electronic structure of the special pair at atomic resolution by detection of the strongly enhanced nuclear polarization with laser-flash photo-CIDNP magic-angle spinning NMR on the carotenoid-less mutant R26. In the electronic ground state, PL is strongly disturbed, carrying a slightly negative charge. In the radical cation state, the ratio of total electron spin densities between PL and PM is 2:1, although it is 2.5:1 for the pyrrole carbons, 2.2:1 for all porphyrinic carbons, and 4:1 for the pyrrole nitrogen. It is shown that the symmetry break between the electronic structures in the electronic ground state and in the radical cation state is an intrinsic property of the special pair supermolecule, which is particularly attributable to a modification of the structure of PL. The significant difference in electron density distribution between the ground and radical cation states is explained by an electric polarization effect of the nearby histidine. PMID:20018724

  1. 1H, 13C and 15N resonance assignments and secondary structure of the human PHF6-ePHD1 domain.

    PubMed

    Bao, Yun; Liu, Zhonghua; Zhang, Jiahai; Wu, Jihui; Shi, Yunyu

    2016-04-01

    The plant homeodomain (PHD) finger 6 (PHF6) is a multidomain protein that comprises four nuclear localization signals and two extended PHD zinc finger domains (ePHD), suggesting that the PHD domains of PHF6 may have different functions compared with other PHD domains. And the PHF6 was first identified as the gene mutated associated with Börjeson-Forssman-Lehmann syndrome, an X-linked mental retardation disorder. The mutant PHF6 is also associated with T cell acute lymphoblastic leukemia and acute myeloid leukemia. But the molecular mechanism between these diseases and PHF6 are still unclear. In addition, the first conserved ePHD (ePHD1) of PHF6 is involved in its nucleolus localization, directly interacts with upstream binding factor (UBF) and suppresses rRNA transcription. Here we show the backbone resonance and side chain assignments of the PHF6-ePHD1 domain from human by heteronuclear multidimensional NMR spectroscopy and its secondary structure as predicted by the TALOS+. These assignments of PHF6-ePHD1 domain throw a light on the further structure determination, dynamics and interaction with UBF.

  2. Hyperfine rather than spin splittings dominate the fine structure of the B 4Σ--X 4Σ- bands of AlC

    NASA Astrophysics Data System (ADS)

    Clouthier, Dennis J.; Kalume, Aimable

    2016-01-01

    Laser-induced fluorescence and wavelength resolved emission spectra of the B 4Σ--X 4Σ- band system of the gas phase cold aluminum carbide free radical have been obtained using the pulsed discharge jet technique. The radical was produced by electron bombardment of a precursor mixture of trimethylaluminum in high pressure argon. High resolution spectra show that each rotational line of the 0-0 and 1-1 bands of AlC is split into at least three components, with very similar splittings and intensities in both the P- and R-branches. The observed structure was reproduced by assuming bβS magnetic hyperfine coupling in the excited state, due to a substantial Fermi contact interaction of the unpaired electron in the aluminum 3s orbital. Rotational analysis has yielded ground and excited state equilibrium bond lengths in good agreement with the literature and our own ab initio values. Small discrepancies in the calculated intensities of the hyperfine lines suggest that the upper state spin-spin constant λ' is of the order of ≈0.025-0.030 cm-1.

  3. Hyperfine structure and lifetime measurements in the 4s2nd 2D3/2 Rydberg sequence of Ga I by time-resolved laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Chunqing; Tian, Yanshan; Yu, Qi; Bai, Wanshuang; Wang, Xinghao; Wang, Chong; Dai, Zhenwen

    2016-05-01

    The hyperfine structure (HFS) constants of the 4s2nd 2D3/2 (n=6-18) Rydberg sequence and the 4s26p 2P3/2 level for two isotopes of 69Ga and 71Ga atoms were measured by means of the time-resolved laser-induced fluorescence (TR-LIF) technique and the quantum beat method. The observed hyperfine quantum beat spectra were analyzed and the magnetic-dipole HFS constants A as well as the electric-quadrupole HFS constants B of these levels were obtained by Fourier transform and a program for multiple regression analysis. Also using TR-LIF method radiative lifetimes of the above sequence states were determined at room temperature. The measured lifetime values range from 69 to 2279 ns with uncertainties no more than 10%. To our knowledge, the HFS constants of this Rydberg sequence and the lifetimes of the 4s2nd 2D3/2 (n=10-18) levels are reported for the first time. Good agreement between our results and the previous is achieved.

  4. New guidelines for δ13C measurements

    USGS Publications Warehouse

    Coplen, Tyler B.; Brand, Willi A.; Gehre, Matthias; Groning, Manfred; Meijer, Harro A. J.; Toman, Blaza; Verkouteren, R. Michael

    2006-01-01

    Consistency of δ13C measurements can be improved 39−47% by anchoring the δ13C scale with two isotopic reference materials differing substantially in 13C/12C. It is recommended thatδ13C values of both organic and inorganic materials be measured and expressed relative to VPDB (Vienna Peedee belemnite) on a scale normalized by assigning consensus values of −46.6‰ to L-SVEC lithium carbonate and +1.95‰ to NBS 19 calcium carbonate. Uncertainties of other reference material values on this scale are improved by factors up to two or more, and the values of some have been notably shifted:  the δ13C of NBS 22 oil is −30.03%.

  5. 1H, 13C, 195Pt and 15N NMR structural correlations in Pd(II) and Pt(II) chloride complexes with various alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline.

    PubMed

    Pawlak, Tomasz; Pazderski, Leszek; Sitkowski, Jerzy; Kozerski, Lech; Szłyk, Edward

    2011-02-01

    (1)H, (13)C, (195)Pt and (15)N NMR studies of platinide(II) (M = Pd, Pt) chloride complexes with such alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline as LL = 6,6'-dimethyl-bpy, 5,5'-dimethyl-bpy, 4,4'-di-tert-butyl-bpy, 2,9-dimethyl-phen, 2,9-dimethyl-4,7-diphenyl-phen, 3,4,7,8-tetramethyl-phen, having the general [M(LL)Cl(2)] formula were performed and the respective chemical shifts (δ(1H), δ(13C), δ(195Pt), δ(15N)) reported. (1)H high-frequency coordination shifts (Δ(coord)(1H) = δ(complex)(1H)-δ(ligand)(1H)) mostly pronounced for nitrogen-adjacent protons and methyl groups in the nearest adjacency of nitrogen, as well as (15)N low-frequency coordination shifts (Δ(coord)(15H) = δ(complex)(15H)-δ(ligand)(15H)) were discussed in relation to the molecular structures.

  6. Structural, elastic, and electronic properties of icosahedral boron subcarbides (B12C3, B13C2), subnitride B12N2, and suboxide B12O2 from data of SCC-DFTB calculations

    NASA Astrophysics Data System (ADS)

    Enyashin, A. N.; Ivanovskii, A. L.

    2011-08-01

    The structural, elastic, and electronic properties of a series of icosahedral phases, such as boron subcarbides B12C3 and B13C2, subnitride B12N2, and suboxide B12O2, have been studied in the framework of the SCC-DFTB method. It has been found that the B12C2 and B13C2 phases manifest metal-like properties, while B12C3 and B12O2 are semiconductors. The estimates have shown that the insertion of 2 p atoms (C, N, or O) into intericosahedral pores of elemental boron can cause both a decrease in its elastic modulus (an increase in the compressibility of B12N2) and a sharp increase in the modulus B (in subcarbides B12C3 and B12BCC). On the other hand, the insertion of 2 p atoms into α-B12 will favor an increase in its hardness (suboxide B12O2 will have a maximum hardness).

  7. Observation and analysis of the hyperfine structure of near-dissociation levels of the NaCs c +3Σ state below the dissociation limit 3 S1 /2+6 P3 /2

    NASA Astrophysics Data System (ADS)

    Liu, Wenliang; Wu, Jizhou; Ma, Jie; Li, Peng; Sovkov, Vladimir B.; Xiao, Liantuan; Jia, Suotang

    2016-09-01

    We report photoassociation (PA) of ultracold Na and Cs atoms in a dual-species magneto-optical trap. Trap loss spectroscopy of the ultracold polar NaCs molecules formed by PA, which carries information about relative PA transition strengths, has been experimentally obtained by using highly sensitive modulation spectroscopy technique. The fine and hyperfine effects at near-dissociation levels of NaCs molecular c +3Σ state are observed and modeled. The interaction Hamiltonian is described in terms of the Hund's case (a ) coupling scheme. The molecular hyperfine structure of near-dissociation levels is simulated within a simplified model of four interacting vibrational levels belonging to different initially unperturbed electronic states. The results of the simulation infer that the interaction parameters of the observed near-dissociation levels are close to the asymptotic parameters of the pair of atoms. The coupling of the electronic states is essential for forming the hyperfine structure.

  8. Millimeter-wave spectroscopy and multichannel quantum-defect-theory analysis of high Rydberg states of xenon: The hyperfine structure of {sup 129}Xe{sup +} and {sup 131}Xe{sup +}

    SciTech Connect

    Schaefer, Martin; Raunhardt, Matthias; Merkt, Frederic

    2010-03-15

    Millimeter-wave transitions between high-n Rydberg states of several isotopes of xenon have been recorded at sub-megahertz resolution. The fine and, for {sup 129}Xe and {sup 131}Xe, hyperfine structures of s, p, d, and f Rydberg states with principal quantum number in the range 52{<=}n{<=}64 have been determined from combination differences and analyzed using multichannel quantum defect theory. Improved eigenquantum defects and channel interaction parameters for the odd- and even-parity Rydberg states of xenon and the hyperfine structure of the {sup 2}P{sub 3/2} ground state of {sup 129}Xe{sup +} and {sup 131}Xe{sup +} have been obtained. Nearly degenerate p and d fine or hyperfine levels are very easily mixed by even weak stray electric fields.

  9. Magnetic hyperfine structure of the ground-state doublet in highly charged ions 89+,87+229Th and the Bohr-Weisskopf effect

    NASA Astrophysics Data System (ADS)

    Tkalya, E. V.; Nikolaev, A. V.

    2016-07-01

    Background: The search for new opportunities to investigate the low-energy level in the 229Th nucleus, which is nowadays intensively studied experimentally, has motivated us to theoretical studies of the magnetic hyperfine (MHF) structure of the 5 /2+ (0.0 eV) ground state and the low-lying 3 /2+ (7.8 eV) isomeric state in highly charged 89+229Th and 87+229Th ions. Purpose: The aim is to calculate, with the maximal precision presently achievable, the energy of levels of the hyperfine structure of the 229Th ground-state doublet in highly charged ions and the probability of radiative transitions between these levels. Methods: The distribution of the nuclear magnetization (the Bohr-Weisskopf effect) is accounted for in the framework of the collective nuclear model with Nilsson model wave functions for the unpaired neutron. Numerical calculations using precise atomic density functional theory methods, with full account of the electron self-consistent field, have been performed for the electron structure inside and outside the nuclear region. Results: The deviations of the MHF structure for the ground and isomeric states from their values in a model of a pointlike nuclear magnetic dipole are calculated. The influence of the mixing of the states with the same quantum number F on the energy of sublevels is studied. Taking into account the mixing of states, the probabilities of the transitions between the components of the MHF structure are calculated. Conclusions: Our findings are relevant for experiments with highly ionized 229Th ions in a storage ring at an accelerator facility.

  10. Hyperfine, rotational, and Zeeman structure of the lowest vibrational levels of the {sup 87}Rb{sub 2} (1) {sup 3{Sigma}}{sub g}{sup +} state

    SciTech Connect

    Takekoshi, T.; Lang, F.; Strauss, C.; Denschlag, J. Hecker; Lysebo, Marius; Veseth, Leif

    2011-06-15

    We present the results of an experimental and theoretical study of the electronically excited (1){sup 3{Sigma}}{sub g}{sup +} state of {sup 87}Rb{sub 2} molecules. The vibrational energies are measured for deeply bound states from the bottom up to v{sup '}=15 using laser spectroscopy of ultracold Rb{sub 2} Feshbach molecules. The spectrum of each vibrational state is dominated by a 47-GHz splitting into 0{sub g}{sup -} and 1{sub g} components caused mainly by a strong second-order spin-orbit interaction. Our spectroscopy fully resolves the rotational, hyperfine, and Zeeman structure of the spectrum. We are able to describe this structure to the first order using a simplified effective Hamiltonian.

  11. NMR study of non-structural proteins--part II: (1)H, (13)C, (15)N backbone and side-chain resonance assignment of macro domain from Venezuelan equine encephalitis virus (VEEV).

    PubMed

    Makrynitsa, Garyfallia I; Ntonti, Dioni; Marousis, Konstantinos D; Tsika, Aikaterini C; Lichière, Julie; Papageorgiou, Nicolas; Coutard, Bruno; Bentrop, Detlef; Spyroulias, Georgios A

    2015-10-01

    Macro domains consist of 130-190 amino acid residues and appear to be highly conserved in all kingdoms of life. Intense research on this field has shown that macro domains bind ADP-ribose and other similar molecules, but their exact function still remains intangible. Macro domains are highly conserved in the Alphavirus genus and the Venezuelan equine encephalitis virus (VEEV) is a member of this genus that causes fatal encephalitis to equines and humans. In this study we report the high yield recombinant expression and preliminary solution NMR study of the macro domain of VEEV. An almost complete sequence-specific assignment of its (1)H, (15)N and (13)C resonances was obtained and its secondary structure predicted by TALOS+. The protein shows a unique mixed α/β-fold.

  12. Uniform {sup 15}N- and {sup 15}N/{sup 13}C-labeling of proteins in mammalian cells and solution structure of the amino terminal fragment of u-PA

    SciTech Connect

    Hansen, A.P.; Petros, A.M.; Meadows, R.P.; Mazar, A.P.; Nettesheim, D.G.; Pederson, T.M.; Fesik, S.W.

    1994-12-01

    Urokinase-type plasminogen activator (u-PA) is a 54-kDa glycoprotein that catalyzes the conversion of plasminogen to plasmin, a broad-specificity protease responsible for the degradation of fibrin clots and extracellular matrix components. The u-PA protein consists of three individual modules: a growth factor domain (GFD), a kringle, and a serine protease domain. The amino terminal fragment (ATF) includes the GFD-responsible for u-PA binding to its receptor-and the kringle domains. This protein was expressed and uniformly {sup 15}N-and {sup 15}N/{sup 13}C-labeled in mammalian cells by methods that will be described. In addition, we present the three-dimensional structure of ATF that was derived from 1299 NOE-derived distance restraints along with the {phi} angle and hydrogen bonding restraints. Although the individual domains in the structures were highly converged, the two domains are structurally independent. The overall structures of the individual domains are very similar to the structures of homologous proteins. However, important structural differences between the growth factor domain of u-PA and other homologous proteins were observed in the region that has been implicated in binding the urokinase receptor. These results may explain, in part, why other growth factors show no appreciable affinity for the urokinase receptor.

  13. Experimental investigation of the hyperfine spectra of Pr I-lines: Discovery of new fine structure levels with high angular momentum

    NASA Astrophysics Data System (ADS)

    Siddiqui, Imran; Khan, Shamim; Windholz, Laurentius

    2014-05-01

    We present 66 even and 58 odd parity newly discovered fine structure levels of Pr I with high angular momentum: J = 15/2, 17/2 and 19/2 and 21/2. Spectral lines in the range 4200 Å to 7500 Å were experimentally investigated using laser induced fluorescence spectroscopy in a hollow cathode discharge lamp. The levels were discovered by analysis of the recorded hyperfine patterns of the investigated transitions. More than 800 spectral lines could be classified with help of these levels. Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2014-50025-7

  14. In vivo13C spectroscopy in the rat brain using hyperpolarized [1- 13C]pyruvate and [2- 13C]pyruvate

    NASA Astrophysics Data System (ADS)

    Marjańska, Małgorzata; Iltis, Isabelle; Shestov, Alexander A.; Deelchand, Dinesh K.; Nelson, Christopher; Uğurbil, Kâmil; Henry, Pierre-Gilles

    2010-10-01

    The low sensitivity of 13C spectroscopy can be enhanced using dynamic nuclear polarization. Detection of hyperpolarized [1- 13C]pyruvate and its metabolic products has been reported in kidney, liver, and muscle. In this work, the feasibility of measuring 13C signals of hyperpolarized 13C metabolic products in the rat brain in vivo following the injection of hyperpolarized [1- 13C]pyruvate and [2- 13C]pyruvate is investigated. Injection of [2- 13C]pyruvate led to the detection of [2- 13C]lactate, but no other downstream metabolites such as TCA cycle intermediates were detected. Injection of [1- 13C]pyruvate enabled the detection of both [1- 13C]lactate and [ 13C]bicarbonate. A metabolic model was used to fit the hyperpolarized 13C time courses obtained during infusion of [1- 13C]pyruvate and to determine the values of VPDH and VLDH.

  15. Monomeric and dimeric structures analysis and spectroscopic characterization of 3,5-difluorophenylboronic acid with experimental (FT-IR, FT-Raman, 1H and 13C NMR, UV) techniques and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Karabacak, Mehmet; Kose, Etem; Atac, Ahmet; Asiri, Abdullah M.; Kurt, Mustafa

    2014-01-01

    The spectroscopic properties of 3,5-difluorophenylboronic acid (3,5-DFPBA, C6H3F2B(OH)2) were investigated by FT-IR, FT-Raman UV-Vis, 1H and 13C NMR spectroscopic techniques. FT-IR (4000-400 cm-1) and FT-Raman spectra (3500-10 cm-1) in the solid phase and 1H and 13C NMR spectra in DMSO solution were recorded. The UV spectra that dissolved in ethanol and water were recorded in the range of 200-400 nm for each solution. The structural and spectroscopic data of the molecule have been obtained for possible three conformers from DFT (B3LYP) with 6-311++G(d,p) basis set calculations. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. Hydrogen-bonded dimer of title molecule, optimized by counterpoise correction, was also studied B3LYP at the 6-311++G(d,p) level and the effects of molecular association through O-H⋯O hydrogen bonding have been discussed. 1H and 13C NMR chemical shifts were calculated by using the gauge-invariant atomic orbital (GIAO) method. The electronic properties, such as excitation energies, oscillator strength, wavelengths, HOMO and LUMO energies, were performed by time-dependent density functional theory (TD-DFT) results complements with the experimental findings. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (OPDOS) diagrams analysis were presented. The effects due to the substitutions of boric acid group and halogen were investigated. The results of the calculations were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP), nonlinear optical properties (NLO) and thermodynamic features were performed.

  16. 1H, 15N, and 13C backbone chemical shift assignments, secondary structure, and magnesium-binding characteristics of the Bacillus subtilis response regulator, Spo0F, determined by heteronuclear high-resolution NMR.

    PubMed Central

    Feher, V. A.; Zapf, J. W.; Hoch, J. A.; Dahlquist, F. W.; Whiteley, J. M.; Cavanagh, J.

    1995-01-01

    Spo0F, sporulation stage 0 F protein, a 124-residue protein responsible, in part, for regulating the transition of Bacillus subtilis from a vegetative state to a dormant endospore, has been studied by high-resolution NMR. The 1H, 15N, and 13C chemical shift assignments for the backbone residues have been determined from analyses of 3D spectra, 15N TOCSY-HSQC, 15N NOESY-HSQC, HNCA, and HN(CO)CA. Assignments for many sidechain proton resonances are also reported. The secondary structure, inferred from short- and medium-range NOEs, 3JHN alpha coupling constants, and hydrogen exchange patterns, define a topology consistent with a doubly wound (alpha/beta)5 fold. Interestingly, comparison of the secondary structure of Spo0F to the structure of the Escherichia coli response regulator, chemotaxis Y protein (CheY) (Volz K, Matsumura P, 1991, J Biol Chem 266:15511-15519; Bruix M et al., 1993, Eur J Biochem 215:573-585), show differences in the relative length of secondary structure elements that map onto a single face of the tertiary structure of CheY. This surface may define a region of binding specificity for response regulators. Magnesium titration of Spo0F, followed by amide chemical shift changes, gives an equilibrium dissociation constant of 20 +/- 5 mM. Amide resonances most perturbed by magnesium binding are near the putative site of phosphorylation, Asp 54. PMID:8528078

  17. A 13C-NMR study of azacryptand complexes.

    PubMed

    Wild, Aljoscha A C; Fennell, Kevin; Morgan, Grace G; Hewage, Chandralal M; Malthouse, J Paul G

    2014-09-28

    An azacryptand has been solubilised in aqueous media containing 50% (v/v) dimethyl sulphoxide. (13)C-NMR has been used to determine how the azacryptand is affected by zinc binding at pH 10. Using (13)C-NMR and (13)C-enriched bicarbonate we have been able to observe the formation of 4 different carbamate derivatives of the azacryptand at pH 10. The azacryptand was shown to solubilise zinc or cadmium at alkaline pHs. Two moles of zinc are bound per mole of azacryptand and this complex binds 1 mole of carbonate. By replacing the zinc with cadmium-113 we have shown that the (13)C-NMR signal of the (13)C-enriched carbon of the bound carbonate is split into two triplets at 2.2 °C. This shows that two cadmium complexes are formed and in each of these complexes the carbonate group is bound by two magnetically equivalent metal ions. It also demonstrates that these cadmium complexes are not in fast exchange. From temperature studies we show that in the zinc complexes both complexes are in fast exchange with each other but are in slow exchange with free bicarbonate. HOESY is used to determine the position of the carbonate carbon in the complex. The solution and crystal structures of the zinc-carbonate-azacryptand complexes are compared. PMID:25091182

  18. Vanadium bisimide bonding investigated by X-ray crystallography, 51V and 13C nuclear magnetic resonance spectroscopy, and V L(3,2)-edge X-ray absorption near-edge structure spectroscopy.

    PubMed

    La Pierre, Henry S; Minasian, Stefan G; Abubekerov, Mark; Kozimor, Stosh A; Shuh, David K; Tyliszczak, Tolek; Arnold, John; Bergman, Robert G; Toste, F Dean

    2013-10-01

    Syntheses of neutral halide and aryl vanadium bisimides are described. Treatment of VCl2(NtBu)[NTMS(N(t)Bu)], 2, with PMe3, PEt3, PMe2Ph, or pyridine gave vanadium bisimides via TMSCl elimination in good yield: VCl(PMe3)2(N(t)Bu)2 3, VCl(PEt3)2(N(t)Bu)2 4, VCl(PMe2Ph)2(N(t)Bu)2 5, and VCl(Py)2(N(t)Bu)2 6. The halide series (Cl-I) was synthesized by use of TMSBr and TMSI to give VBr(PMe3)2(N(t)Bu)2 7 and VI(PMe3)2(N(t)Bu)2 8. The phenyl derivative was obtained by reaction of 3 with MgPh2 to give VPh(PMe3)2(N(t)Bu)2 9. These neutral complexes are compared to the previously reported cationic bisimides [V(PMe3)3(N(t)Bu)2][Al(PFTB)4] 10, [V(PEt3)2(N(t)Bu)2][Al(PFTB)4] 11, and [V(DMAP)(PEt3)2(N(t)Bu)2][Al(PFTB)4] 12 (DMAP = dimethylaminopyridine, PFTB = perfluoro-tert-butoxide). Characterization of the complexes by X-ray diffraction, (13)C NMR, (51)V NMR, and V L(3,2)-edge X-ray absorption near-edge structure (XANES) spectroscopy provides a description of the electronic structure in comparison to group 6 bisimides and the bent metallocene analogues. The electronic structure is dominated by π bonding to the imides, and localization of electron density at the nitrogen atoms of the imides is dictated by the cone angle and donating ability of the axial neutral supporting ligands. This phenomenon is clearly seen in the sensitivity of (51)V NMR shift, (13)C NMR Δδ(αβ), and L3-edge energy to the nature of the supporting phosphine ligand, which defines the parameters for designing cationic group 5 bisimides that would be capable of breaking stronger σ bonds. Conversely, all three methods show little dependence on the variable equatorial halide ligand. Furthermore, this analysis allows for quantification of the electronic differences between vanadium bisimides and the structurally analogous mixed Cp/imide system CpV(N(t)Bu)X2 (Cp = C5H5(1-)). PMID:24024833

  19. Solving the Tautomeric Equilibrium of Purine Through the Analysis of the Complex Hyperfine Structure of the Four 14N Nuclei

    NASA Astrophysics Data System (ADS)

    Cocinero, Emilio J.; Uriarte, Iciar; Ecija, Patricia; Favero, Laura B.; Spada, Lorenzo; Calabrese, Camilla; Caminati, Walther

    2016-06-01

    Microwave spectroscopy has been restricted to the investigation of small molecules in the last years. However, with the advent of FTMW and CP-FTMW spectroscopies coupled with laser vaporization techniques it has turned into a very competitive methodology in the studies of moderate-size biomolecules. Here, we present the study of purine, characterized by two aromatic rings, one six- and one five-membered, fused together to give a planar aromatic bicycle. Biologically, it is the mainframe of two of the five nucleobases of DNA and RNA. Two tautomers were observed by FTMW spectroscopy coupled to UV ultrafast laser vaporization system. The population ratio of the two main tautomers [N(7)H]/[N(9)H] is about 1/40 in the gas phase. It contrasts with the solid state where only the N(7)H species is present, or in solution where a mixture of both tautomers is observed. For both species, a full quadrupolar hyperfine analysis has been performed. This has led to the determination of the full sets of diagonal quadrupole coupling constants of the four 14N atoms, which have provided crucial information for the unambiguous identification of both species. T. J. Balle and W. H. Flygare Rev. Sci. Instrum. 52, 33-45, 1981 J.-U. Grabow, W. Stahl and H. Dreizler Rev. Sci. Instrum. 67, 4072-4084, 1996 G. G. Brown, B. D. Dian, K. O. Douglass, S. M. Geyer, S. T. Shipman and B. H. Pate Rev. Sci. Instrum. 79, 0531031/1-053103/13, 2008 E. J. Cocinero, A. Lesarri, P. écija, F. J. Basterretxea, J. U. Grabow, J. A. Fernández and F. Castaño Angew. Chem. Int. Ed. 51, 3119-3124, 2012

  20. Structure-based predictions of 13C-NMR chemical shifts for a series of 2-functionalized 5-(methylsulfonyl)-1-phenyl-1H-indoles derivatives using GA-based MLR method

    NASA Astrophysics Data System (ADS)

    Ghavami, Raouf; Sadeghi, Faridoon; Rasouli, Zolikha; Djannati, Farhad

    2012-12-01

    Experimental values for the 13C NMR chemical shifts (ppm, TMS = 0) at 300 K ranging from 96.28 ppm (C4' of indole derivative 17) to 159.93 ppm (C4' of indole derivative 23) relative to deuteride chloroform (CDCl3, 77.0 ppm) or dimethylsulfoxide (DMSO, 39.50 ppm) as internal reference in CDCl3 or DMSO-d6 solutions have been collected from literature for thirty 2-functionalized 5-(methylsulfonyl)-1-phenyl-1H-indole derivatives containing different substituted groups. An effective quantitative structure-property relationship (QSPR) models were built using hybrid method combining genetic algorithm (GA) based on stepwise selection multiple linear regression (SWS-MLR) as feature-selection tools and correlation models between each carbon atom of indole derivative and calculated descriptors. Each compound was depicted by molecular structural descriptors that encode constitutional, topological, geometrical, electrostatic, and quantum chemical features. The accuracy of all developed models were confirmed using different types of internal and external procedures and various statistical tests. Furthermore, the domain of applicability for each model which indicates the area of reliable predictions was defined.

  1. Examination of the structure in solid state of amino analogs of 4,4‧-[1,5-pentanediylbis(oxy)]bisbenzonitrile by means of X-ray diffraction, 13C CP/MAS NMR, and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Maciejewska, Dorota; Wolska, Irena; Żabiński, Jerzy

    2008-05-01

    A single crystal of X-ray diffraction structures is presented for 4,4'-[1,5-(3-oxapentanediylbis(amino))]bisbenzonitrile 2 and 4,4'-[1,5-( N-methyl-3-azapentane-diylbis(oxy))]bisbenzonitrile 3. The molecular structures of these derivatives differ especially in conformations of the central linker: in 2 this linker adopts a trans/ gauche conformation, whereas in 3 - a fully extended conformation. The N atoms in various positions of the aliphatic linker change dramatically the molecular packing mode of both bisnitriles. But in both cases the nitrile groups take part in intermolecular hydrogen bonds: a type of N sbnd H···N in 2 and of C sbnd H···N in 3. Various conformations of both molecules were reflected in 13C CP/MAS NMR spectra in solid state as single and double resonance patterns for 2 and 3, respectively. A preliminary anticancer assay against 60 cell lines of 3 reveals strong growth inhibition of leukemia, melanoma, and renal cancer cells.

  2. (13)C-(13)c homonuclear recoupling in solid-state nuclear magnetic resonance at a moderately high magic-angle-spinning frequency.

    PubMed

    Mithu, Venus Singh; Bakthavatsalam, Subha; Madhu, Perunthiruthy K

    2013-01-01

    Two-dimensional (13)C-(13)C correlation experiments are widely employed in structure determination of protein assemblies using solid-state nuclear magnetic resonance. Here, we investigate the process of (13)C-(13)C magnetisation transfer at a moderate magic-angle-spinning frequency of 30 kHz using some of the prominent second-order dipolar recoupling schemes. The effect of isotropic chemical-shift difference and spatial distance between two carbons and amplitude of radio frequency on (1)H channel on the magnetisation transfer efficiency of these schemes is discussed in detail.

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

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-10-28

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

  4. Feasibility of Multianimal Hyperpolarized 13C MRS

    PubMed Central

    Ramirez, Marc S.; Lee, Jaehyuk; Walker, Christopher M.; Chen, Yunyun; Kingsley, Charles V.; De La Cerda, Jorge; Maldonado, Kiersten L.; Lai, Stephen Y.; Bankson, James A.

    2014-01-01

    Purpose There is great potential for real-time investigation of metabolism with MRS and hyperpolarized (HP) 13C agents. Unfortunately, HP technology has high associated costs and efficiency limitations that may constrain in vivo studies involving many animals. To improve the throughput of preclinical investigations, we evaluate the feasibility of performing HP MRS on multiple animals simultaneously. Methods Simulations helped assess the viability of a dual-coil strategy for spatially-localized multivolume MRS.A dual-mouse system was assembled and characterized based on bench- and scanner-based experiments. Enzyme phantoms mixed with HP [1-13C] pyruvate emulated real-time metabolism and offered a controlled mechanism for evaluating system performance. Finally, a normal mouse and a mouse bearing a subcutaneous xenograft of colon cancer were simultaneously scanned in vivo using an agent containing HP [1-13C] pyruvate. Results Geometric separation/rotation, active decoupling, and use of low input impedance preamplifiers permitted an encode-by-channel approach for spatially-localized MRS. A pre-calibrated shim allowed straightforward metabolite differentiation in enzyme phantom and in vivo experiments at 7 T, with performance similar to conventional acquisitions. Conclusion The initial feasibility of multi-animal HP 13C MRS was established. Throughput scales with the number of simultaneously-scanned animals, demonstrating the potential for significant improvements in study efficiency. PMID:24903532

  5. The hyperfine structure of the lowest doublet states of the LiO2 isomers: a density-functional-theory assessment

    NASA Astrophysics Data System (ADS)

    Oliveira, João P. C.; Rivelino, Roberto

    2010-05-01

    Density-functional-theory (DFT) calculations of the hyperfine coupling constants (HFCCs) are systematically reported for the lithium superoxide (LiO2) structural isomers in the doublet ground states, \\tilde X 2A2 and 2Π. Also, structure, harmonic frequencies, rotational constants and dipole moments have been computed at different levels of theory. Our results calculated for the 2A2 state are compared with the available data of matrix-isolated LiO2. Geometric parameters and vibrational modes compare well with available experimental data. However, the present density-functional results show a strong dependence of the isotropic HFCCs on the level of approximation as well as the molecular geometry. Our results confirm that the anisotropic contributions are less sensitive to the exchange-correlation potentials and basis sets. We have obtained the best estimate of the isotropic HFCC (in comparison with the experimental trends) by using the hybrid scheme that combines the Perdew-Wang's 1991 correlation functional with the adiabatic connection. This study allows us to gauge DFT methods for future applications in the alkali superoxide series, as well as open-shell metal centres interacting with dioxygen in biological systems.

  6. Hyperfine interaction in hydrogenated graphene

    NASA Astrophysics Data System (ADS)

    Garcia, Noel; Melle, Manuel; Fernandez-Rossier, Joaquin

    We study the hyperfine interaction of Hydrogen chemisorbed in graphene nanostructures with a gap in their spectrum, such as islands and ribbons. Chemisorption of Hydrogen on graphene results in a bound in-gap state that hosts a single electron localized around the adatom. Using both density functional theory and a four-orbital tight-binding model we study the hyperfine interaction between the hydrogen nuclear spin and the conduction electrons in graphene. We find that the strength of the hyperfine interaction decreases for larger nanostructures for which the energy gap is smaller. We then compare the results of the hyperfine interaction for large nanostructures with those of graphene 2D crystal with a periodic arrangement of chemisorbed Hydrogen atoms, obtaining very similar results. The magnitude of the hyperfine interaction is about 150 MHz, in line with that of Si:P. We acknowledge financial support by Marie-Curie-ITN 607904-SPINOGRAPH.

  7. The influence of hyperfine structure and isotope shift on the detection of Rb by 2 f-wavelength modulation diode laser absorption spectrometry—experimental verification of simulations

    NASA Astrophysics Data System (ADS)

    Gustafsson, Jörgen; Axner, Ove

    1998-12-01

    This work presents an experimental verification of a previously developed methodology for simulation of the 2 f-wavelength modulation diode laser absorption spectrometry technique (2 f-WM-DLAS) when the influence of hyperfine structure, isotope shift and collisional broadening and shift of an atomic transition is taken into account [J. Gustafsson, D. Rojas and O. Axner, Spectrochim. Acta, 52B, 1937-1953 (1997)]. The pilot element in the simulations was Rb, detected at the 780 nm 5s 2S 1/2-5p 2P 3/2 transition, in low-pressure cells and atmospheric-pressure reservoirs (e.g. graphite furnaces). This experimental investigation verifies that the simulations are able to predict, with good accuracy, experimental 2 f-WM signals from Rb atoms under both low-pressure, room-temperature conditions and atmospheric-pressure, high-temperature conditions. This implies that the previously published simulation methodology can be used for predicting and optimizing 2 f-WM signal strengths and shapes from Rb atoms (and thereby presumably also from other atoms) under a variety of pressure and temperature conditions.

  8. Hyperfine structure and magnetic properties of Zn doped Co2Z hexaferrite investigated by high-field Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Lim, Jung Tae; Kim, Chul Sung

    2015-05-01

    The polycrystalline samples of Ba3Co2-xZnxFe24O41 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) were synthesized by the standard solid-state-reaction method. Based on the XRD patterns analyzed by Rietveld refinement, the structure was determined to be single-phased hexagonal with space group of P63/mmc. With increasing Zn ion concentration, the unit cell volume (Vu) of samples was increased, as the sites of Fe3+ ions changed from tetrahedral to octahedral sites. We have obtained zero-field Mössbauer spectra of all samples at various temperatures ranging from 4.2 to 750 K. The measured spectra below TC were analyzed with six distinguishable sextets due to the superposition of ten-sextets for Fe sites, corresponding to the Z-type hexagonal ferrite. Also, the hyperfine field (Hhf) and electric quadrupole shift (EQ) have shown abrupt changes around spin transition temperature (TS). In addition, Mössbauer spectra of all samples at 4.2 K were taken with an applied field ranging from 0 to 50 kOe, which indicates the decrease in the canting angle between applied field and Hhf of samples with increasing Zn concentration.

  9. IMPROVED V II log(gf) VALUES, HYPERFINE STRUCTURE CONSTANTS, AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937

    SciTech Connect

    Wood, M. P.; Lawler, J. E.; Den Hartog, E. A.; Sneden, C.; Cowan, J. J. E-mail: jelawler@wisc.edu E-mail: chris@verdi.as.utexas.edu

    2014-10-01

    New experimental absolute atomic transition probabilities are reported for 203 lines of V II. Branching fractions are measured from spectra recorded using a Fourier transform spectrometer and an echelle spectrometer. The branching fractions are normalized with radiative lifetime measurements to determine the new transition probabilities. Generally good agreement is found between this work and previously reported V II transition probabilities. Two spectrometers, independent radiometric calibration methods, and independent data analysis routines enable a reduction in systematic uncertainties, in particular those due to optical depth errors. In addition, new hyperfine structure constants are measured for selected levels by least squares fitting line profiles in the FTS spectra. The new V II data are applied to high resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to determine new, more accurate V abundances. Lines covering a range of wavelength and excitation potential are used to search for non-LTE effects. Very good agreement is found between our new solar photospheric V abundance, log ε(V) = 3.95 from 15 V II lines, and the solar-system meteoritic value. In HD 84937, we derive [V/H] = –2.08 from 68 lines, leading to a value of [V/Fe] = 0.24.

  10. Hyperfine structure and magnetic properties of Zn doped Co{sub 2}Z hexaferrite investigated by high-field Mössbauer spectroscopy

    SciTech Connect

    Lim, Jung Tae; Kim, Chul Sung

    2015-05-07

    The polycrystalline samples of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0, 1.5, and 2.0) were synthesized by the standard solid-state-reaction method. Based on the XRD patterns analyzed by Rietveld refinement, the structure was determined to be single-phased hexagonal with space group of P6{sub 3}/mmc. With increasing Zn ion concentration, the unit cell volume (V{sub u}) of samples was increased, as the sites of Fe{sup 3+} ions changed from tetrahedral to octahedral sites. We have obtained zero-field Mössbauer spectra of all samples at various temperatures ranging from 4.2 to 750 K. The measured spectra below T{sub C} were analyzed with six distinguishable sextets due to the superposition of ten-sextets for Fe sites, corresponding to the Z-type hexagonal ferrite. Also, the hyperfine field (H{sub hf}) and electric quadrupole shift (E{sub Q}) have shown abrupt changes around spin transition temperature (T{sub S}). In addition, Mössbauer spectra of all samples at 4.2 K were taken with an applied field ranging from 0 to 50 kOe, which indicates the decrease in the canting angle between applied field and H{sub hf} of samples with increasing Zn concentration.

  11. (1)H, (13)C, and (15)N resonance assignments and secondary structure information for Methylobacterium extorquens PqqD and the complex of PqqD with PqqA.

    PubMed

    Evans, Robert L; Latham, John A; Klinman, Judith P; Wilmot, Carrie M; Xia, Youlin

    2016-10-01

    The ribosomally synthesized and post-translationally modified peptide (RiPP), pyrroloquinoline quinone (PQQ), is a dehydrogenase cofactor synthesized by, but not exclusively used by, certain prokaryotes. RiPPs represent a rapidly expanding and diverse class of natural products-many of which have therapeutic potential-and the biosynthetic pathways for these are gaining attention. Five gene products from the pqq operon (PqqA, PqqB, PqqC, PqqD, and PqqE) are essential for PQQ biosynthesis. The substrate is the peptide PqqA, which is presented to the radical SAM enzyme PqqE by the small protein PqqD. PqqA is unstructured in solution, and only binds to PqqE when in complex with PqqD. PqqD is a member of a growing family of RiPP chaperone proteins (or domains in most cases) that present their associated peptide substrates to the initial RiPP biosynthesis enzymes. An X-ray crystal structure exists for dimeric Xanthomonas campestris PqqD (PDB ID: 3G2B), but PqqD is now known to act as a monomer under physiological conditions. In this study, the PqqD truncation from naturally fused Methylobacterium extorquens (Mex) PqqCD was overexpressed in Escherichia coli and MexPqqA was chemically synthesized. Solution NMR (1)H-,(15)N-HSQC chemical shift studies have identified the PqqD residues involved in binding PqqA, and (1)H, (13)C, and (15)N peak assignments for PqqD alone and for PqqD bound to PqqA are reported herein. PMID:27638737

  12. (1)H, (13)C, and (15)N resonance assignments and secondary structure information for Methylobacterium extorquens PqqD and the complex of PqqD with PqqA.

    PubMed

    Evans, Robert L; Latham, John A; Klinman, Judith P; Wilmot, Carrie M; Xia, Youlin

    2016-10-01

    The ribosomally synthesized and post-translationally modified peptide (RiPP), pyrroloquinoline quinone (PQQ), is a dehydrogenase cofactor synthesized by, but not exclusively used by, certain prokaryotes. RiPPs represent a rapidly expanding and diverse class of natural products-many of which have therapeutic potential-and the biosynthetic pathways for these are gaining attention. Five gene products from the pqq operon (PqqA, PqqB, PqqC, PqqD, and PqqE) are essential for PQQ biosynthesis. The substrate is the peptide PqqA, which is presented to the radical SAM enzyme PqqE by the small protein PqqD. PqqA is unstructured in solution, and only binds to PqqE when in complex with PqqD. PqqD is a member of a growing family of RiPP chaperone proteins (or domains in most cases) that present their associated peptide substrates to the initial RiPP biosynthesis enzymes. An X-ray crystal structure exists for dimeric Xanthomonas campestris PqqD (PDB ID: 3G2B), but PqqD is now known to act as a monomer under physiological conditions. In this study, the PqqD truncation from naturally fused Methylobacterium extorquens (Mex) PqqCD was overexpressed in Escherichia coli and MexPqqA was chemically synthesized. Solution NMR (1)H-,(15)N-HSQC chemical shift studies have identified the PqqD residues involved in binding PqqA, and (1)H, (13)C, and (15)N peak assignments for PqqD alone and for PqqD bound to PqqA are reported herein.

  13. Post-translational heterocyclic backbone modifications in the 43-peptide antibiotic microcin B17. Structure elucidation and NMR study of a 13C,15N-labelled gyrase inhibitor.

    PubMed

    Bayer, A; Freund, S; Jung, G

    1995-12-01

    Microcin B17 (McB17), the first known gyrase inhibitor of peptidic nature, is produced by ribosomal synthesis and post-translational modification of the 69-residue precursor protein by an Escherichia coli strain. To elucidate the chemical structure of the mature 43-residue peptide antibiotic, fermentation and purification protocols were established and optimized which allowed the isolation and purification of substantial amounts of highly pure McB17 (non-labelled, 15N-labelled and 13C/15N-labelled peptide. By ultraviolet-absorption spectroscopy. HPLC-electrospray mass spectrometry and GC-mass spectrometry, amino acid analysis, protein sequencing, and, in particular, multidimensional NMR, we could demonstrate and unequivocally prove that the enzymic modification of the precursor backbone at Gly-Cys and Gly-Ser segments leads to the formation of 2-aminomethylthiazole-4-carboxylic acid and 2-aminomethyloxazole-4-carboxylic acid, respectively. In addition, two bicyclic modifications 2-(2-aminomethyloxazolyl)thiazole-4-carboxylic acid and 2-(2-aminomethylthiazolyl)oxazole-4-carboxylic acid were found that consist of directly linked thiazole and oxazole rings derived from one Gly-Ser-Cys and one Gly-Cys-Ser segment. Analogous to the thiazole and oxazole rings found in antitumor peptides of microbial and marine origin, these heteroaromatic ring systems of McB17 presumably play an important role in its gyrase-inhibiting activity, e.g. interacting with the DNA to trap the covalent protein-DNA intermediate of the breakage-reunion reaction of the gyrase.

  14. Characterization of uniformly and atom-specifically 13C-labeled heparin and heparan sulfate polysaccharide precursors using 13C NMR spectroscopy and ESI mass spectrometry

    PubMed Central

    Nguyen, Thao K. N.; Tran, Vy M.; Victor, Xylophone V.; Skalicky, Jack J.; Kuberan, Balagurunathan

    2010-01-01

    The biological actions of heparin and heparan sulfate, two structurally related glycosaminoglycans, depend on the organization of the complex heparanome. Due to the structural complexity of the heparanome, the sequence of variably sulfonated uronic acid and glucosamine residues is usually characterized by the analysis of smaller oligosaccharide and disaccharide fragments. Even characterization of smaller heparin/heparan sulfate oligosaccharide or disaccharide fragments using simple 1D 1H NMR spectroscopy is often complicated by the extensive signal overlap. 13C NMR signals, on the other hand, overlap less and therefore, 13C NMR spectroscopy can greatly facilitate the structural elucidation of the complex heparanome and provide finer insights into the structural basis for biological functions. This is the first report of the preparation of anomeric carbon-specific 13C-labeled heparin/heparan sulfate precursors from the Escherichia coli K5 strain. Uniformly 13C- and 15N-labeled precursors were also produced and characterized by 13C NMR spectroscopy. Mass spectrometric analysis of enzymatically fragmented disaccharides revealed that anomeric carbon-specific labeling efforts resulted in a minor loss/scrambling of 13C in the precursor backbone, whereas uniform labeling efforts resulted in greater than 95% 13C isotope enrichment in the precursor backbone. These labeled precursors provided high-resolution NMR signals with great sensitivity and set the stage for studying the heparanome–proteome interactions. PMID:20832774

  15. The first organic-templated vanadyl(IV) gallophosphates with ambient (51)V hyperfine structure, {V(2)Ga(2)O(14)} cluster or heterometal 12-ring channels.

    PubMed

    Huang, Li-Hsun; Lai, Yi-Chun; Lai, Hui-Chun; Chiang, Yun-Wei; Huang, Jin-Hua; Wang, Sue-Lein

    2009-12-21

    Three new vanadyl gallium phosphates, (H(2)dap)(3)[(VO)(2)(GaO)(2)(PO(4))(4)].H(2)O (1), (H(2)dap)(1.5)[(VO)(2)(GaO)(2)(PO(4))(3)].3H(2)O (2), and (H(2)dap)[(VO)(2)Ga(4)(PO(4))(6)(H(2)O)(4)].2H(2)O (3) (dap = 1,3-diaminopropane), have been prepared under mild solvothermal conditions and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, magnetic susceptibility, and EPR spectroscopy. They are the first examples of an organic/V(4+)/Ga/P/O system that displays three different dimensional structures with a common template. The 1D chain structure of 1 and the 2D layered 2 are both built up with a PO(4) and {V(2)Ga(2)O(14)} cluster which contains a syn-square pyramidal {V(2)O(8)} dimer and two GaO(4) tetrahedra. The tetrameric cluster and V-O-Ga therein are observed in a metal phosphate system. Compound 3 is composed of VO(5)(H(2)O) octahedra, GaO(4)(H(2)O) trigonal bipyramids, and GaO(4) and PO(4) tetrahedra from which a unique 3D structure containing one-dimensional 12-ring channels is constructed. The channel aperture uncommonly comprises heterometal (V, Ga) polyhedra. Magnetic susceptibility data for 1-3 are consistent with V(4+) and show a T(N) of 12 K for 3. The unusual syn-{V(2)O(8)} dimers in 1 and 2 induce superexchange interactions, while isolated VO(5)(H(2)O) octahedra in 3 display super-super-exchange interaction. Electron paramagnetic resonance spectra with (51)V hyperfine structures were distinctly observed at 300 K for 1, while they started emerging at 30 K for 2 and 7 K for 3. The average hyperfine constant, 85.56 Gauss, was obtained via spectral simulations and nonlinear least-squares fittings for 1 and 2. Crystal data for 1 are triclinic, P1, a = 9.1754(4) A, b = 10.7853(5) A, c = 15.6519(7) A, alpha = 93.251(1) degrees , beta = 92.530(1) degrees , gamma = 95.106(1) degrees , V = 1538.4(1) A(3), and Z = 2; for 2, monoclinic, P2(1)/n, a = 8.9195(3) A, b = 14.6374(5) A, c = 17.8608(6) A, beta = 97.272(1) degrees , V = 2313

  16. The hyperfine structure in the rotational spectra of D{sub 2}{sup 17}O and HD{sup 17}O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen

    SciTech Connect

    Puzzarini, Cristina Cazzoli, Gabriele; Harding, Michael E.; Vázquez, Juana; Gauss, Jürgen

    2015-03-28

    Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing {sup 17}O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined {sup 17}O spin-rotation constants of D{sub 2}{sup 17}O and HD{sup 17}O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H{sub 2}{sup 17}O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)].

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

    SciTech Connect

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

    2014-09-21

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

  18. The optical depth of the 158 micrometer (C-12 II) line: Detection of the F=1 yields 0 (C-13 III) hyperfine-structure component

    NASA Technical Reports Server (NTRS)

    Stacey, G. J.; Townes, C. H.; Poglitsch, A.; Madden, S. C.; Jackson, J. M.; Herrmann, F.; Genzel, R.; Geis, N.

    1991-01-01

    The first detection of the F = 1 yields 0 hyperfine component of the 158 micrometer (C-13 II) fine structure line in the interstellar medium is reported. A twelve point intensity map was obtained of the (C-13 II) distribution over the inner 190 inch (right ascension) by 190 inch (declination) regions of the Orion nebula using an imaging Fabry-Perot interferometer. The (C-12 II)/(C-13 II) line intensity ratio varied significantly over the region mapped. It is highest (86 plus or minus 9) in the core of the Orion H II region and significantly lower (62 plus or minus 7) in the outer regions of the map, reflecting higher optical depth in the (C-12 II) line here. It is suggested that this enhanced optical depth is the result of limb brightening of the optically thin (C-13 II) line at the edges of the bowl-shaped H II region blister. If the C-12/C-13 abundance ratio is 43, the (C-12 II) line in the inner regions of the Orion nebula, has a low optical depth: tau sub 12 approximately = 0.75 plus or minus 0.25. The optical depth together with the large brightness temperature of the (C-12 II) line (approximately 160 K) requires that the excitation temperature of the P-2 sub 3/2 level be approximately 310 K, in very good agreement with the previous analysis of the physical conditions of the Orion interface region based on fine structure line intensity ratios and photodissociation region models. If the C-12/C-13 abundance ratio is 67, the line optical depth is somewhat larger (tau sub 12 approximately = 1.85), and the transition excitation temperature is somewhat smaller (approximately 190 K) than that predicted by these models. The present results therefore support values approximately = 43 for the C-12/C-13 abundance ratio in the Orion nebula.

  19. Participation of the surface structure of Pharaonis phoborhodopsin, ppR and its A149S and A149V mutants, consisting of the C-terminal alpha-helix and E-F loop, in the complex-formation with the cognate transducer pHtrII, as revealed by site-directed 13C solid-state NMR.

    PubMed

    Kawamura, Izuru; Ikeda, Yoichi; Sudo, Yuki; Iwamoto, Masayuki; Shimono, Kazumi; Yamaguchi, Satoru; Tuzi, Satoru; Saitô, Hazime; Kamo, Naoki; Naito, Akira

    2007-01-01

    We have recorded 13C solid state NMR spectra of [3-13C]Ala-labeled pharaonis phoborhodopsin (ppR) and its mutants, A149S and A149V, complexed with the cognate transducer pharaonis halobacterial transducer II protein (pHtrII) (1-159), to gain insight into a possible role of their cytoplasmic surface structure including the C-terminal alpha-helix and E-F loop for stabilization of the 2:2 complex, by both cross-polarization magic angle spinning (CP-MAS) and dipolar decoupled (DD)-MAS NMR techniques. We found that 13C CP-MAS NMR spectra of [3-13C]Ala-ppR, A149S and A149V complexed with the transducer pHtrII are very similar, reflecting their conformation and dynamics changes caused by mutual interactions through the transmembrane alpha-helical surfaces. In contrast, their DD-MAS NMR spectral features are quite different between [3-13C]Ala-A149S and A149V in the complexes with pHtrII: 13C DD-MAS NMR spectrum of [3-13C]Ala-A149S complex is rather similar to that of the uncomplexed form, while the corresponding spectral feature of A149V complex is similar to that of ppR complex in the C-terminal tip region. This is because more flexible surface structure detected by the DD-MAS NMR spectra are more directly influenced by the dynamics changes than the CP-MAS NMR. It turned out, therefore, that an altered surface structure of A149S resulted in destabilized complex as viewed from the 13C NMR spectrum of the surface areas, probably because of modified conformation at the corner of the helix E in addition to the change of hydropathy. It is, therefore, concluded that the surface structure of ppR including the C-terminal alpha-helix and the E-F loops is directly involved in the stabilization of the complex through conformational stability of the helix E.

  20. Optoacoustic 13C-breath test analyzer

    NASA Astrophysics Data System (ADS)

    Harde, Hermann; Helmrich, Günther; Wolff, Marcus

    2010-02-01

    The composition and concentration of exhaled volatile gases reflects the physical ability of a patient. Therefore, a breath analysis allows to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter pylori in the stomach wall as an indication of a gastric ulcer. In this contribution we present a new optical analyzer that employs a compact and simple set-up based on photoacoustic spectroscopy. It consists of two identical photoacoustic cells containing two breath samples, one taken before and one after capturing an isotope-marked substrate, where the most common isotope 12C is replaced to a large extent by 13C. The analyzer measures simultaneously the relative CO2 isotopologue concentrations in both samples by exciting the molecules on specially selected absorption lines with a semiconductor laser operating at a wavelength of 2.744 μm. For a reliable diagnosis changes of the 13CO2 concentration of 1% in the exhaled breath have to be detected at a concentration level of this isotope in the breath of about 500 ppm.

  1. Temperature dependence of the hyperfine interaction at

    SciTech Connect

    Lopez-Garcia, Alberto; de la Presa, Patricia; Ayala, Alejandro

    2001-06-01

    The temperature dependence of the quadrupole hyperfine parameters covering the temperature range from 293 to 1173 K was measured at {sup 181}Ta probes in SrHfO{sub 3} by perturbed angular correlation spectroscopy. A fluctuating distribution of quadrupole interactions model was applied to interpret the data. At low temperatures above {approximately}300 K a static, asymmetric, and distributed electric quadrupole interaction was detected. At intermediate temperatures ({approx}600 K) a different quadrupole interaction appears, characterized by a fluctuating distribution of axially symmetric electric field gradient tensors. Above 873 K, the unique presence of a nuclear spin relaxation mechanism shows a second change in the perturbation acting on probes. These changes in the hyperfine interaction are consistent with the structural phase transitions detected by diffraction techniques. The probe effects were also analyzed, comparing {sup 181}Ta with {sup 111}Cd experiments.

  2. A method for simultaneous echo planar imaging of hyperpolarized 13C pyruvate and 13C lactate

    NASA Astrophysics Data System (ADS)

    Reed, Galen D.; Larson, Peder E. Z.; von Morze, Cornelius; Bok, Robert; Lustig, Michael; Kerr, Adam B.; Pauly, John M.; Kurhanewicz, John; Vigneron, Daniel B.

    2012-04-01

    A rapid echo planar imaging sequence for dynamic imaging of [1-13C] lactate and [1-13C] pyruvate simultaneously was developed. Frequency-based separation of these metabolites was achieved by spatial shifting in the phase-encoded direction with the appropriate choice of echo spacing. Suppression of the pyruvate-hydrate and alanine resonances is achieved through an optimized spectral-spatial RF waveform. Signal sampling efficiency as a function of pyruvate and lactate excitation angle was simulated using two site exchange models. Dynamic imaging is demonstrated in a transgenic mouse model, and phantom validations of the RF pulse frequency selectivity were performed.

  3. Synthesis of [1-.sup.13C]pyruvic acid], [2-.sup.13C]pyruvic acid], [3-.sup.13C]pyruvic acid] and combinations thereof

    DOEpatents

    Martinez, Rodolfo A.; Unkefer, Clifford J.; Alvarez, Marc A.

    2009-09-01

    The present invention is directed to labeled compounds, of the formulae ##STR00001## wherein C* is each independently selected from the group consisting of .sup.13C and .sup.12C with the proviso that at least one C* is .sup.13C, each hydrogen of the methylene group can independently be either hydrogen or deuterium, the methyl group includes either zero or three deuterium atoms, Q is from the group of sulfide, sulfinyl, and sulfone, Z is an aryl group from the group of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently from the group of hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group from the group of NH.sub.2, NHR and NRR' where R and R' are each independently from the group of a C.sub.1-C.sub.4 lower alkyl, a phenyl, and an alkoxy group, and the methyl group can include either zero or three deuterium atoms.

  4. Synthesis Of 2h- And 13c-Substituted Dithanes

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2004-05-04

    The present invention is directed to labeled compounds, [2-.sup.13 C]dithane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-.sup.13 C]dithane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [.sup.2 H.sub.1-2, .sup.13 C]methanol (arylthio)-, acetates wherein the .sup.13 C atom is directly bonded to exactly one or two deuterium atoms.

  5. Synthesis of 2H- and 13C-substituted dithanes

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2003-01-01

    The present invention is directed to labeled compounds, [2-.sup.13 C]dithiane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-.sup.13 C]dithiane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [.sup.2 H.sub.1-2, .sup.13 C]methanol (arylthio)-, acetates wherein the .sup.13 C atom is directly bonded to exactly one or two deuterium atoms.

  6. Calculation of total meal d13C from individual food d13C.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Variations in the isotopic signature of carbon in biological samples can be used to distinguish dietary patterns and monitor shifts in metabolism. But for these variations to have meaning, the isotopic signature of the diet must be known. We sought to determine if knowledge of the 13C isotopic abund...

  7. In vivo dynamic turnover of cerebral 13C isotopomers from [U- 13C]glucose

    NASA Astrophysics Data System (ADS)

    Xu, Su; Shen, Jun

    2006-10-01

    An INEPT-based 13C MRS method and a cost-effective and widely available 11.7 Tesla 89-mm bore vertical magnet were used to detect dynamic 13C isotopomer turnover from intravenously infused [U- 13C]glucose in a 211 μL voxel located in the adult rat brain. The INEPT-based 1H → 13C polarization transfer method is mostly adiabatic and therefore minimizes signal loss due to B 1 inhomogeneity of the surface coils used. High quality and reproducible data were acquired as a result of combined use of outer volume suppression, ISIS, and the single-shot three-dimensional localization scheme built in the INEPT pulse sequence. Isotopomer patterns of both glutamate C4 at 34.00 ppm and glutamine C4 at 31.38 ppm are dominated first by a doublet originated from labeling at C4 and C5 but not at C3 (with 1JC4C5 = 51 Hz) and then by a quartet originated from labeling at C3, C4, and C5 (with 1JC3C4 = 35 Hz). A lag in the transition of glutamine C4 pattern from doublet-dominance to quartet dominance as compared to glutamate C4 was observed, which provides an independent verification of the precursor-product relationship between neuronal glutamate and glial glutamine and a significant intercompartmental cerebral glutamate-glutamine cycle between neurons and glial cells.

  8. Determination of the hyperfine magnetic field in magnetic carbon-based materials: DFT calculations and NMR experiments

    PubMed Central

    Freitas, Jair C. C.; Scopel, Wanderlã L.; Paz, Wendel S.; Bernardes, Leandro V.; Cunha-Filho, Francisco E.; Speglich, Carlos; Araújo-Moreira, Fernando M.; Pelc, Damjan; Cvitanić, Tonči; Požek, Miroslav

    2015-01-01

    The prospect of carbon-based magnetic materials is of immense fundamental and practical importance, and information on atomic-scale features is required for a better understanding of the mechanisms leading to carbon magnetism. Here we report the first direct detection of the microscopic magnetic field produced at 13C nuclei in a ferromagnetic carbon material by zero-field nuclear magnetic resonance (NMR). Electronic structure calculations carried out in nanosized model systems with different classes of structural defects show a similar range of magnetic field values (18–21 T) for all investigated systems, in agreement with the NMR experiments. Our results are strong evidence of the intrinsic nature of defect-induced magnetism in magnetic carbons and establish the magnitude of the hyperfine magnetic field created in the neighbourhood of the defects that lead to magnetic order in these materials. PMID:26434597

  9. Dipolar-coupling-mediated total correlation spectroscopy in solid-state 13C NMR: Selection of individual 13C- 13C dipolar interactions

    NASA Astrophysics Data System (ADS)

    Spano, Justin; Wi, Sungsool

    2010-06-01

    Herein is described a useful approach in solid-state NMR, for selecting homonuclear 13C- 13C spin pairs in a multiple- 13C homonuclear dipolar coupled spin system. This method builds upon the zero-quantum (ZQ) dipolar recoupling method introduced by Levitt and coworkers (Marin-Montesinos et al., 2006 [30]) by extending the originally introduced one-dimensional (1D) experiment into a two-dimensional (2D) method with selective irradiation scheme, while moving the 13C- 13C mixing scheme from the transverse to the longitudinal mode, together with a dramatic improvement in the proton decoupling efficiency. Selective spin-pair recoupling experiments incorporating Gaussian and cosine-modulated Gaussian pulses for inverting specific spins were performed, demonstrating the ability to detect informative, simplified/individualized, long-range 13C- 13C homonuclear dipolar coupling interactions more accurately by removing less informative, stronger, short-range 13C- 13C interactions from 2D correlation spectra. The capability of this new approach was demonstrated experimentally on uniformly 13C-labeled Glutamine and a tripeptide sample, GAL.

  10. Hyperfine excitation of OH+ by H

    NASA Astrophysics Data System (ADS)

    Lique, François; Bulut, Niyazi; Roncero, Octavio

    2016-10-01

    The OH+ ions are widespread in the interstellar medium and play an important role in the interstellar chemistry as they act as precursors to the H2O molecule. Accurate determination of their abundance rely on their collisional rate coefficients with atomic hydrogen and electrons. In this paper, we derive OH+-H fine and hyperfine-resolved rate coefficients by extrapolating recent quantum wave packet calculations for the OH+ + H collisions, including inelastic and exchange processes. The extrapolation method used is based on the infinite order sudden approach. State-to-state rate coefficients between the first 22 fine levels and 43 hyperfine levels of OH+ were obtained for temperatures ranging from 10 to 1000 K. Fine structure-resolved rate coefficients present a strong propensity rule in favour of Δj = ΔN transitions. The Δj = ΔF propensity rule is observed for the hyperfine transitions. The new rate coefficients will help significantly in the interpretation of OH+ spectra from photon-dominated region (PDR), and enable the OH+ molecule to become a powerful astrophysical tool for studying the oxygen chemistry.

  11. Electron spin resonance investigations of /sup 11/B/sup 12/C, /sup 11/B/sup 13/C, and /sup 10/B/sup 12/C in neon, argon, and krypton matrices at 4 K: Comparison with theoretical results

    SciTech Connect

    Knight L.B. Jr.; Cobranchi, S.T.; Petty, J.T.; Earl, E.; Feller, D.; Davidson, E.R.

    1989-01-15

    The first spectroscopic study of the diatomic radical BC is reported which confirms previous theoretical predictions of a /sup 4/summation/sup -/ electronic ground state. The nuclear hyperfine interactions (A tensors) obtained for /sup 11/B, /sup 10/B, and /sup 13/C from the electron spin resonance (ESR) measurements are compared with extensive ab initio CI calculations. The BC molecule is one of the first examples of a small high spin radical for such an in-depth experimental--theoretical comparison. The electronic structure of BC obtained from an analysis of the nuclear hyperfine interaction (hfi) is compared to that obtained from a Mulliken-type population analysis conducted on a CI wave function which yields A/sub iso/ and A/sub dip/ results in good agreement with the observed values. The BC radical was generated by the laser vaporization of a boron--carbon mixture and trapped in neon, argon, and krypton matrices at 4 K for a complete ESR characterization. The magnetic parameters (MHz) obtained for /sup 11/B/sup 13/C in solid neon are: g/sub parallel/ = 2.0015(3); g/sub perpendicular/ = 2.0020(3); D(zfs) = 1701(2); /sup 11/B: chemically bondA/sub parallel/chemically bond = 100(1); chemically bondA/sub perpendicular/chemically bond = 79(1); /sup 13/C: chemically bondA/sub parallel/chemically bond = 5(2) and chemically bondA/sub perpendicular/chemically bond = 15(1). Based on comparison with the theoretical results, the most likely choice of signs is that all A values are positive.

  12. The 13C nuclear magnetic resonance in graphite intercalation compounds

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Resing, H. A.

    1985-01-01

    The (13)C NMR chemical shifts of graphite intercalation compounds were calculated. For acceptor types, the shifts come mainly from the paramagnetic (Ramsey) intra-atomic terms. They are related to the gross features of the two-dimensional band structures. The calculated anisotropy is about -140 ppm and is independent of the finer details such as charge transfer. For donor types, the carbon 2p pi orbitals are spin-polarized because of mixing with metal conduction electrons, thus there is an additional dipolar contribution which may be correlated with the electronic specific heat. The general agreement with experimental data is satisfactory.

  13. Precise measurement of hyperfine structure in the 2P{sub 1/2} state of {sup 7}Li using saturated-absorption spectroscopy

    SciTech Connect

    Singh, Alok K.; Muanzuala, Lal; Natarajan, Vasant

    2010-10-15

    We report a precise measurement of the hyperfine interval in the 2P{sub 1/2} state of {sup 7}Li. The transition from the ground state (D{sub 1} line) is accessed using a diode laser and the technique of saturated-absorption spectroscopy in hot Li vapor. The interval is measured by locking an acousto-optic modulator to the frequency difference between the two hyperfine peaks. The measured interval of 92.040(6) MHz is consistent with an earlier measurement reported by us using an atomic-beam spectrometer [Das and Natarajan, J. Phys. B 41, 035001 (2008)]. The interval yields the magnetic dipole constant in the P{sub 1/2} state as A=46.047(3), which is discrepant from theoretical calculations by >80 kHz.

  14. Quantum mechanical study of the structure and spectroscopic (FT-IR, FT-Raman, 13C, 1H and UV), NBO and HOMO-LUMO analysis of 2-quinoxaline carboxylic acid

    NASA Astrophysics Data System (ADS)

    Prabavathi, N.; Nilufer, A.; Krishnakumar, V.

    The FTIR and FT-Raman spectra of 2-quinoxaline carboxylic acid (2-QCA) has been recorded in the region 4000-450 and 4000-100 cm-1, respectively. The conformational analysis, optimized geometry, frequency and intensity of the vibrational bands of 2-QCA were obtained by the density functional theory (DFT) with complete relaxation in the potential energy surface using 6-31G(d) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The 1H and13C NMR spectra have been recorded and 1H and 13C nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method and their respective linear correlations were obtained. The theoretical UV-visible spectrum of the compound using CIS method and the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The Mulliken charges, the values of electric dipole moment (μ) of the molecule were computed using DFT calculations. The change in electron density (ED) in the σ* antibonding orbitals and stabilization energies E(2) have been calculated by natural bond (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen-bonded interactions.

  15. The structure of heparin oligosaccharide fragments with high anti-(factor Xa) activity containing the minimal antithrombin III-binding sequence. Chemical and 13C nuclear-magnetic-resonance studies.

    PubMed Central

    Casu, B; Oreste, P; Torri, G; Zoppetti, G; Choay, J; Lormeau, J C; Petitou, M; Sinäy, P

    1981-01-01

    The chemical composition and the 13C n.m.r. spectra of heparin oligosaccharides (essentially octasaccharides), having high affinity for antithrombin III and high anti-(Factor Xa) activity, prepared by three independent approaches (extraction, partial deaminative cleavage with HNO2 and partial depolymerization with bacterial heparinase), leading to different terminal residues, have been studied and compared with those of the corresponding inactive species. Combined wit chemical data, the spectra of the active oligosaccharides and of their fragmentation products afforded information on composition and sequence. The three types of active oligosaccharides were shown to have the common hexasaccharide core I-Aa-G-As*-Is-As, where I and alpha-L-idopyranosyl-uronic acid, Aa = 2-acetamido-2-deoxy-alpha-D-glucopyranose, G = beta-D-glucopyranosyl-uronic acid, Is = alpha-L-idopyranosyluronic acid 2-O-sulphate, As = 2-deoxy-2-sulphamino-alpha-D-glucopyranose 6-O-sulphate. The fourth residue (As*) is an unusually substituted amino sugar resistant to mild deamination. The 13C spectra of the active species are characterized by signals from the above atypical amino sugar, the most evident of which is at 57.7 p.p.m. These signals, compared with those of appropriate synthetic model compounds, are compatible with the recently proposed 3-O-sulphation of the residue As* [Lindahl, Bäckström, Thunberg & Leder (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 6551-6555]. PMID:7325974

  16. Overexpression of a homogeneous oligosaccharide with 13C labeling by genetically engineered yeast strain.

    PubMed

    Kamiya, Yukiko; Yamamoto, Sayoko; Chiba, Yasunori; Jigami, Yoshifumi; Kato, Koichi

    2011-08-01

    This report describes a novel method for overexpression of (13)C-labeled oligosaccharides using genetically engineered Saccharomyces cerevisiae cells, in which a homogeneous high-mannose-type oligosaccharide accumulates because of deletions of genes encoding three enzymes involved in the processing pathway of asparagine-linked oligosaccharides in the Golgi complex. Using uniformly (13)C-labeled glucose as the sole carbon source in the culture medium of these engineered yeast cells, high yields of the isotopically labeled Man(8)GlcNAc(2) oligosaccharide could be successfully harvested from glycoprotein extracts of the cells. Furthermore, (13)C labeling at selected positions of the sugar residues in the oligosaccharide could be achieved using a site-specific (13)C-enriched glucose as the metabolic precursor, facilitating NMR spectral assignments. The (13)C-labeling method presented provides the technical basis for NMR analyses of structures, dynamics, and interactions of larger, branched oligosaccharides.

  17. Refined Analysis of Brain Energy Metabolism Using In Vivo Dynamic Enrichment of 13C Multiplets

    PubMed Central

    Dehghani M., Masoumeh; Duarte, João M. N.; Kunz, Nicolas; Gruetter, Rolf

    2016-01-01

    Carbon-13 nuclear magnetic resonance spectroscopy in combination with the infusion of 13C-labeled precursors is a unique approach to study in vivo brain energy metabolism. Incorporating the maximum information available from in vivo localized 13C spectra is of importance to get broader knowledge on cerebral metabolic pathways. Metabolic rates can be quantitatively determined from the rate of 13C incorporation into amino acid neurotransmitters such as glutamate and glutamine using suitable mathematical models. The time course of multiplets arising from 13C-13C coupling between adjacent carbon atoms was expected to provide additional information for metabolic modeling leading to potential improvements in the estimation of metabolic parameters. The aim of the present study was to extend two-compartment neuronal/glial modeling to include dynamics of 13C isotopomers available from fine structure multiplets in 13C spectra of glutamate and glutamine measured in vivo in rats brain at 14.1 T, termed bonded cumomer approach. Incorporating the labeling time courses of 13C multiplets of glutamate and glutamine resulted in elevated precision of the estimated fluxes in rat brain as well as reduced correlations between them. PMID:26969691

  18. Dynamic nuclear polarization-enhanced 13C NMR spectroscopy of static biological solids

    NASA Astrophysics Data System (ADS)

    Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

    2013-06-01

    We explore the possibility of using dynamic nuclear polarization (DNP) to enhance signals in structural studies of biological solids by solid state NMR without sample spinning. Specifically, we use 2D 13C-13C exchange spectroscopy to probe the peptide backbone torsion angles (ϕ, ψ) in a series of selectively 13C-labeled 40-residue β-amyloid (Aβ1-40) samples, in both fibrillar and non-fibrillar states. Experiments are carried out at 9.39 T and 8 K, using a static double-resonance NMR probe and low-power microwave irradiation at 264 GHz. In frozen solutions of Aβ1-40 fibrils doped with DOTOPA-TEMPO, we observe DNP signal enhancement factors of 16-21. We show that the orientation- and frequency-dependent spin polarization exchange between sequential backbone carbonyl 13C labels can be simulated accurately using a simple expression for the exchange rate, after experimentally determined homogeneous 13C lineshapes are incorporated in the simulations. The experimental 2D 13C-13C exchange spectra place constraints on the ϕ and ψ angles between the two carbonyl labels. Although the data are not sufficient to determine ϕ and ψ uniquely, the data do provide non-trivial constraints that could be included in structure calculations. With DNP at low temperatures, 2D 13C-13C exchange spectra can be obtained from a 3.5 mg sample of Aβ1-40 fibrils in 4 h or less, despite the broad 13C chemical shift anisotropy line shapes that are observed in static samples.

  19. Dynamic nuclear polarization-enhanced 13C NMR spectroscopy of static biological solids

    PubMed Central

    Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

    2013-01-01

    We explore the possibility of using dynamic nuclear polarization (DNP) to enhance signals in structural studies of biological solids by solid state NMR without sample spinning. Specifically, we use 2D 13C-13C exchange spectroscopy to probe the peptide backbone torsion angles (ϕ,ψ) in a series of selectively 13C-labeled 40-residue β-amyloid (Aβ1–40) samples, in both fibrillar and non-fibrillar states. Experiments are carried out at 9.39 T and 8 K, using a static double-resonance NMR probe and low-power microwave irradiation at 264 GHz. In frozen solutions of Aβ1–40 fibrils doped with DOTOPA-TEMPO, we observe DNP signal enhancement factors of 16–21. We show that the orientation- and frequency-dependent spin polarization exchange between sequential backbone carbonyl 13C labels can be simulated accurately using a simple expression for the exchange rate, after experimentally determined homogeneous 13C lineshapes are incorporated in the simulations. The experimental 2D 13C-13C exchange spectra place constraints on the ϕ and ψ angles between the two carbonyl labels. Although the data are not sufficient to determine ϕ and ψ uniquely, the data do provide non-trivial constraints that could be included in structure calculations. With DNP at low temperatures, 2D 13C-13C exchange spectra can be obtained from a 3.5 mg sample of Aβ1–40 fibrils in 4 hr or less, despite the broad 13C chemical shift anisotropy line shapes that are observed in static samples. PMID:23562665

  20. 13C isotopic fractionation during biodegradation of agricultural wastes.

    PubMed

    Chalk, Phillip M; Inácio, Caio T; Urquiaga, Segundo; Chen, Deli

    2015-01-01

    Significant differences in δ(13)C signatures occur within and between plant tissues and their constituent biochemical entities, and also within and between heterotrophic bacteria and fungi and their metabolic products. Furthermore, (13)C isotopic fractionation occurs during the biodegradation of organic molecules as seen in the substrate, respired CO(2) and the microbial biomass, which could be related to substrate composition and/or microbial metabolism. The (13)C isotopic fractionation observed during the decomposition of a single defined C substrate appears to be due to the intra-molecular heterogeneity in (13)C in the substrate and to (13)C isotopic fractionation during microbial metabolism. Very limited data suggest that the latter may be quantitatively more important than the former. Studies with defined fungi in culture media have highlighted the complexities associated with the interpretation of the observed patterns of (13)C isotopic fractionation when a single defined C source is added to the culture medium which itself contains one or more C sources. Techniques involving (13)C enrichment or paired treatments involving an equivalent C(3)- and C(4)-derived substrate have been devised to overcome the problem of background C in the culture medium and (13)C isotopic fractionation during metabolism. Studies with complex substrates have shown an initial (13)C depletion phase in respired CO(2) followed by a (13)C enrichment phase which may or may not be followed by another (13)C depletion phase. Basic studies involving an integrated approach are required to gain a new insight into (13)C isotopic fractionation during organic residue decomposition, by simultaneous measurements of δ(13)C in all C moieties. New analytical tools to measure real-time changes in δ(13)CO(2) and the intra-molecular δ(13)C distribution within plant biochemical entities offer new opportunities for unravelling the complex interactions between substrate and microbial metabolism with

  1. Effect of particle size distribution on the structure, hyperfine, and magnetic properties of Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nanopowders

    SciTech Connect

    Bhattacharjee, Kaustav; Das, G. C.; Pati, Satya P.; Das, D.

    2014-12-21

    Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nano powders were synthesized by an auto combustion method and then heat treated at different temperatures in air for a fixed time. As a consequence, a distribution in particle size and strain was incorporated within the specimens, as estimated from the Rietveld refinement analysis of the powder x-ray diffraction data. The changes in the microstructure and crystal structure parameters were carefully extracted through the refinement analysis. Thermal annealing causes increment in the dispersion and mean of the size distribution. Reallocation of cations in the lattice sites occur as a consequence of the heat treatment which was manifested in their altered unit cell length (a), r.m.s. strain (〈ε{sup 2}〉{sup 1/2}), oxygen positional parameter (u), metal-oxygen bond lengths (R{sub OA} and R{sub OB}), and the band positions (ν{sub 1}and ν{sub 2}) in the vibrational spectroscopy. We also investigate the hyperfine and magnetic properties of the samples using different instrumental techniques (with different operating time scales) like Mössbauer spectroscopy, electron paramagnetic resonance spectroscopy, and superconducting quantum interference device magnetometry. Results show that the effect of particle size distribution was manifested in their hyperfine field distribution profile, paramagnetic resonance spectra, and magnetic anisotropy energy distribution profile. Co-existence of superparamagnetic and ferrimagnetic phase was recorded at room temperature in the samples when annealed at lower temperature. However, with increase in annealing temperature, the nature of the size distribution changes and ferrimagnetic ordering predominates for the larger size nanoparticles. Thus, the effect of particle size distribution on the structural, hyperfine, and magnetic properties of various Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nanoparticles was investigated herein which hitherto has not been discussed in the literature.

  2. Nagaoka's atomic model and hyperfine interactions.

    PubMed

    Inamura, Takashi T

    2016-01-01

    The prevailing view of Nagaoka's "Saturnian" atom is so misleading that today many people have an erroneous picture of Nagaoka's vision. They believe it to be a system involving a 'giant core' with electrons circulating just outside. Actually, though, in view of the Coulomb potential related to the atomic nucleus, Nagaoka's model is exactly the same as Rutherford's. This is true of the Bohr atom, too. To give proper credit, Nagaoka should be remembered together with Rutherford and Bohr in the history of the atomic model. It is also pointed out that Nagaoka was a pioneer of understanding hyperfine interactions in order to study nuclear structure.

  3. Hyperfine structure of {sup 87,89}Sr 5s4d{sup 3}D-5snf transitions in collinear fast beam RIMS

    SciTech Connect

    Bushaw, B. A.; Kluge, H.-J.; Lantzsch, J.; Schwalbach, R.; Schwarz, M.; Stenner, J.; Stevens, H.; Wendt, K.; Zimmer, K.

    1995-04-01

    The title transition, with n=20, 23, and 32 were measured for stable {sup 87}Sr and the observed hfs was interpreted and strong hyperfine mixing of all four terms {sup 1}F3 and {sup 3}F2,3,4 in the upper configuration. The results of the analysis were used to predict the hfs for the radioactive isotope {sup 89}Sr. Measurement were then performed on samples containing 10{sup 9} atoms {sup 89}Sr. The positions and intensities of the hfs components selected for study were found to agree well with the predicted values.

  4. Observation of the hyperfine structure of the {sup 2}S{sub 1/2}-{sup 2}D{sub 5/2} transition in {sup 87}Sr{sup +}

    SciTech Connect

    Barwood, G.P.; Gao, K.; Gill, P.; Huang, G.; Klein, H.A.

    2003-01-01

    The hyperfine structure of the {sup 2}S{sub 1/2}-{sup 2}D{sub 5/2} quadrupole transition at 674 nm in {sup 87}Sr{sup +} has been observed. The ion was confined in a Paul trap and cooled using laser radiation at 422 and 1092 nm. The quadrupole transition was observed by monitoring quantum jumps in the 422-nm fluorescence. The odd isotope of strontium has 'clock' transitions independent of the first-order Zeeman shift and the {sup 2}D{sub 5/2} state hyperfine structure constants have been determined as A{sub D{sub 5/2}}=2.1743(14) MHz and B{sub D{sub 5/2}}=49.11(6) MHz. Standard uncertainties have been added in parentheses. These values allow the second-order Zeeman shifts to be calculated. The {sup 88}Sr{sup +}-{sup 87}Sr{sup +} isotope shift for the 674-nm quadrupole transition has been measured to be 247.99(4) MHz.

  5. Σ production from targets of ^4He and ^13C

    NASA Astrophysics Data System (ADS)

    Chrien, R. E.

    1996-10-01

    One of the abiding issues in hypernuclear research has been the question of the formation of nuclear bound states incorporating the Σ-hyperon. The recent increases in beam intensity at the Brookhaven AGS have enabled us to obtain a high statistics study on the production of Σ-hyperons on a ^4He target. Earlier research using stopped kaons at KEK indicated the presence of structure in the (K^-,π^-) reaction, and led to the postulate of a Σ bound state. That structure has now been definitely confirmed in the in-flight kaon experiment at the LESB2 beam line and Moby-Dick spectrometer. An improved measurement of the binding energy of the presumed state will be reported, together with a production cross section. In addition, both (K^-,π^-) and (K^-,π^+) reactions on ^13C have been studied and will be compared to similar measurements on ^9Be.

  6. 13C pulse-labeling assessment of the community structure of active fungi in the rhizosphere of a genetically starch-modified potato (Solanum tuberosum) cultivar and its parental isoline.

    PubMed

    Hannula, S E; Boschker, H T S; de Boer, W; van Veen, J A

    2012-05-01

    • The aim of this study was to gain understanding of the carbon flow from the roots of a genetically modified (GM) amylopectin-accumulating potato (Solanum tuberosum) cultivar and its parental isoline to the soil fungal community using stable isotope probing (SIP). • The microbes receiving (13)C from the plant were assessed through RNA/phospholipid fatty acid analysis with stable isotope probing (PLFA-SIP) at three time-points (1, 5 and 12 d after the start of labeling). The communities of Ascomycota, Basidiomycota and Glomeromycota were analysed separately with RT-qPCR and terminal restriction fragment length polymorphism (T-RFLP). • Ascomycetes and glomeromycetes received carbon from the plant as early as 1 and 5 d after labeling, while basidiomycetes were slower in accumulating the labeled carbon. The rate of carbon allocation in the GM variety differed from that in its parental variety, thereby affecting soil fungal communities. • We conclude that both saprotrophic and mycorrhizal fungi rapidly metabolize organic substrates flowing from the root into the rhizosphere, that there are large differences in utilization of root-derived compounds at a lower phylogenetic level within investigated fungal phyla, and that active communities in the rhizosphere differ between the GM plant and its parental cultivar through effects of differential carbon flow from the plant.

  7. Fock-space multireference coupled-cluster calculations of the hyperfine structure of isoelectronic {sup 33}S{sup -} and {sup 35,37}Cl

    SciTech Connect

    Das, Madhulita; Chaudhuri, Rajat K.; Chattopadhyay, Sudip; Mahapatra, Uttam Sinha

    2011-10-15

    Due to its flexibility and possible systematic improvement, the Fock-space (FS) multireference coupled-cluster (MRCC) method remains a very important tool for the computation of energy differences of spectroscopic interest. In the present work, the FS MRCC method for the electron detachment process has been applied to determine the magnetic hyperfine constant A{sub J} and nuclear quadrupole moments Q (related to electric hyperfine constant B{sub J}) for the lowest multiplets of {sup 33}S{sup -}, {sup 35}Cl, and {sup 37}Cl with Dirac-Fock orbitals. In addition, we also report {sup 2}P{sub 3/2}([Ne]3s{sup 2}3p{sup 5}) {yields} {sup 2}P{sub 1/2}([Ne]3s{sup 2}3p{sup 5}) magnetic dipole transition matrix element and electron affinity of {sup 35}Cl (i.e., ionization energy of Cl{sup -}). Calculated properties are in very good agreement with the available new standard or reference values.

  8. Clinical NOE 13C MRS for neuropsychiatric disorders of the frontal lobe

    NASA Astrophysics Data System (ADS)

    Sailasuta, Napapon; Robertson, Larry W.; Harris, Kent C.; Gropman, Andrea L.; Allen, Peter S.; Ross, Brian D.

    2008-12-01

    In this communication, a scheme is described whereby in vivo 13C MRS can safely be performed in the frontal lobe, a human brain region hitherto precluded on grounds of SAR, but important in being the seat of impaired cognitive function in many neuropsychiatric and developmental disorders. By combining two well known features of 13C NMR—the use of low power NOE and the focus on 13C carbon atoms which are only minimally coupled to protons, we are able to overcome the obstacle of SAR and develop means of monitoring the 13C fluxes of critically important metabolic pathways in frontal brain structures of normal volunteers and patients. Using a combination of low-power WALTZ decoupling, variants of random noise for nuclear overhauser effect enhancement it was possible to reduce power deposition to 20% of the advised maximum specific absorption rate (SAR). In model solutions 13C signal enhancement achieved with this scheme were comparable to that obtained with WALTZ-4. In human brain, the low power procedure effectively determined glutamine, glutamate and bicarbonate in the posterior parietal brain after [1- 13C] glucose infusion. The same 13C enriched metabolites were defined in frontal brain of human volunteers after administration of [1- 13C] acetate, a recognized probe of glial metabolism. Time courses of incorporation of 13C into cerebral glutamate, glutamine and bicarbonate were constructed. The results suggest efficacy for measurement of in vivo cerebral metabolic rates of the glutamate-glutamine and tricarboxylic acid cycles in 20 min MR scans in previously inaccessible brain regions in humans at 1.5T. We predict these will be clinically useful biomarkers in many human neuropsychiatric and genetic conditions.

  9. /sup 13/C nuclear magnetic resonance studies of cardiac metabolism

    SciTech Connect

    Seeholzer, S.H.

    1985-01-01

    The last decade has witnessed the increasing use of Nuclear Magnetic Resonance (NMR) techniques for following the metabolic fate of compounds specifically labeled with /sup 13/C. The goals of the present study are: (1) to develop reliable quantitative procedures for measuring the /sup 13/C enrichment of specific carbon sites in compounds enriched by the metabolism of /sup 13/C-labeled substrates in rat heart, and (2) to use these quantitative measurements of fractional /sup 13/C enrichment within the context of a mathematical flux model describing the carbon flow through the TCA cycle and ancillary pathways, as a means for obtaining unknown flux parameters. Rat hearts have been perfused in vitro with various combinations of glucose, acetate, pyruvate, and propionate to achieve steady state flux conditions, followed by perfusion with the same substrates labeled with /sup 13/C in specific carbon sites. The hearts were frozen at different times after addition of /sup 13/C-labeled substrates and neutralized perchloric acid extracts were used to obtain high resolution proton-decoupled /sup 13/C NMR spectra at 90.55 MHz. The fractional /sup 13/C enrichment (F.E.) of individual carbon sites in different metabolites was calculated from the area of the resolved resonances after correction for saturation and nuclear Overhauser effects. These F.E. measurements by /sup 13/C NMR were validated by the analysis of /sup 13/C-/sup 1/H scalar coupling patterns observed in /sup 1/H NMR spectra of the extracted metabolites. The results obtained from perfusion of hearts glucose plus either (2-/sup 13/C) acetate or (3-/sup 13/C) pyruvate are similar to those obtained by previous investigators using /sup 14/C-labeled substrates.

  10. Spectroscopic study of the cycling transition 4s[3/2]{sub 2}-4p[5/2]{sub 3} at 811.8 nm in {sup 39}Ar: Hyperfine structure and isotope shift

    SciTech Connect

    Williams, W.; Mueller, P.; Lu, Z.-T.; Rudinger, K.; Xu, C.-Y.; Yokochi, R.

    2011-01-15

    Doppler-free saturated absorption spectroscopy is performed on an enriched radioactive {sup 39}Ar sample. The spectrum of the 3s{sup 2}3p{sup 5}4s[3/2]{sub 2}-3s{sup 2}3p{sup 5}4p[5/2]{sub 3} cycling transition at 811.8 nm is recorded, and its isotope shift between {sup 39}Ar and {sup 40}Ar is derived. The hyperfine coupling constants A and B for both the 4s[3/2]{sub 2} and 4p[5/2]{sub 3} energy levels in {sup 39}Ar are also determined. The results partially disagree with a recently published measurement of the same transition. Based on earlier measurements as well as the current work, the isotope shift and hyperfine structure of the corresponding transition in {sup 37}Ar are also calculated. These spectroscopic data are essential for the realization of laser trapping and cooling of {sup 37,39}Ar.

  11. Triple resonance experiments for aligned sample solid-state NMR of 13C and 15N labeled proteins

    PubMed Central

    Sinha, Neeraj; Grant, Christopher V.; Park, Sang Ho; Brown, Jonathan Miles; Opella, Stanley J.

    2013-01-01

    Initial steps in the development of a suite of triple-resonance 1H/13C/15N solid-state NMR experiments applicable to aligned samples of 13C and 15N labeled proteins are described. The experiments take advantage of the opportunities for 13C detection without the need for homonuclear 13C/13C decoupling presented by samples with two different patterns of isotopic labeling. In one type of sample, the proteins are ~20% randomly labeled with 13C in all backbone and side chain carbon sites and ~100% uniformly 15N labeled in all nitrogen sites; in the second type of sample, the peptides and proteins are 13C labeled at only the α-carbon and 15N labeled at the amide nitrogen of a few residues. The requirement for homonuclear 13C/13C decoupling while detecting 13C signals is avoided in the first case because of the low probability of any two 13C nuclei being bonded to each other; in the second case, the labeled 13Cα sites are separated by at least three bonds in the polypeptide chain. The experiments enable the measurement of the 13C chemical shift and 1H–13C and 15N–13C heteronuclear dipolar coupling frequencies associated with the 13Cα and 13C′ backbone sites, which provide orientation constraints complementary to those derived from the 15N labeled amide backbone sites. 13C/13C spin-exchange experiments identify proximate carbon sites. The ability to measure 13C–15N dipolar coupling frequencies and correlate 13C and 15N resonances provides a mechanism for making backbone resonance assignments. Three-dimensional combinations of these experiments ensure that the resolution, assignment, and measurement of orientationally dependent frequencies can be extended to larger proteins. Moreover, measurements of the 13C chemical shift and 1H–13C heteronuclear dipolar coupling frequencies for nearly all side chain sites enable the complete three-dimensional structures of proteins to be determined with this approach. PMID:17293139

  12. Magnetic blackbody shift of hyperfine transitions for atomic clocks

    SciTech Connect

    Berengut, J. C.; Flambaum, V. V.; King-Lacroix, J.

    2009-12-15

    We derive an expression for the magnetic blackbody shift of hyperfine transitions such as the cesium primary reference transition which defines the second. The shift is found to be a complicated function of temperature, and has a T{sup 2} dependence only in the high-temperature limit. We also calculate the shift of ground-state p{sub 1/2} hyperfine transitions which have been proposed as new atomic clock transitions. In this case interaction with the p{sub 3/2} fine-structure multiplet may be the dominant effect.

  13. 7P1/2 hyperfine splitting in 206 , 207 , 209 , 213Fr and the hyperfine anomaly

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Orozco, L. A.; Collister, R.; Gwinner, G.; Tandecki, M.; Behr, J. A.; Pearson, M. R.; Gomez, E.; Aubin, S.

    2013-05-01

    We perform precision measurements on francium, the heaviest alkali with no stable isotopes, at the recently commissioned Francium Trapping Facility at TRIUMF. A combination of RF and optical spectroscopy allows better than 10 ppm (statistical) measurements of the 7P1 / 2 state hyperfine splitting for the isotopes 206 , 207 , 209 , 213Fr, in preparation for weak interaction studies. Together with previous measurements of the ground state hyperfine structure, it is possible to extract the hyperfine anomaly. This is a correction to the point interaction of the nuclear magnetic moment and the electron wavefunction, known as the Bohr Weisskopf effect. Our measurements extend previous measurements to the neutron closed shell isotope (213) as well as further in the neutron deficient isotopes (206, 207). Work supported by NSERC and NRC from Canada, NSF and DOE from USA, CONYACT from Mexico.

  14. Anomalous hyperfine structure of NSF{sub 3} in the degenerate vibrational state v{sub 5}=1: Lifting of the parity degeneracy by the fluorine spin-rotation interaction

    SciTech Connect

    Harder, Hauke; Macholl, Sven; Maeder, Heinrich; Fusina, Luciano; Ozier, Irving

    2010-03-15

    For the principal isotopologue {sup 14}N{sup 32}S{sup 19}F{sub 3} of thiazyl trifluoride in the degenerate fundamental state (v{sub 5}=1), the hyperfine structure has been investigated in the Q-branch spectrum between 8 and 26.5 GHz using microwave Fourier transform waveguide spectrometers with a resolution limit of {approx_equal}30 kHz. In addition to l-type doubling spectra and l-type resonance transitions with ({Delta}k={Delta}l={+-}2), perturbation-allowed spectra were measured with {Delta}(k-l)={+-}3,{+-}6. The range in J was from 13 to 61; for the lower states, kl=-3,-2,-1,0,+1. For all the transitions, the hyperfine patterns observed are predicted to be doublets when only the nitrogen quadrupole Hamiltonian H{sub Q}{sup N} is taken into account. Doublets were indeed measured for transitions with {Gamma}{sub RV}=A{sub 1{r_reversible}}A{sub 2}, where {Gamma}{sub RV} is the rovibrational symmetry. However, when {Gamma}{sub RV}=E{r_reversible}E, triplets and quartets were observed in addition to doublets. These anomalous hyperfine patterns are shown to be due to the ({Delta}k={+-}1) and ({Delta}k={+-}2) matrix elements of the fluorine spin-rotation Hamiltonian H{sub SR}{sup F} characterized by the fluorine spin-rotation constants c(1)=(1/2)(c{sub xz}+c{sub zx}{sup *}) and c(2)=(1/2)(c{sub xx}-c{sub yy}), respectively. These terms in H{sub SR}{sup F} lift the parity degeneracy for {Gamma}{sub RV}=E. The rovibrational Hamiltonian H{sub RV} was adopted from an earlier partner study [S. Macholl et al., J. Phys. Chem. A 113, 668 (2009)]. A good fit to the hyperfine data was obtained with a standard deviation of 3.1 kHz. In the fitting process, 12 rovibrational parameters were varied, while the remaining constants in H{sub RV} were left at the values of Macholl et al. In addition, six hyperfine parameters were determined: four in H{sub Q}{sup N}, and two in H{sub SR}{sup F}. It was found that |c(1)|=7.48(24) kHz and |c(2)|=2.423(22) kHz. This determination of c(1) is

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  16. Whole-core analysis by sup 13 C NMR

    SciTech Connect

    Vinegar, H.J.; Tutunjian, P.N. ); Edelstein, W.A.; Roemer, P.B. )

    1991-06-01

    This paper reports on a whole-core nuclear magnetic resonance (NMR) system that was used to obtain natural abundance {sup 13}C spectra. The system enables rapid, nondestructive measurements of bulk volume of movable oil, aliphatic/aromatic ratio, oil viscosity, and organic vs. carbonate carbon. {sup 13}C NMR can be used in cores where the {sup 1}H NMR spectrum is too broad to resolve oil and water resonances separately. A 5 1/4-in. {sup 13}C/{sup 1}H NMR coil was installed on a General Electric (GE) CSI-2T NMR imager/spectrometer. With a 4-in.-OD whole core, good {sup 13}C signal/noise ratio (SNR) is obtained within minutes, while {sup 1}H spectra are obtained in seconds. NMR measurements have been made of the {sup 13}C and {sup 1}H density of crude oils with a wide range of API gravities. For light- and medium-gravity oils, the {sup 13}C and {sup 1}H signal per unit volume is constant within about 3.5%. For heavy crudes, the {sup 13}C and {sup 1}H density measured by NMR is reduced by the shortening of spin-spin relaxation time. {sup 13}C and {sup 1}H NMR spin-lattice relaxation times were measured on a suite of Cannon viscosity standards, crude oils (4 to 60{degrees} API), and alkanes (C{sub 5} through C{sub 16}) with viscosities at 77{degrees}F ranging from 0.5 cp to 2.5 {times} 10{sup 7} cp. The {sup 13}C and {sup 1}H relaxation times show a similar correlation with viscosity from which oil viscosity can be estimated accurately for viscosities up to 100 cp. The {sup 13}C surface relaxation rate for oils on water-wet rocks is very low. Nonproton decoupled {sup 13}C NMR is shown to be insensitive to kerogen; thus, {sup 13}C NMR measures only the movable hydrocarbon content of the cores. In carbonates, the {sup 13}C spectrum also contains a carbonate powder pattern useful in quantifying inorganic carbon and distinguishing organic from carbonate carbon.

  17. The optical depth of the 158 micron forbidden C-12 II line - Detection of the F = 1 - 0 forbidden C-13 II hyperfine-structure component. [in Orion nebula

    NASA Technical Reports Server (NTRS)

    Stacey, G. J.; Townes, C. H.; Geis, N.; Madden, S. C.; Herrmann, F.; Genzel, R.; Poglitsch, A.; Jackson, J. M.

    1991-01-01

    The detection of the F = 1 - 0 hyperfine component of the 158-micron forbidden C-13 II fine-structure line in the interstellar medium is reported. A 12-point intensity map was obtained of the forbidden C-13 distribution over the inner 190-arcsec (R.A.) X 190-arcsec (decl.) regions of the Orion Nebula using an imaging Fabry-Perot interferometer. The forbidden C-12 II/C-13 II line intensity ratio varies significantly over the region mapped. It is highest (86 +/-0) in the core of the Orion H II region, and significantly lower (62 +/-7) in the outer regions of the map, reflecting higher optical depth in the forbidden C-12 II line here. It is suggested that this enhanced optical depth is the result of limb brightening of the optically thin forbidden C-13 II line at the edges of the bowl-shaped H II region blister.

  18. Experimental investigation of the hyperfine spectra of Pr I-lines: discovery of new fine structure energy levels of Pr I using LIF spectroscopy with medium angular momentum quantum number between 7/2 and 13/2

    NASA Astrophysics Data System (ADS)

    Siddiqui, Imran; Khan, Shamim; Windholz, Laurentius

    2016-03-01

    We present 39 even and 60 odd parity newly discovered fine structure levels of Pr I with angular momentum quantum numbers J = 7 / 2, 9/2, 11/2 and 13/2. Spectral lines in the wavelength range of 4200 Å to 7500 Å were investigated experimentally using laser-induced fluorescence spectroscopy or optogalvanic spectroscopy. Free Pr atoms were produced in a hollow cathode discharge. A high resolution Fourier transform spectrum of Pr was used to extract excitation wavelengths. From an analysis of the recorded hyperfine patterns, together with excitation and fluorescence wavelengths, we were able to find the unknown levels involved in the formation of the investigated lines. More than 500 spectral lines could be classified by the new levels. Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-60485-2

  19. Proton, muon and ¹³C hyperfine coupling constants of C₆₀X and C₇₀X (X = H, Mu).

    PubMed

    Brodovitch, Jean-Claude; Addison-Jones, Brenda; Ghandi, Khashayar; McKenzie, Iain; Percival, Paul W

    2015-01-21

    The reaction of H atoms with fullerene C70 has been investigated by identifying the radical products formed by addition of the atom muonium (Mu) to the fullerene in solution. Four of the five possible radical isomers of C70Mu were detected by avoided level-crossing resonance (μLCR) spectroscopy, using a dilute solution of enriched (13)C70 in decalin. DFT calculations were used to predict muon and (13)C isotropic hyperfine constants as an aid to assigning the observed μLCR signals. Computational methods were benchmarked against previously published experimental data for (13)C60Mu in solution. Analysis of the μLCR spectrum resulted in the first experimental determination of (13)C hyperfine constants in either C70Mu or C70H. The large number of values confirms predictions that the four radical isomers have extended distributions of unpaired electron spin.

  20. Study of Urban environmental quality through Isotopes δ13C

    NASA Astrophysics Data System (ADS)

    González-Sosa, E.; Mastachi-Loza, C.; Becerril-Piña, R.; Ramos-Salinas, N. M.

    2012-04-01

    Usually, trees with similar pH values on their bark develop epiphytes of similar species, the acidity to be a factor for growth. The aim of the study was evaluate the air quality through isotope δ13C in order to define the levels of environmental quality in the city of Queretaro, Mexico. In this work were collected at least 4 epiphytes positioned in trees of the species Prosopis Laevigata at 25 sites of Queretaro City. The samples were analyzed for trace elements with an inductively coupled plasma atomic emission spectroscopy (ICP). The collecting took place during dry period, in May and early rain June 2011 period, and on four sectors to identify the spatial distribution of pollution, using isotopic analysis of concentration of δ 13C. According with the results there are significant differences among the species in each of the sampled areas. The 5 February Avenue presented greater diversity and richness of δ13C, followed by those who were surveyed in the proximity of the UAQ and finally in the middle-east area. An average value of δ13C-17.92%, followed by those surveyed in the vicinity of the UAQ that correspond to sector I and II with an concentration of δ13C-17.55% and δ13C-17.22%, and finally the samples collected in trees scattered in the East-Sector II and IV with a value of δ13C-17.02% and δ13C-15.62%, respectively. Also were observed differences between the dry and wet period. It is likely that these results of δ 13C in moist period reflect the drag of the isotopes due to rain events that could mark a trend in the dilution of this element, however there is a trend in terms of abundance and composition of finding more impact in those species sampled in dry period, in May and early June 2011.

  1. Hyperfine structure interval of the 2s state of hydrogenlike atoms and a constraint on a pseudovector boson with mass below 1 keV/c{sup 2}

    SciTech Connect

    Karshenboim, S. G.

    2011-06-15

    A constraint on a spin-dependent interaction, induced by a pseudovector light boson, is presented. The interaction includes a Yukawa-type contribution {alpha}{sup ''}(s{sub 1}{center_dot}s{sub 2})e{sup -{lambda}r}/r and a contact spin-spin term. To disentangle the long-range and contact terms we utilize experimental data on the 1s and 2s hyperfine intervals for light two-body atoms and construct a specific difference 8xE{sub hfs}(2s)-E{sub hfs}(1s). That allows one to constrain the spin-dependent coupling constant {alpha}{sup ''} of an electron-nucleus Yukawa-type interaction in hydrogen, deuterium, and the helium-3 ion at the level below a part in 10{sup 16}. The derived constraint is related to the range of masses below 4 keV/c{sup 2}. The combined constraint including the contact terms is also presented.

  2. Investigations of the ground-state hyperfine atomic structure and beta decay measurement prospects of {sup 21}Na with improved laser trapping techniques

    SciTech Connect

    Rowe, Mary A.

    1999-05-24

    This thesis describes an experiment in which a neutral atom laser trap loaded with radioactive {sup 21}Na was improved and then used for measurements. The sodium isotope (half-life=22 sec) is produced on line at the 88in cyclotron at Lawrence Berkeley National Laboratory. The author developed an effective magnesium oxide target system which is crucial to deliver a substantive beam of {sup 21}Na to the experiment. Efficient manipulation of the {sup 21}Na beam with lasers allowed 30,000 atoms to be contained in a magneto-optical trap. Using the cold trapped atoms, the author measured to high precision the hyperfine splitting of the atomic ground state of {sup 21}Na. She measured the 3S{sub 1/2}(F=1,m=0)-3S{sub 1/2}(F=2,m=0) atomic level splitting of {sup 21}Na to be 1,906,471,870{+-}200 Hz. Additionally, she achieved initial detection of beta decay from the trap and evaluated the prospects of precision beta decay correlation studies with trapped atoms.

  3. EPR spectrum of the Y@C82 metallofullerene isolated in solid argon matrix: hyperfine structure from EPR spectroscopy and relativistic DFT calculations.

    PubMed

    Misochko, Eugenii Ya; Akimov, Alexander V; Belov, Vasilii A; Tyurin, Daniil A; Bubnov, Vyacheslav P; Kareev, Ivan E; Yagubskii, Eduard B

    2010-08-21

    The EPR spectrum of the Y@C(82) molecules isolated in solid argon matrix was recorded for the first time at a temperature of 5 K. The isotropic hyperfine coupling constant (hfcc) A(iso) = 0.12 +/- 0.02 mT on the nucleus (89)Y as derived from the EPR spectrum is found in more than two times greater than that obtained in previous EPR measurements in liquid solutions. Comparison of the measured hfcc on a metal atom with that predicted by density-functional theory calculations (PBE/L22) indicate that relativistic method provides good agreement between experiment in solid argon and theory. Analysis of the DFT calculated dipole-dipole hf-interaction tensor and electron spin distribution in the endometallofullerenes with encaged group 3 metal atoms Sc, Y and La has been performed. It shows that spin density on the scandium atom represents the Sc d(yz) orbital lying in the symmetry plane of the C(2v) fullerene isomer and interacting with two carbon atoms located in the para-position on the fullerene hexagon. In contrast, the configuration of electron spin density on the heavier atoms, Y and La, is associated with the hybridized orbital formed by interaction of the metal d(yz) and p(y) electronic orbitals.

  4. Detection of inflammatory cell function using 13C magnetic resonance spectroscopy of hyperpolarized [6-13C]-arginine

    PubMed Central

    Najac, Chloé; Chaumeil, Myriam M.; Kohanbash, Gary; Guglielmetti, Caroline; Gordon, Jeremy W.; Okada, Hideho; Ronen, Sabrina M.

    2016-01-01

    Myeloid-derived suppressor cells (MDSCs) are highly prevalent inflammatory cells that play a key role in tumor development and are considered therapeutic targets. MDSCs promote tumor growth by blocking T-cell-mediated anti-tumoral immune response through depletion of arginine that is essential for T-cell proliferation. To deplete arginine, MDSCs express high levels of arginase, which catalyzes the breakdown of arginine into urea and ornithine. Here, we developed a new hyperpolarized 13C probe, [6-13C]-arginine, to image arginase activity. We show that [6-13C]-arginine can be hyperpolarized, and hyperpolarized [13C]-urea production from [6-13C]-arginine is linearly correlated with arginase concentration in vitro. Furthermore we show that we can detect a statistically significant increase in hyperpolarized [13C]-urea production in MDSCs when compared to control bone marrow cells. This increase was associated with an increase in intracellular arginase concentration detected using a spectrophotometric assay. Hyperpolarized [6-13C]-arginine could therefore serve to image tumoral MDSC function and more broadly M2-like macrophages. PMID:27507680

  5. Local structure and hyperfine interactions of 57Fe and 119Sn atoms in brownmillerite-like ferrite Sr 2Fe 1.98Sn 0.02O 5+ x

    NASA Astrophysics Data System (ADS)

    Presniakov, Igor; Sobolev, Alexey; Pokholok, Konstantin; Demazeau, Gérard M.; Baranov, Alexey

    2004-10-01

    Mössbauer spectroscopy has been applied for studying local environment of 57Fe and 119Sn probe atoms within tin-doped Sr2Fe1.98Sn0.02O5+x (x⩽0.02) ferrite with the brownmillerite-type structure. 57Fe Mössbauer spectra indicate no appreciable local distortions induced by the tin dopant atoms. The 119Sn spectra recorded below the magnetic ordering temperature (TN) can be described as a superposition of two Zeeman sextets, which indicate that Sn4+ dopant ions are located in two non-equivalent crystallographic and magnetic sites. The observed hyperfine parameters were discussed supposing Sn4+ cations to replace iron cations in the octahedral (SnO) and tetrahedral (SnT) sublattices. It has been supposed that Sn4+ cations being stabilized in the tetrahedral sublattice complete their nearest anion surrounding up to the octahedral oxygen coordination "SnT4+". Annealing of the Sr2Fe1.98Sn0.02O5+x in helium flux conditions at 950°C leads to formation of divalent Sn2+ cations with a simultaneous decrease of the contribution for the SnT4+ sub-spectrum. The parameters of combined electric and magnetic hyperfine interactions of the 119Sn2+ sub-spectrum underline that impurity atoms are stabilized in the sp3d-hybrid state in the oxygen distorted tetragonal pyramid. The analysis of the 119Sn spectra indicates a chemical reversibility of the processes SnT2+⇌SnT4+ within the tetrahedral sublattice of the brownmillerite-type ferrite.

  6. Anomalous 13C enrichment in modern marine organic carbon

    USGS Publications Warehouse

    Arthur, M.A.; Dean, W.E.; Claypool, G.E.

    1985-01-01

    Marine organic carbon is heavier isotopically (13C enriched) than most land-plant or terrestrial organic C1. Accordingly, ??13C values of organic C in modern marine sediments are routinely interpreted in terms of the relative proportions of marine and terrestrial sources of the preserved organic matter2,3. When independent geochemical techniques are used to evaluate the source of organic matter in Cretaceous or older rocks, those rocks containing mostly marine organic C are found typically to have lighter (more-negative) ??13C values than rocks containing mostly terrestrial organic C. Here we conclude that marine photosynthesis in mid-Cretaceous and earlier oceans generally resulted in a greater fractionation of C isotopes and produced organic C having lighter ??13C values. Modern marine photosynthesis may be occurring under unusual geological conditions (higher oceanic primary production rates, lower PCO2) that limit dissolved CO2 availability and minimize carbon isotope fractionation4. ?? 1985 Nature Publishing Group.

  7. Dihydroflavanonols from Cedrus deodara, A (13)C NMR study.

    PubMed

    Agrawal, P K; Agarwal, S K; Rastogi, R P; Osterdahal, B G

    1981-09-01

    High resolution (13)C NMR study of taxifolin, cedeodarin, cedrin and their methyl ethers allowed unambiguous placement of the Me in 5,7-dihydroxyflavanonol nucleus, besides providing other valuable information on the substitution pattern in the molecule.

  8. Abundance anomaly of the 13C species of CCH

    NASA Astrophysics Data System (ADS)

    Sakai, N.; Saruwatari, O.; Sakai, T.; Takano, S.; Yamamoto, S.

    2010-03-01

    Aims: We have observed the N = 1-0 lines of CCH and its 13C isotopic species toward a cold dark cloud, TMC-1 and a star-forming region, L1527, to investigate the 13C abundances and formation pathways of CCH. Methods: The observations have been carried out with the IRAM 30 m telescope. Results: We have successfully detected the lines of 13CCH and C13CH toward the both sources and found a significant intensity difference between the two 13C isotopic species. The [C13CH] /[13CCH] abundance ratios are 1.6 ± 0.4 (3σ) and 1.6 ± 0.1 (3σ) for TMC-1 and L1527, respectively. The abundance difference between C13CH and 13CCH means that the two carbon atoms of CCH are not equivalent in the formation pathway. On the other hand, the [CCH]/[C13CH] and [CCH]/[13CCH] ratios are evaluated to be larger than 170 and 250 toward TMC-1, and to be larger than 80 and 135 toward L1527, respectively. Therefore, both of the 13C species are significantly diluted in comparison with the interstellar 12C/13C ratio of 60. The dilution is discussed in terms of a behavior of 13C in molecular clouds.

  9. Localized in vivo13C NMR spectroscopy of the brain

    PubMed Central

    Gruetter, Rolf; Adriany, Gregor; Choi, In-Young; Henry, Pierre-Gilles; Lei, Hongxia; Öz, Gülin

    2006-01-01

    Localized 13C NMR spectroscopy provides a new investigative tool for studying cerebral metabolism. The application of 13C NMR spectroscopy to living intact humans and animals presents the investigator with a number of unique challenges. This review provides in the first part a tutorial insight into the ingredients required for achieving a successful implementation of localized 13C NMR spectroscopy. The difficulties in establishing 13C NMR are the need for decoupling of the one-bond 13C–1H heteronuclear J coupling, the large chemical shift range, the low sensitivity and the need for localization of the signals. The methodological consequences of these technical problems are discussed, particularly with respect to (a) RF front-end considerations, (b) localization methods, (c) the low sensitivity, and (d) quantification methods. Lastly, some achievements of in vivo localized 13C NMR spectroscopy of the brain are reviewed, such as: (a) the measurement of brain glutamine synthesis and the feasibility of quantifying glutamatergic action in the brain; (b) the demonstration of significant anaplerotic fluxes in the brain; (c) the demonstration of a highly regulated malate-aspartate shuttle in brain energy metabolism and isotope flux; (d) quantification of neuronal and glial energy metabolism; and (e) brain glycogen metabolism in hypoglycemia in rats and humans. We conclude that the unique and novel insights provided by 13C NMR spectroscopy have opened many new research areas that are likely to improve the understanding of brain carbohydrate metabolism in health and disease. PMID:14679498

  10. Table of hyperfine anomaly in atomic systems

    SciTech Connect

    Persson, J.R.

    2013-01-15

    This table is a compilation of experimental values of magnetic hyperfine anomaly in atomic and ionic systems. The last extensive compilation was published in 1984 by Büttgenbach [S. Büttgenbach, Hyperfine Int. 20 (1984) 1] and the aim here is to make an up to date compilation. The literature search covers the period up to January 2011.

  11. Effects of low-temperature catalytic pretreatments on coal structure and reactivity in liquefaction. Final technical report, Volume 2 - hydrogenative and hydrothermal pretreatments and spectroscopic characterization using pyrolysis-GC-MS, CPMAS {sup 13}C NMR and FT-IR

    SciTech Connect

    Chunshan Song; Hatcher, P.G.; Saini, A.K.; Wenzel, K.A.

    1998-01-01

    It has been indicated by DOE COLIRN panel that low-temperature catalytic pretreatment is a promising approach to the development of an improved liquefaction process. This work is a fundamental study on effects of pretreatments on coal structure and reactivity in liquefaction. The main objectives of this project are to study the coal structural changes induced by low-temperature catalytic and thermal pretreatments by using spectroscopic techniques; and to clarify the pretreatment-induced changes in reactivity or convertibility of coals. As the second volume of the final report, here we summarize our work on spectroscopic characterization of four raw coals including two subbituminous coals and two bituminous coals, tetrahydrofuran (THF)-extracted but unreacted coals, the coals (THF-insoluble parts) that have been thermally pretreated. in the absence of any solvents and in the presence of either a hydrogen-donor solvent or a non-donor solvent, and the coals (THF-insoluble parts) that have been catalytically pretreated in the presence of a dispersed Mo sulfide catalyst in the absence of any solvents and in the presence of either a hydrogen-donor solvent or a non-donor solvent.

  12. Hyperfine interactions in titanates: Study of orbital ordering and local magnetic properties

    SciTech Connect

    Agzamova, P. A. Leskova, Yu. V.; Nikiforov, A. E.

    2013-05-15

    Hyperfine magnetic fields induced on the nuclei of nonmagnetic ions {sup 139}La and {sup 89}Y in LaTiO{sub 3} and YTiO{sub 3}, respectively, have been microscopically calculated. The dependence of the hyperfine fields on the orbital and magnetic structures of the compounds under study has been analyzed. The comparative analysis of the calculated and known experimental data confirms the existence of the static orbital structure in lanthanum and yttrium titanates.

  13. Synthesis of [.sup.13C] and [.sup.2H] substituted methacrylic acid, [.sup.13C] and [.sup.2H] substituted methyl methacrylate and/or related compounds

    DOEpatents

    Alvarez, Marc A.; Martinez, Rodolfo A.; Unkefer, Clifford J.

    2008-01-22

    The present invention is directed to labeled compounds of the formulae ##STR00001## wherein Q is selected from the group consisting of --S--, --S(.dbd.O)--, and --S(.dbd.O).sub.2--, Z is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently selected from the group consisting of hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group selected from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each independently selected from the group consisting of a C.sub.1-C.sub.4 lower alkyl, an aryl, and an alkoxy group, and X is selected from the group consisting of hydrogen, a C.sub.1-C.sub.4 lower alkyl group, and a fully-deuterated C.sub.1-C.sub.4 lower alkyl group. The present invention is also directed to a process of preparing labeled compounds, e.g., process of preparing [.sup.13C]methacrylic acid by reacting a (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13CH.sub.2)-- aryl sulfone precursor with .sup.13CHI to form a (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13C(.sup.13CH.sub.3).sub.2)-- aryl sulfone intermediate, and, reacting the (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13C(.sup.13CH.sub.3).sub.2)-- aryl sulfone intermediate with sodium hydroxide, followed by acid to form [.sup.13C]methacrylic acid. The present invention is further directed to a process of preparing [.sup.2H.sub.8]methyl methacrylate by reacting a (HOOC--C(C.sup.2H.sub.3).sub.2-- aryl sulfinyl intermediate with CD.sub.3I to form a (.sup.2H.sub.3COOC--C(C.sup.2H.sub.3).sub.2)-- aryl sulfinyl intermediate, and heating the(.sup.2H.sub.3COOC--C(C.sup.2H.sub.3).sub.2)-- aryl sulfinyl intermediate at temperatures and for time sufficient to form [.sup.2H.sub.8]methyl methacrylate.

  14. Identification of natural metabolites in mixture: a pattern recognition strategy based on (13)C NMR.

    PubMed

    Hubert, Jane; Nuzillard, Jean-Marc; Purson, Sylvain; Hamzaoui, Mahmoud; Borie, Nicolas; Reynaud, Romain; Renault, Jean-Hugues

    2014-03-18

    Because of their highly complex metabolite profile, the chemical characterization of bioactive natural extracts usually requires time-consuming multistep purification procedures to achieve the structural elucidation of pure individual metabolites. The aim of the present work was to develop a dereplication strategy for the identification of natural metabolites directly within mixtures. Exploiting the polarity range of metabolites, the principle was to rapidly fractionate a multigram quantity of a crude extract by centrifugal partition extraction (CPE). The obtained fractions of simplified chemical composition were subsequently analyzed by (13)C NMR. After automatic collection and alignment of (13)C signals across spectra, hierarchical clustering analysis (HCA) was performed for pattern recognition. As a result, strong correlations between (13)C signals of a single structure within the mixtures of the fraction series were visualized as chemical shift clusters. Each cluster was finally assigned to a molecular structure with the help of a locally built (13)C NMR chemical shift database. The proof of principle of this strategy was achieved on a simple model mixture of commercially available plant secondary metabolites and then applied to a bark extract of the African tree Anogeissus leiocarpus Guill. & Perr. (Combretaceae). Starting from 5 g of this genuine extract, the fraction series was generated by CPE in only 95 min. (13)C NMR analyses of all fractions followed by pattern recognition of (13)C chemical shifts resulted in the unambiguous identification of seven major compounds, namely, sericoside, trachelosperogenin E, ellagic acid, an epimer mixture of (+)-gallocatechin and (-)-epigallocatechin, 3,3'-di-O-methylellagic acid 4'-O-xylopyranoside, and 3,4,3'-tri-O-methylflavellagic acid 4'-O-glucopyranoside. PMID:24555703

  15. High-Resolution Correlation Spectroscopy of 13C Spins Near a Nitrogen-Vacancy Center in Diamond

    NASA Astrophysics Data System (ADS)

    Meriles, Carlos; Laraoui, Abdelghani; Dolde, Florian; Wracthrup, Joerg; Reinhard, Friedemann; Burk, Christian

    2013-03-01

    We use a pulse protocol to monitor the time evolution of the 13C ensemble in the vicinity of a NV center. We observe time correlations in the nuclear spin dynamics that extend over several milliseconds exceeding the color center coherence lifetime by more than an order of magnitude. Upon Fourier transform, we separate 13C spins exhibiting differing coupling constants with a frequency resolution inversely proportional to the NV spin-lattice relaxation time. Further, we use the nuclear spin of the host nitrogen as a quantum register during the correlation interval and demonstrate that hyperfine-shifted resonances in this spectrum can be separated from the bare carbon peak upon proper initialization of the NV. Intriguingly, we find that the amplitude of the correlation signal exhibits a sharp dependence on the applied magnetic field, virtually disappearing below a critical field common to all centers. The value of this transition field can be `tuned' by properly adjusting the timing within our correlation scheme. We discuss these observations in the context of the `quantum-to-classical' transition proposed recently to explain the combined dynamics of the NV spin and the 13C bath at variable magnetic field. A.L. and C.A.M. acknowledge support from Research Corp., the von Humboldt Foundation, and NSF. F.D., C.B., F.R. and J.W. acknowledge support from the EU, the DFG, and the Volkswagen Foundation.

  16. 1H and 13C NMR assignments for the cyanine dyes SYBR Safe and thiazole orange.

    PubMed

    Evenson, William E; Boden, Lauren M; Muzikar, Katy A; O'Leary, Daniel J

    2012-12-01

    Analysis of (1)H and (13)C NMR and mass spectral data for the fluorescent nucleic acid stain SYBR Safe indicates that it contains a cyanine-based cationic core structure identical to thiazole orange. The difference between these two compounds is the type of N-substitution on the quinolinium ring system (SYBR Safe, n-Pr; thiazole orange, Me). The (1)H and (13)C NMR resonances for both compounds were assigned on the basis of one- and two-dimensional (COSY, ROESY, HSQC, and HMBC) experiments. The preferred conformation of these compounds was computed by ab initio methods and found to be consistent with the NMR data.

  17. Food webs in Mongolian grasslands: the analysis of 13C and 15N natural abundances.

    PubMed

    Kohzu, Ayato; Iwata, T; Kato, M; Nishikawa, J; Wada, Eitaro; Amartuvshin, N; Namkhaidorj, B; Fujita, N

    2009-09-01

    Overgrazing often lowers species richness and productivity of grassland communities. For Mongolian grassland ecosystems, a lack of detailed information about food-web structures makes it difficult to predict the effects of overgrazing on species diversity and community composition. We analysed the delta13C and delta15N signatures of herbaceous plants, arthropods (grouped by feeding habit), wild and domestic mammals, and humans in central Mongolia to understand the predominant food-web pathways in this grassland ecosystem. The delta13C and delta15N values of mammals showed little variation within species, but varied considerably with slope position for arthropods. The apparent isotopic discrimination between body tissue and hair of mammals was estimated as 2.0 per thousand for delta13C and 2.1 per thousand for delta15N, which was large enough to cause overestimation of the trophic level of mammals if not taken into account when using hair samples to measure isotopic enrichment.

  18. Animal /sup 13/C//sup 12/C correlates with trophic level in pelagic food webs

    SciTech Connect

    Rau, G.H.; Mearns, A.J.; Young, D.R.; Olson, R.J.; Schafer, H.A.; Kaplan, I.R.

    1983-01-01

    Whatever the underlying cause(s), our observations further substantiate the existence of small but progressive increases in animal tissue /sup 13/C//sup 12/C with increasing trophic level. Such a relationship has significant implications for the use of stable carbon isotope natural abundance in animal tissues or remains, in order to interpret the tropic structure and food base of past as well as present-day animal communities. The delta/sup 13/C of the marine animal tissues analyzed ranged from -20.6 to -15.8%. The macro-fauna from the eastern tropical Pacific Ocean had higher isotope values than the net plankton collected from the same area. The average increases in delta/sup 13/C per trophic level were 0.73 and 1.38% for the California coastal waters and for the eastern tropical Pacific, respectively. These isotopic increases approximate closely those previously reported to occur within single trophic level steps.

  19. Multispectral plasmon-induced transparency in hyperfine terahertz meta-molecules.

    PubMed

    Yang, Shengyan; Xia, Xiaoxiang; Liu, Zhe; Yiwen, E; Wang, Yujin; Tang, Chengchun; Li, Wuxia; Li, Junjie; Wang, Li; Gu, Changzhi

    2016-11-01

    We experimentally and theoretically demonstrated an approach to achieve multispectral plasmon-induced transparency (PIT) by utilizing meta-molecules that consist of hyperfine terahertz meta-atoms. The feature size of such hyperfine meta-atoms is 400 nm, which is one order smaller than that of normal terahertz metamaterials. The hyperfine meta-atoms with close eigenfrequencies and narrow resonant responses introduce different metastable energy levels, which makes the multispectral PIT possible. In the triple PIT system, the slow light effect is further confirmed as the effective group delay at three transmission windows can reach 7.3 ps, 7.4 ps and 4.5 ps, respectively. Precisely controllable manipulation of the PIT peaks in such hyperfine meta-molecules was also proven. The new hyperfine planar design is not only suitable for high-integration applications, but also exhibits significant slow light effect, which has great potential in advanced multichannel optical information processing. Moreover, it reveals the possibility to construct hyperfine N-level energy systems by artificial hyperfine plasmonic structures, which brings a significant prospect for applications on miniaturized plasmonic devices.

  20. Multispectral plasmon-induced transparency in hyperfine terahertz meta-molecules

    NASA Astrophysics Data System (ADS)

    Yang, Shengyan; Xia, Xiaoxiang; Liu, Zhe; Yiwen, E.; Wang, Yujin; Tang, Chengchun; Li, Wuxia; Li, Junjie; Wang, Li; Gu, Changzhi

    2016-11-01

    We experimentally and theoretically demonstrated an approach to achieve multispectral plasmon-induced transparency (PIT) by utilizing meta-molecules that consist of hyperfine terahertz meta-atoms. The feature size of such hyperfine meta-atoms is 400 nm, which is one order smaller than that of normal terahertz metamaterials. The hyperfine meta-atoms with close eigenfrequencies and narrow resonant responses introduce different metastable energy levels, which makes the multispectral PIT possible. In the triple PIT system, the slow light effect is further confirmed as the effective group delay at three transmission windows can reach 7.3 ps, 7.4 ps and 4.5 ps, respectively. Precisely controllable manipulation of the PIT peaks in such hyperfine meta-molecules was also proven. The new hyperfine planar design is not only suitable for high-integration applications, but also exhibits significant slow light effect, which has great potential in advanced multichannel optical information processing. Moreover, it reveals the possibility to construct hyperfine N-level energy systems by artificial hyperfine plasmonic structures, which brings a significant prospect for applications on miniaturized plasmonic devices.

  1. Multispectral plasmon-induced transparency in hyperfine terahertz meta-molecules.

    PubMed

    Yang, Shengyan; Xia, Xiaoxiang; Liu, Zhe; Yiwen, E; Wang, Yujin; Tang, Chengchun; Li, Wuxia; Li, Junjie; Wang, Li; Gu, Changzhi

    2016-11-01

    We experimentally and theoretically demonstrated an approach to achieve multispectral plasmon-induced transparency (PIT) by utilizing meta-molecules that consist of hyperfine terahertz meta-atoms. The feature size of such hyperfine meta-atoms is 400 nm, which is one order smaller than that of normal terahertz metamaterials. The hyperfine meta-atoms with close eigenfrequencies and narrow resonant responses introduce different metastable energy levels, which makes the multispectral PIT possible. In the triple PIT system, the slow light effect is further confirmed as the effective group delay at three transmission windows can reach 7.3 ps, 7.4 ps and 4.5 ps, respectively. Precisely controllable manipulation of the PIT peaks in such hyperfine meta-molecules was also proven. The new hyperfine planar design is not only suitable for high-integration applications, but also exhibits significant slow light effect, which has great potential in advanced multichannel optical information processing. Moreover, it reveals the possibility to construct hyperfine N-level energy systems by artificial hyperfine plasmonic structures, which brings a significant prospect for applications on miniaturized plasmonic devices. PMID:27604845

  2. Transport and imaging of brute-force (13)C hyperpolarization.

    PubMed

    Hirsch, Matthew L; Smith, Bryce A; Mattingly, Mark; Goloshevsky, Artem G; Rosay, Melanie; Kempf, James G

    2015-12-01

    We demonstrate transport of hyperpolarized frozen 1-(13)C pyruvic acid from its site of production to a nearby facility, where a time series of (13)C images was acquired from the aqueous dissolution product. Transportability is tied to the hyperpolarization (HP) method we employ, which omits radical electron species used in other approaches that would otherwise relax away the HP before reaching the imaging center. In particular, we attained (13)C HP by 'brute-force', i.e., using only low temperature and high-field (e.g., T<∼2K and B∼14T) to pre-polarize protons to a large Boltzmann value (∼0.4% (1)H polarization). After polarizing the neat, frozen sample, ejection quickly (<1s) passed it through a low field (B<100G) to establish the (1)H pre-polarization spin temperature on (13)C via the process known as low-field thermal mixing (yielding ∼0.1% (13)C polarization). By avoiding polarization agents (a.k.a. relaxation agents) that are needed to hyperpolarize by the competing method of dissolution dynamic nuclear polarization (d-DNP), the (13)C relaxation time was sufficient to transport the sample for ∼10min before finally dissolving in warm water and obtaining a (13)C image of the hyperpolarized, dilute, aqueous product (∼0.01% (13)C polarization, a >100-fold gain over thermal signals in the 1T scanner). An annealing step, prior to polarizing the sample, was also key for increasing T1∼30-fold during transport. In that time, HP was maintained using only modest cryogenics and field (T∼60K and B=1.3T), for T1((13)C) near 5min. Much greater time and distance (with much smaller losses) may be covered using more-complete annealing and only slight improvements on transport conditions (e.g., yielding T1∼5h at 30K, 2T), whereas even intercity transfer is possible (T1>20h) at reasonable conditions of 6K and 2T. Finally, it is possible to increase the overall enhancement near d-DNP levels (i.e., 10(2)-fold more) by polarizing below 100mK, where nanoparticle

  3. Transport and imaging of brute-force 13C hyperpolarization

    NASA Astrophysics Data System (ADS)

    Hirsch, Matthew L.; Smith, Bryce A.; Mattingly, Mark; Goloshevsky, Artem G.; Rosay, Melanie; Kempf, James G.

    2015-12-01

    We demonstrate transport of hyperpolarized frozen 1-13C pyruvic acid from its site of production to a nearby facility, where a time series of 13C images was acquired from the aqueous dissolution product. Transportability is tied to the hyperpolarization (HP) method we employ, which omits radical electron species used in other approaches that would otherwise relax away the HP before reaching the imaging center. In particular, we attained 13C HP by 'brute-force', i.e., using only low temperature and high-field (e.g., T < ∼2 K and B ∼ 14 T) to pre-polarize protons to a large Boltzmann value (∼0.4% 1H polarization). After polarizing the neat, frozen sample, ejection quickly (<1 s) passed it through a low field (B < 100 G) to establish the 1H pre-polarization spin temperature on 13C via the process known as low-field thermal mixing (yielding ∼0.1% 13C polarization). By avoiding polarization agents (a.k.a. relaxation agents) that are needed to hyperpolarize by the competing method of dissolution dynamic nuclear polarization (d-DNP), the 13C relaxation time was sufficient to transport the sample for ∼10 min before finally dissolving in warm water and obtaining a 13C image of the hyperpolarized, dilute, aqueous product (∼0.01% 13C polarization, a >100-fold gain over thermal signals in the 1 T scanner). An annealing step, prior to polarizing the sample, was also key for increasing T1 ∼ 30-fold during transport. In that time, HP was maintained using only modest cryogenics and field (T ∼ 60 K and B = 1.3 T), for T1(13C) near 5 min. Much greater time and distance (with much smaller losses) may be covered using more-complete annealing and only slight improvements on transport conditions (e.g., yielding T1 ∼ 5 h at 30 K, 2 T), whereas even intercity transfer is possible (T1 > 20 h) at reasonable conditions of 6 K and 2 T. Finally, it is possible to increase the overall enhancement near d-DNP levels (i.e., 102-fold more) by polarizing below 100 mK, where

  4. 13C-based metabolic flux analysis: fundamentals and practice.

    PubMed

    Yang, Tae Hoon

    2013-01-01

    Isotope-based metabolic flux analysis is one of the emerging technologies applied to system level metabolic phenotype characterization in metabolic engineering. Among the developed approaches, (13)C-based metabolic flux analysis has been established as a standard tool and has been widely applied to quantitative pathway characterization of diverse biological systems. To implement (13)C-based metabolic flux analysis in practice, comprehending the underlying mathematical and computational modeling fundamentals is of importance along with carefully conducted experiments and analytical measurements. Such knowledge is also crucial when designing (13)C-labeling experiments and properly acquiring key data sets essential for in vivo flux analysis implementation. In this regard, the modeling fundamentals of (13)C-labeling systems and analytical data processing are the main topics we will deal with in this chapter. Along with this, the relevant numerical optimization techniques are addressed to help implementation of the entire computational procedures aiming at (13)C-based metabolic flux analysis in vivo.

  5. A scientific workflow framework for (13)C metabolic flux analysis.

    PubMed

    Dalman, Tolga; Wiechert, Wolfgang; Nöh, Katharina

    2016-08-20

    Metabolic flux analysis (MFA) with (13)C labeling data is a high-precision technique to quantify intracellular reaction rates (fluxes). One of the major challenges of (13)C MFA is the interactivity of the computational workflow according to which the fluxes are determined from the input data (metabolic network model, labeling data, and physiological rates). Here, the workflow assembly is inevitably determined by the scientist who has to consider interacting biological, experimental, and computational aspects. Decision-making is context dependent and requires expertise, rendering an automated evaluation process hardly possible. Here, we present a scientific workflow framework (SWF) for creating, executing, and controlling on demand (13)C MFA workflows. (13)C MFA-specific tools and libraries, such as the high-performance simulation toolbox 13CFLUX2, are wrapped as web services and thereby integrated into a service-oriented architecture. Besides workflow steering, the SWF features transparent provenance collection and enables full flexibility for ad hoc scripting solutions. To handle compute-intensive tasks, cloud computing is supported. We demonstrate how the challenges posed by (13)C MFA workflows can be solved with our approach on the basis of two proof-of-concept use cases.

  6. Synthesis and applications of {sup 13}C glycerol

    SciTech Connect

    Stocking, E.; Khalsa, O.; Martinez, R.A.; Silks, L.A. III

    1994-12-01

    Due in part to the use of labeled glycerol for the {sup 13}C enrichment of biomolecules, we are currently developing new synthetic routes to various isotopomers of glycerol. Judging from our experience, traditional methods of glycerol synthesis are not easily adapted for isotopic enrichment and/or have poor overall yields (12 to 15%). Furthermore, the use of glycerol for enrichment can be prohibitively expensive and its availability is limited by the level of demand. We are presently developing a short de novo synthesis of glycerol from carbon dioxide ({approximately}53% overall yield for four steps) and are examining the feasibility of synthesizing site-specific {sup 13}C-labeled glycerol and dihydroxyacetone (DHA) from labeled methanol and carbon dioxide. One application of {sup 13}C glycerol we have examined is enzymatic conversion of glycerol to glyceraldehyde-3-monophosphate or dihydroxyacetone monophosphate (DHAP) with yields ranging from 25 to 50% (as determined by NMR spectroscopy). We are also pursuing the chemical conversion of {sup 13}C-labeled DHA to DHAP. We are especially interested in {sup 13}C-labeled DHAP because we are investigating its use as a chemo-enzymatic precursor for both labeled 2-deoxyribose and 2-deoxyribonucleic acids.

  7. A scientific workflow framework for (13)C metabolic flux analysis.

    PubMed

    Dalman, Tolga; Wiechert, Wolfgang; Nöh, Katharina

    2016-08-20

    Metabolic flux analysis (MFA) with (13)C labeling data is a high-precision technique to quantify intracellular reaction rates (fluxes). One of the major challenges of (13)C MFA is the interactivity of the computational workflow according to which the fluxes are determined from the input data (metabolic network model, labeling data, and physiological rates). Here, the workflow assembly is inevitably determined by the scientist who has to consider interacting biological, experimental, and computational aspects. Decision-making is context dependent and requires expertise, rendering an automated evaluation process hardly possible. Here, we present a scientific workflow framework (SWF) for creating, executing, and controlling on demand (13)C MFA workflows. (13)C MFA-specific tools and libraries, such as the high-performance simulation toolbox 13CFLUX2, are wrapped as web services and thereby integrated into a service-oriented architecture. Besides workflow steering, the SWF features transparent provenance collection and enables full flexibility for ad hoc scripting solutions. To handle compute-intensive tasks, cloud computing is supported. We demonstrate how the challenges posed by (13)C MFA workflows can be solved with our approach on the basis of two proof-of-concept use cases. PMID:26721184

  8. Dynamic nuclear polarization-enhanced 1H-13C double resonance NMR in static samples below 20 K

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H-13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H-13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H-13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr-Purcell experiments and numerical simulations of Carr-Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C-13C exchange spectrum of selectively 13C-labeled β-amyloid fibrils.

  9. 13C-n.m.r. analysis of some sulphate derivatives of chitosan.

    PubMed

    Hirano, S; Hasegawa, M; Kinugawa, J

    1991-10-01

    Positions of substitution with sulphate in three water-soluble sulphated derivatives of chitosan were analysed by 13C n.m.r. The structures of N-acetylchitosan 3,6-O-disulphate, sodium chitosan N-, 6-O-disulphate, and sodium chitosan 6-O-monosulphate were confirmed.

  10. Geochemical Approach to Archaeal Ecology: δ13C of GDGTs

    NASA Astrophysics Data System (ADS)

    Lichtin, S.; Warren, C.; Pearson, A.; Pagani, M.

    2015-12-01

    Over the last decade and a half, glycerol dialkyl glycerol tetraethers (GDGTs) have increasingly been used to reconstruct environmental temperatures; proxies like TEX86 that correlate the relative abundance of these archaeal cell membrane lipids to sea surface temperature are omnipresent in paleoclimatology literature. While it has become common to make claims about past temperatures using GDGTs, our present understanding of the organisms that synthesize the compounds is still quite limited. The generally accepted theory states that microorganisms like the Thaumarchaeota modify the structure of membrane lipids to increase intermolecular interactions, strengthening the membrane at higher temperatures. Yet to date, culture experiments have been largely restricted to a single species, Nitrosopumilus maritimes, and recent studies on oceanic archaeal rRNA have revealed that these biomarkers are produced in diverse, heterogeneous, and site-specific communities. This brings up questions as to whether different subclasses of GDGTs, and all subsequent proxies, represent adaptation within a single organismal group or a shift in community composition. To investigate whether GDGTs with different chain structures, from the simple isoprenoidal GDGT-0 to Crenarchaeol with its many cyclopentane groups, are sourced from archaea with similar or disparate metabolic pathways—and if that information is inherited in GDGTs trapped in marine sediments—this study examines the stable carbon isotope values (δ13C) of GDGTs extracted from the uppermost meters of sediment in the Orca Basin, Gulf of Mexico, using spooling-wire microcombustion isotope-ratio mass spectrometer (SWiM-IRMS), tackling a fundamental assumption of the TEX86 proxy that influences the way we perceive the veracity of existing temperature records.

  11. 1H and 13C resonance designation of antimycin A1 by two-dimensional NMR spectroscopy

    USGS Publications Warehouse

    Abidi, S.L.; Adams, B.R.

    1987-01-01

    Complete 1H and 13C resonance assignments of antimycin A1 were accomplished by two-dimensional NMR techniques, viz. 1H homonuclear COSY correlation, heteronuclear 13C-1H chemical shift correlation and long-range heteronuclear 13C-1H COLOC correlation. Antimycin A1 was found to consist of two isomeric components in a 2:1 ratio based on NMR spectroscopic evidence. The structure of the major component was newly assigned as the 8-isopentanoic acid ester. The spectra of the minor component were consistent with the known structure of antimycin A1.

  12. Hyperfine structures and Landé g{sub J}-factors for n=2 states in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations

    SciTech Connect

    Verdebout, S.; Nazé, C.; Rynkun, P.; Godefroid, M.

    2014-09-15

    Energy levels, hyperfine interaction constants, and Landé g{sub J}-factors are reported for n=2 states in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations. Valence, core–valence, and core–core correlation effects are taken into account through single and double-excitations from multireference expansions to increasing sets of active orbitals. A systematic comparison of the calculated hyperfine interaction constants is made with values from the available literature.

  13. {sup 13}C relaxation in an RNA hairpin

    SciTech Connect

    King, G.C. |; Akratos, C.; Xi, Z.; Michnica, M.J.

    1994-12-01

    This initial survey of {sup 13}C relaxation in the {triangle}TAR RNA element has generated a number of interesting results that should prove generally useful for future studies. The most readily comparable study in the literature monitored {sup 13}C relaxation of the methyl groups from unusual bases in tRNA{sup Phe}. The study, which used T{sub 1} and NOE data only, reported order parameters for the methyl group axis that ranged between 0.51 and 0.97-a range similar to that observed here. However, they reported a breakdown of the standard order parameter analysis at higher (118-MHz {sup 13}C) frequencies, which should serve to emphasize the need for a thorough exploration of suitable motional models.

  14. Antiferromagnetic nuclear spin helix and topological superconductivity in 13C nanotubes

    NASA Astrophysics Data System (ADS)

    Hsu, Chen-Hsuan; Stano, Peter; Klinovaja, Jelena; Loss, Daniel

    2015-12-01

    We investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction arising from the hyperfine coupling between localized nuclear spins and conduction electrons in interacting 13C carbon nanotubes. Using the Luttinger liquid formalism, we show that the RKKY interaction is sublattice dependent, consistent with the spin susceptibility calculation in noninteracting carbon nanotubes, and it leads to an antiferromagnetic nuclear spin helix in finite-size systems. The transition temperature reaches up to tens of mK, due to a strong boost by a positive feedback through the Overhauser field from ordered nuclear spins. Similar to GaAs nanowires, the formation of the helical nuclear spin order gaps out half of the conduction electrons, and is therefore observable as a reduction of conductance by a factor of 2 in a transport experiment. The nuclear spin helix leads to a density wave combining spin and charge degrees of freedom in the electron subsystem, resulting in synthetic spin-orbit interaction, which induces nontrivial topological phases. As a result, topological superconductivity with Majorana fermion bound states can be realized in the system in the presence of proximity-induced superconductivity without the need of fine tuning the chemical potential. We present the phase diagram as a function of system parameters, including the pairing gaps, the gap due to the nuclear spin helix, and the Zeeman field perpendicular to the helical plane.

  15. Laser vaporization generation of Al sup 12 C, Al sup 13 C, Al sup 12 C sub 2 , and Al sup 13 C sub 2 for rare gas matrix electron spin resonance studies: Experimental--theoretical comparisons

    SciTech Connect

    Knight, L.B. Jr.; Cobranchi, S.T.; Herlong, J.O.; Arrington, C.A. )

    1990-05-15

    The metal carbide radicals AlC and AlC{sub 2} have been generated by the laser vaporization of aluminum carbide and trapped in neon and argon matrices at 4 K for electron spin resonance (ESR) characterization. These results provide the first experimental evidence showing that AlC has a {sup 4}{Sigma} ground electronic state and that AlC{sub 2} is {ital X} {sup 2}{ital A}{sub 1}. {ital Ab} {ital initio} theoretical calculations were conducted for the geometries and various nuclear hyperfine parameters in both radicals which yielded {ital A} values in reasonable agreement with the observed. In AlC, the three unpaired electrons reside primarily on carbon with the following neon matrix magnetic parameters (MHz): {ital g}{sub {parallel}}=2.000(1); {ital g}{sub {perpendicular}}=2.0010(5); {vert bar}{ital A}{sub {perpendicular}}(Al){vert bar}=33.2(5); {vert bar}{ital A}{sub {parallel}}(Al){vert bar}=3(3); {ital A}{sub {perpendicular}}({sup 13}C)=52.1(5); {ital A}{sub {parallel}}({sup 13}C)=52(2); and {ital D}(zero field splitting)=374(1). For AlC{sub 2}, the spin density resides predominantly in an aluminum 3{ital p}{sub {ital z}}/3{ital s} hybrid directed away from C{sub 2}. The neon magnetic parameters (MHz) are: {ital g}{sub {parallel}}=2.0005(5); {ital g}{sub {perpendicular}}=1.9965(3); {ital A}{sub {perpendicular}}(Al)=941.5(5); {ital A}{sub {parallel}}(Al)=1067(1); {vert bar}{ital A}{sub {parallel}}({sup 13}C){vert bar}=59(1); and {vert bar}{ital A}{sub {perpendicular}}({sup 13}C){vert bar}=52(1).

  16. Kinetic modeling of hyperpolarized 13C 1-pyruvate metabolism in normal rats and TRAMP mice

    NASA Astrophysics Data System (ADS)

    Zierhut, Matthew L.; Yen, Yi-Fen; Chen, Albert P.; Bok, Robert; Albers, Mark J.; Zhang, Vickie; Tropp, Jim; Park, Ilwoo; Vigneron, Daniel B.; Kurhanewicz, John; Hurd, Ralph E.; Nelson, Sarah J.

    2010-01-01

    PurposeTo investigate metabolic exchange between 13C 1-pyruvate, 13C 1-lactate, and 13C 1-alanine in pre-clinical model systems using kinetic modeling of dynamic hyperpolarized 13C spectroscopic data and to examine the relationship between fitted parameters and dose-response. Materials and methodsDynamic 13C spectroscopy data were acquired in normal rats, wild type mice, and mice with transgenic prostate tumors (TRAMP) either within a single slice or using a one-dimensional echo-planar spectroscopic imaging (1D-EPSI) encoding technique. Rate constants were estimated by fitting a set of exponential equations to the dynamic data. Variations in fitted parameters were used to determine model robustness in 15 mm slices centered on normal rat kidneys. Parameter values were used to investigate differences in metabolism between and within TRAMP and wild type mice. ResultsThe kinetic model was shown here to be robust when fitting data from a rat given similar doses. In normal rats, Michaelis-Menten kinetics were able to describe the dose-response of the fitted exchange rate constants with a 13.65% and 16.75% scaled fitting error (SFE) for kpyr→lac and kpyr→ala, respectively. In TRAMP mice, kpyr→lac increased an average of 94% after up to 23 days of disease progression, whether the mice were untreated or treated with casodex. Parameters estimated from dynamic 13C 1D-EPSI data were able to differentiate anatomical structures within both wild type and TRAMP mice. ConclusionsThe metabolic parameters estimated using this approach may be useful for in vivo monitoring of tumor progression and treatment efficacy, as well as to distinguish between various tissues based on metabolic activity.

  17. Measuring doubly 13C-substituted ethane by mass spectrometry

    NASA Astrophysics Data System (ADS)

    Clog, M.; Ling, C.; Eiler, J. M.

    2012-12-01

    Ethane (C2H6) is present in non-negligible amounts in most natural gas reservoirs and is used to produce ethylene for petrochemical industries. It is one of the by-products of lipid metabolism and is the arguably simplest molecule that can manifest multiple 13C substitutions. There are several plausible controls on the relative abundances of 13C2H6 in natural gases: thermodynamically controlled homogeneous isotope exchange reactions analogous to those behind carbonate clumped isotope thermometry; inheritance from larger biomolecules that under thermal degradation to produce natural gas; mixing of natural gases that differ markedly in bulk isotopic composition; or combinations of these and/or other, less expected fractionations. There is little basis for predicting which of these will dominate in natural samples. Here, we focus on an analytical techniques that will provide the avenue for exploring these phenomena. The method is based on high-resolution gas source isotope ratio mass spectrometry, using the Thermo 253-Ultra (a new prototype mass spectrometer). This instrument achieves the mass resolution (M/Δ M) up to 27,000, permitting separation of the isobaric interferences of potential contaminants and isotopologues of an analtye or its fragments which share a cardinal mass. We present techniques to analyze several isotopologues of molecular and fragment ions of C2H6. The critical isobaric separations for our purposes include: discrimination of 13C2H6 from 13C12CDH5 at mass 32 and separation of the 13CH3 fragment from 12CH4 at mass 16, both requiring at least a mass resolution of 20000 to make an adequate measurement. Other obvious interferences are either cleanly separated (e.g., O2, O) or accounted for by peak-stripping (CH3OH on mass 32 and NH2 on mass 16). We focus on a set of measurements which constrain: the doubly-substituted isotopologue, 13C2H6, and the 13CH3/12CH3 ratio of the methyl fragment, which constrains the bulk δ 13C. Similar methods can be

  18. Extraordinary 13C enrichment of diether lipids at the Lost City Hydrothermal Field indicates a carbon-limited ecosystem

    NASA Astrophysics Data System (ADS)

    Bradley, Alexander S.; Hayes, John M.; Summons, Roger E.

    2009-01-01

    Active and inactive carbonate chimneys from the Lost City Hydrothermal Field contain up to 0.6% organic carbon with diverse lipid assemblages. The δ 13C values of total organic carbon range from -21.5‰ vs. VPDB at an extinct carbonate chimney to -2.8‰ at a 70 °C, actively venting carbonate chimney. Samples collected at locations with total organic carbon with δ 13C > -15‰ also contained high abundances of isoprenoidal and nonisoprenoidal diether lipids. Samples with TOC more depleted in 13C lacked or contained lower amounts of these diethers. Isoprenoidal diethers, including sn-2 hydroxyarchaeol, sn-3 hydroxyarchaeol, and putative dihydroxyarchaeol, are likely to derive from methanogenic archaea. These compounds have δ 13C values ranging from -2.9 to +6.7‰ vs. VPDB. Nonisoprenoidal diethers and monoethers are presumably derived from bacteria, and have structures similar to those produced by sulfate-reducing bacteria in culture and at cold seeps. In samples that also contained abundant hydroxyarchaeols, these diethers have δ 13C values between -11.8 and +3.6‰. In samples without abundant hydroxyarchaeols, the nonisoprenoidal diethers were typically more depleted in 13C, with δ 13C as low as -28.7‰ in chimneys and -45‰ in fissures. The diethers at Lost City are probably derived from hydrogen-consuming methanogens and bacteria. High hydrogen concentrations favor methanogenesis over methanotrophy and allow the concurrent growth of methanogens and sulfate-reducing bacteria. The unusual enrichment of 13C in lipids can be attributed to nearly complete consumption of bioavailable carbon in vent fluids. Under carbon-limited conditions, the isotope effects that usually lead to 13C-depletion in organic material cannot be expressed. Consequently, metabolic products such as lipids and methane have δ 13C values typical of abiotic carbon.

  19. Optimized [1-13C]glucose infusion protocol for 13C magnetic resonance spectroscopy at 3 Tesla of human brain glucose metabolism under euglycemic and hypoglycemic conditions

    PubMed Central

    van de Ven, Kim C.C.; van der Graaf, Marinette; Tack, Cees J.J.; Klomp, Dennis W.J.; Heerschap, Arend; de Galan, Bastiaan E.

    2009-01-01

    The effect of insulin-induced hypoglycemia on cerebral glucose metabolism is largely unknown. 13C MRS is a unique tool to study cerebral glucose metabolism, but the concurrent requirement for [1-13C]glucose administration limits its use under hypoglycemic conditions. To facilitate 13C MRS data analysis we designed separate [1-13C]glucose infusion protocols for hyperinsulinemic euglycemic and hypoglycemic clamps in such a way that plasma isotopic enrichment of glucose was stable and comparable under both glycemic conditions. 13C MR spectra were acquired with optimized 13C MRS measurement techniques to obtain high quality 13C MR spectra with these protocols. PMID:19913052

  20. Neutron Backgrounds: 13C({alpha}, n) etc

    SciTech Connect

    Mitsui, Tadao

    2005-09-08

    13C({alpha}, n) reaction is the main neutron source in an underground large-volume liquid-scintillator detector KamLAND. {alpha} sources, targets, cross sections, and neutron transport are studied to estimate the backgrounds of v-bare signal.

  1. Spectral editing for in vivo 13C magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Xiang, Yun; Shen, Jun

    2012-01-01

    In vivo detection of carboxylic/amide carbons is a promising technique for studying cerebral metabolism and neurotransmission due to the very low RF power required for proton decoupling. In the carboxylic/amide region, however, there is severe spectral overlap between acetate C1 and glutamate C5, complicating studies that use acetate as an astroglia-specific substrate. There are no known in vivo MRS techniques that can spectrally resolve acetate C1 and glutamate C5 singlets. In this study, we propose to spectrally separate acetate C1 and glutamate C5 by a two-step J-editing technique after introducing homonuclear 13C- 13C scalar coupling between carboxylic/amide carbons and aliphatic carbons. By infusing [1,2- 13C 2]acetate instead of [1- 13C]acetate the acetate doublet can be spectrally edited because of the large separation between acetate C2 and glutamate C4 in the aliphatic region. This technique can be applied to studying acetate transport and metabolism in brain in the carboxylic/amide region without spectral interference.

  2. Does the Shuram δ13C excursion record Ediacaran oxygenation?

    NASA Astrophysics Data System (ADS)

    Husson, J. M.; Maloof, A. C.; Schoene, B.; Higgins, J. A.

    2013-12-01

    The most negative carbon isotope excursion in Earth history is found in carbonate rocks of the Ediacaran Period (635-542 Ma). Known colloquially as the the 'Shuram' excursion, workers have long noted its tantalizing, broad concordance with the rise of abundant macro-scale fossils in the rock record, variously interpreted as animals, giant protists, macro-algae and lichen, and known as the 'Ediacaran Biota.' Thus, the Shuram excursion has been interpreted by many in the context of a dramatically changing redox state of the Ediacaran oceans - e.g., a result of methane cycling in a low O2 atmosphere, the final destruction of a large pool of recalcitrant dissolved organic carbon (DOC), and the step-wise oxidation of the Ediacaran oceans. More recently, diagenetic interpretations of the Shuram excursion - e.g. sedimentary in-growth of very δ13C depleted authigenic carbonates, meteoric alteration of Ediacaran carbonates, late-stage burial diagenesis - have challenged the various Ediacaran redox models. A rigorous geologic context is required to discriminate between these explanatory models, and determine whether the Shuram excursion can be used to evaluate terminal Neoproterozoic oxygenation. Here, we present chemo-stratigraphic data (δ13C, δ18O, δ44/42Ca and redox sensitive trace element abundances) from 12 measured sections of the Ediacaran-aged Wonoka Formation (Fm.) of South Australia that require a syn-depositional age for the extraordinary range of δ13C values (-12 to +4‰) observed in the formation. In some locations, the Wonoka Fm. is ~700 meters (m) of mixed shelf limestones and siliclastics that record the full 16 ‰ δ13C excursion in a remarkably consistent fashion across 100s of square kilometers of basin area. Fabric-altering diagenesis, where present, occurs at the sub-meter vertical scale, only results in sub-permil offsets in δ13C and cannot be used to explain the full δ13C excursion. In other places, the Wonoka Fm. is host to deep (1 km

  3. Laser cooling of {sup 173}Yb for isotope separation and precision hyperfine spectroscopy

    SciTech Connect

    Das, Dipankar; Natarajan, Vasant

    2007-12-15

    The hyperfine transitions in the 399 nm {sup 1}S{sub 0}{r_reversible}{sup 1}P{sub 1} line in {sup 173}Yb overlap with the transition in {sup 172}Yb. We use transverse laser cooling on this line to selectively deflect {sup 173}Yb atoms from a thermal beam containing both isotopes. We then use an acousto-optic modulator to span the frequency difference between the hyperfine transitions, and hence measure hyperfine structure in the {sup 1}P{sub 1} state. Our precise values for the hyperfine constants, A{sub 173}=57.693{+-}0.006 MHz and B{sub 173}=609.028{+-}0.056 MHz, improve previous values significantly.

  4. Optical hyperpolarization of 13C nuclear spins in nanodiamond ensembles

    NASA Astrophysics Data System (ADS)

    Chen, Q.; Schwarz, I.; Jelezko, F.; Retzker, A.; Plenio, M. B.

    2015-11-01

    Dynamical nuclear polarization holds the key for orders of magnitude enhancements of nuclear magnetic resonance signals which, in turn, would enable a wide range of novel applications in biomedical sciences. However, current implementations of DNP require cryogenic temperatures and long times for achieving high polarization. Here we propose and analyze in detail protocols that can achieve rapid hyperpolarization of 13C nuclear spins in randomly oriented ensembles of nanodiamonds at room temperature. Our protocols exploit a combination of optical polarization of electron spins in nitrogen-vacancy centers and the transfer of this polarization to 13C nuclei by means of microwave control to overcome the severe challenges that are posed by the random orientation of the nanodiamonds and their nitrogen-vacancy centers. Specifically, these random orientations result in exceedingly large energy variations of the electron spin levels that render the polarization and coherent control of the nitrogen-vacancy center electron spins as well as the control of their coherent interaction with the surrounding 13C nuclear spins highly inefficient. We address these challenges by a combination of an off-resonant microwave double resonance scheme in conjunction with a realization of the integrated solid effect which, together with adiabatic rotations of external magnetic fields or rotations of nanodiamonds, leads to a protocol that achieves high levels of hyperpolarization of the entire nuclear-spin bath in a randomly oriented ensemble of nanodiamonds even at room temperature. This hyperpolarization together with the long nuclear-spin polarization lifetimes in nanodiamonds and the relatively high density of 13C nuclei has the potential to result in a major signal enhancement in 13C nuclear magnetic resonance imaging and suggests functionalized and hyperpolarized nanodiamonds as a unique probe for molecular imaging both in vitro and in vivo.

  5. Site-specific φ- and ψ-torsion angle determination in a uniformly/extensively 13C- and 15N-labeled peptide

    NASA Astrophysics Data System (ADS)

    Wi, Sungsool; Spano, Justin

    2011-10-01

    A solid-state rotational-echo double resonance (REDOR) NMR method was introduced to identify the ϕ- and ψ-torsion angle from a 1H- 15N or 1H- 13C' spin system of alanine-like residues in a selectively, uniformly, or extensively 15N-/ 13C-labeled peptide. When a C α( i) or a 15N peak is site-specifically obtainable in the NMR spectrum of a uniformly 15N/ 13C-labeled sample system, the ψ- or ϕ-torsion angle specified by the conformational structure of peptide geometry involving 15N( i)- 1H αi - 15N( i + 1) or 13C'( i - 1)- 1H Ni- 13C'( i) spin system can be identified based on 13C α- or 15N-detected 1H α- 15N or 1H N- 13C REDOR experiment. This method will conveniently be utilized to identify major secondary motifs, such as α-helix, β-sheet, and β-turn, from a uniformly 15N-/ 13C-labled peptide sample system. When tested on a 13C-/ 15N-labeled model system of a three amino acid peptide Gly-[U- 13C, 15N]Ala-[U- 13C, 15N]Leu, the ψ-angle of alanine obtained experimentally, ψ = -40 ± 30°, agreed reasonably well with the X-ray determined angle, ψ = -39°.

  6. Hadronic light-by-light scattering in muonium hyperfine splitting

    SciTech Connect

    Karshenboim, S. G.; Shelyuto, V. A.; Vainshtein, A. I.

    2008-09-15

    We consider an impact of hadronic light-by-light scattering on the muonium hyperfine structure. A shift of the hyperfine interval {delta}{nu}(Mu){sub HLBL} is calculated with the light-by-light scattering approximated by the exchange of pseudoscalar and pseudovector mesons. Constraints from the operator product expansion in QCD are used to fix parameters of the model similar to the one used earlier for the hadronic light-by-light scattering in calculations of the muon anomalous magnetic moment. The pseudovector exchange is dominant in the resulting shift, {delta}{nu}(Mu){sub HLBL}=-0.0065(10) Hz. Although the effect is tiny it is useful in understanding the level of hadronic uncertainties.

  7. Synthesis of [1-.sup.13C]pyruvic acid], [2-.sup.13C]pyruvic acid], [3-.sup.13C]pyruvic acid] and combinations thereof

    DOEpatents

    Martinez, Rodolfo A. , Unkefer; Clifford J. , Alvarez; Marc A.

    2012-06-12

    The present invention is directed to the labeled compounds, ##STR00001## wherein C* is each either .sup.13C and .sup.12C where at least one C* is .sup.13C, each hydrogen of the methylene group is hydrogen or deuterium, the methyl group includes either zero or three deuterium atoms, Q is sulfide, sulfinyl, or sulfone, Z is an aryl group such as 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, or a phenyl group ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently either hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group such as NH.sub.2, NHR and NRR' where R and R' are each independently either a C.sub.1-C.sub.4 lower alkyl, a phenyl, and an alkoxy group, and the methyl group can include either zero or three deuterium atoms. The present invention is also directed to the labeled compounds ##STR00003##

  8. First observation of two hyperfine transitions in antiprotonic 3He

    PubMed Central

    Friedreich, S.; Barna, D.; Caspers, F.; Dax, A.; Hayano, R.S.; Hori, M.; Horváth, D.; Juhász, B.; Kobayashi, T.; Massiczek, O.; Sótér, A.; Todoroki, K.; Widmann, E.; Zmeskal, J.

    2011-01-01

    We report on the first experimental results for microwave spectroscopy of the hyperfine structure of p¯3He+. Due to the helium nuclear spin, p¯3He+ has a more complex hyperfine structure than p¯4He+, which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the three-body quantum electrodynamics (QED) theory. Two out of four super-super-hyperfine (SSHF) transition lines of the (n,L)=(36,34) state were observed. The measured frequencies of the individual transitions are 11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current theoretical values, but still within their estimated errors. Although the experimental uncertainty for the difference of these frequencies is still very large as compared to that of theory, its measured value agrees with theoretical calculations. This difference is crucial to be determined because it is proportional to the magnetic moment of the antiproton. PMID:21822351

  9. Dynamic nuclear polarization-enhanced 1H–13C double resonance NMR in static samples below 20 K

    PubMed Central

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

    2012-01-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H–13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H–13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H–13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr–Purcell experiments and numerical simulations of Carr–Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C–13C exchange spectrum of selectively 13C-labeled β-amyloid fibrils. PMID:22743540

  10. Improved measurement of the hyperfine structure of the laser cooling level 4f^{12}(^3H_6)5d_{5/2}6s^2 (J=9/2) in {}^{169}_{ 69}{{Tm}}

    NASA Astrophysics Data System (ADS)

    Fedorov, S. A.; Vishnyakova, G. A.; Kalganova, E. S.; Sukachev, D. D.; Golovizin, A. A.; Tregubov, D. O.; Khabarova, K. Yu.; Akimov, A. V.; Kolachevsky, N. N.; Sorokin, V. N.

    2015-12-01

    We report on an improved measurement of the hyperfine constant of the 4f^{12}(^3 H_6)5d_{5/2}6s^2 (J=9/2) excited state of {}^{169}_{ 69}{{Tm}} which is involved in the second-stage laser cooling of Tm. To measure the absolute value of the hyperfine splitting interval, we used Doppler-free frequency modulation saturated absorption spectroscopy of Tm atoms in a vapor cell. The sign of the hyperfine constant was determined independently by spectroscopy of laser-cooled Tm atoms. The hyperfine constant of the level was determined to be A_J=-422.112(32) {MHz} from the energy difference between the two hyperfine sublevels, -2110.56(16) {MHz}. In relation to the saturated absorption measurement, we quantitatively treat contributions of various mechanisms to the line broadening and shift. We consider power broadening in the case when Zeeman sublevels of atomic levels are taken into account. We also discuss the line broadening due to frequency modulation and relative intensities of transitions in saturated absorption experiments.

  11. 13CFLUX2—high-performance software suite for 13C-metabolic flux analysis

    PubMed Central

    Weitzel, Michael; Nöh, Katharina; Dalman, Tolga; Niedenführ, Sebastian; Stute, Birgit; Wiechert, Wolfgang

    2013-01-01

    Summary: 13C-based metabolic flux analysis (13C-MFA) is the state-of-the-art method to quantitatively determine in vivo metabolic reaction rates in microorganisms. 13CFLUX2 contains all tools for composing flexible computational 13C-MFA workflows to design and evaluate carbon labeling experiments. A specially developed XML language, FluxML, highly efficient data structures and simulation algorithms achieve a maximum of performance and effectiveness. Support of multicore CPUs, as well as compute clusters, enables scalable investigations. 13CFLUX2 outperforms existing tools in terms of universality, flexibility and built-in features. Therewith, 13CFLUX2 paves the way for next-generation high-resolution 13C-MFA applications on the large scale. Availability and implementation: 13CFLUX2 is implemented in C++ (ISO/IEC 14882 standard) with Java and Python add-ons to run under Linux/Unix. A demo version and binaries are available at www.13cflux.net. Contact: info@13cflux.net or k.noeh@fz-juelich.de Supplementary information: Supplementary data are available at Bioinformatics online. PMID:23110970

  12. 13C NMR spectroscopy of the insoluble carbon of carbonaceous chondrites.

    PubMed

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

    1987-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  14. High-resolution magneto-optical spectroscopy of LiYF74:3+167Er, 3+166Er and analysis of hyperfine structure of ultranarrow optical transitions

    NASA Astrophysics Data System (ADS)

    Gerasimov, K. I.; Minnegaliev, M. M.; Malkin, B. Z.; Baibekov, E. I.; Moiseev, S. A.

    2016-08-01

    We performed high-resolution magneto-optical spectroscopy of the hyperfine transitions from 15/2 4I to the 13/2 4I and 9/2 4I multiplets of 3+167Er and 3+166Er in an isotopically purified LiYF74 crystal in various external magnetic fields up to 0.7 T. The obtained experimental results are interpreted in the framework of the generalized theoretical approach. The derived model successfully explains all the experimentally observed optical hyperfine transitions by using a single set of basic parameters found for the crystal-field interaction, magnetic dipole and electric quadrupole hyperfine interactions, together with Zeeman interactions at different orientations of the external magnetic field. A number of the studied quantum transitions appears to be promising for use in Raman quantum storage at optical telecommunication wavelengths.

  15. 13C NMR spectra of pyridine chalcone analogs

    NASA Astrophysics Data System (ADS)

    Jovanović, B. Ž.; Mišić-Vuković, M.; Marinković, A. D.; Csanádi, J.

    1999-05-01

    13C NMR spectra of two series of pyridine chalcone analogs were determined in deuterated dimethylsulphoxide (DMSO-d 6). It was established that these compounds were in more stable E-configurations except for the 4-pyridalacetophenone which was in Z-configuration. On the basis of the Hammett correlations of 13C NMR chemical shifts of the ethylenic bond carbon atoms and the σ values for the pyridine "aza" groups, the polarization of ethylenic bonds were discussed. It was established that the opposite effect of the pyridine substituents at the electronic density distribution in pyridalacetophenone and cinnamoylpyridines depends on its direct bonding to the ethylenic carbon or the transmission electronic effects via the carbonyl group, respectively.

  16. Metabolic Imaging in the Anesthetized Rat Brain Using Hyperpolarized [1-13C] Pyruvate and [1-13C] Ethyl Pyruvate

    PubMed Central

    Hurd, Ralph E.; Yen, Yi-Fen; Mayer, Dirk; Chen, Albert; Wilson, David; Kohler, Susan; Bok, Robert; Vigneron, Daniel; Kurhanewicz, John; Tropp, James; Spielman, Daniel; Pfefferbaum, Adolf

    2010-01-01

    Formulation, polarization, and dissolution conditions were developed to obtain a stable hyperpolarized solution of [1-13C]-ethyl pyruvate. A maximum tolerated concentration and injection rate were determined, and 13C spectroscopic imaging was used to compare the uptake of hyperpolarized [1-13C]-ethyl pyruvate relative to hyperpolarized [1-13C]-pyruvate into anesthetized rat brain. Hyperpolarized [1-13C]-ethyl pyruvate and [1-13C]-pyruvate metabolic imaging in normal brain is demonstrated and quantified in this feasibility and range-finding study. PMID:20432284

  17. Experimental design principles for isotopically instationary 13C labeling experiments.

    PubMed

    Nöh, Katharina; Wiechert, Wolfgang

    2006-06-01

    13C metabolic flux analysis (MFA) is a well-established tool in Metabolic Engineering that found numerous applications in recent years. However, one strong limitation of the current method is the requirement of an-at least approximate-isotopic stationary state at sampling time. This requirement leads to a principle lower limit for the duration of a 13C labeling experiment. A new methodological development is based on repeated sampling during the instationary transient of the 13C labeling dynamics. The statistical and computational treatment of such instationary experiments is a completely new terrain. The computational effort is very high because large differential equations have to be solved and, moreover, the intracellular pool sizes play a significant role. For this reason, the present contribution works out principles and strategies for the experimental design of instationary experiments based on a simple example network. Hereby, the potential of isotopically instationary experiments is investigated in detail. Various statistical results on instationary flux identifiability are presented and possible pitfalls of experimental design are discussed. Finally, a framework for almost optimal experimental design of isotopically instationary experiments is proposed which provides a practical guideline for the analysis of large-scale networks.

  18. Diethers enriched in 13C suggest carbon-limitation at the Lost City Hydrothermal Field

    NASA Astrophysics Data System (ADS)

    Bradley, A. S.; Hayes, J. M.; Summons, R. E.

    2004-12-01

    Active and inactive carbonate vent structures from the Lost City Hydrothermal Field (LCHF) contain up to 0.6% organic carbon including diverse lipids. Values of δ 13C for total organic carbon (TOC) range from -18.7‰ vs. VPDB at the active, high-temperature vent known as "The Beehive" (90° C), to -3.1‰ at Marker 7 (active, 70° C). Samples with relatively high levels of 13C also contained high amounts of isoprenoidal and nonisoprenoidal diethers. Samples more depleted in 13C lacked or contained low amounts of these diethers. The correlation between high 13C and abundant diethers is supported by compound-specific isotopic analyses. Archaeal and bacterial diethers are enriched in 13C relative to photosynthetically derived marine carbon. The biomarkers sn-2 hydroxyarchaeol, sn-3 hydroxyarchaeol, and dihydroxyarchaeol - considered diagnostic for methane-cycling archaea - had δ values ranging from -8.5 to +4.8‰ . Phylogenetic data confirms the presence at these vents of a single group of methanogens, related to the Methanosarcinales (Schrenk et al., 2004). Diethers with non-isoprenoidal alkyl chains are also present, are of presumed bacterial origin, and may indicated the presence of sulfate-reducing bacteria. Values of δ for these compounds range from -7.3 to +1.0‰ . At the Beehive vent, diether lipids are absent and the TOC is depleted in 13C. Coexistence of isotopically similar hydroxyarchaeols and nonisoprenoidal glycerol diethers is typical of marine, cold-seep environments at which concentrations of H2 are low and methane is oxidized anaerobically. At the LCHF, however, concentrations of H2 in pore waters reach 15 mM (Proskurowski et al., 2003). This H2, produced by serpentinization reactions, drives production (rather than oxidation) of methane. Simultaneously, sulfate-reducing bacteria can flourish as carbon-fixing autotrophs. Under such conditions, carbon may be the limiting substrate, its nearly complete consumption accounting for the enrichment of

  19. 13C solid-state NMR chemical shift anisotropy analysis of the anomeric carbon in carbohydrates.

    PubMed

    Chen, Ying-Ying; Luo, Shun-Yuan; Hung, Shang-Cheng; Chan, Sunney I; Tzou, Der-Lii M

    2005-03-21

    (13)C NMR solid-state structural analysis of the anomeric center in carbohydrates was performed on six monosaccharides: glucose (Glc), mannose (Man), galactose (Gal), galactosamine hydrochloride (GalN), glucosamine hydrochloride (GlcN), and N-acetyl-glucosamine (GlcNAc). In the 1D (13)C cross-polarization/magic-angle spinning (CP/MAS) spectrum, the anomeric center C-1 of these carbohydrates revealed two well resolved resonances shifted by 3-5ppm, which were readily assigned to the anomeric alpha and beta forms. From this experiment, we also extracted the (13)C chemical shift anisotropy (CSA) tensor elements of the two forms from their spinning sideband intensities, respectively. It was found out that the chemical shift tensor for the alpha anomer was more axially symmetrical than that of the beta form. A strong linear correlation was obtained when the ratio of the axial asymmetry of the (13)C chemical shift tensors of the two anomeric forms was plotted in a semilogarithmic plot against the relative population of the two anomers. Finally, we applied REDOR spectroscopy to discern whether or not there were any differences in the sugar ring conformation between the anomers. Identical two-bond distances of 2.57A (2.48A) were deduced for both the alpha and beta forms in GlcNAc (GlcN), suggesting that the two anomers have essentially identical sugar ring scaffolds in these sugars. In light of these REDOR distance measurements and the strong correlation observed between the ratio of the axial asymmetry parameters of the (13)C chemical shift tensors and the relative population between the two anomeric forms, we concluded that the anomeric effect arises principally from interaction of the electron charge clouds between the C-1-O-5 and the C-1-O-1 bonds in these monosaccharides.

  20. Two Techniques for Estimating Deglacial Mean-Ocean δ13 C Change from the Same Set of 493 Benthic δ13C Records

    NASA Astrophysics Data System (ADS)

    Peterson, C. D.; Lisiecki, L. E.; Gebbie, G.

    2013-12-01

    The crux of carbon redistribution over the deglaciation centers on the ocean, where the isotopic signature of terrestrial carbon (δ13C terrestrial carbon = -25‰) is observed as a 0.3-0.7‰ shift in benthic foraminiferal δ13C. Deglacial mean-ocean δ13C estimates vary due to different subsets of benthic δ13C data and different methods of weighting the mean δ13C by volume. Here, we present a detailed 1-to-1 comparison of two methods of calculating mean δ13C change and uncertainty estimates using the same set of 493 benthic Cibicidoides spp. δ13C measurements for the LGM and Late Holocene. The first method divides the ocean into 8 regions, and uses simple line fits to describe the distribution of δ13C data for each timeslice over 0.5-5 km depth. With these line fits, we estimate the δ13C value at 100-meter intervals and weight those estimates by the regional volume at each depth slice. The mean-ocean δ13C is the sum of these volume-weighted regional δ13C estimates and the uncertainty of these mean-ocean δ13C estimates is computed using Monte Carlo simulations. The whole-ocean δ13C change is estimated using extrapolated surface- and deep-ocean δ13C estimates, and an assumed δ13C value for the Southern Ocean. This method yields an estimated LGM-to-Holocene change of 0.38×0.07‰ for 0.5-5km and 0.35×0.16‰ for the whole ocean (Peterson et al., 2013, submitted to Paleoceanography). The second method reconstructs glacial and modern δ13C by combining the same data compilation as above with a steady-state ocean circulation model (Gebbie, 2013, submitted to Paleoceanography). The result is a tracer distribution on a 4-by-4 degree horizontal resolution grid with 23 vertical levels, and an estimate of the distribution's uncertainty that accounts for the distinct modern and glacial water-mass geometries. From both methods, we compare the regional δ13C estimates (0.5-5 km), surface δ13C estimates (0-0.5 km), deep δ13C estimates (>5 km), Southern Ocean

  1. Design, total synthesis, and evaluation of C13-C14 cyclopropane analogues of (+)-discodermolide.

    PubMed

    Smith, Amos B; Xian, Ming; Liu, Fenghua

    2005-10-13

    [structure: see text] The design, total synthesis, and biological evaluation of two C13-C14-cyclopropyl analogues [(+)-1 and (+)-2] of (+)-discodermolide have been achieved. Key features of the syntheses include highly stereoselective, hydroxyl-directed cyclopropanations of vinyl iodides and higher order cuprate-mediated cross-coupling reactions between cyclopropyl iodides and alkyl iodides. Biological evaluation revealed that neither orientation of the cyclopropyl methylene completely substitutes for the C14 methyl found in (+)-discodermolide (3).

  2. Measurement of multiple psi torsion angles in uniformly 13C,15N-labeled alpha-spectrin SH3 domain using 3D 15N-13C-13C-15N MAS dipolar-chemical shift correlation spectroscopy.

    PubMed

    Ladizhansky, Vladimir; Jaroniec, Christopher P; Diehl, Annette; Oschkinat, Hartmut; Griffin, Robert G

    2003-06-01

    We demonstrate the simultaneous measurement of several backbone torsion angles psi in the uniformly (13)C,(15)N-labeled alpha-Spectrin SH3 domain using two different 3D 15N-13C-13C-15N dipolar-chemical shift magic-angle spinning (MAS) NMR experiments. The first NCCN experiment utilizes double quantum (DQ) spectroscopy combined with the INADEQUATE type 13C-13C chemical shift correlation. The decay of the DQ coherences formed between 13C'(i) and 13C(alphai) spin pairs is determined by the "correlated" dipolar field due to 15N(i)-13C(alphai) and 13C'(i)-15N(i+1) dipolar couplings and is particularly sensitive to variations of the torsion angle in the regime |psi| > 140 degrees. However, the ability of this experiment to constrain multiple psi-torsion angles is limited by the resolution of the 13C(alpha)-(13)CO correlation spectrum. This problem is partially addressed in the second approach described here, which is an NCOCA NCCN experiment. In this case the resolution is enhanced by the superior spectral dispersion of the 15N resonances present in the 15N(i+1)-13C(alphai) part of the NCOCA chemical shift correlation spectrum. For the case of the 62-residue alpha-spectrin SH3 domain, we determined 13 psi angle constraints with the INADEQUATE NCCN experiment and 22 psi constraints were measured in the NCOCA NCCN experiment.

  3. Hyperfine Splittings in the Near-Infrared Spectrum of 14NH_3

    NASA Astrophysics Data System (ADS)

    Twagirayezu, Sylvestre; Sears, Trevor; Hall, Gregory

    2016-06-01

    Sub-Doppler, saturation dip, measurements of transitions in the ν_1 + ν_3 band of 14NH_3 have been made by frequency comb-referenced diode laser absorption spectroscopy. The observed spectra exhibit either resolved or partially-resolved hyperfine splittings that are primarily determined by the 14N quadrupole coupling in the molecule. Modeling of the line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the upper state level has splittings similar to that of the same rotational level in the ground state. The data provide accurate frequencies for the line positions and the observed hyperfine splittings can be used to make or confirm rotational assignments. Of all the measurements, one transition, pP(5,4)_a at 195 994.73457 GHz, exhibits hyperfine structure which does not conform to that expected based on extrapolation from the known lower state hyperfine splittings. Examination of the known vibration-rotation level structure near the upper state energy shows that there exists a near degeneracy between this level and one in the ν_1 + 2ν_4 manifold which is of the appropriate symmetry to be mixed by magnetic hyperfine terms that couple ortho- and para- modifications of the molecule. It is possible that the unusual hyperfine splittings are a consequence of ortho-paro mixing, which has been predicted, but not previously seen in ammonia and further experimental measurements to investigate this possibility are ongoing. Acknowledgments: 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 within the Office of Basic Energy Sciences.

  4. Using Neural Networks for 13C NMR Chemical Shift Prediction-Comparison with Traditional Methods

    NASA Astrophysics Data System (ADS)

    Meiler, Jens; Maier, Walter; Will, Martin; Meusinger, Reinhard

    2002-08-01

    Interpretation of 13C chemical shifts is essential for structure elucidation of organic molecules by NMR. In this article, we present an improved neural network approach and compare its performance to that of commonly used approaches. Specifically, our recently proposed neural network ( J. Chem. Inf. Comput. Sci. 2000, 40, 1169-1176) is improved by introducing an extended hybrid numerical description of the carbon atom environment, resulting in a standard deviation (std. dev.) of 2.4 ppm for an independent test data set of ˜42,500 carbons. Thus, this neural network allows fast and accurate 13C NMR chemical shift prediction without the necessity of access to molecule or fragment databases. For an unbiased test dataset containing 100 organic structures the accuracy of the improved neural network was compared to that of a prediction method based on the HOSE code ( hierarchically ordered spherical description of environment) using S PECI NFO. The results show the neural network predictions to be of quality (std. dev.=2.7 ppm) comparable to that of the HOSE code prediction (std. dev.=2.6 ppm). Further we compare the neural network predictions to those of a wide variety of other 13C chemical shift prediction tools including incremental methods (C HEMD RAW, S PECT OOL), quantum chemical calculation (G AUSSIAN, C OSMOS), and HOSE code fragment-based prediction (S PECI NFO, ACD/CNMR, P REDICTI T NMR) for the 47 13C-NMR shifts of Taxol, a natural product including many structural features of organic substances. The smallest standard deviations were achieved here with the neural network (1.3 ppm) and S PECI NFO (1.0 ppm).

  5. Compartmentation of glycogen metabolism revealed from 13C isotopologue distributions

    PubMed Central

    2011-01-01

    Background Stable isotope tracers are used to assess metabolic flux profiles in living cells. The existing methods of measurement average out the isotopic isomer distribution in metabolites throughout the cell, whereas the knowledge of compartmental organization of analyzed pathways is crucial for the evaluation of true fluxes. That is why we accepted a challenge to create a software tool that allows deciphering the compartmentation of metabolites based on the analysis of average isotopic isomer distribution. Results The software Isodyn, which simulates the dynamics of isotopic isomer distribution in central metabolic pathways, was supplemented by algorithms facilitating the transition between various analyzed metabolic schemes, and by the tools for model discrimination. It simulated 13C isotope distributions in glucose, lactate, glutamate and glycogen, measured by mass spectrometry after incubation of hepatocytes in the presence of only labeled glucose or glucose and lactate together (with label either in glucose or lactate). The simulations assumed either a single intracellular hexose phosphate pool, or also channeling of hexose phosphates resulting in a different isotopic composition of glycogen. Model discrimination test was applied to check the consistency of both models with experimental data. Metabolic flux profiles, evaluated with the accepted model that assumes channeling, revealed the range of changes in metabolic fluxes in liver cells. Conclusions The analysis of compartmentation of metabolic networks based on the measured 13C distribution was included in Isodyn as a routine procedure. The advantage of this implementation is that, being a part of evaluation of metabolic fluxes, it does not require additional experiments to study metabolic compartmentation. The analysis of experimental data revealed that the distribution of measured 13C-labeled glucose metabolites is inconsistent with the idea of perfect mixing of hexose phosphates in cytosol. In contrast

  6. The delta 13C record of Devonian to Permian carbonates

    NASA Astrophysics Data System (ADS)

    Buggisch, W.

    2003-04-01

    A δ13Ccarb curve will be presented for samples spanning the time interval from the Silurian/Devonian to the Permian/Triassic boundary. Reliable data are usually based on analyses of brachiopod shells. Because of the huge reservoir of carbon in carbonates, also whole rock samples are suitable for stable carbon isotope analyses if they are not altered by meteoric water or by incorporation of re-oxidized organic carbon during diagenesis. There are several possibilities to test the quality of the data: (1) comparison of the δ13C record of whole rock samples with samples from brachiopod shells, (2) with the organic record, (3) analyses of the same time interval in different sections. If the same pattern of isotope data is observed in separa-ted palaeogeographic settings, it is probably caused by a change in the global carbon reservoir. Reliable δ13C data will be presented for the Devonian, Mississippian and Middle to Late Permian. During Pennsylvanian and Early Permian most carbonates were affected by meteoric diagenesis due to the large glacio-eustatic sea level changes of the Permo-Carboniferous glaciation. Long term variations (mean values for 10 Ma) are known from literature. Devonian δ13C values are about 0 to 2 ppm (V-PDB) they increase up to 5 to 6 ppm during the Mississippian - Pennsylvanian transition and drop sharply at the Permian Triassic boundary. The Devonian - Carboniferous trend is probably at least partly due to the evolution of land plants. Short term variations in the range of 0.1 to 1 Ma modify the long term trend significantly. Large positive excursions of δ13C up to 5 or 6 ppm are known from the Silurian - Devonian boundary and during the Middle Tournaisian of Laurentia and Europe. Many positive excursions of a magnitude of 2 to 3 ppm are observed, some are verified worldwide as for instance at the Frasnian - Famennian boundary which coincides with one of the largest extinction events in earth history. Short time variations in the isotopic

  7. S-Factor of radiative р 13C capture

    NASA Astrophysics Data System (ADS)

    Dubovichenko, S. B.

    2012-06-01

    The possibility of description of experimental data on the astrophysical S-factor of radiative р 13C capture within the framework of the potential cluster model with forbidden states is analyzed at energies in the range 0.03-0.8 MeV. It is demonstrated that the behavior of the astrophysical S-factor can be explained based on the Е1-transition to the bound 3 P 1 state of the 14N nucleus in the р 13С channel from the 3 S 1 wave of р 13С scattering at resonant energy of 0.55 MeV (l.s.).

  8. Phenyl galactopyranosides - 13C CPMAS NMR and conformational analysis using genetic algorithm

    NASA Astrophysics Data System (ADS)

    Wałejko, Piotr; Paradowska, Katarzyna; Bukowicki, Jarosław; Witkowski, Stanisław; Wawer, Iwona

    2015-08-01

    Structural analyses of four compounds (phenyl 2,3,4,6-tetra-O-acetyl-β-D-galactopyranoside (1), phenyl β-D-galactopyranoside (2), phenyl 2,3,4,6-tetra-O-acetyl-α-D-galactopyranoside (3) and phenyl α-D-galactopyranoside (4)) have been performed using solid-state 13C MAS NMR spectroscopy and theoretical methods. Conformational analysis involved grid search and genetic algorithm (GAAGS). Low-energy conformers found by GAAGS were further optimized by DFT and chemical shifts were calculated using GIAO/DFT approach. 13C CPMAS NMR chemical shift of carbon C2 is indicative of the glycoside torsional angle. Separated or merged resonances of C2 and C6 suggest free rotation of phenyl ring in the solid phase.

  9. NMR at cryogenic temperatures: A {sup 13}C NMR study of ferrocene

    SciTech Connect

    Orendt, A.M.; Facelli, J.C.; Jiang, Y.J.; Grant, D.M.

    1998-09-24

    A new cryogenic apparatus is described that can be used to obtain NMR spectra at temperatures down to 8--10 K. The static solid {sup 13}C NMR spectrum of ferrocene is recorded at that temperature. Spectra recorded at higher temperatures show that ferrocene is still freely rotating about its 5-fold symmetry axis on the {sup 13}C NMR time scale at 45--50 K. A comparison of the principal values of the {sup 13}C chemical-shift tensor obtained from the room- and low-temperature spectra of ferrocene indicates that the lowest frequency chemical shift principal component, {delta}{sub 33}, is tilted off this symmetry axis by approximately 12{degree}. Quantum chemical calculations of the chemical-shift tensor, completed on structures of ferrocene from the literature as well as on optimized structures with the cyclopentadienyl rings locked in both the staggered and eclipsed arrangements, predict the angle between the {delta}{sub 33} direction and the rotation axis to be between 11 and 15{degree}, depending upon the geometry used in the calculation. The calculations also predict the sign of the angular perturbation, information not obtained from the experiment. An explanation of this angular change in the {delta}{sub 33} direction is provided by the composition of the molecular orbitals.

  10. Hyperfine anomalies of HCN in cold dark clouds

    SciTech Connect

    Walmsley, C.M.; Churchwell, E.; Nash, A.; Fitzpatrick, E.

    1982-07-15

    We report observations of the J = 1..-->..0 line of HCN measured toward six positions in nearby low-temperature dark clouds. The measured relative intensities of the hyperfine components of the J = 1..-->..0 line are anomalous in that the F = 0..-->..1 transition is stronger than would be expected if all three components (F = 2..-->..1, F = 1..-->..1, F = 0..-->..1) had equal excitation temperatures. Differences of approximately 20% in the populations per sublevel of J = 1 could account for the observations. The results are in contrast to the situation observed in warmer molecular clouds associated with H II regions where the F = 1..-->..1 line is anomalously weak. The apparent overpopulation of J = 1, F = 0 in dark clouds may be related to the phenomenon observed in the J = 1..-->..0 transitions of HCO/sup +/ and HNC in the same objects where /sup 13/C substituted version of these species is found to be stronger than the /sup 12/C species.

  11. Density functional theory predictions of isotropic hyperfine coupling constants.

    PubMed

    Hermosilla, L; Calle, P; García de la Vega, J M; Sieiro, C

    2005-02-17

    The reliability of density functional theory (DFT) in the determination of the isotropic hyperfine coupling constants (hfccs) of the ground electronic states of organic and inorganic radicals is examined. Predictions using several DFT methods and 6-31G, TZVP, EPR-III and cc-pVQZ basis sets are made and compared to experimental values. The set of 75 radicals here studied was selected using a wide range of criteria. The systems studied are neutral, cationic, anionic; doublet, triplet, quartet; localized, and conjugated radicals, containing 1H, 9Be, 11B, 13C, 14N, 17O, 19F, 23Na, 25Mg, 27Al, 29Si, 31P, 33S, and 35Cl nuclei. The considered radicals provide 241 theoretical hfcc values, which are compared with 174 available experimental ones. The geometries of the studied systems are obtained by theoretical optimization using the same functional and basis set with which the hfccs were calculated. Regression analysis is used as a basic and appropriate methodology for this kind of comparative study. From this analysis, we conclude that DFT predictions of the hfccs are reliable for B3LYP/TZVP and B3LYP/EPR-III combinations. Both functional/basis set scheme are the more useful theoretical tools for predicting hfccs if compared to other much more expensive methods.

  12. Design of a sup 13 C (1H) RF probe for monitoring the in vivo metabolism of (1- sup 13 C)glucose in primate brain

    SciTech Connect

    Hammer, B.E.; Sacks, W.; Bigler, R.E.; Hennessy, M.J.; Sacks, S.; Fleischer, A.; Zanzonico, P.B. )

    1990-01-01

    The design of an RF probe suitable for obtaining proton-decoupled {sup 13}C spectra from a subhuman primate brain is described. Two orthogonal saddle coils, one tuned to the resonant frequency of {sup 13}C and the other to the resonant frequency of 1H, were used to monitor the in vivo metabolism of (1-{sup 13}C)glucose in rhesus monkey brain at 2.1 T. Difference spectra showed the appearance of {sup 13}C-enriched glutamate and glutamine 30 to 40 min after a bolus injection of (1-{sup 13}C)glucose.

  13. Measuring changes in substrate utilization in the myocardium in response to fasting using hyperpolarized [1-13C]butyrate and [1-13C]pyruvate

    PubMed Central

    Bastiaansen, Jessica A. M.; Merritt, Matthew E.; Comment, Arnaud

    2016-01-01

    Cardiac dysfunction is often associated with a shift in substrate preference for ATP production. Hyperpolarized (HP) 13C magnetic resonance spectroscopy (MRS) has the unique ability to detect real-time metabolic changes in vivo due to its high sensitivity and specificity. Here a protocol using HP [1-13C]pyruvate and [1-13C]butyrate is used to measure carbohydrate versus fatty acid metabolism in vivo. Metabolic changes in fed and fasted Sprague Dawley rats (n = 36) were studied at 9.4 T after tail vein injections. Pyruvate and butyrate competed for acetyl-CoA production, as evidenced by significant changes in [13C]bicarbonate (−48%), [1-13C]acetylcarnitine (+113%), and [5-13C]glutamate (−63%), following fasting. Butyrate uptake was unaffected by fasting, as indicated by [1-13C]butyrylcarnitine. Mitochondrial pseudoketogenesis facilitated the labeling of the ketone bodies [1-13C]acetoacetate and [1-13C]β-hydroxybutyryate, without evidence of true ketogenesis. HP [1-13C]acetoacetate was increased in fasting (250%) but decreased during pyruvate co-injection (−82%). Combining HP 13C technology and co-administration of separate imaging agents enables noninvasive and simultaneous monitoring of both fatty acid and carbohydrate oxidation. This protocol illustrates a novel method for assessing metabolic flux through different enzymatic pathways simultaneously and enables mechanistic studies of the changing myocardial energetics often associated with disease. PMID:27150735

  14. Measuring changes in substrate utilization in the myocardium in response to fasting using hyperpolarized [1-(13)C]butyrate and [1-(13)C]pyruvate.

    PubMed

    Bastiaansen, Jessica A M; Merritt, Matthew E; Comment, Arnaud

    2016-01-01

    Cardiac dysfunction is often associated with a shift in substrate preference for ATP production. Hyperpolarized (HP) (13)C magnetic resonance spectroscopy (MRS) has the unique ability to detect real-time metabolic changes in vivo due to its high sensitivity and specificity. Here a protocol using HP [1-(13)C]pyruvate and [1-(13)C]butyrate is used to measure carbohydrate versus fatty acid metabolism in vivo. Metabolic changes in fed and fasted Sprague Dawley rats (n = 36) were studied at 9.4 T after tail vein injections. Pyruvate and butyrate competed for acetyl-CoA production, as evidenced by significant changes in [(13)C]bicarbonate (-48%), [1-(13)C]acetylcarnitine (+113%), and [5-(13)C]glutamate (-63%), following fasting. Butyrate uptake was unaffected by fasting, as indicated by [1-(13)C]butyrylcarnitine. Mitochondrial pseudoketogenesis facilitated the labeling of the ketone bodies [1-(13)C]acetoacetate and [1-(13)C]β-hydroxybutyryate, without evidence of true ketogenesis. HP [1-(13)C]acetoacetate was increased in fasting (250%) but decreased during pyruvate co-injection (-82%). Combining HP (13)C technology and co-administration of separate imaging agents enables noninvasive and simultaneous monitoring of both fatty acid and carbohydrate oxidation. This protocol illustrates a novel method for assessing metabolic flux through different enzymatic pathways simultaneously and enables mechanistic studies of the changing myocardial energetics often associated with disease. PMID:27150735

  15. Hyperfine-induced electric dipole contributions to the electric octupole and magnetic quadrupole atomic clock transitions

    NASA Astrophysics Data System (ADS)

    Dzuba, V. A.; Flambaum, V. V.

    2016-05-01

    Hyperfine-induced electric dipole contributions may significantly increase probabilities of otherwise very weak electric octupole and magnetic quadrupole atomic clock transitions (e.g., transitions between s and f electron orbitals). These transitions can be used for exceptionally accurate atomic clocks, quantum information processing, and the search for dark matter. They are very sensitive to new physics beyond the standard model, such as temporal variation of the fine-structure constant, the Lorentz invariance, and Einstein equivalence principle violation. We formulate conditions under which the hyperfine-induced electric dipole contribution dominates and perform calculations of the hyperfine structure and E3, M2 and the hyperfine-induced E1 transition rates for a large number of atoms and ions of experimental interest. Due to the hyperfine quenching the electric octupole clock transition in +173Yb is 2 orders of magnitude stronger than that in currently used +171Yb. Some enhancement is found in 13+143Nd, 14+149Pm, 14+147Sm, and 15+147Sm ions.

  16. Fluctuating hyperfine interactions: an updated computational implementation

    NASA Astrophysics Data System (ADS)

    Zacate, M. O.; Evenson, W. E.

    2015-04-01

    The stochastic hyperfine interactions modeling library (SHIML) is a set of routines written in the C programming language designed to assist in the analysis of stochastic models of hyperfine interactions. The routines read a text-file description of the model, set up the Blume matrix, upon which the evolution operator of the quantum mechanical system depends, and calculate the eigenvalues and eigenvectors of the Blume matrix, from which theoretical spectra of experimental techniques can be calculated. The original version of SHIML constructs Blume matrices applicable for methods that measure hyperfine interactions with only a single nuclear spin state. In this paper, we report an extension of the library to provide support for methods such as Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation, which are sensitive to interactions with two nuclear spin states. Examples will be presented that illustrate the use of this extension of SHIML to generate Mössbauer spectra for polycrystalline samples under a number of fluctuating hyperfine field models.

  17. Alkoxy radicals: Delta proton hyperfine couplingsa)

    NASA Astrophysics Data System (ADS)

    Budzinski, Edwin E.; Box, Harold C.

    1985-04-01

    Single crystals of rhamnose were x irradiated at 4.2 K and the ESR and ENDOR spectra taken at 1.6 K. A component of the ESR absorption arises from an alkoxy radical exhibiting an unusual delta proton hyperfine coupling. Parallels between the radiation-induced oxidation of certain carbohydrates and that of amino acids are pointed out.

  18. Food webs in Mongolian grasslands: the analysis of 13C and 15N natural abundances.

    PubMed

    Kohzu, Ayato; Iwata, T; Kato, M; Nishikawa, J; Wada, Eitaro; Amartuvshin, N; Namkhaidorj, B; Fujita, N

    2009-09-01

    Overgrazing often lowers species richness and productivity of grassland communities. For Mongolian grassland ecosystems, a lack of detailed information about food-web structures makes it difficult to predict the effects of overgrazing on species diversity and community composition. We analysed the delta13C and delta15N signatures of herbaceous plants, arthropods (grouped by feeding habit), wild and domestic mammals, and humans in central Mongolia to understand the predominant food-web pathways in this grassland ecosystem. The delta13C and delta15N values of mammals showed little variation within species, but varied considerably with slope position for arthropods. The apparent isotopic discrimination between body tissue and hair of mammals was estimated as 2.0 per thousand for delta13C and 2.1 per thousand for delta15N, which was large enough to cause overestimation of the trophic level of mammals if not taken into account when using hair samples to measure isotopic enrichment. PMID:19507080

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

    PubMed

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

    2014-12-01

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

  20. Spectroscopic characterization of the 1-substituted 3,3-diphenyl-4-(2'-hydroxyphenyl)azetidin-2-ones: Application of 13C NMR, 1H- 13C COSY NMR and mass spectroscopy

    NASA Astrophysics Data System (ADS)

    Singh, Girija S.; Pheko, Tshepo

    2008-08-01

    The article deals with spectroscopic characterization of azetidin-2-ones. The presence of substituents like hydroxyl, fluoro, methoxy and benzhydryl, etc., on the azetidin-2-one ring significantly affects the IR absorption and 13C NMR frequencies of the carbonyl group present in these compounds. The presence of an ester carbonyl group or too many methine protons in the molecule has been observed to limit the scope of IR and 1H NMR spectroscopy in unambiguous assignment of the structure. The application of 13C NMR, 2D NMR ( 1H- 13C COSY) and mass spectroscopy in characterization of complex azetidin-2-ones is discussed. An application of the latter two techniques is described in deciding unequivocally between an azetidin-2-one ring and chroman-2-one ring structure for the product obtained by treatment of the 1-substituted 3,3-diphenyl-4-[2'-( O-diphenylacyl)hydroxyphenyl]-2-azetidinones with ethanolic sodium hydroxide at room temperature.

  1. 13C CP MAS NMR and GIAO-CHF calculations of coumarins.

    PubMed

    Zolek, Teresa; Paradowska, Katarzyna; Wawer, Iwona

    2003-01-01

    13C cross-polarization magic-angle spinning NMR spectra were recorded for a series of solid coumarins. Ab initio calculations of shielding constants were performed with the use of GIAO-CHF method. The combined CPMAS NMR and theoretical approach was successful in characterizing solid-state conformations of coumarins; a relationship sigma (ppm) = -1.032 xdelta + 205.28 (R(2) = 0.9845) can be used to obtain structural information for coumarins, for which solid-state NMR or crystal structure data are not available.

  2. Millimeter and submillimeter wave spectra of 13C-glycolaldehydes

    NASA Astrophysics Data System (ADS)

    Haykal, I.; Motiyenko, R. A.; Margulès, L.; Huet, T. R.

    2013-01-01

    Context. Glycolaldehyde (CH2OHCHO) is the simplest sugar and an important intermediate in the path toward forming more complex biologically relevant molecules. Astronomical surveys of interstellar molecules, such as those available with the very sensitive ALMA telescope, require preliminary laboratory investigations of the microwave and submillimeter-wave spectra of molecular species including new isotopologs - to identify these in the interstellar media. Aims: To achieve the detection of the 13C isotopologs of glycolaldehyde in the interstellar medium, their rotational spectra in the millimeter and submillimeter-wave regions were studied. Methods: The spectra of 13CH2OHCHO and CH2OH13CHO were recorded in the 150-945 GHz spectral range in the laboratory using a solid-state submillimeter-wave spectrometer in Lille. The observed line frequencies were measured with an accuracy of 30 kHz up to 700 GHz and of 50 kHz above 700 GHz. We analyzed the spectra with a standard Watson Hamiltonian. Results: About 10 000 new lines were identified for each isotopolog. The spectroscopic parameters were determined for the ground- and the three lowest vibrational states up to 945 and 630 GHz. Previous microwave assignments of 13CH2OHCHO were not confirmed. Conclusions: The provided line-lists and sets of molecular parameters meet the needs for a first astrophysical search of 13C-glycolaldehydes. Full Tables 3 and 4 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/549/A96

  3. Beam maser measurements of HDO hyperfine structure

    NASA Astrophysics Data System (ADS)

    Fry, H. A.; Kukolich, S. G.

    1982-05-01

    The 431←432, 532←533, and 321←414 transition in HDO were measured in a beam maser spectrometer. Accurate values for rotational transiton frequencies, the deuterium quadrupole coupling tensor, and hydrogen spin-rotation tensor were obtained from the present data combined with previous results on other transitions. Resonance line widths of 2 kHz were obtained for most of the data. Measured quadrupole coupling tensor elements eqQ(D)gg and spin-rotation tensor elements C(X)gg in kHz are as follows: eqQ(D)aa = 276.45±0.88, eqQ(D)bb = -110.97±1.46, eqQ(D)cc = -165.77±1.10, C(D)aa = -1.33±0.20, C(D)bb = -4.38±0.36, C(D)cc = -2.99±0.24, C(H)aa = -58.42±0.47, C(H)bb = -5.46±0.83, C(H)cc = -24.11±0.55.

  4. High-resolution electron spin resonance spectroscopy of XeF* in solid argon. The hyperfine structure constants as a probe of relativistic effects in the chemical bonding properties of a heavy noble gas atom.

    PubMed

    Misochko, Eugenii Ya; Akimov, Alexander V; Goldschleger, Ilya U; Tyurin, Danil A; Laikov, Dimitri N

    2005-01-15

    Xenon fluoride radicals were generated by solid-state chemical reactions of mobile fluorine atoms with xenon atoms trapped in Ar matrix. Highly resolved electron spin resonance spectra of XeF* were obtained in the temperature range of 5-25 K and the anisotropic hyperfine parameters were determined for magnetic nuclei 19F, 129Xe, and 131Xe using naturally occurring and isotopically enriched xenon. Signs of parallel and perpendicular hyperfine components were established from analysis of temperature changes in the spectra and from numerical solutions of the spin Hamiltonian for two nonequivalent magnetic nuclei. Thus, the complete set of components of hyperfine- and g-factor tensors of XeF* were obtained: 19F (Aiso=435, Adip=1249 MHz) and 129Xe (Aiso=-1340, Adip=-485 MHz); g(parallel)=1.9822 and g(perpendicular)=2.0570. Comparison of the measured hyperfine parameters with those predicted by density-functional theory (DFT) calculations indicates, that relativistic DFT gives true electron spin distribution in the 2Sigma+ ground-state, whereas nonrelativistic theory underestimates dramatically the electron-nuclear contact Fermi interaction (Aiso) on the Xe atom. Analysis of the obtained magnetic-dipole interaction constants (Adip) shows that fluorine 2p and xenon 5p atomic orbitals make a major contribution to the spin density distribution in XeF*. Both relativistic and nonrelativistic calculations give close magnetic-dipole interaction constants, which are in agreement with the measured values. The other relativistic feature is considerable anisotropy of g-tensor, which results from spin-orbit interaction. The orbital contribution appears due to mixing of the ionic 2Pi states with the 2Sigma+ ground state, and the spin-orbit interaction plays a significant role in the chemical bonding of XeF*.

  5. Approaches to studies on neuronal/glial relationships by 13C-MRS analysis.

    PubMed

    Taylor, A; McLean, M; Morris, P; Bachelard, H

    1996-01-01

    The use of different 13C-labelled precursors alone or in combination ([1-13C]glucose, [2-13C]glucose, [1-13C]acetate, [2-13C]acetate and [1,2-13C2]acetate) to study neuronal/glial metabolic relationships by MRS is discussed. Glutamine and citrate resonances represent glial metabolism if a combination of [1-13C]glucose + [2-13C]acetate is used, but only for short time periods. A combination of [2-13C]glucose + [2-13C]acetate will label -COO- groups from glucose and -CH2 groups from acetate, respectively, which distinguish well in theory. However, this approach is severely limited by the long T1S of -COO- groups and low S/N. Contributions of the anaplerotic pathway can be assessed using [2-13C]glucose, but again can be limited by the long T1S of -COO- groups. Labelling of glycerol-3-phosphate (believed to be produced in glia) from [1-13C]glucose is difficult to see under normal conditions but has proved useful in, e.g., hypoxia. We believe the most promising approach is the use of [1-13C] glucose with [1,2-13C2]acetate, by analysis of the multiplets ('isotopomers') of the amino acid resonances.

  6. The First in Vivo Observation of 13C- 15N Coupling in Mammalian Brain

    NASA Astrophysics Data System (ADS)

    Kanamori, Keiko; Ross, Brian D.

    2001-12-01

    [5-13C,15N]Glutamine, with 1J(13C-15N) of 16 Hz, was observed in vivo in the brain of spontaneously breathing rats by 13C MRS at 4.7 T. The brain [5-13C]glutamine peak consisted of the doublet from [5-13C,15N]glutamine and the center [5-13C,14N]glutamine peak, resulting in an apparent triplet with a separation of 8 Hz. The time course of formation of brain [5-13C,15N]glutamine was monitored in vivo with a time resolution of 20-35 min. This [5-13C,15N]glutamine was formed by glial uptake of released neurotransmitter [5-13C]glutamate and its reaction with 15NH3 catalyzed by the glia-specific glutamine synthetase. The neurotransmitter glutamate C5 was selectively13C-enriched by intravenous [2,5-13C]glucose infusion to 13C-label whole-brain glutamate C5, followed by [12C]glucose infusion to chase 13C from the small and rapidly turning-over glial glutamate pool, leaving 13C mainly in the neurotransmitter [5-13C]glutamate pool, which is sequestered in vesicles until release. Hence, the observed [5-13C,15N]glutamine arises from a coupling between 13C of neuronal origin and 15N of glial origin. Measurement of the rate of brain [5-13C,15N]glutamine formation provides a novel noninvasive method of studying the kinetics of neurotransmitter uptake into glia in vivo, a process that is crucial for protecting the brain from glutamate excitotoxicity.

  7. Radiative transfer of HCN: interpreting observations of hyperfine anomalies

    NASA Astrophysics Data System (ADS)

    Mullins, A. M.; Loughnane, R. M.; Redman, M. P.; Wiles, B.; Guegan, N.; Barrett, J.; Keto, E. R.

    2016-07-01

    Molecules with hyperfine splitting of their rotational line spectra are useful probes of optical depth, via the relative line strengths of their hyperfine components. The hyperfine splitting is particularly advantageous in interpreting the physical conditions of the emitting gas because with a second rotational transition, both gas density and temperature can be derived. For HCN however, the relative strengths of the hyperfine lines are anomalous. They appear in ratios which can vary significantly from source to source, and are inconsistent with local thermodynamic equilibrium (LTE). This is the HCN hyperfine anomaly, and it prevents the use of simple LTE models of HCN emission to derive reliable optical depths. In this paper, we demonstrate how to model HCN hyperfine line emission, and derive accurate line ratios, spectral line shapes and optical depths. We show that by carrying out radiative transfer calculations over each hyperfine level individually, as opposed to summing them over each rotational level, the anomalous hyperfine emission emerges naturally. To do this requires not only accurate radiative rates between hyperfine states, but also accurate collisional rates. We investigate the effects of different sets of hyperfine collisional rates, derived via the proportional method and through direct recoupling calculations. Through an extensive parameter sweep over typical low-mass star-forming conditions, we show the HCN line ratios to be highly variable to optical depth. We also reproduce an observed effect whereby the red-blue asymmetry of the hyperfine lines (an infall signature) switches sense within a single rotational transition.

  8. Enzymatic 13C Labeling and Multidimensional NMR Analysis of Miltiradiene Synthesized by Bifunctional Diterpene Cyclase in Selaginella moellendorffii*

    PubMed Central

    Sugai, Yoshinori; Ueno, Yohei; Hayashi, Ken-ichiro; Oogami, Shingo; Toyomasu, Tomonobu; Matsumoto, Sadamu; Natsume, Masahiro; Nozaki, Hiroshi; Kawaide, Hiroshi

    2011-01-01

    Diterpenes show diverse chemical structures and various physiological roles. The diversity of diterpene is primarily established by diterpene cyclases that catalyze a cyclization reaction to form the carbon skeleton of cyclic diterpene. Diterpene cyclases are divided into two types, monofunctional and bifunctional cyclases. Bifunctional diterpene cyclases (BDTCs) are involved in hormone and defense compound biosyntheses in bryophytes and gymnosperms, respectively. The BDTCs catalyze the successive two-step type-B (protonation-initiated cyclization) and type-A (ionization-initiated cyclization) reactions of geranylgeranyl diphosphate (GGDP). We found that the genome of a lycophyte, Selaginella moellendorffii, contains six BDTC genes with the majority being uncharacterized. The cDNA from S. moellendorffii encoding a BDTC-like enzyme, miltiradiene synthase (SmMDS), was cloned. The recombinant SmMDS converted GGDP to a diterpene hydrocarbon product with a molecular mass of 272 Da. Mutation in the type-B active motif of SmMDS abolished the cyclase activity, whereas (+)-copalyl diphosphate, the reaction intermediate from the conversion of GGDP to the hydrocarbon product, rescued the cyclase activity of the mutant to form a diterpene hydrocarbon. Another mutant lacking type-A activity accumulated copalyl diphosphate as the reaction intermediate. When the diterpene hydrocarbon was enzymatically synthesized from [U-13C6]mevalonate, all carbons were labeled with 13C stable isotope (>99%). The fully 13C-labeled product was subjected to 13C-13C COSY NMR spectroscopic analyses. The direct carbon-carbon connectivities observed in the multidimensional NMR spectra demonstrated that the hydrocarbon product by SmMDS is miltiradiene, a putative biosynthetic precursor of tanshinone identified from the Chinese medicinal herb Salvia miltiorrhiza. Hence, SmMDS functions as a bifunctional miltiradiene synthase in S. moellendorffii. In this study, we demonstrate that one-dimensional and

  9. Microwave spectra for the three 13C1 isotopologues of propene and new rotational constants for propene and its 13C1 isotopologues

    NASA Astrophysics Data System (ADS)

    Craig, Norman C.; Groner, Peter; Conrad, Andrew R.; Gurusinghe, Ranil; Tubergen, Michael J.

    2016-10-01

    New measurements of microwave lines (A and E) of propene and its three 13C1 isotopologues have been made in the 10-22 GHz region with FT accuracy. The revised lines for propene along with many hundreds from the literature were fitted with the ERHAM program for internal rotors to give improved rotational constants. The new constants are A0 = 46280.2904(16), B0 = 9305.24260(30), and C0 = 8134.22685(28) MHz. Lines for the 3-13C1 species were observed in a pure sample; lines for the 1-13C1 and 2-13C1 species were observed in natural abundance. In fitting the limited sets of lines for the 13C1 species, many of the centrifugal distortion constants and most of the tunneling parameters were transferred from the fit of propene itself with 27 parameters. Improved rotational constants for the 13C1 species are reported.

  10. Sucrose octabenzoate: assignment of 13C and 1H resonances of the sucrose moiety and the 13C resonances of the carbonyl carbons. Use of 13C-n.m.r. spectroscopy for the study of selective deacylation.

    PubMed

    Colquhoun, I J; Haines, A H; Konowicz, P A; Jones, H F

    1990-09-19

    Assignment of the 1H and 13C signals arising from the carbohydrate portion of sucrose octabenzoate has been achieved using homonuclear shift correlation experiments (COSY) and one-bond 1H-13C heteronuclear shift correlation measurements, respectively. The 13C resonances of the carbonyl carbon atoms of the eight benzoyl groups are readily distinguished for solutions in benzene-d6-pyridine-d5 (1:1), and have been assigned by means of three-bond 1H-13C shift correlation studies coupled with measurement of the 13C-n.m.r. spectrum of a sucrose octabenzoate specifically labelled with 13C in some of the carbonyl groups. With this assignment, products of partial deacylation of the octabenzoate may readily be identified by treatment with excess of benzoyl-carbonyl-13C chloride followed by measurement of the 13C-n.m.r. spectrum of the labelled sucrose octabenzoate, so prepared, in the carbonyl region. PMID:2276151

  11. Solid-State NMR Study of Paramagnetic Bis(alaninato-κ(2)N,O)copper(II) and Bis(1-amino(cyclo)alkane-1-carboxylato-κ(2)N,O)copper(II) Complexes: Reflection of Stereoisomerism and Molecular Mobility in (13)C and (2)H Fast Magic Angle Spinning Spectra.

    PubMed

    Szalontai, Gábor; Csonka, Róbert; Speier, Gábor; Kaizer, József; Sabolović, Jasmina

    2015-05-18

    Solid-state stereochemistry and mobility of paramagnetic copper(II) complexes formed by aliphatic amino acids (l-alanine, d,l-alanine, 1-amino-2-methyl-alanine) and 1-amino(cyclo)alkane-1-carboxylic acids (alkane = propane, butane, pentane, hexane) as bidentate ligands has been studied by (13)C and (2)H solid-state fast magic angle spinning (MAS) NMR spectroscopy. We examined the prospective method to characterize solid-state paramagnetic compounds in a routine way. Both (13)C and (2)H MAS spectra can distinguish d,l and l,l diastereomers of natural and polydeuterated bis([Dn]alaninato)copper(II) (n = 0, 2, 8) complexes with axial and/or equatorial methyl positions (conformations) primarily due to different Fermi-contact (FC) contributions. The three-bond hyperfine couplings clearly show Karplus-like dependence on the torsional angles which turned out to be a useful assignment aid. Density functional theory calculations of the FC term and crystal structures were also used to aid the final assignments. The correlations obtained for bis(alaninato-κ(2)N,O)copper(II) complexes were successfully used to characterize other complexes. The usefulness of the (2)H MAS spectra of the deuterated complexes was underlined. Even the spectra of the easily exchangeable amine protons contained essential stereochemical information. In the case of a dimer structure of bis(1-aminohexane-1-carboxylato-κ(2)N,O)copper(II) both the (13)C and (2)H resolutions were good enough to confirm the presence of the cis and trans forms in the asymmetric unit. With regard to the internal solid-state motions in the crystal lattice, the obtained quadrupolar tensor parameters were similar for the d,l- and l,l-alaninato isomers and also for the cis-trans forms suggesting similar crystal packing effects, static amine deuterons involved in hydrogen bonding, and fast rotating methyl groups.

  12. A high resolution δ13C record in a modern Porites lobata coral: Insights into controls on skeletal δ13C

    NASA Astrophysics Data System (ADS)

    Allison, Nicola; Finch, Adrian A.; EIMF

    2012-05-01

    δ13C was determined at a high spatial resolution by secondary ion mass spectrometry (SIMS) across a 1 year section of a modern Porites lobata coral skeleton from Hawaii. Skeletal δ13C is dominated by large oscillations of 5-7‰ that typically cover skeletal distances equivalent to periods of ˜14-40 days. These variations do not reflect seawater temperature and it is unlikely that they reflect variations in the δ13C of local seawater. We observe no correlation between skeletal δ13C and the pH of the calcification fluid (estimated from previous measurements of skeletal δ11B). We conclude that either the proportion of skeletal carbon derived from metabolic CO2 is not reflected by estimated ECF pH (as the [CO2] in the overlying coral tissue varies) and/or the δ13C composition of the metabolic CO2 is highly variable. We also observe no correlation between skeletal δ13C and previous δ18O SIMS measurements. Variations in skeletal δ13C and δ18O do not have a common timing, providing no evidence that skeletal δ13C and δ18O vary in response to a single factor. This suggests that skeletal δ13C is principally driven by variations in the δ13C composition of metabolic CO2 rather than by the abundance of metabolic CO2, which would also affect skeletal δ18O. The δ13C composition of metabolic CO2 reflects the processes of photosynthesis, heterotrophic feeding and respiration in the overlying coral tissue. Corals catabolise stored lipid reserves to meet energetic demands when photosynthesis conditions are sub-optimal. Variations in the amounts and types of reserves utilised could induce changes in the δ13C composition of metabolic CO2 and the resultant skeleton which are temporally offset from skeletal δ18O records.

  13. Trans and surface membrane bound zervamicin IIB: 13C-MAOSS-NMR at high spinning speed.

    PubMed

    Raap, J; Hollander, J; Ovchinnikova, T V; Swischeva, N V; Skladnev, D; Kiihne, S

    2006-08-01

    Interactions between (15)N-labelled peptides or proteins and lipids can be investigated using membranes aligned on a thin polymer film, which is rolled into a cylinder and inserted into the MAS-NMR rotor. This can be spun at high speed, which is often useful at high field strengths. Unfortuantely, substrate films like commercially available polycarbonate or PEEK produce severe overlap with peptide and protein signals in (13)C-MAOSS NMR spectra. We show that a simple house hold foil support allows clear observation of the carbonyl, aromatic and C(alpha) signals of peptides and proteins as well as the ester carbonyl and choline signals of phosphocholine lipids. The utility of the new substrate is validated in applications to the membrane active peptide zervamicin IIB. The stability and macroscopic ordering of thin PC10 bilayers was compared with that of thicker POPC bilayers, both supported on the household foil. Sidebands in the (31)P-spectra showed a high degree of alignment of both the supported POPC and PC10 lipid molecules. Compared with POPC, the PC10 lipids are slightly more disordered, most likely due to the increased mobilities of the shorter lipid molecules. This mobility prevents PC10 from forming stable vesicles for MAS studies. The (13)C-peptide peaks were selectively detected in a (13)C-detected (1)H-spin diffusion experiment. Qualitative analysis of build-up curves obtained for different mixing times allowed the transmembrane peptide in PC10 to be distinguished from the surface bound topology in POPC. The (13)C-MAOSS results thus independently confirms previous findings from (15)N spectroscopy [Bechinger, B., Skladnev, D.A., Ogrel, A., Li, X., Rogozhkina, E.V., Ovchinnikova, T.V., O'Neil, J.D.J. and Raap, J. (2001) Biochemistry, 40, 9428-9437]. In summary, application of house hold foil opens the possibility of measuring high resolution (13)C-NMR spectra of peptides and proteins in well ordered membranes, which are required to determine the secondary

  14. 2s Hyperfine splitting in light hydrogen-like atoms: Theory and experiment

    SciTech Connect

    Karshenboim, S. G. Kolachevsky, N. N.; Ivanov, V. G.; Fischer, M.; Fendel, P.; Haensch, T. W.

    2006-03-15

    Since the combination D{sub 21} = 8f{sub HFS}(2s)-f{sub HFS}(1s) of hyperfine intervals in hydrogen and light two-body hydrogen-like atomic systems weakly depends on the nuclear structure, comparison between theory and experiment can be sensitive to high order QED corrections. New theoretical and experimental results are presented. Calculations have been performed for the hydrogen and deuterium atoms and for the helium-3 ion. Experiments on the 2s hyperfine splitting (responsible for the dominant contribution to the error in D{sub 21}) have been conducted for hydrogen and deuterium. The theory and experiment are in good agreement, and their accuracy is comparable to that attained in verifying the QED theory of the hyperfine splitting in leptonic atoms (muonium and positronium)

  15. Calculation of radiative corrections to hyperfine splitting in p1/2 states

    NASA Astrophysics Data System (ADS)

    Sapirstein, J.; Cheng, K. T.

    2006-10-01

    Techniques to calculate one-loop radiative corrections to hyperfine splitting including binding corrections to all orders have been developed in the last decade for s states of atoms and ions. In this paper these methods are extended to p1/2 states for three cases. In the first case, the point-Coulomb 2p1/2 hyperfine splitting is treated for the hydrogen isoelectonic sequence, and the lowest order result, (α)/(4π)EF , is shown to have large binding corrections at high Z . In the second case, neutral alkali-metal atoms are considered. In the third case, hyperfine splitting of the 2p1/2 state of lithiumlike bismuth is treated. In the latter two cases, correlation corrections are included and, in addition, the point is stressed that uncertainties associated with nuclear structure, which complicate comparison with experiment for s states, are considerably reduced because of the smaller overlap with the nucleus.

  16. Complete (1)H and (13)C signal assignment of prenol-10 with 3D NMR spectroscopy.

    PubMed

    Misiak, Maria; Koźmiński, Wiktor; Kwasiborska, Maria; Wójcik, Jacek; Ciepichal, Ewa; Swiezewska, Ewa

    2009-10-01

    The complete assignment of (1)H and (13)C chemical shifts of natural abundance prenol-10 is reported for the first time. It was achieved using 3D NMR experiments, which were based on random sampling of the evolution time space followed by multidimensional Fourier transform. This approach makes it possible to acquire 3D NMR spectra in a reasonable time and preserves high resolution in indirectly detected dimensions. It is shown that the interpretation of 3D COSY-HMBC and 3D TOCSY-HSQC spectra is crucial in the structural analysis of prenol-10.

  17. The hyperfine Paschen-Back Faraday effect

    NASA Astrophysics Data System (ADS)

    Zentile, Mark A.; Andrews, Rebecca; Weller, Lee; Knappe, Svenja; Adams, Charles S.; Hughes, Ifan G.

    2014-04-01

    We investigate experimentally and theoretically the Faraday effect in an atomic medium in the hyperfine Paschen-Back regime, where the Zeeman interaction is larger than the hyperfine splitting. We use a small permanent magnet and a micro-fabricated vapour cell, giving magnetic fields of the order of a tesla. We show that for low absorption and small rotation angles, the refractive index is well approximated by the Faraday rotation signal, giving a simple way to measure the atomic refractive index. Fitting to the atomic spectra, we achieve magnetic field sensitivity at the 10-4 level. Finally we note that the Faraday signal shows zero crossings which can be used as temperature insensitive error signals for laser frequency stabilization at large detuning. The theoretical sensitivity for 87Rb is found to be ˜40 kHz °C-1.

  18. Sparse (13)C labelling for solid-state NMR studies of P. pastoris expressed eukaryotic seven-transmembrane proteins.

    PubMed

    Liu, Jing; Liu, Chang; Fan, Ying; Munro, Rachel A; Ladizhansky, Vladimir; Brown, Leonid S; Wang, Shenlin

    2016-05-01

    We demonstrate a novel sparse (13)C labelling approach for methylotrophic yeast P. pastoris expression system, towards solid-state NMR studies of eukaryotic membrane proteins. The labelling scheme was achieved by co-utilizing natural abundance methanol and specifically (13)C labelled glycerol as carbon sources in the expression medium. This strategy improves the spectral resolution by 1.5 fold, displays site-specific labelling patterns, and has advantages for collecting long-range distance restraints for structure determination of large eukaryotic membrane proteins by solid-state NMR.

  19. Solid-state 13C NMR and molecular modeling studies of acetyl aleuritolic acid obtained from Croton cajucara Benth

    NASA Astrophysics Data System (ADS)

    da Silva San Gil, Rosane Aguiar; Albuquerque, Magaly Girão; de Alencastro, Ricardo Bicca; da Cunha Pinto, Angelo; do Espírito Santo Gomes, Fabiano; de Castro Dantas, Tereza Neuma; Maciel, Maria Aparecida Medeiros

    2008-08-01

    Solid-state 13C nuclear magnetic resonance ( 13C NMR) with magic-angle spinning (MAS) and with cross-polarization and magic-angle spinning (CP/MAS) spectra, and differential scanning calorimetry (DSC) techniques were used to obtain structural data from a sample of acetyl aleuritolic acid (AAA) extracted from the stem bark of Croton cajucara Benth. (Euphorbiaceae) and recrystallized from acetone. Since solid-state 13C NMR results suggested the presence of more than one molecule in the unitary cell for the AAA, DSC analysis and molecular modeling calculations were used to access this possibility. The absence of phase transition peaks in the DSC spectra and the dimeric models of AAA simulated using the semi-empirical PM3 method are in agreement with that proposal.

  20. Labeling strategies for 13C-detected aligned-sample solid-state NMR of proteins

    NASA Astrophysics Data System (ADS)

    Filipp, Fabian V.; Sinha, Neeraj; Jairam, Lena; Bradley, Joel; Opella, Stanley J.

    2009-12-01

    13C-detected solid-state NMR experiments have substantially higher sensitivity than the corresponding 15N-detected experiments on stationary, aligned samples of isotopically labeled proteins. Several methods for tailoring the isotopic labeling are described that result in spatially isolated 13C sites so that dipole-dipole couplings among the 13C are minimized, thus eliminating the need for homonuclear 13C- 13C decoupling in either indirect or direct dimensions of one- or multi-dimensional NMR experiments that employ 13C detection. The optimal percentage for random fractional 13C labeling is between 25% and 35%. Specifically labeled glycerol and glucose can be used at the carbon sources to tailor the isotopic labeling, and the choice depends on the resonances of interest for a particular study. For investigations of the protein backbone, growth of the bacteria on [2- 13C]-glucose-containing media was found to be most effective.

  1. Synthesis of 13C and 15N labeled 2,4-dinitroanisole.

    PubMed

    Jagadish, Bhumasamudram; Field, Jim A; Chorover, Jon; Sierra-Alvarez, Reyes; Abrell, Leif; Mash, Eugene A

    2014-05-30

    Syntheses of [(13)C6]-2,4-dinitroanisole (ring-(13)C6) from [(13)C6]-anisole (ring-(13)C6) and [(15)N2]-2,4-dinitroanisole from anisole using in situ generated acetyl nitrate and [(15)N]-acetyl nitrate, respectively, are described. Treatment of [(13)C6]-anisole (ring-(13)C6) with acetyl nitrate generated in 100% HNO3 gave [(13)C6]-2,4-dinitroanisole (ring-(13)C6) in 83% yield. Treatment of anisole with [(15)N]-acetyl nitrate generated in 10 N [(15)N]-HNO3 gave [(15)N2 ]-2,4-dinitroanisole in 44% yield after two cycles of nitration. Byproducts in the latter reaction included [(15)N]-2-nitroanisole and [(15)N]-4-nitroanisole.

  2. Model of decision system for 13C Isotope Separation column

    NASA Astrophysics Data System (ADS)

    Boca, M. L.

    2015-11-01

    This paper presents the model of a decisional system for 13C Isotope Separation column, which is used to detect mission critical situation. The start model was a model of one distributed control system of critical situations that may arise in the operation of the distillation column. The research work it is proposed a model of decision system which implement a temperature sensor inside of liquid nitrogen level in the condenser. The condenser is a part of column where take place the cryogenic process using nitrogen liquid. The work temperature is very low about -192oC, and because the temperature can grow or go down more than 2 degrees is a very critical location inside the column. In this way the column has a deeply monitor and supervised and it take a decision in a proper time when the temperature is grow up or getting down and became a critical situation. For monitor and supervised it was used MatLAB SimuLink. The model, the decision system gives a signal to one sensor when something is wrong in the condenser which is the most critical place of the isotopic column. In this way it creates an alarm that something is getting wrong in the isotopic column.

  3. Inelastic pion scattering by /sup 13/C at low energies

    SciTech Connect

    Mitchell, J.H.

    1987-03-01

    Angular distributions for inelastically scattered pions were obtained for several states in /sup 13/C at an incident energy of 65 MeV. The data include results from both ..pi../sup +/ and ..pi../sup -/ measurements. In addition, ..pi../sup -/ measurements were made at T/sub ..pi../ = 50 MeV at one angle to give a two point fixed-q excitation function. The data are compared to theory and the data of others. As might be expected, medium corrections are shown to be considerably more important at low energies than at resonance. This is true for inelastic transitions of multipolarity 0,2 and 3. Parameters derived from an analysis of elastic pion scattering and SCX data also provide an adequate description of the inelastic transitions. The charge asymmetry in the cross sections for the 9/2/sup +/ state that was seen at resonance persists at these energies. This result is consistent with an impulse approximation treatment of the spin-flip amplitude. This is true even though the incoming energy of the pions is far below the range where the validity of an impulse treatment is expected. 65 refs., 45 figs.

  4. New optical analyzer for 13C-breath test

    NASA Astrophysics Data System (ADS)

    Harde, Hermann; Dressler, Matthias; Helmrich, Günther; Wolff, Marcus; Groninga, Hinrich

    2008-04-01

    Medical breath tests are well established diagnostic tools, predominantly for gastroenterological inspections, but also for many other examinations. Since the composition and concentration of exhaled volatile gases reflect the physical condition of a patient, a breath analysis allows one to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter pylori in the stomach wall as an indication of a gastric ulcer. In this contribution we present a new optical analyzer that is based on photoacoustic spectroscopy and uses a DFB diode laser at 2.744 μm. The concentration ratio of the CO II isotopologues is determined by measuring the absorption on a 13CO II line in comparison to a 12CO II line. In the specially selected spectral range the lines have similar strengths, although the concentrations differ by a factor of 90. Therefore, the signals are well comparable. Due to an excellent signal-noise-ratio isotope variations of less than 1% can be resolved as required for the breath test.

  5. Two Categories of 13C/12C Ratios for Higher Plants 1

    PubMed Central

    Smith, Bruce N.; Epstein, Samuel

    1971-01-01

    13C/12C ratios have been determined for plant tissue from 104 species representing 60 families. Higher plants fall into two categories, those with low δPDBI13C values (—24 to —34‰) and those with high δ 13C values (—6 to —19‰). Algae have δ 13C values of —12 to —23‰. Photosynthetic fractionation leading to such values is discussed. PMID:16657626

  6. Relativistic Force Field: Parametrization of (13)C-(1)H Nuclear Spin-Spin Coupling Constants.

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-11-01

    Previously, we reported a reliable DU8 method for natural bond orbital (NBO)-aided parametric scaling of Fermi contacts to achieve fast and accurate prediction of proton-proton spin-spin coupling constants (SSCC) in (1)H NMR. As sophisticated NMR experiments for precise measurements of carbon-proton SSCCs are becoming more user-friendly and broadly utilized by the organic chemistry community to guide and inform the process of structure determination of complex organic compounds, we have now developed a fast and accurate method for computing (13)C-(1)H SSCCs. Fermi contacts computed with the DU8 basis set are scaled using selected NBO parameters in conjunction with empirical scaling coefficients. The method is optimized for inexpensive B3LYP/6-31G(d) geometries. The parametric scaling is based on a carefully selected training set of 274 ((3)J), 193 ((2)J), and 143 ((1)J) experimental (13)C-(1)H spin-spin coupling constants reported in the literature. The DU8 basis set, optimized for computing Fermi contacts, which by design had evolved from optimization of a collection of inexpensive 3-21G*, 4-21G, and 6-31G(d) bases, offers very short computational (wall) times even for relatively large organic molecules containing 15-20 carbon atoms. The most informative SSCCs for structure determination, i.e., (3)J, were computed with an accuracy of 0.41 Hz (rmsd). The new unified approach for computing (1)H-(1)H and (13)C-(1)H SSCCs is termed "DU8c".

  7. Relativistic Force Field: Parametrization of (13)C-(1)H Nuclear Spin-Spin Coupling Constants.

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-11-01

    Previously, we reported a reliable DU8 method for natural bond orbital (NBO)-aided parametric scaling of Fermi contacts to achieve fast and accurate prediction of proton-proton spin-spin coupling constants (SSCC) in (1)H NMR. As sophisticated NMR experiments for precise measurements of carbon-proton SSCCs are becoming more user-friendly and broadly utilized by the organic chemistry community to guide and inform the process of structure determination of complex organic compounds, we have now developed a fast and accurate method for computing (13)C-(1)H SSCCs. Fermi contacts computed with the DU8 basis set are scaled using selected NBO parameters in conjunction with empirical scaling coefficients. The method is optimized for inexpensive B3LYP/6-31G(d) geometries. The parametric scaling is based on a carefully selected training set of 274 ((3)J), 193 ((2)J), and 143 ((1)J) experimental (13)C-(1)H spin-spin coupling constants reported in the literature. The DU8 basis set, optimized for computing Fermi contacts, which by design had evolved from optimization of a collection of inexpensive 3-21G*, 4-21G, and 6-31G(d) bases, offers very short computational (wall) times even for relatively large organic molecules containing 15-20 carbon atoms. The most informative SSCCs for structure determination, i.e., (3)J, were computed with an accuracy of 0.41 Hz (rmsd). The new unified approach for computing (1)H-(1)H and (13)C-(1)H SSCCs is termed "DU8c". PMID:26414291

  8. Backbone and sidechain 1H, 15N and 13C assignments of the KSR1 CA1 domain

    PubMed Central

    Koveal, Dorothy; Pinheiro, Anderson S.; Peti, Wolfgang; Page, Rebecca

    2014-01-01

    The backbone and side chain resonance assignments of the murine KSR1 CA1 domain have been determined based on triple-resonance experiments using uniformly [13C, 15N]-labeled protein. This assignment is the first step towards the determination of the three-dimensional structure of the unique KSR1 CA1 domain. PMID:20737253

  9. 40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this...

  10. 40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this...

  11. 40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this...

  12. 40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this...

  13. 40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this...

  14. Stable isotope-enhanced two- and three-dimensional diffusion ordered 13C-NMR spectroscopy (SIE-DOSY 13C-NMR)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stable Isotope-Enhanced Diffusion Ordered (SIE-DOSY) 13C-NMR has been applied to 13C-enriched carbohydrates and has been used to determine diffusion coefficients for pentose and hexose monosaccharides, a disaccharide and a trisaccharide. These 2D spectra were obtained with as little as 8 min of acq...

  15. Solubilization and localization of weakly polar lipids in unsonicated egg phosphatidylcholine: A sup 13 C MAS NMR study

    SciTech Connect

    Hamilton, J.A. ); Fujito, D.T.; Hammer, C.F. )

    1991-03-19

    The weakly polar lipids cholesteryl ester, triacylglycerol, and diacylglycerol incorporate to a limited extent into the lamellar structure of small unilamellar vesicles. The localization of the carbonyl group(s) at the aqueous interface was detected by ({sup 13}C)carbonyl chemical shift changes relative to the neat unhydrated lipid. This study uses {sup 13}C NMR to investigate the interactions of thes lipids with unsonicated (multilamellar) phosphatidylcholine, a model system for cellular membranes and surfaces of emulsion particles with low curvature. Magic angle spinning reduced the broad lines of the unsonicated dispersions to narrow lines comparable to those from sonicated dispersions. ({sup 13}C)Carbonyl chemical shifts revealed incorporation of the three lipids into the lamellar structure of the unsonicated phospholipids and a partial hydration of the carbonyl groups similar to that observed in small vesicles. Other properties of interfacial weakly polar lipids in multilayers were similar to those in small unilamellar bilayers. There is thus a general tendency of weakly polar lipids to incorparate at least to a small extent into the lamellar structure of phospholipids and take on interfacial properties that are distinct from their bulk-phase properties. This pool of surface-located lipid is likely to be directly involved in enzymatyic transformations and protein-mediated transport. The {sup 13}C magic angle spinning NMR method may be generally useful for determining the orientation of molecules in model membranes.

  16. Determination of fructose metabolic pathways in normal and fructose-intolerant children: A sup 13 C NMR study using (U- sup 13 C)fructose

    SciTech Connect

    Gopher, A.; Lapidot, A. ); Vaisman, N. ); Mandel, H. )

    1990-07-01

    An inborn deficiency in the ability of aldolase B to split fructose 1-phosphate is found in humans with hereditary fructose intolerance (HFI). A stable isotope procedure to elucidate the mechanism of conversion of fructose to glucose in normal children and in HFI children has been developed. A constant infusion of D-(U-{sup 13}C)fructose was given nasogastrically to control and to HFI children. Hepatic fructose conversion to glucose was estimated by examination of {sup 13}C NMR spectra of plasma glucose. Significantly lower values ({approx}3-fold) for fructose conversion to glucose were obtained for the HFI patients as compared to the controls. A quantitative determination of the metabolic pathways of fructose conversion to glucose was derived from {sup 13}C NMR measurement of plasma ({sup 13}C)glucose isotopomer populations. The finding of isotopomer populations of three adjacent {sup 13}C atoms at glucose C-4 ({sup 13}C{sub 3}-{sup 13}C{sub 4}-{sup 13}C{sub 5}) suggests that there is a direct pathway from fructose, by-passing fructose-1-phosphate aldolase, to fructose 1,6-bisphosphate. The metabolism of fructose by fructose-1-phosphate aldolase activity accounts for only {approx}50% of the total amount of hepatic fructose conversion to glucose. In view of the marked decline by 67% in synthesis of glucose from fructose in HFI subjects found in this study, the extent of ({sup 13}C)glucose formation from a trace amount of (U-{sup 13}C)fructose infused into the patient can be used as a safe and noninvasive diagnostic test for inherent faulty fructose metabolism.

  17. Solid-state (13)C NMR reveals effects of temperature and hydration on elastin.

    PubMed Central

    Perry, Ashlee; Stypa, Michael P; Tenn, Brandon K; Kumashiro, Kristin K

    2002-01-01

    Elastin is the principal protein component of the elastic fiber in vertebrate tissue. The waters of hydration in the elastic fiber are believed to play a critical role in the structure and function of this largely hydrophobic, amorphous protein. (13)C CPMAS NMR spectra are acquired for elastin samples with different hydration levels. The spectral intensities in the aliphatic region undergo significant changes as 70% of the water in hydrated elastin is removed. In addition, dramatic differences in the CPMAS spectra of hydrated, lyophilized, and partially dehydrated elastin samples over a relatively small temperature range (-20 degrees C to 37 degrees C) are observed. Results from other experiments, including (13)C T(1) and (1)H T(1 rho) measurements, direct polarization with magic-angle spinning, and static CP of the hydrated and lyophilized elastin preparations, also support the model that there is significant mobility in fully hydrated elastin. Our results support models in which water plays an integral role in the structure and proper function of elastin in vertebrate tissue. PMID:11806948

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

    PubMed

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

    2014-12-01

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

  19. 2D-hyperfine sublevel correlation spectroscopy of tyrosyl radicals.

    PubMed

    Deligiannakis, Y; Ivancich, A; Rutherord, A W

    2002-04-01

    Hyperfine sublevel correlation (HYSCORE) spectroscopy has been used to study the tyrosyl radicals in Photosystem II and bovine liver catalase. The HYSCORE data allow a complete resolution of all the 1H hyperfine tensors of these radicals. The present work shows that the proper analysis of the HYSCORE data allows the complete assignment of the 1H-hyperfine tensors in tyrosine radicals and this offers an alternative experimental tool relative to ENDOR. PMID:11993467

  20. The Late Pleistocene history of surface water δ13C in the Sulu Sea: Possible relationship to Pacific Deepwater δ13C changes

    NASA Astrophysics Data System (ADS)

    Linsley, Braddock K.; Dunbar, Robert B.

    1994-04-01

    A reconstruction of late Pleistocene surface water carbon isotopic (δ13C) variability is presented from Ocean Drilling Program (ODP) site 769 in the Sulu Sea in the western tropical Pacific. The Sulu Sea is a shallowly silled back arc basin with a maximum sill depth of 420 m. Site 769 was drilled on a bathymetric high in 3643 m of water and has average late Pleistocene sedimentation rates of 8.5 cm/kyr. The oxygen isotope record (δ18O) of Globigerinoides ruber at site 769 shows a strong correlation with the SPECMAP stacked δ18O record, attesting to the continuity of sediment archive at the site. Surface δ13C displays consistent glacial-interglacial variability which averages ˜0.9‰ and has varied from 0.75 to 1.1‰ over the last 800 kyr. Comparison to surface water δ13C records in the South China Sea and western tropical Pacific suggests that the glacial-interglacial surface δ13C variability is regional in scale. Planktonic δ13C data from ODP site 677 in the eastern Pacific is also coherent with the site 769. Additionally, we have found that the site 769 surface δ13C record is coherent at periods of 100 and 41 kyr with deepwater δ13C records from the Pacific. The highest correlation occurs with the deep eastern Pacific, where benthic δ13C data from cores RC13-110 and ODP site 677 closely match the Sulu Sea surface water record. We evaluate several possible controls of surface water δ13C in the Sulu Sea that may explain the coherent timing with Pacific deepwater δ13C records. These include variations in terrestrial organic matter flux to the basin, the upwelling of subsurface water and productivity changes, and the influx of western Pacific intermediate water to the Sulu Sea. Our preferred explanation involves a region of upper intermediate water upwelling in the far western Pacific which has been shown to outgas CO2 from subsurface waters into surface waters. Upwelling also occurs in the area of Panama Basin site 677. These equatorial upwelling zones

  1. Determination of 13C/ 12C ratios with (d, p) nuclear reactions

    NASA Astrophysics Data System (ADS)

    Wang, Y. Q.; Zhang, J.; Tesmer, J. R.; Li, Y. H.; Greco, R.; Grim, G. P.; Obst, A. W.; Rundberg, R. S.; Wilhelmy, J. B.

    2010-06-01

    Stable isotope ratios such as 13C/ 12C play an important role in many applications including environment and energy research. Since many surface analysis techniques are plagued with unavoidable hydrocarbon contamination issues during analysis, it is highly desirable that 13C and 12C isotopes be measured simultaneously especially in specimens with a minute amount of 13C, in order to reliably determine 13C/ 12C ratios. In this paper, we report that deuterium induced proton particle reactions, 13C(d, p) 14C and 12C(d, p) 13C, provide a convenient and reliable approach for 13C/ 12C ratio determination. Optimizations on experimental considerations and potential interferences from other common light isotopes are discussed as well as results from the application of this technique to diagnose the performance of a target debris collection in an inertial confinement fusion (ICF) experiment.

  2. Sc3CH@C80: selective (13)C enrichment of the central carbon atom.

    PubMed

    Junghans, Katrin; Rosenkranz, Marco; Popov, Alexey A

    2016-05-01

    Sc3CH@C80 is synthesized and characterized by (1)H, (13)C, and (45)Sc NMR. A large negative chemical shift of the proton, -11.73 ppm in the Ih and -8.79 ppm in the D5h C80 cage isomers, is found. (13)C satellites in the (1)H NMR spectrum enabled indirect determination of the (13)C chemical shift for the central carbon at 173 ± 1 ppm. Intensity of the satellites allowed determination of the (13)C content for the central carbon atom. This unique possibility is applied to analyze the cluster/cage (13)C distribution in mechanistic studies employing either (13)CH4 or (13)C powder to enrich Sc3CH@C80 with (13)C. PMID:27109443

  3. Sc3CH@C80: selective 13C enrichment of the central carbon atom†

    PubMed Central

    Junghans, Katrin; Rosenkranz, Marco; Popov, Alexey A.

    2016-01-01

    Sc3CH@C80 is synthesized and characterized by 1H, 13C, and 45Sc NMR. A large negative chemical shift of the proton, −11.73 ppm in the Ih and −8.79 ppm in the D5h C80 cage isomers, is found. 13C satellites in the 1H NMR spectrum enabled indirect determination of the 13C chemical shift for the central carbon at 173 ± 1 ppm. Intensity of the satellites allowed determination of the 13C content for the central carbon atom. This unique possibility is applied to analyze the cluster/cage 13C distribution in mechanistic studies employing either 13CH4 or 13C powder to enrich Sc3CH@C80 with 13C. PMID:27109443

  4. Simple method for identification of skeletons of aporphine alkaloids from 13C NMR data using artificial neural networks.

    PubMed

    Rufino, Alessandra R; Brant, Antônio J C; Santos, João B O; Ferreira, Marcelo J P; Emerenciano, Vicente P

    2005-01-01

    This paper describes the use of artificial neural networks as a theoretical tool in the structural determination of alkaloids from (13)C NMR chemical shift data, aiming to identify skeletal types of those compounds. For that, 162 aporphine alkaloids belonging to 12 different skeletons were codified with their respective (13)C NMR chemical shifts. Each skeleton pertaining to aporphine alkaloid type was used as output, and the (13)C NMR chemical shifts were used as input data of the net. Analyzing the obtained results, one can then affirm the skeleton to which each one of these compounds belongs with high degree of confidence (over 97%). The relation between the correlation coefficient and the number of epochs and the architecture of net (3-layer MLP or 4-layer MLP) were analyzed, too. The analysis showed that the results predicted by the 3-layer MLP networks trained with a number of the epochs higher than 900 epochs are the best ones. The artificial neural nets were shown to be a simple and efficient tool to solve structural elucidation problems making use of (13)C NMR chemical shift data, even when a similarity between the searched skeletons occurs, offering fast and accurate results to identification of skeletons of organic compounds.

  5. Charge disproportionation with lattice distortion of α-(BEDT-TTF)2RbHg(SCN)4 observed by 13C-NMR

    NASA Astrophysics Data System (ADS)

    Noda, Kazuki; Ihara, Yoshihiko; Kawamoto, Atsushi

    2013-02-01

    To explore the connection between α-(BEDT-TTF)2I3 and α-(BEDT-TTF)2MHg(SCN)4 (M=K, Rb, Tl and NH4) and to resolve the difference between band picture and charge fluctuation of α-(BEDT-TTF)2MHg(SCN)4, we utilized 13C-NMR to examine α-(BEDT-TTF)2RbHg(SCN)4 under the conditions with a large hyperfine coupling constant at each site. The temperature dependence of site susceptibility showed the development of spin disproportionation as observed in α-(BEDT-TTF)2I3. We found that the linewidth of the A site only increased as temperature decreased from 200 to 100 K, a change associated with the development of lattice modulation. These findings indicate that density-wave modulation occurs during charge disproportionation instability.

  6. δ 13C evidence that high primary productivity delayed recovery from end-Permian mass extinction

    NASA Astrophysics Data System (ADS)

    Meyer, K. M.; Yu, M.; Jost, A. B.; Kelley, B. M.; Payne, J. L.

    2011-02-01

    Euxinia was widespread during and after the end-Permian mass extinction and is commonly cited as an explanation for delayed biotic recovery during Early Triassic time. This anoxic, sulfidic episode has been ascribed to both low- and high-productivity states in the marine water column, leaving the causes of euxinia and the mechanisms underlying delayed recovery poorly understood. Here we use isotopic analysis to examine the changing chemical structure of the water column through the recovery interval and thereby better constrain paleoproductivity. The δ 13C of limestones from 5 stratigraphic sections in south China displays a negative gradient of approximately 4‰ from shallow-to-deep water facies within the Lower Triassic. This intense gradient declines within Spathian and lowermost Middle Triassic strata, coincident with accelerated biotic recovery and carbon cycle stabilization. Model simulations show that high nutrient levels and a vigorous biological pump are required to sustain such a large gradient in δ 13C, indicating that Early Triassic ocean anoxia and delayed recovery of benthic animal ecosystems resulted from too much productivity rather than too little.

  7. Affordable uniform isotope labeling with (2)H, (13)C and (15)N in insect cells.

    PubMed

    Sitarska, Agnieszka; Skora, Lukasz; Klopp, Julia; Roest, Susan; Fernández, César; Shrestha, Binesh; Gossert, Alvar D

    2015-06-01

    For a wide range of proteins of high interest, the major obstacle for NMR studies is the lack of an affordable eukaryotic expression system for isotope labeling. Here, a simple and affordable protocol is presented to produce uniform labeled proteins in the most prevalent eukaryotic expression system for structural biology, namely Spodoptera frugiperda insect cells. Incorporation levels of 80% can be achieved for (15)N and (13)C with yields comparable to expression in full media. For (2)H,(15)N and (2)H,(13)C,(15)N labeling, incorporation is only slightly lower with 75 and 73%, respectively, and yields are typically twofold reduced. The media were optimized for isotope incorporation, reproducibility, simplicity and cost. High isotope incorporation levels for all labeling patterns are achieved by using labeled algal amino acid extracts and exploiting well-known biochemical pathways. The final formulation consists of just five commercially available components, at costs 12-fold lower than labeling media from vendors. The approach was applied to several cytosolic and secreted target proteins. PMID:25929326

  8. NMR study of Met-1 human Angiogenin: (1)H, (13)C, (15)N backbone and side-chain resonance assignment.

    PubMed

    Tsika, Aikaterini C; Chatzileontiadou, Demetra S M; Leonidas, Demetres D; Spyroulias, Georgios A

    2016-10-01

    Here, we report the high yield expression and preliminary structural analysis via solution hetero-nuclear NMR spectroscopy of the recombinant Met-1 human Angiogenin. The analysis reveals a well folded as well as, a monomeric polypeptide. Τhe sequence-specific assignment of its (1)H, (15)N and (13)C resonances at high percentage was obtained. Also, using TALOS+ its secondary structure elements were determined.

  9. 13C metabolic flux analysis at a genome-scale.

    PubMed

    Gopalakrishnan, Saratram; Maranas, Costas D

    2015-11-01

    Metabolic models used in 13C metabolic flux analysis generally include a limited number of reactions primarily from central metabolism. They typically omit degradation pathways, complete cofactor balances, and atom transition contributions for reactions outside central metabolism. This study addresses the impact on prediction fidelity of scaling-up mapping models to a genome-scale. The core mapping model employed in this study accounts for (75 reactions and 65 metabolites) primarily from central metabolism. The genome-scale metabolic mapping model (GSMM) (697 reaction and 595 metabolites) is constructed using as a basis the iAF1260 model upon eliminating reactions guaranteed not to carry flux based on growth and fermentation data for a minimal glucose growth medium. Labeling data for 17 amino acid fragments obtained from cells fed with glucose labeled at the second carbon was used to obtain fluxes and ranges. Metabolic fluxes and confidence intervals are estimated, for both core and genome-scale mapping models, by minimizing the sum of square of differences between predicted and experimentally measured labeling patterns using the EMU decomposition algorithm. Overall, we find that both topology and estimated values of the metabolic fluxes remain largely consistent between core and GSM model. Stepping up to a genome-scale mapping model leads to wider flux inference ranges for 20 key reactions present in the core model. The glycolysis flux range doubles due to the possibility of active gluconeogenesis, the TCA flux range expanded by 80% due to the availability of a bypass through arginine consistent with labeling data, and the transhydrogenase reaction flux was essentially unresolved due to the presence of as many as five routes for the inter-conversion of NADPH to NADH afforded by the genome-scale model. By globally accounting for ATP demands in the GSMM model the unused ATP decreased drastically with the lower bound matching the maintenance ATP requirement. A non

  10. Determination of de novo synthesized amino acids in cellular proteins revisited by 13C NMR spectroscopy.

    PubMed

    Flögel, U; Willker, W; Leibfritz, D

    1997-04-01

    13C nuclear magnetic resonance spectroscopy was used to determine the absolute amounts to de novo synthesized amino acids in both the perchloric acid extracts and the hydrolyzed protein fractions of F98 glioma cells incubated for 2 h with 5 mmol/l [U-13C]glucose. 13C NMR spectra of the hydrolyzed protein fraction revealed a marked incorporation of 13C-labelled alanine, aspartate and glutamate into the proteins of F98 cells within the incubation period. Additionally, small amounts of 13C-labelled glycine, proline and serine could unambiguously be identified in the protein fraction. Astonishingly, approximately equal amounts of 13C-labelled glutamate and aspartate were incorporated into the cellular proteins, although the cytosolic steady-state concentration of aspartate was below 13C NMR detectability. Hypertonic stress decreased the incorporation of 13C-labelled amino acids into the total protein, albeit their cytosolic concentrations were increased, which reflects an inhibition of protein synthesis under these conditions. On the other hand, hypotonic stress increased the amount of 13C-labelled proline incorporated into the cellular proteins even though the cytosolic concentration of 13C-labelled proline was largely decreased. Apparently, hypoosmotic conditions stimulate the synthesis of proteins or peptides with a high proline content. The results show that already after 2 h of incubation with [U-13C]glucose there is a pronounced flux of 13C label into the cellular proteins, which is usually disregarded if cytosolic fluids are examined only. This means that calculations of metabolic fluxes based on 13C NMR spectroscopic data obtained from perchloric acid extracts of cells or tissues and also from in vivo measurements consider only the labelled 'NMR visible' cytosolic metabolites, which may have to be corrected for fast label flowing off into other compartments.

  11. [Characteristics of foliar delta13C values of common shrub species in various microhabitats with different karst rocky desertification degrees].

    PubMed

    Du, Xue-Lian; Wang, Shi-Jie; Rong, Li

    2011-12-01

    By measuring the foliar delta13C values of 5 common shrub species (Rhamnus davurica, Pyracantha fortuneana, Rubus biflorus, Zanthoxylum planispinum, and Viburnum utile) growing in various microhabitats in Wangjiazhai catchment, a typical karst desertification area in Guizhou Province, this paper studied the spatial heterogeneity of plant water use at niche scale and the response of the heterogeneity to different karst rocky desertification degrees. The foliar delta13C values of the shrub species in the microhabitats followed the order of stony surface > stony gully > stony crevice > soil surface, and those of the majority of the species were more negative in the microhabitat soil surface than in the others. The foliar delta13C values decreased in the sequence of V. utile > R. biflorus > Z. planispinum > P. fortuneana > R. davurica, and the mean foliar delta13C value of the shrubs and that of typical species in various microhabitats all increased with increasing karst rocky desertification degree, differed significantly among different microhabitats. It was suggested that with the increasing degree of karst rocky desertification, the structure and functions of karst habitats were impaired, microhabitats differentiated gradually, and drought degree increased.

  12. Differentiation of histidine tautomeric states using 15N selectively filtered 13C solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Miao, Yimin; Cross, Timothy A.; Fu, Riqiang

    2014-08-01

    The histidine imidazole ring in proteins usually contains a mixture of three possible tautomeric states (two neutral - τ and π states and a charged state) at physiological pHs. Differentiating the tautomeric states is critical for understanding how the histidine residue participates in many structurally and functionally important proteins. In this work, one dimensional 15N selectively filtered 13C solid-state NMR spectroscopy is proposed to differentiate histidine tautomeric states and to identify all 13C resonances of the individual imidazole rings in a mixture of tautomeric states. When 15N selective 180° pulses are applied to the protonated or non-protonated nitrogen region, the 13C sites that are bonded to the non-protonated or protonated nitrogen sites can be identified, respectively. A sample of 13C, 15N labeled histidine powder lyophilized from a solution at pH 6.3 has been used to illustrate the usefulness of this scheme by uniquely assigning resonances of the neutral τ and charged states from the mixture.

  13. Nagaoka’s atomic model and hyperfine interactions

    PubMed Central

    INAMURA, Takashi T.

    2016-01-01

    The prevailing view of Nagaoka’s “Saturnian” atom is so misleading that today many people have an erroneous picture of Nagaoka’s vision. They believe it to be a system involving a ‘giant core’ with electrons circulating just outside. Actually, though, in view of the Coulomb potential related to the atomic nucleus, Nagaoka’s model is exactly the same as Rutherford’s. This is true of the Bohr atom, too. To give proper credit, Nagaoka should be remembered together with Rutherford and Bohr in the history of the atomic model. It is also pointed out that Nagaoka was a pioneer of understanding hyperfine interactions in order to study nuclear structure. PMID:27063182

  14. Metabolic pathways for ketone body production. /sup 13/C NMR spectroscopy of rat liver in vivo using /sup 13/C-multilabeled fatty acids

    SciTech Connect

    Pahl-Wostl, C.; Seelig, J.

    1986-11-04

    The hormonal regulation of ketogenesis in the liver of living rat has been studied noninvasively with /sup 13/C nuclear magnetic resonance. The spatial selection for the liver was better than 90%, with extrahepatic adipose tissue contribution only a very small amount of signal. The metabolic activities of the liver were investigated by infusion of /sup 13/C-labeled butyrate in the jugular vein of the anesthetized rat. The rate of butyrate infusion was chosen to be close to the maximum oxidative capacity of the rat liver, and the /sup 13/C signal intensities were enhanced by using doubly labeled (1,3-/sup 13/C)butyrate as a substrate. Different /sup 13/C NMR spectra and hence different metabolites were observed depending on the hormonal state of the animal. The /sup 13/C NMR studies demonstrate that even when rate of acetyl-CoA production are high, the disposal of this compound is not identical in fasted and diabetic animals. This supports previous suggestions that the redox state of the mitochondrion represents the most important factor in regulation. For a given metabolic state of the animal, different signal intensities were obtained depending on whether butyrate was labeled at C-1, C-3, or C-1,3. From the ratios of incorporation of /sup 13/C label into the carbons of 3-hydroxybutyrate, it could be estimated that a large fraction of butyrate evaded ..beta..-oxidation to acetyl-CoA but was converted directly to acetoacetyl-CoA. /sup 13/C-labeled glucose could be detected in vivo in the liver of diabetic rats.

  15. Hyperfine transitions in ultracold hydrogen-antihydrogen collisions

    SciTech Connect

    Voronin, A. Yu.; Froelich, P.

    2009-07-15

    We consider the hyperfine transitions in ultracold collisions of hydrogen (H) and antihydrogen (H) atoms. The cross sections for transitions between various spin states are calculated. We show that hyperfine transitions in H-H collisions are basically driven by the strong force between proton and antiproton.

  16. Synthesis of isotopically labeled R- or S-[.sup.13C, .sup.2H] glycerols

    DOEpatents

    Martinez, Rodolfo A.; Unkefer, Clifford J.; Alvarez, Marc A.

    2008-01-22

    The present invention is directed to asymmetric chiral labeled glycerols including at least one chiral atom, from one to two .sup.13C atoms and from zero to four deuterium atoms bonded directly to a carbon atom, e.g., (2S) [1,2-.sup.13C.sub.2]glycerol and (2R) [1,2-.sup.13C.sub.2]glycerol, and to the use of such chiral glycerols in the preparation of labeled amino acids.

  17. Proceedings of the 2nd KUR symposium on hyperfine interactions

    NASA Astrophysics Data System (ADS)

    Mekata, M.; Minamisono, T.; Kawase, Y.

    1991-10-01

    Hyperfine interactions between a nuclear spin and an electronic spin discovered from hyperfine splitting in atomic optical spectra have been utilized not only for the determination of nuclear parameters in nuclear physics but also for novel experimental techniques in many fields such as solid state physics, chemistry, biology, mineralogy, and for diagnostic methods in medical science. Experimental techniques based on hyperfine interactions yield information about microscopic states of matter so that they are important in material science. Probes for material research using hyperfine interactions have been nuclei in the ground state and radioactive isotopes prepared with nuclear reactors or particle accelerators. But the use of muons generated from accelerators is growing. Such wide spread application of hyperfine interaction techniques gives rise to some difficulty in collaboration among various research fields. This report summarizes the KUR symposium in the hope that this information will help to alleviate the problem.

  18. Open-Source Automated Parahydrogen Hyperpolarizer for Molecular Imaging Using (13)C Metabolic Contrast Agents.

    PubMed

    Coffey, Aaron M; Shchepin, Roman V; Truong, Milton L; Wilkens, Ken; Pham, Wellington; Chekmenev, Eduard Y

    2016-08-16

    An open-source hyperpolarizer producing (13)C hyperpolarized contrast agents using parahydrogen induced polarization (PHIP) for biomedical and other applications is presented. This PHIP hyperpolarizer utilizes an Arduino microcontroller in conjunction with a readily modified graphical user interface written in the open-source processing software environment to completely control the PHIP hyperpolarization process including remotely triggering an NMR spectrometer for efficient production of payloads of hyperpolarized contrast agent and in situ quality assurance of the produced hyperpolarization. Key advantages of this hyperpolarizer include: (i) use of open-source software and hardware seamlessly allowing for replication and further improvement as well as readily customizable integration with other NMR spectrometers or MRI scanners (i.e., this is a multiplatform design), (ii) relatively low cost and robustness, and (iii) in situ detection capability and complete automation. The device performance is demonstrated by production of a dose (∼2-3 mL) of hyperpolarized (13)C-succinate with %P13C ∼ 28% and 30 mM concentration and (13)C-phospholactate at %P13C ∼ 15% and 25 mM concentration in aqueous medium. These contrast agents are used for ultrafast molecular imaging and spectroscopy at 4.7 and 0.0475 T. In particular, the conversion of hyperpolarized (13)C-phospholactate to (13)C-lactate in vivo is used here to demonstrate the feasibility of ultrafast multislice (13)C MRI after tail vein injection of hyperpolarized (13)C-phospholactate in mice. PMID:27478927

  19. Measuring (13)C-(2)D dipolar couplings with a universal REDOR dephasing curve

    PubMed

    Gullion

    2000-09-01

    A (13)C-observe REDOR experiment is described which allows (13)C-(2)D dipolar couplings to be obtained by a universal dipolar dephasing curve. Previous (13)C-observe REDOR experiments on (13)C-(2)D spin pairs generally relied on numerical simulations to obtain the dipolar coupling. The REDOR experiment described in this article is based on a deuterium composite pulse, and the data analysis eliminates the need for numerical simulations and is the same as the traditional REDOR analysis performed on pairs of spin-12 nuclei. Copyright 2000 Academic Press. PMID:10968975

  20. In vivo hyperpolarized 13C MR spectroscopic imaging with 1H decoupling

    NASA Astrophysics Data System (ADS)

    Chen, Albert P.; Tropp, James; Hurd, Ralph E.; Van Criekinge, Mark; Carvajal, Lucas G.; Xu, Duan; Kurhanewicz, John; Vigneron, Daniel B.

    2009-03-01

    Application of 13C MRS in vivo on whole body MR system has been limited due to the low static field (and consequent low signal to noise ratio—SNR) of these scanners; thus there have been few reports of 1H decoupled 13C MRS in vivo using a clinical MR platform. The recent development of techniques to retain highly polarized spins in solution following DNP in a solid matrix has provided a mechanism to use endogenous pre-polarized 13C labeled substrates to study real time cellular metabolism in vivo with high SNR. In a recent in vivo hyperpolarized metabolic imaging study using 13C pyruvate, it has been demonstrated that the line shape (signal decay) of the resonances observed are greatly affected by JCH coupling in addition to inhomogeneous broadening. This study demonstrates the feasibility of improving hyperpolarized 13C metabolic imaging in vivo by incorporating 1H decoupling on a clinical whole body 3 T MR scanner. No reduction of T1 of a pre-polarized 13C substrate ([1- 13C] lactate) in solution was observed when 1H decoupling was applied with WALTZ16 sequence. Narrower linewidth for the [1- 13C] lactate resonance was observed in hyperpolarized 13C MRSI data in vivo with 1H decoupling.

  1. Near-silence of isothiocyanate carbon in (13)C NMR spectra: a case study of allyl isothiocyanate.

    PubMed

    Glaser, Rainer; Hillebrand, Roman; Wycoff, Wei; Camasta, Cory; Gates, Kent S

    2015-05-01

    (1)H and (13)C NMR spectra of allyl isothiocyanate (AITC) were measured, and the exchange dynamics were studied to explain the near-silence of the ITC carbon in (13)C NMR spectra. The dihedral angles α = ∠(C1-C2-C3-N4) and β = ∠(C2-C3-N4-C5) describe the conformational dynamics (conformation change), and the bond angles γ = ∠(C3-N4-C5) and ε = ∠(N4-C5-S6) dominate the molecular dynamics (conformer flexibility). The conformation space of AITC contains three minima, Cs-M1 and enantiomers M2 and M2'; the exchange between conformers is very fast, and conformational effects on (13)C chemical shifts are small (νM1 - νM2 < 3 ppm). Isotropic chemical shifts, ICS(γ), were determined for sp, sp(x), and sp(2) N-hybridization, and the γ dependencies of δ(N4) and δ(C5) are very large (10-33 ppm). Atom-centered density matrix propagation trajectories show that every conformer can access a large region of the potential energy surface AITC(γ,ε,...) with 120° < γ < 180° and 155° < ε < 180°. Because the extreme broadening of the (13)C NMR signal of the ITC carbon is caused by the structural flexibility of every conformer of AITC, the analysis provides a general explanation for the near-silence of the ITC carbon in (13)C NMR spectra of organic isothiocyanates.

  2. /sup 13/C NMR studies of the molecular flexibility of antidepressants

    SciTech Connect

    Munro, S.L.; Andrews, P.R.; Craik, D.J.; Gale, D.J.

    1986-02-01

    The solution dynamics of a series of clinically potent antidepressants have been investigated by measuring /sup 13/C NMR relaxation parameters. Correlation times and internal motional rates were calculated from spin-lattice relaxation times and nuclear Overhauser effects for the protonated carbons in mianserin, imipramine-like antidepressants, and amitriptyline-like antidepressants. These data were interpreted in terms of overall molecular tumbling, internal rotations, and inherent flexibility of these structures. Of particular interest was the conformational variability of the tricyclic nucleus of the tricyclic antidepressants, where the data indicated a fivefold difference in mobility of the dimethylene bridge of imipramine-like antidepressants relative to amitriptyline-like compounds. The implications of such a difference in internal motions is discussed in relation to previous NMR studies and to the reported differences in pharmacological activity of these antidepressants.

  3. Simulation of 13C nuclear magnetic resonance spectra for isodon terpenoid

    NASA Astrophysics Data System (ADS)

    Yang, Guochen; Tong, Jianbo; Liu, Shuling

    2008-11-01

    A quantitative structure spectroscopy relationship (QSSR) model of 13C nuclear magnetic resonance (NMR) of 7000 carbon atoms in 350 isodon terpenoid compounds has been developed using atomic electronegativity distance vector (AEDV) and atomic hybridization state index (AHSI). The prediction correlation coefficient ( R) value of the QSSR model based on multiple linear regression analysis was 0.9542. The stability and prediction capacity of the QSSR model have been tested using the leave-one-out cross-validation and test sets methodology. The correlation coefficients R obtained were 0.9540 and 0.9556, respectively, which showed that the predictive potential of the proposed models has good modeling stability and prediction ability.

  4. Total assignment of 1H and 13C NMR data for the sesquiterpene lactone 15-deoxygoyazensolide.

    PubMed

    Heleno, Vladimir Constantino Gomes; Crotti, Antônio Eduardo Miller; Constantino, Mauricio Gomes; Lopes, Norberto Peporine; Lopes, João Luis Callegari

    2004-03-01

    We describe a complete analysis of the 1H and 13C spectra of the anti-inflamatory, schistossomicidal and trypanosomicidal sesquiterpene lactone 15-deoxygoyazensolide. This lactone, with a structure similar to other important ones, was studied by NMR techniques such as COSY, HMQC, HMBC, Jres and NOE experiments. The comparison of the data with some computational results led to an unequivocal assignment of all hydrogen and carbon chemical shifts, even eliminating some previous ambiguities. We were able to determine all hydrogen coupling constants (J) and signal multiplicities and to confirm the stereochemistry. A new method for the determination of the relative position of the lactonization and the position of the ester group on a medium-sized ring by NMR was developed.

  5. The effect of sample hydration on 13C CPMAS NMR spectra of fulvic acids

    USGS Publications Warehouse

    Hatcher, P.G.; Wilson, M.A.

    1991-01-01

    Three fulvic acids, two of which have been well studied by a number of other groups (Armadale and Suwannee river fulvic acids) have been examined by high resolution solid-state 13C-NMR techniques to delineate the effect of absorbed water. Two main effects of absorbed water were observed: (1) changes in spin lattice relaxation times in the rotating frame and cross polarization times and (2) total loss of signal so that some fulvic acid is effectively in solution. These results suggest that discrepancies in the literature concerning observed relative signal intensities from different structural groups are due to absorbed water and emphasize the necessity for proper precautionary drying before spectroscopic analysis. ?? 1991.

  6. Solid state 13C NMR investigation of impact of annealing in lyophilized glasses.

    PubMed

    Luthra, Suman A; Pikal, Michael J; Utz, Marcel

    2008-10-01

    The purpose of this study was to investigate the impact of annealing on molecular mobility in lyophilized glasses, composed of a saccharide excipient and a small concentration of aspartame as a model "drug." Changes in molecular dynamics during annealing were monitored through carbon ((13)C) T(1) and T(1 rho) nuclear magnetic resonance relaxation times of the aspartame and the saccharides. Two different saccharides were studied, sucrose and trehalose. The local mobility of the aspartame guest was found to correlate closely with the overall structural relaxation monitored through calorimetric methods in the aspartame: sucrose formulation. In general terms, annealing leads to longer NMR relaxation times, indicating a slowing of the local dynamics. By contrast, annealing had only a minimal effect on the NMR relaxation times in aspartame: trehalose. Specificity of solid state NMR in detecting molecular mobility in guest and host molecules showed that sucrose provided a homogenous matrix for the guest drug as compared to the trehalose.

  7. The 3 A Band System in the Spectrum of the 13C 16O Molecule

    NASA Astrophysics Data System (ADS)

    Hakalla, R.; Kępa, R.; Rytel, M.; Zachwieja, M.

    1999-10-01

    In the emission spectrum of the carbon monoxide 13C16O isotopic molecule three bands comprising about 1820 lines of the 3A band system (c3Π-a3Π) were recorded and analyzed. The 0-0 and 0-1 bands of this system were photographed for the first time and the 0-2 band was rephotographed by using methods of conventional high-resolution spectroscopy. The result of the rotational band analysis includes expanding of the spectrum interpretation up to J = 25 as well as the identification of four previously unobserved branches P13, R13, P31, and R31. Because of strong perturbations in the c3Π (v = 0) state, the calculation of the rovibronic structure constants was performed only for the lower a3Π state. By using a calculation based on a nonlinear least-squares method, an effective Hamiltonian of Brown [J. M. Brown, E. A. Colbourn, J. K. G. Watson, and F. D. Wayne, J. Mol. Spectrosc. 74, 294-318 (1979)] and a separative procedure proposed by Curl-Dane-Watson [R. F. Curl and C. B. Dane, J. Mol. Spectrosc. 128, 406-412 (1988); J. K. G. Watson, J. Mol. Spectrosc. 138, 302-308 (1989)], it was possible to derive the rotational structure constants for the v = 0, 1, and 2 levels for the a3Π state in the 13C16O isotopic molecule. Term values for the c3Π (v = 0) level and the equilibrium molecular constants for the a3Π state also are reported.

  8. The 3A Band System in the Spectrum of the (13)C(16)O Molecule.

    PubMed

    Hakalla; Kepa; Rytel; Zachwieja

    1999-10-01

    In the emission spectrum of the carbon monoxide (13)C(16)O isotopic molecule three bands comprising about 1820 lines of the 3A band system (c(3)Pi-a(3)Pi) were recorded and analyzed. The 0-0 and 0-1 bands of this system were photographed for the first time and the 0-2 band was rephotographed by using methods of conventional high-resolution spectroscopy. The result of the rotational band analysis includes expanding of the spectrum interpretation up to J = 25 as well as the identification of four previously unobserved branches P(13), R(13), P(31), and R(31). Because of strong perturbations in the c(3)Pi (v = 0) state, the calculation of the rovibronic structure constants was performed only for the lower a(3)Pi state. By using a calculation based on a nonlinear least-squares method, an effective Hamiltonian of Brown [J. M. Brown, E. A. Colbourn, J. K. G. Watson, and F. D. Wayne, J. Mol. Spectrosc. 74, 294-318 (1979)] and a separative procedure proposed by Curl-Dane-Watson [R. F. Curl and C. B. Dane, J. Mol. Spectrosc. 128, 406-412 (1988); J. K. G. Watson, J. Mol. Spectrosc. 138, 302-308 (1989)], it was possible to derive the rotational structure constants for the v = 0, 1, and 2 levels for the a(3)Pi state in the (13)C(16)O isotopic molecule. Term values for the c(3)Pi (v = 0) level and the equilibrium molecular constants for the a(3)Pi state also are reported. Copyright 1999 Academic Press.

  9. Ab Initio Calculations of Possible γ-Gauche Effects in the 13C-NMR for Methine and Carbonyl Carbons in Precise Polyethylene Acrylic Acid Copolymers

    SciTech Connect

    Alam, Todd

    2013-07-29

    The impacts of local polymer chain conformations on the methine and carbonyl 13C-NMR chemical shifts for polyethylene acrylic acid p(E-AA) copolymers were predicted using ab initio methods. Using small molecular cluster models, the magnitude and sign of the γ-gauche torsional angle effect, along with the impact of local tetrahedral structure distortions near the carbonyl group, on the 13C-NMR chemical shifts were determined. These 13C-NMR chemical shift variations were compared to the experimental trends observed for precise p(E-AA) copolymers as a function acid group spacing and degree of zinc-neutralization in the corresponding p(E-AA) ionomers. These ab initio calculations address the future ability of 13C-NMR chemical shift variations to provide information about the local chain conformations in p(E-AA) copolymer materials.

  10. New study of the astrophysical reaction 13C(a,n)16O via the 13C(7Li,t)17O transfer reaction

    NASA Astrophysics Data System (ADS)

    Pellegriti, Maria Grazia; Hammache, F.; Roussel, P.; Audouin, L.; Beaumel, D.; Fortier, S.; Gaudefroy, L.; Kiener, J.; Lefebvre-Schujl, A.; Stanoiu, M.; Tatischeff, V.; Vilmay, M.

    PoS(NIC-IX)161 , , [1] , L. Gaudefroy[2] , J. Kiener[3] , A. Lefebvre-Schuhl[3] , M. Stanoiu[4] , V. The cross section of the 13 C(α,n)16 O reaction is a key ingredient for the comprehension of the s-process (slow neutron captures) in stars. This reaction is considered as the main neutron source for the s-process in low-mass Asymptotic Giant Branch (AGB) stars (1-3 solar mass) [1, 2, 3]. At the α-13 C energies of astrophysical interest (Ecm around 190 keV, corresponding to a tem- perature of 108 K) the contribution of the 17 O α-decay subthreshold resonance at 6.356 MeV to the 13 C(α,n)16 O cross section should be taken into account. The effect of this resonance is controversial after the different analyses of the Kubono et al. measurement [4] of the 6.356 MeV α-spectroscopic factor (Sα ) via the transfer reaction 13 C(6 Li,d)17 O . In order to further investigate the contribution of the 6.356 MeV resonance to the 13 C(α,n)16 O cross section, we performed a new measurement of its Sα factor via a different α-transfer reac- tion, namely the 13 C(7 Li,t)17 O reaction. The experiment was performed at the Orsay Tandem by using a 7 Li beam of 28 and 34 MeV on a 13C target. The angular distribution for the transfer dif- ferential cross section was measured by detecting the tritons at the focal plane of the SPLITPOLE spectrometer. The analysis procedure used in order to extract the yield of the 6.356 MeV level will be described. Preliminary results of the angular distribution will be shown.

  11. A Large Metabolic Carbon Ccontribution to the δ13C Record in Marine Aragonitic Bivalve Shells

    NASA Astrophysics Data System (ADS)

    Gillikin, D. P.; Lorrain, A.; Dehairs, F.

    2006-12-01

    The stable carbon isotopic signature archived in bivalve shells was originally thought to record the δ13C of seawater dissolved inorganic carbon (δ13C-DIC). However, more recent studies have shown that the incorporation of isotopically light metabolic carbon (M) significantly affects the δ13C signal recorded in biogenic carbonates. To assess the M contribution to Mercenaria mercenaria shells collected in North Carolina, USA, we sampled seawater δ13C-DIC, tissue, hemolymph and shell δ13C. We found up to a 4‰ decrease through ontogeny in shell δ13C in a 23 year old individual. There was no correlation between shell height or age and tissue δ13C. Thus, the ontogenic decrease observed in the shell δ13C could not be attributed to changes in food sources as the animal ages leading to more negative metabolic CO2, since this would require a negative relationship between tissue δ13C and shell height. Hemolymph δ13C, on the other hand, did exhibit a negative relationship with height, but the δ13C values were more positive than expected, indicating that hemolymph may not be a good proxy of extrapallial fluid δ13C. Nevertheless, the hemolymph data indicate that respired CO2 does influence the δ13C of internal fluids and that the amount of respired CO2 is related to the age of the bivalve. The percent metabolic C incorporated into the shell (%M) was significantly higher (up to 37%) than has been found in other bivalve shells, which usually contain less than 10 %M. Attempts to use shell biometrics to predict %M could not explain more than ~60% of the observed variability. Moreover, there were large differences in the %M between different sites. Thus, the metabolic effect on shell δ13C cannot easily be accounted for to allow reliable δ13C-DIC reconstructions. However, there does seem to be a common effect of size, as all sites had indistinguishable slopes between the %M and shell height (+0.19% per mm of shell height).

  12. Preliminary studies of a canine 13C-aminopyrine demethylation blood test.

    PubMed Central

    Moeller, E M; Steiner, J M; Williams, D A; Klein, P D

    2001-01-01

    The objectives of this study were to determine whether a 13C-aminopyrine demethylation blood test is technically feasible in clinically healthy dogs, whether oral administration of 13C-aminopyrine causes a detectable increase in percent dose/min (PCD) of 13C administered as 13C-aminopyrine and recovered in gas extracted from blood, and whether gas extraction efficiency has an impact on PCD. A dose of 2 mg/kg body weight of 13C-aminopyrine dissolved in deionized water was administered orally to 6 clinically healthy dogs. Blood samples were taken from each dog 0, 30, 60, and 120 min after administration of the 13C-aminopyrine. Carbon dioxide was extracted from blood samples by addition of acid and analyzed by fractional mass spectrometry. None of the 6 dogs showed any side effects after 13C-aminopyrine administration. All 6 dogs showed a measurable increase of the PCD in gas samples extracted from blood samples at 30 min, 60 min, and 120 min after 13C-aminopyrine administration. Coefficients of variation between the triplicate samples were statistically significantly higher for the %CO2, a measure of extraction efficiency, than for PCD values (P < 0.0001). The 13C-aminopyrine demethylation blood test described here is technically feasible. Oral administration of 13C-aminopyrine did not lead to gross side effects in the 6 dogs. Clinically healthy dogs show a measurable increase of PCD in gas extracted from blood samples after oral administration of 13C-aminopyrine. Efficiency of CO2 extraction from blood samples does not have an impact on PCD determined from these blood samples. This test may prove useful to evaluate hepatic function in dogs. PMID:11227194

  13. Stratigraphic significance and global distribution of the δ13C Suess effect during the Anthropocene

    NASA Astrophysics Data System (ADS)

    Paul, André; Mulitza, Stefan

    2015-04-01

    The Anthropocene is the proposed term for the present geological epoch (from the time of the Industrial Revolution onwards), during which human influence significantly impacts the environment. We argue that the burning of isotopically light fossil fuel that causes the so-called 'δ13C Suess effect' leaves such a strong imprint on marine sediments that it may serve to define the onset of this geological epoch, at least since the so-called 'Great Acceleration', i.e., the second half of the 20th century. Sediment data with high temporal resolution from the recent past indeed reveal a trend that corresponds to a negative carbon isotope excursion of the order of one permil, comparable to carbon isotope excursions in the deep past that define stratigraphic boundaries such as the Paleocene-Eocene Thermal Maximum (PETM). A global carbon cycle model based on the MIT general circulation model (MITgcm), fitted with carbon isotopes 13C and 14C and forced with observed changes in the atmospheric carbon dioxide partial pressure and carbon isotopic ratio 13C/12C, allows to investigate the temporal evolution and three-dimensional structure of the anomaly. We show the carbon isotopic ratios of fossil shells of benthic foraminifera (δ13Cc) from two ocean sediment cores GeoB6008 (31° N) und GeoB9501 (17° N) over the Anthropocene (mainly the 20th century). The decrease in δ13Cc at 31° N is about 0.8 permil; off Mauretania (at 17° N in the shadow zone of the subtropical gyre) it still amounts to about 0.4 permil. While the magnitude of the change in the global carbon cycle model is similar, the difference is smaller: The decrease in the model is around 0.9 permil near the location of the northern core and around 0.8 permil near the location of the southern core. The smaller difference of only about 0.1 permil points to a bias in the simulated as opposed to the observed ventilation of the thermocline. We further use a carbon cycle multi-box model to extrapolate this change in δ13

  14. Economical synthesis of 13C-labeled opiates, cocaine derivatives and selected urinary metabolites by derivatization of the natural products.

    PubMed

    Karlsen, Morten; Liu, Huiling; Johansen, Jon Eigill; Hoff, Bård Helge

    2015-01-01

    The illegal use of opiates and cocaine is a challenge world-wide, but some derivatives are also valuable pharmaceuticals. Reference samples of the active ingredients and their metabolites are needed both for controlling administration in the clinic and to detect drugs of abuse. Especially, (13)C-labeled compounds are useful for identification and quantification purposes by mass spectroscopic techniques, potentially increasing accuracy by minimizing ion alteration/suppression effects. Thus, the synthesis of [acetyl-(13)C4]heroin, [acetyl-(13)C4-methyl-(13)C]heroin, [acetyl-(13)C2-methyl-(13)C]6-acetylmorphine, [N-methyl-(13)C-O-metyl-(13)C]codeine and phenyl-(13)C6-labeled derivatives of cocaine, benzoylecgonine, norcocaine and cocaethylene was undertaken to provide such reference materials. The synthetic work has focused on identifying (13)C atom-efficient routes towards these derivatives. Therefore, the (13)C-labeled opiates and cocaine derivatives were made from the corresponding natural products.

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

    PubMed

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

    2005-12-14

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

  16. Chain packing in glassy polymers by natural-abundance 13C-13C spin diffusion using 2D centerband-only detection of exchange.

    PubMed

    Singh, Manmilan; Schaefer, Jacob

    2011-03-01

    The proximities of specific subgroups of nearest-neighbor chains in glassy polymers are revealed by distance-dependent (13)C-(13)C dipolar couplings and spin diffusion. The measurement of such proximities is practical even with natural-abundance levels of (13)C using a 2D version of centerband-only detection of exchange (CODEX). Two-dimensional CODEX is a relaxation-compensated experiment that avoids the problems associated with variations in T(1)(C)'s due to dynamic site heterogeneity in the glass. Isotropic chemical shifts are encoded in the t(1) preparation times before and after mixing, and variations in T(2)'s are compensated by an S(0) reference (no mixing). Data acquisition involves acquisition of an S(0) reference signal on alternate scans, and the active control of power amplifiers, to achieve stability and accuracy over long accumulation times. The model system to calibrate spin diffusion is the polymer itself. For a mixing time of 200 ms, only (13)C-(13)C pairs separated by one or two bonds (2.5 Å) show cross peaks, which therefore identify reference intrachain proximities. For a mixing time of 1200 ms, 5 Å interchain proximities appear. The resulting cross peaks are used in a simple and direct way to compare nonrandom chain packing for two commercial polycarbonates with decidedly different mechanical properties.

  17. Natural (13) C distribution in oil palm (Elaeis guineensis Jacq.) and consequences for allocation pattern.

    PubMed

    Lamade, Emmanuelle; Tcherkez, Guillaume; Darlan, Nuzul Hijri; Rodrigues, Rosario Lobato; Fresneau, Chantal; Mauve, Caroline; Lamothe-Sibold, Marlène; Sketriené, Diana; Ghashghaie, Jaleh

    2016-01-01

    Oil palm has now become one of the most important crops, palm oil representing nearly 25% of global plant oil consumption. Many studies have thus addressed oil palm ecophysiology and photosynthesis-based models of carbon allocation have been used. However, there is a lack of experimental data on carbon fixation and redistribution within palm trees, and important C-sinks have not been fully characterized yet. Here, we carried out extensive measurement of natural (13) C-abundance (δ(13) C) in oil palm tissues, including fruits at different maturation stages. We find a (13) C-enrichment in heterotrophic organs compared to mature leaves, with roots being the most (13) C-enriched. The δ(13) C in fruits decreased during maturation, reflecting the accumulation in (13) C-depleted lipids. We further used observed δ(13) C values to compute plausible carbon fluxes using a steady-state model of (13) C-distribution including metabolic isotope effects ((12) v/(13) v). The results suggest that fruits represent a major respiratory loss (≈39% of total tree respiration) and that sink organs such as fruits are fed by sucrose from leaves. That is, glucose appears to be a quantitatively important compound in palm tissues, but computations indicate that it is involved in dynamic starch metabolism rather that C-exchange between organs. PMID:26228944

  18. Evaluation of 13C isotopic tracers for metabolic flux analysis in mammalian cells

    PubMed Central

    Metallo, Christian M.; Walther, Jason L.; Stephanopoulos, Gregory

    2009-01-01

    13C metabolic flux analysis (MFA) is the most comprehensive means of characterizing cellular metabolic states. Uniquely labeled isotopic tracers enable more focused analyses to probe specific reactions within the network. As a result, the choice of tracer largely determines the precision with which one can estimate metabolic fluxes, especially in complex mammalian systems that require multiple substrates. Here we have experimentally determined metabolic fluxes in a tumor cell line, successfully recapitulating the hallmarks of cancer cell metabolism. Using these data, we computationally evaluated specifically labeled 13C glucose and glutamine tracers for their ability to precisely and accurately estimate fluxes in central carbon metabolism. These methods enabled us to to identify the optimal tracer for analyzing individual fluxes, specific pathways, and central carbon metabolism as a whole. [1,2-13C2]glucose provided the most precise estimates for glycolysis, the pentose phosphate pathway, and the overall network. Tracers such as [2-13C]glucose and [3-13C]glucose also outperformed the more commonly used [1-13C]glucose. [U-13C5]glutamine emerged as the preferred isotopic tracer for analysis of the tricarboxylic acid (TCA) cycle. These results provide valuable, quantitative information on the performance of 13C-labeled substrates and can aid in the design of more informative MFA experiments in mammalian cell culture. PMID:19622376

  19. Application of Good's buffers to pH imaging using hyperpolarized (13)C MRI.

    PubMed

    Flavell, Robert R; von Morze, Cornelius; Blecha, Joseph E; Korenchan, David E; Van Criekinge, Mark; Sriram, Renuka; Gordon, Jeremy W; Chen, Hsin-Yu; Subramaniam, Sukumar; Bok, Robert A; Wang, Zhen J; Vigneron, Daniel B; Larson, Peder E; Kurhanewicz, John; Wilson, David M

    2015-09-25

    N-(2-Acetamido)-2-aminoethanesulfonic acid (ACES), one of Good's buffers, was applied to pH imaging using hyperpolarized (13)C magnetic resonance spectroscopy. Rapid NMR- and MRI-based pH measurements were obtained by exploiting the sensitive pH-dependence of its (13)C chemical shift within the physiologic range.

  20. Draft Genome Sequence of a Tropical Freshwater Cyanobacterium, Limnothrix sp. Strain P13C2

    PubMed Central

    Tan, Boon Fei; Gin, Karina Yew-Hoong

    2016-01-01

    A nonaxenic unialgal culture of Limnothrix sp. strain P13C2 was obtained through multiple subculturing of an inoculum obtained from a tropical freshwater lake. Here, we report the genome of P13C2 of 4.6 Mbp, extracted from the metagenome of this coculture. PMID:27795269

  1. Natural (13) C distribution in oil palm (Elaeis guineensis Jacq.) and consequences for allocation pattern.

    PubMed

    Lamade, Emmanuelle; Tcherkez, Guillaume; Darlan, Nuzul Hijri; Rodrigues, Rosario Lobato; Fresneau, Chantal; Mauve, Caroline; Lamothe-Sibold, Marlène; Sketriené, Diana; Ghashghaie, Jaleh

    2016-01-01

    Oil palm has now become one of the most important crops, palm oil representing nearly 25% of global plant oil consumption. Many studies have thus addressed oil palm ecophysiology and photosynthesis-based models of carbon allocation have been used. However, there is a lack of experimental data on carbon fixation and redistribution within palm trees, and important C-sinks have not been fully characterized yet. Here, we carried out extensive measurement of natural (13) C-abundance (δ(13) C) in oil palm tissues, including fruits at different maturation stages. We find a (13) C-enrichment in heterotrophic organs compared to mature leaves, with roots being the most (13) C-enriched. The δ(13) C in fruits decreased during maturation, reflecting the accumulation in (13) C-depleted lipids. We further used observed δ(13) C values to compute plausible carbon fluxes using a steady-state model of (13) C-distribution including metabolic isotope effects ((12) v/(13) v). The results suggest that fruits represent a major respiratory loss (≈39% of total tree respiration) and that sink organs such as fruits are fed by sucrose from leaves. That is, glucose appears to be a quantitatively important compound in palm tissues, but computations indicate that it is involved in dynamic starch metabolism rather that C-exchange between organs.

  2. 29 CFR 2580.412-36 - Application of 13(c) to “party in interest”.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... members covered by such plan.” (b) A basic question presented is whether the effect of 13(c) is to... 29 Labor 9 2012-07-01 2012-07-01 false Application of 13(c) to âparty in interestâ. 2580.412-36... 1974 TEMPORARY BONDING RULES Prohibition Against Bonding by Parties Interested in the Plan §...

  3. Deglacial change in terrestrial carbon storage estimated by benthic δ13C

    NASA Astrophysics Data System (ADS)

    Peterson, C. D.; Lisiecki, L. E.

    2012-12-01

    Terrestrial carbon storage is dramatically decreased during glacial periods due to cold temperatures, increased aridity, and the presence of large ice sheets on land. Most of the carbon released by the terrestrial biosphere is stored in the glacial ocean, where the isotopic signature of terrestrial carbon (δ13C terrestrial carbon = -25‰) is observed as a 0.32-0.7‰ depletion in benthic foraminiferal δ13C. The wide range in estimated δ13C change is due to different subsets of benthic δ13C data and different methods of weighting the mean δ13C by volume. We estimate the glacial-interglacial δ13C change of marine DIC using benthic Cibicides spp. δ13C records from 356 core sites (five to eight times as many as previous studies). We divide the ocean into 9 regions to generate linear regressions of regional δ13C versus depth (0.5-5 km) for the late Holocene (0-6 ka) and LGM (18-21 ka) and estimate a mean δ13C decrease of 0.53 +/-0.06‰ (2σ), equivalent to 715-885 Pg C. Our estimate is in good agreement with a vegetation reconstruction estimate of ~750-1050 Pg C [Crowley, 1995] and a recent model estimate of ~670 Pg C [Kohler, 2010] and is ~66% larger than the previous whole ocean δ13C estimate of 0.32‰ [Duplessy et al., 1988]. To evaluate the uncertainty of our estimate, we used a bootstrapping approach (100,000 iterations) to generate realistic error estimates for our different regional line-fits of δ13C vs. depth for both the LGM and Holocene time slices. We propagated the bootstrapped linear regressions through all of our calculations to estimate a 95% confidence interval for global δ13C change (+/-0.06‰) and the uncertainty contribution from each region. The largest sources of uncertainty in our estimate are the South Pacific (35% of variance) and Indian Ocean (36% of variance) because they are the regions with the largest volumes and sparsest δ13C data. Additionally, we note that mean benthic δ13C change could in part reflect glacial

  4. Variation in woody plant delta(13)C along a topoedaphic gradient in a subtropical savanna parkland.

    PubMed

    Bai, Edith; Boutton, Thomas W; Liu, Feng; Wu, X Ben; Archer, Steven R

    2008-06-01

    delta(13)C values of C(3) plants are indicators of plant carbon-water relations that integrate plant responses to environmental conditions. However, few studies have quantified spatial variation in plant delta(13)C at the landscape scale. We determined variation in leaf delta(13)C, leaf nitrogen per leaf area (N(area)), and specific leaf area (SLA) in April and August 2005 for all individuals of three common woody species within a 308 x 12-m belt transect spanning an upland-lowland topoedaphic gradient in a subtropical savanna in southern Texas. Clay content, available soil moisture, and soil total N were all negatively correlated with elevation. The delta(13)C values of Prosopis glandulosa (deciduous N(2)-fixing tree legume), Condalia hookeri (evergreen shrub), and Zanthoxylum fagara (evergreen shrub) leaves increased 1-4 per thousand with decreasing elevation, with the delta(13)C value of P. glandulosa leaves being 1-3 per thousand higher than those of the two shrub species. Contrary to theory and results from previous studies, delta(13)C values were highest where soil water was most available, suggesting that some other variable was overriding or interacting with water availability. Leaf N(area) was positively correlated with leaf delta(13)C of all species (p < 0.01) and appeared to exert the strongest control over delta(13)C along this topoedaphic gradient. Since leaf N(area) is positively related to photosynthetic capacity, plants with high leaf N(area) are likely to have low p (I)/p (a) ratios and therefore higher delta(13)C values, assuming stomatal conductance is constant. Specific leaf area was not correlated significantly with leaf delta(13)C. Following a progressive growing season drought in July/August, leaf delta(13)C decreased. The lower delta(13)C in August may reflect the accumulation of (13)C-depleted epicuticular leaf wax. We suggest control of leaf delta(13)C along this topoedaphic gradient is mediated by leaf N(area) rather than by stomatal

  5. /sup 13/C nuclear magnetic resonance study of the complexation of calcium by taurine

    SciTech Connect

    Irving, C.S.; Hammer, B.E.; Danyluk, S.S.; Klein, P.D.

    1980-01-01

    /sup 13/C Nuclear magnetic resonance chemical shifts, /sup 1/J/sub c-c/ scalar coupling constants, spin-lattice relaxation times, and nuclear Overhauser effects were determined for taurine-(1, 2 /sup 13/C) and a taurine-(1 /sup 13/C) and taurine-(2 /sup 13/C) mixture in the presence and absence of calcium. Comparison of taurine titration shifts to values for related compounds reveals some unusual electronic properties of the taurine molecule. Stability constants of 1:1 calcium complexes with taurine zwitterions and anions, as well as their /sup 13/C chemical shifts, were obtained by least squares analysis of titration curves measured in the presence of calcium. The stability constants of calcium-taurine complexes were significantly lower than previous values and led to estimates that only approximately one percent of intracellular calcium of mammalian myocardial cells would exist in a taurine complex.

  6. Fish Movement and Dietary History Derived from Otolith (delta)13C

    SciTech Connect

    Weber, P K; Finlay, J C; Power, M E; Phillis, C C; Ramon, C E; Eaton, G F; Ingram, B L

    2005-09-08

    Habitat use and food web linkages are critical data for fish conservation and habitat restoration efforts, particularly for threatened salmonids species. Otolith microchemistry has been shown to be a powerful tool for reconstructing fish movement, but over small distances (kilometers), geology-derived differences in otolith chemistry are rare. Here, we demonstrate that otolith {sup 13}C/{sup 12}C ratio (i.e. {delta}{sup 13}C) of anadromous steelhead trout can be used to distinguish residence in small streams from residence in larger streams and rivers. While previous research has shown that water dissolved inorganic carbon {delta}{sup 13}C is the primary source of carbon in otoliths, the downstream change in food {delta}{sup 13}C in this watershed appears to be the primary control on otolith {delta}{sup 13}C. As a result, this method can also be applied to the problem of reconstructing feeding history at a location.

  7. A 13C-NMR study of exopolysaccharide synthesis in Rhizobium meliloti Su47 strain

    NASA Astrophysics Data System (ADS)

    Tavernier, P.; Portais, J.-C.; Besson, I.; Courtois, J.; Courtois, B.; Barbotin, J.-N.

    1998-02-01

    Metabolic pathways implied in the synthesis of succinoglycan produced by the Su47 strain of R. meliloti were evaluated by 13C-NMR spectroscopy after incubation with [1{-}13C] or [2{-}13C] glucose. The biosynthesis of this polymer by R. meliloti from glucose occurred by a direct polymerisation of the introduced glucose and by the pentose phosphate pathway. Les voies métaboliques impliquées dans la synthèse du succinoglycane produit par la souche Su47 de R. meliloti ont été évaluées par la spectroscopie de RMN du carbone 13 après incubation des cellules avec du [1{-}13C] ou [2{-}13C] glucose. La biosynthèse de ce polymère à partir du glucose se produit par polymérisation directe du glucose et par la voie des pentoses phosphate.

  8. An alternative and robust synthesis of [(13) C4 ]Baraclude® (entecavir).

    PubMed

    Easter, John A; Burrell, Richard C; Bonacorsi, Samuel J

    2013-10-01

    Stable isotope-labeled [(13) C4 ]entecavir (1) was prepared in 11 steps. Commercially available [(13) C]guanidine hydrochloride and diethyl[1,2,3-(13) C3 ]malonate were condensed to yield 2-amino[2,4,5,6-(13) C4 ]pyrimidine-4,6-diol (8). This was converted to the desired purine (7) in five steps. Introduction of the chiral epoxide was followed by subsequent deprotection to give [(13) C4 ]entecavir (1), in an overall yield of 5.7% from labeled precursors. The chemical purity of the title compound was determined to be >99% by HPLC. The isotopic distribution was determined by mass spectrometry to be 282[M + 4], 98.4%; 281[M + 3], 1.6%; and 278[M + 0], <0.1%.

  9. Multi-band frequency encoding method for metabolic imaging with hyperpolarized [1- 13C]pyruvate

    NASA Astrophysics Data System (ADS)

    von Morze, Cornelius; Reed, Galen; Shin, Peter; Larson, Peder E. Z.; Hu, Simon; Bok, Robert; Vigneron, Daniel B.

    2011-08-01

    A new method was developed for simultaneous spatial localization and spectral separation of multiple compounds based on a single echo, by designing the acquisition to place individual compounds in separate frequency encoding bands. This method was specially designed for rapid and robust metabolic imaging of hyperpolarized 13C substrates and their metabolic products, and was investigated in phantom studies and studies in normal mice and transgenic models of prostate cancer to provide rapid metabolic imaging of hyperpolarized [1- 13C]pyruvate and its metabolic products [1- 13C]lactate and [1- 13C]alanine at spatial resolutions up to 3 mm in-plane. Elevated pyruvate and lactate signals in the vicinity of prostatic tissues were observed in transgenic tumor mice. The multi-band frequency encoding technique enabled rapid metabolic imaging of hyperpolarized 13C compounds with important advantages over prior approaches, including less complicated acquisition and reconstruction methods.

  10. Fish movement and dietary history derived from otolith δ13C

    NASA Astrophysics Data System (ADS)

    Weber, P. K.; Finlay, J. C.; Power, M. E.; Phillis, C. C.; Ramon, C. E.; Eaton, G. F.; Ingram, B. L.

    2005-12-01

    Habitat use and food web linkages are critical data for fish conservation and habitat restoration efforts, particularly for threatened salmonids species. Otolith microchemistry has been shown to be a powerful tool for reconstructing fish movement, but over small distances (kilometers), geology-derived differences in otolith chemistry are rare. Here, we demonstrate that otolith 13C/12C ratio (i.e. δ13C) of anadromous steelhead trout can be used to distinguish residence in small streams from residence in larger streams and rivers. While previous research has shown that water dissolved inorganic carbon d13C is the primary source of carbon in otoliths, the downstream change in food δ13C in this watershed appears to be the primary control on otolith δ13C. As a result, this method can also be applied to the problem of reconstructing feeding history at a location.

  11. 13C magnetic resonance spectroscopy measurements with hyperpolarized [1‐13C] pyruvate can be used to detect the expression of transgenic pyruvate decarboxylase activity in vivo

    PubMed Central

    Dzien, Piotr; Tee, Sui‐Seng; Kettunen, Mikko I.; Lyons, Scott K.; Larkin, Timothy J.; Timm, Kerstin N.; Hu, De‐En; Wright, Alan; Rodrigues, Tiago B.; Serrao, Eva M.; Marco‐Rius, Irene; Mannion, Elizabeth; D'Santos, Paula; Kennedy, Brett W. C.

    2015-01-01

    Purpose Dissolution dynamic nuclear polarization can increase the sensitivity of the 13C magnetic resonance spectroscopy experiment by at least four orders of magnitude and offers a novel approach to the development of MRI gene reporters based on enzymes that metabolize 13C‐labeled tracers. We describe here a gene reporter based on the enzyme pyruvate decarboxylase (EC 4.1.1.1), which catalyzes the decarboxylation of pyruvate to produce acetaldehyde and carbon dioxide. Methods Pyruvate decarboxylase from Zymomonas mobilis (zmPDC) and a mutant that lacked enzyme activity were expressed using an inducible promoter in human embryonic kidney (HEK293T) cells. Enzyme activity was measured in the cells and in xenografts derived from the cells using 13C MRS measurements of the conversion of hyperpolarized [1‐13C] pyruvate to H13 CO3–. Results Induction of zmPDC expression in the cells and in the xenografts derived from them resulted in an approximately two‐fold increase in the H13 CO3–/[1‐13C] pyruvate signal ratio following intravenous injection of hyperpolarized [1‐13C] pyruvate. Conclusion We have demonstrated the feasibility of using zmPDC as an in vivo reporter gene for use with hyperpolarized 13C MRS. Magn Reson Med 76:391–401, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:26388418

  12. Compartmentalized Cerebral Metabolism of [1,6-13C]Glucose Determined by in vivo 13C NMR Spectroscopy at 14.1 T

    PubMed Central

    Duarte, João M. N.; Lanz, Bernard; Gruetter, Rolf

    2011-01-01

    Cerebral metabolism is compartmentalized between neurons and glia. Although glial glycolysis is thought to largely sustain the energetic requirements of neurotransmission while oxidative metabolism takes place mainly in neurons, this hypothesis is matter of debate. The compartmentalization of cerebral metabolic fluxes can be determined by 13C nuclear magnetic resonance (NMR) spectroscopy upon infusion of 13C-enriched compounds, especially glucose. Rats under light α-chloralose anesthesia were infused with [1,6-13C]glucose and 13C enrichment in the brain metabolites was measured by 13C NMR spectroscopy with high sensitivity and spectral resolution at 14.1 T. This allowed determining 13C enrichment curves of amino acid carbons with high reproducibility and to reliably estimate cerebral metabolic fluxes (mean error of 8%). We further found that TCA cycle intermediates are not required for flux determination in mathematical models of brain metabolism. Neuronal tricarboxylic acid cycle rate (VTCA) and neurotransmission rate (VNT) were 0.45 ± 0.01 and 0.11 ± 0.01 μmol/g/min, respectively. Glial VTCA was found to be 38 ± 3% of total cerebral oxidative metabolism, accounting for more than half of neuronal oxidative metabolism. Furthermore, glial anaplerotic pyruvate carboxylation rate (VPC) was 0.069 ± 0.004 μmol/g/min, i.e., 25 ± 1% of the glial TCA cycle rate. These results support a role of glial cells as active partners of neurons during synaptic transmission beyond glycolytic metabolism. PMID:21713114

  13. LASER BIOLOGY AND MEDICINE: Laser analysis of the 13C/12C isotope ratio in CO2 in exhaled air

    NASA Astrophysics Data System (ADS)

    Stepanov, E. V.

    2002-11-01

    Tunable diode lasers (TDLs) are applied to the diagnostics of gastroenterological diseases using respiratory tests and preparations enriched with the stable 13C isotope. This method of the analysis of the 13C/12C isotope ratio in CO2 in exhaled air is based on the selective measurement of the resonance absorption at the vibrational — rotational structure of 12CO2 and 13CO2. The CO2 transmission spectra in the region of 4.35 μm were measured with a PbEuSe double-heterostructure TDL. The accuracy of carbon isotope ratio measurements in CO2 of exhaled air performed with the TDL was ~0.5%. The data of clinical tests of the developed laser-based analyser are presented.

  14. Foliar d13C within a temperate deciduous forest: spatial, temporal, and species sources of variation

    SciTech Connect

    Garten Jr, Charles T; TaylorJr, G. E.

    1992-04-01

    Foliar {sup 13}C-abundance ({delta}{sup 13}C) was analyzed in the dominant trees of a temperate deciduous forest in east Tennessee (Walker Branch Watershed) to investigate the variation in foliar {delta}{sup 13}C as a function of time (within-year and between years), space (canopy height, watershed topography and habitat) and species (deciduous and coniferous taxa). Various hypotheses were tested by analyzing (i) samples collected from the field during the growing season and (ii) foliar tissues maintained in an archived collection. The {delta}{sup 13}C-value for leaves from the tops of trees was 2 to 3%. more positive than for leaves sampled at lower heights in the canopy. Quercus prinus leaves sampled just prior to autumn leaf fall had significantly more negative {delta}{sup 13}C-values than those sampled during midsummer. On the more xeric ridges, needles of Pinus spp. had more positive {delta}{sup 13}C-values than leaves from deciduous species. Foliar {delta}{sup 13}C-values differed significantly as a function of topography. Deciduous leaves from xeric sites (ridges and slopes) had more positive {delta}{sup 13}C-values than those from mesic (riparian and cove) environments. On the more xeric sites, foliar {delta}{sup 13}C was significantly more positive in 1988 (a dry year) relative to that in 1989 (a year with above-normal precipitation). In contrast, leaf {delta}{sup 13}C in trees from mesic valley bottoms did not differ significantly among years with disparate precipitation. Patterns in foliar {delta}{sup 13}C indicated a higher ratio of net CO{sub 2} assimilation to transpiration (A/E) for trees in more xeric versus mesic habitats, and for trees in xeric habitats during years of drought versus years of normal precipitation. However, A/E (units of mmol CO{sub 2} fixed/mol H{sub 2}O transpired) calculated on the basis of {delta}{sup 13}C-values for leaves from the more xeric sites was higher in a wet year (6.6 {+-} 1.2) versus a dry year (3.4 {+-} 0.4). This

  15. Non-catalytic facile synthesis of superhard phase of boron carbide (B13C2) nanoflakes and nanoparticles.

    PubMed

    Xie, Sky Shumao; Su, Liap Tat; Guo, Jun; Vasylkiv, Oleg; Borodianska, Hanna; Xi, Zhu; Krishnan, Gireesh M; Su, Haibin; Tokl, Alfred I Y

    2012-01-01

    Boron Carbide is one the hardest and lightest material that is also relatively easier to synthesis as compared to other superhard ceramics like cubic boron nitride and diamond. However, the brittle nature of monolithic advanced ceramics material hinders its use in various engineering applications. Thus, strategies that can toughen the material are of fundamental and technological importance. One approach is to use nanostructure materials as building blocks, and organize them into a complex hierarchical structure, which could potentially enhance its mechanical properties to exceed that of the monolithic form. In this paper, we demonstrated a simple approach to synthesize one- and two-dimension nanostructure boron carbide by simply changing the mixing ratio of the initial compound to influence the saturation condition of the process at a relatively low temperature of 1500 degrees C with no catalyst involved in the growing process. Characterization of the resulting nano-structures shows B13C2, which is a superhard phase of boron carbide as its hardness is almost twice as hard as the commonly known B4C. Using ab-initio density functional theory study on the elastic properties of both B12C3 and B13C2, the high hardness of B13C2 is consistent to our calculation results, where bulk modulus of B13C2 is higher than that of B4C. High resolution transmission electron microscopy of the nanoflakes also reveals high density of twinning defects which could potentially inhibit the crack propagation, leading to toughening of the materials.

  16. Theoretical investigation of Mössbauer hyperfine interactions in ordered FeNi and disordered Fe-Ni alloys

    NASA Astrophysics Data System (ADS)

    Guenzburger, Diana; Terra, Joice

    Electronic structure spin-polarized calculations were performed for 79-atoms embedded clusters representing the ordered intermetallic compound FeNi, the fcc Fe-rich disordered alloy Fe85Ni15 in an antiferromagnetic (AFM) configuration, and the ferromagnetic (FM) disordered alloy Fe50Ni50. The spin-polarized discrete variational method (DVM) in Density Functional theory was employed. Spin magnetic moments, as well as the 57Fe Mössbauer hyperfine parameters isomer shift and magnetic hyperfine fields, were obtained from the calculations. For FM Fe50Ni50, the effect of pressure on the hyperfine field and on the isomer shift was investigated, for three different local atomic configurations surrounding the 57Fe probe atom. In the case of the isomer shift, the calculated values were compared to reported experimental data.

  17. Theoretical investigation of Mössbauer hyperfine interactions in ordered FeNi and disordered Fe Ni alloys

    NASA Astrophysics Data System (ADS)

    Guenzburger, Diana; Terra, Joice

    2006-02-01

    Electronic structure spin-polarized calculations were performed for 79-atoms embedded clusters representing the ordered intermetallic compound FeNi, the fcc Fe-rich disordered alloy Fe85Ni15 in an antiferromagnetic (AFM) configuration, and the ferromagnetic (FM) disordered alloy Fe50Ni50. The spin-polarized discrete variational method (DVM) in Density Functional theory was employed. Spin magnetic moments, as well as the 57Fe Mössbauer hyperfine parameters isomer shift and magnetic hyperfine fields, were obtained from the calculations. For FM Fe50Ni50, the effect of pressure on the hyperfine field and on the isomer shift was investigated, for three different local atomic configurations surrounding the 57Fe probe atom. In the case of the isomer shift, the calculated values were compared to reported experimental data.

  18. hNCOcanH pulse sequence and a robust protocol for rapid and unambiguous assignment of backbone ((1)H(N), (15)N and (13)C') resonances in (15)N/(13)C-labeled proteins.

    PubMed

    Kumar, Dinesh; Hosur, Ramakrishna V

    2011-09-01

    A three-dimensional nuclear magnetic resonance (NMR) pulse sequence named as hNCOcanH has been described to aid rapid sequential assignment of backbone resonances in (15)N/(13)C-labeled proteins. The experiment has been derived by a simple modification of the previously described HN(C)N pulse sequence [Panchal et al., J. Biomol. NMR 20 (2001) 135-147]; t2 evolution is used to frequency label (13)C' rather than (15)N (similar trick has also been used in the design of hNCAnH pulse sequence from hNcaNH [Frueh et al., JACS, 131 (2009) 12880-12881]). The modification results in a spectrum equivalent to HNCO, but in addition to inter-residue correlation peaks (i.e. Hi , Ci-1), the spectrum also contains additional intra-residue correlation peaks (i.e. Hi-1 , Ci-1) in the direct proton dimension which has maximum resolution. This is the main strength of the experiment and thus, even a small difference in amide (1) H chemical shifts (5-6 Hz) can be used for establishing a sequential connectivity. This experiment in combination with the HNN experiment described previously [Panchal et al., J. Biomol. NMR 20 (2001) 135-147] leads to a more robust assignment protocol for backbone resonances ((1) H(N) , (15)N) than could be derived from the combination of HNN and HN(C)N experiments [Bhavesh et al., Biochemistry, 40 (2001) 14727-14735]. Further, this new protocol enables assignment of (13)C' resonances as well. We believe that the experiment and the protocol presented here will be of immense value for structural-and functional-proteomics research by NMR. Performance of this experiment has been demonstrated using (13)C/(15)N labeled ubiquitin.

  19. hNCOcanH pulse sequence and a robust protocol for rapid and unambiguous assignment of backbone ((1)H(N), (15)N and (13)C') resonances in (15)N/(13)C-labeled proteins.

    PubMed

    Kumar, Dinesh; Hosur, Ramakrishna V

    2011-09-01

    A three-dimensional nuclear magnetic resonance (NMR) pulse sequence named as hNCOcanH has been described to aid rapid sequential assignment of backbone resonances in (15)N/(13)C-labeled proteins. The experiment has been derived by a simple modification of the previously described HN(C)N pulse sequence [Panchal et al., J. Biomol. NMR 20 (2001) 135-147]; t2 evolution is used to frequency label (13)C' rather than (15)N (similar trick has also been used in the design of hNCAnH pulse sequence from hNcaNH [Frueh et al., JACS, 131 (2009) 12880-12881]). The modification results in a spectrum equivalent to HNCO, but in addition to inter-residue correlation peaks (i.e. Hi , Ci-1), the spectrum also contains additional intra-residue correlation peaks (i.e. Hi-1 , Ci-1) in the direct proton dimension which has maximum resolution. This is the main strength of the experiment and thus, even a small difference in amide (1) H chemical shifts (5-6 Hz) can be used for establishing a sequential connectivity. This experiment in combination with the HNN experiment described previously [Panchal et al., J. Biomol. NMR 20 (2001) 135-147] leads to a more robust assignment protocol for backbone resonances ((1) H(N) , (15)N) than could be derived from the combination of HNN and HN(C)N experiments [Bhavesh et al., Biochemistry, 40 (2001) 14727-14735]. Further, this new protocol enables assignment of (13)C' resonances as well. We believe that the experiment and the protocol presented here will be of immense value for structural-and functional-proteomics research by NMR. Performance of this experiment has been demonstrated using (13)C/(15)N labeled ubiquitin. PMID:21818779

  20. 13C18O in Earth's Atmosphere: a New Proxy for Constraining CO Budget

    NASA Astrophysics Data System (ADS)

    Guo, W.; Eiler, J. M.

    2005-12-01

    Despite its low average mixing ratio (70-100 ppbv), carbon monoxide plays an important role in atmospheric chemistry. It is the major sink of OH radicals, and thus strongly influences the oxidizing capacity of the atmosphere, and the lifetimes of many other atmospheric trace gases (e.g., methane, NHMCs and HCFCs). At present, the budget of atmospheric CO is constrained by its mixing ratio, δ13C, δ18O, δ17O values, inventory analysis and inverse modeling. However, the major sources of CO (CH4-oxidation, NMHC-oxidation, biomass burning, anthropogenic emissions and the ocean) vary in flux and isotopic composition, and some overlap one another in isotopic composition. Therefore, its atmospheric budget cannot be rigorously defined by inversion of the existing isotopic and concentration records. Here we introduce measurements of the abundance anomaly of the 13C18O isotopologue of carbon monoxide as an additional constraint on its atmospheric budget. We define the 13C18O anomaly as the deviation of its actual abundance from its expected statistical abundance,Δ13C18O=(([13C18O]actual/[12C16O]actual)/([13C18O]stati stical /[12C16O]statistical)-1)×1000. Abundances of 13C18O are measured by quantitatively oxidizing CO to CO2 over the Schutze reagent, and then measuring mass 47 (mainly 13C18O16O) in the product CO2, which is proportional to the abundance of 13C18O in the starting CO. External precision of Δ13C18O for repeated measurements of pure CO averages 0.03‰(one standard deviation). We expect Δ13C18O in atmospheric carbon monoxide to be sensitive to: mixing between CO of different isotopic compositions, thermodynamic fractionations, diffusion, and kinetic isotope effects accompanying chemical reactions. We have investigated the thermodynamic fractionation of Δ13C18O by performing measurements on carbon monoxide samples catalytically equilibrated at high temperatures (300-1000°C). Measured Δ13C18O values, ranging from ~0.08‰ to ~0.47‰, vary as a function

  1. High-resolution proton NMR studies of intracellular metabolites in yeast using 13C decoupling

    NASA Astrophysics Data System (ADS)

    Sillerud, Laurel O.; Alger, Jeffry R.; Shulman, Robert G.

    The resolution and specificity of 1H NMR in studies of yeast cellular metabolism were increased by feeding a 13C-labeled substrate and observing 1H difference spectra in the presence and absence of 13C decoupling fields. [2- 13C]Acetate was utilized as a respiratory substrate in an aerobic suspension of Saccharomyces cerevisiae. The broad cellular background proton resonances are removed by the technique, leaving only signals from the protons of the substrate, or its metabolites, that are coupled to 13C. Spectra of the yeast suspension after acetate feeding show the disappearance of label from the acetate pool and the subsequent appearance of 13C in glutamate C 3 and C 4 and in aspartate C 3. These results are in accord with the known fluxes of metabolites. Selective single-frequency 13C decoupling was used to provide assignments for the difference signals. The limitations on single-frequency decoupling coming from finite decoupling fields are investigated. The technique shows a potential for application in a wide variety of systems where the resolution of the 13C spectrum may be combined with the sensitivity for proton detection to observe metabolites that have been previously unobservable.

  2. Diurnal variation of the delta 13C of pine needle respired CO2 evolved in darkness.

    PubMed

    Prater, James L; Mortazavi, Behzad; Chanton, Jeffrey P

    2006-02-01

    The delta 13C of pine needle CO2 evolved in darkness (delta 13Cr) for slash pine trees (Pinus elliottii) was determined by placing recently collected pine needles in darkness and collecting respired CO2 over a short time period (<15 min). Delta 13Cr measurements were made over several 24 h periods to test the hypothesis that significant variation in delta 13Cr would be observed during a diurnal cycle. The delta 13Cr measurements from the 24 h time series trials showed a consistent midday 13C-enrichment (5-10 per thousand) relative to bulk biomass. The delta 13Cr values became more 13C-depleted at night and following shading, and approached bulk-biomass delta 13C values by dawn. The effect of night-time respired 13C-enriched CO2 on the delta 13C value of the remaining assimilate is shown to be minimal (13C depleted by 0.22 per thousand) under field conditions for P. elliottii needles.

  3. VizieR Online Data Catalog: Doubly 13C-substituted ethyl cyanide (Margules+,

    NASA Astrophysics Data System (ADS)

    Margules, L.; Belloche, A.; Muller, H. S. P.; Motiyenko, R. A.; Guillemin, J.-C.; Garrod, R. T.; Menten, K. M.

    2016-04-01

    We identified more than 5000 rotational transitions, pertaining to more than 3500 different transition frequencies, in the laboratory for each of the three doubly 13C-substituted isotopomers. The quantum numbers reach J~115 and Ka~35, resulting in accurate spectroscopic parameters and accurate rest frequency calculations beyond 1000 GHz for strong to moderately weak transitions of either isotopomer. All three species are unambiguously detected in our ALMA data. The 12C/13C column density ratio of the isotopomers with one 13C atom to those with two 13C atoms is about 25. Ethyl cyanide is the second molecule after methyl cyanide for which isotopologues containing two 13C atoms have been securely detected in the interstellar medium. The model of our ethyl cyanide data suggests that we should be able to detect vibrational satellites of the main species up to at least v19=1 at 1130K and up to v13+v21=2 at 600K for the isotopologues with one 13C atom in our present ALMA data. Such satellites may be too weak to be identified unambiguously for isotopologues with two 13C atoms. (3 data files).

  4. The hyperfine excitation of OH radicals by He

    NASA Astrophysics Data System (ADS)

    Marinakis, Sarantos; Kalugina, Yulia; Lique, François

    2016-04-01

    Hyperfine-resolved collisions between OH radicals and He atoms are investigated using quantum scattering calculations and the most recent ab initio potential energy surface, which explicitly takes into account the OH vibrational motion. Such collisions play an important role in astrophysics, in particular in the modelling of OH masers. The hyperfine-resolved collision cross sections are calculated for collision energies up to 2500 cm-1 from the nuclear spin free scattering S-matrices using a recoupling technique. The collisional hyperfine propensities observed are discussed. As expected, the results from our work suggest that there is a propensity for collisions with ΔF = Δj. The new OH-He hyperfine cross sections are expected to significantly help in the modelling of OH masers from current and future astronomical observations. Contribution to the Topical Issue "Atomic Cluster Collisions (7th International Symposium)", edited by Gerardo Delgado Barrio, Andrey Solov'Yov, Pablo Villarreal, Rita Prosmiti.

  5. 13C Incorporation into Signature Fatty Acids as an Assay for Carbon Allocation in Arbuscular Mycorrhiza

    PubMed Central

    Olsson, Pål Axel; van Aarle, Ingrid M.; Gavito, Mayra E.; Bengtson, Per; Bengtsson, Göran

    2005-01-01

    The ubiquitous arbuscular mycorrhizal fungi consume significant amounts of plant assimilated C, but this C flow has been difficult to quantify. The neutral lipid fatty acid 16:1ω5 is a quantitative signature for most arbuscular mycorrhizal fungi in roots and soil. We measured carbon transfer from four plant species to the arbuscular mycorrhizal fungus Glomus intraradices by estimating 13C enrichment of 16:1ω5 and compared it with 13C enrichment of total root and mycelial C. Carbon allocation to mycelia was detected within 1 day in monoxenic arbuscular mycorrhizal root cultures labeled with [13C]glucose. The 13C enrichment of neutral lipid fatty acid 16:1ω5 extracted from roots increased from 0.14% 1 day after labeling to 2.2% 7 days after labeling. The colonized roots usually were more enriched for 13C in the arbuscular mycorrhizal fungal neutral lipid fatty acid 16:1ω5 than for the root specific neutral lipid fatty acid 18:2ω6,9. We labeled plant assimilates by using 13CO2 in whole-plant experiments. The extraradical mycelium often was more enriched for 13C than was the intraradical mycelium, suggesting rapid translocation of carbon to and more active growth by the extraradical mycelium. Since there was a good correlation between 13C enrichment in neutral lipid fatty acid 16:1ω5 and total 13C in extraradical mycelia in different systems (r2 = 0.94), we propose that the total amount of labeled C in intraradical and extraradical mycelium can be calculated from the 13C enrichment of 16:1ω5. The method described enables evaluation of C flow from plants to arbuscular mycorrhizal fungi to be made without extraction, purification and identification of fungal mycelia. PMID:15870350

  6. A study of the molecular conformations and the vibrational, 1H and 13C NMR spectra of the anticancer drug tamoxifen and triphenylethylene

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Khan, Ibrahim

    2016-08-01

    The structural stability and the vibrational spectra of the anticancer drug tamoxifen and triphenylethylene were investigated by the DFT B3LYP/6-311G (d,p) calculations. Tamoxifen and triphenylethylene were predicted to exist predominantly as non-planar structures. The vibrational frequencies and the 1H and 13C NMR chemical shifts of the low energy structures of tamoxifen and triphenylethylene were computed at the DFT B3LYP level of theory. Complete vibrational assignments were provided by combined theoretical and experimental data of tamoxifen and triphenylethylene. The 1H and 13C NMR spectra of both molecules were interpreted by experimental and DFT calculated chemical shifts of the two molecules. The RMSD between experimental and theoretical 1H and 13C chemical shifts for tamoxifen is 0.29 and 4.72 ppm, whereas for triphenylethylene, it is 0.16 and 2.70 ppm, respectively.

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

    PubMed Central

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

    2005-01-01

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

  8. Position-Specific Isotope Analysis of Xanthines: A (13)C Nuclear Magnetic Resonance Method to Determine the (13)C Intramolecular Composition at Natural Abundance.

    PubMed

    Diomande, Didier G; Martineau, Estelle; Gilbert, Alexis; Nun, Pierrick; Murata, Ariaki; Yamada, Keita; Watanabe, Naoharu; Tea, Illa; Robins, Richard J; Yoshida, Naohiro; Remaud, Gérald S

    2015-07-01

    The natural xanthines caffeine, theobromine, and theophylline are of major commercial importance as flavor constituents in coffee, cocoa, tea, and a number of other beverages. However, their exploitation for authenticity, a requirement in these commodities that have a large origin-based price-range, by the standard method of isotope ratio monitoring by mass spectrometry (irm-MS) is limited. We have now developed a methodology that overcomes this deficit that exploits the power of isotopic quantitative (13)C nuclear magnetic resonance (NMR) spectrometry combined with chemical modification of the xanthines to enable the determination of positional intramolecular (13)C/(12)C ratios (δ(13)Ci) with high precision. However, only caffeine is amenable to analysis: theobromine and theophylline present substantial difficulties due to their poor solubility. However, their N-methylation to caffeine makes spectral acquisition feasible. The method is confirmed as robust, with good repeatability of the δ(13)Ci values in caffeine appropriate for isotope fractionation measurements at natural abundance. It is shown that there is negligible isotope fractionation during the chemical N-methylation procedure. Thus, the method preserves the original positional δ(13)Ci values. The method has been applied to measure the position-specific variation of the (13)C/(12)C distribution in caffeine. Not only is a clear difference between caffeine isolated from different sources observed, but theobromine from cocoa is found to show a (13)C pattern distinct from that of caffeine. PMID:26067163

  9. Two new organic reference materials for δ13C and δ15N measurements and a new value for the δ13C of NBS 22 oil

    USGS Publications Warehouse

    Qi, Haiping; Coplen, Tyler B.; Geilmann, Heike; Brand, Willi A.; Bohlke, John Karl

    2003-01-01

    Analytical grade L-glutamic acid is chemically stable and has a C/N mole ratio of 5, which is close to that of many of natural biological materials, such as blood and animal tissue. Two L-glutamic acid reference materials with substantially different 13C and 15N abundances have been prepared for use as organic reference materials for C and N isotopic measurements. USGS40 is analytical grade L-glutamic acid and has a δ13C value of −26.24‰ relative to VPDB and a δ15N value of −4.52‰ relative to N2 in air. USGS41 was prepared by dissolving analytical grade L-glutamic acid with L-glutamic acid enriched in 13C and 15N. USGS41 has a δ13C value of +37.76‰ and a δ15N value of +47.57‰. The δ13C and δ15N values of both materials were measured against the international reference materials NBS 19 calcium carbonate (δ13C = +1.95‰), L-SVEC lithium carbonate (δ13C = −46.48‰), IAEA-N-1 ammonium sulfate (δ15N = 0.43‰), and USGS32 potassium nitrate (δ15N = 180‰) by on-line combustion continuous-flow and off-line dual-inlet isotope-ratio mass spectrometry. Both USGS40 and USGS41 are isotopically homogeneous; reproducibility of δ13C is better than 0.13‰, and that of δ15N is better than 0.13‰ in 100-μg amounts. These two isotopic reference materials can be used for (i) calibrating local laboratory reference materials, and (ii) quantifying drift with time, mass-dependent fractionations, and isotope-ratio-scale contraction in the isotopic analysis of various biological materials. Isotopic results presented in this paper yield a δ13C value for NBS 22 oil of −29.91‰, in contrast to the commonly accepted value of −29.78‰ for which off-line blank corrections probably have not been quantified satisfactorily.

  10. A roadmap for interpreting 13C metabolite labeling patterns from cells

    PubMed Central

    Buescher, Joerg M.; Antoniewicz, Maciek R.; Boros, Laszlo G.; Burgess, Shawn C.; Brunengraber, Henri; Clish, Clary B.; DeBerardinis, Ralph J.; Feron, Olivier; Frezza, Christian; Ghesquiere, Bart; Gottlieb, Eyal; Hiller, Karsten; Jones, Russell G.; Kamphorst, Jurre J.; Kibbey, Richard G.; Kimmelman, Alec C.; Locasale, Jason W.; Lunt, Sophia Y.; Maddocks, Oliver D. K.; Malloy, Craig; Metallo, Christian M.; Meuillet, Emmanuelle J.; Munger, Joshua; Nöh, Katharina; Rabinowitz, Joshua D.; Ralser, Markus; Sauer, Uwe; Stephanopoulos, Gregory; St-Pierre, Julie; Tennant, Daniel A.; Wittmann, Christoph; Vander Heiden, Matthew G.; Vazquez, Alexei; Vousden, Karen; Young, Jamey D.; Zamboni, Nicola; Fendt, Sarah-Maria

    2015-01-01

    Measuring intracellular metabolism has increasingly led to important insights in biomedical research. 13C tracer analysis, although less information-rich than quantitative 13C flux analysis that requires computational data integration, has been established as a time-efficient method to unravel relative pathway activities, qualitative changes in pathway contributions, and nutrient contributions. Here, we review selected key issues in interpreting 13C metabolite labeling patterns, with the goal of drawing accurate conclusions from steady state and dynamic stable isotopic tracer experiments. PMID:25731751

  11. Novel biological insights through metabolomics and 13C-flux analysis.

    PubMed

    Zamboni, Nicola; Sauer, Uwe

    2009-10-01

    Metabolomics and (13)C-flux analysis have become instrumental for analyzing cellular metabolism and its regulation. Driven primarily by technical advances in mass spectrometry-based analytics, they provide unmatched readouts on metabolic state and activity. Functional genomics leverages metabolomics for the discovery of novel enzymes and unexpected secondary activities of annotated enzymes. (13)C-flux analyses are frequently used for empirical elucidation of pathways in poorly characterized species and for network-wide analysis of mechanisms that realize energy and redox balancing. Integration of metabolomics, (13)C-flux analysis and other data enable the condition-dependent characterization of regulatory circuits that ultimately govern the metabolic phenotype.

  12. Polarization operator contributions to the Lamb shift and hyperfine splitting

    SciTech Connect

    Eides, Michael I.; Shelyuto, Valery A.

    2003-10-01

    We calculate radiative corrections to the Lamb shift of order {alpha}{sup 3}(Z{alpha}){sup 5}m and radiative corrections to hyperfine splitting of order {alpha}{sup 3}(Z{alpha})E{sub F} generated by the diagrams with insertions of radiative photons and electron polarization loops in the graphs with two external photons. We also obtain the radiative-recoil correction to hyperfine splitting in muonium generated by the diagrams with the {tau} polarization loop.

  13. Thermal and nuclear hyperfine properties of Ho(OH)3

    NASA Astrophysics Data System (ADS)

    Karmakar, S.

    1985-05-01

    A reasonable explanation for the findings of Catanese and Meissner [Phys. Rev. B 8, 2071 (1973)] regarding the (hyperfine) heat capacity in the low-temperature region of Ho(OH)3 is given. The Schottky specific heat in the high-temperature region observed calorimetrically by Chirico et al. [J. Chem. Thermodyn. 13, 1092 (1981)] explained satisfactorily. Nuclear hyperfine constants for Ho3+ ions in Ho(OH)3 are determined.

  14. Stable Carbon Isotopes (δ 13C) in Coral Skeletons: Experimental Approach and Applications for Paleoceanography

    NASA Astrophysics Data System (ADS)

    Grottoli, A. G.

    2004-12-01

    Scleractinian corals obtain fixed carbon via photosynthesis by their endosymbiotic algae (zooxanthellae) and via hetertrophy (injestion of zooplankton, δ 13C ≈ -17 to -22‰ ). Carbon dioxide (CO2) used for photosynthesis is obtained