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Sample records for 13c suess effect

  1. 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

  2. 13C Suess effect in scleractinian corals mirror changes in the anthropogenic CO2 inventory of the surface oceans

    NASA Astrophysics Data System (ADS)

    Swart, P. K.; Greer, L.; Rosenheim, B. E.; Moses, C. S.; Winter, A.; Dodge, R. E.; Helmle, K. P.

    2009-12-01

    New δ13C data are presented from ten coral skeletons collected from Florida and the Caribbean. These corals range from 96 to 200 years in age and were collected between 1976 and 2002. The change in the δ13C of the skeletons (Δδ13C/Δt) of these corals has been measured between 1900 and 1990 and have been compared with 26 other published coral records from the Atlantic, Pacific, and Indian Oceans. Together these data make possible a global comparison of Δδ13C/Δt changes in coral skeletons. Of the records, 78 % show a decrease in δ13C towards the modern day, statistically significant (p<0.05) in over 64 % of these records. This decrease is attributable to the addition of anthropogenically derived CO2 to the atmosphere (13C Suess effect). Between 1900 and 1990, the average Δδ13C/Δt in coral skeletons is approximately -0.01 ‰. In the Atlantic Ocean the magnitude of the Δδ13C/Δt since 1960 (-0.019+/-0.015‰/yr) is essentially the same as the decrease observed in the atmosphere and the oceans (-0.023 to -0.029‰/yr), while in the Pacific and Indian Oceans the rate is more variable and significantly reduced (-0.007 +/-0.013 ‰ /yr). These data strongly support the notion that (i) the δ13C of the atmosphere controls ambient δ13C of the dissolved inorganic carbon which in turn is reflected in coral skeletons, (ii) the rate of decline in the coral skeletons is higher in oceans with a greater anthropogenic CO2 inventory in the surface oceans, (iii) the rate of δ13C decline is accelerating.

  3. The 13C Suess effect in scleractinian corals mirror changes in the anthropogenic CO2 inventory of the surface oceans

    NASA Astrophysics Data System (ADS)

    Swart, Peter K.; Greer, Lisa; Rosenheim, Brad E.; Moses, Chris S.; Waite, Amanda J.; Winter, A.; Dodge, Richard E.; Helmle, Kevin

    2010-03-01

    New δ13C data are presented from 10 coral skeletons collected from Florida and elsewhere in the Caribbean (Dominica, Dominican Republic, Puerto Rico, and Belize). These corals range from 96 to 200 years in age and were collected between 1976 and 2002. The change in the δ13C of the skeletons from these corals between 1900 and 1990 has been compared with 27 other published coral records from the Atlantic, Pacific, and Indian Oceans. The new data presented here make possible, for the first time, a global comparison of rates of change in the δ13C value of coral skeletons. Of these records, 64% show a statistically significant (p < 0.05) decrease in δ13C towards the modern day (23 out of 37). This decrease is attributable to the addition of anthropogenically derived CO2 (13C Suess effect) to the atmosphere. Between 1900 and 1990, the average rate of change of the δ13C in all the coral skeletons living under open oceanic conditions is approximately -0.01‰ yr-1. In the Atlantic Ocean the magnitude of the decrease since 1960,-0.019 yr-1 ±0.015‰, is essentially the same as the decrease in the δ13C of atmospheric CO2 and the δ13C of the oceanic dissolved inorganic carbon (-0.023 to -0.029‰ yr-1), while in the Pacific and Indian Oceans the rate is more variable and significantly reduced (-0.007‰ yr-1 ±0.013). These data strongly support the notion that (i) the δ13C of the atmosphere controls ambient δ13C of the dissolved inorganic carbon which in turn is reflected in the coral skeletons, (ii) the rate of decline in the coral skeletons is higher in oceans with a greater anthropogenic CO2 inventory in the surface oceans, (iii) the rate of δ13C decline is accelerating. Superimposed on these secular variations are controls on the δ13C in the skeleton governed by growth rate, insolation, and local water masses.

  4. Local Variations in the 13-Suess Effect: A Global and Regional Phenomenon

    NASA Astrophysics Data System (ADS)

    Swart, P. K.; Okazaki, R.; Waite, A.

    2012-12-01

    low delivery the system tends to come back into equilibrium. As patterns of precipitation are often link through climate teleconnections, deviations in the δ13C of corals from the global trends are frequently correlated in geographic disparate areas. Such as the case here where similar deviations from the 13C- Suess effect can be observed in corals from localities throughout the Caribbean.

  5. Evaluating the Influence of Solar Radiation, Coral Extension Rate and Anthropogenic CO2 on Skeletal δ13C in a Network of Fiji and Tonga Porites Corals

    NASA Astrophysics Data System (ADS)

    Dassie, E. P.; Lemley, G. M.; Linsley, B. K.; Howe, S. S.

    2011-12-01

    While stable oxygen isotope signatures in coral reefs have proven to be reliable recorders of temperature and salinity, it is difficult to interpret their skeletal 13C/12C signatures. Various studies have suggested that coral skeletal δ13C is primarily controlled by complex physiological mechanisms. However, it has also been proposed that δ13C variations in coral skeletons are related to more apparent factors such as solar radiation, skeletal extension rate, and the anthropogenic addition of 13C-depleted CO2 into the atmosphere and surface ocean ("Suess Effect"). We will present time-series variations of δ13C in six coral cores from Fiji and Tonga (South Pacific Ocean). On seasonal timescales, increases in solar radiation are correlated to increases in skeletal δ13C and visa-versa. Annually averaged data shows a correlation between increased coral δ13C and reduced coral extension rate, while a decrease in δ13C is associated with an increased extension rate. In the most recent portion of four of the coral δ13C records (from around 1900 to the core top), the value progressively decreases - a trend that is not present in either the skeletal extension rate or solar radiation data. We conclude that this decreasing δ13C trend is a consequence of the Suess Effect, as reported in other coral δ13C records. However, two of the six corals do not show this decreasing trend, which may be a result of their residence in especially shallow water (sub-tidal environments). The onset of the Suess effect in the four corals may help constrain the timing of the uptake of anthropogenic carbon by the western South Pacific Ocean. Although all factors controlling δ13C variation in corals are not completely understood, this study works towards an understanding of their relative contribution to δ13C variation.

  6. Pre-bomb {Delta}{sup 14}C variability and the Suess Effect in Cariaco Basin Surface Waters as Recorded in Hermatypic Corals

    SciTech Connect

    Guilderson, T; Cole, J; Southon, J

    2004-10-28

    The {Delta}{sup 14}C content of surface waters in and around the Cariaco Basin were reconstructed from {sup 14}C measurements on sub-annually sampled coral skeletal material. During the late 1930s - early 1940s surface waters within and outside of the Cariaco Basin are similar. Within the Cariaco Basin at Islas Tortugas coral {Delta}{sup 14}C averages -51.9 {+-}3.3 {per_thousand}. Corals collected outside of the basin at Boca de Medio and Los Testigos have {Delta}{sup 14}C values of -53.4 {+-} 3.3 {per_thousand} and -54.3 {+-} 2.6 respectively. Additional {sup 14}C analyses on the Isla Tortugas coral document an {approx} 11 {per_thousand} decrease between {approx}1905 (-40.9 {+-}4.5 {per_thousand}) and {approx}1940. The implied Suess Effect trend (-3 {per_thousand}/decade) is nearly as large as that observed in the atmosphere over the same time period. If we assume that there is little to no fossil fuel {sup 14}CO{sub 2} signature in Cariaco surface waters in {approx}1905, the waters have an equivalent reservoir age of {approx}312 years.

  7. Effects of sampling method on foliar δ (13)C of Leymus chinensis at different scales.

    PubMed

    Liu, Yanjie; Li, Yan; Zhang, Lirong; Xu, Xingliang; Niu, Haishan

    2015-03-01

    Stable carbon isotope composition (δ (13)C) usually shows a negative relationship with precipitation at a large scale. We hypothesized that sampling method affects foliar δ (13)C and its response pattern to precipitation. We selected 11 sites along a precipitation gradient in Inner Mongolia and collected leaves of Leymus chinensis with five or six replications repeatedly in each site from 2009 to 2011. Additionally, we collected leaves of L. chinensis separately from two types of grassland (grazed and fenced) in 2011. Foliar δ (13)C values of all samples were measured. We compared the patterns that foliar δ (13)C to precipitation among different years or different sample sizes, the differences of foliar δ (13)C between grazed and fenced grassland. Whether actual annual precipitation (AAP) or mean annual precipitation (MAP), it was strongly correlated with foliar δ (13)C every year. Significant difference was found between the slopes of foliar δ (13)C to AAP and MAP every year, among the slopes of foliar δ (13)C to AAP from 2009 to 2011. The more samples used at each site the lower and convergent P-values of the linear regression test between foliar δ (13)C and precipitation. Furthermore, there was significant lower foliar δ (13)C value in presence of grazed type than fenced type grassland. These findings provide evidence that there is significant effect of sampling method to foliar δ (13)C and its response pattern to precipitation of L. chinensis. Our results have valuable implications in methodology for future field sampling studies. PMID:25798224

  8. Coupling and higher-order effects in the {sup 12}C(d,p){sup 13}C and {sup 13}C(p,d){sup 12}C reactions

    SciTech Connect

    Delaunay, F.; Nunes, F.M.; Lynch, W.G.; Tsang, M.B.

    2005-07-01

    Coupled-channel calculations are performed for the {sup 12}C(d,p){sup 13}C and {sup 13}C(p,d){sup 12}C reactions between 7 and 60 MeV to study the effect of inelastic couplings in transfer reactions. The effect of treating transfer beyond Born approximation is also addressed. The coupling to the {sup 12}C 2{sup +} state is found to change the peak cross section by up to 15%. Effects beyond Born approximation lead to a significant renormalization of the cross sections, between 5% and 10% for deuteron energies above 10 MeV and larger than 10% for lower energies. We also performed calculations including the remnant term in the transfer operator, which has a small impact on the {sup 12}C(d,p){sup 13}C(g.s.) and {sup 13}C(p,d){sup 12}C(g.s.) reactions (where g.s. indicates ground state). Above 30-MeV deuteron energy, the effect of the remnant term is larger than 10% for the {sup 12}C(d,p){sup 13}C(1/2{sup +}, 3.09 MeV) reaction and is found to increase with decreasing neutron separation energy for the 3.09-MeV state of {sup 13}C. This is of importance for transfer reactions with weakly bound nuclei.

  9. Evidence of 13C non-covalent isotope effects obtained by quantitative 13C nuclear magnetic resonance spectroscopy at natural abundance during normal phase liquid chromatography.

    PubMed

    Botosoa, Eliot P; Silvestre, Virginie; Robins, Richard J; Rojas, Jose Manuel Moreno; Guillou, Claude; Remaud, Gérald S

    2009-10-16

    Quantitative isotopic (13)C NMR at natural abundance has been used to determine the site-by-site (13)C/(12)C ratios in vanillin and a number of related compounds eluted from silica gel chromatography columns under similar conditions. Head-to-tail isotope fractionation is observed in all compounds at the majority of carbon positions. Furthermore, the site-specific isotope deviations show signatures characteristic of the position and functionality of the substituents present. The observed effects are more complex than would be obtained by simply summing the individual effects. Such detail is hidden when only the global (13)C content is measured by mass spectrometry. In particular, carbon positions within the aromatic ring are found to show site-specific isotope fractionation between the solute and the stationary phase. These interactions, defined as non-covalent isotope effects, can be normal or inverse and vary with the substitution pattern present. PMID:19748628

  10. The effect of chemical processing on the δ 13C value of plant tissue

    NASA Astrophysics Data System (ADS)

    Van de Water, Peter K.

    2002-04-01

    The effect of standard processing techniques on the δ 13C value of plant tissue was tested using species representing the three photosynthetic pathways, including angiosperms and gymnosperms within the C 3 taxonomic division. The species include Cowania mexicana (C 3 angiosperm), Juniperus osteosperma (C 3 gymnosperm), Opuntia spp. (crassulacean acid metabolism [CAM] angiosperm), and Atriplex canescens (C 4 angiosperm). Each species is represented by 5 plants collected at two different sites, for a total of 10 samples. The samples were processed to whole plant tissue, holocellulose, α-cellulose, and nitrocellulose. An additional process was added with the discovery of residual Ca-oxalate crystals in holocellulose samples. Both C 3 species show δ 13C values becoming 13C enriched with increased processing. The CAM representative shows the opposite trend, with 13C depletion during the progression of treatments. The greatest range of values and most inconsistent trends occur in the C 4 representative. Removal of the Ca-oxalate fraction resulted in different mean weight percentages and δ 13C values among the species. Calculated δ 13C values of the Ca-oxalate crystals show depletion from the tissue values in the two C 3 species and enrichment in the C 4 and CAM representatives. The C. mexicana samples show the greatest change between the tissue and Ca-oxalates (7.3‰) but the least mean weight percentage (11%), whereas A. canescens shows the greatest overall change, with a -2.8‰ isotopic shift and over 48% mean weight percentage. Variability within the samples undergoing each treatment remained relatively unchanged even with increased cellulose purity. This paper provides estimates of isotopic offsets necessary to correct from one treatment to another. Significant differences in δ 13C among different treatments confirm the need to state the tissue fraction analyzed when reporting δ 13C results.

  11. Theoretical estimation of 13C-D clumped isotope effects in methyl of several organic compound

    NASA Astrophysics Data System (ADS)

    LIU, Q.; Yin, X.; Liu, Y.

    2015-12-01

    Recent developments in mass spectrometry and tunable infrared laser direct absorption spectroscopy make it possible to measure 13C-D clumped isotope effects of methane. These techniques can be further applied to determine 13C-D clumped isotope effects of methyl fragments, therefore need accurate equilirbium Δi values to calibrate experimental measurements. In this study, we calculate temperature depandences of 13C-D clumped isotope signatures in methyl of several organic compounds including ethane, propane, acetic acid, etc. Our calculation are performed at CCSD/6-311+G(3df,3pd) by using Gaussian 03 program with no scale treament. Our results show that the Δi values of 13C-D clumping in methyl fragments of different organic compounds yield similar signals (~5.5‰ at 25˚C, slightly lower than Δi value of 13C-D clumping in methane). For testing the calculated accuracy, theoretical treaments beyond the harmonic level by including several higher-order corrections to the Bigeleisen-Mayer equation are used. Contributions from higher-order corrections (e.g., AnZPE, AnEXC, VrZPE, VrEXC, QmCorr and CenDist) are estimated to repire the ignorings of the Bigeleisen-Mayer equation (the anharmonic effects of vibration, vibration-rotation coupling, quantum mechanics and centrifugal distortion for rotation, etc.) for the calculation of partition function ratios. The results show that the higher-order corrections contribute ~0.05‰ at 25˚C, which is similar to the contribution for calculating 13C-D clumped isotope signature of methane. By comparing our calculated frequencies to the measured ones, the uncertainty of our calculation of Δi values 13C-D clumping in methyl fragments is considered to be within ~0.05‰ at room temperature.

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

    PubMed

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

    2001-01-01

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

  13. Neuroprotective effects of caffeine in MPTP model of Parkinson's disease: A (13)C NMR study.

    PubMed

    Bagga, Puneet; Chugani, Anup N; Patel, Anant B

    2016-01-01

    Parkinson's disease (PD) is a neurodegenerative disorder characterized by degeneration of nigrostriatal dopaminergic neurons with an accompanying neuroinflammation leading to loss of dopamine in the basal ganglia. Caffeine, a well-known A2A receptor antagonist is reported to slow down the neuroinflammation caused by activated microglia and reduce the extracellular glutamate in the brain. In this study, we have evaluated the neuroprotective effect of caffeine in the MPTP model of PD by monitoring the region specific cerebral energy metabolism. Adult C57BL6 mice were treated with caffeine (30 mg/kg, i.p.) 30 min prior to MPTP (25 mg/kg, i.p.) administration for 8 days. The paw grip strength of mice was assessed in order to evaluate the motor function after various treatments. For metabolic studies, mice were infused with [1,6-(13)C2]glucose, and (13)C labeling of amino acids was monitored using ex vivo(1)H-[(13)C]-NMR spectroscopy. The paw grip strength was found to be reduced following the MPTP treatment. The caffeine pretreatment showed significant protection against the reduction of paw grip strength in MPTP treated mice. The levels of GABA and myo-inositol were found to be elevated in the striatum of MPTP treated mice. The (13)C labeling of GluC4, GABAC2 and GlnC4 from [1,6-(13)C2]glucose was decreased in the cerebral cortex, striatum, olfactory bulb, thalamus and cerebellum suggesting impaired glutamatergic and GABAergic neuronal activity and neurotransmission of the MPTP treated mice. Most interestingly, the pretreatment of caffeine maintained the (13)C labeling of amino acids to the control values in cortical, olfactory bulb and cerebellum regions while it partially retained in striatal and thalamic regions in MPTP treated mice. The pretreatment of caffeine provides a partial neuro-protection against severe striatal degeneration in the MPTP model of PD. PMID:26626997

  14. Temporal δ13C records from bottlenose dolphins (Tursiops truncatus) reflect variation in foraging location and global carbon cycling

    NASA Astrophysics Data System (ADS)

    Rossman, S. L.; Barros, N. B.; Ostrom, P. H.; Gandhi, H.; Wells, R. S.

    2010-12-01

    first year of life. Given the age of bottlenose dolphins from SB (ca. 60 years), our isotopic data provide a record beginning in 1944. While carbon isotope values show a striking decline over time, the data must be corrected for the Suess effect. The Suess effect results from burning of 13C depleted hydrocarbons which causes a decrease in the δ13C of atmospheric CO2 that subsequent depresses isotope values in food webs. To account for the Suess effect, δ13C values are adjusted by 0.15‰ per decade. Suess corrected δ13C values do not show a temporal linear trend however the average isotope value prior to 1960 is significantly higher than that after 1960 (-10.1 vs -11.66, p=0.038). While documented declines in seagrass abundance prior to 1980 may influence our data, the decline in δ13C of atmospheric CO2 is likely an important factor that controls the isotopic composition of dolphin tissues. Our results suggest that isotope-based estimates of foraging should account for the Suess effect, and that dolphins act as environmental sentinels whose δ13C values records perturbations in global carbon cycling.

  15. High resolution (13)C MRI with hyperpolarized urea: in vivo T(2) mapping and (15)N labeling effects.

    PubMed

    Reed, Galen D; von Morze, Cornelius; Bok, Robert; Koelsch, Bertram L; Van Criekinge, Mark; Smith, Kenneth J; Hong Shang; Larson, Peder E Z; Kurhanewicz, John; Vigneron, Daniel B

    2014-02-01

    (13)C steady state free precession (SSFP) magnetic resonance imaging and effective spin-spin relaxation time (T2) mapping were performed using hyperpolarized [(13)C] urea and [(13) C,(15)N2] urea injected intravenously in rats. (15)N labeling gave large T2 increases both in solution and in vivo due to the elimination of a strong scalar relaxation pathway. The T2 increase was pronounced in the kidney, with [(13) C,(15) N2] urea giving T2 values of 6.3±1.3 s in the cortex and medulla, and 11±2 s in the renal pelvis. The measured T2 in the aorta was 1.3±0.3 s. [(13)C] urea showed shortened T2 values in the kidney of 0.23±0.03 s compared to 0.28±0.03 s measured in the aorta. The enhanced T2 of [(13)C,(15)N2] urea was utilized to generate large signal enhancement by SSFP acquisitions with flip angles approaching the fully refocused regime. Projection images at 0.94 mm in-plane resolution were acquired with both urea isotopes, with [(13)C,(15) N2] urea giving a greater than four-fold increase in signal-to-noise ratio over [(13)C] urea. PMID:24235273

  16. Effects of fasting on serial measurements of hyperpolarized [1-(13) C]pyruvate metabolism in tumors.

    PubMed

    Serrao, Eva M; Rodrigues, Tiago B; Gallagher, Ferdia A; Kettunen, Mikko I; Kennedy, Brett W C; Vowler, Sarah L; Burling, Keith A; Brindle, Kevin M

    2016-08-01

    Imaging of the metabolism of hyperpolarized [1-(13) C]pyruvate has shown considerable promise in preclinical studies in oncology, particularly for the assessment of early treatment response. The repeatability of measurements of (13) C label exchange between pyruvate and lactate was determined in a murine lymphoma model in fasted and non-fasted animals. The fasted state showed lower intra-individual variability, although the [1-(13) C]lactate/[1-(13) C]pyruvate signal ratio was significantly greater in fasted than in non-fasted mice, which may be explained by the higher tumor lactate concentrations in fasted animals. These results indicate that the fasted state may be preferable for the measurement of (13) C label exchange between pyruvate and lactate, as it reduces the variability and therefore should make it easier to detect the effects of therapy. © 2016 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd. PMID:27309986

  17. Effects of fasting on serial measurements of hyperpolarized [1‐13C]pyruvate metabolism in tumors

    PubMed Central

    Serrao, Eva M.; Rodrigues, Tiago B.; Gallagher, Ferdia A.; Kettunen, Mikko I.; Kennedy, Brett W. C.; Vowler, Sarah L.; Burling, Keith A.

    2016-01-01

    Imaging of the metabolism of hyperpolarized [1‐13C]pyruvate has shown considerable promise in preclinical studies in oncology, particularly for the assessment of early treatment response. The repeatability of measurements of 13C label exchange between pyruvate and lactate was determined in a murine lymphoma model in fasted and non‐fasted animals. The fasted state showed lower intra‐individual variability, although the [1‐13C]lactate/[1‐13C]pyruvate signal ratio was significantly greater in fasted than in non‐fasted mice, which may be explained by the higher tumor lactate concentrations in fasted animals. These results indicate that the fasted state may be preferable for the measurement of 13C label exchange between pyruvate and lactate, as it reduces the variability and therefore should make it easier to detect the effects of therapy. © 2016 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd. PMID:27309986

  18. Effect of light and brine shrimp on skeletal δ 13C in the Hawaiian coral Porites compressa: a tank experiment

    NASA Astrophysics Data System (ADS)

    Grottoli, Andréa G.

    2002-06-01

    Previous experimental fieldwork showed that coral skeletal δ 13C values decreased when solar intensity was reduced, and increased in the absence of zooplankton. However, actual seasonal changes in solar irradiance levels are typically less pronounced than those used in the previous experiment and the effect of increases in the consumption of zooplankton in the coral diet on skeletal δ 13C remains relatively unknown. In the present study, the effects of four different light and heterotrophy regimes on coral skeletal δ 13C values were measured. Porites compressa corals were grown in outdoor flow-through tanks under 112%, 100%, 75%, and 50% light conditions at the Hawaii Institute of Marine Biology, Hawaii. In addition, corals were fed either zero, low, medium, or high concentrations of brine shrimp. Decreases in light from 100% resulted in significant decreases in δ 13C that is most likely due to a corresponding decrease in photosynthesis. Increases in light to 112% also resulted in a decrease in δ 13C values. This latter response may be a consequence of photoinhibition. The overall curved response in δ 13C values was described by a significant quadratic function. Increases in brine shrimp concentrations resulted in increased skeletal δ 13C levels. This unexpected outcome appears to be attributable to enhanced nitrogen supply associated with the brine shrimp diet which led to increased zooxanthellae concentrations, increased photosynthesis rates, and thus increased δ 13C values. This result highlights the potential influence of nutrients from heterotrophically acquired carbon in maintaining the zooxanthellae-host symbiosis in balance. In addition, evidence is presented that suggests that coral skeletal growth and δ 13C are decoupled. These results increase our knowledge of how light and heterotrophy affects the δ 13C of coral skeletons.

  19. 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.

  20. Dissecting the Mechanisms of a Class of Chemical Glycosylation Using Primary 13C Kinetic Isotope Effects

    PubMed Central

    Huang, Min; Garrett, Graham E.; Birlirakis, Nicolas; Bohé, Luis

    2012-01-01

    Although arguably the most important reaction in glycoscience, chemical glycosylations are among the least well understood of organic chemical reactions resulting in an unnecessarily high degree of empiricism and a brake on rational development in this critical area. To address this problem primary 13C kinetic isotope effects now have been determined for the formation of β- and α-manno- and glucopyranosides by a natural abundance NMR method. In contrast to the common current assumption, for three of the four cases studied the experimental values concur with those computed for associative displacement of the intermediate covalent glycosyl trifluoromethanesulfonates. For the formation of the α-mannopyranosides the experimentally determined KIE differs significantly from that computed for an associative displacement, which is strongly suggestive of a dissociative mechanism that approaches the intermediacy of a glycosyl oxocarbenium ion. The application of comparable experiments to other glycosylation systems should shed further light on their glycosylation mechanisms and thus assist in the design of better reactions conditions with improved stereoselectivity. PMID:22824899

  1. Dissecting the mechanisms of a class of chemical glycosylation using primary 13C kinetic isotope effects

    NASA Astrophysics Data System (ADS)

    Huang, Min; Garrett, Graham E.; Birlirakis, Nicolas; Bohé, Luis; Pratt, Derek A.; Crich, David

    2012-08-01

    Although arguably the most important reaction in glycoscience, chemical glycosylations are among the least well understood of organic chemical reactions, resulting in an unnecessarily high degree of empiricism and a brake on rational development in this critical area. To address this problem, primary 13C kinetic isotope effects have now been determined for the formation of β- and α-manno- and glucopyranosides using a natural abundance NMR method. In contrast to the common current assumption, for three of the four cases studied the experimental and computed values are indicative of associative displacement of the intermediate covalent glycosyl trifluoromethanesulfonates. For the formation of the α-mannopyranosides, the experimentally determined KIE differs significantly from that computed for an associative displacement, which is strongly suggestive of a dissociative mechanism that approaches the intermediacy of a glycosyl oxocarbenium ion. The application of analogous experiments to other glycosylation systems should shed further light on their mechanisms and thus assist in the design of better reactions conditions with improved stereoselectivity.

  2. Effect of body size and body mass on δ 13 C and δ 15 N in coastal fishes and cephalopods

    NASA Astrophysics Data System (ADS)

    Vinagre, C.; Máguas, C.; Cabral, H. N.; Costa, M. J.

    2011-11-01

    Carbon and nitrogen isotopes have been widely used in the investigation of trophic relations, energy pathways, trophic levels and migrations, under the assumption that δ 13C is independent of body size and that variation in δ 15N occurs exclusively due to ontogenetic changes in diet and not body size increase per se. However, several studies have shown that these assumptions are uncertain. Data from food-webs containing an important number of species lack theoretical support on these assumptions because very few species have been tested for δ 13C and δ 15N variation in captivity. However, if sampling comprises a wide range of body sizes from various species, the variation of δ 13C and δ 15N with body size can be investigated. While correlation between body size and δ 13C and δ 15N can be due to ontogenetic diet shifts, stability in such values throughout the size spectrum can be considered an indication that δ 13C and δ 15N in muscle tissues of such species is independent of body size within that size range, and thus the basic assumptions can be applied in the interpretation of such food webs. The present study investigated the variation in muscle δ 13C and δ 15N with body size and body mass of coastal fishes and cephalopods. It was concluded that muscle δ 13C and δ 15N did not vary with body size or mass for all bony fishes with only one exception, the dragonet Callionymus lyra. Muscle δ 13C and δ 15N also did not vary with body size or mass in cartilaginous fishes and cephalopods, meaning that body size/mass per se have no effect on δ 13C or δ 15N, for most species analysed and within the size ranges sampled. The assumption that δ 13C is independent of body size and that variation in δ 15N is not affected by body size increase per se was upheld for most organisms and can be applied to the coastal food web studied taking into account that C. lyra is an exception.

  3. Land use Effects on Storage, Stability and Structure of Organic Carbon in Soil Density Fractions Revealed by 13C Natural Abundance and CPMAS 13C NMR

    NASA Astrophysics Data System (ADS)

    Flessa, H.; Helfrich, M.; John, B.; Yamashita, T.; Ludwig, B.

    2004-12-01

    The type of land use and soil cultivation are important factors controlling organic carbon storage (SOC) in soils and they can also influence the relative importance, the structure, and the stability of different SOC pools. The objectives of our study were: i) to quantify the SOC stocks in different density fractions (mineral-associated soil organic matter > 2 g cm-3 (Mineral-SOM), free particulate organic matter < 1.6 g cm-3 (free POM), light occluded particulate organic matter < 1.6 g cm-3 (occluded POM<1.6) and dense occluded particulate organic matter 1.6 to 2.0 g cm-3 (occluded POM1.6-2.0)) of silty soils under different land use (spruce forest, grassland, maize, wheat), ii) to determine the structure of these SOC fractions by CPMAS 13C NMR spectroscopy, and iii) to analyse the stability of these SOC fractions in the maize soil on the basis of the stable isotope composition of SOC. The SOC concentration in the A horizon increased in the order wheat (12.7 g kg-1) < maize (13.0 g kg-1) < grassland (24.5 g kg-1) < spruce (40.5 g kg-1). The major part (86-91%) of the SOC was associated with the heavy mineral fraction at the grassland, maize and wheat site. In the A horizon of the spruce soil, the particulate organic matter accounted for 52% of the total SOC content. The chemical structure of the soil organic matter (SOM) was influenced by litter quality, the intensity of litter decomposition and the related production and storage of microbially-derived substances. SOM of the acid forest soil was characterized by large amounts of POM with a high content of spruce litter-derived alkyl C. In the biologically more active grassland and maize soil, litter-derived POM was decomposed more rapidly and SOC stocks were dominated by mineral-associated SOM which contained greater proportions of aryl and carbonyl C. The cultivation of the grassland soil induced enhanced mineralization of POM and in particular of mineral-associated SOM. The faster SOC turnover was associated

  4. Effect of petroleum products on the decomposition of soil organic matter as assessed by 13C natural abundance

    NASA Astrophysics Data System (ADS)

    Stelmach, Wioleta; Szarlip, Paweł; Trembaczowski, Andrzej; Bieganowski, Andrzej

    2016-04-01

    Petroleum products are common contaminants in soils due to human activities. They are toxic for microorganisms and threat their functions, including decomposition of soil organic matter (SOM). The direct estimation of altered SOM decomposition - based on the CO2 emission - is impossible after oil contamination, because oil decomposition also contributes to the CO2 release. We used the natural differences in the isotopic signature (δ13C) of SOM and of oil products to partition the total CO2 for both sources and to analyze the suppression of SOM decomposition. The dynamics of 13C fractionation during the mineralization of gasoline and diesel was measured during 42 days. The 13C fractionation varied between -8.8‰ and +3.6‰ within the first 10 days, and stabilized thereafter at about -5.3‰ for gasoline and +3.2‰ for diesel. These 13C fractionations and δ13C values of CO2 emitted from the soil were used for correct partitioning of the total CO2. Contamination with gasoline reduced the CO2 efflux from SOM decomposition by a factor of 25 (from 151 to 6 mg C-CO2 kg‑1 soil during 42 days). The negative effect of diesel was much lower: the CO2 efflux from SOM was decreased by less than a factor of 2. The strong effect of gasoline versus diesel reflects the lower absorption of gasoline to mineral particles and the development of a thin film on water surfaces, leading to toxicity for microorganisms. We conclude that the small differences of 13C of SOM and of organic pollutants can be used to partition CO2 fluxes and analyze pollutant effects on SOM decomposition.

  5. 13C NMR of methane in an AlPO4-11 molecular sieve: Exchange effects and shielding anisotropy

    NASA Astrophysics Data System (ADS)

    Koskela, Tuomas; Ylihautala, Mika; Jokisaari, Jukka; Vaara, Juha

    1998-12-01

    13C NMR spectra of 13CH4 in an AlPO4-11 molecular sieve reveal exchange effects between adsorbed and nonadsorbed methane gas. An application of pulsed field gradients is introduced to decrease nonadsorbed and exchanging gas signals in order to extract the chemical shift anisotropy line shape of the adsorbed gas. The resulting 13C shielding anisotropy of methane is compared to existing value for methane in related SAPO-11 material. Less anisotropic shielding is observed in AlPO4-11, most likely due to the lack of charge-compensating cations.

  6. Effects of Induced Sputtering on delta (13) C and AR in the Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Kass, D. M.; Yung, Y. L.

    1996-09-01

    Given the possibility of life having developed on Mars, it becomes important to know the environment that it evolved in. There is geomorphological evidence that the ancient climate was wetter and warmer. This environment was presumably created by a dense CO_2 atmosphere, but it leaves the fundamental question of what happened to the atmosphere. One possibility is that the atmosphere escaped to space. The main method for removing CO_2 is indirect sputtering, a process where the solar wind accelerates O(+) to high energies and then has them impact the upper atmosphere, causing them to eject other particles (see Luhmann and Kozyra, { \\sl JGR}, 1991). The primary constraint on sputtering and its effect on the atmosphere is the isotopic signature. We have updated our Monte-Carlo model for sputtering (Kass and Yung, Science, 1995) with improved cross sections (from Johnson and Liu, Science, in press) and a more realistic handling of the dissociation of CO_2. Using our new model, we find that Mars could have lost as much as a bar of CO_2 in the last 3.5 Gyr. This is sufficient CO_2 to allow a warmer and wetter climate to have existed during the early part of Mars' history. While there are large errors associated with the calculation due to uncertainties in modeling the evolution of the Sun, our modeling indicates (unlike Luhmann et al., \\sl JRL, 1992) that sputtering can play a significant role in the evolution of the Martian atmosphere. Using our new model, we considered the effects of the sputtering on the delta (13) C and (36) Ar /(38) Ar ratio of the Martian atmosphere. Using a simple model combining the effects of sputtering, outgassing (taken from Jakosky et al., \\sl Icarus, 1994), carbonate formation (Stephens, Caltech Thesis, 1995) and polar reservoirs, we find that the model predicts values for the two isotopic systems in agreement with the current measurements for Mars. These two systems were chosen both because they are affected by relatively few processes

  7. /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.

  8. Quantitative analysis of deuterium using the isotopic effect on quaternary (13)C NMR chemical shifts.

    PubMed

    Darwish, Tamim A; Yepuri, Nageshwar Rao; Holden, Peter J; James, Michael

    2016-07-13

    Quantitative analysis of specifically deuterated compounds can be achieved by a number of conventional methods, such as mass spectroscopy, or by quantifying the residual (1)H NMR signals compared to signals from internal standards. However, site specific quantification using these methods becomes challenging when dealing with non-specifically or randomly deuterated compounds that are produced by metal catalyzed hydrothermal reactions in D2O, one of the most convenient deuteration methods. In this study, deuterium-induced NMR isotope shifts of quaternary (13)C resonances neighboring deuterated sites have been utilized to quantify the degree of isotope labeling of molecular sites in non-specifically deuterated molecules. By probing (13)C NMR signals while decoupling both proton and deuterium nuclei, it is possible to resolve (13)C resonances of the different isotopologues based on the isotopic shifts and the degree of deuteration of the carbon atoms. We demonstrate that in different isotopologues, the same quaternary carbon, neighboring partially deuterated carbon atoms, are affected to an equal extent by relaxation. Decoupling both nuclei ((1)H, (2)H) resolves closely separated quaternary (13)C signals of the different isotopologues, and allows their accurate integration and quantification under short relaxation delays (D1 = 1 s) and hence fast accumulative spectral acquisition. We have performed a number of approaches to quantify the deuterium content at different specific sites to demonstrate a convenient and generic analysis method for use in randomly deuterated molecules, or in cases of specifically deuterated molecules where back-exchange processes may take place during work up. PMID:27237841

  9. Effect of posture on 13C-urea breath test in partial gastrectomy patients

    PubMed Central

    Yin, Shu-Ming; Zhang, Fan; Shi, Dong-Mei; Xiang, Ping; Xiao, Li; Huang, Yi-Qin; Zhang, Gan-Sheng; Bao, Zhi-Jun

    2015-01-01

    AIM: To investigate whether posture affects the accuracy of 13C-urea breath test (13C-UBT) for Helicobacter pylori (H. pylori) detection in partial gastrectomy patients. METHODS: We studied 156 consecutive residual stomach patients, including 76 with H. pylori infection (infection group) and 80 without H. pylori infection (control group). H. pylori infection was confirmed if both the rapid urease test and histology were positive during gastroscopy. The two groups were divided into four subgroups according to patients’ posture during the 13C-UBT: subgroup A, sitting position; subgroup B, supine position; subgroup C, right lateral recumbent position; and subgroup D, left lateral recumbent position. Each subject underwent the following modified 13C-UBT: 75 mg of 13C-urea (powder) in 100 mL of citric acid solution was administered, and a mouth wash was performed immediately; breath samples were then collected at baseline and at 5-min intervals up to 30 min while the position was maintained. Seven breath samples were collected for each subject. The cutoff value was 2.0‰. RESULTS: The mean delta over baseline (DOB) values in the subgroups of the infection group were similar at 5 min (P > 0.05) and significantly higher than those in the corresponding control subgroups at all time points (P < 0.01). In the infection group, the mean DOB values in subgroup A were higher than those in other subgroups within 10 min and peaked at the 10-min point (12.4‰ ± 2.4‰). The values in subgroups B and C both reached their peaks at 15 min (B, 13.9‰ ± 1.5‰; C, 12.2‰ ± 1.7‰) and then decreased gradually until the 30-min point. In subgroup D, the value peaked at 20 min (14.7‰ ± 1.7‰). Significant differences were found between the values in subgroups D and B at both 25 min (t = 2.093, P = 0.043) and 30 min (t = 2.141, P = 0.039). At 30 min, the value in subgroup D was also significantly different from those in subgroups A and C (D vs C: t = 6.325, P = 0.000; D vs A: t

  10. Effects of temperature and substrate stoichiometry on microbial specific respiration rate, carbon use efficiency, and 13C fractionation

    NASA Astrophysics Data System (ADS)

    Min, K.; Lehmeier, C.; Sellers, M.; Chen, Y.; Ballantyne, F.; Billings, S. A.

    2013-12-01

    Microbial activity contributes up to 60% of soil respiration. However, uncertainty in microbial respiration with rising temperature has previously prevented better predictions of the amount and the source of carbon (C) respired from soil. Three key variables of microbial C economies are of particular interest for estimating microbially mediated C release with temperature: (1) specific respiration rate (SRR), which is microbial CO2 release per microbial biomass-C, (2) carbon use efficiency (CUE), which determines how much organic C consumed by microbes is transformed into biomass, and (3) changes in the δ13C of respired CO2 with temperature, which suggests the form of organic C mineralized and helps to partition soil respiration in plant- and microbe-derived CO2. However, it is difficult to obtain these variables in intact soils, due to confounding factors that influence the amount and δ13C of respired CO2. Here we present an experimental approach that allows us to grow an isolated microbial population on well-characterized organic substrates and directly measure SRR, CUE and δ13C of respired CO2. We explored the effect of temperature on those variables, and how it changes with C:N of the substrate provided. This is important given various substrates available for microbial decay, and the potential for changing microbial CUE with substrate C:N. This approach thus can help constrain potential microbial C loss with warming as soil organic substrates with varying C:N are decomposed. We hypothesized that (1) increased SRR and declined CUE with warming would be more evident at higher C:N, (2) apparent 13C fractionation between biomass and respired CO2 would decrease with temperature due to C limitation, and (3) this fractionation would be higher for high C:N. Pseudomonas fluorescens (a ubiquitous Gram-negative bacterium) was grown at 0.13 h-1 in a chemostat from 13 to 26.5°C. The concentration of cellobiose, the sole C source with constant δ13C, was adjusted to have

  11. Deuterium-induced isotope effects on the 13C chemical shifts of α-D-glucose pentaacetate.

    PubMed

    Pérez-Hernández, Nury; Álvarez-Cisneros, Celina; Cerda-García-Rojas, Carlos M; Morales-Ríos, Martha S; Joseph-Nathan, Pedro

    2013-03-01

    1,2,3,4,6-Penta-O-acetyl-α-D-glucopyranose and the corresponding [1-(2)H], [2-(2)H], [3-(2)H], [4-(2)H], [5-(2)H], and [6,6-(2)H(2)]-labeled compounds were prepared for measuring deuterium/hydrogen-induced effects on (13)C chemical shift (n)Δ (DHIECS) values. A conformational analysis of the nondeuterated compound was achieved using density functional theory (DFT) molecular models that allowed calculation of several structural properties as well as Boltzmann-averaged (13)C NMR chemical shifts by using the gauge-including atomic orbital method. It was found that the DFT-calculated C-H bond lengths correlate with (1)Δ DHIECS. PMID:23315885

  12. The effect of biochar amendment on the soil microbial community - PLFA analyses and 13C labeling results

    NASA Astrophysics Data System (ADS)

    Watzinger, A.; Feichtmair, S.; Rempt, F.; Anders, E.; Wimmer, B.; Kitzler, B.; Zechmeister-Boltenstern, S.; Horacek, M.; Zehetner, F.; Kloss, S.; Richoz, S.; Soja, G.

    2012-04-01

    The effects of biochar amendment on plant growth and on the chemical / physical soil characteristics are well explored but only few studies have investigated the impact on soil microorganisms. The response of the soil microbial community to biochar amendment was investigated by phospholipid fatty acid (PLFA) analysis in (i) a large scale pot experiment, (ii) a small scale pot experiment using 13C labeled biochar and (iii) an incubation study using 13C labeled biochar. In the large scale pot experiment, three different agricultural soils from Austria (Planosol, Cambisol, Chernozem) and four different types of biochar were investigated. In total, 25 treatments with 5 replicates each were set up and monitored over a year. The results from the pot experiments showed no significant influence of biochar amendment on the total microbial biomass in the first 100 days after biochar addition. However, discriminant analysis showed a distinction of biochar and control soils as well as a strong effect of the pyrolysis temperature on the microbial composition. The effect of biochar was dependent on the type of soil. In the Planosol, some PLFAs were affected positively, especially when adding biochar with a low pyrolysis temperature, in the first month. In the long term, microbial community composition altered. Growth of fungi and gram negative bacteria was enhanced. In the Chernozem, PLFAs from various microbial groups decreased in the long term. Variability in the incubation study was low. Consequently, many PLFAs were significantly affected by biochar amendment. Again, in the Planosol, gram negative bacteria, actinomycetes and, after 2 weeks, gram positive bacteria increased under biochar amendment whereas in the chernozem total microbial biomass and gram positive bacteria were negatively affected in the long term. The 13C labeling studies confirmed the low degradability of the biochar, i.e. no alteration of the content and the δ13C in the soil organic matter within 100 days

  13. Effects of a glucokinase activator on hepatic intermediary metabolism: study with 13C-isotopomer-based metabolomics

    PubMed Central

    Nissim, Itzhak; Horyn, Oksana; Nissim, Ilana; Daikhin, Yevgeny; Wehrli, Suzanne L.; Yudkoff, Marc; Matschinsky, Franz M.

    2013-01-01

    GKAs (glucokinase activators) are promising agents for the therapy of Type 2 diabetes, but little is known about their effects on hepatic intermediary metabolism. We monitored the fate of 13C-labelled glucose in both a liver perfusion system and isolated hepatocytes. MS and NMR spectroscopy were deployed to measure isotopic enrichment. The results demonstrate that the stimulation of glycolysis by GKA led to numerous changes in hepatic metabolism: (i) augmented flux through the TCA (tricarboxylic acid) cycle, as evidenced by greater incorporation of 13C into the cycle (anaplerosis) and increased generation of 13C isotopomers of citrate, glutamate and aspartate (cataplerosis); (ii) lowering of hepatic [Pi] and elevated [ATP], denoting greater phosphorylation potential and energy state; (iii) stimulation of glycogen synthesis from glucose, but inhibition of glycogen synthesis from 3-carbon precursors; (iv) increased synthesis of N-acetylglutamate and consequently augmented ureagenesis; (v) increased synthesis of glutamine, alanine, serine and glycine; and (vi) increased production and outflow of lactate. The present study provides a deeper insight into the hepatic actions of GKAs and uncovers the potential benefits and risks of GKA for treatment of diabetes. GKA improved hepatic bioenergetics, ureagenesis and glycogenesis, but decreased gluconeogenesis with a potential risk of lactic acidosis and fatty liver. PMID:22448977

  14. Effects of ingesting [13C]glucose early or late into cold exposure on substrate utilization

    PubMed Central

    Blondin, Denis P.; Péronnet, François

    2010-01-01

    One of the factors limiting the oxidation of exogenous glucose during cold exposure may be the delay in establishing a shivering steady state (∼60 min), reducing glucose uptake into skeletal muscle. Therefore, using indirect calorimetry and isotopic methodologies in non-cold-acclimatized men, the main purpose of this study was to determine whether ingesting glucose at a moment coinciding with the maximal shivering intensity could increase the utilization rate of the ingested glucose. 13C-enriched glucose was ingested (800 mg/min) from the onset (G0) or after 60 min (G60) of cold exposure when the thermogenic rate was stabilized to low-intensity shivering (∼2.5 times resting metabolic rate). For the same quantity of glucose ingested, the oxidation rate of exogenous glucose was 35% higher in G60 (159 ± 17 vs. 118 ± 17 mg/min in G0) between minutes 60 and 90. By the end of cold exposure, exogenous glucose oxidation was significantly greater in G0, reaching 231 ± 14 mg/min, ∼15% higher than the only rates previously reported. This considerably reduced the utilization of endogenous reserves over time and compared with the G60 condition. This study also demonstrates a fall in muscle glycogen utilization, when glucose was ingested from the onset of cold exposure (from ∼150 to ∼75 mg/min). Together, these findings indicate the importance of ingesting glucose immediately on exposure to a cold condition, relying on shivering thermogenesis and sustaining that consumption for as long as possible. This substrate not only provides an auxiliary fuel source for shivering thermogenesis, but, more importantly, preserves the limited endogenous glucose reserves. PMID:20651221

  15. Insight on RDX degradation mechanism by Rhodococcus strains using 13C and 15N kinetic isotope effects.

    PubMed

    Bernstein, Anat; Ronen, Zeev; Gelman, Faina

    2013-01-01

    The explosive Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is known to be degraded aerobically by various isolates of the Rhodococcus species, with denitration being the key step, mediated by Cytochrome P450. Our study aimed at gaining insight into the RDX degradation mechanism by Rhodococcus species and comparing isotope effects associated with RDX degradation by distinct Rhodococcus strains. For these purposes, enrichment in (13)C and (15)N isotopes throughout RDX denitration was studied for three distinct Rhodococcus strains, isolated from soil and groundwater in an RDX-contaminated site. The observable (15)N enrichment throughout the reaction, together with minor (13)C enrichment, suggests that N-N bond cleavage is likely to be the key rate-limiting step in the reaction. The similarity in the kinetic (15)N isotope effect between the three tested strains suggests that either isotope-masking effects are negligible, or are of a similar extent for all tested strains. The lack of variability in the kinetic (15)N isotope effect allows the interpretation of environmental studies with greater confidence. PMID:23215036

  16. Combined Effects of Ocean Acidification and Light or Nitrogen Availabilities on 13C Fractionation in Marine Dinoflagellates.

    PubMed

    Hoins, Mirja; Eberlein, Tim; Groβmann, Christian H; Brandenburg, Karen; Reichart, Gert-Jan; Rost, Björn; Sluijs, Appy; Van de Waal, Dedmer B

    2016-01-01

    Along with increasing oceanic CO2 concentrations, enhanced stratification constrains phytoplankton to shallower upper mixed layers with altered light regimes and nutrient concentrations. Here, we investigate the effects of elevated pCO2 in combination with light or nitrogen-limitation on 13C fractionation (εp) in four dinoflagellate species. We cultured Gonyaulax spinifera and Protoceratium reticulatum in dilute batches under low-light ('LL') and high-light ('HL') conditions, and grew Alexandrium fundyense and Scrippsiella trochoidea in nitrogen-limited continuous cultures ('LN') and nitrogen-replete batches ('HN'). The observed CO2-dependency of εp remained unaffected by the availability of light for both G. spinifera and P. reticulatum, though at HL εp was consistently lower by about 2.7‰ over the tested CO2 range for P. reticulatum. This may reflect increased uptake of (13C-enriched) bicarbonate fueled by increased ATP production under HL conditions. The observed CO2-dependency of εp disappeared under LN conditions in both A. fundyense and S. trochoidea. The generally higher εp under LN may be associated with lower organic carbon production rates and/or higher ATP:NADPH ratios. CO2-dependent εp under non-limiting conditions has been observed in several dinoflagellate species, showing potential for a new CO2-proxy. Our results however demonstrate that light- and nitrogen-limitation also affect εp, thereby illustrating the need to carefully consider prevailing environmental conditions. PMID:27153107

  17. sup 13 C and sup 18 O isotopic disequilibrium in biological carbonates: II. In vitro simulation of kinetic isotope effects

    SciTech Connect

    McConnaughey, T. )

    1989-01-01

    Biological carbonates are built largely from CO{sub 2}, which diffuses across the skeletogenic membrane and reacts to form HCO{sub 3}{sup {minus}}. Kinetic discrimination against the heavy isotopes {sup 18}O and {sup 13}C during CO{sub 2} hydration and hydroxylation apparently causes most of the isotopic disequilibrium observed in biological carbonates. These kinetic isotope effects are expressed when the extracytosolic calcifying solution is thin and alkaline, and HCO{sub 3}{sup {minus}} precipitates fairly rapidly as CaCO{sub 3}. In vitro simulation of the calcifying environment produced heavy isotope depletions qualitatively similar to, but somewhat more extreme than, those seen in biological carbonates. Isotopic equilibration during biological calcification occurs through CO{sub 2} exchange across the calcifying membrane and by admixture ambient waters (containing HCO{sub 3}{sup {minus}}) into the calcifying fluids. Both mechanisms tend to produce linear correlations between skeletal {delta}{sup 13}C and {delta}{sup 18}O.

  18. Combined Effects of Ocean Acidification and Light or Nitrogen Availabilities on 13C Fractionation in Marine Dinoflagellates

    PubMed Central

    Hoins, Mirja; Eberlein, Tim; Groβmann, Christian H.; Brandenburg, Karen; Reichart, Gert-Jan; Rost, Björn; Sluijs, Appy; Van de Waal, Dedmer B.

    2016-01-01

    Along with increasing oceanic CO2 concentrations, enhanced stratification constrains phytoplankton to shallower upper mixed layers with altered light regimes and nutrient concentrations. Here, we investigate the effects of elevated pCO2 in combination with light or nitrogen-limitation on 13C fractionation (εp) in four dinoflagellate species. We cultured Gonyaulax spinifera and Protoceratium reticulatum in dilute batches under low-light (‘LL’) and high-light (‘HL’) conditions, and grew Alexandrium fundyense and Scrippsiella trochoidea in nitrogen-limited continuous cultures (‘LN’) and nitrogen-replete batches (‘HN’). The observed CO2-dependency of εp remained unaffected by the availability of light for both G. spinifera and P. reticulatum, though at HL εp was consistently lower by about 2.7‰ over the tested CO2 range for P. reticulatum. This may reflect increased uptake of (13C-enriched) bicarbonate fueled by increased ATP production under HL conditions. The observed CO2-dependency of εp disappeared under LN conditions in both A. fundyense and S. trochoidea. The generally higher εp under LN may be associated with lower organic carbon production rates and/or higher ATP:NADPH ratios. CO2-dependent εp under non-limiting conditions has been observed in several dinoflagellate species, showing potential for a new CO2-proxy. Our results however demonstrate that light- and nitrogen-limitation also affect εp, thereby illustrating the need to carefully consider prevailing environmental conditions. PMID:27153107

  19. A (13)C NMR analysis of the effects of electron radiation on graphite/polyetherimide composites

    NASA Technical Reports Server (NTRS)

    Ferguson, Milton W.

    1989-01-01

    Initial investigations have been made into the use of high resolution nuclear magnetic resonance (NMR) for the characterization of radiation effects in graphite and Kevlar fibers, polymers, and the fiber/matrix interface in graphite/polyetherimide composites. Sample preparation techniques were refined. Essential equipment has been procured. A new NMR probe was constructed to increase the proton signal-to-noise ratio. Problem areas have been identified and plans developed to resolve them.

  20. The effect of feeding on CO2 production and energy expenditure in ponies measured by indirect calorimetry and the 13C-bicarbonate technique.

    PubMed

    Jensen, R B; Kyrstein, T D; Junghans, P; Tauson, A H

    2015-11-01

    Energy expenditure (EE) can be estimated based on respiratory gas exchange measurements, traditionally done in respiration chambers by indirect calorimetry (IC). However, the (13)C-bicarbonate technique ((13)C-BT) might be an alternative minimal invasive method for estimation of CO(2) production and EE in the field. In this study, four Shetland ponies were used to explore the effect of feeding on CO(2) production and EE measured simultaneously by IC and (13)C-BT. The ponies were individually housed in respiration chambers and received either a single oral or intravenous (IV) bolus dose of (13)C-labelled sodium bicarbonate (NaH(13)CO(3)). The ponies were fed haylage 3 h before (T(-3)), simultaneously with (T(0)) or 3 h after (T(+3)) administration of (13)C-bicarbonate. The CO(2) produced and O(2) consumed by the ponies were measured for 6 h with both administration routes of (13)C-bicarbonate at the three different feeding times. Feeding time affected the CO(2) production (P<0.001) and O(2) consumption (P<0.001), but not the respiratory quotient (RQ) measured by IC. The recovery factor (RF) of (13)C in breath CO(2) was affected by feeding time (P<0.01) and three different RF were used in the calculation of CO(2) production measured by 13C-BT. An average RQ was used for the calculations of EE. There was no difference between IC and (13)C-BT for estimation of CO(2) production. An effect of feeding time (P<0.001) on the estimated EE was found, with higher EE when feed was offered (T(0) and T(+3)) compared with when no feed was available (T -3) during measurements. In conclusion, this study showed that feeding time affects the RF and measurements of CO(2) production and EE. This should be considered when the (13)C-BT is used in the field. IV administration of (13)C-bicarbonate is recommended in future studies with horses to avoid complex (13)C enrichment-time curves with maxima and shoulders as observed in several experiments with oral administration of (13)C

  1. Evaporation induced 18O and 13C enrichment in lake systems: A global perspective on hydrologic balance effects

    NASA Astrophysics Data System (ADS)

    Horton, Travis W.; Defliese, William F.; Tripati, Aradhna K.; Oze, Christopher

    2016-01-01

    Growing pressure on sustainable water resource allocation in the context of global development and rapid environmental change demands rigorous knowledge of how regional water cycles change through time. One of the most attractive and widely utilized approaches for gaining this knowledge is the analysis of lake carbonate stable isotopic compositions. However, endogenic carbonate archives are sensitive to a variety of natural processes and conditions leaving isotopic datasets largely underdetermined. As a consequence, isotopic researchers are often required to assume values for multiple parameters, including temperature of carbonate formation or lake water δ18O, in order to interpret changes in hydrologic conditions. Here, we review and analyze a global compilation of 57 lacustrine dual carbon and oxygen stable isotope records with a topical focus on the effects of shifting hydrologic balance on endogenic carbonate isotopic compositions. Through integration of multiple large datasets we show that lake carbonate δ18O values and the lake waters from which they are derived are often shifted by >+10‰ relative to source waters discharging into the lake. The global pattern of δ18O and δ13C covariation observed in >70% of the records studied and in several evaporation experiments demonstrates that isotopic fractionations associated with lake water evaporation cause the heavy carbon and oxygen isotope enrichments observed in most lakes and lake carbonate records. Modeled endogenic calcite compositions in isotopic equilibrium with lake source waters further demonstrate that evaporation effects can be extreme even in lake records where δ18O and δ13C covariation is absent. Aridisol pedogenic carbonates show similar isotopic responses to evaporation, and the relevance of evaporative modification to paleoclimatic and paleotopographic research using endogenic carbonate proxies are discussed. Recent advances in stable isotope research techniques present unprecedented

  2. Acute porcine renal metabolic effect of endogastric soft drink administration assessed with hyperpolarized [1‐13c]pyruvate

    PubMed Central

    Hansen, Esben Søvsø Szocska; Kjærgaard, Uffe; Bertelsen, Lotte Bonde; Ringgaard, Steffen; Stødkilde‐Jørgensen, Hans

    2015-01-01

    Purpose Our aim was to determine the quantitative reproducibility of metabolic breakdown products in the kidney following intravenous injection of hyperpolarized [1‐13C]pyruvate and secondly to investigate the metabolic effect on the pyruvate metabolism of oral sucrose load using dissolution dynamic nuclear polarization. By this technique, metabolic alterations in several different metabolic related diseases and their metabolic treatment responses can be accessed. Methods In four healthy pigs the lactate‐to‐pyruvate, alanine‐to‐pyruvate and bicarbonate‐to‐pyruvate ratio was measured following administration of regular cola and consecutive injections of hyperpolarized [1‐13C]pyruvate four times within an hour. Results The overall lactate‐to‐pyruvate metabolic profile changed significantly over one hour following an acute sucrose load leading to a significant rise in blood glucose. Conclusion The reproducibility of hyperpolarized magnetic resonance spectroscopy in the healthy pig kidney demonstrated a repeatability of more than 94% for all metabolites and, furthermore, that the pyruvate to lactate conversion and the blood glucose level is elevated following endogastric sucrose administration. Magn Reson Med 74:558–563, 2015. © 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‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made. PMID:26014387

  3. 13C and 199Hg nuclear magnetic resonance spectroscopic study of alkenemercurinium ions: Effect of methyl substituents on 199Hg chemical shifts

    PubMed Central

    Olah, George A.; Garcia-Luna, Armando

    1980-01-01

    The long-lived ethylene, cyclohexene, and norbornenemercurinium ions prepared in superacidic, low-nucleophilic media have been studied by 13C and 199Hg NMR spectroscopy. The norbornenemercurinium ion shows temperature-dependent 13C and 199Hg NMR spectra, consistent with equilibration via rapid hydride and Wagner-Meerwin shifts. The 199Hg NMR shifts of a series of alkylmercury bromides were also obtained in order to elucidate the effect of methyl substituents on 199Hg NMR chemical shifts. PMID:16592870

  4. Investigation of the enzymatic mechanism of yeast orotidine-5'-monophosphate decarboxylase using sup 13 C kinetic isotope effects

    SciTech Connect

    Smiley, J.A.; Bell, J.B.; Jones, M.E. ); Paneth, P.; O'Leary, M.H. )

    1991-06-25

    Orotidine-5'-monophosphate decarboxylase (ODCase) from Saccharomyces cerevisiae displays an observed {sup 13}C kinetic isotope effect of 1.0247 {plus minus} 0.0008 at 25 C, pH 6.8. The observed isotope effect is sensitive to changes in the reaction medium, such as pH, temperature, or glycerol content. The value of 1.0494 {plus minus} 0.0006 measured at pH 4.0, 25 C, is not altered significantly by temperature or glycerol, and thus the intrinsic isotope effect for the reaction is apparently being observed under these conditions and decarboxylation is almost entirely rate-determining. These data require a catalytic mechanism with freely reversible binding and one in which a very limited contribution to the overall rate is made by chemical steps preceding decarboxylation; the zwitterion mechanism of Beak and Siegel, which involves only protonation of the pyrimidine ring, is such a mechanism. With use of an intrinsic isotope effect of 1.05, a partitioning factor of less than unity is calculated for ODCase at pH 6.0, 25 C. A quantitative kinetic analysis using this result excludes the possibility of an enzymatic mechanism involving covalent attachment of an enzyme nucleophile to C-5 of the pyrimidine ring. These data fit a kinetic model in which an enzyme proton necessary for catalysis is titrated at high pH, thus providing evidence for the catalytic mechanism of Beak and Siegal.

  5. Effects of Air Pollutants on the Composition of Stable Carbon Isotopes, δ13C, of Leaves and Wood, and on Leaf Injury 1

    PubMed Central

    Martin, Bjorn; Bytnerowicz, Andrzej; Thorstenson, Yvonne R.

    1988-01-01

    Air pollutants are known to cause visible leaf injury as well as impairment of photosynthetic CO2 fixation. Here we evaluate whether the effects on photosynthesis are large enough to cause changes in the relative composition of stable carbon isotopes, δ13C, of plant tissue samples, and, if so, how the changes relate to visual leaf injury. For that purpose, several woody and herbaceous plant species were exposed to SO2 + O3 and SO2 + O3 + NO2 for one month (8 hours per day, 5 days per week). At the end of the fumigations, the plants were evaluated for visual leaf lesions, and δ13C of leaf tissue was determined. Woody plants generally showed less visual leaf injury and smaller effects on δ13C of pollutant exposure than did herbaceous plants. If δ13C was affected by pollutants, it became, with few exceptions, less negative. The data from the fumigation experiments were consistent with δ13C analyses of whole wood of annual growth rings from two conifer tree species, Pseudotsuga menziesii and Pinus strobus. These trees had been exposed until 1977 to exhaust gases from a gas plant at Lacq, France. Wood of both conifer species formed in the polluted air of 1972 to 1976 had less negative δ13C values than had wood formed in the much cleaner air in 1982 to 1986. No similar, time-dependent differences in δ13C of wood were observed in trees which had been continuously growing in clean air. Our δ13C data from both relatively short-term artificial exposures and long-term natural exposure are consistent with greater stomatal limitation of photosynthesis in polluted air than in clean air. PMID:16666270

  6. [COMPARATIVE EVALUATION OF THE EFFECTIVENESS OF THE USE OF 13C-LABELED MIXED TRIGLYCERIDE AND 13C-STARCH BREATH TESTS IN PATIENTS WITH CHRONIC PANCREATITIS AFTER CHOLECYSTECTOMY].

    PubMed

    Sirchak, Ye S

    2015-01-01

    The results of a comprehensive study of 96 patients after cholecystectomy are provided. The higher sensitivity and informativeness of the 13C-labeled mixed triglyceride breath .test compared with 13C-starch breath test for determining functional pancreatic insufficiency in patients after cholecystectomy in early stages of its formation was set. PMID:27491156

  7. The Longitudinal Effects of Impoundment on Periphyton Biomass and δ13C in a Northern Michigan Stream

    NASA Astrophysics Data System (ADS)

    Mulder, J. D.; Rebertus, A.

    2005-05-01

    Autochthonous production is often altered upstream of small impoundments, such as beaver dams, but few studies have examined how such impoundments affect downstream production. A better understanding is needed of how production and organic matter dynamics are affected by natural impoundments. In this study we examined the effects of a beaver impoundment on periphyton biomass and δ13C in a low-order, forested stream. Periphyton samples were cultured at locations every 200 meters starting at a beaver dam and continuing 800 meters downstream. Samples were analyzed for biomass and carbon and nitrogen stable isotopes. By using additions of macrophyte biomass, the system was manipulated in an attempt to alter natural production levels and isotopic signatures of periphyton. Statistically significant effects were not detected; however, the results did indicate trends. Production decreased with distance from the impoundment, and detrital additions increased production. The amount of increase, however, was inversely related to distance from the impoundment. A shift in isotopic ratios of periphyton was detected, suggesting effects on the inorganic carbon pool, and perhaps shortening of carbon turnover lengths.

  8. Effects of Ontogeny on δ13C of Plant- and Soil-Respired CO2 and on Respiratory Carbon Fractionation in C3 Herbaceous Species.

    PubMed

    Salmon, Yann; Buchmann, Nina; Barnard, Romain L

    2016-01-01

    Knowledge gaps regarding potential ontogeny and plant species identity effects on carbon isotope fractionation might lead to misinterpretations of carbon isotope composition (δ13C) of respired CO2, a widely-used integrator of environmental conditions. In monospecific mesocosms grown under controlled conditions, the δ13C of C pools and fluxes and leaf ecophysiological parameters of seven herbaceous species belonging to three functional groups (crops, forage grasses and legumes) were investigated at three ontogenetic stages of their vegetative cycle (young foliage, maximum growth rate, early senescence). Ontogeny-related changes in δ13C of leaf- and soil-respired CO2 and 13C/12C fractionation in respiration (ΔR) were species-dependent and up to 7‰, a magnitude similar to that commonly measured in response to environmental factors. At plant and soil levels, changes in δ13C of respired CO2 and ΔR with ontogeny were related to changes in plant physiological status, likely through ontogeny-driven changes in the C sink to source strength ratio in the aboveground plant compartment. Our data further showed that lower ΔR values (i.e. respired CO2 relatively less depleted in 13C) were observed with decreasing net assimilation. Our findings highlight the importance of accounting for ontogenetic stage and plant community composition in ecological studies using stable carbon isotopes. PMID:27010947

  9. Effects of Ontogeny on δ13C of Plant- and Soil-Respired CO2 and on Respiratory Carbon Fractionation in C3 Herbaceous Species

    PubMed Central

    Salmon, Yann; Buchmann, Nina; Barnard, Romain L.

    2016-01-01

    Knowledge gaps regarding potential ontogeny and plant species identity effects on carbon isotope fractionation might lead to misinterpretations of carbon isotope composition (δ13C) of respired CO2, a widely-used integrator of environmental conditions. In monospecific mesocosms grown under controlled conditions, the δ13C of C pools and fluxes and leaf ecophysiological parameters of seven herbaceous species belonging to three functional groups (crops, forage grasses and legumes) were investigated at three ontogenetic stages of their vegetative cycle (young foliage, maximum growth rate, early senescence). Ontogeny-related changes in δ13C of leaf- and soil-respired CO2 and 13C/12C fractionation in respiration (ΔR) were species-dependent and up to 7‰, a magnitude similar to that commonly measured in response to environmental factors. At plant and soil levels, changes in δ13C of respired CO2 and ΔR with ontogeny were related to changes in plant physiological status, likely through ontogeny-driven changes in the C sink to source strength ratio in the aboveground plant compartment. Our data further showed that lower ΔR values (i.e. respired CO2 relatively less depleted in 13C) were observed with decreasing net assimilation. Our findings highlight the importance of accounting for ontogenetic stage and plant community composition in ecological studies using stable carbon isotopes. PMID:27010947

  10. Evaluation of Hyperpolarized [1-13C]-Pyruvate by Magnetic Resonance to Detect Ionizing Radiation Effects in Real Time

    PubMed Central

    Sandulache, Vlad C.; Chen, Yunyun; Lee, Jaehyuk; Rubinstein, Ashley; Ramirez, Marc S.; Skinner, Heath D.; Walker, Christopher M.; Williams, Michelle D.; Tailor, Ramesh; Court, Laurence E.; Bankson, James A.; Lai, Stephen Y.

    2014-01-01

    Ionizing radiation (IR) cytotoxicity is primarily mediated through reactive oxygen species (ROS). Since tumor cells neutralize ROS by utilizing reducing equivalents, we hypothesized that measurements of reducing potential using real-time hyperpolarized (HP) magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) can serve as a surrogate marker of IR induced ROS. This hypothesis was tested in a pre-clinical model of anaplastic thyroid carcinoma (ATC), an aggressive head and neck malignancy. Human ATC cell lines were utilized to test IR effects on ROS and reducing potential in vitro and [1-13C] pyruvate HP-MRS/MRSI imaging of ATC orthotopic xenografts was used to study in vivo effects of IR. IR increased ATC intra-cellular ROS levels resulting in a corresponding decrease in reducing equivalent levels. Exogenous manipulation of cellular ROS and reducing equivalent levels altered ATC radiosensitivity in a predictable manner. Irradiation of ATC xenografts resulted in an acute drop in reducing potential measured using HP-MRS, reflecting the shunting of reducing equivalents towards ROS neutralization. Residual tumor tissue post irradiation demonstrated heterogeneous viability. We have adapted HP-MRS/MRSI to non-invasively measure IR mediated changes in tumor reducing potential in real time. Continued development of this technology could facilitate the development of an adaptive clinical algorithm based on real-time adjustments in IR dose and dose mapping. PMID:24475215

  11. Biomarkers of Exposure and Effect in Human Lymphoblastoid TK6 Cells Following [13C2]-Acetaldehyde Exposure

    PubMed Central

    Swenberg, James A.

    2013-01-01

    The dose-response relationship for biomarkers of exposure (N2-ethylidene-dG adducts) and effect (cell survival and micronucleus formation) was determined across 4.5 orders of magnitude (50nM–2mM) using [13C2]-acetaldehyde exposures to human lymphoblastoid TK6 cells for 12h. There was a clear increase in exogenous N 2-ethylidene-dG formation at exposure concentrations ≥ 1µM, whereas the endogenous adducts remained nearly constant across all exposure concentrations, with an average of 3.0 adducts/107 dG. Exogenous adducts were lower than endogenous adducts at concentrations ≤ 10µM and were greater than endogenous adducts at concentrations ≥ 250µM. When the endogenous and exogenous adducts were summed together, statistically significant increases in total adduct formation over the endogenous background occurred at 50µM. Cell survival and micronucleus formation were monitored across the exposure range and statistically significant decreases in cell survival and increases in micronucleus formation occurred at ≥ 1000µM. This research supports the hypothesis that endogenously produced reactive species, including acetaldehyde, are always present and constitute the majority of the observed biological effects following very low exposures to exogenous acetaldehyde. These data can replace default assumptions of linear extrapolation to very low doses of exogenous acetaldehyde for risk prediction. PMID:23425604

  12. Halogen effect on structure and 13C NMR chemical shift of 3,6-disubstituted-N-alkyl carbazoles.

    PubMed

    Radula-Janik, Klaudia; Kupka, Teobald; Ejsmont, Krzysztof; Daszkiewicz, Zdzislaw; Sauer, Stephan P A

    2013-10-01

    Structures of selected 3,6-dihalogeno-N-alkyl carbazole derivatives were calculated at the B3LYP/6-311++G(3df,2pd) level of theory, and their (13) C nuclear magnetic resonance (NMR) isotropic shieldings were predicted using density functional theory (DFT). The model compounds contained 9H, N-methyl and N-ethyl derivatives. The relativistic effect of Br and I atoms on nuclear shieldings was modeled using the spin-orbit zeroth-order regular approximation (ZORA) method. Significant heavy atom shielding effects for the carbon atom directly bonded with Br and I were observed (~-10 and ~-30 ppm while the other carbon shifts were practically unaffected). The decreasing electronegativity of the halogen substituent (F, Cl, Br, and I) was reflected in both nonrelativistic and relativistic NMR results as decreased values of chemical shifts of carbon atoms attached to halogen (C3 and C6) leading to a strong sensitivity to halogen atom type at 3 and 6 positions of the carbazole ring. The predicted NMR data correctly reproduce the available experimental data for unsubstituted N-alkylcarbazoles. PMID:23922027

  13. 12C/13C kinetic isotope effects in the reactions of CH4 with OH and Cl

    NASA Astrophysics Data System (ADS)

    Gupta, Mohan L.; McGrath, M. P.; Cicerone, R. J.; Rowland, F. S.; Wolfsberg, M.

    1997-11-01

    In qualitative agreement with previous MP2 level calculations of the 12C/13C kinetic isotope effects (KIEs) for H-abstraction of CH4 by OH and Cl, higher level calculations yield KIEs at 300 K that differ from the corresponding experimental values, but in different directions. At QCISD(T)/6-311+G(2df,p), the theoretical KIE for CH4+Cl is 32‰ less than the measured value, while for CH4+OH, the theoretical KIE is greater than the measured value, but only by 5‰. Noticeable differences in atmospheric model simulation studies can occur if the measured KIEs are replaced by the analogous theoretical values. For example, the effect of carbon isotopic fractionation from the CH4 + Cl reaction on stratospheric δ13CH4 will be significantly lower than that obtained by Bergamaschi et al. [1996]. It is suggested, for the CH4+OH reaction and especially for the CH4+Cl reaction, that additional KIE measurements are needed.

  14. Effect of Crop cultivation after Mediterranean maquis on soil carbon stock, δ13C spatial distribution and root turnover

    NASA Astrophysics Data System (ADS)

    Novara, Agata; Gristina, Luciano; Santoro, Antonino; La Mantia, Tommaso

    2013-04-01

    The aim of this work was investigate the effect of land use change on soil organic carbon (SOC) stock and distribution in a Mediterranean succession. A succession composed by natural vegetation, cactus pear crop and olive grove, was selected in Sicily. The land use change from mediterranena maquis (C3 plant) to cactus pear (C4 plant) lead to a SOC decrease of 65% after 28 years of cultivation, and a further decrease of 14% after 7 years since the land use from cactus pear to olive grove (C3 plant). Considering this exchange and decrease as well as the periods after the land use changes we calculated the mean residence time (MRT) of soil C of different age. The MRT of C under Mediterranean maquis was about 142 years, but was 10 years under cactus pear. Total SOC and δ13 C were measured along the soil profile (0-75cm) and in the intra-rows in order to evaluate the distribution of new and old carbon derived and the growth of roots. After measuring of weight of cactus pear root, an approach was developed to estimate the turnover of root biomass. Knowledge of root turnover and carbon input are important to evaluate the correlation between carbon input accumulation and SOC stock in order to study the ability of C sink of soils with different use and managements.

  15. Effect of photosynthesis on the abundance of 18O13C16O in atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Hofmann, Magdalena E. G.; Pons, Thijs L.; Ziegler, Martin; Lourens, Lucas J.; Röckmann, Thomas

    2016-04-01

    The abundance of the isotopologue 18O13C16O (Δ47) in atmospheric air is a promising new tracer for the atmospheric carbon cycle (Eiler and Schauble, 2004; Affek and Eiler, 2006; Affek et al., 2007). The large gross fluxes in CO2 between the atmosphere and biosphere are supposed to play a major role in controlling its abundance. Eiler and Schauble (2004) set up a box model describing the effect of air-leaf interaction on the abundance of 18O13C16O in atmospheric air. The main assumption is that the exchange between CO2 and water within the mesophyll cells will imprint a Δ47 value on the back-diffusing CO2 that reflects the leaf temperature. Additionally, kinetic effects due to CO2 diffusion into and out of the stomata are thought to play a role. We investigated the effect of photosynthesis on the residual CO2 under controlled conditions using a leaf chamber set-up to quantitatively test the model assumptions suggested by Eiler and Schauble (2004). We studied the effect of photosynthesis on the residual CO2 using two C3 and one C4 plant species: (i) sunflower (Helianthus annuus), a C3 species with a high leaf conductance for CO2 diffusion, (ii) ivy (Hedera hibernica), a C3 species with a low conductance, and (iii), maize (Zea mays), a species with the C4 photosynthetic pathway. We also investigated the effect of different light intensities (photosynthetic photon flux density of 200, 700 and 1800 μmol m2s‑1), and thus, photosynthetic rate in sunflower and maize. A leaf was mounted in a cuvette with a transparent window and an adjustable light source. The air inside was thoroughly mixed, making the composition of the outgoing air equal to the air inside. A gas-mixing unit was attached at the entrance of the cuvette that mixed air with a high concentration of scrambled CO2 with a Δ47 value of 0 to 0.1‰ with CO2 free air to set the CO2 concentration of ingoing air at 500 ppm. The flow rate through the cuvette was adjusted to the photosynthetic activity of the

  16. Routing of Fatty Acids from Fresh Grass to Milk Restricts the Validation of Feeding Information Obtained by Measuring (13)C in Milk.

    PubMed

    Auerswald, Karl; Schäufele, Rudi; Bellof, Gerhard

    2015-12-01

    Dairy production systems vary widely in their feeding and livestock-keeping regimens. Both are well-known to affect milk quality and consumer perceptions. Stable isotope analysis has been suggested as an easy-to-apply tool to validate a claimed feeding regimen. Although it is unambiguous that feeding influences the carbon isotope composition (δ(13)C) in milk, it is not clear whether a reported feeding regimen can be verified by measuring δ(13)C in milk without sampling and analyzing the feed. We obtained 671 milk samples from 40 farms distributed over Central Europe to measure δ(13)C and fatty acid composition. Feeding protocols by the farmers in combination with a model based on δ(13)C feed values from the literature were used to predict δ(13)C in feed and subsequently in milk. The model considered dietary contributions of C3 and C4 plants, contribution of concentrates, altitude, seasonal variation in (12/13)CO2, Suess's effect, and diet-milk discrimination. Predicted and measured δ(13)C in milk correlated closely (r(2) = 0.93). Analyzing milk for δ(13)C allowed validation of a reported C4 component with an error of <8% in 95% of all cases. This included the error of the method (measurement and prediction) and the error of the feeding information. However, the error was not random but varied seasonally and correlated with the seasonal variation in long-chain fatty acids. This indicated a bypass of long-chain fatty acids from fresh grass to milk. PMID:26567466

  17. Magnetic isotope effects in the photolysis of dibenzyl ketone on porous silica. /sup 13/C and /sup 17/O enrichments

    SciTech Connect

    Turro, N.J.; Cheng, C.C.; Wan, P.; Chung, C.; Mahler, W.

    1985-04-25

    The photolysis of dibenzyl ketone (DBK) on porous silica has been investigated. Both /sup 13/C and /sup 17/O isotopic enrichment in the ketone remaining after partial photolysis is demonstrated. The efficiency of /sup 13/C enrichment was found to be relatively insensitive to the average pore diameter of the silica host, to the percent coverage by DBK, and to the application of an external magnetic field. A significant dependence of /sup 13/C enrichment with temperature, with a maximum in the enrichment-temperature profile, was observed. The results are interpreted in terms of the competition between pathways available to the triplet C/sub 6/H/sub 5/CH/sub 2/COCH/sub 2/C/sub 6/H/sub 5/ radical pair produced by photolysis of DBK.

  18. Effect of Dipolar Cross Correlation on Model-Free Motional Parameters Obtained from 13C Relaxation in AX 2 Systems

    NASA Astrophysics Data System (ADS)

    Zhu, L. Y.; Kemple, M. D.; Landy, S. B.; Buckley, P.

    The importance of dipolar cross correlation in 13C relaxation studies of molecular motion in AX 2 spin systems (A = 13C, X = 1H) was examined. Several different models for the internal motion, including two restricted-diffusion, and two-site jump models, the Kinosita model [K. Kinosita, Jr., S. Kawato, and A. Ikegami, Biophys. J.20, 289 (1977)], and an axially symmetric model, were applied through the Lipari and Szabo [ J. Am. Chem. Soc.104, 4546 (1982)] formalism to calculate errors in 13C T1, obtained from inversion-recovery measurements under proton saturation, and NOE when dipolar cross correlation is neglected. Motional parameters in the Lipari and Szabo formalism, τ m, S2, and τ e, were then determined from T1 and NOE (including the errors) and compared with parameters initially used to simulate the relaxation data. The resulting differences in the motional parameters, while model dependent, were generally small for plausible motions. At larger S2 values (≥ 0.6), the errors in both τ m and S2 were <5%. Errors in τ e increased with S2 but were usually less than 10%. Larger errors in the parameters were found for an axially symmetric model, but with τ m fixed even those were >5% only for the τ m = 1 ns, τ e = 10 ps case. Furthermore, it was observed that deviations in a given motional parameter were mostly of the same sign, which allows bounds to be set on experimentally derived parameters. Relaxation data for the peptide melittin synthesized with gly enriched with 13C at the backbone cu position and with lys enriched with 13C in the side chain were examined in light of the results of the simulations. All in all, it appears that neglect of dipolar cross correlation in 13C T1 (With proton saturation) and NOE measurements in AX 2 systems does not lead to major problems in interpretation of the results in terms of molecular motion.

  19. Density functional investigation of intermolecular effects on {sup 13}C NMR chemical-shielding tensors modeled with molecular clusters

    SciTech Connect

    Holmes, Sean T.; Dybowski, Cecil; Iuliucci, Robbie J.; Mueller, Karl T.

    2014-10-28

    A quantum-chemical method for modeling solid-state nuclear magnetic resonance chemical-shift tensors by calculations on large symmetry-adapted clusters of molecules is demonstrated. Four hundred sixty five principal components of the {sup 13}C chemical-shielding tensors of 24 organic materials are analyzed. The comparison of calculations on isolated molecules with molecules in clusters demonstrates that intermolecular effects can be successfully modeled using a cluster that represents a local portion of the lattice structure, without the need to use periodic-boundary conditions (PBCs). The accuracy of calculations which model the solid state using a cluster rivals the accuracy of calculations which model the solid state using PBCs, provided the cluster preserves the symmetry properties of the crystalline space group. The size and symmetry conditions that the model cluster must satisfy to obtain significant agreement with experimental chemical-shift values are discussed. The symmetry constraints described in the paper provide a systematic approach for incorporating intermolecular effects into chemical-shielding calculations performed at a level of theory that is more advanced than the generalized gradient approximation. Specifically, NMR parameters are calculated using the hybrid exchange-correlation functional B3PW91, which is not available in periodic codes. Calculations on structures of four molecules refined with density plane waves yield chemical-shielding values that are essentially in agreement with calculations on clusters where only the hydrogen sites are optimized and are used to provide insight into the inherent sensitivity of chemical shielding to lattice structure, including the role of rovibrational effects.

  20. Hypermetabolic state in the 7-month-old triple transgenic mouse model of Alzheimer's disease and the effect of lipoic acid: a 13C-NMR study

    PubMed Central

    Sancheti, Harsh; Patil, Ishan; Kanamori, Keiko; Díaz Brinton, Roberta; Zhang, Wei; Lin, Ai-Ling; Cadenas, Enrique

    2014-01-01

    Alzheimer's disease (AD) is characterized by age-dependent biochemical, metabolic, and physiologic changes. These age-dependent changes ultimately converge to impair cognitive functions. This study was carried out to examine the metabolic changes by probing glucose and tricarboxylic acid cycle metabolism in a 7-month-old triple transgenic mouse model of AD (3xTg-AD). The effect of lipoic acid, an insulin-mimetic agent, was also investigated to examine its ability in modulating age-dependent metabolic changes. Seven-month-old 3xTg-AD mice were given intravenous infusion of [1-13C]glucose followed by an ex vivo 13C nuclear magnetic resonance to determine the concentrations of 13C-labeled isotopomers of glutamate, glutamine, aspartate, gamma aminobutyric acid, and N-acetylaspartate. An intravenous infusion of [1-13C]glucose+[1,2-13C]acetate was given for different periods of time to distinguish neuronal and astrocytic metabolism. Enrichments of glutamate, glutamine, and aspartate were calculated after quantifying the total (12C+13C) concentrations by high-performance liquid chromatography. A hypermetabolic state was clearly evident in 7-month-old 3xTg-AD mice in contrast to the hypometabolic state reported earlier in 13-month-old mice. Hypermetabolism was evidenced by prominent increase of 13C labeling and enrichment in the 3xTg-AD mice. Lipoic acid feeding to the hypermetabolic 3xTg-AD mice brought the metabolic parameters to the levels of nonTg mice. PMID:25099753

  1. Hypermetabolic state in the 7-month-old triple transgenic mouse model of Alzheimer's disease and the effect of lipoic acid: a 13C-NMR study.

    PubMed

    Sancheti, Harsh; Patil, Ishan; Kanamori, Keiko; Díaz Brinton, Roberta; Zhang, Wei; Lin, Ai-Ling; Cadenas, Enrique

    2014-11-01

    Alzheimer's disease (AD) is characterized by age-dependent biochemical, metabolic, and physiologic changes. These age-dependent changes ultimately converge to impair cognitive functions. This study was carried out to examine the metabolic changes by probing glucose and tricarboxylic acid cycle metabolism in a 7-month-old triple transgenic mouse model of AD (3xTg-AD). The effect of lipoic acid, an insulin-mimetic agent, was also investigated to examine its ability in modulating age-dependent metabolic changes. Seven-month-old 3xTg-AD mice were given intravenous infusion of [1-(13)C]glucose followed by an ex vivo (13)C nuclear magnetic resonance to determine the concentrations of (13)C-labeled isotopomers of glutamate, glutamine, aspartate, gamma aminobutyric acid, and N-acetylaspartate. An intravenous infusion of [1-(13)C]glucose+[1,2-(13)C]acetate was given for different periods of time to distinguish neuronal and astrocytic metabolism. Enrichments of glutamate, glutamine, and aspartate were calculated after quantifying the total ((12)C+(13)C) concentrations by high-performance liquid chromatography. A hypermetabolic state was clearly evident in 7-month-old 3xTg-AD mice in contrast to the hypometabolic state reported earlier in 13-month-old mice. Hypermetabolism was evidenced by prominent increase of (13)C labeling and enrichment in the 3xTg-AD mice. Lipoic acid feeding to the hypermetabolic 3xTg-AD mice brought the metabolic parameters to the levels of nonTg mice. PMID:25099753

  2. Consistent fractionation of 13C in nature and in the laboratory: growth-rate effects in some haptophyte algae.

    PubMed

    Bidigare, R R; Fluegge, A; Freeman, K H; Hanson, K L; Hayes, J M; Hollander, D; Jasper, J P; King, L L; Laws, E A; Milder, J; Millero, F J; Pancost, R; Popp, B N; Steinberg, P A; Wakeham, S G

    1997-06-01

    The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by epsilon p approximately delta e - delta p, where delta e and delta p are the delta 13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, micromole kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, microM, and b = (25 - epsilon p)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] < or = 0.1 microM) fall above the b = f[PO4] line. Analysis of correlations expected between mu (growth rate), epsilon p, and Ce shows that, for our entire data set, most variations in epsilon p result from variations in mu rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera. PMID:11540616

  3. Consistent fractionation of 13C in nature and in the laboratory: Growth-rate effects in some haptophyte algae

    NASA Astrophysics Data System (ADS)

    Bidigare, Robert R.; Fluegge, Arnim; Freeman, Katherine H.; Hanson, Kristi L.; Hayes, John M.; Hollander, David; Jasper, John P.; King, Linda L.; Laws, Edward A.; Milder, Jeffrey; Millero, Frank J.; Pancost, Richard; Popp, Brian N.; Steinberg, Paul A.; Wakeham, Stuart G.

    1997-06-01

    The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by єP ≈ δe - δp, where δe and δp are the δ13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, μmol kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, μM, and b = (25 - єp)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] ≤ 0.1 μM) fall above the b = f[PO4] line. Analysis of correlations expected between μ (growth rate), єp, and Ce shows that, for our entire data set, most variations in єp result from variations in μ rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera.

  4. The interplay between the solid effect and the cross effect mechanisms in solid state 13C DNP at 95 GHz using trityl radicals

    NASA Astrophysics Data System (ADS)

    Banerjee, Debamalya; Shimon, Daphna; Feintuch, Akiva; Vega, Shimon; Goldfarb, Daniella

    2013-05-01

    The 13C solid state Dynamic Nuclear Polarization (DNP) mechanism using trityl radicals (OX63) as polarizers was investigated in the temperature range of 10-60 K. The solutions used were 6 M 13C urea in DMSO/H2O (50% v/v) with 15 mM and 30 mM OX63. The measurements were carried out at ˜3.5 T, which corresponds to Larmor frequencies of 95 GHz and 36 MHz for the OX63 and the 13C nuclei, respectively. Measurements of the 13C signal intensity as a function of the microwave (MW) irradiation frequency yielded 13C DNP spectra with temperature dependent lineshapes for both samples. The maximum enhancement for the 30 mM sample was reached at 40 K, while that of the 15 mM sample at 20-30 K. Furthermore, the lineshapes observed showed that both the cross effect (CE) and the solid effect (SE) DNP mechanisms are active in this temperature range and that their relative contribution is temperature dependent. Simulations of the spectra with the relative contributions of the CE and SE mechanisms as a fit parameter revealed that for both samples the CE contribution decreases with decreasing temperature while the SE contribution increases. In addition, for the 15 mM sample the contributions of the two mechanisms are comparable from 20 K to 60 K while for the 30 mM the CE dominates in this range, as expected from the higher concentration. The steep decrease of the CE contribution towards low temperatures is however unexpected. The temperature dependence of the OX63 longitudinal relaxation, DNP buildup times and 13C spin lattice relaxation times did not reveal any obvious correlation with the DNP temperature dependence. A similar behavior of the CE and SE mechanism was observed for 1H DNP with the nitroxide radical TEMPOL as a polarizer. This suggests that this effect is a general phenomenon involving a temperature dependent competition between the CE and SE mechanisms, the source of which is, however, still unknown.

  5. Effects of insulin on perfused liver from streptozotocin-diabetic and untreated rats: /sup 13/C NMR assay of pyruvate kinase flux

    SciTech Connect

    Cohen, S.M.

    1987-01-27

    The effects of insulin in vitro on perfused liver from streptozotocin-diabetic rats and their untreated littermates during gluconeogenesis from either (3-/sup 13/C)alanine + ethanol or (2-/sup 13/C)pyruvate + NH/sub 4/Cl + ethanol were studied by /sup 13/C NMR. A /sup 13/C NMR determination of the rate of pyruvate kinase flux under steady-state conditions of active gluconeogenesis was developed; this assay includes a check on the reuse of recycled pyruvate. The preparations studied provided gradations of pyruvate kinase flux within the confines of the assay's requirement of active gluconeogenesis. By this determination, the rate of pyruvate kinase flux was 0.74 +/- 0.04 of the gluconeogenic rate in liver from 24-h-fasted controls; in liver from 12-h fasted controls, relative pyruvate kinase flux increased to 1.0 +/- 0.2. In diabetic liver, this flux was undetectable by the authors NMR method. Insulin's hepatic influence in vitro was greatest in the streptozotocin model of type 1 diabetes: upon treatment of diabetic liver with 7 nM insulin in vitro, a partial reversal of many of the differences noted between diabetic and control liver was demonstrated by /sup 13/C NMR. A major effect of insulin in vitro upon diabetic liver was the induction of a large increase in the rate of pyruvate kinase flux, bringing relative and absolute fluxes up to the levels measured in 24-h-fasted controls. By way of comparison, the effects of ischemia on diabetic liver were studied by /sup 13/C NMR to test whether changes in allosteric effectors under these conditions could also increase pyruvate kinase flux. A large increase in this activity was demonstrated in ischemic diabetic liver.

  6. Isotope Substitution Effect in Polyatomic Molecules on the Example of 13C2H4 ← 12C2H4 Substitution

    NASA Astrophysics Data System (ADS)

    Bekhtereva, E. S.; Gromova, O. V.; Berezkin, K. B.; Kashirina, N. V.; Konov, I. A.; Bauerecker, S.

    2016-03-01

    General points of the theory of isotope substitution are applied to an analysis of the isotope substitution effect for the substitution 13C2H4←12C2H4 in the ethylene molecule. On the basis of the isotope relations so obtained, numerical predictions of band centers and the most significant rotational, centrifugal, and resonance parameters are made here for the first time for the four lower vibrational states of the 13C2H4 molecule, which can be used to analyze the complicated vibrational-rotational structure of the above-mentioned vibrational states.

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

    PubMed Central

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

    2013-01-01

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

  8. Effect of Glutamine, Glutamic Acid and Nucleotides on the Turnover of Carbon (δ13C) in Organs of Weaned Piglets

    PubMed Central

    Amorim, Alessandro Borges; Berto, Dirlei Antonio; Saleh, Mayra Anton Dib; Telles, Filipe Garcia; Denadai, Juliana Célia; Sartori, Maria Márcia Pereira; Luiggi, Fabiana Golin; Santos, Luan Sousa; Ducatti, Carlos

    2016-01-01

    Morphological and physiological alterations occur in the digestive system of weanling piglets, compromising the performance in subsequent phases. This experiment aimed at verifying the influence of glutamine, glutamate and nucleotides on the carbon turnover in the pancreas and liver of piglets weaned at 21 days of age. Four diets were evaluated: glutamine, glutamic acid or nucleotides-free diet (CD); containing 1% glutamine (GD); containing 1% glutamic acid (GAD) and containing 1% nucleotides (ND). One hundred and twenty-three piglets were utilized with three pigs slaughtered at day zero (weaning day) and three at each one of the experimental days (1, 2, 4, 5, 7, 9, 13, 20, 27, and 49 post-weaning), in order to collect organ samples, which were analyzed for the δ13C isotopic composition and compared by means of time. No differences were found (p>0.05) among treatments for the turnover of the 13C in the pancreas (T50% = 13.91, 14.37, 11.07, and 9.34 days; T95% = 46.22, 47.73, 36.79, and 31.04 days for CD, GD, GAD, and ND, respectively). In the liver, the ND presented accelerated values of carbon turnover (T50% = 7.36 and T95% = 24.47 days) in relation to the values obtained for the GD (T50% = 10.15 and T95% = 33.74 days). However, the values obtained for the CD (T50% = 9.12 and T95% = 30.31 days) and GAD (T50% = 7.83 and T95% = 26.03 days) had no differences (p>0.05) among other diets. The technique of 13C isotopic dilution demonstrated trophic action of nucleotides in the liver. PMID:26954179

  9. Effect of Glutamine, Glutamic Acid and Nucleotides on the Turnover of Carbon (δ(13)C) in Organs of Weaned Piglets.

    PubMed

    Amorim, Alessandro Borges; Berto, Dirlei Antonio; Saleh, Mayra Anton Dib; Telles, Filipe Garcia; Denadai, Juliana Célia; Sartori, Maria Márcia Pereira; Luiggi, Fabiana Golin; Santos, Luan Sousa; Ducatti, Carlos

    2016-08-01

    Morphological and physiological alterations occur in the digestive system of weanling piglets, compromising the performance in subsequent phases. This experiment aimed at verifying the influence of glutamine, glutamate and nucleotides on the carbon turnover in the pancreas and liver of piglets weaned at 21 days of age. Four diets were evaluated: glutamine, glutamic acid or nucleotides-free diet (CD); containing 1% glutamine (GD); containing 1% glutamic acid (GAD) and containing 1% nucleotides (ND). One hundred and twenty-three piglets were utilized with three pigs slaughtered at day zero (weaning day) and three at each one of the experimental days (1, 2, 4, 5, 7, 9, 13, 20, 27, and 49 post-weaning), in order to collect organ samples, which were analyzed for the δ(13)C isotopic composition and compared by means of time. No differences were found (p>0.05) among treatments for the turnover of the (13)C in the pancreas (T50% = 13.91, 14.37, 11.07, and 9.34 days; T95% = 46.22, 47.73, 36.79, and 31.04 days for CD, GD, GAD, and ND, respectively). In the liver, the ND presented accelerated values of carbon turnover (T50% = 7.36 and T95% = 24.47 days) in relation to the values obtained for the GD (T50% = 10.15 and T95% = 33.74 days). However, the values obtained for the CD (T50% = 9.12 and T95% = 30.31 days) and GAD (T50% = 7.83 and T95% = 26.03 days) had no differences (p>0.05) among other diets. The technique of (13)C isotopic dilution demonstrated trophic action of nucleotides in the liver. PMID:26954179

  10. Effects of cadmium combined with ultraviolet-B radiation on growth, gas exchange, and stable carbon isotope value (δ13C) in soybean (Glycine max L.)

    NASA Astrophysics Data System (ADS)

    Chen, Tuo; Qiang, Weiya; An, Lizhe; Wang, Xunling

    2003-06-01

    The changes in growth, gas exchange, and stable carbon isotope value (δ13C) in soybean seedlings (Glycine max L. Merr. cv. Longdou No.1) exposed to a 11.2 kJ m-2 day-1 biologically effective UV-B radiation (UV-BBE, 280-315 nm) and 50 mg CdCl2 kg-1 vermicular treatment, either alone or in combination were investigated under greenhouse conditions. Compared to the control, plant height and biomass, photosynthesis rates (Pn), water-use efficiency (WUE), and stomatal conductance (Gs) decreased significantly (P<0.05) exposed to cadmium (Cd) or UV-B radiation and combination. Leaf stable carbon isotope composition (δ13C values) decreased by Cd or UV-B radiation alone and in combination, δ13C were significantly correlated with changes in Pn, WUE and biomass. But Cd and UV-B in combination did not cause greater changes compared to Cd or UV-B radiation alone in many parameters. These results suggested that there was relatively little interaction of the two stresses. δ13C values may provide a reliable indication for growth, WUE, Pn or biomass of soybean seedlings when exposed to UV-B radiation and cadmium pollution.

  11. Effects of combustion emissions from the Eurasian continent in winter on seasonal δ 13C of elemental carbon in aerosols in Japan

    NASA Astrophysics Data System (ADS)

    Kawashima, Hiroto; Haneishi, Yuya

    2012-01-01

    We investigated suspended particulate matter (SPM, particles with a 100% cut-off aerodynamic diameter of 10 μm) and PM2.5 (particles with a 50% cut-off aerodynamic diameter of 2.5 μm) concentrations in aerosols sampled in Akita Prefecture, Japan, from April 2008 to January 2010, and the carbon isotope ratios (δ 13C) of elemental carbon (EC) in both SPM and PM2.5 and in samples from possible sources. We also determined the ion contents of SPM and estimated the back trajectories of air masses arriving at Akita Prefecture during the study period. The SPM concentration was very low (annual average, 15.2 μg m -3), and it tended to be higher in spring and lower in winter. We attributed the higher SPM in spring to dust storms brought from the Asian continent. The average annual PM2.5 concentration was 8.6 μg m -3. δ 13C of source samples (gasoline and diesel vehicle exhaust, fireplace soot, open biomass burning emissions, street dust, soil, charcoal, and coal) ranged from -34.7‰ to -1.8‰. δ 13C values of soot from gasoline light-duty (-24.4 ± 0.7‰) and passenger vehicles (-24.1 ± 0.6‰) were very similar to that of soot from all diesel vehicles (-24.3 ± 0.3‰). δ 13C was enriched in SPM in winter compared with summer values, moreover, only a slight seasonal trend was detected in δ 13C in PM2.5. From these data and the source results, we hypothesized that the enrichment of δ 13C of SPM and PM2.5 in winter was a long-range effect of overseas combustion processes such as coal combustion. In addition, δ 13C of SPM was correlated with Cl - and Mg 2+ contents in SPM, suggesting the influence of sea salt. We verified this hypothesis by back trajectory analyses. The results indicated a continental influence effects on EC of SPM and PM2.5 in winter.

  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. PMID:25795666

  13. 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

  14. The effect of dietary amino acid abundance and isotopic composition on the growth rate, metabolism and tissue δ13C of rainbow trout.

    PubMed

    Gaye-Siessegger, Julia; McCullagh, James S O; Focken, Ulfert

    2011-06-28

    The aim of the present study was to test whether the dietary non-essential/conditionally essential amino acid composition has an effect on growth and protein utilisation and on δ13C of individual amino acids in rainbow trout (Oncorhynchus mykiss). Trout were reared on six purified diets containing only synthetic amino acids in place of protein. Diet 1 mimicked the amino acid composition of fishmeal, in diet 2, cysteine (Cys), glycine (Gly), proline (Pro) and tyrosine (Tyr) were isonitrogenously replaced by their precursor amino acids serine (Ser), glutamic acid (Glu) and phenylalanine (Phe), and in diet 3, alanine (Ala), asparagine and aspartate, Cys, Gly, Pro, Ser and Tyr were isonitrogenously replaced by Glu. Diets 4, 5 and 6 resembled diets 1, 2 and 3 except that Glu contained 0·1 % 13C-enriched Glu. A control group was reared on a fishmeal-based diet. A total of forty-two trout (4·7 (sd 0·57) g) were fed one of the diets at a level of 3·5 % body mass for 10 weeks in a flow-through system. Dietary non-essential amino acid composition significantly influenced protein gain (P < 0·025) and δ13C of Ala, arginine (Arg), Gly, histidine (His), Phe and Tyr. Non-enriched Glu was predominantly found in trout fed 13C-enriched Glu, which is consistent with the fact that Glu has been shown to be used extensively in the gut as an energy source but is less consistent with the enrichment of Pro in fish fed diet 6 compared with fish fed diet 3. Further research is required to better understand the mechanisms that lead to the alteration of amino acid δ13C between diet and body tissues. PMID:21418707

  15. 13C MAS NMR studies of the effects of hydration on the cell walls of potatoes and Chinese water chestnuts.

    PubMed

    Tang, H; Belton, P S; Ng, A; Ryden, P

    1999-02-01

    13C NMR with magic angle spinning (MAS) has been employed to investigate the cell walls of potatoes and Chinese water chestnuts over a range of hydration levels. Both single-pulse excitation (SPEMAS) and cross-polarization (CPMAS) experiments were carried out. Hydration led to a substantial increase in signal intensities of galactan and galacturonan in the SPEMAS spectra and a decrease in line width, implying mobilization in the backbone and side chains of pectin. In CPMAS spectra of both samples, noncellulose components showed signal loss as hydration increased. However, the signals of some galacturonan in the 3(1) helix configuration remained in the spectra even when the water content was as high as 110%. Cellulose was unaffected. It is concluded that the pectic polysaccharides experience a distribution of molecular conformations and mobility, whereas cellulose remained as typical rigid solid. PMID:10563925

  16. Effects of post-reactor functionalization on the phase behaviour of an ethylene-1-octene copolymer studied using solid-state high resolution 13C NMR spectroscopy.

    PubMed

    Calucci, Lucia; Cicogna, Francesca; Forte, Claudia

    2013-10-01

    The effects of post-reactor functionalization with naphthoate-TEMPO on the structure and morphology of an ethylene-1-octene copolymer were investigated by means of solid-state NMR techniques and DSC measurements. Selective (13)C MAS experiments allowed the orthorhombic and the monoclinic crystalline phases and two amorphous phases with different degree of mobility to be detected and quantified. (13)C and (1)H relaxation time measurements and spin diffusion experiments gave insight into the polymer dynamics within the different phases, the crystalline domain dimensions, and the rate of chain diffusion between amorphous and crystalline phases. Comparison of the results obtained for the pristine copolymer and the functionalized samples clearly indicated that the functionalization procedure causes redistribution within the crystalline and the amorphous phases with no relevant change in the degree of crystallinity or in the crystalline domain average size, and slows down chain diffusion. PMID:23942957

  17. Experimental Evidence for Heavy-Atom Tunneling in the Ring-Opening of Cyclopropylcarbinyl Radical from Intramolecular 12C/13C Kinetic Isotope Effects

    PubMed Central

    Gonzalez-James, Ollie M.; Zhang, Xue; Datta, Ayan; Hrovat, David A.; Borden, Weston Thatcher; Singleton, Daniel A.

    2010-01-01

    The intramolecular 13C kinetic isotope effects for the ring-opening of cyclopropylcarbinyl radical were determined over a broad temperature range. The observed isotope effects are unprecedentedly large, ranging from 1.062 at 80 °C to 1.163 at −100 °C. Semi-classical calculations employing canonical variational transition state theory drastically underpredict the observed isotope effects, but the predicted isotope effects including tunneling by a small-curvature tunneling model match well with experiment. These results and a curvature in the Arrhenius plot of the isotope effects support the recently predicted importance of heavy-atom tunneling in cyclopropylcarbinyl ring-opening. PMID:20722415

  18. Experimental evidence for heavy-atom tunneling in the ring-opening of cyclopropylcarbinyl radical from intramolecular 12C/13C kinetic isotope effects.

    PubMed

    Gonzalez-James, Ollie M; Zhang, Xue; Datta, Ayan; Hrovat, David A; Borden, Weston Thatcher; Singleton, Daniel A

    2010-09-15

    The intramolecular (13)C kinetic isotope effects for the ring-opening of cyclopropylcarbinyl radical were determined over a broad temperature range. The observed isotope effects are unprecedentedly large, ranging from 1.062 at 80 degrees C to 1.163 at -100 degrees C. Semiclassical calculations employing canonical variational transition-state theory drastically underpredict the observed isotope effects, but the predicted isotope effects including tunneling by a small-curvature tunneling model match well with experiment. These results and a curvature in the Arrhenius plot of the isotope effects support the recently predicted importance of heavy-atom tunneling in cyclopropylcarbinyl ring-opening. PMID:20722415

  19. Effective Estimation of Dynamic Metabolic Fluxes Using 13C Labeling and Piecewise Affine Approximation: From Theory to Practical Applicability

    PubMed Central

    Schumacher, Robin; Wahl, S. Aljoscha

    2015-01-01

    The design of microbial production processes relies on rational choices for metabolic engineering of the production host and the process conditions. These require a systematic and quantitative understanding of cellular regulation. Therefore, a novel method for dynamic flux identification using quantitative metabolomics and 13C labeling to identify piecewise-affine (PWA) flux functions has been described recently. Obtaining flux estimates nevertheless still required frequent manual reinitalization to obtain a good reproduction of the experimental data and, moreover, did not optimize on all observables simultaneously (metabolites and isotopomer concentrations). In our contribution we focus on measures to achieve faster and robust dynamic flux estimation which leads to a high dimensional parameter estimation problem. Specifically, we address the following challenges within the PWA problem formulation: (1) Fast selection of sufficient domains for the PWA flux functions, (2) Control of over-fitting in the concentration space using shape-prescriptive modeling and (3) robust and efficient implementation of the parameter estimation using the hybrid implicit filtering algorithm. With the improvements we significantly speed up the convergence by efficiently exploiting that the optimization problem is partly linear. This allows application to larger-scale metabolic networks and demonstrates that the proposed approach is not purely theoretical, but also applicable in practice. PMID:26690237

  20. Quantitative solid-state 13C nuclear magnetic resonance spectrometric analyses of wood xylen: effect of increasing carbohydrate content

    USGS Publications Warehouse

    Bates, A.L.; Hatcher, P.G.

    1992-01-01

    Isolated lignin with a low carbohydrate content was spiked with increasing amounts of alpha-cellulose, and then analysed by solid-state 13C nuclear magnetic resonance (NMR) using cross-polarization with magic angle spinning (CPMAS) and dipolar dephasing methods in order to assess the quantitative reliability of CPMAS measurement of carbohydrate content and to determine how increasingly intense resonances for carbohydrate carbons affect calculations of the degree of lignin's aromatic ring substitution and methoxyl carbon content. Comparisons were made of the carbohydrate content calculated by NMR with carbohydrate concentrations obtained by phenol-sulfuric acid assay and by the calculation from the known amounts of cellulose added. The NMR methods used in this study yield overestimates for carbohydrate carbons due to resonance area overlap from the aliphatic side chain carbons of lignin. When corrections are made for these overlapping resonance areas, the NMR results agree very well with results obtained by other methods. Neither the calculated methoxyl carbon content nor the degree of aromatic ring substitution in lignin, both calculated from dipolar dephasing spectra, change with cellulose content. Likewise, lignin methoxyl content does not correlate with cellulose abundance when measured by integration of CPMAS spectra. ?? 1992.

  1. Sex difference in the effects of alcohol on gastric emptying in healthy volunteers: a study using the (13)C breath test.

    PubMed

    Horikoshi, Miyuki; Funakoshi, Akihiro; Miyasaka, Kyoko; Sekime, Ayako

    2013-01-01

    Several studies on alcohol and gastric emptying using the (13)C breath test showed that alcohol consumption delayed gastric emptying of meals in healthy male subjects. However, they did not employ female subjects, and the retention time of alcoholic beverages in the stomach has not been examined, yet. We examined the retention time (= gastric emptying rate) of alcoholic beverages in the stomach in healthy male and female subjects. We also examined whether the congeners (nonalcoholic components) of red wine have any effect on gastric emptying. The retention time of 60 mL of red wine, vodka, congeners of red wine, or mineral water, was measured using a (13)C labeled acetic acid breath test. In male subjects, the retention time of wine and vodka was significantly longer than that of congeners and mineral water. In female subjects, although the (13)C content in the breath was slightly but significantly decreased by wine and congeners, but not by vodka, and the parameters for gastric emptying did not differ significantly among the 4 drinks. That is, alcohol hardly influenced the retention time in female subjects. In conclusion, there are sex differences in the gastric emptying rate of alcohol. PMID:24389403

  2. Reduced mitochondrial malate dehydrogenase activity has a strong effect on photorespiratory metabolism as revealed by 13C labelling.

    PubMed

    Lindén, Pernilla; Keech, Olivier; Stenlund, Hans; Gardeström, Per; Moritz, Thomas

    2016-05-01

    Mitochondrial malate dehydrogenase (mMDH) catalyses the interconversion of malate and oxaloacetate (OAA) in the tricarboxylic acid (TCA) cycle. Its activity is important for redox control of the mitochondrial matrix, through which it may participate in regulation of TCA cycle turnover. In Arabidopsis, there are two isoforms of mMDH. Here, we investigated to which extent the lack of the major isoform, mMDH1 accounting for about 60% of the activity, affected leaf metabolism. In air, rosettes of mmdh1 plants were only slightly smaller than wild type plants although the fresh weight was decreased by about 50%. In low CO2 the difference was much bigger, with mutant plants accumulating only 14% of fresh weight as compared to wild type. To investigate the metabolic background to the differences in growth, we developed a (13)CO2 labelling method, using a custom-built chamber that enabled simultaneous treatment of sets of plants under controlled conditions. The metabolic profiles were analysed by gas- and liquid- chromatography coupled to mass spectrometry to investigate the metabolic adjustments between wild type and mmdh1 The genotypes responded similarly to high CO2 treatment both with respect to metabolite pools and (13)C incorporation during a 2-h treatment. However, under low CO2 several metabolites differed between the two genotypes and, interestingly most of these were closely associated with photorespiration. We found that while the glycine/serine ratio increased, a concomitant altered glutamine/glutamate/α-ketoglutarate relation occurred. Taken together, our results indicate that adequate mMDH activity is essential to shuttle reductants out from the mitochondria to support the photorespiratory flux, and strengthen the idea that photorespiration is tightly intertwined with peripheral metabolic reactions. PMID:26889011

  3. Reduced mitochondrial malate dehydrogenase activity has a strong effect on photorespiratory metabolism as revealed by 13C labelling

    PubMed Central

    Lindén, Pernilla; Keech, Olivier; Stenlund, Hans; Gardeström, Per; Moritz, Thomas

    2016-01-01

    Mitochondrial malate dehydrogenase (mMDH) catalyses the interconversion of malate and oxaloacetate (OAA) in the tricarboxylic acid (TCA) cycle. Its activity is important for redox control of the mitochondrial matrix, through which it may participate in regulation of TCA cycle turnover. In Arabidopsis, there are two isoforms of mMDH. Here, we investigated to which extent the lack of the major isoform, mMDH1 accounting for about 60% of the activity, affected leaf metabolism. In air, rosettes of mmdh1 plants were only slightly smaller than wild type plants although the fresh weight was decreased by about 50%. In low CO2 the difference was much bigger, with mutant plants accumulating only 14% of fresh weight as compared to wild type. To investigate the metabolic background to the differences in growth, we developed a 13CO2 labelling method, using a custom-built chamber that enabled simultaneous treatment of sets of plants under controlled conditions. The metabolic profiles were analysed by gas- and liquid- chromatography coupled to mass spectrometry to investigate the metabolic adjustments between wild type and mmdh1. The genotypes responded similarly to high CO2 treatment both with respect to metabolite pools and 13C incorporation during a 2-h treatment. However, under low CO2 several metabolites differed between the two genotypes and, interestingly most of these were closely associated with photorespiration. We found that while the glycine/serine ratio increased, a concomitant altered glutamine/glutamate/α-ketoglutarate relation occurred. Taken together, our results indicate that adequate mMDH activity is essential to shuttle reductants out from the mitochondria to support the photorespiratory flux, and strengthen the idea that photorespiration is tightly intertwined with peripheral metabolic reactions. PMID:26889011

  4. Laboratory measurement of temperature dependent 13C and D kinetic isotope effect in the reaction of CH4 oxidation by O(1D)

    NASA Astrophysics Data System (ADS)

    Shen, Linhan; Bui, Thinh Q.; Chen, Pin; Okumura, Mitchio

    2014-11-01

    Martian atmospheric methane (CH4) concentrations observed from satellite orbiter and Earth based telescopes have shown significant time and spatial variations. Recent MSL measurements observed very low methane concentrations (0.18 ± 0.67 ppbv). In order to reconcile these findings, a search of missing methane sinks is needed. In this study, we investigated the kinetic isotope effect (KIE) of methane oxidation reaction by O(1D) as a function of temperature, which will provide an important constraint to the loss of methane. The KIE of major methane isotopologues (13CH4 and 12CH3D) are measured as a function of temperature. The experiments were carried out by photolyzing a mixture of N2O, isotope enriched methane, and He at 193 nm in a temperature controlled cell between 155 K and 300 K. The N2O molecules were used as an O(1D) source, while He was used to collisionally quench translationally hot O(1D) radicals. The concentrations of all major methane isotopologues before and after photolysis were analyzed using a frequency stabilized cavity ringdown (FS-CRDS) spectrometer. The spectrometer employs coupling of two orthogonally polarized cw lasers into a ringdown cavity for simultaneous spectral measurements over the full wavelength range of 1.45 - 1.65 µm and is capable of measuring isotopes of methane of enriched samples to a very high precision (D < 0.03% and 13C < 0.01%). We measured for the first time the D-KIE and 13C-KIE at temperatures relative to the Martian conditions. Our measurements observed D-KIE(155 K) = 1.133(20), and 13C-KIE(115 K) = 1.149(22).

  5. Indirect relativistic bridge and substituent effects from the 'heavy' environment on the one-bond and two-bond (13)C-(1)H spin-spin coupling constants.

    PubMed

    Rusakova, Irina L; Rusakov, Yury Yu; Krivdin, Leonid B

    2016-01-01

    Indirect relativistic bridge effect (IRBE) and indirect relativistic substituent effect (IRSE) induced by the 'heavy' environment of the IV-th, V-th and VI-th main group elements on the one-bond and geminal (13)C-(1)H spin-spin coupling constants are observed, and spin-orbit parts of these two effects were interpreted in terms of the third-order Rayleigh-Schrödinger perturbation theory. Both effects, IRBE and IRSE, rapidly increase with the total atomic charge of the substituents at the coupled carbon. The accumulation of IRSE for geminal coupling constants is not linear with respect to the number of substituents in contrast to the one-bond couplings where IRSE is an essentially additive quantity. PMID:26352434

  6. CARBON-13 NUCLEAR MAGNETIC RESONANCE. 13C CHEMICAL SHIFTS AND 13C-199HG COUPLING CONSTANTS FOR SOME ORGANOMERCURY COMPOUNDS

    EPA Science Inventory

    The (13)C shieldings and (13)C-(199)Hg coupling constants of fourteen phenyl- and seven alkyl- and alkenyl-mercury compounds have been obtained. Substituent effects on the (13)C shieldings are similar to those in nonmercurated phenyl compounds, with a similar relationship between...

  7. Methionine kinetics in adult men: effects of dietary betaine on L-(2H3-methyl-1-13C)methionine

    SciTech Connect

    Storch, K.J.; Wagner, D.A.; Young, V.R. )

    1991-08-01

    The effects of a daily 3-g supplement of betaine on kinetic aspects of L-(2H3-methyl-1-13C)methionine (MET) metabolism in healthy young adult men were explored. Four groups of four subjects each were given a control diet, based on an L-amino acid mixture supplying 29.5 and 21.9 mg.kg-1.d-1 of L-methionine and L-cystine for 4 d before the tracer study, conducted on day 5 during the fed state. Two groups received the control diet and two groups received the betaine supplement. Tracer was given intravenously (iv) or orally. The transmethylation rate of MET (TM), homocysteine remethylation (RM), and oxidation of methionine were estimated from plasma methionine labeling and 13C enrichment of expired air. RM tended to increase (P = 0.14) but the TM and methionine oxidation were significantly (P less than 0.05) higher after betaine supplementation when estimated with the oral tracer. No differences were detected with the intravenous tracer. Methionine concentration in plasma obtained from blood taken from subjects in the fed state was higher (P less than 0.01) with betaine supplementation. These results suggest that excess methyl-group intake may increase the dietary requirement for methionine.

  8. Effects of Boron Nutrition and Water Stress on Nitrogen Fixation, Seed δ15N and δ13C Dynamics, and Seed Composition in Soybean Cultivars Differing in Maturities

    PubMed Central

    Bellaloui, Nacer; Mengistu, Alemu

    2015-01-01

    Therefore, the objective of the current research was to investigate the effects of foliar B nutrition on seed protein, oil, fatty acids, and sugars under water stress conditions. A repeated greenhouse experiment was conducted using different maturity group (MG) cultivars. Plants were well-watered with no foliar B (W − B), well-watered with foliar B (W + B), water-stressed with no foliar B (WS − B), and water-stressed with foliar B (WS + B). Foliar B was applied at rate of 0.45 kg·ha−1 and was applied twice at flowering and at seed-fill stages. The results showed that seed protein, sucrose, fructose, and glucose were higher in W + B treatment than in W − B, WS + B, and WS − B. The increase in protein in W + B resulted in lower seed oil, and the increase of oleic in WS − B or WS + B resulted in lower linolenic acid. Foliar B resulted in higher nitrogen fixation and water stress resulted in seed δ15N and δ13C alteration. Increased stachyose indicated possible physiological and metabolic changes in carbon and nitrogen pathways and their sources under water stress. This research is beneficial to growers for fertilizer management and seed quality and to breeders to use 15N/14N and 13C/12C ratios and stachyose to select for drought tolerance soybean. PMID:25667936

  9. Total-body protein turnover in parenterally fed neonates: effects of energy source studied by using [15N]glycine and [1-13C]leucine.

    PubMed

    Pencharz, P; Beesley, J; Sauer, P; Van Aerde, J; Canagarayar, U; Renner, J; McVey, M; Wesson, D; Swyer, P

    1989-12-01

    The effects of nonprotein energy source (ie, glucose only vs glucose and lipid) on nitrogen retention and total-body protein turnover were studied in 20 parenterally fed newborn infants. All infants received approximately 3 g amino acids and 80-90 kcal.kg body wt.d. Total-body protein synthesis was estimated by using three constant-infusion, end-product methods: enrichment of urinary urea and ammonia in response to a [15N]glycine label and exhaled carbon dioxide enrichment in response to a [1-13C]leucine label. No differences were seen in nitrogen retention between the two energy sources. The estimate of total-body protein turnover obtained from the 13C label was similar to that obtained with the [15N]urea label. No differences in turnover rates were observed between the two diet groups. Use of the glucose-plus-lipid fuel system enhanced energy storage and the reutilization of amino acid for protein synthesis. PMID:2512806

  10. Implications of the large carbon kinetic isotope effect in the reaction CH4 + Cl for the 13C/12C ratio of stratospheric CH4

    NASA Astrophysics Data System (ADS)

    Bergamaschi, P.; Brühl, C.; Brenninkmeijer, C. A. M.; Saueressig, G.; Crowley, J. N.; Grooß, J. U.; Fischer, H.; Crutzen, P. J.

    Recent investigations of the carbon kinetic isotope effect (KIE) of the reaction CH4 + Cl yielded KIECl = 1.066±0.002 at 297 K (increasing to 1.075±0.005 at 223 K) [Saueressig et al., 1995]. In order to assess the effect of the exceptionally large KIEcl on δ13C of stratospheric CH4 we applied a two-dimensional, time dependent chemical transport model. The model results demonstrate the strong influence of the CH4 + Cl reaction on δ13CH4 in particular in the middle and upper stratosphere, where this reaction contributes several tens of percent to the total CH4 sink. The Cl sink helps to explain the relatively large overall isotope fractionation of 1.010-1.012 observed in the lower stratosphere [Brenninkmeijer et al., 1995; Brenninkmeijer et al., 1996], even though the model results predict a smaller effect than observed.

  11. The C-13/C-12 kinetic isotope effect for soil oxidation of methane at ambient atmospheric concentrations

    NASA Technical Reports Server (NTRS)

    King, Stagg L.; Quay, Paul D.; Lansdown, John M.

    1989-01-01

    During a survey of the Alaskan North Slope to estimate the isotopic composition and fluxes of methane (CH4) from the tundra, two sites were encountered that showed net methane consumption within flux chambers. Methane concentrations decreased from ambient (1.78 ppmv) by up to 50 percent, and the delta C-13 increased by up to 10 percent in the two chamber deployments showing CH4 consumption. CH4 consumption rates were measured to be 1.2 and 0.6 mg CH4/sq m per day; the corresponding carbon kinetic isotope effects (k13/k12) were 0.974 and 0.984, respectively.

  12. Analysing Groundwater Using the 13C Isotope

    NASA Astrophysics Data System (ADS)

    Awad, Sadek

    The stable isotope of the carbon atom (13C) give information about the type of the mineralisation of the groundwater existing during the water seepage and about the recharge conditions of the groundwater. The concentration of the CO2(aq.) dissolved during the infiltration of the water through the soil's layers has an effect on the mineralisation of this water. The type of the photosynthesis's cycle (C-3 or C-4 carbon cycle) can have a very important role to determine the conditions (closed or open system) of the mineralisation of groundwater. The isotope 13C of the dissolved CO2 in water give us a certain information about the origin and the area of pollution of water. The proportion of the biogenic carbon and its percentage in the mineralisation of groundwater is determined by using the isotope 13C.

  13. Partitioning of carbon sources among functional pools to investigate short-term priming effects of biochar in soil: A (13)C study.

    PubMed

    Kerré, Bart; Hernandez-Soriano, Maria C; Smolders, Erik

    2016-03-15

    Biochar sequesters carbon (C) in soils because of its prolonged residence time, ranging from several years to millennia. In addition, biochar can promote indirect C-sequestration by increasing crop yield while, potentially, reducing C-mineralization. This laboratory study was set up to evaluate effects of biochar on C-mineralization with due attention to source appointment by using (13)C isotope signatures. An arable soil (S) (7.9g organic C, OCkg(-1)) was amended (single dose of 10gkg(-1) soil) with dried, grinded maize stover (leaves and stalks), either natural (R) or (13)C enriched (R*), and/or biochar (B/B*) prepared from the maize stover residues (450°C). Accordingly, seven different combinations were set up (S, SR, SB, SR*, SB*, SRB*, SR*B) to trace the source of C in CO2 (180days), dissolved organic-C (115days) and OC in soil aggregate fractions (90days). The application of biochar to soil reduced the mineralization of native soil organic C but the effect on maize stover-C mineralization was not consistent. Biochar application decreased the mineralization of the non-enriched maize stover after 90days, this being consistent with a significant reduction of dissolved organic C concentration from 45 to 18mgL(-1). However, no significant effect was observed for the enriched maize stover, presumably due to differences between the natural and enriched materials. The combined addition of biochar and enriched maize stover significantly increased (twofold) the presence of native soil organic C or maize derived C in the free microaggregate fraction relative to soil added only with stover. Although consistent effects among C sources and biochar materials remains elusive, our outcomes indicate that some biochar products can reduce mineralization and solubilization of other sources of C while promoting their physical protection in soil particles. PMID:26780129

  14. Effect of age and ration on diet-tissue isotopic (Δ13C, Δ15N) discrimination in striped skunks (Mephitis mephitis).

    PubMed

    Hobson, Keith A; Quirk, Travis W

    2014-01-01

    An important prerequisite for the effective use of stable isotopes in animal ecology is the accurate assessment of isotopic discrimination factors linking animals to their diets for a multitude of tissue types. Surprisingly, these values are poorly known in general and especially for mammalian carnivores and omnivores in particular. Also largely unknown are the factors that influence diet-tissue isotopic discrimination such as nutritional quality and age. We raised adult and juvenile striped skunks (Mephitis mephitis) in captivity on a constant omnivore diet (Mazuri Omnivore A 5635). Adults (n=6) and juveniles (n=3) were kept for 7 months and young (n=7) to the age of 50 days. We then examined individuals for stable carbon (δ(13)C) and nitrogen (δ(15)N) isotope values of hair, nails, lipid, liver, muscle, bone collagen and the plasma, and cellular fractions of blood. Discrimination values differed among age groups and were significantly higher for young compared with their mothers, likely due to the effects of weaning. Δ(15)N isotopic discrimination factors ranged from 3.14 (nails) to 5.6‰ (plasma) in adults and 4.3 (nails) to 5.8‰ (liver) for young. For Δ(13)C, values ranged from-3.3 (fat) to 3.0‰ (collagen) in adults and from-3.3 (fat) to 2.0‰ (collagen) in young. Our data provide an important tool for predicting diets and source of feeding for medium-sized mammalian omnivorous adults integrated over short (e.g. liver, plasma) through long (e.g. collagen) periods and underline the potential effects of age on isotopic values in omnivore diets. PMID:24506487

  15. NMR ({sup 1}H and {sup 13}C) based signatures of abnormal choline metabolism in oral squamous cell carcinoma with no prominent Warburg effect

    SciTech Connect

    Bag, Swarnendu; Banerjee, Deb Ranjan; Basak, Amit; Das, Amit Kumar; Pal, Mousumi; Banerjee, Rita; Paul, Ranjan Rashmi; Chatterjee, Jyotirmoy

    2015-04-17

    At functional levels, besides genes and proteins, changes in metabolome profiles are instructive for a biological system in health and disease including malignancy. It is understood that metabolomic alterations in association with proteomic and transcriptomic aberrations are very fundamental to unravel malignant micro-ambient criticality and oral cancer is no exception. Hence deciphering intricate dimensions of oral cancer metabolism may be contributory both for integrated appreciation of its pathogenesis and to identify any critical but yet unexplored dimension of this malignancy with high mortality rate. Although several methods do exist, NMR provides higher analytical precision in identification of cancer metabolomic signature. Present study explored abnormal signatures in choline metabolism in oral squamous cell carcinoma (OSCC) using {sup 1}H and {sup 13}C NMR analysis of serum. It has demonstrated down-regulation of choline with concomitant up-regulation of its break-down product in the form of trimethylamine N-oxide in OSCC compared to normal counterpart. Further, no significant change in lactate profile in OSCC possibly indicated that well-known Warburg effect was not a prominent phenomenon in such malignancy. Amongst other important metabolites, malonate has shown up-regulation but D-glucose, saturated fatty acids, acetate and threonine did not show any significant change. Analyzing these metabolomic findings present study proposed trimethyl amine N-oxide and malonate as important metabolic signature for oral cancer with no prominent Warburg effect. - Highlights: • NMR ({sup 1}H and {sup 13}C) study of Oral Squamous cell Carcinoma Serum. • Abnormal Choline metabolomic signatures. • Up-regulation of Trimethylamine N-oxide. • Unchanged lactate profile indicates no prominent Warburg effect. • Proposed alternative glucose metabolism path through up-regulation of malonate.

  16. GC-{sup 13}C IRMS characterisation of extractable and covalently bound alkanes in petroleum source rocks to reveal compositional fractionation effects

    SciTech Connect

    Love, G.D.; Fallick, A.E.; Taylor, C.

    1995-12-31

    The application of a sequential extraction/degradation scheme to differentiate between molecular alkanes (both easily extractable and physically-trapped) and covalently-bound alkyl moieties to a number of vitrinite concentrates and petroleum source rocks has been reported previously. Gas chromatography-isotope ratio mass spectrometry GC-s{sup 13}C IRMS has now been applied to the different awe fractions to probe compositional fractionation effects that might occur from the different initial biological inputs. For a Turkish oil shale (Goynuk - Type I kerogen), inputs from diverse sources, including phytoplanktron, higher plants and bacteria were implied from analysis of solvent-extractable alkanes. However, the much larger quantities of covalently-bound alkanes had an isotopic signature typical of eukarytoic (freshwater) algae. The isotopic uniformity of alkanes/alkenes released from sequential hydropyrolysis of a torbanite (Duunet shale) confirmed that this sample was largely derived from the selective preservation of resistant aliphatic biopolymers found in Botryococcus cell walls.

  17. 13C and 18O fractionation effects on open splits and on the ion source in continuous flow isotope ratio mass spectrometry.

    PubMed

    Elsig, Joachim; Leuenberger, Markus C

    2010-05-30

    Measurements of carbon and oxygen isotopes of CO(2) by continuous flow isotope ratio mass spectrometry are widely used in environmental studies and climate change research. Yet, there are remaining problems associated with the reproducibility of measurements, in particular when high precision is required and/or the amount of sample material is limited. Isotopic fractionations in open splits and nonlinear effects occurring in the mass spectrometer due to different sample amounts alter the results. In this study, we discuss the influence and the origin of these two effects and propose procedures for preventing their impact. Fractionation in the open split can be related to diffusion of CO(2) and can lead to shifted delta-values when measuring a sample gas against a reference gas injected via different open splits. We present a method, where such fractionations can be minimized by adjusting either the position of the capillaries or the flow rates involved or both. The nonlinear peak area dependence of delta(13)C measurements for small sample sizes can be explained by adsorption/desorption processes in the ionization chamber or its vicinity. For constant amplitudes, the magnitude of the nonlinearity only depends on the amount of CO(2) entering the ion source. This nonlinearity can be eliminated by a small additional flux of a conditioning gas fed to the mass spectrometer. The best results were obtained when using carbon monoxide. For the adsorption process in the mass spectrometer we found a fractionation factor of 0.982 +/- 0.005 for delta(13)C and 1.002 +/- 0.004 for delta(18)O. PMID:20411581

  18. Solvent effect on pathways and mechanisms for D-fructose conversion to 5-hydroxymethyl-2-furaldehyde: in situ 13C NMR study.

    PubMed

    Kimura, Hiroshi; Nakahara, Masaru; Matubayasi, Nobuyuki

    2013-03-14

    Noncatalytic reactions of D-fructose were kinetically investigated in dimethylsulfoxide (DMSO), water, and methanol as a function of time at temperatures of 30-150 °C by applying in situ (13)C NMR spectroscopy. The products were quantitatively analyzed with distinction of isomeric species by taking advantage of site-selective (13)C labeling technique. In DMSO, D-fructose was converted first into 3,4-dihydroxy-2-dihydroxymethyl-5-hydroxymethyltetrahydrofuran having no double bond in the ring, subsequently into 4-hydroxy-5-hydroxymethyl-4,5-dihydrofuran-2-carbaldehyde having one double bond through dehydration, and finally into 5-hydroxymethyl-2-furaldehyde (5-HMF) having two double bonds. No other reaction pathways were involved, as shown from the carbon mass balance. In water, 5-HMF, the final product in DMSO, was generated with the precursors undetected and furthermore transformed predominantly into formic and levulinic acids and slightly into 1,2,4-benzenetriol accompanied by polymerization. D-glucose was also produced through the reversible transformation of the reactant D-fructose. In methanol, some kinds of anhydro-D-fructoses were generated instead of 5-HMF. The reaction pathways can thus be controlled by taking advantage of the solvent effect. The D-fructose conversion reactions are of the first order with respect to the concentration of D-fructose and proceed on the order of minutes in DMSO but on the order of hours in water and methanol. The rate constant was three orders of magnitude larger in DMSO than in water or methanol. PMID:23458365

  19. Carbon flux analysis by 13C nuclear magnetic resonance to determine the effect of CO2 on anaerobic succinate production by Corynebacterium glutamicum.

    PubMed

    Radoš, Dušica; Turner, David L; Fonseca, Luís L; Carvalho, Ana Lúcia; Blombach, Bastian; Eikmanns, Bernhard J; Neves, Ana Rute; Santos, Helena

    2014-05-01

    Wild-type Corynebacterium glutamicum produces a mixture of lactic, succinic, and acetic acids from glucose under oxygen deprivation. We investigated the effect of CO2 on the production of organic acids in a two-stage process: cells were grown aerobically in glucose, and subsequently, organic acid production by nongrowing cells was studied under anaerobic conditions. The presence of CO2 caused up to a 3-fold increase in the succinate yield (1 mol per mol of glucose) and about 2-fold increase in acetate, both at the expense of l-lactate production; moreover, dihydroxyacetone formation was abolished. The redistribution of carbon fluxes in response to CO2 was estimated by using (13)C-labeled glucose and (13)C nuclear magnetic resonance (NMR) analysis of the labeling patterns in end products. The flux analysis showed that 97% of succinate was produced via the reductive part of the tricarboxylic acid cycle, with the low activity of the oxidative branch being sufficient to provide the reducing equivalents needed for the redox balance. The flux via the pentose phosphate pathway was low (~5%) regardless of the presence or absence of CO2. Moreover, there was significant channeling of carbon to storage compounds (glycogen and trehalose) and concomitant catabolism of these reserves. The intracellular and extracellular pools of lactate and succinate were measured by in vivo NMR, and the stoichiometry (H(+):organic acid) of the respective exporters was calculated. This study shows that it is feasible to take advantage of natural cellular regulation mechanisms to obtain high yields of succinate with C. glutamicum without genetic manipulation. PMID:24610842

  20. Carbon Flux Analysis by 13C Nuclear Magnetic Resonance To Determine the Effect of CO2 on Anaerobic Succinate Production by Corynebacterium glutamicum

    PubMed Central

    Radoš, Dušica; Turner, David L.; Fonseca, Luís L.; Carvalho, Ana Lúcia; Blombach, Bastian; Eikmanns, Bernhard J.; Neves, Ana Rute

    2014-01-01

    Wild-type Corynebacterium glutamicum produces a mixture of lactic, succinic, and acetic acids from glucose under oxygen deprivation. We investigated the effect of CO2 on the production of organic acids in a two-stage process: cells were grown aerobically in glucose, and subsequently, organic acid production by nongrowing cells was studied under anaerobic conditions. The presence of CO2 caused up to a 3-fold increase in the succinate yield (1 mol per mol of glucose) and about 2-fold increase in acetate, both at the expense of l-lactate production; moreover, dihydroxyacetone formation was abolished. The redistribution of carbon fluxes in response to CO2 was estimated by using 13C-labeled glucose and 13C nuclear magnetic resonance (NMR) analysis of the labeling patterns in end products. The flux analysis showed that 97% of succinate was produced via the reductive part of the tricarboxylic acid cycle, with the low activity of the oxidative branch being sufficient to provide the reducing equivalents needed for the redox balance. The flux via the pentose phosphate pathway was low (∼5%) regardless of the presence or absence of CO2. Moreover, there was significant channeling of carbon to storage compounds (glycogen and trehalose) and concomitant catabolism of these reserves. The intracellular and extracellular pools of lactate and succinate were measured by in vivo NMR, and the stoichiometry (H+:organic acid) of the respective exporters was calculated. This study shows that it is feasible to take advantage of natural cellular regulation mechanisms to obtain high yields of succinate with C. glutamicum without genetic manipulation. PMID:24610842

  1. Whey and casein labeled with L-[1-13C]leucine and muscle protein synthesis: effect of resistance exercise and protein ingestion.

    PubMed

    Reitelseder, Søren; Agergaard, Jakob; Doessing, Simon; Helmark, Ida C; Lund, Peter; Kristensen, Niels B; Frystyk, Jan; Flyvbjerg, Allan; Schjerling, Peter; van Hall, Gerrit; Kjaer, Michael; Holm, Lars

    2011-01-01

    Muscle protein turnover following resistance exercise and amino acid availability are relatively well described. By contrast, the beneficial effects of different sources of intact proteins in relation to exercise need further investigation. Our objective was to compare muscle anabolic responses to a single bolus intake of whey or casein after performance of heavy resistance exercise. Young male individuals were randomly assigned to participate in two protein trials (n = 9) or one control trial (n = 8). Infusion of l-[1-(13)C]leucine was carried out, and either whey, casein (0.3 g/kg lean body mass), or a noncaloric control drink was ingested immediately after exercise. l-[1-(13)C]leucine-labeled whey and casein were used while muscle protein synthesis (MPS) was assessed. Blood and muscle tissue samples were collected to measure systemic hormone and amino acid concentrations, tracer enrichments, and myofibrillar protein synthesis. Western blots were used to investigate the Akt signaling pathway. Plasma insulin and branched-chain amino acid concentrations increased to a greater extent after ingestion of whey compared with casein. Myofibrillar protein synthesis was equally increased 1-6 h postexercise after whey and casein intake, both of which were higher compared with control (P < 0.05). Phosphorylation of Akt and p70(S6K) was increased after exercise and protein intake (P < 0.05), but no differences were observed between the types of protein except for total 4E-BP1, which was higher after whey intake than after casein intake (P < 0.05). In conclusion, whey and casein intake immediately after resistance exercise results in an overall equal MPS response despite temporal differences in insulin and amino acid concentrations and 4E-BP1. PMID:21045172

  2. 12C/ 13C kinetic isotope effects of the gas-phase reactions of isoprene, methacrolein, and methyl vinyl ketone with OH radicals

    NASA Astrophysics Data System (ADS)

    Iannone, Richard; Koppmann, Ralf; Rudolph, Jochen

    The stable-carbon kinetic isotope effects (KIEs) for the gas-phase reactions of isoprene, methacrolein (MACR), and methyl vinyl ketone (MVK) with OH radicals were studied in a 25 L reaction chamber at (298 ± 2) K and ambient pressure. The time dependence of both the stable-carbon isotope ratios and the concentrations was determined using a gas-chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The volatile organic compounds (VOCs) used in the KIE experiments had natural-abundance isotopic composition thus KIE data obtained from these experiments can be directly applied to atmospheric studies of isoprene chemistry. All 12C/ 13/C KIE values are reported as ɛ values, where ɛ = (KIE - 1) × 1000‰, and KIE = k12/ k13. The following average stable-carbon KIEs were obtained: (6.56 ± 0.12)‰ (isoprene), (6.47 ± 0.27)‰ (MACR), and (7.58 ± 0.47)‰ (MVK). The measured KIEs all agree within uncertainty to an inverse molecular mass (MM) dependence of OHɛ(‰) = (487 ± 18)MM -1, which was derived from two previous studies [ J. Geophys. Res.2000, 105, 29329-29346; J. Phys. Chem. A2004, 108, 11537-11544]. Upon adding the isoprene, MACR, and MVK OHɛ values from this study, the inverse MM dependence changes only marginally to OHɛ(‰) = (485 ± 14)MM -1. The addition of these isoprene OHɛ values to a recently measured set of ɛO3 values in an analogous study [ Atmos. Environ.2008, 42, 8728-8737] allows for estimates of the average change in the 12C/ 13C ratio due to processing in the troposphere.

  3. Predicting Effects of Cations (Mg, Ca, Na, and K) on 13C-18O Clumping in Dissolved Inorganic Carbon Species and Implications for Carbonate Geothermometry

    NASA Astrophysics Data System (ADS)

    Hill, P. S.; Tripati, A.; Schauble, E. A.

    2014-12-01

    13C-18O bond abundance in carbonates is becoming more widely used as a geothermometer; this proxy is affected by various environmental factors. Here we report the influence of cations (Mg2+, Ca2+, Na+, and K+) at high concentrations (~2 mol/liter) on the isotopologue composition of the DIC pool. Clumped isotope fractionation in CO32- groups of dissolved species and carbonate minerals is reported using the notation Δ63 corresponding mainly to the enrichment in per mil of Hx13C18O16O2x-2 (plus Hx12C18O17O 16Ox-2, Hx12C17O17O 17Ox-2, and Hx13C17O17O 16Ox-2) above the amount expected for a random distribution of isotopes among all CO32-, HCO3- and H2CO3 isotopologues. The Δ63 of a solution of dissolved inorganic carbon (DIC) depends upon the relative abundances of each DIC species (CO2(aq) or H2CO3, HCO3-, and CO32-) since each DIC species has a distinct equilibrium clumped isotope signature. These abundances depend primarily upon solution pH and secondarily upon temperature and salinity (fresh water vs. sea water vs. brine). Solvated DIC species with additional ions and the composite DIC solutions were modeled as a series of supermolecular clusters, each with a single DIC molecule, an added cation, and 21 to 32 surrounding H2O molecules. As in our previous work (Hill et al., 2014, GCA 125, 610-652), we developed electronic structure models at different levels of theory to ensure the best possible reliability at reasonable computational efficiency. Overall, the models predict that common aqueous cations will slightly increase the 13C-18O clumping signature of both individual DIC species and the total DIC pool at a given pH, salinity, and temperature. Predicted Δ63values are also dependent upon cation concentration. The perturbing effect of Mg2+ > Ca2+ > K+ > Na+. Dissolved cations increase the clumped crossover pH (pH at which the composite Δ63 of the DIC pool equals the Δ63 of calcite at equilibrium). Our models predict that a DIC solution of low to moderate p

  4. Effect of organic matter application on CP-MAS-13C-NMR spectra of humic acids from a brown soil

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    The humified SOM or humic substances (HS) composed of humic acid (HA), fulvic acid (FA) and humin (HM) represent the most microbially recalcitrant and stable reservoir of organic carbon in soil (Piccolo et al., 2004). OM applications can influence the amount and structural characteristics of HS(Dou et al., 2008). During the past few decades, there has been much research on HS, but their chemical structure is still not fully understood (Dong, 2006).CP-MAS-13C-NMR spectroscopy was considered as an effective method to study structures of HS without dissolving problem compared with liquid 13C-NMR (Conte et al., 1997; Dou et al., 2008). It can directly measure the carbon framework and reflect the nature of HS transformation after OM application (Spaccini et al., 2000). For that reason, this method was applied in this study. The objective of this paper was to clarify the effect of long term OM application on the changes of structural characteristics in HAs, which provided new information for improving soil fertility by OM application. The experiment was carried out on a brown soil (Paleudalf in USDA Soil Taxonomy) at Shenyang Agricultural University, Liaoning province, China (N41°48'-E123°25'). The experiment included 3 treatments: zero-treatment (CKbr), and two pig manure (PM) treatments (O1 and O2) at the rates of 0.9 t ha-1 and 1.8 t ha-1 of organic carbon, respectively. The samples of the HA fraction were extracted, separated and purified according to the method described by Dou et al. (1991). Elemental composition, Differential thermal analysis (DTA), -lgK value, FT-IR and CP-MAS- 13C-NMR of HAs were performed. Effects on the contents of orgaic carbon and its composition. The contents of TOC were from 8.77 g kg-1 to 12.25 g kg-1. The relative contents in TOC for WSS, HA, and FA were 6.87%, 14.2% and 19.8%. Comparing the CKbr, the contents of WSS, HA and FA for O1 and O2 increased, but relative contents of WSS and FA decreased. The content of the HA increased after

  5. Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ13C and δ15N)

    PubMed Central

    Nelson, James A.; Rozar, Katherine L.; Adams, Charles S.; Wall, Kara R.; Switzer, Theodore S.; Winner, Brent L.; Hollander, David J.

    2015-01-01

    Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ13C and δ15N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ15N values in nearly all comparisons. Ethanol also had strong effects on the δ13C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and corresponding

  6. Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ (13)C and δ (15)N).

    PubMed

    Stallings, Christopher D; Nelson, James A; Rozar, Katherine L; Adams, Charles S; Wall, Kara R; Switzer, Theodore S; Winner, Brent L; Hollander, David J

    2015-01-01

    Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ (13)C and δ (15)N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ (15)N values in nearly all comparisons. Ethanol also had strong effects on the δ (13)C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and

  7. Cost effectiveness analysis of population-based serology screening and 13C-Urea breath test for Helicobacter pylori to prevent gastric cancer: A markov model

    PubMed Central

    Xie, Feng; Luo, Nan; Lee, Hin-Peng

    2008-01-01

    AIM: To compare the costs and effectiveness of no screening and no eradication therapy, the population-based Helicobacter pylori (H pylori) serology screening with eradication therapy and 13C-Urea breath test (UBT) with eradication therapy. METHODS: A Markov model simulation was carried out in all 237 900 Chinese males with age between 35 and 44 from the perspective of the public healthcare provider in Singapore. The main outcome measures were the costs, number of gastric cancer cases prevented, life years saved, and quality-adjusted life years (QALYs) gained from screening age to death. The uncertainty surrounding the cost-effectiveness ratio was addressed by one-way sensitivity analyses. RESULTS: Compared to no screening, the incremental cost-effectiveness ratio (ICER) was $16 166 per life year saved or $13 571 per QALY gained for the serology screening, and $38 792 per life year saved and $32 525 per QALY gained for the UBT. The ICER was $477 079 per life year saved or $390 337 per QALY gained for the UBT compared to the serology screening. The cost-effectiveness of serology screening over the UBT was robust to most parameters in the model. CONCLUSION: The population-based serology screening for H pylori was more cost-effective than the UBT in prevention of gastric cancer in Singapore Chinese males. PMID:18494053

  8. Priming effect of (13)C-labelled wheat straw in no-tillage soil under drying and wetting cycles in the Loess Plateau of China.

    PubMed

    Liu, Enke; Wang, Jianbo; Zhang, Yanqing; Angers, Denis A; Yan, Changrong; Oweis, Theib; He, Wenqing; Liu, Qin; Chen, Baoqing

    2015-01-01

    The objectives of this study were to determine the effects of drying and wetting (DW) cycles on soil organic carbon (SOC) mineralisation and on the priming effect (PE) induced by the addition of (13)C-labelled wheat straw to long-term no-tillage (NT) and conventional-tillage (CT) soils. We observed that the SOC mineralisation rate in rewetted soils was greater than that in soils that were kept at constant water content. The proportion of CO2 derived from the straw declined dramatically during the first 10 days. The priming direction was first positive, and then became slightly negative. The PE was higher under DW cycles than under constant water content. There was no significant effect of the tillage system on the SOC mineralisation rate or PE. The data indicate that the DW cycles had a significant effect on the SOC mineralisation rate and on the PE, demonstrating a positive combined effect between wheat straw and moisture fluctuations. Further research is needed to study the role of microbial communities and C pools in affecting the SOC mineralisation response to DW cycles. PMID:26345303

  9. Priming effect of 13C-labelled wheat straw in no-tillage soil under drying and wetting cycles in the Loess Plateau of China

    PubMed Central

    Liu, Enke; Wang, Jianbo; Zhang, Yanqing; Angers, Denis A.; Yan, Changrong; Oweis, Theib; He, Wenqing; Liu, Qin; Chen, Baoqing

    2015-01-01

    The objectives of this study were to determine the effects of drying and wetting (DW) cycles on soil organic carbon (SOC) mineralisation and on the priming effect (PE) induced by the addition of 13C-labelled wheat straw to long-term no-tillage (NT) and conventional-tillage (CT) soils. We observed that the SOC mineralisation rate in rewetted soils was greater than that in soils that were kept at constant water content. The proportion of CO2 derived from the straw declined dramatically during the first 10 days. The priming direction was first positive, and then became slightly negative. The PE was higher under DW cycles than under constant water content. There was no significant effect of the tillage system on the SOC mineralisation rate or PE. The data indicate that the DW cycles had a significant effect on the SOC mineralisation rate and on the PE, demonstrating a positive combined effect between wheat straw and moisture fluctuations. Further research is needed to study the role of microbial communities and C pools in affecting the SOC mineralisation response to DW cycles. PMID:26345303

  10. Effect of organic matter application on CP-MAS-13C-NMR spectra of humic acids from a brown soil

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    The humified SOM or humic substances (HS) composed of humic acid (HA), fulvic acid (FA) and humin (HM) represent the most microbially recalcitrant and stable reservoir of organic carbon in soil (Piccolo et al., 2004). OM applications can influence the amount and structural characteristics of HS(Dou et al., 2008). During the past few decades, there has been much research on HS, but their chemical structure is still not fully understood (Dong, 2006).CP-MAS-13C-NMR spectroscopy was considered as an effective method to study structures of HS without dissolving problem compared with liquid 13C-NMR (Conte et al., 1997; Dou et al., 2008). It can directly measure the carbon framework and reflect the nature of HS transformation after OM application (Spaccini et al., 2000). For that reason, this method was applied in this study. The objective of this paper was to clarify the effect of long term OM application on the changes of structural characteristics in HAs, which provided new information for improving soil fertility by OM application. The experiment was carried out on a brown soil (Paleudalf in USDA Soil Taxonomy) at Shenyang Agricultural University, Liaoning province, China (N41°48'-E123°25'). The experiment included 3 treatments: zero-treatment (CKbr), and two pig manure (PM) treatments (O1 and O2) at the rates of 0.9 t ha-1 and 1.8 t ha-1 of organic carbon, respectively. The samples of the HA fraction were extracted, separated and purified according to the method described by Dou et al. (1991). Elemental composition, Differential thermal analysis (DTA), -lgK value, FT-IR and CP-MAS- 13C-NMR of HAs were performed. Effects on the contents of orgaic carbon and its composition. The contents of TOC were from 8.77 g kg-1 to 12.25 g kg-1. The relative contents in TOC for WSS, HA, and FA were 6.87%, 14.2% and 19.8%. Comparing the CKbr, the contents of WSS, HA and FA for O1 and O2 increased, but relative contents of WSS and FA decreased. The content of the HA increased after

  11. /sup 18/O isotope effect in /sup 13/C nuclear magnetic resonance spectroscopy. Part 9. Hydrolysis of benzyl phosphate by phosphatase enzymes and in acidic aqueous solutions

    SciTech Connect

    Parente, J.E.; Risley, J.M.; Van Etten, R.L.

    1984-12-26

    The /sup 18/O isotope-induced shifts in /sup 13/C and /sup 31/P nuclear magnetic resonance (NMR) spectroscopy were used to establish the position of bond cleavage in the phosphatase-catalyzed and acid-catalyzed hydrolysis reactions of benzyl phosphate. The application of the /sup 18/O-isotope effect in NMR spectroscopy affords a continuous, nondestructive assay method for following the kinetics and position of bond cleavage in the hydrolytic process. The technique provides advantages over most discontinuous methods in which the reaction components must be isolated and converted to volatile derivatives prior to analysis. In the present study, (..cap alpha..-/sup 13/C,ester-/sup 18/O)benzyl phosphate and (ester-/sup 18/O)benzyl phosphate were synthesized for use in enzymatic and nonenzymatic studies. Hydrolysis reactions catalyzed by the alkaline phosphatase from E. coli and by the acid phosphatases isolated from human prostate and human liver were all accompanied by cleavage of the substrate phosphorus-oxygen bond consistent with previously postulated mechanisms involving covalent phosphoenzyme intermediates. An extensive study of the acid-catalyzed hydrolysis of benzyl phosphate at 75/sup 0/C revealed that the site of bond cleavage is dependent on pH. At pH less than or equal to 1.3, the hydrolysis proceeds with C-O bond cleavage; at 1.3 < pH < 2.0, there is a mixture of C-O and P-O bond scission, the latter progressively predominating as the pH is raised; at pH greater than or equal to 2.0, the hydrolysis proceeds with exclusive P-O bond scission. (S)-(+)-(..cap alpha..-/sup 2/H)Benzyl phosphate was also synthesized. Hydrolysis of this chiral benzyl derivative demonstrated that the acid-catalyzed C-O bond scission of benzyl phosphate proceeds by an A-1 (S/sub N/1) mechanism with 70% racemization and 30% inversion at carbon. 37 references, 4 figures, 2 tables.

  12. Effect of a test meal on the intragastric distribution of urea in the 13C-urea breath test for Helicobacter pylori.

    PubMed Central

    Atherton, J C; Washington, N; Blackshaw, P E; Greaves, J L; Perkins, A C; Hawkey, C J; Spiller, R C

    1995-01-01

    Test meals are invariably used in the 13C-urea breath test (UBT) but their effect on the intragastric distribution and gastric residence time of urea given in the test is unknown. The site of Helicobacter pylori urease measured in the test is unknown and whether the test measures total or regional gastric urease is uncertain. This study reports the results of paired UBTs with simultaneous gastric distribution studies, one with and one without a fatty test meal, two weeks apart on seven H pylori infected subjects. The test meal did not affect UBT results at 10 minutes, but increased values at 30 minutes and thereafter. The amount of scintigraphic label in the antrum at 10 minutes was also unaffected by the meal but increased at 30 minutes and thereafter, whereas the amount in the body/fundus was greatly increased both at 10 minutes and throughout the test. There was considerable variation in intragastric distribution of urea between subjects, both with and without the test meal. This study shows that a test meal profoundly affects intragastric distribution of urea solution in the UBT, and increases UBT values at 30 minutes and later. Variability between subjects, however, means that accurate measurement of total or regional gastric urease is probably unrealistic. Images Figure 1 PMID:7698688

  13. In folio respiratory fluxomics revealed by 13C isotopic labeling and H/D isotope effects highlight the noncyclic nature of the tricarboxylic acid "cycle" in illuminated leaves.

    PubMed

    Tcherkez, Guillaume; Mahé, Aline; Gauthier, Paul; Mauve, Caroline; Gout, Elizabeth; Bligny, Richard; Cornic, Gabriel; Hodges, Michael

    2009-10-01

    While the possible importance of the tricarboxylic acid (TCA) cycle reactions for leaf photosynthesis operation has been recognized, many uncertainties remain on whether TCA cycle biochemistry is similar in the light compared with the dark. It is widely accepted that leaf day respiration and the metabolic commitment to TCA decarboxylation are down-regulated in illuminated leaves. However, the metabolic basis (i.e. the limiting steps involved in such a down-regulation) is not well known. Here, we investigated the in vivo metabolic fluxes of individual reactions of the TCA cycle by developing two isotopic methods, (13)C tracing and fluxomics and the use of H/D isotope effects, with Xanthium strumarium leaves. We provide evidence that the TCA "cycle" does not work in the forward direction like a proper cycle but, rather, operates in both the reverse and forward directions to produce fumarate and glutamate, respectively. Such a functional division of the cycle plausibly reflects the compromise between two contrasted forces: (1) the feedback inhibition by NADH and ATP on TCA enzymes in the light, and (2) the need to provide pH-buffering organic acids and carbon skeletons for nitrate absorption and assimilation. PMID:19675152

  14. Molecular single-particle effects in the /sup 12/C+/sup 17,18/O and /sup 13/C+/sup 17/O reactions

    SciTech Connect

    Cha, M.H.; Park, J.Y.; Scheid, W.

    1987-12-01

    We have used the asymmetric two-center shell model to calculate the single-neutron energies in the /sup 12/C+ /sup 17,18/O and /sup 13/C+ /sup 17/O collisions as a function of the internuclear distance. The periodic resonancelike structures observed in the angle-integrated inelastic cross sections for these systems can be understood in terms of the nuclear Landau-Zener promotion of a loosely bound valence neutron from the 1d/sub 5/2/ (..cap omega.. = (1/2) state to the 2s/sub 1/2/ state of the oxygen isotopes. Inclusion of the effects of a turning point in the Landau-Zener formula is found to give marked improvements in accounting for the observed angle-integrated inelastic cross sections for these systems. Intermediate structures in the cross sections are found to arise due to the energy-dependent oscillatory behavior of the partial cross sections. While some resonancelike peaks can be attributed to a single orbital angular momentum, many others arise due to the combined contributions of two or more angular momenta.

  15. Evaluation of 13C-urea breath test in the detection of Helicobacter pylori and in monitoring the effect of tripotassium dicitratobismuthate in non-ulcer dyspepsia.

    PubMed Central

    Dill, S; Payne-James, J J; Misiewicz, J J; Grimble, G K; McSwiggan, D; Pathak, K; Wood, A J; Scrimgeour, C M; Rennie, M J

    1990-01-01

    Sixty nine patients with non-ulcer dyspepsia have been studied with endoscopy, biopsy, quick urease (CLO) test, Helicobacter pylori culture, and the 13C-urea breath test before and after treatment with tripotassium dicitratobismuthane (DeNol) two tablets twice daily for four weeks. Symptoms of non-ulcer dyspepsia were recorded using a standard questionnaire. Using H pylori culture as the gold standard, the sensitivity of the 13C-urea breath test was 90%, the specificity 98.6%, and the accuracy 94.8% with a positive predictive value of 98.2% and a negative predictive value of 92.5%. Conversion rate from H pylori positive to negative status after treatment with tripotassium dicitratobismuthate was 17.9%. Symptoms of non-ulcer dyspepsia improved appreciably after treatment irrespective of H pylori status. The 13C-urea breath test is an accurate research tool suitable for serial testing and population surveys. PMID:2253905

  16. /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.

  17. Comparative effect of salinity on growth, grain yield, water use efficiency, δ(13)C and δ(15)N of landraces and improved durum wheat varieties.

    PubMed

    Chamekh, Zoubeir; Ayadi, Sawsen; Karmous, Chahine; Trifa, Youssef; Amara, Hajer; Boudabbous, Khaoula; Yousfi, Salima; Serret, Maria Dolors; Araus, José Luis

    2016-10-01

    Supplemental irrigation with low-quality water will be paramount in Mediterranean agriculture in the future, where durum wheat is a major crop. Breeding for salinity tolerance may contribute towards improving resilience to irrigation with brackish water. However, identification of appropriate phenotyping traits remains a bottleneck in breeding. A set of 25 genotypes, including 19 landraces and 6 improved varieties most cultivated in Tunisia, were grown in the field and irrigated with brackish water (6, 13 and 18dSm(-1)). Improved genotypes exhibited higher grain yield (GY) and water use efficiency at the crop level (WUEyield or 'water productivity'), shorter days to flowering (DTF), lower N concentration (N) and carbon isotope composition (δ(13)C) in mature kernels and lower nitrogen isotope composition (δ(15)N) in the flag leaf compared with landraces. GY was negatively correlated with DTF and the δ(13)C and N of mature kernels and was positively correlated with the δ(15)N of the flag leaf. Moreover, δ(13)C of mature kernels was negatively correlated with WUEyield. The results highlight the importance of shorter phenology together with photosynthetic resilience to salt-induced water stress (lower δ(13)C) and nitrogen metabolism (higher N and δ(15)N) for assessing genotypic performance to salinity. PMID:27593462

  18. The Effect of Molecular Conformation on the Accuracy of Theoretical (1)H and (13)C Chemical Shifts Calculated by Ab Initio Methods for Metabolic Mixture Analysis.

    PubMed

    Chikayama, Eisuke; Shimbo, Yudai; Komatsu, Keiko; Kikuchi, Jun

    2016-04-14

    NMR spectroscopy is a powerful method for analyzing metabolic mixtures. The information obtained from an NMR spectrum is in the form of physical parameters, such as chemical shifts, and construction of databases for many metabolites will be useful for data interpretation. To increase the accuracy of theoretical chemical shifts for development of a database for a variety of metabolites, the effects of sets of conformations (structural ensembles) and the levels of theory on computations of theoretical chemical shifts were systematically investigated for a set of 29 small molecules in the present study. For each of the 29 compounds, 101 structures were generated by classical molecular dynamics at 298.15 K, and then theoretical chemical shifts for 164 (1)H and 123 (13)C atoms were calculated by ab initio quantum chemical methods. Six levels of theory were used by pairing Hartree-Fock, B3LYP (density functional theory), or second order Møller-Plesset perturbation with 6-31G or aug-cc-pVDZ basis set. The six average fluctuations in the (1)H chemical shift were ±0.63, ± 0.59, ± 0.70, ± 0.62, ± 0.75, and ±0.66 ppm for the structural ensembles, and the six average errors were ±0.34, ± 0.27, ± 0.32, ± 0.25, ± 0.32, and ±0.25 ppm. The results showed that chemical shift fluctuations with changes in the conformation because of molecular motion were larger than the differences between computed and experimental chemical shifts for all six levels of theory. In conclusion, selection of an appropriate structural ensemble should be performed before theoretical chemical shift calculations for development of an accurate database for a variety of metabolites. PMID:26963288

  19. Trimethylamine and Organic Matter Additions Reverse Substrate Limitation Effects on the δ13C Values of Methane Produced in Hypersaline Microbial Mats.

    PubMed

    Kelley, Cheryl A; Nicholson, Brooke E; Beaudoin, Claire S; Detweiler, Angela M; Bebout, Brad M

    2014-12-01

    Methane production has been observed in a number of hypersaline environments, and it is generally thought that this methane is produced through the use of noncompetitive substrates, such as the methylamines, dimethylsulfide and methanol. Stable isotope measurements of the produced methane have also suggested that the methanogens are operating under conditions of substrate limitation. Here, substrate limitation in gypsum-hosted endoevaporite and soft-mat hypersaline environments was investigated by the addition of trimethylamine, a noncompetitive substrate for methanogenesis, and dried microbial mat, a source of natural organic matter. The δ(13)C values of the methane produced after amendments were compared to those in unamended control vials. At all hypersaline sites investigated, the δ(13)C values of the methane produced in the amended vials were statistically lower (by 10 to 71‰) than the unamended controls, supporting the hypothesis of substrate limitation at these sites. When substrates were added to the incubation vials, the methanogens within the vials fractionated carbon isotopes to a greater degree, resulting in the production of more (13)C-depleted methane. Trimethylamine-amended samples produced lower methane δ(13)C values than the mat-amended samples. This difference in the δ(13)C values between the two types of amendments could be due to differences in isotope fractionation associated with the dominant methane production pathway (or substrate used) within the vials, with trimethylamine being the main substrate used in the trimethylamine-amended vials. It is hypothesized that increased natural organic matter in the mat-amended vials would increase fermentation rates, leading to higher H2 concentrations and increased CO2/H2 methanogenesis. PMID:25239903

  20. Trimethylamine and Organic Matter Additions Reverse Substrate Limitation Effects on the δ13C Values of Methane Produced in Hypersaline Microbial Mats

    PubMed Central

    Nicholson, Brooke E.; Beaudoin, Claire S.; Detweiler, Angela M.; Bebout, Brad M.

    2014-01-01

    Methane production has been observed in a number of hypersaline environments, and it is generally thought that this methane is produced through the use of noncompetitive substrates, such as the methylamines, dimethylsulfide and methanol. Stable isotope measurements of the produced methane have also suggested that the methanogens are operating under conditions of substrate limitation. Here, substrate limitation in gypsum-hosted endoevaporite and soft-mat hypersaline environments was investigated by the addition of trimethylamine, a noncompetitive substrate for methanogenesis, and dried microbial mat, a source of natural organic matter. The δ13C values of the methane produced after amendments were compared to those in unamended control vials. At all hypersaline sites investigated, the δ13C values of the methane produced in the amended vials were statistically lower (by 10 to 71‰) than the unamended controls, supporting the hypothesis of substrate limitation at these sites. When substrates were added to the incubation vials, the methanogens within the vials fractionated carbon isotopes to a greater degree, resulting in the production of more 13C-depleted methane. Trimethylamine-amended samples produced lower methane δ13C values than the mat-amended samples. This difference in the δ13C values between the two types of amendments could be due to differences in isotope fractionation associated with the dominant methane production pathway (or substrate used) within the vials, with trimethylamine being the main substrate used in the trimethylamine-amended vials. It is hypothesized that increased natural organic matter in the mat-amended vials would increase fermentation rates, leading to higher H2 concentrations and increased CO2/H2 methanogenesis. PMID:25239903

  1. High-Frequency (13)C and (29)Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of Tl(I) and Pb(II): Decisive Role of Relativistic Effects.

    PubMed

    Vícha, Jan; Marek, Radek; Straka, Michal

    2016-02-15

    The (13)C and (29)Si NMR signals of ligand atoms directly bonded to Tl(I) or Pb(II) heavy-element centers are predicted to resonate at very high frequencies, up to 400 ppm for (13)C and over 1000 ppm for (29)Si, outside the typical experimental NMR chemical-shift ranges for a given type of nuclei. The large (13)C and (29)Si NMR chemical shifts are ascribed to sizable relativistic spin-orbit effects, which can amount to more than 200 ppm for (13)C and more than 1000 ppm for (29)Si, values unexpected for diamagnetic compounds of the main group elements. The origin of the vast spin-orbit contributions to the (13)C and (29)Si NMR shifts is traced to the highly efficient 6p → 6p* metal-based orbital magnetic couplings and related to the 6p orbital-based bonding together with the low-energy gaps between the occupied and virtual orbital subspaces in the subvalent Tl(I) and Pb(II) compounds. New NMR spectral regions for these compounds are suggested based on the fully relativistic density functional theory calculations in the Dirac-Coulomb framework carefully calibrated on the experimentally known NMR data for Tl(I) and Pb(II) complexes. PMID:26820039

  2. Effects of configurational disorder on the elastic properties of icosahedral boron-rich alloys based on B6O, B13C2, and B4C, and their mixing thermodynamics

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    The elastic properties of alloys between boron suboxide (B6O) and boron carbide (B13C2), denoted by (B6O)1-x(B13C2)x, as well as boron carbide with variable carbon content, ranging from B13C2 to B4C are calculated from first-principles. Furthermore, the mixing thermodynamics of (B6O)1-x(B13C2)x is studied. A superatom-special quasirandom structure approach is used for modeling different atomic configurations, in which effects of configurational disorder between the carbide and suboxide structural units, as well as between boron and carbon atoms within the units, are taken into account. Elastic properties calculations demonstrate that configurational disorder in B13C2, where a part of the C atoms in the CBC chains substitute for B atoms in the B12 icosahedra, drastically increase the Young's and shear modulus, as compared to an atomically ordered state, B12(CBC). These calculated elastic moduli of the disordered state are in excellent agreement with experiments. Configurational disorder between boron and carbon can also explain the experimentally observed almost constant elastic moduli of boron carbide as the carbon content is changed from B4C to B13C2. The elastic moduli of the (B6O)1-x(B13C2)x system are also practically unchanged with composition if boron-carbon disorder is taken into account. By investigating the mixing thermodynamics of the alloys, in which the Gibbs free energy is determined within the mean-field approximation for the configurational entropy, we outline the pseudo-binary phase diagram of (B6O)1-x(B13C2)x. The phase diagram reveals the existence of a miscibility gap at all temperatures up to the melting point. Also, the coexistence of B6O-rich as well as ordered or disordered B13C2-rich domains in the material prepared through equilibrium routes is predicted.

  3. Effects of foliar boron application on seed composition, cell wall boron, and seed δ15N and δ13C isotopes in water-stressed soybean plants

    PubMed Central

    Bellaloui, Nacer; Hu, Yanbo; Mengistu, Alemu; Kassem, My A.; Abel, Craig A.

    2013-01-01

    Limited information is available on the effects of foliar boron (B) application on soybean seed composition. The objective of this research was to investigate the effects of foliar B on seed composition (protein, oil, fatty acids, and sugars). Our hypothesis was that since B is involved in nitrogen and carbon metabolism, it may impact seed composition. A repeated greenhouse experiment was conducted where half of the soybean plants was exposed to water stress (WS) and the other half was well-watered. Foliar boron (FB) in the form of boric acid was applied twice at a rate of 1.1 kg ha−1. The first application was during flowering stage, and the second application was during seed-fill stage. Treatments were water stressed plants with no FB (WS–B); water stressed plants with FB (WS+B); watered plants without FB (W–B), and watered plants with FB (W+B). The treatment W–B was used as a control. Comparing with WS–B plants, B concentration was the highest in leaves and seed of W+B plants (84% increase in leaves and 73% in seed). Seeds of W+B plants had higher protein (11% increase), oleic acid (27% increase), sucrose (up to 40% increase), glucose, and fructose comparing with W–B. However, seed stachyose concentrations increased by 43% in WS–B plants seed compared with W–B plants. Cell wall (structural) B concentration in leaves was higher in all plants under water stress, especially in WS–B plants where the percentage of cell wall B reached up to 90%. Water stress changed seed δ15N and δ13C values in both B applied and non-B applied plants, indicating possible effects on nitrogen and carbon metabolism. This research demonstrated that FB increased B accumulation in leaves and seed, and altered seed composition of well-watered and water stressed plants, indicating a possible involvement of B in seed protein, and oleic and linolenic fatty acids. Further research is needed to explain mechanisms of B involvement in seed protein and fatty acids. PMID:23888163

  4. Effects of foliar boron application on seed composition, cell wall boron, and seed δ(15)N and δ(13)C isotopes in water-stressed soybean plants.

    PubMed

    Bellaloui, Nacer; Hu, Yanbo; Mengistu, Alemu; Kassem, My A; Abel, Craig A

    2013-01-01

    Limited information is available on the effects of foliar boron (B) application on soybean seed composition. The objective of this research was to investigate the effects of foliar B on seed composition (protein, oil, fatty acids, and sugars). Our hypothesis was that since B is involved in nitrogen and carbon metabolism, it may impact seed composition. A repeated greenhouse experiment was conducted where half of the soybean plants was exposed to water stress (WS) and the other half was well-watered. Foliar boron (FB) in the form of boric acid was applied twice at a rate of 1.1 kg ha(-1). The first application was during flowering stage, and the second application was during seed-fill stage. Treatments were water stressed plants with no FB (WS-B); water stressed plants with FB (WS+B); watered plants without FB (W-B), and watered plants with FB (W+B). The treatment W-B was used as a control. Comparing with WS-B plants, B concentration was the highest in leaves and seed of W+B plants (84% increase in leaves and 73% in seed). Seeds of W+B plants had higher protein (11% increase), oleic acid (27% increase), sucrose (up to 40% increase), glucose, and fructose comparing with W-B. However, seed stachyose concentrations increased by 43% in WS-B plants seed compared with W-B plants. Cell wall (structural) B concentration in leaves was higher in all plants under water stress, especially in WS-B plants where the percentage of cell wall B reached up to 90%. Water stress changed seed δ(15)N and δ(13)C values in both B applied and non-B applied plants, indicating possible effects on nitrogen and carbon metabolism. This research demonstrated that FB increased B accumulation in leaves and seed, and altered seed composition of well-watered and water stressed plants, indicating a possible involvement of B in seed protein, and oleic and linolenic fatty acids. Further research is needed to explain mechanisms of B involvement in seed protein and fatty acids. PMID:23888163

  5. Effect of salinity and water stress during the reproductive stage on growth, ion concentrations, Delta 13C, and delta 15N of durum wheat and related amphiploids.

    PubMed

    Yousfi, Salima; Serret, Maria Dolores; Voltas, Jordi; Araus, José Luis

    2010-08-01

    The physiological performance of durum wheat and two related amphiploids was studied during the reproductive stage under different combinations of salinity and irrigation. One triticale, one tritordeum, and four durum wheat genotypes were grown in pots in the absence of stress until heading, when six different treatments were imposed progressively. Treatments resulted from the combination of two irrigation regimes (100% and 35% of container water capacity) with three levels of water salinity (1.8, 12, and 17 dS m(-1)), and were maintained for nearly 3 weeks. Gas exchange and chlorophyll fluorescence and content were measured prior to harvest; afterwards shoot biomass and height were recorded, and Delta(13)C, delta(15)N, and the concentration of nitrogen (N), phosphorus, and several ions (K(+), Na(+), Ca(2+), Mg(2+)) were analysed in shoot material. Compared with control conditions (full irrigation with Hoagland normal) all other treatments inhibited photosynthesis through stomatal closure, accelerated senescence, and decreased biomass. Full irrigation with 12 dS m(-1) outperformed other stress treatments in terms of biomass production and physiological performance. Biomass correlated positively with N and delta(15)N, and negatively with Na(+) across genotypes and fully irrigated treatments, while relationships across deficit irrigation conditions were weaker or absent. Delta(13)C did not correlate with biomass across treatments, but it was the best trait correlating with phenotypic differences in biomass within treatments. Tritordeum produced more biomass than durum wheat in all treatments. Its low Delta(13)C and high K(+)/Na(+) ratio, together with a high potential growth, may underlie this finding. Mechanisms relating delta(15)N and Delta(13)C to biomass are discussed. PMID:20660293

  6. 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.

  7. Efficacy and cost-effectiveness of the 13C-urea breath test as the primary diagnostic investigation for the detection of Helicobacter pylori infection compared to invasive and non-invasive diagnostic tests

    PubMed Central

    Nocon, Marc; Kuhlmann, Alexander; Leodolter, Andreas; Roll, Stephanie; Vauth, Christoph; Willich, Stefan N.; Greiner, Wolfgang

    2009-01-01

    Background Helicobacter pylori (H. pylori) is one of the most common bacterial infections in humans. There is a risk factor for gastric or duodenal ulcers, gastric cancer and MALT (Mucosa Associated Lymphoid Tissue)-Lymphomas. There are several invasive and non-invasive methods available for the diagnosis of H. pylori. The 13C-urea breath test is a non-invasive method recommended for monitoring H. pylori eradication therapy. However, this test is not yet used for primary assessment of H. pylori in Germany. Objectives What are the clinical and health economic benefits of the 13C-urea breath test in the primary assessment of H. pylori compared to other invasive and non-invasive methods? Methods A systematic literature search including a hand search was performed for studies investigating test criteria and cost-effectiveness of the 13C-urea breath test in comparison to other methods used in the primary assessment of H. pylori. Only studies that directly compared the 13C-urea breath test to other H. pylori-tests were included. For the medical part, biopsy-based tests were used as the gold standard. Results 30 medical studies are included. Compared to the immunoglobulin G (IgG) test, the sensitivity of the 13C-urea breath test is higher in twelve studies, lower in six studies and one study reports no differences. The specificity is higher in 13 studies, lower in three studies and two studies report no differences. Compared to the stool antigen test, the sensitivity of the 13C-urea breath test is higher in nine studies, lower in three studies and one study reports no difference. The specificity is higher in nine studies, lower in two studies and two studies report no differences. Compared to the urease test, the sensitivity of the 13C-urea breath test is higher in four studies, lower in three studies and four studies report no differences. The specificity is higher in five studies, lower in five studies and one study reports no difference. Compared to histology, the

  8. Short communication: Using diurnal patterns of (13)C enrichment of CO2 to evaluate the effects of nitrate and docosahexaenoic acid on fiber degradation in the rumen of lactating dairy cows.

    PubMed

    Klop, G; Bannink, A; Dieho, K; Gerrits, W J J; Dijkstra, J

    2016-09-01

    Nitrate decreases enteric CH4 production in ruminants, but may also negatively affect fiber degradation. In this experiment, 28 lactating Holstein dairy cows were grouped into 7 blocks. Within blocks, cows were randomly assigned to 1 of 4 isonitrogenous treatments in a 2×2 factorial arrangement: control (CON); NO3 [21g of nitrate/kg of dry matter (DM)]; DHA [3g of docosahexaenoic acid (DHA)/kg of DM]; or NO3+DHA (21g of nitrate/kg of DM and 3g of DHA/kg of DM). Cows were fed a total mixed ration consisting of 21% grass silage, 49% corn silage, and 30% concentrates on a DM basis. Based on the difference in natural (13)C enrichment and neutral detergent fiber and starch content between grass silage and corn silage, we investigated whether a negative effect on rumen fiber degradation could be detected by evaluating diurnal patterns of (13)C enrichment of exhaled carbon dioxide. A significant nitrate × DHA interaction was found for neutral detergent fiber digestibility, which was reduced on the NO3 treatment to an average of 55%, as compared with 61, 64, and 65% on treatments CON, DHA, and NO3+DHA, respectively. Feeding nitrate, but not DHA, resulted in a pronounced increase in (13)C enrichment of CO2 in the first 3 to 4 h after feeding only. Results support the hypothesis that effects of a feed additive on the rate of fiber degradation in the rumen can be detected by evaluating diurnal patterns of (13)C enrichment of CO2. To be able to detect this, the main ration components have to differ considerably in fiber and nonfiber carbohydrate content as well as in natural (13)C enrichment. PMID:27344384

  9. Aperitif effects on gastric emptying: a crossover study using continuous real-time 13C breath test (BreathID System).

    PubMed

    Inamori, M; Iida, H; Endo, H; Hosono, K; Akiyama, T; Yoneda, K; Fujita, K; Iwasaki, T; Takahashi, H; Yoneda, M; Goto, A; Abe, Y; Kobayashi, N; Kubota, K; Nakajima, A

    2009-04-01

    The aim of this study was to determine whether there is a correlation between aperitif and gastric emptying. Ten healthy male volunteers participated in this randomized, two-way crossover study. Under two conditions (after drinking an aperitif versus not), the (13)C breath test was performed for 4 h with a liquid meal (200 kcal/200 ml) containing 100 mg (13)C acetate. We used 50 ml of umeshu as the aperitif. This is a traditional Japanese plum liqueur, and contains 7 ml alcohol (14%). In the aperitif group, T(1/2), T(lag), and T(peak) were significantly delayed [T(1/2) (132: 113-174) versus (112: 92-134) (P = 0.0069); T(lag) (80: 63-94) versus (55: 47-85) (P = 0.0069); and T(peak) (81: 62-96) versus (54: 34-84) (P = 0.0069), (median: range, aperitif versus control, min)]. Gastric emptying was significantly delayed in the aperitif group as compared with the control group. This study revealed that even a small amount of alcohol such as an aperitif may contribute to delayed gastric emptying. PMID:18688714

  10. /sup 13/C-/sup 13/C spin-spin coupling constants in structural investigations. II. Conformational structure of vinyl ethers

    SciTech Connect

    Krivdin, L.B.; Shcherbakov, V.V.; Bzhezovskii, V.M.; Kalabin, G.A.

    1986-10-10

    The /sup 13/C-/sup 13/C spin-spin coupling constants between the carbon nuclei of the vinyl group were measured for a series of vinyl ethers. It was established that the unshared electron pairs of the oxygen atom can make a substantial stereospecific contribution to the direct /sup 13/C-/sup 13/C constants of the adjacent nuclei. The observed effect was used to establish the conformational structure of the compounds.

  11. Strategy for Enhancement of (13)C-Photo-CIDNP NMR Spectra by Exploiting Fractional (13)C-Labeling of Tryptophan.

    PubMed

    Eisenreich, Wolfgang; Joshi, Monika; Illarionov, Boris; Kacprzak, Sylwia; Lukaschek, Michail; Kothe, Gerd; Budisa, Nediljko; Fischer, Markus; Bacher, Adelbert; Weber, Stefan

    2015-10-29

    The photo-CIDNP effect has proven to be useful to strongly enhance NMR signals of photochemically active proteins simply by irradiation with light. The evolving characteristic patterns of enhanced absorptive and emissive NMR lines can be exploited to elucidate the photochemistry and photophysics of light-driven protein reactions. In particular, by the assignment of (13)C NMR resonances, redox-active amino acids may be identified and thereby electron-transfer pathways unraveled, in favorable cases, even with (13)C at natural abundance. If signal enhancement is weak, uniform (13)C isotope labeling is traditionally applied to increase the signal strength of protein (13)C NMR. However, this typically leads to cross relaxation, which transfers light-induced nuclear-spin polarization to adjacent (13)C nuclei, thereby preventing an unambiguous analysis of the photo-CIDNP effect. In this contribution, two isotope labeling strategies are presented; one leads to specific but ubiquitous (13)C labeling in tryptophan, and the other is based on fractional isotope labeling affording sets of isotopologs with low probability of next-neighbor isotope accumulation within individual tryptophan molecules. Consequently, cross relaxation is largely avoided while the signal enhancement by (13)C enrichment is preserved. This results in significantly simplified polarization patterns that are easier to analyze with respect to the generation of light-generated nuclear-spin polarization. PMID:26244593

  12. 13C NMR Metabolomics: INADEQUATE Network Analysis

    PubMed Central

    Clendinen, Chaevien S.; Pasquel, Christian; Ajredini, Ramadan; Edison, Arthur S.

    2015-01-01

    The many advantages of 13C NMR are often overshadowed by its intrinsically low sensitivity. Given that carbon makes up the backbone of most biologically relevant molecules, 13C NMR offers a straightforward measurement of these compounds. Two-dimensional 13C-13C correlation experiments like INADEQUATE (incredible natural abundance double quantum transfer experiment) are ideal for the structural elucidation of natural products and have great but untapped potential for metabolomics analysis. We demonstrate a new and semi-automated approach called INETA (INADEQUATE network analysis) for the untargeted analysis of INADEQUATE datasets using an in silico INADEQUATE database. We demonstrate this approach using isotopically labeled Caenorhabditis elegans mixtures. PMID:25932900

  13. E-2-Benzylidenebenzocycloalkanones. IV. Studies on transmission of substituent effects on 13C NMR chemical shifts of E-2-(X-benzylidene)-1-tetralones, and -benzosuberones. Comparison with the 13C NMR data of chalcones and E-2-(X-benzylidene)-1-indanones

    NASA Astrophysics Data System (ADS)

    Perjési, Pál; Linnanto, Juha; Kolehmainen, Erkki; Ősz, Erzsébet; Virtanen, Elina

    2005-04-01

    Single substituent parameter (SSP) and dual substituent parameter (DSP) analyses were applied to study the transmission of substituent effects on selected 13C NMR chemical shifts of the cyclic chalcone analogues, E-2-(4'-X-benzylidene)-1-tetralones ( 2) and E-2-(4'-X-benzylidene)-1-benzosuberones ( 3). In order to study how the geometry of the cyclic chalcone analogues affects the transmission of substituent effects similar investigations with the respective chalcones ( 4) were also performed. The results obtained earlier with the five-membered analogue E-2-(4'-X-benzylidene)-1-indanones ( 1) were also involved in the comparisons. Geometry optimization of the unsubstituted 1a, 2a, 3a and 4a as well as the substituted 2 and 3 was performed by ab initio quantum chemical calculations. Both SSP and DSP analyses reflected that resonance effects contribute more to the chemical shift of C-α (C2), while inductive effects primarily affect that of C-β (C10) of the enone moiety of all the four series. This latter effect, however, is far not as pronounced as that of the former one. It was found that DSP analysis data ( ρF and ρR values) of transmission of substituent effects on the δC2 data can serve as a measure of choice to study the conformation (planarity) of the investigated enones in the four series.

  14. 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%.

  15. Sheep wool δ13C reveals no effect of grazing on the C3/C4 ratio of vegetation in the inner Mongolia-Mongolia border region grasslands.

    PubMed

    Auerswald, Karl; Wittmer, Max H O M; Tungalag, Radnaakhand; Bai, Yongfei; Schnyder, Hans

    2012-01-01

    We tested whether the abundance of C(4) vegetation in grasslands of the Mongolian plateau is influenced by grazing conditions. The analysis exploited the politically originated contrast that exists between Mongolia (low stocking rate, transhumant system) and the district of Inner Mongolia, China (high stocking rate, sedentary system). We estimated the proportion of C(4) carbon (P(C4)) in grazed vegetation from the relative carbon isotope ratio (δ(13)C) of sheep wool sampled from 298 annual shearings originating from 1996 to 2007. Annual stocking rates varying over time and between the districts of both countries were taken from regional statistics. The P(C4) pattern within the 0.7 million km(2) sampling area was geostatistically analyzed and related to stocking rates and temperature gradients. For similar climatic conditions, P(C4) was the same in both countries. Further, a unique relationship was found between P(C4) and July temperature on both sides of the border, which explained 71% of the pattern. Stocking rate and grazing system had no significant influences on present-day C(3)/C(4) abundance ratio. This finding suggests that recent changes in the C(3)/C(4) ratio of these grasslands are mainly a consequence of regional warming, not overgrazing. PMID:23029090

  16. /sup 13/C spin diffusion of adamantane

    SciTech Connect

    Bronniman, C.E.; Szeverenyi, N.M.; Maciel, G.E.

    1983-10-15

    Two-dimensional exchange spectroscopy of natural abundance /sup 13/C--/sup 13/C spin diffusion in solid adamantane illustrates the influence that /sup 13/C--/sup 1/H dipole--dipole coupling exerts on /sup 13/C spin diffusion by determining spectral overlap in the /sup 13/C system. 2D /sup 13/C spectra were obtained for several values of mixing time tau/sub m/ and compared with spectra calculated in the limit of nearest-neighbor coupling. Good agreement is obtained for short tau/sub m/, during which the equilibration of neighboring spins dominates. For longer tau/sub m/, slower spin diffusion that is not acounted for by the simple model is seen; after nearest-neighbor spins equilibrate, communication over larger distances produces further mixing. It is possible to modify spin diffusion rates by altering experimental conditions, e.g., magic-angle spinning, low-power /sup 1/H decoupling, or spin locking /sup 13/C in the rotating frame during tau/sub m/.

  17. Effects of climate on deer bone δ15N and δ13C: Lack of precipitation effects on δ15N for animals consuming low amounts of C 4 plants

    NASA Astrophysics Data System (ADS)

    Cormie, A. B.; Schwarcz, H. P.

    1996-11-01

    We have examined the relationship of bone collagen δ15N and δ13C to climatic variables, humidity, temperature, and amount of precipitation using fifty-nine specimens of North American white-tailed deer ( Odocoileus virginianus) from forty-six different locations. In previous studies of African mammals there was a significant correlation between bone collagen δ15N and local amount of precipitation. Results presented here similarly show an increase in δ15N with decreasing amount of precipitation but only for 25% of the animals, namely those consuming more than 10% C 4 plants. These animals also exhibited a significant correlation between δ13C and temperature which mirrors previous observations for grasses suggesting that these deer consume grasses during times of population and nutrient stress. In contrast, even in dry areas containing high proportions of C 4 grasses, the majority of the deer had consumed low amounts of C 4 plants and these deer did not have δ15N which correlate with amount of precipitation. Only when deer deviated from their normal feeding pattern by consuming C 4 plants or grasses did their δ15N correlate with amount of rainfall. For these animals, consumption of C 4 plants or grasses may signal conditions of water and nutrient stress. An increase in δ15N of bone collagen may result from combined effects from excretion of concentrated urine (to conserve water) and increased internal recycling of nitrogen (to conserve nitrogen).

  18. Determination of molecular structure of kerogens using 13C NMR spectroscopy: II. The effects of thermal maturation on kerogens from marine sediments

    NASA Astrophysics Data System (ADS)

    Patience, R. L.; Mann, A. L.; Poplett, I. J. F.

    1992-07-01

    Solid state 13C nuclear magnetic resonance (NMR) spectrometry has been used to analyse kerogens isolated from marine sediments, to obtain information about relative changes in average molecular structures with increases in thermal maturity. Three suites of samples, all of which vary from immature to mature with respect to petroleum generation, were investigated: (a) seven samples of the Cretaceous Brown Limestone Formation (BLF), Gulf of Suez; (b) six from the Miocene Monterey Formation (MF), California; (c) seven from the Upper Jurassic to Lower Cretaceous Kimmeridge Clay Formation (KCF), UK continental shelf (UKCS). Each NMR spectrum has been quantified in terms of fourteen different carbon types. The immature KCF samples have a somewhat higher initial aromaticity (f a) than immature representatives of the other two suites, perhaps due to a slightly greater terrestrial organic input. With increasing maturity, only a modest increase in f a occurs in all three suites, until petroleum generation commences. The latter results in a sharp increase in f a, because alkyl carbon types are progressively lost from kerogen. No preferential loss of particular alkyl carbon types is seen within the resolution of the method. The percentage of heteroatom-bonded carbon (to O or S) declines consistently with increasing maturation and prior to the onset of petroleum generation. The distribution of aromatic carbon types changes substantially with increasing maturity, in that the relative abundances of bridgehead (ring junction) and protonated aromatic carbons increase, whereas phenolic and alkylated aromatic carbon decline or remain roughly constant, respectively. The data acquired have been used to monitor the hydrogen budget during maturation. Firstly, aromatisation reactions seem to occur during petroleum generation (increasing aromaticity is not simply a concentration of existing aromatic carbon) and, secondly, sufficient or excess hydrogen is liberated during these reactions to

  19. 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.

  20. Effects of fish oil and starch added to a diet containing sunflower-seed oil on dairy goat performance, milk fatty acid composition and in vivo delta9-desaturation of [13C]vaccenic acid.

    PubMed

    Bernard, Laurence; Mouriot, Julien; Rouel, Jacques; Glasser, Frédéric; Capitan, Pierre; Pujos-Guillot, Estelle; Chardigny, Jean-Michel; Chilliard, Yves

    2010-08-01

    The potential benefits on human health have prompted an interest in developing nutritional strategies for specifically increasing rumenic acid (RA) in ruminant milk. The aims of the present study were to (i) compare two dietary treatments with lipid supplements on milk yield and composition, (ii) measure the in vivo delta9-desaturation of vaccenic acid (VA) to RA using 13C-labelled VA and (iii) determine the effect of the dietary treatments on this variable. Treatments were 90 g sunflower-seed oil (SO) per d or 60 g sunflower-seed oil and 30 g fish oil per d plus additional starch (SFO), in a grassland hay-based diet given to eight Alpine goats in a 2 x 2 cross-over design with 21 d experimental periods. Milk yield and composition were similar between treatments. Goats fed SFO had higher milk 6 : 0-16 : 0 concentration, lower milk sigmaC18 concentrations and showed no effect on milk VA and RA, compared with SO. At the end of the experiment, intravenous injection of 1.5 g [13C]VA followed by measurements of milk lipid 13C enrichment showed that in vivo 31.7 and 31.6 % of VA was delta9-desaturated into milk RA in the caprine with the SO and SFO treatments, respectively. The expression of genes encoding for delta9-desaturase (or stearoyl-CoA desaturase; SCD1, SCD5) in mammary tissues and four milk delta9-desaturation ratios were similar between treatments. In conclusion, the present study provides the first estimates of in vivo endogenous synthesis of RA (63-73 % of milk RA) from VA in goats, and shows no difference between the two lipid supplements compared. PMID:20307350

  1. The effects of Paraloid B-72 and Butvar B-98 treatment and organic solvent removal on δ(13)C, δ(15)N, and δ(18)O values of collagen and hydroxyapatite in a modern bone.

    PubMed

    France, Christine A M; Giaccai, Jennifer A; Doney, Charlotte R

    2015-06-01

    Stable isotopes in bones are a powerful tool for diet, provenance, climate, and physiological reconstructions, but necessarily require well-preserved specimens unaltered by postmortem diagenesis or conservation practices. This study examines the effects of Paraloid B-72 and Butvar B-98, two common consolidants used in field and museum conservation, on δ(13)C, δ(15)N, and δ(18)O values from bone collagen and hydroxyapatite. The effects of solvent removal (100% acetone, 100% ethanol, 9:1 acetone:xylenes, 9:1 ethanol:xylenes) and drying methods (ambient air, vacuum, oven drying at 80°C) were also examined to determine if bones treated with these consolidants can successfully be cleaned and used for stable isotope analyses. Results show that introduction of Paraloid B-72 or Butvar B-98 in 100% acetone or 100% ethanol, respectively, with subsequent removal by the same solvents and drying at 80°C facilitates the most successful removal of consolidants and solvents. The δ(13)C values in collagen, δ(15)N in collagen, δ(18)O in hydroxyapatite phosphate, and δ(13)C in hydroxyapatite structural carbonate were unaltered by treatments with Paraloid or Butvar and subsequent solvent removal. The δ(18)O in hydroxyapatite structural carbonate showed nonsystematic variability when bones were treated with Paraloid and Butvar, which is hypothesized to be a result of hydroxyl exchange when bones are exposed to consolidants in solution. It is therefore recommended that δ(18)O in hydroxyapatite structural carbonate should not be used in stable isotope studies if bones have been treated with Paraloid or Butvar. PMID:25639211

  2. Determination of the tautomeric equilibria of pyridoyl benzoyl β-diketones in the liquid and solid state through the use of deuterium isotope effects on (1)H and (13)C NMR chemical shifts and spin coupling constants.

    PubMed

    Hansen, Poul Erik; Borisov, Eugeny V; Lindon, John C

    2015-02-01

    The tautomeric equilibria for 2-pyridoyl-, 3-pyridoyl-, and 4-pyridoyl-benzoyl methane have been investigated using deuterium isotope effects on (1)H and (13)C chemical shifts both in the liquid and the solid state. Equilibria are established both in the liquid and the solid state. In addition, in the solution state the 2-bond and 3-bond J((1)H-(13)C) coupling constants have been used to confirm the equilibrium positions. The isotope effects due to deuteriation at the OH position are shown to be superior to chemical shift in determination of equilibrium positions of these almost symmetrical -pyridoyl-benzoyl methanes. The assignments of the NMR spectra are supported by calculations of the chemical shifts at the DFT level. The equilibrium positions are shown to be different in the liquid and the solid state. In the liquid state the 4-pyridoyl derivative is at the B-form (C-1 is OH), whereas the 2-and 3-pyridoyl derivatives are in the A-form. In the solid state all three compounds are on the B-form. The 4-pyridoyl derivative shows unusual deuterium isotope effects in the solid, which are ascribed to a change of the crystal structure of the deuteriated compound. PMID:24070650

  3. States of 13C with abnormal radii

    NASA Astrophysics Data System (ADS)

    Demyanova, A. S.; Ogloblin, A. A.; Danilov, A. N.; Goncharov, S. A.; Belyaeva, T. L.; Sobolev, Yu. G.; Khlebnikov, S. V.; Burtebaev, N.; Trzaska, W.; Heikkinen, P.; Tyurin, G. P.; Janseitov, D.; Gurov, Yu. B.

    2016-05-01

    Differential cross-sections of the elastic and inelastic 13C + α scattering were measured at E(α) = 90 MeV. The root mean-square radii() of 13C nucleus in the states: 8.86 (1/2-), 3.09 (1/2+) and 9.90 (3/2-) MeV were determined by the Modified diffraction model (MDM). The radii of the first two levels are enhanced compared to that of the ground state of 13C, confirming the suggestion that the 8.86 MeV state is an analogue of the Hoyle state in 12C and the 3.09 MeV state has a neutron halo. Some indications to the abnormally small size of the 9.90 MeV state were obtained.

  4. Coupling tree-ring delta13C and delta15N to test the effect of fertilization on mature Douglas-fir (Pseudotsuga menziesii var. glauca) stands across the Interior northwest, USA.

    PubMed

    Balster, Nick J; Marshall, John D; Clayton, Murray

    2009-12-01

    Nitrogen (N) fertilization causes long-term increases in biomass production in many N-limited forests around the world, but the mechanistic basis underlying the increase is often unclear. One possibility, especially in summer-dry climates, is that N fertilization increases the efficiency with which a finite water supply is consumed to support photosynthesis. This increase is achieved by a reduction in the canopy-integrated concentration of internal CO(2) and thus discrimination against (13)C. We used stable isotopes of carbon (delta(13)C) in tree rings to experimentally test the physiological impact of N fertilization on mature Douglas-fir (Pseudotsuga menziesii Franco var. glauca) stands across the geographic extent of the Intermountain West, USA. The concentration and the stable isotopes of N (delta(15)N) in tree rings were also used to assess the presence and activity of fertilizer N. We hypothesized that N fertilization would (i) increase delta(15)N and N concentration of stemwood relative to non-fertilized stands and (ii) increase stemwood delta(13)C as photosynthetic gas exchange responded to the additional N. This experiment included two rates of urea addition, 178 kg ha(-1) (low) and 357 kg ha(-1) (high), which were applied twice over a 6-year interval bracketed by the 18 years of wood production measured in this study. Foliar N concentrations measured the year after each fertilization treatment suggest that the fertilizer N had been assimilated by the trees (P < 0.001). The N fertilization significantly enriched stemwood delta(15)N by 1.3 per thousand at the low fertilization rate and by 2.4 per thousand at the high rate (P < 0.001) despite variation in soil N between sites. However, we found no significant effect of the N fertilizer on delta(13)C of the annual rings (P = 0.76). These data lead us to suggest that alternative mechanisms underlie the growth response to fertilizer, i.e., increase in canopy area and shifts in biomass allocation. PMID:19855101

  5. From Natural History to the Nuclear Shell Model: Chemical Thinking in the Work of Mayer, Haxel, Jensen, and Suess

    NASA Astrophysics Data System (ADS)

    Johnson, Karen E.

    2004-09-01

    In 1949 the nuclear shell model was discovered simultaneously in the United States and Germany. Both discoveries were the result of a nuclear scientist looking at geochemical and nuclear data with the eyes of a chemist. Maria Goeppert Mayer in the United States and Hans Suess in Germany both brought a chemist’s perspective to the problem; the theoretical solution was subsequently supplied independently by Mayer and Hans Jensen.

  6. Effects of boron nutrition and water stress on nitrogen fixation, seed d15N and d13C daynamics, and seed composition in soybean cultivars differing in maturities

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water stress is a major abiotic stress factor, resulting in a major yield loss and poor seed quality. Little information is available on the effects of B nutrition on seed composition under water stress. Therefore, the objective of the current research was to investigate the effects of foliar B nutr...

  7. Effects of foliar boron application on seed composition, cell wall boron, and seed delta 15N and delta 13C isotopes in soybean are influenced by water stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although the effect of foliar boron (B) application on yield and quality is well established for crops, limited information and controversial results still exist on the effects of foliar B application on soybean seed composition (seed protein, oil, fatty acids, and sugars). The objective of this res...

  8. Chemical composition of organic matter in a deep soil changed with a positive priming effect due to glucose addition as investigated by 13C NMR spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fresh organic carbon becomes more accessible to subsoil following losses of surface soil or deep incorporation of crop residues, which can cause the priming effect and influence the quality and quantity of soil organic C (SOC) in subsoil. Chemical compositions of SOC in subsoil (1.0-1.2 m) without ...

  9. Soil phosphorus and water effects on growth, nutrient and carbohydrate concentrations, d13C, and nodulation of mimosa (Albizia julibrissin Durz.) on a highly weathered soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Growth and physiological performance of multipurpose tree species can be severely constrained by nutrient shortages such as of phosphorus (P) in highly-weathered soils. Limitations to plant growth are accentuated by seasonal dry periods. We examined P fertilization and irrigation effects on growth...

  10. 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.

  11. Effect of organic carbon chemistry on sorption of atrazine and metsulfuron-methyl as determined by (13)C-NMR and IR spectroscopy.

    PubMed

    Dutta, Anirban; Mandal, Abhishek; Manna, Suman; Singh, S B; Berns, Anne E; Singh, Neera

    2015-10-01

    Soil organic matter (SOM) content is the major soil component affecting pesticide sorption. However, recent studies have highlighted the fact that it is not the total carbon content of the organic matter, but its chemical structure which have a profound effect on the pesticide's sorption. In the present study, sorption of atrazine and metsulfuron-methyl herbicides was studied in four SOM fractions viz. commercial humic acid, commercial lignin, as well as humic acid and humin extracted from a compost. Sorption data was fitted to the Freundlich adsorption equation. In general, the Freundlich slope (1/n) values for both the herbicides were <1. Except for atrazine sorption on commercial humic acid, metsulfuron-methyl was more sorbed. Desorption results suggested that atrazine was more desorbed than metsulfuron-methyl. Lignin, which showed least sorption of both the herbicides, showed minimum desorption. Sorption of atrazine was best positively correlated with the alkyl carbon (adjusted R (2) = 0.748) and carbonyl carbon (adjusted R (2) = 0.498) but, their effect was statistically nonsignificant (P = 0.05). Metsulfuron-methyl sorption showed best positive correlation with carbonyl carbon (adjusted R (2) = 0.960; P = 0.05) content. Sorption of both the herbicides showed negative correlation with O/N-alkyl carbon. Correlation of herbicide's sorption with alkyl and carbonyl carbon content of SOM fractions suggested their contribution towards herbicide sorption. But, sorption of metsulfuron-methyl, relatively more polar than atrazine, was mainly governed by the polar groups in SOM. IR spectra showed that H-bonds and charge-transfer bonds between SOM fraction and herbicides probably operated as mechanisms of adsorption. PMID:26353968

  12. /sup 13/C NMR study of effects of fasting and diabetes on the metabolism of pyruvate in the tricarboxylic acid cycle and of the utilization of pyruvate and ethanol in lipogenesis in perfused rat liver

    SciTech Connect

    Cohen, S.M.

    1987-01-27

    /sup 13/C NMR has been used to study the competition of pyruvate dehydrogenase with pyruvate carboxylase for entry of pyruvate into the tricarboxylic acid (TCA) cycle in perfused liver from streptozotocin-diabetic and normal donor rats. The relative proportion of pyruvate entering the TCA cycle by these two routes was estimated from the /sup 13/C enrichments at the individual carbons of glutamate when (3-/sup 13/C)alanine was the only exogenous substrate present. In this way, the proportion of pyruvate entering by the pyruvate dehydrogenase route relative to the pyruvate carboxylase route was determined to be 1:1.2 +/- 0.1 in liver from fed controls, 1:7.7 +/- 2 in liver from 24-fasted controls, and 1:2.6 +/- 0.3 in diabetic liver. Pursuant to this observation that conversion of pyruvate to acetyl coenzyme A (acetyl-CoA) was greatest in perfused liver from fed controls, the incorporation of /sup 13/C label into fatty acids was monitored in this liver preparation. With the exception of the repeating methylene carbons, fatty acyl carbons labeled by (1-/sup 13/C)acetyl-CoA (from (2-/sup 13/C)pyruvate) gave rise to resonances distinguishable on the basis of chemical shift from those observed when label was introduced by (3-/sup 13/C)alanine plus (2-/sup 13/C)ethanol, which are converted to (2-/sup 13/C)acetyl-CoA. Thus, measurement of /sup 13/C enrichment at several specific sites in the fatty acyl chains in time-resolved spectra of perfused liver offers a novel way of monitoring the kinetics of the biosynthesis of fatty acids. In addition to obtaining the rate of lipogenesis, it was possible to distinguish the contributions of chain elongation from those of the de novo synthesis pathway and to estimate the average chain length of the /sup 13/C-labeled fatty acids produced.

  13. Model-free estimation of the effective correlation time for C-H bond reorientation in amphiphilic bilayers: 1H-13C solid-state NMR and MD simulations

    NASA Astrophysics Data System (ADS)

    Ferreira, Tiago Mendes; Ollila, O. H. Samuli; Pigliapochi, Roberta; Dabkowska, Aleksandra P.; Topgaard, Daniel

    2015-01-01

    Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 μs. The reorientational dynamics of the C-H bonds is conventionally verified by measurements of 13C or 2H nuclear magnetic resonance (NMR) longitudinal relaxation rates R1, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomically resolved model-free estimation of the C-H bond effective reorientational correlation time τe, which includes contributions from the entire range of all-atom MD timescales and that can be calculated directly from the MD trajectories. The approach is based on measurements of 13C R1 and R1ρ relaxation rates, as well as 1H-13C dipolar couplings, and is applicable to anisotropic liquid crystalline lipid or surfactant systems using a conventional solid-state NMR spectrometer and samples with natural isotopic composition. The procedure is demonstrated on a fully hydrated lamellar phase of 1-palmitoyl-2-oleoyl-phosphatidylcholine, yielding values of τe from 0.1 ns for the methyl groups in the choline moiety and at the end of the acyl chains to 3 ns for the g1 methylene group of the glycerol backbone. MD simulations performed with a widely used united-atom force-field reproduce the τe-profile of the major part of the acyl chains but underestimate the dynamics of the glycerol backbone and adjacent molecular segments. The measurement of experimental τe-profiles can be used to study subtle effects on C-H bond reorientational motions in anisotropic liquid crystals, as well as to validate the C-H bond reorientation dynamics predicted in MD simulations of amphiphilic bilayers such as lipid membranes.

  14. Accurate determinations of one-bond 13C-13C couplings in 13C-labeled carbohydrates

    NASA Astrophysics Data System (ADS)

    Azurmendi, Hugo F.; Freedberg, Darón I.

    2013-03-01

    Carbon plays a central role in the molecular architecture of carbohydrates, yet the availability of accurate methods for 1DCC determination has not been sufficiently explored, despite the importance that such data could play in structural studies of oligo- and polysaccharides. Existing methods require fitting intensity ratios of cross- to diagonal-peaks as a function of the constant-time (CT) in CT-COSY experiments, while other methods utilize measurement of peak separation. The former strategies suffer from complications due to peak overlap, primarily in regions close to the diagonal, while the latter strategies are negatively impacted by the common occurrence of strong coupling in sugars, which requires a reliable assessment of their influence in the context of RDC determination. We detail a 13C-13C CT-COSY method that combines a variation in the CT processed with diagonal filtering to yield 1JCC and RDCs. The strategy, which relies solely on cross-peak intensity modulation, is inspired in the cross-peak nulling method used for JHH determinations, but adapted and extended to applications where, like in sugars, large one-bond 13C-13C couplings coexist with relatively small long-range couplings. Because diagonal peaks are not utilized, overlap problems are greatly alleviated. Thus, one-bond couplings can be determined from different cross-peaks as either active or passive coupling. This results in increased accuracy when more than one determination is available, and in more opportunities to measure a specific coupling in the presence of severe overlap. In addition, we evaluate the influence of strong couplings on the determination of RDCs by computer simulations. We show that individual scalar couplings are notably affected by the presence of strong couplings but, at least for the simple cases studied, the obtained RDC values for use in structural calculations were not, because the errors introduced by strong couplings for the isotropic and oriented phases are very

  15. 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.

  16. Cryoreduction EPR and 13C, 19F ENDOR study of substrate-bound substates and solvent kinetic isotope effects in the catalytic cycle of cytochrome P450cam and its T252A mutant.

    PubMed

    Kim, Sun Hee; Yang, Tran-Chin; Perera, Roshan; Jin, Shengxi; Bryson, Thomas A; Sono, Masanori; Davydov, Roman; Dawson, John H; Hoffman, Brian M

    2005-11-01

    We recently used cryoreduction EPR/ENDOR techniques to show that a substrate can modulate the properties of both the monooxygenase active-oxygen intermediates and of the proton-delivery network which encompasses them. In the present report we use Q-band pulsed 19F ENDOR (Mims 3-pulse sequence) to examine the substrate binding geometries of camphor, through use of the 5,5'--difluorocamphor, and 13C ENDOR to examine the binding of 5-methylenyl camphor labeled with 13C at C11. These probes are examined in multiple states of the catalytic cycle of P450cam and its T252A mutant. As part of this investigation we further report a new cryoreduction reaction, the reduction of a ferroheme to the EPR-visible Fe(I) state, and use it to probe the substrate binding to the EPR-silent ferroheme state. Finally we report the solvent kinetic isotope effect on the decay of the camphor complex of the hydroperoxo-ferric intermediate, the first such measurement on an individual step within the P450cam reaction cycle. Following reduction of oxyferrous-P450cam, this step is the rate-limiting step in camphor hydroxylation, and its solv-KIE of 1.8 at 190 K establishes that it involves activation of the hydroperoxo moiety by transfer of the 'second' proton of catalysis. We suggest that the finding that the heme pocket can exist in multiple substates, including multiple substrate binding locations, even in P450cam, along with the established possibility that the hydroperoxo-ferriheme intermediate can react with substrate, may explain the formation of multiple products by P450s. PMID:16234926

  17. Performance evaluation of quantitative adiabatic (13)C NMR pulse sequences for site-specific isotopic measurements.

    PubMed

    Thibaudeau, Christophe; Remaud, Gérald; Silvestre, Virginie; Akoka, Serge

    2010-07-01

    (2)H/(1)H and (13)C/(12)C site-specific isotope ratios determined by NMR spectroscopy may be used to discriminate pharmaceutically active ingredients based on the synthetic process used in production. Extending the Site-specific Natural Isotope Fractionation NMR (SNIF-NMR) method to (13)C is highly beneficial for complex organic molecules when measurements of (2)H/(1)H ratios lead to poorly defined molecular fingerprints. The current NMR methodology to determine (13)C/(12)C site-specific isotope ratios suffers from poor sensitivity and long experimental times. In this work, several NMR pulse sequences based on polarization transfer were evaluated and optimized to measure precise quantitative (13)C NMR spectra within a short time. Adiabatic 180 degrees (1)H and (13)C pulses were incorporated into distortionless enhancement by polarization transfer (DEPT) and refocused insensitive nuclei enhanced by polarization transfer (INEPT) to minimize the influence of 180 degrees pulse imperfections and of off-resonance effects on the precision of the measured (13)C peak areas. The adiabatic DEPT sequence was applied to draw up a precise site-specific (13)C isotope profile of ibuprofen. A modified heteronuclear cross-polarization (HCP) experiment featuring (1)H and (13)C spin-locks with adiabatic 180 degrees pulses is also introduced. This sequence enables efficient magnetization transfer across a wide (13)C frequency range although not enough for an application in quantitative (13)C isotopic analysis. PMID:20527737

  18. The phenomenology of optically pumped 13C NMR in diamond at 7.05 T: Room temperature polarization, orientation dependence, and the effect of defect concentration on polarization dynamics

    NASA Astrophysics Data System (ADS)

    Scott, Eric; Drake, Melanie; Reimer, Jeffrey A.

    2016-03-01

    Room temperature optical illumination of NV- imbibed single crystal diamonds with a 532 nm laser produces 13C polarization enhancements up to 200 times greater than that of the thermal equilibrium value at 7.05 T. We report high field NV- mediated 13C polarization as a function of the number and type (NV- and P1) of defects in commercially available diamonds. Surprisingly, both positive and negative 13C polarizations are observed depending on the orientation of the crystal with respect to the external magnetic field and the electric field vector of the optical illumination. The data reported herein cannot be explained by a previously proposed mechanism.

  19. Photosynthesis and sup 13 C/ sup 12 C ratios in Amazonian rain forests

    SciTech Connect

    Van Der Merwe, N.J. ); Medina, E. )

    1989-05-01

    Measurements are reported of {sup 13}C/{sup 12}C ratios for air CO{sub 2} at different heights in two Amazonian rain forests. CO{sub 2} emitted from the forest floor is severely depleted in {sup 13}C which produces isotopically light source air throughout the forest. Air {delta}{sup 13}C values vary very little with height above ground, but are about 5 to 6{per thousand} more negative than the open atmosphere. CO{sub 2} recycling under the canopy depletes all leaf {delta}{sup 13}C values by a like amount. Additional factors further deplete leaf {delta}{sup 13}C values by 4 to 5{per thousand} at ground level; this effect decreases with height to zero in the upper canopy, yielding a gradient in {delta}{sup 13}C values.

  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. A large metabolic carbon contribution to the δ 13C record in marine aragonitic bivalve shells

    NASA Astrophysics Data System (ADS)

    Gillikin, David P.; Lorrain, Anne; Meng, Li; Dehairs, Frank

    2007-06-01

    It is well known that the incorporation of isotopically light metabolic carbon (C M) significantly affects the stable carbon isotope (δ 13C) signal recorded in biogenic carbonates. This can obscure the record of δ 13C of seawater dissolved inorganic carbon (δ 13C DIC) potentially archived in the shell carbonate. To assess the C M contribution to Mercenaria mercenaria shells collected in North Carolina, USA, we sampled seawater δ 13C DIC, tissue, hemolymph and shell δ 13C. All shells showed an ontogenic decrease in shell δ 13C, with as much as a 4‰ decrease over the lifespan of the clam. There was no apparent ontogenic change in food source indicated by soft tissue δ 13C values, therefore a change in the respired δ 13C value cannot be the cause of this decrease. Hemolymph δ 13C, on the other hand, did exhibit a negative relationship with shell height indicating that respired CO 2 does influence the δ 13C value of internal fluids and that the amount of respired CO 2 is related to the size or age of the bivalve. The percent metabolic C incorporated into the shell (%C M) was significantly higher (up to 37%, with a range from 5% to 37%) than has been found in other bivalve shells, which usually contain less than 10%C M. Interestingly, the hemolymph did contain less than 10%C M, suggesting that complex fractionation might occur between hemolymph and calcifying fluids. Simple shell biometrics explained nearly 60% of the observed variability in %C M, however, this is not robust enough to predict %C M for fossil shells. Thus, the metabolic effect on shell δ 13C cannot easily be accounted for to allow reliable δ 13C DIC reconstructions. However, there does seem to be a common effect of size, as all sites had indistinguishable slopes between the %C M and shell height (+0.19% per mm of shell height).

  2. Using the δ13C of Leaf Sugars to Examine the Effects of Changing the Onset or Duration of the Heatwave Season in a Widespread California Native Shrub, Heteromeles arbutifolia

    NASA Astrophysics Data System (ADS)

    Shuldman, M. I.; Dawson, T. E.

    2009-12-01

    The length of the “heatwave” season in California (CA) is predicted to increase. It is uncertain, however, if the heatwave season will start earlier or end later. In this study we examined the effect of a spring heatwave on the native shrub Heteromeles arbutifolia. We hypothesized that plants experiencing a heatwave in the spring, when soil water availability is high and plants are acclimated to lower temperatures, will use evaporative cooling to reduce leaf temperatures. Alternatively, we hypothesized that when plants are experiencing a combination of soil drought and high temperatures in summer they will not be able to use evaporative cooling due to the lack of available water. We used both full grown shrubs and plants that had regrown their canopies following a fire five years prior (resprouts). Measurements were made in spring under pre-heatwave and two days later under heatwave conditions and then monthly into the summer drought. During the spring heatwave air temperature was approximately 5°C higher than the pre-heatwave day and there was a 40% increase in vapor pressure deficit. At the same time, air temperature within plants canopies and leaf temperatures were not significantly different (or in some cases, cooler) from the previous pre-heatwave day. During the heatwave there was a significant increase in stomatal conductance to water vapor in early morning (8:30 AM) in both types on plants, however, the resprouts doubled their conductance compared to the previous pre-heatwave day. There was approximately a 1‰ difference of midday δ13C of leaf sugars before (-24.2‰ ± 0.2) compared to during the heatwave (-25.4‰ ±0.4). Within a plant type we saw no difference in the δ13C of leaf sugars, and therefore no difference in calculated ci/ca, between April 2009 and June 2009. Throughout this period ci/ca stayed constant as conductance decreased, suggesting photosynthesis and conductance were declining in concert. In July we observed significantly lower

  3. Model-free estimation of the effective correlation time for C–H bond reorientation in amphiphilic bilayers: {sup 1}H–{sup 13}C solid-state NMR and MD simulations

    SciTech Connect

    Ferreira, Tiago Mendes; Ollila, O. H. Samuli; Pigliapochi, Roberta; Dabkowska, Aleksandra P.; Topgaard, Daniel

    2015-01-28

    Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 μs. The reorientational dynamics of the C–H bonds is conventionally verified by measurements of {sup 13}C or {sup 2}H nuclear magnetic resonance (NMR) longitudinal relaxation rates R{sub 1}, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomically resolved model-free estimation of the C–H bond effective reorientational correlation time τ{sub e}, which includes contributions from the entire range of all-atom MD timescales and that can be calculated directly from the MD trajectories. The approach is based on measurements of {sup 13}C R{sub 1} and R{sub 1ρ} relaxation rates, as well as {sup 1}H−{sup 13}C dipolar couplings, and is applicable to anisotropic liquid crystalline lipid or surfactant systems using a conventional solid-state NMR spectrometer and samples with natural isotopic composition. The procedure is demonstrated on a fully hydrated lamellar phase of 1-palmitoyl-2-oleoyl-phosphatidylcholine, yielding values of τ{sub e} from 0.1 ns for the methyl groups in the choline moiety and at the end of the acyl chains to 3 ns for the g{sub 1} methylene group of the glycerol backbone. MD simulations performed with a widely used united-atom force-field reproduce the τ{sub e}-profile of the major part of the acyl chains but underestimate the dynamics of the glycerol backbone and adjacent molecular segments. The measurement of experimental τ{sub e}-profiles can be used to study subtle effects on C–H bond reorientational motions in anisotropic liquid crystals, as well as to validate the C–H bond reorientation dynamics predicted in MD

  4. Towards hyperpolarized 13C-succinate imaging of brain cancer

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Pratip; Chekmenev, Eduard Y.; Perman, William H.; Harris, Kent C.; Lin, Alexander P.; Norton, Valerie A.; Tan, Chou T.; Ross, Brian D.; Weitekamp, Daniel P.

    2007-05-01

    We describe a novel 13C enriched precursor molecule, sodium 1- 13C acetylenedicarboxylate, which after hydrogenation by PASADENA (Parahydrogen and Synthesis Allows Dramatically Enhanced Nuclear Alignment) under controlled experimental conditions, becomes hyperpolarized 13C sodium succinate. Fast in vivo 3D FIESTA MR imaging demonstrated that, following carotid arterial injection, the hyperpolarized 13C-succinate appeared in the head and cerebral circulation of normal and tumor-bearing rats. At this time, no in vivo hyperpolarized signal has been localized to normal brain or brain tumor. On the other hand, ex vivo samples of brain harvested from rats bearing a 9L brain tumor, 1 h or more following in vivo carotid injection of hyperpolarized 13C sodium succinate, contained significant concentrations of the injected substrate, 13C sodium succinate, together with 13C maleate and succinate metabolites 1- 13C-glutamate, 5- 13C-glutamate, 1- 13C-glutamine and 5- 13C-glutamine. The 13C substrates and products were below the limits of NMR detection in ex vivo samples of normal brain consistent with an intact blood-brain barrier. These ex vivo results indicate that hyperpolarized 13C sodium succinate may become a useful tool for rapid in vivo identification of brain tumors, providing novel biomarkers in 13C MR spectral-spatial images.

  5. 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.

  6. 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.

  7. Adult-onset hypothyroidism and the cerebral metabolism of (1,2-13C2) acetate as detected by 13C nuclear magnetic resonance.

    PubMed

    Chapa, F; Künnecke, B; Calvo, R; Escobar del Rey, F; Morreale de Escobar, G; Cerdán, S

    1995-01-01

    The effects of adult-onset hypothyroidism on the metabolic compartmentation of the cerebral tricarboxylic acid cycle and the gamma-aminobutyric acid (GABA) shunt have been investigated by 13C nuclear magnetic resonance spectroscopy. Rats thyroidectomized as adults and age-matched controls were infused in the right jugular vein with unlabeled or (1,2-13C2) acetate solutions for 60 min. At the end of the infusion, the brains were frozen in situ and perchloric acid extracts were prepared and analyzed by 13C nuclear magnetic resonance and reverse-phase HPLC. Thyroidectomized animals showed a decrease in the incorporation of 13C from (1,2-13C2) acetate in cerebral metabolites and an increase in the concentrations of unlabeled glutamate and GABA. Computer-assisted interpretation of the 13C multiplets observed for the carbons of glutamate, glutamine, and GABA indicated that adult-onset hypothyroidism produced 1) a decrease in the contribution of infused (1,2-13C2) acetate to the glial tricarboxylic acid cycle; 2) an increase in the contribution of unlabeled acetyl-CoA to the neuronal tricarboxylic acid cycle; and 3) impairments in the exchange of glutamate, glutamine, and GABA between the neuronal and glial compartments. Despite the fact that the adult brain has often been considered metabolically unresponsive to thyroid hormone status, present results show metabolic alterations in the neuronal and glial compartments that are reversible with substitution therapy. PMID:7828544

  8. 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.

  9. 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...

  10. 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

  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. Eduard Suess (1831 1914) et sa fresque mondiale La face de la Terre, deuxième tentative de tectonique globale

    NASA Astrophysics Data System (ADS)

    Durand-Delga, Michel; Seidl, Johannes

    2007-01-01

    The global synthesis of Suess, Das Antlitz der Erde (1883-1909), translated and augmented as La face de la Terre, replaces Élie de Beaumont's theory of 'upheavals', rejected by the end of the century. Although Suess' theory is also based upon the alleged cooling of the Earth, it differs on significant points such as the following: ( i) mountain belts are not symmetrical, they result from tangential push directed towards their foreland; ( ii) their bends result from their accommodation against older rigid blocks; ( iii) the 'Caledonian belt' has been followed by the 'Variscan', in turn followed by the 'Alpides' (see Marcel Bertrand); ( iv) the oceans formed by foundering of their basement at varied epochs, and their progressive infilling resulted in the worldwide 'eustatic' transgressions; ( v) the peri-Pacific 'island arcs' move toward the Pacific Ocean, which is the oldest one. Besides a coherent vision of the development of the Earth, integrating the early concepts of 'mobilism', Suess coined many currently used geological terms (Tethys, Gondwana, etc.). Suess, at this time authoritative the world over, was a member of the 'Académie des sciences' of Paris.

  13. 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

  14. The cluster and single-particle states in 13C (α,α)13C reactions

    NASA Astrophysics Data System (ADS)

    Mynbayev, N. A.; Nurmukhanbetova, A. K.; Goldberg, V. Z.; Rogachev, G. V.; Golovkov, M. S.; Koloberdin, M.; Ivanov, I.; Nauruzbayev, D. K.; Berdibek, Sh S.; Rakhymzhanov, A. M.; Tribble, R. E.

    2016-06-01

    The excitation functions of elastic scattering of 13C on alpha particle have been measured using the thick-target inverse kinematic method at the heavy ion DC-60 cyclotron. The helium gas was used as a target and also as a degrader to stop the beam. New data (including 180°degree) of the resonances close to the threshold in 17O have been obtained.

  15. Automated data processing of { 1H-decoupled} 13C MR spectra acquired from human brain in vivo

    NASA Astrophysics Data System (ADS)

    Shic, Frederick; Ross, Brian

    2003-06-01

    In clinical 13C infusion studies, broadband excitation of 200 ppm of the human brain yields 13C MR spectra with a time resolution of 2-5 min and generates up to 2000 metabolite peaks over 2 h. We describe a fast, automated, observer-independent technique for processing { 1H-decoupled} 13C spectra. Quantified 13C spectroscopic signals, before and after the administration of [1- 13C]glucose and/or [1- 13C]acetate in human subjects are determined. Stepwise improvements of data processing are illustrated by examples of normal and pathological results. Variation in analysis of individual 13C resonances ranged between 2 and 14%. Using this method it is possible to reliably identify subtle metabolic effects of brain disease including Alzheimer's disease and epilepsy.

  16. 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. PMID:25816077

  17. 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.

  18. 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.

  19. Ground-fire effects on the composition of dissolved and total organic matter in forest floor and soil solutions from Scots pine forests in Germany: new insights from solid state 13C NMR analysis

    NASA Astrophysics Data System (ADS)

    Näthe, Kerstin; Michalzik, Beate; Levia, Delphis; Steffens, Markus

    2016-04-01

    Fires represent an ecosystem disturbance and are recognized to seriously pertubate the nutrient budgets of forested ecosystems. While the effects of fires on chemical, biological, and physical soil properties have been intensively studied, especially in Mediterranean areas and North America, few investigations examined the effects of fire-induced alterations in the water-bound fluxes and the chemical composition of dissolved and particulate organic carbon and nitrogen (DOC, POC, DN, PN). The exclusion of the particulate organic matter fraction (0.45 μm < POM < 500 μm) potentially results in misleading inferences and budgeting gaps when studying the effects of fires on nutrient and energy fluxes. To our best knowledge, this is the first known study to present fire-induced changes on the composition of dissolved and total organic matter (DOM, TOM) in forest floor (FF) and soil solutions (A, B horizon) from Scots pine forests in Germany. In relation to control sites, we test the effects of low-severity fires on: (1) the composition of DOM and TOM in forest floor and soil solutions; and (2) the translocated amount of particulate in relation to DOC and DN into the subsoil. The project aims to uncover the mechanisms of water-bound organic matter transport along an ecosystem profile and its compositional changes following a fire disturbance. Forest floor and soil solutions were fortnightly sampled from March to December 2014 on fire-manipulated and control plots in a Scots pine forest in Central Germany. Shortly after the experimental duff fire in April 2014 pooled solutions samples were taken for solid-state 13C NMR spectroscopy to characterize DOM (filtered solution < 0.8μm pore size) and TOM in unfiltered solutions. Independent from fire manipulation, the composition of TOM was generally less aromatic (aromaticity index [%] according to Hatcher et al., 1981) with values between 18 (FF) - 25% (B horizon) than the DOM fraction with 23 (FF) - 27% (B horizon). For DOM

  20. Toward using delta13C of ecosystem respiration to monitor canopy physiology in complex terrain.

    PubMed

    Pypker, T G; Hauck, M; Sulzman, E W; Unsworth, M H; Mix, A C; Kayler, Z; Conklin, D; Kennedy, A M; Barnard, H R; Phillips, C; Bond, B J

    2008-12-01

    In 2005 and 2006, air samples were collected at the base of a Douglas-fir watershed to monitor seasonal changes in the delta13CO2 of ecosystem respiration (delta13C(ER)). The goals of this study were to determine whether variations in delta13C(ER) correlated with environmental variables and could be used to predict expected variations in canopy-average stomatal conductance (Gs). Changes in delta13C(ER) correlated weakly with changes in vapor pressure deficit (VPD) measured 0 and 3-7 days earlier and significantly with soil matric potential (psi(m)) (P value <0.02) measured on the same day. Midday G (s) was estimated using sapflow measurements (heat-dissipation method) at four plots located at different elevations within the watershed. Values of midday Gs from 0 and 3-7 days earlier were correlated with delta13C(ER), with the 5-day lag being significant (P value <0.05). To examine direct relationships between delta13C(ER) and recent Gs, we used models relating isotope discrimination to stomatal conductance and photosynthetic capacity at the leaf level to estimate values of stomatal conductance ("Gs-I") that would be expected if respired CO2 were derived entirely from recent photosynthate. We compared these values with estimates of Gs using direct measurement of transpiration at multiple locations in the watershed. Considering that the approach based on isotopes considers only the effect of photosynthetic discrimination on delta13C(ER), the magnitude and range in the two values were surprisingly similar. We conclude that: (1) delta13C(ER) is sensitive to variations in weather, and (2) delta13C(ER) potentially could be used to directly monitor average, basin-wide variations in Gs in complex terrain if further research improves understanding of how delta13C(ER) is influenced by post-assimilation fractionation processes. PMID:18839214

  1. Utilizing continuous measurements of delta^{13}C_r, delta18O_r, and net ecosystem exchange of CO_2 and H_2O to understand the effects of inter-annual variability in drought on ecosystem functioning

    NASA Astrophysics Data System (ADS)

    Osuna, J. L.; McDowell, N. G.; Shim, J. H.; Rahn, T.; Pockman, W.

    2011-12-01

    In the semi-arid Southwestern US, seasonal drought has strengthened in recent years due to both a decrease in winter precipitation and delayed onset of the summer monsoon. A process-based understanding of ecosystem response to increased drought stress is vital to predicting the long-term stability of semi-arid biomes. To understand the processes responsible for inter-annual and seasonal variability in net ecosystem carbon and water fluxes, we compared nearly continuous measurements of ecosystem scale respiration (R_e) from an eddy covariance system with the stable carbon and oxygen isotope signals in ecosystem respired CO_2 (delta^{13}C_r and delta^{18}O_r) measured continuously by a tunable diode laser spectrometer (TDL) sampling at various canopy heights at the same site. The study site, at Los Alamos National Laboratory, converted from pitilde{n}on juniper woodland to juniper woodland after over 90% of pitilde{n}ons died in 2002-2003 following multiple years of enhanced drought leaving a high necromass at the site. We analyzed the relationships between the Bowen ratio, delta^{18}O_r, daily and annual accumulated NEE, and delta^{13}C_r to understand the (de)coupling between the response of transpiration and respiration under varying degrees of drought stress. Additionally, we explored the variability in the lag and intensity of ecosystem response to precipitation pulses depending on antecedent conditions. The response of delta^{18}O_r was more consistent across years and seasons whereas variability in the contribution of autotrophic versus heterotrophic respiration appeared to cause differing responses of delta^{13}C_r to drought stress and precipitation pulses. This result was supported by the diurnal CO_2 and H_2O fluxes indicating nearly immediate transpirational water loss initiated by most precipitation pulses. Annual accumulated precipitation (versus pulse size) was a better indicator of delta^{13}C_ r response (i.e. relative contributions of autotrophic

  2. Non-stationary (13)C-metabolic flux ratio analysis.

    PubMed

    Hörl, Manuel; Schnidder, Julian; Sauer, Uwe; Zamboni, Nicola

    2013-12-01

    (13)C-metabolic flux analysis ((13)C-MFA) has become a key method for metabolic engineering and systems biology. In the most common methodology, fluxes are calculated by global isotopomer balancing and iterative fitting to stationary (13)C-labeling data. This approach requires a closed carbon balance, long-lasting metabolic steady state, and the detection of (13)C-patterns in a large number of metabolites. These restrictions mostly reduced the application of (13)C-MFA to the central carbon metabolism of well-studied model organisms grown in minimal media with a single carbon source. Here we introduce non-stationary (13)C-metabolic flux ratio analysis as a novel method for (13)C-MFA to allow estimating local, relative fluxes from ultra-short (13)C-labeling experiments and without the need for global isotopomer balancing. The approach relies on the acquisition of non-stationary (13)C-labeling data exclusively for metabolites in the proximity of a node of converging fluxes and a local parameter estimation with a system of ordinary differential equations. We developed a generalized workflow that takes into account reaction types and the availability of mass spectrometric data on molecular ions or fragments for data processing, modeling, parameter and error estimation. We demonstrated the approach by analyzing three key nodes of converging fluxes in central metabolism of Bacillus subtilis. We obtained flux estimates that are in agreement with published results obtained from steady state experiments, but reduced the duration of the necessary (13)C-labeling experiment to less than a minute. These results show that our strategy enables to formally estimate relative pathway fluxes on extremely short time scale, neglecting cellular carbon balancing. Hence this approach paves the road to targeted (13)C-MFA in dynamic systems with multiple carbon sources and towards rich media. PMID:23860906

  3. 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 from seawater (δ 13C ≈ 0%) or from respired CO2 within the coral host. The δ 13C of the carbon used in the formation of the underlying coral skeleton is fractionated as a result of both of these metabolic processes. Here I have pooled evidence from several field and tank experiments on the effect of photosynthesis and heterotrophy of coral skeletal δ 13C. In the experiments, decreases in light levels due to shading or depth resulted in a significant decrease in skeletal δ 13C in all species studied (Pavona gigantea, Pavona clavus, Porites compressa). Decreases in photosynthesis in bleached corals also resulted in a decrease in skeletal δ 13C compared to non-bleached corals growing under the same conditions and at the same location. Skeletal δ 13C also decreased at higher than normal light levels most likely due to photoinhibition. Thus, decreases in photosynthesis due to reduced light levels, due to bleaching-induced decreases in chlorophyll a concentrations, or due to photodamage-induced decreases in functional cholorphyll a, results in significant δ 13C decreases. Comprehensive interpretation of all of the data showed that changes in photosynthesis itself can drive the changes in δ 13C. In field experiments, the addition of natural concentrations of zooplankton to the diet resulted in decreases in skeletal δ 13C. Such a decrease was more pronounced with depth and in P. gigantea compared to P. clavus. In situ feeding experiments have since confirmed these findings. However under tank conditions with unaturally high feeding rates, enhanced nitrogen supply in the diet can disrupt the coral-algal symbiosis, stimlate zooxanthellae growth and photosynthesis, and cause an incrase in skeletal δ 13C. It is proposed that under

  4. Short-Term Effects of Tillage Practices on Soil Organic Carbon Turnover Assessed by δ13C Abundance in Particle-Size Fractions of Black Soils from Northeast China

    PubMed Central

    Zhang, Xiaoping; Chen, Xuewen

    2014-01-01

    The combination of isotope trace technique and SOC fractionation allows a better understanding of SOC dynamics. A five-year tillage experiment consisting of no-tillage (NT) and mouldboard plough (MP) was used to study the changes in particle-size SOC fractions and corresponding δ13C natural abundance to assess SOC turnover in the 0–20 cm layer of black soils under tillage practices. Compared to the initial level, total SOC tended to be stratified but showed a slight increase in the entire plough layer under short-term NT. MP had no significant impacts on SOC at any depth. Because of significant increases in coarse particulate organic carbon (POC) and decreases in fine POC, total POC did not remarkably decrease under NT and MP. A distinct increase in silt plus clay OC occurred in NT plots, but not in MP plots. However, the δ13C abundances of both coarse and fine POC increased, while those of silt plus clay OC remained almost the same under NT. The C derived from C3 plants was mainly associated with fine particles and much less with coarse particles. These results suggested that short-term NT and MP preferentially enhanced the turnover of POC, which was considerably faster than that of silt plus clay OC. PMID:25162052

  5. A Polymer-Based Magnetic Resonance Tracer for Visualization of Solid Tumors by 13C Spectroscopic Imaging

    PubMed Central

    Suzuki, Yoshikazu; Iida, Mitsuru; Miura, Iwao; Inubushi, Toshiro; Morikawa, Shigehiro

    2014-01-01

    Morphological imaging precedes lesion-specific visualization in magnetic resonance imaging (MRI) because of the superior ability of this technique to depict tissue morphology with excellent spatial and temporal resolutions. To achieve lesion-specific visualization of tumors by MRI, we investigated the availability of a novel polymer-based tracer. Although the 13C nucleus is a candidate for a detection nucleus because of its low background signal in the body, the low magnetic resonance sensitivity of the nucleus needs to be resolved before developing a 13C-based tracer. In order to overcome this problem, we enriched polyethylene glycol (PEG), a biocompatible polymer, with 13C atoms. 13C-PEG40,000 (13C-PEG with an average molecular weight of 40 kDa) emitted a single 13C signal with a high signal-to-noise ratio due to its ability to maintain signal sharpness, as was confirmed by in vivo investigation, and displayed a chemical shift sufficiently distinct from that of endogenous fat. 13C-PEG40,000 intravenously injected into mice showed long retention in circulation, leading to its effective accumulation in tumors reflecting the well-known phenomenon that macromolecules accumulate in tumors because of leaky tumor capillaries. These properties of 13C-PEG40,000 allowed visualization of tumors in mice by 13C spectroscopic imaging. These findings suggest that a technique based on 13C-PEG is a promising strategy for tumor detection. PMID:25007334

  6. sup 13 C and sup 18 O isotopic disequilibrium in biological carbonates: I. Patterns

    SciTech Connect

    McConnaughey, T. )

    1989-01-01

    Biological carbonates frequently precipitate out of {sup 18}O and {sup 13}C equilibrium with ambient waters. Two patterns of isotopic disequilibrium are particularly common. Kinetic disequilibria, so designated because they apparently result from kinetic isotope effects during CO{sub 2} hydration and hydroxylation, involve simultaneous depletions of {sup 18}O and {sup 13}C as large as 4{per thousand} and 10 to 15{per thousand}, respectively. Rapid skeletogenesis favors strong kinetic effects, and approximately linear correlations between skeletal {delta}{sup 18}O and {delta}{sup 13}C are common in carbonates showing mainly the kinetic pattern. Metabolic effects involve additional positive or negative modulation of skeletal {delta}{sup 13}C, reflecting changes in the {delta}{sup 13}C of dissolved inorganic carbon, caused mainly by photosynthesis and respiration. Kinetic isotope disequilibria tend to be fairly consistent in rapidly growing parts of photosynthetic corals, and time dependent isotopic variations therefore reflect changes in environmental conditions. {delta}{sup 18}O variations from Galapagos corals yields meaningful clues regarding seawater temperature, while {delta}{sup 13}C variations reflect changes in photosynthesis, modulated by cloudiness.

  7. 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...

  8. Simultaneous DNP enhancements of (1)H and (13)C nuclei: theory and experiments.

    PubMed

    Shimon, Daphna; Hovav, Yonatan; Kaminker, Ilia; Feintuch, Akiva; Goldfarb, Daniella; Vega, Shimon

    2015-05-01

    DNP on heteronuclear spin systems often results in interesting phenomena such as the polarization enhancement of one nucleus during MW irradiation at the "forbidden" transition frequencies of another nucleus or the polarization transfer between the nuclei without MW irradiation. In this work we discuss the spin dynamics in a four-spin model system of the form {ea-eb-((1)H,(13)C)}, with the Larmor frequencies ωa, ωb, ωH and ωC, by performing Liouville space simulations. This spin system exhibits the common (1)H solid effect (SE), (13)C cross effect (CE) and in addition high order CE-DNP enhancements. Here we show, in particular, the "proton shifted (13)C-CE" mechanism that results in (13)C polarization when the model system, at one of its (13)C-CE conditions, is excited by a MW field at the zero quantum or double quantum electron-proton transitions ωMW = ωa ± ωH and ωMW = ωb ± ωH. Furthermore, we introduce the "heteronuclear" CE mechanism that becomes efficient when the system is at one of its combined CE conditions |ωa - ωb| = |ωH ± ωC|. At these conditions, simulations of the four-spin system show polarization transfer processes between the nuclei, during and without MW irradiation, resembling the polarization exchange effects often discussed in the literature. To link the "microscopic" four-spin simulations to the experimental results we use DNP lineshape simulations based on "macroscopic" rate equations describing the electron and nuclear polarization dynamics in large spin systems. This approach is applied based on electron-electron double resonance (ELDOR) measurements that show strong (1)H-SE features outside the EPR frequency range. Simulated ELDOR spectra combined with the indirect (13)C-CE (iCE) mechanism, result in additional "proton shifted (13)C-CE" features that are similar to the experimental ones. These features are also observed experimentally in (13)C-DNP spectra of a sample containing 15 mM of trityl in a glass forming solution of

  9. Distinct fungal and bacterial δ13C signatures can drive the increase in soil δ13C with depth

    NASA Astrophysics Data System (ADS)

    Kohl, Lukas; Laganièrea, Jérôme; Edwards, Kate A.; Billings, Sharon A.; Morrill, Penny L.; Van Biesen, Geert; Ziegler, Susan E.

    2015-04-01

    Soil microbial biomass is a key precursor of soil organic carbon (SOC), and the enrichment in 13C during SOC diagenesis has been purported to be driven by increasing proportions of microbially derived SOC. Yet, little is known about how the δ13C of soil microbial biomass - and by extension the δ13C of microbial inputs to SOC - vary in space, time, or with the composition of the microbial community. Phospholipid fatty acids (PLFA) can be analyzed to measure the variation of the natural abundance δ13C values of both individual groups of microorganisms and the microbial community as a whole. Here, we show how variations of δ13CPLFA within the soil profile provides insight into C fluxes in undisturbed soils and demonstrate that distinct δ13C of fungal and bacterial biomass and their relative abundance can drive the increase of bulk δ13CSOC with depth. We studied the variation in natural abundance δ13C signatures of PLFA in podzolic soil profiles from mesic boreal forests in Atlantic Canada. Samples from the organic horizons (L,F,H) and the mineral (B; top 10 cm) horizons were analyzed for δ13C values of PLFA specific to fungi, G+ bacteria, or G- bacteria as proxies for the δ13C of the biomass of these groups, and for δ13C values of PLFA produced by a wide range of microorganisms (e.g. 16:0) as a proxy for the δ13C value of microbial biomass as a whole. Results were compared to fungi:bacteria ratios (F:B) and bulk δ13CSOC values. The δ13C values of group-specific PLFA were driven by differences among source organisms, with fungal PLFA consistently depleted (2.1 to 6.4‰) relative to and G+ and G- bacterial PLFA in the same sample. All group-specific PLFA, however, exhibited nearly constant δ13C values throughout the soil profile, apparently unaffected by the over 2.8‰ increase in δ13CSOC with depth from the L to B horizons. This indicates that bulk SOC poorly represents the substrates actually consumed by soil microorganisms in situ. Instead, our

  10. 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.

  11. Accurate quantitative 13C NMR spectroscopy: repeatability over time of site-specific 13C isotope ratio determination.

    PubMed

    Caytan, Elsa; Botosoa, Eliot P; Silvestre, Virginie; Robins, Richard J; Akoka, Serge; Remaud, Gérald S

    2007-11-01

    The stability over time (repeatability) for the determination of site-specific 13C/12C ratios at natural abundance by quantitative 13C NMR spectroscopy has been tested on three probes: enriched bilabeled [1,2-13C2]ethanol; ethanol at natural abundance; and vanillin at natural abundance. It is shown in all three cases that the standard deviation for a series of measurements taken every 2-3 months over periods between 9 and 13 months is equal to or smaller than the standard deviation calculated from 5-10 replicate measurements made on a single sample. The precision which can be achieved using the present analytical 13C NMR protocol is higher than the prerequisite value of 1-2 per thousand for the determination of site-specific 13C/12C ratios at natural abundance (13C-SNIF-NMR). Hence, this technique permits the discrimination of very small variations in 13C/12C ratios between carbon positions, as found in biogenic natural products. This observed stability over time in 13C NMR spectroscopy indicates that further improvements in precision will depend primarily on improved signal-to-noise ratio. PMID:17900175

  12. State-of-the-Art Direct 13C and Indirect 1H-[13C] NMR Spectroscopy In Vivo

    PubMed Central

    de Graaf, Robin A.; Rothman, Douglas L.; Behar, Kevin L.

    2013-01-01

    Carbon-13 NMR spectroscopy in combination with 13C-labeled substrate infusion is a powerful technique to measure a large number of metabolic fluxes non-invasively in vivo. It has been used to quantify glycogen synthesis rates, establish quantitative relationships between energy metabolism and neurotransmission and evaluate the importance of different substrates. All measurements can, in principle, be performed through direct 13C NMR detection or via indirect 1H-[13C] NMR detection of the protons attached to 13C nuclei. The choice for detection scheme and pulse sequence depends on the magnetic field strength, whereas substrate selection depends on the metabolic pathways that are studied. 13C NMR spectroscopy remains a challenging technique that requires several non-standard hardware modifications, infusion of 13C-labeled substrates and sophisticated processing and metabolic modeling. Here the various aspects of direct 13C and indirect 1H-[13C] NMR are reviewed with the aim of providing a practical guide. PMID:21919099

  13. 13C breath tests in infections and beyond.

    PubMed

    Kurpad, Anura V; Ajami, Alfred; Young, Vernon R

    2002-09-01

    Stable isotope labeled compounds are widely used as diagnostic probes in medicine. These diagnostic stable isotope probes are now being expanded in their scope, to provide precise indications of the presence or absence of etiologically significant change in metabolism due to a specific disease. This concept exploits a labeled tracer probe that is a specifically designed substrate of a "gateway" enzyme in a discrete metabolic pathway, whose turnover can be measured by monitoring unidirectional precursor product mass flow. An example of such a probe is the 13C-urea breath test, where labeled urea is given to patients with H. pylori infection. Another example of this kind of probe is used to study the tripeptide glutathione (glu-cys-gly, GSH), which is the most abundant cellular thiol, and protects cells from the toxic effects of reactive oxygen species. Within the gamma glutamyl cycle, 5-oxoproline (L-pyroglutamic acid) is a metabolite generated during GSH catabolism, and is metabolized to glutamic acid by 5-oxoprolinase. This enzyme can also utilize the substrate L-2-oxothiazolidone-4-carboxylate (OTC), to generate intracellular cysteine, which is beneficial to the cell. Thus, labeled (13C) OTC would, under enzymatic attack yield cysteine and 13CO2, and can thus track the state and capacity of glutathione metabolism. Similarly, stable isotope labeled probes can be used to track the activity of the rate of homocysteine clearance, lymphocyte CD26, and liver CYP (cytochrome P450) enzyme activity. In the future, these applications should be able to titrate, in vivo, the characteristics of various specific enzyme systems in the body and their response to stress or infection as well as to treatment regimes. PMID:12362798

  14. Parallel labeling experiments validate Clostridium acetobutylicum metabolic network model for (13)C metabolic flux analysis.

    PubMed

    Au, Jennifer; Choi, Jungik; Jones, Shawn W; Venkataramanan, Keerthi P; Antoniewicz, Maciek R

    2014-11-01

    In this work, we provide new insights into the metabolism of Clostridium acetobutylicum ATCC 824 obtained using a systematic approach for quantifying fluxes based on parallel labeling experiments and (13)C-metabolic flux analysis ((13)C-MFA). Here, cells were grown in parallel cultures with [1-(13)C]glucose and [U-(13)C]glucose as tracers and (13)C-MFA was used to quantify intracellular metabolic fluxes. Several metabolic network models were compared: an initial model based on current knowledge, and extended network models that included additional reactions that improved the fits of experimental data. While the initial network model did not produce a statistically acceptable fit of (13)C-labeling data, an extended network model with five additional reactions was able to fit all data with 292 redundant measurements. The model was subsequently trimmed to produce a minimal network model of C. acetobutylicum for (13)C-MFA, which could still reproduce all of the experimental data. The flux results provided valuable new insights into the metabolism of C. acetobutylicum. First, we found that TCA cycle was effectively incomplete, as there was no measurable flux between α-ketoglutarate and succinyl-CoA, succinate and fumarate, and malate and oxaloacetate. Second, an active pathway was identified from pyruvate to fumarate via aspartate. Third, we found that isoleucine was produced exclusively through the citramalate synthase pathway in C. acetobutylicum and that CAC3174 was likely responsible for citramalate synthase activity. These model predictions were confirmed in several follow-up tracer experiments. The validated metabolic network model established in this study can be used in future investigations for unbiased (13)C-flux measurements in C. acetobutylicum. PMID:25183671

  15. Multi-year estimates of plant and ecosystem 13C discrimination at AmeriFlux sites

    NASA Astrophysics Data System (ADS)

    Dang, X.; Lai, C.; Hollinger, D. Y.; Bush, S.; Randerson, J. T.; Law, B. E.; Schauer, A. J.; Ehleringer, J.

    2011-12-01

    We estimated plant and ecosystem 13C discrimination continuously at 8 AmeriFlux sites (Howland Forest, Harvard Forest, Wind River Forest, Rannells Prairie, Freeman Ranch, Chestnut Ridge, Metolius, and Marys River fir) over 8 years (2002-2009). We used an observation-based approach from weekly measurements of eddy covariance CO2 fluxes and their 13C/12C ratios to estimate photosynthetic 13C discrimination (△A) and respiration (δ13CR) on seasonal and interannual time scales. The coordinated, systematic flask sampling across the AmeriFlux subnetwork were used for cross-site synthesis of monthly flux estimates [Dang et al. Combining tower mixing ratio and community model data to estimate regional-scale net ecosystem carbon exchange by boundary layer inversion over 4 flux towers in the U.S.A., Journal of Geophysical Research-Biogeosciences, in press]. Here, we evaluated environmental factors that also influenced temporal variability in △A and δ13CR from daily to interannual time scales, comparing atmospheric 13C/12C measurements, leaf and needle organic matter, and tree ring cellulose. Across these major biomes that dominate the continent, we show differential ecophysiological responses to environmental stresses, among which water availability appeared to be a dominant factor. Our decadal measurement period provided robust estimates of atmospheric 13C discrimination by terrestrial ecosystems, but also suggest regions where enhanced monitoring efforts are required (e.g., 13C/12C emission from fire and urban metabolism; increased temporal resolution of 13C measurements in stress-sensitive ecosystems) to make atmospheric 13C/12C measurements an effective constraint for continental-scale assessments of the terrestrial carbon cycle.

  16. Directly detected 55Mn MRI: Application to phantoms for human hyperpolarized 13C MRI development

    PubMed Central

    von Morze, Cornelius; Carvajal, Lucas; Reed, Galen D.; Swisher, Christine Leon; Tropp, James; Vigneron, Daniel B.

    2014-01-01

    In this work we demonstrate for the first time directly detected manganese-55 (55Mn) MRI using a clinical 3T MRI scanner designed for human hyperpolarized 13C clinical studies with no additional hardware modifications. Due to the similar frequency of the 55Mn and 13C resonances, the use of aqueous permanganate for large, signal-dense, and cost-effective “13C” MRI phantoms was investigated, addressing the clear need for new phantoms for these studies. Due to 100% natural abundance, higher intrinsic sensitivity, and favorable relaxation properties, 55Mn MRI of aqueous permanganate demonstrates dramatically increased sensitivity over typical 13C phantom MRI, at greatly reduced cost as compared with large 13C-enriched phantoms. A large sensitivity advantage (22-fold) was demonstrated. A cylindrical phantom (d= 8 cm) containing concentrated aqueous sodium permanganate (2.7M) was scanned rapidly by 55Mn MRI in a human head coil tuned for 13C, using a balanced SSFP acquisition. The requisite penetration of RF magnetic fields into concentrated permanganate was investigated by experiments and high frequency electromagnetic simulations, and found to be sufficient for 55Mn MRI with reasonably sized phantoms. A sub-second slice-selective acquisition yielded mean image SNR of ~60 at 0.5cm3 spatial resolution, distributed with minimum central signal ~40% of the maximum edge signal. We anticipate that permanganate phantoms will be very useful for testing HP 13C coils and methods designed for human studies. PMID:25179135

  17. The paper trail of the 13C of atmospheric CO2 since the industrial revolution period

    NASA Astrophysics Data System (ADS)

    Yakir, Dan

    2011-07-01

    The 13C concentration in atmospheric CO2 has been declining over the past 150 years as large quantities of 13C-depleted CO2 from fossil fuel burning are added to the atmosphere. Deforestation and other land use changes have also contributed to the trend. Looking at the 13C variations in the atmosphere and in annual growth rings of trees allows us to estimate CO2 uptake by land plants and the ocean, and assess the response of plants to climate. Here I show that the effects of the declining 13C trend in atmospheric CO2 are recorded in the isotopic composition of paper used in the printing industry, which provides a well-organized archive and integrated material derived from trees' cellulose. 13C analyses of paper from two European and two American publications showed, on average, a - 1.65 ± 1.00‰ trend between 1880 and 2000, compared with - 1.45 and - 1.57‰ for air and tree-ring analyses, respectively. The greater decrease in plant-derived 13C in the paper we tested than in the air is consistent with predicted global-scale increases in plant intrinsic water-use efficiency over the 20th century. Distinct deviations from the atmospheric trend were observed in both European and American publications immediately following the World War II period.

  18. Metabolism of [13C5]hydroxyproline in vitro and in vivo: implications for primary hyperoxaluria

    PubMed Central

    Jiang, Juquan; Johnson, Lynnette C.; Knight, John; Callahan, Michael F.; Riedel, Travis J.; Holmes, Ross P.

    2012-01-01

    Hydroxyproline (Hyp) metabolism is a key source of glyoxylate production in the body and may be a major contributor to excessive oxalate production in the primary hyperoxalurias where glyoxylate metabolism is impaired. Important gaps in our knowledge include identification of the tissues with the capacity to degrade Hyp and the development of model systems to study this metabolism and how to suppress it. The expression of mRNA for enzymes in the pathway was examined in 15 different human tissues. Expression of the complete pathway was identified in liver, kidney, pancreas, and small intestine. HepG2 cells also expressed these mRNAs and enzymes and were shown to metabolize Hyp in the culture medium to glycolate, glycine, and oxalate. [18O]- and [13C5]Hyp were synthesized and evaluated for their use with in vitro and in vivo models. [18O]Hyp was not suitable because of an apparent tautomerism of [18O]glyoxylate between enol and hydrated forms, which resulted in a loss of isotope. [13C5]Hyp, however, was metabolized to [13C2]glycolate, [13C2]glycine, and [13C2]oxalate in vitro in HepG2 cells and in vivo in mice infused with [13C5]Hyp. These model systems should be valuable tools for exploring various aspects of Hyp metabolism and will be useful in determining whether blocking Hyp catabolism is an effective therapy in the treatment of primary hyperoxaluria. PMID:22207577

  19. In vivo 13 carbon metabolic imaging at 3T with hyperpolarized 13C-1-pyruvate.

    PubMed

    Kohler, S J; Yen, Y; Wolber, J; Chen, A P; Albers, M J; Bok, R; Zhang, V; Tropp, J; Nelson, S; Vigneron, D B; Kurhanewicz, J; Hurd, R E

    2007-07-01

    We present for the first time dynamic spectra and spectroscopic images acquired in normal rats at 3T following the injection of (13)C-1-pyruvate that was hyperpolarized by the dynamic nuclear polarization (DNP) method. Spectroscopic sampling was optimized for signal-to-noise ratio (SNR) and for spectral resolution of (13)C-1-pyruvate and its metabolic products (13)C-1-alanine, (13)C-1-lactate, and (13)C-bicarbonate. Dynamic spectra in rats were collected with a temporal resolution of 3 s from a 90-mm axial slab using a dual (1)H-(13)C quadrature birdcage coil to observe the combined effects of metabolism, flow, and T(1) relaxation. In separate experiments, spectroscopic imaging data were obtained during a 17-s acquisition of a 20-mm axial slice centered on the rat kidney region to provide information on the spatial distribution of the metabolites. Conversion of pyruvate to lactate, alanine, and bicarbonate occurred within a minute of injection. Alanine was observed primarily in skeletal muscle and liver, while pyruvate, lactate, and bicarbonate concentrations were relatively high in the vasculature and kidneys. In contrast to earlier work at 1.5 T, bicarbonate was routinely observed in skeletal muscle as well as the kidney and vasculature. PMID:17659629

  20. Sensitivity-enhanced IPAP experiments for measuring one-bond 13C '- 13C α and 13C α- 1H α residual dipolar couplings in proteins

    NASA Astrophysics Data System (ADS)

    Ding, Keyang; Gronenborn, Angela M.

    2004-04-01

    Sensitivity-enhanced 2D IPAP experiments using the accordion principle for measuring one-bond 13C '- 13C α and 1H α- 13C α dipolar couplings in proteins are presented. The resolution of the resulting spectra is identical to that of the decoupled HSQC spectra and the sensitivity of the corresponding 1D acquisitions are only slightly lower than those obtained with 3D HNCO and 3D HN(COCA)HA pulse sequences due to an additional delay 2 Δ. For cases of limited resolution in the 2D 15N- 1H N HSQC spectrum the current pulse sequences can easily be modified into 3D versions by introducing a poorly digitized third dimension, if so desired. The experiments described here are a valuable addition to the suites available for determination of residual dipolar couplings in biological systems.

  1. Quality assurance of PASADENA hyperpolarization for 13C biomolecules

    PubMed Central

    Hövener, Jan-Bernd; Chekmenev, Eduard Y.; Harris, Kent C.; Perman, William H.; Tran, Thao T.; Bhattacharya, Pratip

    2009-01-01

    Object Define MR quality assurance procedures for maximal PASADENA hyperpolarization of a biological 13C molecular imaging reagent. Materials and methods An automated PASADENA polarizer and a parahydrogen generator were installed. 13C enriched hydroxyethyl acrylate, 1-13C, 2,3,3-d3 (HEA), was converted to hyperpolarized hydroxyethyl propionate, 1-13C, 2,3,3-d3 (HEP) and fumaric acid, 1-13C, 2,3-d2 (FUM) to hyperpolarized succinic acid, 1-13C, 2,3-d2 (SUC), by reaction with parahydrogen and norbornadiene rhodium catalyst. Incremental optimization of successive steps in PASADENA was implemented. MR spectra and in vivo images of hyperpolarized 13C imaging agents were acquired at 1.5 and 4.7 T. Results Application of quality assurance (QA) criteria resulted in incremental optimization of the individual steps in PASADENA implementation. Optimal hyperpolarization of HEP of P = 20% was achieved by calibration of the NMR unit of the polarizer (B0 field strength ± 0.002 mT). Mean hyperpolarization of SUC, P = [15.3 ± 1.9]% (N = 16) in D2O, and P = [12.8 ± 3.1]% (N = 12) in H2O, was achieved every 5–8 min (range 13–20%). An in vivo 13C succinate image of a rat was produced. Conclusion PASADENA spin hyperpolarization of SUC to 15.3% in average was demonstrated (37,400 fold signal enhancement at 4.7 T). The biological fate of 13C succinate, a normally occurring cellular intermediate, might be monitored with enhanced sensitivity. PMID:19067009

  2. 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.

  3. IRMS detection of testosterone manipulated with 13C labeled standards in human urine by removing the labeled 13C.

    PubMed

    Wang, Jingzhu; Yang, Rui; Yang, Wenning; Liu, Xin; Xing, Yanyi; Xu, Youxuan

    2014-12-10

    Isotope ratio mass spectrometry (IRMS) is applied to confirm testosterone (T) abuse by determining the carbon isotope ratios (δ(13)C value). However, (13)C labeled standards can be used to control the δ(13)C value and produce manipulated T which cannot be detected by the current method. A method was explored to remove the (13)C labeled atom at C-3 from the molecule of androsterone (Andro), the metabolite of T in urine, to produce the resultant (A-nor-5α-androstane-2,17-dione, ANAD). The difference in δ(13)C values between Andro and ANAD (Δδ(13)CAndro-ANAD, ‰) would change significantly in case manipulated T is abused. Twenty-one volunteers administered T manipulated with different (13)C labeled standards. The collected urine samples were analyzed with the established method, and the maximum value of Δδ(13)CAndro-ANAD post ingestion ranged from 3.0‰ to 8.8‰. Based on the population reference, the cut-off value of Δδ(13)CAndro-ANAD for positive result was suggested as 1.2‰. The developed method could be used to detect T manipulated with 3-(13)C labeled standards. PMID:25441891

  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. 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

  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. Field measurements of del13C in ecosystem respiration

    NASA Astrophysics Data System (ADS)

    van Asperen, Hella; Sabbatini, Simone; Nicolini, Giacomo; Warneke, Thorsten; Papale, Dario; Notholt, Justus

    2014-05-01

    Stable carbon isotope del13C-measurements are extensively used to study ecological and biogeochemical processes in ecosystems. Above terrestrial ecosystems, atmospheric del13C can vary largely due to photosynthetic fractionation. Photosynthetic processes prefer the uptake of the lighter isotope 12C (in CO2), thereby enriching the atmosphere in 13C and depleting the ecosystem carbon. At night, when ecosystem respiratory fluxes are dominant, 13C-depleted CO2 is respired and thereby depletes the atmospheric del13C-content. Different ecosystems and different parts of one ecosystem (type of plant, leaves, and roots) fractionate and respire with a different del13C-ratio signature. By determining the del13C-signature of ecosystem respiration in temporal and spatial scale, an analysis can be made of the composition of respiratory sources of the ecosystem. A field study at a dry cropland after harvest (province of Viterbo, Lazio, Italy) was performed in the summer of 2013. A FTIR (Fourier Transform Infrared Spectrometer) was set up to continuously measure CO2-, CH4-, N2O-, CO- and del13C-concentrations. The FTIR was connected to 2 different flux measurements systems: a Flux Gradient system (sampling every half hour at 1.3m and 4.2m) and 2 flux chambers (measured every hour), providing a continuous data set of the biosphere-atmosphere gas fluxes and of the gas concentrations at different heights. Keeling plot intercept values of respiratory CO2, measured by the Flux Gradient system at night, were determined to be between -25‰ and -20‰. Keeling plot intercept values of respiratory CO2, measured by the flux chamber system, varied between -24‰ and -29‰, and showed a clear diurnal pattern, suggesting different (dominant) respiratory processes between day and night.

  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. 13C-phenylalanine breath test detects altered phenylalanine kinetics in schizophrenia patients.

    PubMed

    Teraishi, T; Ozeki, Y; Hori, H; Sasayama, D; Chiba, S; Yamamoto, N; Tanaka, H; Iijima, Y; Matsuo, J; Kawamoto, Y; Kinoshita, Y; Hattori, K; Ota, M; Kajiwara, M; Terada, S; Higuchi, T; Kunugi, H

    2012-01-01

    Phenylalanine is an essential amino acid required for the synthesis of catecholamines including dopamine. Altered levels of phenylalanine and its metabolites in blood and cerebrospinal fluid have been reported in schizophrenia patients. This study attempted to examine for the first time whether phenylalanine kinetics is altered in schizophrenia using L-[1-(13)C]phenylalanine breath test ((13)C-PBT). The subjects were 20 chronically medicated schizophrenia patients (DSM-IV) and the same number of age- and sex-matched controls. (13)C-phenylalanine (99 atom% (13)C; 100 mg) was administered orally and the breath (13)CO(2) /(12)CO(2) ratio was monitored for 120 min. The possible effect of antipsychotic medication (risperidone (RPD) or haloperidol (HPD) treatment for 21 days) on (13)C-PBT was examined in rats. Body weight (BW), age and diagnostic status were significant predictors of the area under the curve of the time course of Δ(13)CO(2) (‰) and the cumulative recovery rate (CRR) at 120 min. A repeated measures analysis of covariance controlled for age and BW revealed that the patterns of CRR change over time differed between the patients and controls and that Δ(13)CO(2) was lower in the patients than in the controls at all sampling time points during the 120 min test, with an overall significant difference between the two groups. Chronic administration of RPD or HPD had no significant effect on (13)C-PBT indices in rats. Our results suggest that (13)C-PBT is a novel laboratory test that can detect altered phenylalanine kinetics in chronic schizophrenia patients. Animal experiments suggest that the observed changes are unlikely to be attributable to antipsychotic medication. PMID:22832963

  10. Factors determining δ13C and δ18O fractionation in aragonitic otoliths of marine fish

    NASA Astrophysics Data System (ADS)

    Thorrold, Simon R.; Campana, Steven E.; Jones, Cynthia M.; Swart, Peter K.

    1997-07-01

    Fish otoliths are aragonitic accretions located within the inner ear of teleost fish. The acellular nature of otoliths, along with taxon-specific shapes, chronological growth increments, and abundance in the fossil record suggest that the stable isotope chemistry of these structures may be unique recorders of environmental conditions experienced by fish in both modern and ancient water masses. To assess the factors determining δ 13C and δ 18O fractionation in fish otoliths, we reared Atlantic croaker ( Micropogonias undulatus) larvae under controlled environmental conditions. Metabolic effects apparently generated large isotopic disequilibria in the δ 13C values of M. undulatus otoliths. We found evidence of a negative regression between δ 13C- carbonate-δ 13C water (δ 13C) and temperature: δ 13C = -1.78 - 0.18 T °C However, this relationship was aliased to a degree by a positive correlation between δ 13C and somatic growth and otolith precipitation rates. Oxygen isotopes were deposited close to equilibrium with the ambient water. The relationship between temperature and the 18O/ 16O fractionation factor (α) was determined empirically to be: 1000 ln α = 18.56(10 3T K -1) - 32.54 The fractionation factor was not affected by either otolith precipitation or fish growth rates. Reconstruction of water temperature histories should, therefore, be possible from the δ 18O values of M. undulatus otoliths with a precision of 1°C, providing the δ 18O of the ambient water can be estimated.

  11. Directly detected (55)Mn MRI: application to phantoms for human hyperpolarized (13)C MRI development.

    PubMed

    von Morze, Cornelius; Carvajal, Lucas; Reed, Galen D; Swisher, Christine Leon; Tropp, James; Vigneron, Daniel B

    2014-12-01

    In this work we demonstrate for the first time directly detected manganese-55 ((55)Mn) magnetic resonance imaging (MRI) using a clinical 3T MRI scanner designed for human hyperpolarized (13)C clinical studies with no additional hardware modifications. Due to the similar frequency of the (55)Mn and (13)C resonances, the use of aqueous permanganate for large, signal-dense, and cost-effective "(13)C" MRI phantoms was investigated, addressing the clear need for new phantoms for these studies. Due to 100% natural abundance, higher intrinsic sensitivity, and favorable relaxation properties, (55)Mn MRI of aqueous permanganate demonstrates dramatically increased sensitivity over typical (13)C phantom MRI, at greatly reduced cost as compared with large (13)C-enriched phantoms. A large sensitivity advantage (22-fold) was demonstrated. A cylindrical phantom (d=8 cm) containing concentrated aqueous sodium permanganate (2.7 M) was scanned rapidly by (55)Mn MRI in a human head coil tuned for (13)C, using a balanced steady state free precession acquisition. The requisite penetration of radiofrequency magnetic fields into concentrated permanganate was investigated by experiments and high frequency electromagnetic simulations, and found to be sufficient for (55)Mn MRI with reasonably sized phantoms. A sub-second slice-selective acquisition yielded mean image signal-to-noise ratio of ~60 at 0.5 cm(3) spatial resolution, distributed with minimum central signal ~40% of the maximum edge signal. We anticipate that permanganate phantoms will be very useful for testing HP (13)C coils and methods designed for human studies. PMID:25179135

  12. The Fate of Oral Glucosamine Traced by 13C Labeling in the Dog

    PubMed Central

    Dodge, George R.; Regatte, Ravinder R.; Noyszewski, Elizabeth A.; Hall, Jeffery O.; Sharma, Akella V.; Callaway, D. Allen; Reddy, Ravinder

    2011-01-01

    Objective: It has remained ambiguous as to whether oral dosing of glucosamine (GlcN) would make its way to the joint and affect changes in the cartilage, particularly the integrity of cartilage and chondrocyte function. The objective of this study was to trace the fate of orally dosed GlcN and determine definitively if GlcN was incorporated into cartilage proteoglycans. Design: Two dogs were treated with 13C-GlcN-HCl by oral dosing (500 mg/dog/d for 2 weeks and 250 mg/dog/d for 3 weeks). Cartilage was harvested from the tibial plateau and femoral condyles along with tissue specimens from the liver, spleen, heart, kidney, skin, skeletal muscle, lung, and costal cartilage. Percentages of 13C and 13C-GlcN present in each tissue sample were determined by inductively coupled plasma mass spectroscopy (ICP-MS) and nuclear magnetic resonance spectroscopy, respectively. Results: In the case of dog 1 (2-week treatment), there was an increase of 2.3% of 13C present in the articular cartilage compared to the control and an increase of 1.6% of 13C in dog 2 compared to control. As to be expected, the highest percentage of 13C in the other tissues tested was found in the liver, and the remaining tissues had percentages of 13C less than that of articular cartilage. Conclusion: The results are definitive and for the first time provide conclusive evidence that orally given GlcN can make its way through the digestive tract and be used by chondrocytes in joint cartilage, thereby potentially having an effect on the available GlcN for proteoglycan biosynthesis. PMID:26069586

  13. On the use of phloem sap δ13C to estimate canopy carbon discrimination

    NASA Astrophysics Data System (ADS)

    Rascher, Katherine; Máguas, Cristina; Werner, Christiane

    2010-05-01

    along the canopy to trunk continuum. We further hypothesize that pronounced depletion along the basipetal transport pathway in A. longifolia (more than 6 per mil from leaf water soluble organic matter to trunk phloem sap) may be due to high stem photosynthesis rates in this green-barked legume. Regardless of these fractionation effects, phloem sap d13C correlated well with environmental parameters driving photosynthesis (photosynthetic photon flux density, soil moisture, vapor pressure deficit) for both species indicating that phloem sap d13C is a good integrative tracer of changes in canopy-level carbon discrimination once species-specific differences in post-photosynthetic fractionation are accounted for. Furthermore, we illustrate that combining sap flow estimated canopy stomatal conductance (gs) with measurements of phloem sap d13C (adjusted for post-photosynthetic fractionation) has significant potential as a relatively non-intensive method for estimating canopy-level carbon assimilation rates in field studies.

  14. 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.

  15. 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

  16. 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

  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. 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.

  19. 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

  20. 13C NMR spectroscopy applications to brain energy metabolism

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    1999-01-01

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

  2. A Method to Constrain Genome-Scale Models with 13C Labeling Data

    PubMed Central

    García Martín, Héctor; Kumar, Vinay Satish; Weaver, Daniel; Ghosh, Amit; Chubukov, Victor; Mukhopadhyay, Aindrila; Arkin, Adam; Keasling, Jay D.

    2015-01-01

    Current limitations in quantitatively predicting biological behavior hinder our efforts to engineer biological systems to produce biofuels and other desired chemicals. Here, we present a new method for calculating metabolic fluxes, key targets in metabolic engineering, that incorporates data from 13C labeling experiments and genome-scale models. The data from 13C labeling experiments provide strong flux constraints that eliminate the need to assume an evolutionary optimization principle such as the growth rate optimization assumption used in Flux Balance Analysis (FBA). This effective constraining is achieved by making the simple but biologically relevant assumption that flux flows from core to peripheral metabolism and does not flow back. The new method is significantly more robust than FBA with respect to errors in genome-scale model reconstruction. Furthermore, it can provide a comprehensive picture of metabolite balancing and predictions for unmeasured extracellular fluxes as constrained by 13C labeling data. A comparison shows that the results of this new method are similar to those found through 13C Metabolic Flux Analysis (13C MFA) for central carbon metabolism but, additionally, it provides flux estimates for peripheral metabolism. The extra validation gained by matching 48 relative labeling measurements is used to identify where and why several existing COnstraint Based Reconstruction and Analysis (COBRA) flux prediction algorithms fail. We demonstrate how to use this knowledge to refine these methods and improve their predictive capabilities. This method provides a reliable base upon which to improve the design of biological systems. PMID:26379153

  3. Multi-objective experimental design for (13)C-based metabolic flux analysis.

    PubMed

    Bouvin, Jeroen; Cajot, Simon; D'Huys, Pieter-Jan; Ampofo-Asiama, Jerry; Anné, Jozef; Van Impe, Jan; Geeraerd, Annemie; Bernaerts, Kristel

    2015-10-01

    (13)C-based metabolic flux analysis is an excellent technique to resolve fluxes in the central carbon metabolism but costs can be significant when using specialized tracers. This work presents a framework for cost-effective design of (13)C-tracer experiments, illustrated on two different networks. Linear and non-linear optimal input mixtures are computed for networks for Streptomyces lividans and a carcinoma cell line. If only glucose tracers are considered as labeled substrate for a carcinoma cell line or S. lividans, the best parameter estimation accuracy is obtained by mixtures containing high amounts of 1,2-(13)C2 glucose combined with uniformly labeled glucose. Experimental designs are evaluated based on a linear (D-criterion) and non-linear approach (S-criterion). Both approaches generate almost the same input mixture, however, the linear approach is favored due to its low computational effort. The high amount of 1,2-(13)C2 glucose in the optimal designs coincides with a high experimental cost, which is further enhanced when labeling is introduced in glutamine and aspartate tracers. Multi-objective optimization gives the possibility to assess experimental quality and cost at the same time and can reveal excellent compromise experiments. For example, the combination of 100% 1,2-(13)C2 glucose with 100% position one labeled glutamine and the combination of 100% 1,2-(13)C2 glucose with 100% uniformly labeled glutamine perform equally well for the carcinoma cell line, but the first mixture offers a decrease in cost of $ 120 per ml-scale cell culture experiment. We demonstrated the validity of a multi-objective linear approach to perform optimal experimental designs for the non-linear problem of (13)C-metabolic flux analysis. Tools and a workflow are provided to perform multi-objective design. The effortless calculation of the D-criterion can be exploited to perform high-throughput screening of possible (13)C-tracers, while the illustrated benefit of multi

  4. Impact of Ho(3+)-doping on (13)C dynamic nuclear polarization using trityl OX063 free radical.

    PubMed

    Kiswandhi, Andhika; Niedbalski, Peter; Parish, Christopher; Kaur, Pavanjeet; Martins, André; Fidelino, Leila; Khemtong, Chalermchai; Song, Likai; Sherry, A Dean; Lumata, Lloyd

    2016-08-21

    We have investigated the effects of Ho-DOTA doping on the dynamic nuclear polarization (DNP) of [1-(13)C] sodium acetate using trityl OX063 free radical at 3.35 T and 1.2 K. Our results indicate that addition of 2 mM Ho-DOTA on 3 M [1-(13)C] sodium acetate sample in 1 : 1 v/v glycerol : water with 15 mM trityl OX063 improves the DNP-enhanced (13)C solid-state nuclear polarization by a factor of around 2.7-fold. Similar to the Gd(3+) doping effect on (13)C DNP, the locations of the positive and negative (13)C maximum polarization peaks in the (13)C microwave DNP sweep are shifted towards each other with the addition of Ho-DOTA on the DNP sample. W-band electron spin resonance (ESR) studies have revealed that while the shape and linewidth of the trityl OX063 ESR spectrum was not affected by Ho(3+)-doping, the electron spin-lattice relaxation time T1 of trityl OX063 was prominently reduced at cryogenic temperatures. The reduction of trityl OX063 electron T1 by Ho-doping is linked to the (13)C DNP improvement in light of the thermodynamic picture of DNP. Moreover, the presence of Ho-DOTA in the dissolution liquid at room temperature has negligible reduction effect on liquid-state (13)C T1, in contrast to Gd(3+)-doping which drastically reduces the (13)C T1. The results here suggest that Ho(3+)-doping is advantageous over Gd(3+) in terms of preservation of hyperpolarized state-an important aspect to consider for in vitro and in vivo NMR or imaging (MRI) experiments where a considerable preparation time is needed to administer the hyperpolarized (13)C liquid. PMID:27424954

  5. Specific 13C functional pathways as diagnostic targets in gastroenterology breath-tests: tricks for a correct interpretation.

    PubMed

    Pizzoferrato, M; Del Zompo, F; Mangiola, F; Lopetuso, L R; Petito, V; Cammarota, G; Gasbarrini, A; Scaldaferri, F

    2013-01-01

    Breath tests are non-invasive, non-radioactive, safe, simple and effective tests able to determine significant metabolic alterations due to specific diseases or lack of specific enzymes. Carbon isotope (13)C, the stable-non radioactive isotope of carbon, is the most used substrate in breath testing, in which (13)C/(12)C ratio is measured and expressed as a delta value, a differences between readings and a fixed standard. (13)C/(12)C ratio is measured with isotope ratio mass spectrometry or non-dispersive isotope-selective infrared spectrometer and generally there is a good agreement between these techniques in the isotope ratio estimation. (13)C/(12)C ratio can be expressed as static measurement (like delta over baseline in urea breath test) or as dynamic measurement as percent dose recovery, but more dosages are necessary. (13)C Breath-tests are involved in many fields of interest within gastroenterology, such as detection of Helicobacter pylori infection, study of gastric emptying, assessment of liver and exocrine pancreatic functions, determination of oro-caecal transit time, evaluation of absorption and to a lesser extend detection of bacterial overgrowth. The use of every single test in a clinical setting is vary depending on accuracy and substrate costs. This review is meant to present (13)C the meaning of (13)C/(12)C ratio and static and dynamic measure and, finally, the instruments dedicated to its use in gastroenterology. A brief presentation of (13)C breath tests in gastroenterology is also provided. PMID:24443068

  6. Inclusion of 13C and D in protonated acetylene

    NASA Astrophysics Data System (ADS)

    Fortenberry, Ryan C.; Roueff, Evelyne; Lee, Timothy J.

    2016-04-01

    The rovibrational spectrum of cyclic, protonated acetylene has been established. The improvement in modern telescopes coupled with the different branching ratios in reaction models welcomes study of 13C-substitution for C2H3+. Quartic force fields (QFFs) have been previously utilized to predict the antisymmetric HCCH stretch in standard c-C2H3+ to within 0.1 cm-1 of experiment and are employed here to generate rovibrational insights for the 13C isotopologues. The zero-point energies are also given for the cyclic and 'Y'-shaped isomers for both 13C and D substitutions. Vibrational intensities and the dipole moments are provided in order to characterize more fully this simple cation.

  7. {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.

  8. Magnetic Resonance Imaging with Hyperpolarized 13C Contrast Agents

    NASA Astrophysics Data System (ADS)

    Gordon, Jeremy W.

    Hyperpolarized 13C substrates offer the potential to non-invasively image metabolism and enzymatic activity. However, hyperpolarization introduces a number of difficulties, and imaging is hampered by non-equilibrium magnetization and the need for spectral encoding. There is therefore a need for fast and RF efficient spectral imaging techniques. This work presents a number of new methods that can be used to improve polarization, increase RF efficiency and improve modeling accuracy in hyperpolarized 13C experiments. In particular, a novel encoding and reconstruction algorithm is presented that can generate spatially and spectrally resolved images with a single RF excitation and echo time. This reconstruction framework increases data acquisition efficiency, enabling accelerated acquisition speed, preserved polarization, and/or improved temporal or spatial resolution. Overall, the methods enumerated in this dissertation have the potential to improve modeling accuracy and to mitigate the conventional tradeoffs between SNR, spatial resolution, and temporal resolution that govern image quality in hyperpolarized 13C experiments.

  9. Study of molecular interactions with 13C DNP-NMR

    NASA Astrophysics Data System (ADS)

    Lerche, Mathilde H.; Meier, Sebastian; Jensen, Pernille R.; Baumann, Herbert; Petersen, Bent O.; Karlsson, Magnus; Duus, Jens Ø.; Ardenkjær-Larsen, Jan H.

    2010-03-01

    NMR spectroscopy is an established, versatile technique for the detection of molecular interactions, even when these interactions are weak. Signal enhancement by several orders of magnitude through dynamic nuclear polarization alleviates several practical limitations of NMR-based interaction studies. This enhanced non-equilibrium polarization contributes sensitivity for the detection of molecular interactions in a single NMR transient. We show that direct 13C NMR ligand binding studies at natural isotopic abundance of 13C gets feasible in this way. Resultant screens are easy to interpret and can be performed at 13C concentrations below μM. In addition to such ligand-detected studies of molecular interaction, ligand binding can be assessed and quantified with enzymatic assays that employ hyperpolarized substrates at varying enzyme inhibitor concentrations. The physical labeling of nuclear spins by hyperpolarization thus provides the opportunity to devise fast novel in vitro experiments with low material requirement and without the need for synthetic modifications of target or ligands.

  10. Measurements of 13C multiple-quantum coherences in amyloid fibrils under magic-angle spinning.

    PubMed

    Chou, Fang-Chieh; Tsai, Tim W T; Cheng, Hsin-Mei; Chan, Jerry C C

    2012-06-21

    The excitation and detection of high-order multiple quantum coherences among (13)C nuclear spins are demonstrated in the samples of [1-(13)C]-L-alanine and (13)C labeled amyloid fibrils at a spinning frequency of 20 kHz. The technique is based on the double-quantum average Hamiltonian prepared by the DRAMA-XY4 pulse sequence. Empirically, we find that multiple supercycles are required to suppress the higher-order effects for real applications. Measurements for the fibril samples formed by the polypeptides of PrP(113-127) provide the first solid-state NMR evidence for the stacking of multiple β-sheet layers at the structural core of amyloid fibrils. PMID:22632418

  11. Measuring (13)C/(15)N chemical shift anisotropy in [(13)C,(15)N] uniformly enriched proteins using CSA amplification.

    PubMed

    Hung, Ivan; Ge, Yuwei; Liu, Xiaoli; Liu, Mali; Li, Conggang; Gan, Zhehong

    2015-11-01

    Extended chemical shift anisotropy amplification (xCSA) is applied for measuring (13)C/(15)N chemical shift anisotropy (CSA) of uniformly labeled proteins under magic-angle spinning (MAS). The amplification sequence consists of a sequence of π-pulses that repetitively interrupt MAS averaging of the CSA interaction. The timing of the pulses is designed to generate amplified spinning sideband manifolds which can be fitted to extract CSA parameters. The (13)C/(13)C homonuclear dipolar interactions are not affected by the π-pulses due to the bilinear nature of the spin operators and are averaged by MAS in the xCSA experiment. These features make the constant evolution-time experiment suitable for measuring CSA of uniformly labeled samples. The incorporation of xCSA with multi-dimensional (13)C/(15)N correlation is demonstrated with a GB1 protein sample as a model system for measuring (13)C/(15)N CSA of all backbone (15)NH, (13)CA and (13)CO sites. PMID:26404770

  12. Influence of 13C isotopic labeling location of 13C DNP of acetate using TEMPO free radical

    NASA Astrophysics Data System (ADS)

    Parish, Christopher; Niedbalski, Peter; Lumata, Lloyd

    2015-03-01

    Dynamic nuclear polarization (DNP) via the dissolution method enhances the liquid-state magnetic resonance (NMR or MRI) signals of insensitive nuclear spins by at least 10,000-fold. The basis for all these signal enhancements at room temperature is the polarization transfer from the electrons to nuclear spins at cryogenic temperature and high magnetic field. In this work, we have studied the influence of the location of 13C isotopic labeling on the DNP of sodium acetate at 3.35 T and 1.4 K using a wide ESR linewidth free radical 4-oxo-TEMPO. The carbonyl [1-13C]acetate spins produced a polarization level that is almost twice that of the methyl [2-13C]acetate spins. On the other hand, the polarization of the methyl 13C spins doubled to reach the level of [1-13C]acetate when the methyl group was deuterated. Meanwhile, the solid-state nuclear relaxation of these samples are the same and do not correlate with the polarization levels. These behavior implies that the nuclear relaxation for these samples is dominated by the contribution from the free radicals and the polarization levels can be explained by a thermodynamic picture of DNP.

  13. 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

  14. Rotary resonance recoupling of 13C- 1H dipolar interactions in magic angle spinning 13C NMR of dynamic solids

    NASA Astrophysics Data System (ADS)

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

    2000-06-01

    Rotary resonance recoupling of heteronuclear 13C- 1H dipolar interactions in magic angle spinning solid state 13C NMR spectra (recorded under conditions of 1H decoupling at frequency ν1 and magic angle spinning at frequency νr) has been studied for three examples of molecular solids (adamantane, ferrocene and hexamethylbenzene) in which substantial molecular motion is known to occur. It is shown that when rotary resonance conditions are satisfied (i.e. ν1/νr= n, for n=1 or 2), the recoupling can lead to motionally averaged Pake-like powder patterns from which information on 13C- 1H internuclear distances and/or molecular motion can be derived.

  15. Two-dimensional (13)C-(13)C correlation spectroscopy with magic angle spinning and dynamic nuclear polarization.

    PubMed

    Rosay, Melanie; Weis, Volker; Kreischer, Kenneth E; Temkin, Richard J; Griffin, Robert G

    2002-04-01

    The sensitivity of solid-state NMR experiments can be enhanced with dynamic nuclear polarization (DNP), a technique that transfers the high Boltzmann polarization of unpaired electrons to nuclei. Signal enhancements of up to 23 have been obtained for magic angle spinning (MAS) experiments at 5 T and 85-90 K using a custom-designed high-power gyrotron. The extended stability of MAS/DNP experiments at low temperature is demonstrated with (1)H-driven (13)C spin-diffusion experiments on the amino acid proline. These (13)C-(13)C chemical shift correlation spectra are the first two-dimensional MAS/DNP experiments performed at high field (>1.4 T). PMID:11916398

  16. 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.

  17. Synthesis of 2-deoxy-(6-/sup 13/C)glucose

    SciTech Connect

    Walker, T.E.; Unkefer, C.J.; Ehler, D.S.

    1987-05-01

    The authors have prepared 2-deoxy-D-(6-/sup 13/C)glucose which will be used to test the stability of 2-deoxy-D-glucose-6-phosphate in brain tissue. They chose to label 2-deoxy-D-glucose at C-6 because of the large chemical shift difference between C-6 in the free sugar and C-6 in the 6-phosphate analog. Their synthetic scheme is similar to that used for the synthesis of D-(6-/sup 13/C)glucose which involves the removal of C-6 from D-glucose followed by its replacement with /sup 13/C. They first prepare the methyl ..cap alpha..-furanoside using trifluoroacetic acid in methanol. This product is then treated with periodate which cleaves only between C-5 and C-6 to form a hydrated aldehyde which is reacted directly with K/sup 13/CN to form a mixture of nitriles. The enriched nitriles are reduced with hydrogen to a mixture of 6-aldehydo sugars using a 5% Pd on carbon catalyst. These sugars are reduced with NaBH/sub 4/ to a mixture of labeled methyl furanosides. Acid hydrolysis followed by chromatography yields 2-deoxy-D-(6-/sup 13/C)glucose in an overall yield of 10% from K/sup 13/CN.

  18. 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

  19. 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

  20. Using Headspace Equilibration to Measure the d13C of Soil-Respired CO2

    NASA Astrophysics Data System (ADS)

    Robertson, M. A.; Powers, E.; Marshall, J.

    2007-12-01

    Soil respiration is an important component of the global carbon cycle and can account for as much as 70% of ecosystem respiration. Soil gas flux measurements have been combined with stable isotope analysis to examine ecosystem properties and processes such as water-use efficiency and the role of above ground weather in controlling soil respiration. However, current methods of measuring the δ13C of soil-respired CO2 are either inherently inaccurate or time-consuming and tedious. An alternative method of obtaining this value offers a potential solution to these problems. In this method, plastic chambers are fitted with rubber septa to allow for sample collection, then inverted and partially buried in soil. The chamber headspace is allowed to come to equilibrium with soil air. In this study we tested the viability of this method by examining whether frequent resampling of respiration chambers affected δ13C measurements, whether headspace CO2 concentration and δ13C values approached equilibrium asymptotically, and whether simulated and actual diel temperature cycles affected estimates of δ13C. All experiments were conducted on respiration chambers inverted in potting soil and placed in a Conviron growth chamber, with the exception of one field test that was conducted on respiration chambers installed in a Northern Idaho experimental forest. Samples were collected with a syringe and stored in glass vials for analysis by a ratioing mass spectrometer. We found that resampling respiration chambers as frequently as every 10 minutes had no significant effect on final δ13C values, that both chamber CO2 concentrations and δ13C values exhibited an asymptotic approach to equilibrium, and that the equilibrium value was offset from the initial flux by the amount we expected, approximately 4 ‰. However, we also found that diel temperature variation affected both headspace CO2 concentration and δ13C in the lab and in the field. We concluded that if this method is used in

  1. 13C-NMR spectra and contact time experiment for Skjervatjern fulvic and humic acids

    USGS Publications Warehouse

    Malcolm, R.L.

    1992-01-01

    The T(CP) and T(1p) time constants for Skjervatjern fulvic and humic acids were determined to be short with T(CP) values ranging from 0.14 ms to 0.53 ms and T(1p) values ranging from 3.3 ms to 5.9 ms. T(CP) or T(1p) time constants at a contact time of 1 ms are favorable for quantification of 13C-NMR spectra. Because of the short T(CP) values, correction factors for signal intensity for various regions of the 13C-NMR spectra would be necessary at contact times greater than 1.1 ms or less than 0.9 ms. T(CP) and T(1p) values have a limited non-homogeneity within Skjervatjern fulvic and humic acids. A pulse delay or repeat time of 700 ms is more than adequate for quantification of these 13C-NMR spectra. Paramagnetic effects in these humic substances are precluded due to low inorganic ash contents, low contents of Fe, Mn, and Co, and low organic free-radical contents. The observed T(CP) values suggest that all the carbon types in Skjervatjern fulvic and humic acids are fully cross-polarized before significant proton relaxation occurs. The 13C-NMR spectra for Skjervatjern fulvic acid is similar to most aquatic fulvic acids as it is predominantly aliphatic, low in aromaticity (fa1 = 24), low in phenolic content, high in carboxyl content, and has no resolution of a methoxyl peak. The 13C-NMR spectra for Skjervatjern humic acid is also similar to most other aquatic humic acids in that it is also predominantly aliphatic, high in aromaticity (fa1 = 38), moderate in phenolic content, moderate in carboxyl content, and has a clear resolution of a methoxyl carbon region. After the consideration of the necessary 13C-NMR experimental conditions, these spectra are considered to be quantitative. With careful consideration of the previously determined 13C-NMR experimental conditions, quantitative spectra can be obtained for humic substances in the future from the HUMEX site. Possible changes in humic substances due to acidification should be determined from 13C-NMR data.

  2. 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

  3. Strong coupling of centennial-scale changes of Asian monsoon and soil processes derived from stalagmite δ18O and δ13C records, southern China

    NASA Astrophysics Data System (ADS)

    Liu, Dianbing; Wang, Yongjin; Cheng, Hai; Edwards, R. Lawrence; Kong, Xinggong; Li, Ting-Yong

    2016-05-01

    The paleoclimate application of speleothem δ13C is influenced by site-specific processes. Here we present four stalagmite δ13C records from two caves in southern China, covering early and late Marine Isotope Stage (MIS) 3 and the Holocene, to investigate the spatio-temporal pattern of calcite δ13C changes and the relationship with Asian monsoon (AM) variability. In each growth period, precessional- to millennial-scale changes are clear in the δ18O record. In contrast, millennial variability is absent in the δ13C record, which characterizes persistent centennial oscillations. However, centennial-scale δ18O variations agree well with those of δ13C, with a larger amplitude in δ13C changes (about twice that of δ18O). This suggests that soil humidity balance associated with regional hydrological circulations is important for these centennial δ13C changes, although evaporation-related kinetic fractionation can induce concurrent enrichments in δ18O and δ13C. In frequency, the detrended δ18O and δ13C records are coupled at a periodicity of about 300 yr during the last glacial period and 150 yr during the Holocene. Those centennial-scale δ13C variations are generally consistent with Greenland temperature variability, indicating a climate response over broad regions. Thus, strong co-variation of δ18O and δ13C records should have a climatic origin, even if it is amplified by kinetic effects.

  4. Strong coupling of centennial-scale changes of Asian monsoon and soil processes derived from stalagmite δ18O and δ13C records, southern China

    NASA Astrophysics Data System (ADS)

    Liu, Dianbing; Wang, Yongjin; Cheng, Hai; Edwards, R. Lawrence; Kong, Xinggong; Li, Ting-Yong

    2016-05-01

    The paleoclimate application of speleothem δ13C is influenced by site-specific processes. Here we present four stalagmite δ13C records from two caves in southern China, covering early and late Marine Isotope Stage (MIS) 3 and the Holocene, to investigate the spatio-temporal pattern of calcite δ13C changes and the relationship with Asian monsoon (AM) variability. In each growth period, precessional- to millennial-scale changes are clear in the δ18O record. In contrast, millennial variability is absent in the δ13C record, which characterizes persistent centennial oscillations. However, centennial-scale δ18O variations agree well with those of δ13C, with a larger amplitude in δ13C changes (about twice that of δ18O). This suggests that soil humidity balance associated with regional hydrological circulations is important for these centennial δ13C changes, although evaporation-related kinetic fractionation can induce concurrent enrichments in δ18O and δ13C. In frequency, the detrended δ18O and δ13C records are coupled at a periodicity of about 300 yr during the last glacial period and 150 yr during the Holocene. Those centennial-scale δ13C variations are generally consistent with Greenland temperature variability, indicating a climate response over broad regions. Thus, strong co-variation of δ18O and δ13C records should have a climatic origin, even if it is amplified by kinetic effects.

  5. 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.

  6. 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##

  7. Distortion-free {sup 13}C NMR spectroscopy in coal: {sup 1}H rotating-frame dynamic nuclear polarization and {sup 1}H-{sup 13}C cross-polarization

    SciTech Connect

    Wind, R.A.

    1993-12-31

    A {sup 1}H-{sup 13}C cross-polarization (CP) experiment is described in which the {sup 1}H magnetization, used in CP, is obtained via dynamic nuclear polarization (DNP) in the proton rotating frame (RF DNP). This experiment can be carried out in coal and other solids containing unpaired electrons. In this so-called RF DNP-CP experiment, interplay effects between the {sup 1}H-{sup 13}C polarization-transfer times and the {sup 1}H rotating-frame relaxation time are avoided; thus {sup 13}C spectral distortions due to these effects are prevented. Moreover, multiple-contact RF DNP-CP experiments are possible, and these experiments reduce the measuring time of a {sup 13}C spectrum. An application of the RF DNP-CP technique in a low-volatile bituminous coal is given. 25 refs., 3 figs.

  8. Single voxel localization for dynamic hyperpolarized 13C MR spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Albert P.; Cunningham, Charles H.

    2015-09-01

    The PRESS technique has been widely used to achieve voxel localization for in vivo1H MRS acquisitions. However, for dynamic hyperpolarized 13C MRS experiments, the transition bands of the refocusing pulses may saturate the pre-polarized substrate spins flowing into the voxel. This limitation may be overcome by designing refocusing pulses that do not perturb the resonance of the hyperpolarized substrate, but selectively refocuses the spins of the metabolic products. In this study, a PRESS pulse sequence incorporating spectral-spatial refocusing pulses that have a stop band ('notch') at the substrate resonance is tested in vivo using hyperpolarized [1-13C]pyruvate. Higher metabolite SNR was observed in experiments using the spectral-spatial refocusing pulses as compared to conventional refocusing pulses.

  9. Single voxel localization for dynamic hyperpolarized (13)C MR spectroscopy.

    PubMed

    Chen, Albert P; Cunningham, Charles H

    2015-09-01

    The PRESS technique has been widely used to achieve voxel localization for in vivo(1)H MRS acquisitions. However, for dynamic hyperpolarized (13)C MRS experiments, the transition bands of the refocusing pulses may saturate the pre-polarized substrate spins flowing into the voxel. This limitation may be overcome by designing refocusing pulses that do not perturb the resonance of the hyperpolarized substrate, but selectively refocuses the spins of the metabolic products. In this study, a PRESS pulse sequence incorporating spectral-spatial refocusing pulses that have a stop band ('notch') at the substrate resonance is tested in vivo using hyperpolarized [1-(13)C]pyruvate. Higher metabolite SNR was observed in experiments using the spectral-spatial refocusing pulses as compared to conventional refocusing pulses. PMID:26232365

  10. Recent advances in mapping environmental microbial metabolisms through 13C isotopic fingerprints.

    PubMed

    Tang, Joseph Kuo-Hsiang; You, Le; Blankenship, Robert E; Tang, Yinjie J

    2012-11-01

    After feeding microbes with a defined (13)C substrate, unique isotopic patterns (isotopic fingerprints) can be formed in their metabolic products. Such labelling information not only can provide novel insights into functional pathways but also can determine absolute carbon fluxes through the metabolic network via metabolic modelling approaches. This technique has been used for finding pathways that may have been mis-annotated in the past, elucidating new enzyme functions, and investigating cell metabolisms in microbial communities. In this review paper, we summarize the applications of (13)C approaches to analyse novel cell metabolisms for the past 3 years. The isotopic fingerprints (defined as unique isotopomers useful for pathway identifications) have revealed the operations of the Entner-Doudoroff pathway, the reverse tricarboxylic acid cycle, new enzymes for biosynthesis of central metabolites, diverse respiration routes in phototrophic metabolism, co-metabolism of carbon nutrients and novel CO(2) fixation pathways. This review also discusses new isotopic methods to map carbon fluxes in global metabolisms, as well as potential factors influencing the metabolic flux quantification (e.g. metabolite channelling, the isotopic purity of (13)C substrates and the isotopic effect). Although (13)C labelling is not applicable to all biological systems (e.g. microbial communities), recent studies have shown that this method has a significant value in functional characterization of poorly understood micro-organisms, including species relevant for biotechnology and human health. PMID:22896564

  11. Recent advances in mapping environmental microbial metabolisms through 13C isotopic fingerprints

    PubMed Central

    Tang, Joseph Kuo-Hsiang; You, Le; Blankenship, Robert E.; Tang, Yinjie J.

    2012-01-01

    After feeding microbes with a defined 13C substrate, unique isotopic patterns (isotopic fingerprints) can be formed in their metabolic products. Such labelling information not only can provide novel insights into functional pathways but also can determine absolute carbon fluxes through the metabolic network via metabolic modelling approaches. This technique has been used for finding pathways that may have been mis-annotated in the past, elucidating new enzyme functions, and investigating cell metabolisms in microbial communities. In this review paper, we summarize the applications of 13C approaches to analyse novel cell metabolisms for the past 3 years. The isotopic fingerprints (defined as unique isotopomers useful for pathway identifications) have revealed the operations of the Entner–Doudoroff pathway, the reverse tricarboxylic acid cycle, new enzymes for biosynthesis of central metabolites, diverse respiration routes in phototrophic metabolism, co-metabolism of carbon nutrients and novel CO2 fixation pathways. This review also discusses new isotopic methods to map carbon fluxes in global metabolisms, as well as potential factors influencing the metabolic flux quantification (e.g. metabolite channelling, the isotopic purity of 13C substrates and the isotopic effect). Although 13C labelling is not applicable to all biological systems (e.g. microbial communities), recent studies have shown that this method has a significant value in functional characterization of poorly understood micro-organisms, including species relevant for biotechnology and human health. PMID:22896564

  12. Ethane's 12C/13C Ratio in Titan: Implications for Methane Replenishment

    NASA Technical Reports Server (NTRS)

    Jennings, Donald E.; Nixon, C. A.; Romani, P. N.; Bjoraker, G. L.; Sada, P. V.; Lunsford, A. W.; Boyle, R. J.; Hesman, B. E.; McCabe, G. H.

    2009-01-01

    As the .main destination of carbon in the destruction of methane in the atmosphere of Titan, ethane provides information about the carbon isotopic composition of the reservoir from which methane is replenished. If the amount of methane entering the atmosphere is presently equal to the amount converted to ethane, the 12C/13C ratio in ethane should be close to the ratio in the reservoir. We have measured the 12C/13C ratio in ethane both with Cassini CIRS(exp 1) and from the ground and find that it is very close to the telluric standard and outer planet values (89), consistent with a primordial origin for the methane reservoir. The lower 12C/13C ratio measured for methane by Huygens GCMS (82.3) can be explained if the conversion of CH4 to CH3 (and C2H6) favors 12C over 13C with a carbon kinetic isotope effect of 1.08. The time required for the atmospheric methane to reach equilibrium, i.e., for replenishment to equal destruction, is approximately 5 methane atmospheric lifetimes.

  13. Interlobe communication in 13C-methionine-labeled human transferrin.

    PubMed

    Beatty, E J; Cox, M C; Frenkiel, T A; Tam, B M; Mason, A B; MacGillivray, R T; Sadler, P J; Woodworth, R C

    1996-06-18

    [1H, 13C] NMR investigations of metal-induced conformational changes in the blood serum protein transferrin (80 kDa) are reported. These are thought to play an important role in the recognition of this protein by its cellular receptors. [1H, 13C] NMR resonance assignments are presented for all nine methionine 13CH3 groups of recombinant deglycosylated human transferrin on the basis of studies of recombinant N-lobe (40 kDa, five Met residues), NOESY-relayed [1H, 13C] HMQC spectra, and structural considerations. The first specific assignments for C-lobe resonances of transferrin are presented. Using methionine 13CH3 resonances as probes, it is shown that, with oxalate as the synergistic anion, Ga3+ binds preferentially to the C-lobe and subsequently to the N-lobe. The NMR shifts of Met464, which is in the Trp460-centered hydrophobic patch of helix 5 in the C-lobe in contact with the anion and metal binding site, show that Ga3+ binding causes movement of side chains within this helix, as is also the case in the N-lobe. The C-lobe residue Met382, which contacts the N-lobe hinge region, is perturbed when Ga3+ binds to the N-lobe, indicative of interlobe communication, a feature which may control the recognition of fully-metallated transferrin by its receptor. These results demonstrate that selective 13C labeling is a powerful method for probing the structure and dynamics of high-molecular-mass proteins. PMID:8672464

  14. 13c Measurements On Air of Small Ice Samples

    NASA Astrophysics Data System (ADS)

    Eyer, M.; Leuenberger, M.

    We have developed a new method for 13C analysis for very small air amounts of less than 0.5 cc STP, corresponding to less than 10 gram of ice. It is based on the needle-crasher technique, which we routinely use for CO2 concentration measurements by infrared laser absorption. The extracted air is slowly expanded into a large volume through a water trap held at ­100°C. This sampled air is then carried by a high helium flux through a modified Precon system of Thermo-Finnigan to separate CO2 from the air and to inject the pure CO2 gas in a low helium stream via an open split device to a Delta Plus XL mass spectrometer. The overall precision based on replicates of standard air is significantly better than 0.1 for a single analysis and is further improved by a triplicate measurement of the same sample through a specially designed gas splitter. We have used this new method for investigations on polar ice cores. The 13C measurements are important for climate reconstructions, e.g. to reconstruct the evolution and its variability in the terrestrial and oceanic carbon sinks and to identify natural variations in the marine carbon cycle. During the industrialization atmospheric 13C decreased by about -2, mainly due to the anthropogenic release of biogenic CO2 by fossil fuel burning. Reconstructions of carbon and oxygen cycles of Joos at al. [1999] using a double deconvolution method show that between 1930 and 1950 the net terrestrial release is changing to a net terrestrial uptake of CO2. A highly resolved 13C dataset of this time window would replenish the documentation of this behaviour. Further, it would be interesting to compare such data with O2/N2 measurements, known as an other partitioning tool for carbon sources and sinks. At the EGS 2002 we will present a highly resolved 13C record from Antarctic ice covering this time period.

  15. Millimeter and submillimeter wave spectra of 13C methylamine

    NASA Astrophysics Data System (ADS)

    Motiyenko, R. A.; Margulès, L.; Ilyushin, V. V.; Smirnov, I. A.; Alekseev, E. A.; Halfen, D. T.; Ziurys, L. M.

    2016-03-01

    Context. Methylamine (CH3NH2) is a light molecule of astrophysical interest, which has an intensive rotational spectrum that extends in the submillimeter wave range and far beyond, even at temperatures characteristic for the interstellar medium. It is likely for 13C isotopologue of methylamine to be identified in astronomical surveys, but there is no information available for the 13CH3NH2 millimeter and submillimeter wave spectra. Aims: In this context, to provide reliable predictions of 13CH3NH2 spectrum in millimeter and submillimeter wave ranges, we have studied rotational spectra of the 13C methylamine isotopologue in the frequency range from 48 to 945 GHz. Methods: The spectrum of 13C methylamine was recorded using conventional absorption spectrometers. The analysis of the rotational spectrum of 13C methylamine in the ground vibrational state was performed on the basis of the group-theoretical high-barrier tunneling Hamiltonian that was developed for methylamine. The available multiple observations of the parent methylamine species toward Sgr B2(N) at 1, 2, and 3 mm using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory were used to make a search for interstellar 13CH3NH2. Results: In the recorded spectra, we have assigned 2721 rotational transitions that belong to the ground vibrational state of the 13CH3NH2. These measurements were fitted to the Hamiltonian model that uses 75 parameters to achieve an overall weighted rms deviation of 0.73. On the basis of these spectroscopic results, predictions of transition frequencies in the frequency range up to 950 GHz with J ≤ 50 and Ka ≤ 20 are presented. The search for interstellar 13C methylamine in available observational data was not successful and therefore only an upper limit of 6.5 × 1014 cm-2 can be derived for the column density of 13CH3NH2 toward Sgr B2(N), assuming the same source size, temperature, linewidth, and systemic velocity as for parent methylamine isotopic

  16. The Rotational Spectrum of Singly and Doubly 13C-SUBSTITUTED Dimethylether

    NASA Astrophysics Data System (ADS)

    Koerber, Monika; Endres, Christian P.; Lewen, Frank; Giesen, Thomas F.; Schlemmer, Stephan; Pohl, Roland; Klein, Axel

    2010-06-01

    Dimethylether (DME) is a nearly prolate asymmetric top with two internal rotors (methyl groups) which undergo periodic large amplitude motions and show a complicated torsional splitting of each rotational energy level. Due to its complex spectrum and its high abundance in hot cores such as Orion KL or Sagittarius B2 at temperatures exceeding 100 K, DME is very prominent in astronomical line surveys and contributes to spectral line confusion of such sources. The interpretation of astronomical observations therefore depends on the knowledge of accurate rest frequencies and reliable intensities. Precise predictions for the ground state of DME's main isotopologue are now available up to 2.1 THz In contrast, very little is known about 13C-substituted DME. Only a few data are available on singly 13C-substituted DME, 12CH_3O13CH_3. However, no data are available on doubly 13C-substituted DME, (13CH_3)_2O, yet. While in (13CH_3)_2O the two internal rotating methyl groups are equivalent and the splitting of rotational energy levels into four substates is comparable to the main isotopologue, singly 13C-substituted DME has two non-equivalent internal rotors resulting in torsional splitting of rotational energy levels into five substates. The purpose of our new laboratory measurements is to extend the knowledge on the astrophysically relevant species 12CH_3O13CH_3. To analyze the complicated spectrum resulting from a 13C-enriched sample of DME, containing all different 13C-substituted species as well as the main isotopologue, also precise data on doubly 13C-substituted DME are inevitable. We performed measurements in the frequency region 35-120 GHz using an all solid state spectrometer. Rotational as well as torsional parameters have been obtained for (13CH_3)_2O as well as 12CH_3O13CH_3 by fitting the assigned transitions to an effective rotational Hamiltonian introduced by Peter Groner. C. Comito et al., Astrophys. J. Suppl. Ser. 156, 127-167 (2005) C. P. Endres et al

  17. Asymmetry measurement for (13)C(charged pion,charged pion)(13)C* at T(pi) = 162 MeV

    NASA Astrophysics Data System (ADS)

    Johnson, Kevin William

    1998-12-01

    Left-right asymmetry measurements ( AY) were obtained for charged pion scattering of incident kinetic energy 162 MeV from polarized 13C nuclei over an angular range of 30o to 90o. The experiment was performed at the Los Alamos Meson Physics Facility with the Energetic PIon Channel and Spectrometer (EPICS). The 13C target was made up of frozen beads of toluene consisting of 93% 13C612CH8 cryogenically cooled to 0.45o K by a 3He evaporation refrigerator. Polarization was achieved with the dynamic nuclear polarization method using a 2.5 Tesla magnetic field, target material doping by the paramagnetic substance DTBN, and a polarization driving microwave field of frequency 70.060 GHz for parallel and 70.320 GHz anti-parallel alignment with the applied magnetic field. Average polarization of the 13Cl nuclei was ~17% and for the 1H nuclei was ~54% which was obtained after an initial polarization time period of about 30 minutes. AY measurements were calculated by separately obtaining the excitation yield spectra for the chosen target nuclei spin orientation of up or down with respect to [/bf k]inc×[/bf k]scat of the incident and scattered pion. The separate excitation spectra for up and down were used to derive the difference and polarization scaled sum in a channel-by- channel method to reduce effects of the spectrometer plus polarization magnet acceptance. These difference and sum spectra were statistically fitted to peak shapes calculated to account for the pion energy loss straggling. The ratio of the peak yield of the difference spectra to the sum spectra is Ay. Results of AY for the elastic scattering of π+ and πsp- from 1H are consistent with the values calculated by phase shift analysis. Measured AY for the elastic scattering from 13C are found to be in general small but to exhibit two maxima at approximately 51o and 88o CMS scattering angle of approximate values 0.26 (0.24) and 0.21 (0.41) for π+/ (/pi/sp-) scattering. AY values were also measured for states

  18. Influence of seasonal primary productivity on δ13C of North Atlantic deep-sea benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Corliss, B. H.; Sun, X.; Brown, C. W.; Showers, W. J.

    2006-04-01

    The stable isotopic composition of benthic foraminifera has been widely used to reconstruct deep-ocean circulation, but questions have been raised about the influence of organic carbon flux on the carbon isotopic composition of deep-sea taxa. We show that annual and seasonality of primary productivity in the North Atlantic do not affect δ13C of Planulina wuellerstorfi, but that the intermittency or seasonality of primary production has a significant effect (0.9‰ change over 60° latitude) on δ13C of Epistominella exigua, reflecting the influence of pelagic-benthic coupling and microhabitat preferences on test geochemistry. These results support the use of δ13C of P. wuellerstorfi in paleocirculation studies and suggest that the δ13C of E. exigua can be used to reconstruct seasonality of productivity.

  19. Trends in stomatal density and 13C/12C ratios of Pinus flexilis needles during last glacial-interglacial cycle

    USGS Publications Warehouse

    Van De Water, Peter K.; Leavitt, Steven W.; Betancourt, J.L.

    1994-01-01

    Measurements of stomatal density and ?? 13C of limber pine (Pinus flexilis) needles (leaves) preserved in pack rat middens from the Great Basin reveal shifts in plant physiology and leaf morphology during the last 30,000 years. Sites were selected so as to offset glacial to Holocene climatic differences and thus to isolate the effects of changing atmospheric CO2 levels. Stomatal density decreased ~17 percent and ?? 13C decreased ~1.5 per mil during deglaciation from 15,000 to 12,000 years ago, concomitant with a 30 percent increase in atmospheric CO2. Water-use efficiency increased ~15 percent during deglaciation, if temperature and humidity were held constant and the proxy values for CO2 and ?? 13C of past atmospheres are accurate. The ??13C variations may help constrain hypotheses about the redistribution of carbon between the atmosphere and biosphere during the last glacial-interglacial cycle.

  20. 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.

  1. Galactose oxidation using (13)C in healthy and galactosemic children.

    PubMed

    Resende-Campanholi, D R; Porta, G; Ferrioli, E; Pfrimer, K; Ciampo, L A Del; Junior, J S Camelo

    2015-03-01

    Galactosemia is an inborn error of galactose metabolism that occurs mainly as the outcome of galactose-1-phosphate uridyltransferase (GALT) deficiency. The ability to assess galactose oxidation following administration of a galactose-labeled isotope (1-(13)C-galactose) allows the determination of galactose metabolism in a practical manner. We aimed to assess the level of galactose oxidation in both healthy and galactosemic Brazilian children. Twenty-one healthy children and seven children with galactosemia ranging from 1 to 7 years of age were studied. A breath test was used to quantitate (13)CO2 enrichment in exhaled air before and at 30, 60, and 120 min after the oral administration of 7 mg/kg of an aqueous solution of 1-(13)C-galactose to all children. The molar ratios of (13)CO2 and (12)CO2 were quantified by the mass/charge ratio (m/z) of stable isotopes in each air sample by gas-isotope-ratio mass spectrometry. In sick children, the cumulative percentage of (13)C from labeled galactose (CUMPCD) in the exhaled air ranged from 0.03% at 30 min to 1.67% at 120 min. In contrast, healthy subjects showed a much broader range in CUMPCD, with values from 0.4% at 30 min to 5.58% at 120 min. The study found a significant difference in galactose oxidation between children with and without galactosemia, demonstrating that the breath test is useful in discriminating children with GALT deficiencies. PMID:25608239

  2. 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.

  3. 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.).

  4. Absolute partial decay-branch measurements in 13C

    NASA Astrophysics Data System (ADS)

    Wheldon, C.; Ashwood, N. I.; Barr, M.; Curtis, N.; Freer, M.; Kokalova, Tz.; Malcolm, J. D.; Ziman, V. A.; Faestermann, Th.; Wirth, H.-F.; Hertenberger, R.; Lutter, R.

    2012-10-01

    The 9Be(6Li,d)13C* reaction at a beam energy of 42 MeV has been investigated using a large-acceptance silicon-strip detector array and the high-resolution Q3D magnetic spectrograph. The Q3D facilitated the unambiguous determination of the reaction channel via identification of the deuteron ejectile, thereby providing the spectrum of excited states in 13C in the range from 10.7 to 15.0 MeV. The silicon array was used to detect and identify the 13C recoil-breakup products with efficiencies of up to 49%. The results obtained for the absolute partial branching ratios represent the first complete measurements for states in this energy region and allow the extraction of reduced widths. The quantities measured for Γn0/Γtot and Γn1/Γtot are 0.91±0.11 and ≤0.13 (10.753 MeV), 0.51±0.04 and 0.51±0.04 (10.818 MeV), 0.68±0.03 and 0.42±0.02 (10.996 MeV), 0.49±0.08 and 0.71±0.11 (11.848 MeV), and 0.49±0.08 and 0.53±0.08 (12.130 MeV), respectively. For the two observed higher-lying energy levels, Γα0/Γtot and Γn1/Γtot have been measured as 0.54±0.02 and 0.45±0.02 (13.760 MeV) and 0.94±0.03 and 0.13±0.02 (14.582 MeV), respectively. The consequences for the proposed molecular structures in 13C are explored following the extraction of reduced widths.

  5. 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.

  6. Decarboxylation of [1-(13)C]leucine by hydroxyl radicals.

    PubMed

    Guitton, J; Tinardon, F; Lamrini, R; Lacan, P; Desage, M; Francina, A

    1998-08-01

    The decarboxylation of [1-13C]leucine by hydroxyl radicals was studied by using gas chromatography-isotope ratio mass spectrometry (GC-IRMS) to follow the production of 13CO2. A Fenton reaction between a (Fe2+)-porphyrin and hydrogen peroxide under aerobic conditions yielded hydroxyl radicals. The decarboxylation rates (VLeu) measured by GC-IRMS were dependent on [1-13C]leucine, porphyrin and hydrogen peroxide concentrations. The 13CO2 production was also dependent on bicarbonate or carbon dioxide added in the reaction medium. Bicarbonate facilitated 13CO2 production, whereas carbon dioxide decreased 13CO2 production. Proton effects on some decarboxylation intermediates could explain bicarbonate or carbon dioxide effects. No effect on the decarboxylation rates was observed in the presence of the classical hydroxyl radicals scavengers dimethyl sulfoxide, mannitol, and uric acid. By contrast, a competitive effect with a strong decrease of the decarboxylation rates was observed in the presence of various amino acids: unlabeled leucine, valine, phenylalanine, cysteine, lysine, and histidine. Two reaction products, methyl-4 oxo-2 pentanoate and methyl-3 butanoate were identified by gas chromatography-mass spectrometry in comparison with standards. The present results suggest that [1-13C]leucine can participate to the coordination sphere of (Fe2+)-porphyrin, with a caged process of the hydroxyl radicals which cannot get out of the coordination sphere. PMID:9680180

  7. 13C NMR relaxation in neutral and charged tetra- n-alkyl compounds

    NASA Astrophysics Data System (ADS)

    Bordes, B.; Coletta, F.; Ferrarini, A.; Gottardi, F.; Nordio, P. L.

    1998-05-01

    NMR T1 relaxation times have been measured for 13C nuclei in the alkyl chains of symmetric tetra- n-alkylstannanes dissolved in CDCl 3. The results are interpreted in terms of conformational transitions occurring in the aliphatic chains superimposed to rotational diffusion of the whole molecule. A comparison with analogous tetra- n-alkylammonium salts is performed. Differences are ascribed to changes in the overall rotational diffusion deriving from effects of charge upon formation of ion-pairs and larger aggregates.

  8. 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.

  9. 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

  10. 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

  11. Stable isotope-enhanced two- and three-dimensional diffusion ordered 13C NMR spectroscopy (SIE-DOSY 13C NMR)

    NASA Astrophysics Data System (ADS)

    Vermillion, Karl; Price, Neil P. J.

    2009-06-01

    The feasibility of obtaining high quality homonuclear or heteronuclear diffusion-ordered 13C NMR data is shown to be greatly improved by using 13C isotopically-enriched samples. 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, and a disaccharide and trisaccharide. These 2D spectra were obtained with as little as 8 min of acquisition time. Fully resolved 3D DOSY-HMQC NMR spectra of [U- 13C]xylose, [U- 13C]glucose, and [1- 13C gal]lactose were obtained in 5 h. Sample derivatization with [ carbonyl- 13C]acetate (peracetylation) extends the usefulness of the technique to included non-labeled sugars; the 13C-carbonyl - carbohydrate ring proton 1H- 13C correlations also provide additional structural information, as shown for the 3-D DOSY-HMQC analysis of a mixture of maltotriose and lactose per-[ carbonyl- 13C]acetates.

  12. Hepatic gluconeogenesis influences (13)C enrichment in lactate in human brain tumors during metabolism of [1,2-(13)C]acetate.

    PubMed

    Pichumani, Kumar; Mashimo, Tomoyuki; Vemireddy, Vamsidhara; Kovacs, Zoltan; Ratnakar, James; Mickey, Bruce; Malloy, Craig R; DeBerardinis, Ralph J; Bachoo, Robert M; Maher, Elizabeth A

    2016-07-01

    (13)C-enriched compounds are readily metabolized in human malignancies. Fragments of the tumor, acquired by biopsy or surgical resection, may be acid-extracted and (13)C NMR spectroscopy of metabolites such as glutamate, glutamine, 2-hydroxyglutarate, lactate and others provide a rich source of information about tumor metabolism in situ. Recently we observed (13)C-(13)C spin-spin coupling in (13)C NMR spectra of lactate in brain tumors removed from patients who were infused with [1,2-(13)C]acetate prior to the surgery. We found, in four patients, that infusion of (13)C-enriched acetate was associated with synthesis of (13)C-enriched glucose, detectable in plasma. (13)C labeled glucose derived from [1,2-(13)C]acetate metabolism in the liver and the brain pyruvate recycling in the tumor together lead to the production of the (13)C labeled lactate pool in the brain tumor. Their combined contribution to acetate metabolism in the brain tumors was less than 4.0%, significantly lower than the direct oxidation of acetate in the citric acid cycle in tumors. PMID:27020407

  13. Short-term d13C changes in cultivated soils from Mexico

    NASA Astrophysics Data System (ADS)

    Lounejeva, E.; Etchevers, J.; Morales Puente, P.; Cienfuegos Alvarado, E.; Sedov, S.; Solleiro, E.; Hidalgo, C.

    2007-05-01

    (generally less than -20%o). The common feature for the soils under the Traditional and Traditional improved treatments was a C3 enrichment of the superficial SOM component compared to the underlying layers as a consequence of the dominance of the cultivated C3 species. A similar but more accentuated negative shift is also observed in the SOM from the forest soil (non-cultivated soil d13C -25.2), so the interpretation is uncertain. In the Traditional Organic treatment a clear and perceptible increment of d13C in the SOM carbon signature was observed. This was attributed mainly to the fact that cows manure may contain a lot of C4 coming from feedstuff rich in corn grain that is provided to the animals during grass shortage periods . However, the maize crop introduced in the rotation during the 3rd year had no major effect on the tepetates carbon isotopic signature. The stable isotopic carbon data corresponding to a short period (4 years) of observation in uniformly managed soil ecosystems showed that d13C changed due to the quality of the residues (relative abundance of C3/C4 species) incorporated to the SOC, but this memory is susceptible to undergo changes in the short term and could be rapidly reversed as a consequence of crop management.

  14. 13C measurements on organic aerosol - a comparison of sources with ambient samples

    NASA Astrophysics Data System (ADS)

    Dusek, Ulrike; Meusinger, Carl; Oyama, Beatriz; Holzinger, Rupert; Röckmann, Thomas

    2014-05-01

    The stable carbon isotopes 12C and 13C can be used to get information about sources and processing of organic aerosol (OA). We developed and tested a method to measure δ13C values of OA collected on filter samples in different volatility classes. These filter samples are introduced into an oven, where organic compounds are thermally desorbed in He at different temperatures. The compounds released at each temperature step are oxidized to CO2 using a platinum catalyst at 550 °C. The CO2 is then passed on to an isotope ratio mass spectrometer (IRMS) to measure d13C ratios. With a similar setup the chemical composition at each temperature step can be determined using a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS). System evaluation with controlled test compounds showed that organic compounds usually start evaporating from the filter when their melting point is reached. Isotopic fractionation occurs only if one temperature step is within a few degrees of the melting point of the substance, so that the substance only partially evaporates. However, this effect should be limited in an ambient sample containing thousands of individual chemical compounds. δ13C values of aerosol filter samples do not depend on the sample amount used, i.e. the system shows good linearity. The reproducibility depends somewhat on the sample amount and is usually < ± 0.3 ‰ for oven temperatures up to 200 °C and < ± 0.5 ‰ for oven temperatures greater than 200 °C. We analysed aerosol samples collected in a tunnel in Brazil (vehicular emissions), laboratory generated secondary organic aerosol (SOA) from alpha-pinene ozonolysis, and ambient filter samples from a regional site in the Netherlands, an urban site in Belgium, and Sao Paulo Brazil. First results show that δ13C ratios of SOA and vehicular emissions do not change strongly with oven temperature, i.e. the more refractory organic compounds have similar isotopic composition as the more volatile compounds

  15. Evolution of E. coli on [U-13C]Glucose Reveals a Negligible Isotopic Influence on Metabolism and Physiology

    PubMed Central

    Sandberg, Troy E.; Long, Christopher P.; Gonzalez, Jacqueline E.; Feist, Adam M.; Antoniewicz, Maciek R.; Palsson, Bernhard O.

    2016-01-01

    13C-Metabolic flux analysis (13C-MFA) traditionally assumes that kinetic isotope effects from isotopically labeled compounds do not appreciably alter cellular growth or metabolism, despite indications that some biochemical reactions can be non-negligibly impacted. Here, populations of Escherichia coli were adaptively evolved for ~1000 generations on uniformly labeled 13C-glucose, a commonly used isotope for 13C-MFA. Phenotypic characterization of these evolved strains revealed ~40% increases in growth rate, with no significant difference in fitness when grown on either labeled (13C) or unlabeled (12C) glucose. The evolved strains displayed decreased biomass yields, increased glucose and oxygen uptake, and increased acetate production, mimicking what is observed after adaptive evolution on unlabeled glucose. Furthermore, full genome re-sequencing revealed that the key genetic changes underlying these phenotypic alterations were essentially the same as those acquired during adaptive evolution on unlabeled glucose. Additionally, glucose competition experiments demonstrated that the wild-type exhibits no isotopic preference for unlabeled glucose, and the evolved strains have no preference for labeled glucose. Overall, the results of this study indicate that there are no significant differences between 12C and 13C-glucose as a carbon source for E. coli growth. PMID:26964043

  16. Relayed 13C magnetization transfer: Detection of malate dehydrogenase reaction in vivo

    NASA Astrophysics Data System (ADS)

    Yang, Jehoon; Shen, Jun

    2007-02-01

    Malate dehydrogenase catalyzes rapid interconversion between dilute metabolites oxaloacetate and malate. Both oxaloacetate and malate are below the detection threshold of in vivo MRS. Oxaloacetate is also in rapid exchange with aspartate catalyzed by aspartate aminotransferase, the latter metabolite is observable in vivo using 13C MRS. We hypothesized that the rapid turnover of oxaloacetate can effectively relay perturbation of magnetization between malate and aspartate. Here, we report indirect observation of the malate dehydrogenase reaction by saturating malate C2 resonance at 71.2 ppm and detecting a reduced aspartate C2 signal at 53.2 ppm due to relayed magnetization transfer via oxaloacetate C2 at 201.3 ppm. Using this strategy the rate of the cerebral malate dehydrogenase reaction was determined to be 9 ± 2 μmol/g wet weight/min (means ± SD, n = 5) at 11.7 Tesla in anesthetized adult rats infused with [1,6- 13C 2]glucose.

  17. NMR analyses of the cold cataract. III. /sup 13/C acrylamide studies

    SciTech Connect

    Lerman, S.; Megaw, J.M.; Moran, M.N.

    1985-10-01

    /sup 13/C-enriched acrylamide was employed to further delineate the action of this compound in preventing the cold cataract phenomenon when it is incorporated (in vitro) into young human and rabbit lenses. The extent of acrylamide incorporation, in the dark and with concurrent UV exposure, was monitored by /sup 13/C NMR spectroscopy. These studies provide further evidence that UV exposure causes permanent acrylamide photobinding within the lens. In such lenses, the gamma crystallin fraction of the soluble lens proteins is affected to the greatest extent. It appears to become aggregated and/or combined with the alpha and beta fractions resulting in an apparent loss of most of the gamma monomers. There is also an age-related effect with respect to the amount of acrylamide that can be incorporated into the lens. The decrease in acrylamide incorporation with age directly parallels the age-related decline in gamma crystallin levels.

  18. Four-Component Relativistic DFT Calculations of (13)C Chemical Shifts of Halogenated Natural Substances.

    PubMed

    Casella, Girolamo; Bagno, Alessandro; Komorovsky, Stanislav; Repisky, Michal; Saielli, Giacomo

    2015-12-14

    We have calculated the (13)C NMR chemical shifts of a large ensemble of halogenated organic molecules (81 molecules for a total of 250 experimental (13)C NMR data at four different levels of theory), ranging from small rigid organic compounds, used to benchmark the performance of various levels of theory, to natural substances of marine origin with conformational degrees of freedom. Carbon atoms bonded to heavy halogen atoms, particularly bromine and iodine, are known to be rather challenging when it comes to the prediction of their chemical shifts by quantum methods, due to relativistic effects. In this paper, we have applied the state-of-the-art four-component relativistic density functional theory for the prediction of such NMR properties and compared the performance with two-component and nonrelativistic methods. Our results highlight the necessity to include relativistic corrections within a four-component description for the most accurate prediction of the NMR properties of halogenated organic substances. PMID:26541625

  19. Temporal variability in (13)C of respired CO(2) in a pine and a hardwood forest subject to similar climatic conditions.

    PubMed

    Mortazavi, Behzad; Chanton, Jeffrey P; Prater, James L; Oishi, A Christopher; Oren, Ram; Katul, Gabriel

    2005-01-01

    Temporal variability in the (13)C of foliage (delta(13)C(F)), soil (delta(13)C(S)) and ecosystem (delta(13)C(R)) respired CO(2) was contrasted between a 17.2-m tall evenly aged loblolly pine forest and a 35-m tall unevenly aged mature second growth mixed broadleaf deciduous forest in North Carolina, USA, over a 2-year period. The two forests are located at the Duke Forest within a kilometer of each other and are subject to identical climate and have similar soil types. The delta(13)C(F), collected just prior to dawn, was primarily controlled by the time-lagged vapor pressure deficit (VPD) in both stands; it was used for calculating the ratio of intercellular to ambient CO(2) ( Ci/ Ca). A remarkable similarity was observed in the relationship between Ci/ Ca and time-lagged VPD in these two forests despite large differences in hydraulic characteristics. This similarity emerged as a result of physiological adjustments that compensated for differences in plant hydraulic characteristics, as predicted by a recently proposed equilibrium hypothesis, and has implications to ecophysiological models. We found that in the broadleaf forest, the delta(13)C of forest floor CO(2) efflux dominated the delta(13)C(R), while in the younger pine forest, the delta(13)C of foliage respired CO(2) dominated delta(13)C(R). This dependence resulted in a more variable delta(13)C(R) in the pine forest when compared to the broadleaf forest due to the larger photosynthetic contribution. Given the sensitivity of the atmospheric inversion models to delta(13)C(R), the results demonstrate that these models could be improved by accounting for stand characteristics, in addition to previously recognized effects of moisture availability, when estimating delta(13)C(R). PMID:15340829

  20. Low-field thermal mixing in [1-(13)C] pyruvic acid for brute-force hyperpolarization.

    PubMed

    Peat, David T; Hirsch, Matthew L; Gadian, David G; Horsewill, Anthony J; Owers-Bradley, John R; Kempf, James G

    2016-07-28

    We detail the process of low-field thermal mixing (LFTM) between (1)H and (13)C nuclei in neat [1-(13)C] pyruvic acid at cryogenic temperatures (4-15 K). Using fast-field-cycling NMR, (1)H nuclei in the molecule were polarized at modest high field (2 T) and then equilibrated with (13)C nuclei by fast cycling (∼300-400 ms) to a low field (0-300 G) that activates thermal mixing. The (13)C NMR spectrum was recorded after fast cycling back to 2 T. The (13)C signal derives from (1)H polarization via LFTM, in which the polarized ('cold') proton bath contacts the unpolarised ('hot') (13)C bath at a field so low that Zeeman and dipolar interactions are similar-sized and fluctuations in the latter drive (1)H-(13)C equilibration. By varying mixing time (tmix) and field (Bmix), we determined field-dependent rates of polarization transfer (1/τ) and decay (1/T1m) during mixing. This defines conditions for effective mixing, as utilized in 'brute-force' hyperpolarization of low-γ nuclei like (13)C using Boltzmann polarization from nearby protons. For neat pyruvic acid, near-optimum mixing occurs for tmix∼ 100-300 ms and Bmix∼ 30-60 G. Three forms of frozen neat pyruvic acid were tested: two glassy samples, (one well-deoxygenated, the other O2-exposed) and one sample pre-treated by annealing (also well-deoxygenated). Both annealing and the presence of O2 are known to dramatically alter high-field longitudinal relaxation (T1) of (1)H and (13)C (up to 10(2)-10(3)-fold effects). Here, we found smaller, but still critical factors of ∼(2-5)× on both τ and T1m. Annealed, well-deoxygenated samples exhibit the longest time constants, e.g., τ∼ 30-70 ms and T1m∼ 1-20 s, each growing vs. Bmix. Mixing 'turns off' for Bmix > ∼100 G. That T1m≫τ is consistent with earlier success with polarization transfer from (1)H to (13)C by LFTM. PMID:27362505

  1. The 4051 Å Comet Band of 13C3

    NASA Astrophysics Data System (ADS)

    Haddad, M. A.; Zhao, D.; Linnartz, H.; Ubachs, W.

    2014-02-01

    The tricarbon C3 molecule has been detected in a number of translucent interstellar clouds via its $A^1\\Piu-X^1\\Sigmag+$ (000-000) electronic `comet' band around 4051 Å. So far, it is the largest molecule unambiguously identified in the diffuse interstellar medium. In this work, rotationally resolved laboratory spectra are presented for the corresponding transition of the 13C3 isotopologue. The spectra are recorded in direct absorption using cavity ring-down spectroscopy in combination with a supersonic plasma jet. A rotational analysis yields accurate spectroscopic parameters. In contrast to 12C3, no significant perturbations are found for (e- or f-parity) levels up to J' = 18 in the A 1Π upper electronic state.

  2. 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.

  3. Multiscale computational modeling of (13)C DNP in liquids.

    PubMed

    Küçük, Sami Emre; Sezer, Deniz

    2016-04-14

    Dynamic nuclear polarization (DNP) enables the substantial enhancement of the NMR signal intensity in liquids. While proton DNP is dominated by the dipolar interaction between the electron and nuclear spins, the Fermi contact (scalar) interaction is equally important for heavier nuclei. The impossibility to predict the magnitude and field dependence of the scalar contribution hampers the application of high-field DNP to nuclei other than (1)H. We demonstrate that molecular dynamics (MD) simulations followed by density functional calculations of the Fermi contacts along the MD trajectory lead to quantitative agreement with the DNP coupling factors of the methyl and carbonyl carbons of acetone in water at 0.35 T. Thus, the accurate calculation of scalar-dominated DNP enhancement at a desired magnetic field is demonstrated for the first time. For liquid chloroform at fields above 9 T, our methodology predicts direct (13)C DNP enhancements that are two orders of magnitude larger than those of (1)H. PMID:27001446

  4. 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

  5. Climatic significance of D/H and13C/12C ratios in Irish oak cellulose

    NASA Astrophysics Data System (ADS)

    Baillie, M. G. L.; Pilcher, J. R.; Pollard, A. M.; Ramesh, R.

    2000-03-01

    δD and δ13C analyses of cellulose nitrate from two modern Irish oak trees that form part of the 7400 year long chronology were carried out, covering a period of 123 years (1861-1983 A.D.) with a 5 year resolution so as to assess the potential of this long chronology for retrieval of palaeoenvironmental data. One of the trees (Q5293) showed significant correlations of δD, δ13 C and ring width with mean annual temperatures as recorded at the Armagh weather station nearby and the mean fall temperatures of Central England. The other tree (Q5296) did not exhibit any significant climatic correlations either because it grew utilizing a nearby permanent source of ground water or because the intra-ring isotopic variations in Irish oak are significant enough to mask the climatic signal. Whilst our results have given a positive indication of the usefulness of these trees for palaeoenvironmental information, more trees need to be analysed to confirm our findings. Even though one of the trees did not exhibit climatic correlations, both trees show a significant positive correlation of δ13C and a negative correlation of δD with ring width variations. Furthermore, two tree samples that grew during the 1620s B.C., when a volcano is thought to have erupted on the Aegean island of Santorini, show increased δD and decreased δ13C for one to two decades following the eruption, though the magnitudes of change seem to vary with site and trees. We have proposed a possible mechanism based on tree phenology to explain both the above effects.

  6. A comparison of quantitative methods for clinical imaging with hyperpolarized (13)C-pyruvate.

    PubMed

    Daniels, Charlie J; McLean, Mary A; Schulte, Rolf F; Robb, Fraser J; Gill, Andrew B; McGlashan, Nicholas; Graves, Martin J; Schwaiger, Markus; Lomas, David J; Brindle, Kevin M; Gallagher, Ferdia A

    2016-04-01

    Dissolution dynamic nuclear polarization (DNP) enables the metabolism of hyperpolarized (13)C-labelled molecules, such as the conversion of [1-(13)C]pyruvate to [1-(13)C]lactate, to be dynamically and non-invasively imaged in tissue. Imaging of this exchange reaction in animal models has been shown to detect early treatment response and correlate with tumour grade. The first human DNP study has recently been completed, and, for widespread clinical translation, simple and reliable methods are necessary to accurately probe the reaction in patients. However, there is currently no consensus on the most appropriate method to quantify this exchange reaction. In this study, an in vitro system was used to compare several kinetic models, as well as simple model-free methods. Experiments were performed using a clinical hyperpolarizer, a human 3 T MR system, and spectroscopic imaging sequences. The quantitative methods were compared in vivo by using subcutaneous breast tumours in rats to examine the effect of pyruvate inflow. The two-way kinetic model was the most accurate method for characterizing the exchange reaction in vitro, and the incorporation of a Heaviside step inflow profile was best able to describe the in vivo data. The lactate time-to-peak and the lactate-to-pyruvate area under the curve ratio were simple model-free approaches that accurately represented the full reaction, with the time-to-peak method performing indistinguishably from the best kinetic model. Finally, extracting data from a single pixel was a robust and reliable surrogate of the whole region of interest. This work has identified appropriate quantitative methods for future work in the analysis of human hyperpolarized (13)C data. PMID:27414749

  7. 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.

  8. A Catalyzing Phantom for Reproducible Dynamic Conversion of Hyperpolarized [1-13C]-Pyruvate

    PubMed Central

    Walker, Christopher M.; Lee, Jaehyuk; Ramirez, Marc S.; Schellingerhout, Dawid; Millward, Steven; Bankson, James A.

    2013-01-01

    In vivo real time spectroscopic imaging of hyperpolarized 13C labeled metabolites shows substantial promise for the assessment of physiological processes that were previously inaccessible. However, reliable and reproducible methods of measurement are necessary to maximize the effectiveness of imaging biomarkers that may one day guide personalized care for diseases such as cancer. Animal models of human disease serve as poor reference standards due to the complexity, heterogeneity, and transient nature of advancing disease. In this study, we describe the reproducible conversion of hyperpolarized [1-13C]-pyruvate to [1-13C]-lactate using a novel synthetic enzyme phantom system. The rate of reaction can be controlled and tuned to mimic normal or pathologic conditions of varying degree. Variations observed in the use of this phantom compare favorably against within-group variations observed in recent animal studies. This novel phantom system provides crucial capabilities as a reference standard for the optimization, comparison, and certification of quantitative imaging strategies for hyperpolarized tracers. PMID:23977006

  9. Temperature-mediated changes in microbial carbon use efficiency and 13C discrimination

    NASA Astrophysics Data System (ADS)

    Lehmeier, C. A.; Ballantyne, F., IV; Min, K.; Billings, S. A.

    2015-10-01

    Understanding how carbon dioxide (CO2) flux from soils feeds back to climate warming depends in part on our ability to quantify the efficiency with which microorganisms convert soil organic carbon (C) into either biomass or CO2. Quantifying ecosystem-level respiratory CO2 losses often also requires assumptions about stable C isotope fractionations associated with the microbial transformation of soil organic substrates. However, the diversity of organic substrates' δ13C and the challenges of measuring microbial C use efficiency (CUE) in soils fundamentally limit our ability to project soil, and thus ecosystem, C budgets in a warming climate. Here, we quantify the effect of temperature on C fluxes during metabolic transformations of cellobiose, a common microbial substrate, by a cosmopolitan soil microorganism growing at a constant rate. Specific respiration rate increased by 250 % between 13 and 26.5 °C, decreasing CUE from 77 to 56 %. Specific respiration rate was positively correlated with an increase in respiratory 13C discrimination from 4.4 to 6.7 ‰ across the same temperature range. This first demonstration of a direct link between temperature, microbial CUE and associated isotope fluxes provides a critical step towards understanding δ13C of respired CO2 at multiple scales, and towards a framework for predicting future soil C fluxes.

  10. Temperature-mediated changes in microbial carbon use efficiency and 13C discrimination

    NASA Astrophysics Data System (ADS)

    Lehmeier, Christoph A.; Ballantyne, Ford, IV; Min, Kyungjin; Billings, Sharon A.

    2016-06-01

    Understanding how carbon dioxide (CO2) flux from ecosystems feeds back to climate warming depends in part on our ability to quantify the efficiency with which microorganisms convert organic carbon (C) into either biomass or CO2. Quantifying ecosystem-level respiratory CO2 losses often also requires assumptions about stable C isotope fractionations associated with the microbial transformation of organic substrates. However, the diversity of organic substrates' δ13C and the challenges of measuring microbial C use efficiency (CUE) in their natural environment fundamentally limit our ability to project ecosystem C budgets in a warming climate. Here, we quantify the effect of temperature on C fluxes during metabolic transformations of cellobiose, a common microbial substrate, by a cosmopolitan microorganism growing at a constant rate. Biomass C specific respiration rate increased by 250 % between 13 and 26.5 °C, decreasing CUE from 77 to 56 %. Biomass C specific respiration rate was positively correlated with an increase in respiratory 13C discrimination from 4.4 to 6.7 ‰ across the same temperature range. This first demonstration of a direct link between temperature, microbial CUE, and associated isotope fluxes provides a critical step towards understanding δ13C of respired CO2 at multiple scales, and towards a framework for predicting future ecosystem C fluxes.

  11. 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

  12. Predicting outcomes of steady-state 13C isotope tracing experiments using Monte Carlo sampling

    PubMed Central

    2012-01-01

    Background Carbon-13 (13C) analysis is a commonly used method for estimating reaction rates in biochemical networks. The choice of carbon labeling pattern is an important consideration when designing these experiments. We present a novel Monte Carlo algorithm for finding the optimal substrate input label for a particular experimental objective (flux or flux ratio). Unlike previous work, this method does not require assumption of the flux distribution beforehand. Results Using a large E. coli isotopomer model, different commercially available substrate labeling patterns were tested computationally for their ability to determine reaction fluxes. The choice of optimal labeled substrate was found to be dependent upon the desired experimental objective. Many commercially available labels are predicted to be outperformed by complex labeling patterns. Based on Monte Carlo Sampling, the dimensionality of experimental data was found to be considerably less than anticipated, suggesting that effectiveness of 13C experiments for determining reaction fluxes across a large-scale metabolic network is less than previously believed. Conclusions While 13C analysis is a useful tool in systems biology, high redundancy in measurements limits the information that can be obtained from each experiment. It is however possible to compute potential limitations before an experiment is run and predict whether, and to what degree, the rate of each reaction can be resolved. PMID:22289253

  13. Dynamic nuclear polarization of carbonyl and methyl 13C spins in acetate using trityl OX063

    NASA Astrophysics Data System (ADS)

    Niedbalski, Peter; Parish, Christopher; Lumata, Lloyd

    2015-03-01

    Hyperpolarization via dissolution dynamic nuclear polarization (DNP) is a physics technique that amplifies the magnetic resonance signals by several thousand-fold for biomedical NMR spectroscopy and imaging (MRI). Herein we have investigated the effect of carbon-13 isotopic location on the DNP of acetate (one of the biomolecules commonly used for hyperpolarization) at 3.35 T and 1.4 K using a narrow ESR linewidth free radical trityl OX063. We have found that the carbonyl 13C spins yielded about twice the polarization produced in methyl 13C spins. Deuteration of the methyl group, beneficial in the liquid-state, did not produce an improvement in the polarization level at cryogenic conditions. Concurrently, the solid-state nuclear relaxation of these samples correlate with the polarization levels achieved. These results suggest that the location of the 13C isotopic labeling in acetate has a direct impact on the solid-state polarization achieved and is mainly governed by the nuclear relaxation leakage factor.

  14. 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.

  15. Galactic Chemical Evolution and Solar s-process Abundances: Dependence on the 13C-pocket Structure

    NASA Astrophysics Data System (ADS)

    Bisterzo, S.; Travaglio, C.; Gallino, R.; Wiescher, M.; Käppeler, F.

    2014-05-01

    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 13C pocket, which may affect the efficiency of the 13C(α, n)16O reaction, the major neutron source of the s process. First, keeping the same 13C profile adopted so far, we modify by a factor of two the mass involved in the pocket; second, we assume a flat 13C 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 13C pocket once a different weighted range of 13C-pocket strengths is assumed. We obtain that, independently of the internal structure of the 13C pocket, the missing solar system s-process contribution in the range from A = 90 to 130 remains essentially the same.

  16. Hyperpolarized (13) C-lactate to (13) C-bicarbonate ratio as a biomarker for monitoring the acute response of anti-vascular endothelial growth factor (anti-VEGF) treatment.

    PubMed

    Park, Jae Mo; Spielman, Daniel M; Josan, Sonal; Jang, Taichang; Merchant, Milton; Hurd, Ralph E; Mayer, Dirk; Recht, Lawrence D

    2016-05-01

    Hyperpolarized [1-(13) C]pyruvate MRS provides a unique imaging opportunity to study the reaction kinetics and enzyme activities of in vivo metabolism because of its favorable imaging characteristics and critical position in the cellular metabolic pathway, where it can either be reduced to lactate (reflecting glycolysis) or converted to acetyl-coenzyme A and bicarbonate (reflecting oxidative phosphorylation). Cancer tissue metabolism is altered in such a way as to result in a relative preponderance of glycolysis relative to oxidative phosphorylation (i.e. Warburg effect). Although there is a strong theoretical basis for presuming that readjustment of the metabolic balance towards normal could alter tumor growth, a robust noninvasive in vivo tool with which to measure the balance between these two metabolic processes has yet to be developed. Until recently, hyperpolarized (13) C-pyruvate imaging studies had focused solely on [1-(13) C]lactate production because of its strong signal. However, without a concomitant measure of pyruvate entry into the mitochondria, the lactate signal provides no information on the balance between the glycolytic and oxidative metabolic pathways. Consistent measurement of (13) C-bicarbonate in cancer tissue, which does provide such information, has proven difficult, however. In this study, we report the reliable measurement of (13) C-bicarbonate production in both the healthy brain and a highly glycolytic experimental glioblastoma model using an optimized (13) C MRS imaging protocol. With the capacity to obtain signal in all tumors, we also confirm for the first time that the ratio of (13) C-lactate to (13) C-bicarbonate provides a more robust metric relative to (13) C-lactate for the assessment of the metabolic effects of anti-angiogenic therapy. Our data suggest a potential application of this ratio as an early biomarker to assess therapeutic effectiveness. Furthermore, although further study is needed, the results suggest that anti

  17. Metabolic Pathway Confirmation and Discovery Through 13C-labeling of Proteinogenic Amino Acids

    PubMed Central

    You, Le; Page, Lawrence; Feng, Xueyang; Berla, Bert; Pakrasi, Himadri B.; Tang, Yinjie J.

    2012-01-01

    Microbes have complex metabolic pathways that can be investigated using biochemistry and functional genomics methods. One important technique to examine cell central metabolism and discover new enzymes is 13C-assisted metabolism analysis 1. This technique is based on isotopic labeling, whereby microbes are fed with a 13C labeled substrates. By tracing the atom transition paths between metabolites in the biochemical network, we can determine functional pathways and discover new enzymes. As a complementary method to transcriptomics and proteomics, approaches for isotopomer-assisted analysis of metabolic pathways contain three major steps 2. First, we grow cells with 13C labeled substrates. In this step, the composition of the medium and the selection of labeled substrates are two key factors. To avoid measurement noises from non-labeled carbon in nutrient supplements, a minimal medium with a sole carbon source is required. Further, the choice of a labeled substrate is based on how effectively it will elucidate the pathway being analyzed. Because novel enzymes often involve different reaction stereochemistry or intermediate products, in general, singly labeled carbon substrates are more informative for detection of novel pathways than uniformly labeled ones for detection of novel pathways3, 4. Second, we analyze amino acid labeling patterns using GC-MS. Amino acids are abundant in protein and thus can be obtained from biomass hydrolysis. Amino acids can be derivatized by N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (TBDMS) before GC separation. TBDMS derivatized amino acids can be fragmented by MS and result in different arrays of fragments. Based on the mass to charge (m/z) ratio of fragmented and unfragmented amino acids, we can deduce the possible labeled patterns of the central metabolites that are precursors of the amino acids. Third, we trace 13C carbon transitions in the proposed pathways and, based on the isotopomer data, confirm whether these

  18. Use of the Biphasic (13)C-Sucrose/Glucose Breath Test to Assess Sucrose Maldigestion in Adults with Functional Bowel Disorders.

    PubMed

    Opekun, Antone R; Balesh, Albert M; Shelby, Harold T

    2016-01-01

    Sucrase insufficiency has been observed in children with of functional bowel disorders (FBD) and symptoms of dietary carbohydrate intolerance may be indistinguishable from those of FBD. A two-phase (13)C-sucrose/(13)C-glucose breath test ((13)C-S/GBT) was used to assess sucrase activity because disaccharidase assays are seldom performed in adults. When (13)C-sucrose is hydrolyzed to liberate monosaccharides, oxidation to (13)CO2 is a proportional indicator of sucrase activity. Subsequently, (13)C-glucose oxidation rate was determined after a secondary substrate ingestion (superdose) to adjust for individual habitus effects (Phase II). (13)CO2 enrichment recovery ratio from (13)C-sucrose and secondary (13)C-glucose loads reflect the individualized sucrase activity [Coefficient of Glucose Oxidation for Sucrose (CGO-S)]. To determine if sucrase insufficiency could be a factor in FBD, (13)C-S/GBT was validated using subjects with known sucrase gene mutation status by comparing (13)CO2-breath enrichment with plasma (13)C-glucose enrichment. (13)C-S/GBT was used to assess sucrose digestion in FBD patients and asymptomatic controls. (13)CO2-breath enrichment correlated with the appearance of (13)C-sucrose-derived glucose in plasma (r (2) = 0.80). Mean, control group CGO-S-enrichment outcomes were 1.01 at 60', 0.92 at 75', and 0.96 at mean 60'-75' with normal CGO-S defined as >0.85 (95% C.I.). In contrast, FBD patients demonstrated lower CGO-S values of 0.77 at 60', 0.77 at 75', and 0.76 at mean 60'-75' (Chi Square: 6.55; p < 0.01), which points to sucrose maldigestion as a cause of FBD. PMID:27579322

  19. Use of the Biphasic 13C-Sucrose/Glucose Breath Test to Assess Sucrose Maldigestion in Adults with Functional Bowel Disorders

    PubMed Central

    Balesh, Albert M.; Shelby, Harold T.

    2016-01-01

    Sucrase insufficiency has been observed in children with of functional bowel disorders (FBD) and symptoms of dietary carbohydrate intolerance may be indistinguishable from those of FBD. A two-phase 13C-sucrose/13C-glucose breath test (13C-S/GBT) was used to assess sucrase activity because disaccharidase assays are seldom performed in adults. When 13C-sucrose is hydrolyzed to liberate monosaccharides, oxidation to 13CO2 is a proportional indicator of sucrase activity. Subsequently, 13C-glucose oxidation rate was determined after a secondary substrate ingestion (superdose) to adjust for individual habitus effects (Phase II). 13CO2 enrichment recovery ratio from 13C-sucrose and secondary 13C-glucose loads reflect the individualized sucrase activity [Coefficient of Glucose Oxidation for Sucrose (CGO-S)]. To determine if sucrase insufficiency could be a factor in FBD, 13C-S/GBT was validated using subjects with known sucrase gene mutation status by comparing 13CO2-breath enrichment with plasma 13C-glucose enrichment. 13C-S/GBT was used to assess sucrose digestion in FBD patients and asymptomatic controls. 13CO2-breath enrichment correlated with the appearance of 13C-sucrose-derived glucose in plasma (r2 = 0.80). Mean, control group CGO-S-enrichment outcomes were 1.01 at 60′, 0.92 at 75′, and 0.96 at mean 60′–75′ with normal CGO-S defined as >0.85 (95% C.I.). In contrast, FBD patients demonstrated lower CGO-S values of 0.77 at 60′, 0.77 at 75′, and 0.76 at mean 60′–75′ (Chi Square: 6.55; p < 0.01), which points to sucrose maldigestion as a cause of FBD. PMID:27579322

  20. Changes and their possible causes in δ13C of dark-respired CO2 and its putative bulk and soluble sources during maize ontogeny.

    PubMed

    Ghashghaie, Jaleh; Badeck, Franz W; Girardin, Cyril; Huignard, Christophe; Aydinlis, Zackarie; Fonteny, Charlotte; Priault, Pierrick; Fresneau, Chantal; Lamothe-Sibold, Marlène; Streb, Peter; Terwilliger, Valery J

    2016-04-01

    The issues of whether, where, and to what extent carbon isotopic fractionations occur during respiration affect interpretations of plant functions that are important to many disciplines across the natural sciences. Studies of carbon isotopic fractionation during dark respiration in C3 plants have repeatedly shown respired CO2 to be (13)C enriched relative to its bulk leaf sources and (13)C depleted relative to its bulk root sources. Furthermore, two studies showed respired CO2 to become progressively (13)C enriched during leaf ontogeny and (13)C depleted during root ontogeny in C3 legumes. As such data on C4 plants are scarce and contradictory, we investigated apparent respiratory fractionations of carbon and their possible causes in different organs of maize plants during early ontogeny. As in the C3 plants, leaf-respired CO2 was (13)C enriched whereas root-respired CO2 was (13)C depleted relative to their putative sources. In contrast to the findings for C3 plants, however, not only root- but also leaf-respired CO2 became more (13)C depleted during ontogeny. Leaf-respired CO2 was highly (13)C enriched just after light-dark transition but the enrichment rapidly decreased over time in darkness. We conclude that (i) although carbon isotopic fractionations in C4 maize and leguminous C3 crop roots are similar, increasing phosphoenolpyruvate-carboxylase activity during maize ontogeny could have produced the contrast between the progressive (13)C depletion of maize leaf-respired CO2 and (13)C enrichment of C3 leaf-respired CO2 over time, and (ii) in both maize and C3 leaves, highly (13)C enriched leaf-respired CO2 at light-to-dark transition and its rapid decrease during darkness, together with the observed decrease in leaf malate content, may be the result of a transient effect of light-enhanced dark respiration. PMID:26970389

  1. 13C-18O bonding (Δ47) in deep-sea corals: a calibration study

    NASA Astrophysics Data System (ADS)

    Kimball, J. B.; Tripati, A.; Dunbar, R. B.; Eagle, R.

    2013-12-01

    Deep-sea corals are a potentially valuable archive of temperature in intermediate and deep waters, regions for which a paucity of temperature data exists. These archives could give valuable insight into the natural variability of areas of the ocean that play an active role in large-scale climate dynamics. Due to significant 'vital effects' (i.e., non-equilibrium mineral compositions) in δ18O, however, deep-sea coral have been challenging to develop as a paleotemperature proxy. Clumped-isotope paleothermometry is a new method that may circumvent some of the known complications with δ18O paleotemperature analysis in deep-sea coral. This geothermometer is based on the ordering of heavy 13C-18O ';clumps' in carbonate minerals. Initial calibration studies have shown that the method is independent from the solution chemistry of the precipitating fluids as well as 'vital effects' in deep-sea corals and other types of carbonates. Some kinetic effects have been observed in tropical corals and speleothems. Here we report new data in order to further develop clumped isotopes as a paleothermometer in deep-sea corals as well as to investigate taxon-specific effects. 13C-18O bond ordering was analyzed in live-collected scleractinian (Enallopsammia sp.) and gorgonian (Isididae and Coralliidae) deep-sea corals. We determined mass 47 anomalies in samples (Δ47), which refers to the parts per thousand excess of 13C-18O-16O in CO2 produced on acid digestion of a sample, relative to the amount predicted to be present if isotopes were randomly distributed amongst all CO2 isotopologues. Measured Δ47 values were compared to in situ temperatures and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects.

  2. 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

  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. PASADENA hyperpolarization of 13C biomolecules: equipment design and installation

    PubMed Central

    Hövener, Jan-Bernd; Chekmenev, Eduard Y.; Harris, Kent C.; Perman, William H.; Robertson, Larry W.; Bhattacharya, Pratip

    2009-01-01

    Object The PASADENA method has achieved hyperpolarization of 16–20% (exceeding 40,000-fold signal enhancement at 4.7 T), in liquid samples of biological molecules relevant to in vivo MRI and MRS. However, there exists no commercial apparatus to perform this experiment conveniently and reproducibly on the routine basis necessary for translation of PASADENA to questions of biomedical importance. The present paper describes equipment designed for rapid production of six to eight liquid samples per hour with high reproducibility of hyperpolarization. Materials and methods Drawing on an earlier, but unpublished, prototype, we provide diagrams of a delivery circuit, a laminar-flow reaction chamber within a low field NMR contained in a compact, movable housing. Assembly instructions are provided from which a computer driven, semiautomated PASADENA polarizer can be constructed. Results Together with an available parahydrogen generator, the polarizer, which can be operated by a single investigator, completes one cycle of hyperpolarization each 52 s. Evidence of efficacy is presented. In contrast to competing, commercially available devices for dynamic nuclear polarization which characteristically require 90 min per cycle, PASADENA provides a low-cost alternative for high throughput. Conclusions This equipment is suited to investigators who have an established small animal NMR and wish to explore the potential of heteronuclear (13C and 15N) MRI, MRS, which harnesses the enormous sensitivity gain offered by hyperpolarization. PMID:19067008

  5. 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.

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. Characterization and quantitation of urinary metabolites of [1,2,3-13C]acrylamide in rats and mice using 13C nuclear magnetic resonance spectroscopy.

    PubMed

    Sumner, S C; MacNeela, J P; Fennell, T R

    1992-01-01

    Acrylamide, widely used for the production of polymers and as a grouting agent, causes neurotoxic effects in humans and neurotoxic, genotoxic, reproductive, and carcinogenic effects in laboratory animals. In this study, 13C NMR spectroscopy was used to detect metabolites of acrylamide directly in the urine of rats and mice following administration of [1,2,3-13C]acrylamide (50 mg/kg po). Two-dimensional NMR experiments were used to correlate carbon signals for each metabolite in the urine samples and to determine the number of hydrogens attached to each carbon. Metabolite structures were identified from the NMR data together with calculated values of shift for biochemically feasible metabolites and by comparison with standards. The metabolites assigned in rat and mouse urine are N-acetyl-S-(3-amino-3-oxopropyl)cysteine, N-acetyl-S-(3-amino-2-hydroxy-3-oxopropyl)cysteine, N-acetyl-S-(1-carbamoyl-2-hydroxy-ethyl)cysteine, glycidamide, and 2,3-dihydroxypropionamide. These metabolites arise from direct conjugation of acrylamide with glutathione or from oxidation to the epoxide, glycidamide, and further metabolism. Acrylamide was also detected in the urine. Quantitation was carried out by integrating the metabolite carbon signals with respect to that of dioxane added at a known concentration. The major metabolite for both the rat (70% of total metabolites excreted) and the mouse (40%) was formed from direct conjugation of acrylamide with glutathione. The remaining metabolites for the rat (30%) and mouse (60%) are derived from glycidamide. The species differences in extent of metabolism through glycidamide may have important consequences for the toxic and carcinogenic effects of acrylamide. PMID:1581543

  12. 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.

  13. 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...

  14. 1H to 13C Energy Transfer in Solid State NMR Spectroscopy of Natural Organic Systems

    NASA Astrophysics Data System (ADS)

    Berns, Anne E.; Conte, Pellegrino

    2010-05-01

    ., van Lagen, B., Buurman, P. & de Jager, P.A., 1997. Quantitative Aspects of Solid-State 13C-NMR Spectra of Humic Substances from Soils of Volcanic Systems. Geoderma, 80, 327-338. Conte, P., Piccolo, A., van Lagen, B., Buurman, P. & Hemminga, M.A., 2002. Elemental quantitation of natural organic matter by CPMAS C-13 NMR spectroscopy. Solid State Nuclear Magnetic Resonance, 21, 158-170. Conte, P., Spaccini, R. & Piccolo, A., 2004. State of the art of CPMAS C-13-NMR spectroscopy applied to natural organic matter. Progress in Nuclear Magnetic Resonance Spectroscopy, 44, 215-223. Dria, K.J., Sachleben, J.R. & Hatcher, P.G., 2002. Solid-state carbon-13 nuclear magnetic resonance of humic acids at high magnetic field strengths. Journal of Environmental Quality, 31, 393-401. Kiem, R., Knicker, H., Korschens, M. & Kogel-Knabner, I., 2000. Refractory organic carbon in C-depleted arable soils, as studied by C-13 NMR spectroscopy and carbohydrate analysis. Organic Geochemistry, 31, 655-668. Kögel-Knabner, I., 2000. Analytical approaches for characterizing soil organic matter. Organic Geochemistry, 31, 609-625. Mao, J.D., Hu, W.G., Schmidt-Rohr, K., Davies, G., Ghabbour, E.A. & Xing, B., 2000. Quantitative characterization of humic substances by solid-state carbon-13 nuclear magnetic resonance. Soil Science Society of America Journal, 64, 873-884. Metz, G., Ziliox, M. & Smith, S.O., 1996. Towards quantitative CP-MAS NMR. Solid State Nuclear Magnetic Resonance, 7, 155-160. Preston, C.M., 2001. Carbon-13 solid-state NMR of soil organic matter - using the technique effectively. Canadian Journal of Soil Science, 81, 255-270. Smernik, R.J. & Oades, J.M., 2000a. The use of spin counting for determining quantitation in solid state C-13 NMR spectra of natural organic matter 1. Model systems and the effects of paramagnetic impurities. Geoderma, 96, 101-129. Smernik, R.J. & Oades, J.M., 2000b. The use of spin counting for determining quantitation in solid state C-13 NMR spectra of natural

  15. Plant diversity moderates drought stress in grasslands: Implications from a large real-world study on (13)C natural abundances.

    PubMed

    Klaus, Valentin H; Hölzel, Norbert; Prati, Daniel; Schmitt, Barbara; Schöning, Ingo; Schrumpf, Marion; Solly, Emily F; Hänsel, Falk; Fischer, Markus; Kleinebecker, Till

    2016-10-01

    Land-use change and intensification play a key role in the current biodiversity crisis. The resulting species loss can have severe effects on ecosystem functions and services, thereby increasing ecosystem vulnerability to climate change. We explored whether land-use intensification (i.e. fertilization intensity), plant diversity and other potentially confounding environmental factors may be significantly related to water use (i.e. drought stress) of grassland plants. Drought stress was assessed using δ(13)C abundances in aboveground plant biomass of 150 grassland plots across a gradient of land-use intensity. Under water shortage, plants are forced to increasingly take up the heavier (13)C due to closing stomata leading to an enrichment of (13)C in biomass. Plants were sampled at the community level and for single species, which belong to three different functional groups (one grass, one herb, two legumes). Results show that plant diversity was significantly related to the δ(13)C signal in community, grass and legume biomass indicating that drought stress was lower under higher diversity, although this relation was not significant for the herb species under study. Fertilization, in turn, mostly increased drought stress as indicated by more positive δ(13)C values. This effect was mostly indirect by decreasing plant diversity. In line with these results, we found similar patterns in the δ(13)C signal of the organic matter in the topsoil, indicating a long history of these processes. Our study provided strong indication for a positive biodiversity-ecosystem functioning relationship with reduced drought stress at higher plant diversity. However, it also underlined a negative reinforcing situation: as land-use intensification decreases plant diversity in grasslands, this might subsequently increases drought sensitivity. Vice-versa, enhancing plant diversity in species-poor agricultural grasslands may moderate negative effects of future climate change. PMID:27220098

  16. Global patterns in leaf 13C discrimination and implications for studies of past and future climate.

    PubMed

    Diefendorf, Aaron F; Mueller, Kevin E; Wing, Scott L; Koch, Paul L; Freeman, Katherine H

    2010-03-30

    Fractionation of carbon isotopes by plants during CO(2) uptake and fixation (Delta(leaf)) varies with environmental conditions, but quantitative patterns of Delta(leaf) across environmental gradients at the global scale are lacking. This impedes interpretation of variability in ancient terrestrial organic matter, which encodes climatic and ecological signals. To address this problem, we converted 3,310 published leaf delta(13)C values into mean Delta(leaf) values for 334 woody plant species at 105 locations (yielding 570 species-site combinations) representing a wide range of environmental conditions. Our analyses reveal a strong positive correlation between Delta(leaf) and mean annual precipitation (MAP; R(2) = 0.55), mirroring global trends in gross primary production and indicating stomatal constraints on leaf gas-exchange, mediated by water supply, are the dominant control of Delta(leaf) at large spatial scales. Independent of MAP, we show a lesser, negative effect of altitude on Delta(leaf) and minor effects of temperature and latitude. After accounting for these factors, mean Delta(leaf) of evergreen gymnosperms is lower (by 1-2.7 per thousand) than for other woody plant functional types (PFT), likely due to greater leaf-level water-use efficiency. Together, environmental and PFT effects contribute to differences in mean Delta(leaf) of up to 6 per thousand between biomes. Coupling geologic indicators of ancient precipitation and PFT (or biome) with modern Delta(leaf) patterns has potential to yield more robust reconstructions of atmospheric delta(13)C values, leading to better constraints on past greenhouse-gas perturbations. Accordingly, we estimate a 4.6 per thousand decline in the delta(13)C of atmospheric CO(2) at the onset of the Paleocene-Eocene Thermal Maximum, an abrupt global warming event approximately 55.8 Ma. PMID:20231481

  17. Forward Modeling of Fluctuating Dietary 13C Signals to Validate 13C Turnover Models of Milk and Milk Components from a Diet-Switch Experiment

    PubMed Central

    Braun, Alexander; Schneider, Stephan; Auerswald, Karl; Bellof, Gerhard; Schnyder, Hans

    2013-01-01

    Isotopic variation of food stuffs propagates through trophic systems. But, this variation is dampened in each trophic step, due to buffering effects of metabolic and storage pools. Thus, understanding of isotopic variation in trophic systems requires knowledge of isotopic turnover. In animals, turnover is usually quantified in diet-switch experiments in controlled conditions. Such experiments usually involve changes in diet chemical composition, which may affect turnover. Furthermore, it is uncertain if diet-switch based turnover models are applicable under conditions with randomly fluctuating dietary input signals. Here, we investigate if turnover information derived from diet-switch experiments with dairy cows can predict the isotopic composition of metabolic products (milk, milk components and feces) under natural fluctuations of dietary isotope and chemical composition. First, a diet-switch from a C3-grass/maize diet to a pure C3-grass diet was used to quantify carbon turnover in whole milk, lactose, casein, milk fat and feces. Data were analyzed with a compartmental mixed effects model, which allowed for multiple pools and intra-population variability, and included a delay between feed ingestion and first tracer appearance in outputs. The delay for milk components and whole milk was ∼12 h, and that of feces ∼20 h. The half-life (t½) for carbon in the feces was 9 h, while lactose, casein and milk fat had a t½ of 10, 18 and 19 h. The 13C kinetics of whole milk revealed two pools, a fast pool with a t½ of 10 h (likely representing lactose), and a slower pool with a t½ of 21 h (likely including casein and milk fat). The diet-switch based turnover information provided a precise prediction (RMSE ∼0.2 ‰) of the natural 13C fluctuations in outputs during a 30 days-long period when cows ingested a pure C3 grass with naturally fluctuating isotope composition. PMID:24392000

  18. 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.

  19. Robust Feedback Linearization Applied to a Separation Column for {sup 13}C

    SciTech Connect

    Dulf, Eva-Henrietta; Pop, Cristina-Ioana; Festila, Clement; Dulf, Francisc

    2009-03-05

    In the present developing plan to apply the cryogenic technology for the production of the {sup 13}C, an efficient and safe operation is a strong reason to conceive and to apply a modern computer based control strategy. The authors are concerned with the problem of developing effective and readily implemental techniques for modelling and control of the isotope separation plant. These columns are characterized by complex nonlinearities, with large time-delays. Furthermore, are subject to external disturbances, which are difficult to model. The present paper presents two models of the plant: a nonlinear model and a linear system obtained by robust feedback linearization.

  20. 13C NMR spectral characterization of epimeric rotenone and some related tetrahydrobenzopyranofurobenzopyranones

    USGS Publications Warehouse

    Abidi, S.L.; Abidi, M.S.

    1983-01-01

    The 13C nuclear magnetic resonance (nmr) spectra of epimers of rotenone and four 12a-hydroxy-analogues were examined to determine the stereochemical effect of the B/C ring fusion involving the 6a- and 12a-carbon centers. Chemical shift differences between the epimeric carbon resonances of cis- and trans-6a,12a-compounds were notably larger than those of diastereoisomers derived from the same B/C ring junction stereochemistry. Results of the spectral analysis have been useful for the quantification of mixtures of epimers and for the measurement of rates of epimerization and oxygenation.

  1. 13C SPE MAS measurement of ligand concentration in compressible chromatographic beads

    PubMed Central

    Elwinger, Fredrik; Dvinskikh, Sergey V.

    2015-01-01

    A method for measuring the ligand concentration in heterogeneous materials like chromatography media is described. In this method, 13C single pulse excitation magic angle spinning NMR experiment with broadband 1H decoupling is used to determine the peak integrals for a butyl ligand in the spectrum of a dried chromatography medium. Within a carefully controlled protocol, those integrals compared with that of the internal reference compound dimethyl sulfone provide the required volume concentration with an accuracy of ca 2%. The effects of temperature, degree of hydration, and other experimental parameters are discussed. Copyright © 2015 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd. PMID:26053054

  2. 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.

  3. 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.

  4. Fluxomers: a new approach for 13C metabolic flux analysis

    PubMed Central

    2011-01-01

    Background The ability to perform quantitative studies using isotope tracers and metabolic flux analysis (MFA) is critical for detecting pathway bottlenecks and elucidating network regulation in biological systems, especially those that have been engineered to alter their native metabolic capacities. Mathematically, MFA models are traditionally formulated using separate state variables for reaction fluxes and isotopomer abundances. Analysis of isotope labeling experiments using this set of variables results in a non-convex optimization problem that suffers from both implementation complexity and convergence problems. Results This article addresses the mathematical and computational formulation of 13C MFA models using a new set of variables referred to as fluxomers. These composite variables combine both fluxes and isotopomer abundances, which results in a simply-posed formulation and an improved error model that is insensitive to isotopomer measurement normalization. A powerful fluxomer iterative algorithm (FIA) is developed and applied to solve the MFA optimization problem. For moderate-sized networks, the algorithm is shown to outperform the commonly used 13CFLUX cumomer-based algorithm and the more recently introduced OpenFLUX software that relies upon an elementary metabolite unit (EMU) network decomposition, both in terms of convergence time and output variability. Conclusions Substantial improvements in convergence time and statistical quality of results can be achieved by applying fluxomer variables and the FIA algorithm to compute best-fit solutions to MFA models. We expect that the fluxomer formulation will provide a more suitable basis for future algorithms that analyze very large scale networks and design optimal isotope labeling experiments. PMID:21846358

  5. [Eco-environmental evolution inferred from n-alkanes and delta13C records in the sediments of Shijiu Lake].

    PubMed

    Ou, Jie; Wang, Yan-Hua; Yang, Hao; Hu, Jian-Fang; Chen, Xia; Zou, Jun; Xie, Yun

    2013-02-01

    The study of global changes has focused on the reconstruction of paleovegetation and paleoclimate by n-alkanes and delta13C. 210Pb contents were measured for dating. The distribution characteristics of n-alkanes and delta13C were used to indicate the source of the organic matter in the sediments of Shijiu Lake. The relationship between modern eco-environmental evolution and human behaviors was discussed in this paper. The combination characteristics of n-alkanes showed a significant odd-even predominance in high-carbon number and main peak at C29, suggesting that the organic matter in the sediments were mainly derived from macrophytes and terrestrial higher plants. The delta13C contents of C27, C29 and C31 n-alkanes were analyzed. Results indicated that C3 plants are the dominant species. The distribution characteristics of n-alkanes and delta13C in different periods revealed the impact of human behaviors on Shijiu Lake. From 1862 to 1970, the low relative content of TOC, TN, C17-C25 and the light delta13C25-31 values showed that there were less human behaviors effects on Shijiu Lake and the eco-environment around the lake was stable. From 1970 to 1983, the relative content of TOC, TN and C17-C25 increased significantly, the delta13C25-31 values became weight. In this period, large areas of Shijiu Lake turned into farmland; pollution by fertilizers and pesticides was serious; large amounts of industrial and domestic wastewater were discharged into the lake. All these human behaviors resulted in the degradation of terrestrial higher plants around the lake. Meanwhile, the eutrophication levels were significantly increased. From 1983 to 2010, the relative contents of TOC, TN and C17-C25 were still in high-value ranges, the problem of eutrophication was not effectively controlled and the eco-environment of Shijiu Lake was relatively degradated. PMID:23668113

  6. Natural abundance and 13C-enriched characterisation of atmospheric methane uptake in a forest soil

    NASA Astrophysics Data System (ADS)

    Maxfield, Peter; Hornibrook, Edward; Evershed, Richard

    2013-04-01

    Whilst much attention is focused on CH4 emission inventories, CH4 sinks are sometimes overlooked and not accurately accounted for in national budgets. Two primary reasons for this disjunction include uncertainties about the magnitude and mechanism of terrestrial CH4 oxidation, and an under-appreciation of the quantity of CH4 that is removed from the atmosphere by microorganisms. These uncertainties in part are caused by a lack of high-resolution field data that quantify microbial soil CH4 sink. To fully characterize the soil CH4 sink, isotopic fractionation of CH4during uptake and the fate of CH4 carbon following oxidation by soil microorganisms should be quantified in addition to CH4 fluxes. Here we report on field tests studying CH4 uptake in soil using a Picarro G2201-i cavity ringdown spectrometer (CRDS). Short term atmospheric CH4 uptake was continuously measured in a forest soil in Leigh Woods, UK where the soil methanotrophic community and soil CH4 uptake kinetic isotopic effect (KIE) had been previously quantified using stable isotope probing and conventional stable isotope analysis techniques (Maxfield et al., 2008). Two methodological approaches were tested: (i) direct measurement of the soil CH4 uptake KIE at subambient CH4 concentrations, and (ii) methanotrophic carbon conversion efficiency (CCE) where CCE was evaluated through monitoring the direct conversion of 13C-labelled CH4 to 13C-labelled CO2. The suitability of the G2201-i analyzer as a continuous isotopic CH4 and CO2 analyzer for use at both subambient CH4 concentrations and high 13C-enrichments will be discussed. Maxfield, P.J., Evershed, R.P. and Hornibrook, E.R.C. (2008) Physical and biological controls on the in situ kinetic isotope effect associated with oxidation of atmospheric CH4 in mineral soils. Environmental Science & Technology, 42, 7824-7830.

  7. Large 13C enrichment in primary carbonates from Andean Altiplano lakes, northwest Argentina

    NASA Astrophysics Data System (ADS)

    Valero-Garcés, Blas L.; Delgado-Huertas, Antonio; Ratto, Norma; Navas, Ana

    1999-08-01

    We report here extreme 13C enrichments up to +13‰ PDB in primary calcite and aragonite precipitates in saline, well oxygenated waters from high-altitude lakes in the southern Andean Altiplano, northwestern Argentina. Biological effects, as well as variations in carbon source inputs, and in the exchange rate with atmospheric CO 2, are commonly considered the main controls on the carbon isotope values of authigenic lacustrine carbonate. We present sedimentological and geochemical evidence that favors physical processes — evaporation effects and CO 2-degassing — as major controls on 13C enrichment. We propose that large enrichments may result from the non-equilibrium gas-transfer isotope fractionation during CO 2-degassing from thermal springs and evaporation effects in arid environments. The dilution effect by large quantities of 14C-free CO 2 hinders accurate 14C chronology of these lake records based on lacustrine organic matter and aquatic plants. Our results indicate that geothermal and volcanic CO 2 sources in lake basins located in volcanic settings, and physical fractionation may have a greater significance than commonly accepted to explain lacustrine carbon isotope records.

  8. 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

  9. 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

  10. Direct analysis of δ13C and concentration of dissolved organic carbon (DOC) in environmental samples by TOC-IRMS

    NASA Astrophysics Data System (ADS)

    Kirkels, Frédérique; Cerli, Chiara; Federherr, Eugen; Kalbitz, Karsten

    2014-05-01

    Dissolved organic carbon (DOC) plays an important role in carbon cycling in terrestrial and aquatic systems. Stable isotope analysis (delta 13C) of DOC could provide valuable insights in its origin, fluxes and environmental fate. Precise and routine analysis of delta 13C and DOC concentration are therefore highly desirable. A promising, new system has been developed for this purpose, linking a high-temperature combustion TOC analyzer trough an interface with a continuous flow isotope ratio mass spectrometer (Elementar group, Hanau, Germany). This TOC-IRMS system enables simultaneous stable isotope (bulk delta 13C) and concentration analysis of DOC, with high oxidation efficiency by high-temperature combustion for complex mixtures as natural DOC. To give delta 13C analysis by TOC-IRMS the necessary impulse for broad-scale application, we present a detailed evaluation of its analytical performance for realistic and challenging conditions inclusive low DOC concentrations and environmental samples. High precision (standard deviation, SD predominantly < 0.15 permil) and accuracy (R2 = 0.9997, i.e. comparison TOC-IRMS and conventional EA-IRMS) were achieved by TOC-IRMS for a broad diversity of DOC solutions. This precision is comparable or even slightly better than that typically reported for EA-IRMS systems, and improves previous techniques for δ13C analysis of DOC. Simultaneously, very good precision was obtained for DOC concentration measurements. Assessment of natural abundance and slightly 13C enriched DOC, a wide range of concentrations (0.2-150 mgC/L) and injection volumes (0.05-3 ml), demonstrated good analytical performance with negligible memory effects, no concentration/volume effects and a wide linearity. Low DOC concentrations (< 2 mgC/L), were correctly analyzed without any pre-concentration. Moreover, TOC-IRMS was successfully applied to analyze DOC from diverse terrestrial, freshwater and marine environments (SD < 0.23 permil). In summary, the TOC

  11. s-Processing in AGB Stars Revisited. II. Enhanced 13C Production through MHD-induced Mixing

    NASA Astrophysics Data System (ADS)

    Trippella, O.; Busso, M.; Palmerini, S.; Maiorca, E.; Nucci, M. C.

    2016-02-01

    Slow neutron captures are responsible for the production of about 50% of elements heavier than iron, mainly occurring during the asymptotic giant branch phase of low-mass stars (1 ≲ M/M⊙ ≲ 3), where the main neutron source is the 13C(α, n)16O reaction. This last reaction is activated from locally produced 13C, formed by partial mixing of hydrogen into the He-rich layers. We present here the first attempt to describe a physical mechanism for the formation of the 13C reservoir, studying the mass circulation induced by magnetic buoyancy without adding new free parameters to those already involved in stellar modeling. Our approach represents the application to the stellar layers relevant for s-processing of recent exact analytical 2D and 3D models for magneto-hydrodynamic processes at the base of convective envelopes in evolved stars in order to promote downflows of envelope material for mass conservation during the occurrence of a dredge-up phenomenon. We find that the proton penetration is characterized by small concentrations, but is extended over a large fractional mass of the He-layers, thus producing 13C reservoirs of several 10-3 M⊙. The ensuing 13C-enriched zone has an almost flat profile, while only a limited production of 14N occurs. In order to verify the effects of our new findings we show how the abundances of the main s-component nuclei can be accounted for in solar proportions and how our large 13C-reservoir allows us to solve a few so far unexplained features in the abundance distribution of post-AGB objects.

  12. Spectral density mapping at multiple magnetic fields suitable for 13C NMR relaxation studies

    NASA Astrophysics Data System (ADS)

    Kadeřávek, Pavel; Zapletal, Vojtěch; Fiala, Radovan; Srb, Pavel; Padrta, Petr; Přecechtělová, Jana Pavlíková; Šoltésová, Mária; Kowalewski, Jozef; Widmalm, Göran; Chmelík, Josef; Sklenář, Vladimír; Žídek, Lukáš

    2016-05-01

    Standard spectral density mapping protocols, well suited for the analysis of 15N relaxation rates, introduce significant systematic errors when applied to 13C relaxation data, especially if the dynamics is dominated by motions with short correlation times (small molecules, dynamic residues of macromolecules). A possibility to improve the accuracy by employing cross-correlated relaxation rates and on measurements taken at several magnetic fields has been examined. A suite of protocols for analyzing such data has been developed and their performance tested. Applicability of the proposed protocols is documented in two case studies, spectral density mapping of a uniformly labeled RNA hairpin and of a selectively labeled disaccharide exhibiting highly anisotropic tumbling. Combination of auto- and cross-correlated relaxation data acquired at three magnetic fields was applied in the former case in order to separate effects of fast motions and conformational or chemical exchange. An approach using auto-correlated relaxation rates acquired at five magnetic fields, applicable to anisotropically moving molecules, was used in the latter case. The results were compared with a more advanced analysis of data obtained by interpolation of auto-correlated relaxation rates measured at seven magnetic fields, and with the spectral density mapping of cross-correlated relaxation rates. The results showed that sufficiently accurate values of auto- and cross-correlated spectral density functions at zero and 13C frequencies can be obtained from data acquired at three magnetic fields for uniformly 13C -labeled molecules with a moderate anisotropy of the rotational diffusion tensor. Analysis of auto-correlated relaxation rates at five magnetic fields represents an alternative for molecules undergoing highly anisotropic motions.

  13. The Influence of Plant Litter on Soil Water Repellency: Insight from 13C NMR Spectroscopy.

    PubMed

    Cesarano, Gaspare; Incerti, Guido; Bonanomi, Giuliano

    2016-01-01

    Soil water repellency (SWR, i.e. reduced affinity for water owing to the presence of organic hydrophobic coatings on soil particles) has relevant hydrological implications because low rates of infiltration enhance water runoff, and untargeted diffusion of fertilizers and pesticides. Previous studies investigated the occurrence of SWR in ecosystems with different vegetation cover but did not clarify its relationships with litter biochemical quality. Here, we investigated the capability of different plant litter types to induce SWR by using fresh and decomposed leaf materials from 12 species, to amend a model sandy soil over a year-long microcosm experiment. Water repellency, measured by the Molarity of an Ethanol Droplet (MED) test, was tested for the effects of litter species and age, and compared with litter quality assessed by 13C-CPMAS NMR in solid state and elemental chemical parameters. All litter types were highly water repellent, with MED values of 18% or higher. In contrast, when litter was incorporated into the soil, only undecomposed materials induced SWR, but with a large variability of onset and peak dynamics among litter types. Surprisingly, SWR induced by litter addition was unrelated to the aliphatic fraction of litter. In contrast, lignin-poor but labile C-rich litter, as defined by O-alkyl C and N-alkyl and methoxyl C of 13C-CPMAS NMR spectral regions, respectively, induced a stronger SWR. This study suggests that biochemical quality of plant litter is a major controlling factor of SWR and, by defining litter quality with 13C-CPMAS NMR, our results provide a significant novel contribution towards a full understanding of the relationships between plant litter biochemistry and SWR. PMID:27022916

  14. Simple 13C-urea breath test with infra-red spectrophotometer.

    PubMed

    Taniguchi, Y; Kimura, K; Sohara, H; Shirasaki, A; Kawada, H; Satoh, K; Kihira, K; Wang, X M; Takimoto, T; Goto, Y; Takatori, K; Iida, K; Kajiwara, M

    1996-11-01

    When mass spectrophotometric analysis is used for the 13C-urea breath test to assess H. pylori infection, it is costly, complicated, and time-consuming. To overcome these disadvantages, we utilized an infra-red spectrophotometer as a substitute for the mass spectrophotometer. A total of 153 patients (181 tests) analyzed with peptic ulcers or non-ulcer dyspepsia were investigated. Breath samples were collected 15 min after ingestion of 13C-urea (100 mg in 30 ml water). An infra-red spectrophotometer was used to determine the concentration of 13CO2 in the expirate. The 13CO2/12CO2 ratio was also measured by mass spectrophotometry to compare results with those of infra-red spectrophotometric analysis. Direct detection of H. pylori was qualified in biopsy specimens. Of the 181 biopsies, 138 were positive for H. pylori infection and 43 were negative. With the urea breath test, the mean value in the positive group was significantly higher than that in the negative group (0.062 +/- 0.044 vs 0.011 +/- 0.014, respectively). The cut-off level, 0.01, was determined as delta 13C atom %. The sensitivity of infra-red spectrophotometry was 97.8% (135/138) and specificity was 74.4% (32/43). There was an extremely high coefficient of correlation (r = 0.996) between mass and infra-red photometric analysis. Infra-red spectrometry appears to have great potential not only for diagnosing H. pylori infection but also for assessing treatment results. Its advantages include technical simplicity, cost-effectiveness, and high accuracy. PMID:8959516

  15. The Influence of Plant Litter on Soil Water Repellency: Insight from 13C NMR Spectroscopy

    PubMed Central

    Cesarano, Gaspare; Incerti, Guido; Bonanomi, Giuliano

    2016-01-01

    Soil water repellency (SWR, i.e. reduced affinity for water owing to the presence of organic hydrophobic coatings on soil particles) has relevant hydrological implications because low rates of infiltration enhance water runoff, and untargeted diffusion of fertilizers and pesticides. Previous studies investigated the occurrence of SWR in ecosystems with different vegetation cover but did not clarify its relationships with litter biochemical quality. Here, we investigated the capability of different plant litter types to induce SWR by using fresh and decomposed leaf materials from 12 species, to amend a model sandy soil over a year-long microcosm experiment. Water repellency, measured by the Molarity of an Ethanol Droplet (MED) test, was tested for the effects of litter species and age, and compared with litter quality assessed by 13C-CPMAS NMR in solid state and elemental chemical parameters. All litter types were highly water repellent, with MED values of 18% or higher. In contrast, when litter was incorporated into the soil, only undecomposed materials induced SWR, but with a large variability of onset and peak dynamics among litter types. Surprisingly, SWR induced by litter addition was unrelated to the aliphatic fraction of litter. In contrast, lignin-poor but labile C-rich litter, as defined by O-alkyl C and N-alkyl and methoxyl C of 13C-CPMAS NMR spectral regions, respectively, induced a stronger SWR. This study suggests that biochemical quality of plant litter is a major controlling factor of SWR and, by defining litter quality with 13C-CPMAS NMR, our results provide a significant novel contribution towards a full understanding of the relationships between plant litter biochemistry and SWR. PMID:27022916

  16. Spectral density mapping at multiple magnetic fields suitable for (13)C NMR relaxation studies.

    PubMed

    Kadeřávek, Pavel; Zapletal, Vojtěch; Fiala, Radovan; Srb, Pavel; Padrta, Petr; Přecechtělová, Jana Pavlíková; Šoltésová, Mária; Kowalewski, Jozef; Widmalm, Göran; Chmelík, Josef; Sklenář, Vladimír; Žídek, Lukáš

    2016-05-01

    Standard spectral density mapping protocols, well suited for the analysis of (15)N relaxation rates, introduce significant systematic errors when applied to (13)C relaxation data, especially if the dynamics is dominated by motions with short correlation times (small molecules, dynamic residues of macromolecules). A possibility to improve the accuracy by employing cross-correlated relaxation rates and on measurements taken at several magnetic fields has been examined. A suite of protocols for analyzing such data has been developed and their performance tested. Applicability of the proposed protocols is documented in two case studies, spectral density mapping of a uniformly labeled RNA hairpin and of a selectively labeled disaccharide exhibiting highly anisotropic tumbling. Combination of auto- and cross-correlated relaxation data acquired at three magnetic fields was applied in the former case in order to separate effects of fast motions and conformational or chemical exchange. An approach using auto-correlated relaxation rates acquired at five magnetic fields, applicable to anisotropically moving molecules, was used in the latter case. The results were compared with a more advanced analysis of data obtained by interpolation of auto-correlated relaxation rates measured at seven magnetic fields, and with the spectral density mapping of cross-correlated relaxation rates. The results showed that sufficiently accurate values of auto- and cross-correlated spectral density functions at zero and (13)C frequencies can be obtained from data acquired at three magnetic fields for uniformly (13)C-labeled molecules with a moderate anisotropy of the rotational diffusion tensor. Analysis of auto-correlated relaxation rates at five magnetic fields represents an alternative for molecules undergoing highly anisotropic motions. PMID:27003380

  17. 13C measurements on organic aerosol - ambient samples versus source studies

    NASA Astrophysics Data System (ADS)

    Dusek, Ulrike; Meusinger, Carl; Oyama, Beatriz; Ramon, Wichert; de Wilde, Peter A.; Holzinger, Rupert; Röckmann, Thomas

    2013-04-01

    The stable carbon isotopes 12C and 13C can be used to get information about sources and processing of organic aerosol (OA). We developed and tested a method to measure δ13C values of OA collected on filter samples in different volatility classes. These filter samples are introduced into an oven, where organic compounds are thermally desorbed in He at different temperatures. The compounds released at each temperature step are oxidized to CO2 using a platinum catalyst at 550 °C. The CO2 is then passed on to an isotope ratio mass spectrometer (IRMS) to measure δ13C ratios. With a similar setup the chemical composition at each temperature step can be determined using a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS). System evaluation with controlled test compounds showed that organic compounds usually start evaporating from the filter when their melting point is reached. Isotopic fractionation occurs only, if one temperature step is within a few degrees of the melting point of the substance, so that the substance only partially evaporates. However, this effect should be limited in an ambient sample containing thousands of individual chemical compounds. We analysed aerosol samples collected in a tunnel in Brazil (vehicular emissions), laboratory generated secondary organic aerosol (SOA) from alpha-pinene ozonolysis, and ambient filter samples from a regional site in the Netherlands and an urban site in Belgium. First results indicate that SOA is more volatile than organic aerosol from ambient or tunnel filters. The δ13C ratios of SOA and vehicular emissions do not change strongly with oven temperature, i.e. the more refractory organic compounds have similar isotopic composition as the more volatile compounds. This is in contrast to ambient organic aerosol where the more volatile compounds evaporating below 200°C are depleted with respect to the refractory compounds. Possible reasons for this difference (mixture of sources vs the role of

  18. High-precision position-specific isotope analysis of 13C/12C in leucine and methionine analogues.

    PubMed

    Sacks, Gavin L; Brenna, J Thomas

    2003-10-15

    We report an automated method for high-precision position-specific isotope analysis (PSIA) of carbon in amino acid analogues. Carbon isotope ratios are measured for gas-phase pyrolysis fragments from multiple sources of 3-methylthiopropylamine (3MTP) and isoamylamine (IAA), the decarboxylated analogues of methionine and leucine, using a home-built gas chromatography (GC)-pyrolysis-GC preparation system coupled to a combustion-isotope ratio mass spectrometry system. Over a temperature range of 620-900 degrees C, the characteristic pyrolysis products for 3MTP were CH4, C2H6, HCN, and CH3CN and for IAA products were propylene, isobutylene, HCN, and CH3CN. Fragment origin was confirmed by 13C-labeling, and fragments used for isotope analysis were generated from unique moieties with > 95% structural fidelity. Isotope ratios for the fragments were determined with an average precision of SD(delta13C) < 0.3% per thousand, and relative isotope ratios of fragments from different sources were determined with an average precision of SD(delta(delta)13C) < 0.5% per thousand. Delta(delta)13C values of fragments were invariant over a range of pyrolysis temperatures. The delta(delta)13C of complementary fragments in IAA was within 0.8% per thousand of the delta(delta)13C of the parent compounds, indicating that pyrolysis-induced isotopic fractionation is effectively taken into account with this calibration procedure. Using delta(delta)13C values of fragments, delta(delta)13C values were determined for all four carbon positions of 3MTP and for C1, C2, and the propyl moiety of IAA, either directly or indirectly by mass balance. Large variations in position-specific isotope ratios were observed in samples from different commercial sources. Most dramatically, two 3MTP sources differed by 16.30% per thousand at C1, 48.33% per thousand at C2, 0.37% per thousand at C3, and 5.36% per thousand at C(methyl). These PSIA techniques are suitable for studying subtle changes in intramolecular

  19. Validating methods for measuring delta18O and delta13C in otoliths from freshwater fish.

    PubMed

    Guiguer, K R R A; Drimmie, R; Power, M

    2003-01-01

    The ability of the phosphoric acid digestion technique to extract carbon dioxide from biogenic carbonates and reliably reproduce delta(18)O and delta(13)C signatures from standard reference materials (NBS-18, NBS-19) was tested and shown to produce accurate, unbiased measurements of non-biologic materials. The effects of roasting preparation methods commonly reported when analyzing biogenic carbonates were also tested in a series of experiments using reference standards and otoliths obtained from aquacultured Arctic charr and rainbow trout. Roasting had no effect on the isotope measurement of reference standards. No significant differences between mean oxygen isotope signatures from paired experiments with roasted and non-roasted fish otoliths were found. However, otolith oxygen isotope measurements were significantly enriched in comparison to rearing water-based measurements for both species. Agreement between expected isotopic equilibrium and measured otolith delta(18)O values varied as a function of roasting temperature and between species. Criteria for the selection of appropriate roasting temperatures are suggested and favour 350 degrees C in freshwater fish where unbiased estimates of average rearing water temperatures and known differences in rearing temperatures were obtained. Carbon isotopic disequilibria were observed for both species. A mixing model analysis established differences in the percentage of metabolically derived carbon in studied otoliths, with Arctic charr deriving a greater proportion of otolith delta(13)C from metabolism as a result of higher metabolic rates. PMID:12590395

  20. Analysis of hyperpolarized dynamic 13C lactate imaging in a transgenic mouse model of prostate cancer☆

    PubMed Central

    Lupo, Janine M.; Chen, Albert P.; Zierhut, Matthew L.; Bok, Robert A.; Cunningham, Charles H.; Kurhanewicz, John; Vigneron, Daniel B.; Nelson, Sarah J.

    2011-01-01

    This study investigated the application of an acquisition that selectively excites the [1-13C]lactate resonance and allows dynamic tracking of the conversion of 13C-lactate from hyperpolarized 13C-pyruvate at a high spatial resolution. In order to characterize metabolic processes occurring in a mouse model of prostate cancer, 20 sequential 3D images of 13C-lactate were acquired 5 s apart using a pulse sequence that incorporated a spectral–spatial excitation pulse and a flyback echo-planar readout to track the time course of newly converted 13C-lactate after injection of prepolarized 13C-pyruvate. The maximum lactate signal (MLS), full-width half-maximum (FWHM), time to the peak 13C-lactate signal (TTP) and area under the dynamic curve were calculated from the dynamic images of 10 TRAMP mice and two wild-type controls. The regional variation in 13C-lactate associated with the injected pyruvate was demonstrated by the peak of the 13C-lactate signal occurring earlier in the kidney than in the tumor region. The intensity of the dynamic 13C-lactate curves also varied spatially within the tumor, illustrating the heterogeneity in metabolism that was most prominent in more advanced stages of disease development. The MLS was significantly higher in TRAMP mice that had advanced disease. PMID:19695815

  1. 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

  2. Conformational changes of alamethicin induced by solvent and temperature. A 13C-NMR and circular-dichroism study.

    PubMed

    Jung, G; Dubischar, N

    1975-06-01

    13C nuclear magnetic resonance (NMR) and circular dichroism (CD) have been used for studies on the conformation of alamethicin. The 13C NMR spectrum is assigned with the aid of signals of synthetic partial sequences and selective proton decoupling. The solvent and temperature-dependence of the 13C NMR spectra, T1 measurements and the use of lanthanide-shift reagents allow the differentiation between the amino acids belonging to a rigid alpha-helical portion of the alamethicin sequence and those belonging to a more flexible part. The 13C NMR results are in agreement with results obtained from extended solvent and temperature-dependent CD studies which indicate a highly stabilized nonpolar and intrachenar alpha-helical part. The concentration-dependence of the CD spectrum of alamethicin in a nematic phase revealed aggregation phenomena which might simulate those observed in natural and synthetic membranes. After dissolving alamethicin in aqueous alcohol there is a time-dependence of the ellipticity of the Cotton effects showing a sort of memory effect on the mode of dissolution. Four different conformations can be characterized by CD spectra depending on the solvent and concentration. A model illustrating the dynamic conformations and aggregation phenomena within a membrane is proposed. PMID:1175592

  3. 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.

  4. HepatoDyn: A Dynamic Model of Hepatocyte Metabolism That Integrates 13C Isotopomer Data

    PubMed Central

    Foguet, Carles; Selivanov, Vitaly A.; Fanchon, Eric; Guinovart, Joan J.; de Atauri, Pedro; Cascante, Marta

    2016-01-01

    The liver performs many essential metabolic functions, which can be studied using computational models of hepatocytes. Here we present HepatoDyn, a highly detailed dynamic model of hepatocyte metabolism. HepatoDyn includes a large metabolic network, highly detailed kinetic laws, and is capable of dynamically simulating the redox and energy metabolism of hepatocytes. Furthermore, the model was coupled to the module for isotopic label propagation of the software package IsoDyn, allowing HepatoDyn to integrate data derived from 13C based experiments. As an example of dynamical simulations applied to hepatocytes, we studied the effects of high fructose concentrations on hepatocyte metabolism by integrating data from experiments in which rat hepatocytes were incubated with 20 mM glucose supplemented with either 3 mM or 20 mM fructose. These experiments showed that glycogen accumulation was significantly lower in hepatocytes incubated with medium supplemented with 20 mM fructose than in hepatocytes incubated with medium supplemented with 3 mM fructose. Through the integration of extracellular fluxes and 13C enrichment measurements, HepatoDyn predicted that this phenomenon can be attributed to a depletion of cytosolic ATP and phosphate induced by high fructose concentrations in the medium. PMID:27124774

  5. Impact of Gd3+ doping and glassing solvent deuteration on 13C DNP at 5 Tesla

    NASA Astrophysics Data System (ADS)

    Kiswandhi, Andhika; Lama, Bimala; Niedbalski, Peter; Goderya, Mudrekh; Long, Joanna; Lumata, Lloyd

    Dynamic nuclear polarization (DNP) is a technique which can be used to amplify signals in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) by several thousand-fold. The most commonly available DNP system typically operates at the W-band field or 3.35 T, at which it has been shown that 13C NMR signal can be enhanced by deuteration and Gd3+ doping. In this work, we have investigated the applicability of these procedures at 5 T. Our results indicate that the deuteration of the glassing matrix still yields an enhancement of 13C DNP when 4-oxo-TEMPO free radical is used. The effect is attributed to the lower heat load of the deuterons compared to protons. An addition of a trace amount of Gd3+ gives a modest enhancement of the signal when trityl OX063 is used, albeit with a less pronounced relative enhancement compared to the results obtained at 3.35 T. The results suggest that the enhancement obtained via Gd3+ doping may become saturated at higher field. These results will be discussed using a thermodynamic model of DNP. This work is supported by US Dept of Defense Award No. W81XWH-14-1-0048 and Robert A. Welch Foundation Grant No. AT-1877.

  6. δ18O and δ13C values of modern brachiopod shells

    NASA Astrophysics Data System (ADS)

    Carpenter, Scott J.; Lohmann, Kyger C.

    1995-09-01

    Researchers have not rigorously tested the hypothesis that calcite from modern brachiopod shells is precipitated in oxygen isotope equilibrium with ambient seawater. Isotopic variability at the intraspecimen and intertaxon levels has not been examined. Without such data for modern brachiopods, similar data from ancient brachiopods cannot be accurately interpreted. In this study, a survey is made of δ18O and δ13C values of Terebratulid, Rhynchonellid, Thecideidine, and Craniacean brachiopods from Antarctica, the Bay of Fundy, Curacao, Japan, New Zealand, Norway, Puget Sound, Palau, Sicily, and South Africa. This suite of samples provides a wide range of taxonomic levels, temperatures, salinities, and depositional environments for evaluating the degree of isotopic equilibrium attained during precipitation of brachiopod calcite. New data indicate that modem brachiopod calcite is not always precipitated in oxygen and carbon isotope equilibrium with ambient seawater. Calcite from the primary layer and specialized shell structures (hinge, brachidium, foramen, interarea, muscle scars) are depleted in both 18O and 13C, a characteristic of biological fractionation or "vital" effects often found in other calcerous, marine organisms. Our findings suggest that these portions of the brachiopod shell should be avoided during sampling of ancient brachiopods. Secondary layer calcite, the material most often analyzed in ancient brachiopods, has higher δ18O and δ13C values which approach and sometimes correspond with predicted equilibrium values. Therefore, secondary layer calcite is the most suitable portion of the brachiopod shell for use as an ancient seawater proxy. Although near equilibrium precipitation in secondary layer calcite is encouraging to those studying the isotopic composition of ancient oceans, these data come with caveats. Large intraspecimen variability in the δ18O values of secondary layer calcite (±1‰ in some samples) limits the use of brachiopods as

  7. Site-specific 13C content by quantitative isotopic 13C nuclear magnetic resonance spectrometry: a pilot inter-laboratory study.

    PubMed

    Chaintreau, Alain; Fieber, Wolfgang; Sommer, Horst; Gilbert, Alexis; Yamada, Keita; Yoshida, Naohiro; Pagelot, Alain; Moskau, Detlef; Moreno, Aitor; Schleucher, Jürgen; Reniero, Fabiano; Holland, Margaret; Guillou, Claude; Silvestre, Virginie; Akoka, Serge; Remaud, Gérald S

    2013-07-25

    Isotopic (13)C NMR spectrometry, which is able to measure intra-molecular (13)C composition, is of emerging demand because of the new information provided by the (13)C site-specific content of a given molecule. A systematic evaluation of instrumental behaviour is of importance to envisage isotopic (13)C NMR as a routine tool. This paper describes the first collaborative study of intra-molecular (13)C composition by NMR. The main goals of the ring test were to establish intra- and inter-variability of the spectrometer response. Eight instruments with different configuration were retained for the exercise on the basis of a qualification test. Reproducibility at the natural abundance of isotopic (13)C NMR was then assessed on vanillin from three different origins associated with specific δ (13)Ci profiles. The standard deviation was, on average, between 0.9 and 1.2‰ for intra-variability. The highest standard deviation for inter-variability was 2.1‰. This is significantly higher than the internal precision but could be considered good in respect of a first ring test on a new analytical method. The standard deviation of δ (13)Ci in vanillin was not homogeneous over the eight carbons, with no trend either for the carbon position or for the configuration of the spectrometer. However, since the repeatability for each instrument was satisfactory, correction factors for each carbon in vanillin could be calculated to harmonize the results. PMID:23845488

  8. Biosynthesis of highly enriched 13C-lycopene for human metabolic studies using repeated batch tomato cell culturing with 13C-glucose

    PubMed Central

    Moran, Nancy E.; Rogers, Randy B.; Lu, Chi-Hua; Conlon, Lauren E.; Lila, Mary Ann; Clinton, Steven K.; Erdman, John W.

    2013-01-01

    While putative disease-preventing lycopene metabolites are found in both tomato (Solanum lycopersicum) products and in their consumers, mammalian lycopene metabolism is poorly understood. Advances in tomato cell culturing techniques offer an economical tool for generation of highly-enriched 13C-lycopene for human bioavailability and metabolism studies. To enhance the 13C-enrichment and yields of labeled lycopene from the hp-1 tomato cell line, cultures were first grown in 13C-glucose media for three serial batches and produced increasing proportions of uniformly labeled lycopene (14.3 +/− 1.2 %, 39.6 +/− 0.5 %, and 48.9 +/− 1.5% with consistent yields (from 5.8 to 9 mg/L). An optimized 9-day-long 13C-loading and 18-day-long labeling strategy developed based on glucose utilization and lycopene yields, yielded 13C-lycopene with 93% 13C isotopic purity, and 55% of isotopomers were uniformly labeled. Furthermore, an optimized acetone and hexane extraction led to a four-fold increase in lycopene recovery from cultures compared to a standard extraction. PMID:23561155

  9. 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.

  10. Effects of a Fusarium toxin-contaminated triticale, either untreated or treated with sodium metabisulphite (Na2S2O5, SBS), on weaned piglets with a special focus on liver function as determined by the 13C-methacetin breath test.

    PubMed

    Dänicke, Sven; Beineke, Andreas; Goyarts, Tanja; Valenta, Hana; Beyer, Marita; Humpf, Hans-Ulrich

    2008-08-01

    The aim of the present experiment was to test the effects of a wet preservation of triticale contaminated mainly with deoxynivalenol (DON) with sodium metabisulphite (Na2S2O5, SBS) on growth performance, liver function, clinical-chemical plasma parameters and organ histopathology of piglets. For this purpose both the uncontaminated control triticale and the DON contaminated triticale were included in the piglet diet either untreated (CON, FUS) or SBS-treated (CON-SBS, FUS-SBS) and fed for 28 d starting from weaning. The dietary concentrations of DON and DON sulfonate (DONS), the DON derivative resulting from the SBS treatment, amounted to 0.156, 0.084, 2.312 and 0.275 mg DON per kg CON, CON-SBS, FUS and FUS-SBS diet, and to <0.05, <0.05, <0.05 and 1.841 mg/kg diet, respectively. Feeding the FUS diet significantly reduced the feed intake compared to the other three groups as indicated by the significant interactions between triticale source and SBS treatment when the whole experimental period of 28 d was considered (p = 0.014) while live weight gain and feed to gain ratio remained unaffected. The total plasma protein concentration was significantly depressed due to feeding the contaminated diets whereas SBS treatment exerted an increasing effect at the same time (45.4, 49.5, 40.7 and 46.5 g/l for piglets fed the CON, CON-SBS, FUS and FUS-SBS diet, respectively). The liver function was tested by the 13C-methacetin breath test (MBT) allowing evaluation of the cytochrome P4501A2 activity. MBT results, expressed as cumulative percentage dose recovery after 360 min (cPDR360) revealed a slight stimulation of liver function due to SBS treatment (p = 0.052) (37.5, 39.4, 37.4 and 55.1% for piglets fed the CON, CON-SBS, FUS and FUS-SBS diet, respectively). Liver weight and histopathological scoring were only weakly related to the MBT results. Further histopathological examinations of kidneys, pancreas and heart revealed no treatment effects. It was concluded that the SBS

  11. 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

  12. 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

  13. Sub-second Proton Imaging of 13C Hyperpolarized Contrast Agents in Water

    PubMed Central

    Truong, Milton L.; Coffey, Aaron M.; Shchepin, Roman V.; Waddell, Kevin W.; Chekmenev, Eduard Y.

    2014-01-01

    Indirect proton detection of 13C hyperpolarized contrast agents potentially enables greater sensitivity. Presented here is a study of sub-second projection imaging of hyperpolarized 13C contrast agent addressing the obstacle posed by water suppression for indirect detection in vivo. Sodium acetate phantoms were used to develop and test water suppression and sub-second imaging with frequency selective RF pulses using spectroscopic and imaging indirect proton detection. A 9.8 mM aqueous solution of 13C PHIP hyperpolarized 2-hydroxyethyl-13C-propionate-d2,3,3 (HEP),

    ~25% was used for demonstration of indirect proton sub-second imaging detection. Balanced 2D FSSFP (Fast Steady State Free Precession) allowed recording proton images with FOV = 64×64 mm2 and spatial resolution 2×2 mm2 with total acquisition time of less than 0.2 s. In thermally polarized sodium 1-13C-acetate, 13C to 1H polarization transfer efficiency of 45.1% of the theoretically predicted values was observed in imaging detection corresponding to an 11 fold of overall sensitivity improvement compared to direct 13C FSSFP imaging. 13C to 1H polarization transfer efficiency of 27% was observed in imaging detection corresponding to a 3.25 fold sensitivity improvement compared to direct 13C FSSFP imaging with hyperpolarized HEP. The range of potential applications and limitations of this sub-second and ultra-sensitive imaging approach are discussed. PMID:24753438

  14. 13C Tracking after 13CO2 Supply Revealed Diurnal Patterns of Wood Formation in Aspen1

    PubMed Central

    Mahboubi, Amir; Linden, Pernilla; Moritz, Thomas

    2015-01-01

    Wood of trees is formed from carbon assimilated in the photosynthetic tissues. Determining the temporal dynamics of carbon assimilation, subsequent transport into developing wood, and incorporation to cell walls would further our understanding of wood formation in particular and tree growth in general. To investigate these questions, we designed a 13CO2 labeling system to study carbon transport and incorporation to developing wood of hybrid aspen (Populus tremula × tremuloides). Tracking of 13C incorporation to wood over a time course using nuclear magnetic resonance spectroscopy revealed diurnal patterns in wood cell wall biosynthesis. The dark period had a differential effect on 13C incorporation to lignin and cell wall carbohydrates. No 13C was incorporated into aromatic amino acids of cell wall proteins in the dark, suggesting that cell wall protein biosynthesis ceased during the night. The results show previously unrecognized temporal patterns in wood cell wall biosynthesis, suggest diurnal cycle as a possible cue in the regulation of carbon incorporation to wood, and establish a unique 13C labeling method for the analysis of wood formation and secondary growth in trees. PMID:25931520

  15. Conditions to obtain precise and true measurements of the intramolecular 13C distribution in organic molecules by isotopic 13C nuclear magnetic resonance spectrometry.

    PubMed

    Bayle, Kevin; Gilbert, Alexis; Julien, Maxime; Yamada, Keita; Silvestre, Virginie; Robins, Richard J; Akoka, Serge; Yoshida, Naohiro; Remaud, Gérald S

    2014-10-10

    Intramolecular (13)C composition gives access to new information on the (bio) synthetic history of a given molecule. Isotopic (13)C NMR spectrometry provides a general tool for measuring the position-specific (13)C content. As an emerging technique, some aspects of its performance are not yet fully delineated. This paper reports on (i) the conditions required to obtain satisfactory trueness and precision for the determination of the internal (13)C distribution, and (ii) an approach to determining the "absolute" position-specific (13)C content. In relation to (i), a precision of <1% can be obtained whatever the molecule on any spectrometer, once quantitative conditions are met, in particular appropriate proton decoupling efficiency. This performance is a prerequisite to the measurement of isotope fractionation either on the transformed or residual compound when a chemical reaction or process is being studied. The study of the trueness has revealed that the response of the spectrometer depends on the (13)C frequency range of the studied molecule, i.e. the chemical shift range. The "absolute value" and, therefore, the trueness of the (13)C NMR measurements has been assessed on acetic acid and by comparison to the results obtained on the fragments from COOH and CH3 by isotopic mass spectrometry coupled to a pyrolysis device (GC-Py-irm-MS), this technique being the reference method for acetic acid. Of the two NMR spectrometers used in this work, one gave values that corresponded to those obtained by GC-Py-irm-MS (thus, the "true" value) while the other showed a bias, which was dependent to the range covered by the resonance frequencies of the molecule. Therefore, the former can be used directly for studying isotope affiliations, while the latter can only be used directly for comparative data, for example in authenticity studies, but can also be used to obtain the true values by applying appropriate correction factors. The present study assesses several key protocol

  16. Soil microbial communities in a CO2-enriched and 13C-labelled treeline ecosystem with different tree species

    NASA Astrophysics Data System (ADS)

    Hiltbrunner, David; Hagedorn, Frank; Miltner, Anja; Schmidt, Michael W. I.

    2010-05-01

    The aim of this study was to estimate the responses of soil microbial communities at the alpine treeline to elevated CO2 and to gain insight into the C cycling through microbial groups under two tree species by tracking 13C signatures into phospholipid fatty acids (PLFA). In alpine treeline ecosystems, we exposed 30 year-old larch and pine trees growing on undisturbed thick mor-type organic layers to five years of elevated CO2 (+200 μmol CO2 mol-1) being depleted in 13C. Results showed that elevated CO2 increased soil respiration particularly under pine trees. However, we found negligible CO2 effects on the biomass and community structure of soil microorganisms, which might be due to small plant growth responses, and a comparatively small input of new plant-derived C into the thick organic layers with large C stocks. The tracing of 13C-depleted CO2 revealed that only a small portion of the microbial community actively metabolized new C (25%). The 13C label in individual PLFA indicated that mainly fungi were involved in the use of new substrate. Tree species affected soil microbial communities in the organic layer with a significantly higher ratio of fungal to bacterial fatty acids under pine than under larch trees. Under pine, fungal PLFA of the organic layer carried a stronger 13C label which strongly suggests a greater mycorrhizal activity that might also lead to the 60% greater input of new plant-derived C into soil organic matter under pine than under larch. In conclusion, our results show that significant responses of microbial communities in these treeline ecosystems if any would require more drastic and long lasting effects than five years of elevated CO2. Tree species have a major impact on the cycling of new plant C through soil microbial communities.

  17. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; Wu, R.; Yao, B.; Zhao, Y.; Lin, G.; Wu, B.; Lu, Q.; Meng, P.

    2015-01-01

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, hypothesized to be the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs, while processes such as fractionating foliar metabolism and preferentially loading into phloem of 13C-enriched sugars may contribute to the overall autotrophic-heterotrophic difference in carbon isotope compositions.

  18. Monitoring creatine and phosphocreatine by (13)C MR spectroscopic imaging during and after (13)C4 creatine loading: a feasibility study.

    PubMed

    Janssen, Barbara H; Lassche, Saskia; Hopman, Maria T; Wevers, Ron A; van Engelen, Baziel G M; Heerschap, Arend

    2016-08-01

    Creatine (Cr) supplementation to enhance muscle performance shows variable responses among individuals and different muscles. Direct monitoring of the supplied Cr in muscles would address these differences. In this feasibility study, we introduce in vivo 3D (13)C MR spectroscopic imaging (MRSI) of the leg with oral ingestion of (13)C4-creatine to observe simultaneously Cr and phosphocreatine (PCr) for assessing Cr uptake, turnover, and the ratio PCr over total Cr (TCr) in individual muscles. (13)C MRSI was performed of five muscles in the posterior thigh in seven subjects (two males and two females of ~20 years, one 82-year-old male, and two neuromuscular patients) with a (1)H/(13)C coil in a 3T MR system before, during and after intake of 15 % (13)C4-enriched Cr. Subjects ingested 20 g Cr/day for 4 days in four 5 g doses at equal time intervals. The PCr/TCr did not vary significantly during supplementation and was similar for all subjects and investigated muscles (average 0.71 ± 0.07), except for the adductor magnus (0.64 ± 0.03). The average Cr turnover rate, assessed in male muscles, was 2.1 ± 0.7 %/day. The linear uptake rates of Cr were variable between muscles, although not significantly different. This assessment was possible in all investigated muscles of young male volunteers, but less so in muscles of the other subjects due to lower signal-to-noise ratio. Improvements for future studies are discussed. In vivo (13)C MRSI after (13)C-Cr ingestion is demonstrated for longitudinal studies of Cr uptake, turnover, and PCr/TCr ratios of individual muscles in one exam. PMID:27401085

  19. Photobioreactor design for isotopic non-stationary 13C-metabolic flux analysis (INST 13C-MFA) under photoautotrophic conditions.

    PubMed

    Martzolff, Arnaud; Cahoreau, Edern; Cogne, Guillaume; Peyriga, Lindsay; Portais, Jean-Charles; Dechandol, Emmanuel; Le Grand, Fabienne; Massou, Stéphane; Gonçalves, Olivier; Pruvost, Jérémy; Legrand, Jack

    2012-12-01

    Adaptive metabolic behavior of photoautotrophic microorganisms toward genetic and environmental perturbations can be interpreted in a quantitative depiction of carbon flow through a biochemical reaction network using isotopic non-stationary (13) C-metabolic flux analysis (INST (13) C-MFA). To evaluate (13) C-metabolic flux maps for Chlamydomonas reinhardtii, an original experimental framework was designed allowing rapid, reliable collection of high-quality isotopomer data against time. It involved (i) a short-time (13) C labeling injection device based on mixing control in a torus-shaped photobioreactor with plug-flow hydrodynamics allowing a sudden step-change in the (13) C proportion in the substrate feed and (ii) a rapid sampling procedure using an automatic fast filtration method coupled to a manual rapid liquid nitrogen quenching step. (13) C-substrate labeling enrichment was controlled through the total dissolved inorganic carbon concentration in the pulsed solution. First results were obtained from steady-state continuous culture measurements allowing the characterization of the kinetics of label incorporation into light-limited growing cells cultivated in a photobioreactor operating at the maximal biomass productivity for an incident photon flux density of 200 µmol m(-2) s(-1). (13)C label incorporation was measured for 21 intracellular metabolites using IC-MS/MS in 58 samples collected across a labeling experiment duration of 7 min. The fastest labeling rate was observed for 2/3-phosphoglycerate with an apparent isotopic stationary state reached after 300 s. The labeling rate was consistent with the optimized mixing time of about 4.9 s inside the reactor and the shortest reliable sampling period assessed at 5 s. PMID:22688667

  20. Metabolism of hyperpolarized [1-(13) C]pyruvate through alternate pathways in rat liver.

    PubMed

    Jin, Eunsook S; Moreno, Karlos X; Wang, Jian-Xiong; Fidelino, Leila; Merritt, Matthew E; Sherry, A Dean; Malloy, Craig R

    2016-04-01

    The source of hyperpolarized (HP) [(13) C]bicarbonate in the liver during metabolism of HP [1-(13) C]pyruvate is uncertain and likely changes with physiology. Multiple processes including decarboxylation through pyruvate dehydrogenase or pyruvate carboxylase followed by subsequent decarboxylation via phosphoenolpyruvate carboxykinase (gluconeogenesis) could play a role. Here we tested which metabolic fate of pyruvate contributed to the appearance of HP [(13) C]bicarbonate during metabolism of HP [1-(13) C]pyruvate by the liver in rats after 21 h of fasting compared to rats with free access to food. The (13) C NMR of HP [(13) C]bicarbonate was observed in the liver of fed rats, but not in fasted rats where pyruvate carboxylation and gluconeogenesis was active. To further explore the relative fluxes through pyruvate carboxylase versus pyruvate dehydrogenase in the liver under typical conditions of hyperpolarization studies, separate parallel experiments were performed with rats given non-hyperpolarized [2,3-(13) C]pyruvate. (13) C NMR analysis of glutamate isolated from the liver of rats revealed that flux from injected pyruvate through pyruvate dehydrogenase was dominant under fed conditions whereas flux through pyruvate carboxylase dominated under fasted conditions. The NMR signal of HP [(13) C]bicarbonate does not parallel pyruvate carboxylase activity followed by subsequent decarboxylation reaction leading to glucose production. In the liver of healthy well-fed rats, the appearance of HP [(13) C]bicarbonate exclusively reflects decarboxylation of HP [1-(13) C]pyruvate via pyruvate dehydrogenase. © 2016 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd. PMID:26836042

  1. Robust hyperpolarized (13)C metabolic imaging with selective non-excitation of pyruvate (SNEP).

    PubMed

    Chen, Way Cherng; Teo, Xing Qi; Lee, Man Ying; Radda, George K; Lee, Philip

    2015-08-01

    In vivo metabolic imaging using hyperpolarized [1-(13)C]pyruvate provides localized biochemical information and is particularly useful in detecting early disease changes, as well as monitoring disease progression and treatment response. However, a major limitation of hyperpolarized magnetization is its unrecoverable decay, due not only to T1 relaxation but also to radio-frequency (RF) excitation. RF excitation schemes used in metabolic imaging must therefore be able to utilize available hyperpolarized magnetization efficiently and robustly for the optimal detection of substrate and metabolite activities. In this work, a novel RF excitation scheme called selective non-excitation of pyruvate (SNEP) is presented. This excitation scheme involves the use of a spectral selective RF pulse to specifically exclude the excitation of [1-(13)C]pyruvate, while uniformly exciting the key metabolites of interest (namely [1-(13)C]lactate and [1-(13)C]alanine) and [1-(13)C]pyruvate-hydrate. By eliminating the loss of hyperpolarized [1-(13)C]pyruvate magnetization due to RF excitation, the signal from downstream metabolite pools is increased together with enhanced dynamic range. Simulation results, together with phantom measurements and in vivo experiments, demonstrated the improvement in signal-to-noise ratio (SNR) and the extension of the lifetime of the [1-(13)C]lactate and [1-(13)C]alanine pools when compared with conventional non-spectral selective (NS) excitation. SNEP has also been shown to perform comparably well with multi-band (MB) excitation, yet SNEP possesses distinct advantages, including ease of implementation, less stringent demands on gradient performance, increased robustness to frequency drifts and B0 inhomogeneity as well as easier quantification involving the use of [1-(13)C]pyruvate-hydrate as a proxy for the actual [1-(13)C] pyruvate signal. SNEP is therefore a promising alternative for robust hyperpolarized [1-(13)C]pyruvate metabolic imaging with high

  2. The Nature of Carbonate and Organic δ13C Covariance Through Geological Time

    NASA Astrophysics Data System (ADS)

    Oehlert, A. M.; Swart, P. K.

    2014-12-01

    Significant evolutionary, climatic, and oceanographic events in Earth history are often accompanied by excursions in the carbon isotope composition (δ13C) of marine carbonates and co-occurring sedimentary organic material. The observation of synchronous excursions in the δ13C values of marine carbonates and coeval organic matter is commonly thought to prove that the deposit has not been altered by diagenesis, and that the variations in the δ13C records are the result of a significant change in global carbon cycling. Furthermore, this model suggests that the covariance of carbonate and organic δ13C records is driven only by changes in the δ13C value of the dissolved inorganic carbon in the surface waters of the ocean. However, recent work suggests that there may be at least two alternate models for generating covariance between carbonate and organic δ13C values in the geologic record. One of the models invokes sea-level driven syndepositional mixing between isotopically distinct sources of carbonate and organic material to produce positive covariance between carbonate and organic δ13C values. The second model suggests that post-depositional alteration to the carbonate δ13C values during meteoric diagenesis, in concert with concurrent contributions of terrestrial organic material during subaerial exposure, can also produce co-occurring negative excursions with tightly covariant δ13C records. In contrast to earlier interpretations of covariant δ13C values, these models suggest that both syndepositional and post-depositional factors can significantly influence the relationship between carbonate and organic δ13C values in a variety of depositional environments. The implications for reconstructions of ancient global carbon cycle events will be explored within the context of these three models, and their relative importance throughout geologic time will be discussed.

  3. Mathematical analysis of isotope labeling in the citric acid cycle with applications to 13C NMR studies in perfused rat hearts.

    PubMed

    Chance, E M; Seeholzer, S H; Kobayashi, K; Williamson, J R

    1983-11-25

    Rat hearts have been perfused in vitro with 5 mM glucose and either 5 mM acetate or 1 mM pyruvate to achieve steady state conditions, followed by replacement of the acetate with 90% enriched [2-13C]acetate or pyruvate with 90% enriched [3-13C]pyruvate. The hearts were frozen different times after addition of 13C-substrate and neutralized perchloric acid extracts from three pooled hearts per time point were used to obtain high resolution proton-decoupled 13C NMR spectra at 90.55 MHz. The 13C fractional enrichment of individual carbons of different metabolites was calculated from the area of the resolved resonances after correction for nuclear Overhauser enhancement and saturation effects. A mathematical flux model of the citric acid cycle and ancillary transamination reactions was constructed with the FACSIMILE program, and used to solve unknown flux parameters with constant pool sizes by nonlinear least squares analysis of the approximately 200 simultaneous differential equations required to describe the reactions. With [2-13C] acetate as substrate, resonances and line splittings due to 13C-13C spin coupling of the C-2, C-3, and C-4 carbons of glutamate were well resolved. The half-times to reach maximum 13C enrichment were 2.6 min for glutamate C-4 and 8 min for glutamate C-2 and C-3. From these data, a well determined citric acid cycle flux of 8.3 mumol/g dry weight X min was calculated for an observed oxygen consumption of 31 mumol/g dry weight X min. With [3-13C]pyruvate as substrate, resonances of aspartate C-2 and C-3 and of alanine C-3 were well resolved in addition to those of glutamate C-2, C-3, and C-4. Nonlinear least squares fitting of these data to the model gave nonrandomly distributed residuals for the 13C fractional enrichments of glutamate C-4, suggesting an incomplete model, but a well determined cycle flux of 11.9 mumol/g dry weight X min for an oxygen uptake of 35 mumol/g dry weight X min. Our studies demonstrate the practicality of 13C NMR

  4. δ13C values of soil organic matter in semiarid grassland with mesquite (Prosopis) encroachment in southeastern Arizona

    USGS Publications Warehouse

    Biggs, Thomas H.; Quade, Jay; Webb, Robert H.

    2002-01-01

    Over the past century, C3 woody plants and trees have increased in abundance in many semiarid ecosystems, displacing native C4 grasses. Livestock grazing, climatic fluctuations, and fire suppression are several reasons proposed for this shift. Soil carbon isotopic signatures are an ideal technique to evaluate carbon turnover rates in such ecosystems. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established on homogeneous granitic alluvium to investigate the effects of fire frequency on δ13C values in surface soil organic matter (SOM). These ranges have had no livestock grazing for 50 years and a well-documented history of fires. Prosopis velutina Woot. (mesquite) trees have altered SOM δ13C pools by the concentration of plant nutrients and the addition of isotopically light litter. These soil carbon changes do not extend beyond canopy margins. Elevated total organic carbon (TOC), plant nutrient (N and P) concentrations, and depleted SOM δ13C values are associated with C3Prosopis on an unburned plot, which enables recognition of former Prosopis-occupied sites on plots with recent fire histories. Elevated nutrient concentrations associated with former Prosopis are retained in SOM for many decades. Surface SOM δ13C values indicate the estimated minimum turnover time of C4-derived carbon beneath large mature Prosopis is about 100–300 years. In contrast, complete turnover of original C3 carbon to C4 carbon under grasslands is estimated to take a minimum of 150–500 years. Our study confirms that C4 grass cover has declined over the past 100 years, although isolated C3 trees or shrubs were not uncommon on the historic C4-dominated grasslands. We find evidence in surface soil layers for a modern C3 plant expansion reflected in the substantial shift of SOM δ13C values from C4 grasses to C3 shrublands.

  5. Root biomass and soil δ13C in C3 and C4 grasslands along a precipitation gradient

    NASA Astrophysics Data System (ADS)

    Pau, S.; Angelo, C. L.

    2014-12-01

    Many studies have investigated the distribution of C3 and C4 grasses along climatic gradients because they illustrate complex interactions between abiotic and biotic controls on ecosystem functions. Yet few studies have examined belowground components of these distributions, which may present very different patterns compared to aboveground measures. In this study, we surveyed grass species cover and collected soil and root samples from field plots at 100 - 150 m elevation intervals along a climatic gradient in Hawai'i. We examined how the relationship between soil carbon isotopic composition (δ13C), a proxy for C4 productivity and dominance, and % C4 cover changed along a climatic gradient. Results showed that δ13C underpredicted C4 dominance in wetter sites. Indeed, the relationship between % C4 cover and soil δ13C became more negative with increasing mean annual precipitation (MAP) based on a linear mixed-effects model (F 1,34 = 12.25, P < 0.01). Soil δ13C in wetter sites indicated a larger C3 contribution than estimated by aboveground cover, which was in part due to C3 root biomass increasing (P < 0.05) whereas C4 root biomass did not change along the precipitation gradient. C3 and C4 grasses appear to allocate disproportionately belowground, thus a different understanding of C4 ecological dominance may emerge when considering both above and belowground components. Our results show that belowground allocation and interpretation of soil δ13C need to be more carefully considered in global vegetation and carbon models and paleoecological reconstructions of C4 dominance.

  6. Losses of soil carbon by converting tropical forest to plantations: erosion and decomposition estimated by δ(13) C.

    PubMed

    Guillaume, Thomas; Damris, Muhammad; Kuzyakov, Yakov

    2015-09-01

    Indonesia lost more tropical forest than all of Brazil in 2012, mainly driven by the rubber, oil palm, and timber industries. Nonetheless, the effects of converting forest to oil palm and rubber plantations on soil organic carbon (SOC) stocks remain unclear. We analyzed SOC losses after lowland rainforest conversion to oil palm, intensive rubber, and extensive rubber plantations in Jambi Province on Sumatra Island. The focus was on two processes: (1) erosion and (2) decomposition of soil organic matter. Carbon contents in the Ah horizon under oil palm and rubber plantations were strongly reduced up to 70% and 62%, respectively. The decrease was lower under extensive rubber plantations (41%). On average, converting forest to plantations led to a loss of 10 Mg C ha(-1) after about 15 years of conversion. The C content in the subsoil was similar under the forest and the plantations. We therefore assumed that a shift to higher δ(13) C values in plantation subsoil corresponds to the losses from the upper soil layer by erosion. Erosion was estimated by comparing the δ(13) C profiles in the soils under forest and under plantations. The estimated erosion was the strongest in oil palm (35 ± 8 cm) and rubber (33 ± 10 cm) plantations. The (13) C enrichment of SOC used as a proxy of its turnover indicates a decrease of SOC decomposition rate in the Ah horizon under oil palm plantations after forest conversion. Nonetheless, based on the lack of C input from litter, we expect further losses of SOC in oil palm plantations, which are a less sustainable land use compared to rubber plantations. We conclude that δ(13) C depth profiles may be a powerful tool to disentangle soil erosion and SOC mineralization after the conversion of natural ecosystems conversion to intensive plantations when soils show gradual increase of δ(13) C values with depth. PMID:25707391

  7. 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

  8. 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

  9. 13C MRS studies of neuroenergetics and neurotransmitter cycling in humans

    PubMed Central

    Rothman, Douglas L.; De Feyter, Henk M.; de Graaf, Robin A.; Mason, Graeme F.; Behar, Kevin L.

    2011-01-01

    In the last 25 years 13C MRS has been established as the only non invasive method for measuring glutamate neurotransmission and cell specific neuroenergetics. Although technically and experimentally challenging 13C MRS has already provided important new information on the relationship between neuroenergetics and neuronal function, energy cost of brain function, the high neuronal activity in the resting brain state, and how neuroenergetics and neurotransmitter cycling are altered in neurological and psychiatric disease. In this paper the current state of 13C MRS as it is applied to study neuroenergetics and neurotransmitter cycling in humans is reviewed. The focus is predominantly on recent findings in humans regarding metabolic pathways, applications to clinical research, and the technical status of the method. Results from in vivo 13C MRS studies in animals are discussed from the standpoint of validation of MRS measurements of neuroenergetics and neurotransmitter cycling and where they have helped identify key questions to address in human research. Controversies concerning the relation of neuroenergetics and neurotransmitter cycling and factors impacting accurate determination of fluxes through mathematical modeling are addressed. We further touch upon different 13C labeled substrates used to study brain metabolism, before reviewing a number of human brain diseases studied using 13C MRS. Future technological developments are discussed that will help to overcome limitations of 13C MRS with special attention on recent developments in hyperpolarized 13C MRS. PMID:21882281

  10. Amorphous Fe72Cr8P13C7 Powder with High Corrosion Resistance

    NASA Astrophysics Data System (ADS)

    Cho, Kangjo; Hwang, Choll-Hong; Pak, Chang-Su; Ryeom, Yeong-Jo

    1982-07-01

    Amorphous Fe72Cr8P13C7 powder has been prepared by the spark erosion technique and its corrosion behavior investigated potentiodynamically. It is concluded that the powder prepared this way possesses a relatively high corrosion resistance, as does amorphous Fe72Cr8P13C7 ribbon prepared by rapid quenching.

  11. 13c-SUCROSE BREATH TEST TO DIFFERENTIATE CONGENITAL SUCRASE-ISOMALTASE DEFICIENCY FROM PANDISACCHARIDASE DEFICIENCY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction: A substrate-paired breath test using 13C-sucrose (S) and 13C-glucose (G) has been developed to assess congenital sucrase-isomaltase deficiency (CSID). The aim was to determine if CSID could be detected without duodenal enzyme assay. Methods: Two patients (1F:1M, aged 1 & 15 yrs) wi...

  12. Latitudinal Variation in δ13C derived from Terrestrial Plants during the Cretaceous

    NASA Astrophysics Data System (ADS)

    Strganac, C.; Jacobs, L. L.; Ferguson, K.; Macphee, R. D.; Fiorillo, A. R.; Hooker, J.; Nishida, Y.; Flemming, C.

    2010-12-01

    Modern plankton and terrestrial plants exhibit a gradient in δ13C with latitude. Although there are several reasons for δ13C variation in plants, modern latitudinal variation is correlated with environmental and climatic factors such as temperature. We present δ13C values derived from mid-Cretaceous terrestrial plant fossils in Texas at paleolatitude ~30 N and Australia at paleolatitude ~70 S that show an offset in δ13C values, suggesting a latitudinal gradient in δ13C in plants during the Cretaceous. This hypothesis was tested by new data from Antarctica at paleolatitude ~60 S and Alaska at paleolatitude ~70 N, and we compared these data to published carbon isotope records. The latitudinal variation in plant δ13C was on the order of 2‰ more negative at high latitudes, suggesting a shallower Cretaceous latitudinal gradient in plant δ13C than at present. The shallow gradient in plant δ13C during the Cretaceous correlates with a latitudinal temperature gradient that is also less than today.

  13. Towards a vibrational analysis of spheroidene. Resonance Raman spectroscopy of 13C-labelled spheroidenes in petroleum ether and in the Rhodobacter sphaeroides reaction centre.

    PubMed

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

    1994-04-28

    We report resonance Raman spectra of the carotenoid spheroidene and its 14'-13C and 15'-13C substituted analogues in petroleum ether and bound to the reaction centre of Rhodobacter sphaeroides R26. The spectra in petroleum ether correspond to planar all-trans spheroidene while those of the reaction centres are consistent with a nonplanar 15,15'-cis spheroidene. The effect of 13C labelling is largest in the carbon-carbon double-bond stretching region. The 15'-13C substitution of the reaction centre bound spheroidene, however, hardly changes the C=C band as compared to that for the natural abundance spheroidene apart from a new weak band at 1508 cm(-1). This observation has been interpreted as a decoupling of the C15=C15' stretch from the other double-bond stretches in combination with a small intrinsic Raman intensity of this local mode for 15,15'-cis spheroidene. PMID:8167135

  14. 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

  15. ^13C Solid NMR Study of Devulcanization and Revulcanization of SBR Ne

    NASA Astrophysics Data System (ADS)

    Massey, J.; Levin, V.; Isayev, A.; von Meerwall, E.

    1996-03-01

    As part of a larger effort in support of recycling of rubber-based composites, we have used ^13C CP-MAS NMR spectroscopy and relaxation to study molecular and segmental mobilities in styrene-butadiene random copolymers before and after sulfur crosslinking, after subsequent devulcanization using a thermal ultrasound technique, and following revulcanization. Tracking the cis-trans ratio indicates that overall network crosslink density increases during each of these steps, including devulcanization, which produces mesoscale network aggregates and substantial amounts of sol. This observation is confirmed by the transverse (T_2) relaxation times, which show that molecular/segmental mobilities monotonically decrease in the same sequence. Analysis of these effects requires the invocation of alterations in sulfur crosslinking, i.e. density, distribution, and functionality, including extensive cyclization. Measurements of the glass transition temperatures in melt, network, sol , and revulcanizate are in accord with this picture.

  16. 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.

  17. 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.

  18. 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.

  19. Parallel δ 13C and Conifer Physiognomic Trends Across the Triassic-Jurassic Boundary

    NASA Astrophysics Data System (ADS)

    Whiteside, J. H.; Olsen, P. E.; Sambrotto, R. N.; Cornet, B.

    2003-12-01

    The Triassic-Jurassic mass extinction event ( ˜200 Ma) had a profound effect on biotic evolution, and herein we describe trends in cheirolepidaceous conifer leaf physiognomy from the Pangean tropics (present northeastern USA) that at least broadly parallel a negative δ 13C excursion recorded in the same strata. The physiognomic changes appear at an abrupt (<10 ky) negative carbon isotope excursion (1) synchronous with a previously described palynological extinction level, fern spike, and Ir anomaly (2), and continue through a prolonged negative excursion, lasting 900 ky (through all three CAMP basaltic extrusive events), encompassing most of the Hettangian age. The physiognomic changes seen in the cheirolepidaceous conifer leafy shoot forms Brachyphyllum and Pagiophyllum through the δ 13C excursions include primarily the development of microphyllous leaves with thickened cuticle and sunken papillate stomata (3). These floral modifications are consistent with intense thermal stress plausibly due to very high atmospheric CO2 concentrations and corroborate McElwain's (4) thermal damage hypothesis for the Triassic-Jurassic transition that was originally based on different plant taxa from the higher Pangean latitudes in present Greenland and Sweden. Subsequently, a 2- to 5-fold increase in the area of leafy shoots in strata of latest Hettangian age suggest a return to lower thermal stress levels perhaps due to lower CO2, despite the fact that eastern North America continued to drift into more arid latitudes. The floral physiognomic changes associated with the negative δ 13C excursion and likely very elevated CO2 levels is in many ways a microcosm of the Mesozoic in which the dominance of cheiroleps apparently overlaps with the highest CO2 levels of the Mesozoic (5). References. (1) Whiteside JH, Olsen PE, Sambrotto RN. 2003. Geol. Soc. Amer. Abst. Prog. (in press). (2) Olsen PE et al., Science 296:1305-1307 (3) Cornet B. 1989. in Olsen PE, Schlische RW, Gore PJW

  20. Cigarette Butt Decomposition and Associated Chemical Changes Assessed by 13C CPMAS NMR

    PubMed Central

    Bonanomi, Giuliano; Incerti, Guido; Cesarano, Gaspare; Gaglione, Salvatore A.; Lanzotti, Virginia

    2015-01-01

    Cigarette butts (CBs) are the most common type of litter on earth, with an estimated 4.5 trillion discarded annually. Apart from being unsightly, CBs pose a serious threat to living organisms and ecosystem health when discarded in the environment because they are toxic to microbes, insects, fish and mammals. In spite of the CB toxic hazard, no studies have addressed the effects of environmental conditions on CB decomposition rate. In this study we investigate the interactive effects of substrate fertility and N transfer dynamics on CB decomposition rate and carbon quality changes. We carried out an experiment using smoked CBs and wood sticks, used as a slow decomposing standard organic substrate, incubated in both laboratory and field conditions for two years. CB carbon quality changes during decomposition was assessed by 13C CPMAS NMR. Our experiment confirmed the low degradation rate of CBs which, on average, lost only 37.8% of their initial mass after two years of decomposition. Although a net N transfer occurred from soil to CBs, contrary to our hypothesis, mass loss in the medium-term (two years) was unaffected by N availability in the surrounding substrate. The opposite held for wood sticks, in agreement with the model that N-rich substrates promote the decomposition of other N-poor natural organic materials with a high C/N ratio. As regards CB chemical quality, after two years of decomposition 13C NMR spectroscopy highlighted very small changes in C quality that are likely to reflect a limited microbial attack. PMID:25625643

  1. Cigarette butt decomposition and associated chemical changes assessed by 13C CPMAS NMR.

    PubMed

    Bonanomi, Giuliano; Incerti, Guido; Cesarano, Gaspare; Gaglione, Salvatore A; Lanzotti, Virginia

    2015-01-01

    Cigarette butts (CBs) are the most common type of litter on earth, with an estimated 4.5 trillion discarded annually. Apart from being unsightly, CBs pose a serious threat to living organisms and ecosystem health when discarded in the environment because they are toxic to microbes, insects, fish and mammals. In spite of the CB toxic hazard, no studies have addressed the effects of environmental conditions on CB decomposition rate. In this study we investigate the interactive effects of substrate fertility and N transfer dynamics on CB decomposition rate and carbon quality changes. We carried out an experiment using smoked CBs and wood sticks, used as a slow decomposing standard organic substrate, incubated in both laboratory and field conditions for two years. CB carbon quality changes during decomposition was assessed by 13C CPMAS NMR. Our experiment confirmed the low degradation rate of CBs which, on average, lost only 37.8% of their initial mass after two years of decomposition. Although a net N transfer occurred from soil to CBs, contrary to our hypothesis, mass loss in the medium-term (two years) was unaffected by N availability in the surrounding substrate. The opposite held for wood sticks, in agreement with the model that N-rich substrates promote the decomposition of other N-poor natural organic materials with a high C/N ratio. As regards CB chemical quality, after two years of decomposition 13C NMR spectroscopy highlighted very small changes in C quality that are likely to reflect a limited microbial attack. PMID:25625643

  2. 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

  3. 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.

  4. 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

  5. Metabolism of parenterally administered fat emulsions in the rat: studies of fatty acid oxidation with 1-13C- and 8-13C-labelled triolein.

    PubMed

    Bäurle, W; Brösicke, H; Matthews, D E; Pogan, K; Fürst, P

    1998-04-01

    To reassess the hypothesis that fatty acid catabolism occurs to completion via beta-oxidation, male Sprague-Dawley rats receiving continuous total parenteral nutrition (TPN) including 43% energy as fat were infused with [1-(13)C]- or [8-(13)C]triolein. Expired CO2 was collected continuously for 4 h and its 13C:12C ratio determined by isotope-ratio mass spectrometry. Bicarbonate retention was also assessed over 4 h by infusion of NaH14CO3 and measurement of the expired 14CO2. A possible loss of label from [8-(13)C]oleic acid from the citric acid cycle via labelled acetyl-CoA without oxidation to CO2 was assessed by infusing further animals with acetate labelled with 14C either at C atoms 1 or 2 and determination of its conversion to expired 14CO2. At isotopic steady state, 63.2 (SE 1.6)% (n 8) of the infused [1-(14)C]acetate and 46.0 (SE 1.2)% (n 8) of [2-(14)C]acetate was recovered as expired 14CO2. After correction for bicarbonate retention and non-oxidative isotope loss, 37.3 (SE 1.2)% (n 20) of the [1-(13)C]triolein was found to have been oxidized, whereas 32.6 (SE 1.0)% (n 20) of the [8-(13)C]triolein was oxidized (P < or = 0.01). The lower oxidation of the C atom at position 8 of oleic acid than that at position 1 indicates incomplete oxidative breakdown of the fatty acid after entering beta-oxidation. PMID:9624230

  6. The Dependence of Plant δ13C on Atmospheric pCO2

    NASA Astrophysics Data System (ADS)

    Jahren, H.; Schubert, B.

    2011-12-01

    Numerous studies on multicellular plants have reported increasing carbon isotope fractionation in leaf tissue with increasing concentrations of atmospheric carbon dioxide (pCO2), but the magnitude of the effect is highly variable (i.e., 0.62 to 2.7 % per 100 ppm CO2). The majority of these experiments tested only small differences in CO2 levels (<100 ppm), with maximum concentrations of elevated pCO2 = 700 ppm. In order to quantify how carbon isotope fractionation in plant tissues is affected by the pCO2 concentration under which plants grow, we measured carbon isotope values in a total of 191 Arabidopsis thaliana and Raphanus sativus plants grown under controlled light, water, and temperature conditions, and varying the pCO2 concentrations across a trajectory of 17 different pCO2 levels ranging from 370 to 4200 ppm. From this large dataset, we show that the carbon isotope discrimination [Δδ13C = (δ13CCO2 - δ13Cplant) / (1000 + δ13Cplant)] is indeed a function of pCO2, however, the relationship is hyperbolic, rather than linear, as is typically assumed. Across the small changes in pCO2 previously studied the response appears linear, however, our expanded dataset clearly shows that increases in Δδ13C level off at high pCO2, which is consistent with the ultimate control over fractionation being the activity of Rubisco as the concentration of pCO2 inside the leaf approaches the pCO2 level outside the leaf. The hyperbolic relationship we have quantified using published and new data is extremely robust (R2 = 0.90, n = 26, P < 0.0001), and evident in n-alkanes as well as bulk tissue, suggesting the potential for application to fossil plant materials in order to reconstruct pCO2 across critical intervals.

  7. Body temperatures of modern and extinct vertebrates from 13C-18O bond abundances in bioapatite

    PubMed Central

    Eagle, Robert A.; Schauble, Edwin A.; Tripati, Aradhna K.; Tütken, Thomas; Hulbert, Richard C.; Eiler, John M.

    2010-01-01

    The stable isotope compositions of biologically precipitated apatite in bone, teeth, and scales are widely used to obtain information on the diet, behavior, and physiology of extinct organisms and to reconstruct past climate. Here we report the application of a new type of geochemical measurement to bioapatite, a “clumped-isotope” paleothermometer, based on the thermodynamically driven preference for 13C and 18O to bond with each other within carbonate ions in the bioapatite crystal lattice. This effect is dependent on temperature but, unlike conventional stable isotope paleothermometers, is independent from the isotopic composition of water from which the mineral formed. We show that the abundance of 13C-18O bonds in the carbonate component of tooth bioapatite from modern specimens decreases with increasing body temperature of the animal, following a relationship between isotope “clumping” and temperature that is statistically indistinguishable from inorganic calcite. This result is in agreement with a theoretical model of isotopic ordering in carbonate ion groups in apatite and calcite. This thermometer constrains body temperatures of bioapatite-producing organisms with an accuracy of 1–2 °C. Analyses of fossilized tooth enamel of both Pleistocene and Miocene age yielded temperatures within error of those derived from similar modern taxa. Clumped-isotope analysis of bioapatite represents a new approach in the study of the thermophysiology of extinct species, allowing the first direct measurement of their body temperatures. It will also open new avenues in the study of paleoclimate, as the measurement of clumped isotopes in phosphorites and fossils has the potential to reconstruct environmental temperatures. PMID:20498092

  8. Metabolic Flux Elucidation for Large-Scale Models Using 13C Labeled Isotopes

    PubMed Central

    Suthers, Patrick F.; Burgard, Anthony P.; Dasika, Madhukar S.; Nowroozi, Farnaz; Van Dien, Stephen; Keasling, Jay D.; Maranas, Costas D.

    2007-01-01

    A key consideration in metabolic engineering is the determination of fluxes of the metabolites within the cell. This determination provides an unambiguous description of metabolism before and/or after engineering interventions. Here, we present a computational framework that combines a constraint-based modeling framework with isotopic label tracing on a large-scale. When cells are fed a growth substrate with certain carbon positions labeled with 13C, the distribution of this label in the intracellular metabolites can be calculated based on the known biochemistry of the participating pathways. Most labeling studies focus on skeletal representations of central metabolism and ignore many flux routes that could contribute to the observed isotopic labeling patterns. In contrast, our approach investigates the importance of carrying out isotopic labeling studies using a more comprehensive reaction network consisting of 350 fluxes and 184 metabolites in Escherichia coli including global metabolite balances on cofactors such as ATP, NADH, and NADPH. The proposed procedure is demonstrated on an E. coli strain engineered to produce amorphadiene, a precursor to the anti-malarial drug artemisinin. The cells were grown in continuous culture on glucose containing 20% [U-13C]glucose; the measurements are made using GC-MS performed on 13 amino acids extracted from the cells. We identify flux distributions for which the calculated labeling patterns agree well with the measurements alluding to the accuracy of the network reconstruction. Furthermore, we explore the robustness of the flux calculations to variability in the experimental MS measurements, as well as highlight the key experimental measurements necessary for flux determination. Finally, we discuss the effect of reducing the model, as well as shed light onto the customization of the developed computational framework to other systems. PMID:17632026

  9. In vivo single-shot 13C spectroscopic imaging of hyperpolarized metabolites by spatiotemporal encoding

    NASA Astrophysics Data System (ADS)

    Schmidt, Rita; Laustsen, Christoffer; Dumez, Jean-Nicolas; Kettunen, Mikko I.; Serrao, Eva M.; Marco-Rius, Irene; Brindle, Kevin M.; Ardenkjaer-Larsen, Jan Henrik; Frydman, Lucio

    2014-03-01

    Hyperpolarized metabolic imaging is a growing field that has provided a new tool for analyzing metabolism, particularly in cancer. Given the short life times of the hyperpolarized signal, fast and effective spectroscopic imaging methods compatible with dynamic metabolic characterizations are necessary. Several approaches have been customized for hyperpolarized 13C MRI, including CSI with a center-out k-space encoding, EPSI, and spectrally selective pulses in combination with spiral EPI acquisitions. Recent studies have described the potential of single-shot alternatives based on spatiotemporal encoding (SPEN) principles, to derive chemical-shift images within a sub-second period. By contrast to EPSI, SPEN does not require oscillating acquisition gradients to deliver chemical-shift information: its signal encodes both spatial as well as chemical shift information, at no extra cost in experimental complexity. SPEN MRI sequences with slice-selection and arbitrary excitation pulses can also be devised, endowing SPEN with the potential to deliver single-shot multi-slice chemical shift images, with a temporal resolution required for hyperpolarized dynamic metabolic imaging. The present work demonstrates this with initial in vivo results obtained from SPEN-based imaging of pyruvate and its metabolic products, after injection of hyperpolarized [1-13C]pyruvate. Multi-slice chemical-shift images of healthy rats were obtained at 4.7 T in the region of the kidney, and 4D (2D spatial, 1D spectral, 1D temporal) data sets were obtained at 7 T from a murine lymphoma tumor model.

  10. Continuous-flow 13C-filtered 1H NMR spectroscopy of ethanol metabolism in rat liver perfusate.

    PubMed

    Albert, K; Sudmeier, J L; Anwer, M S; Bachovchin, W W

    1989-09-01

    Using a 188.5-microliters continuous-flow dual probe 1H[13C] spin-echo difference spectra of rat liver perfusate were acquired. The conversion of [1-13C]ethanol to [1-13C]-acetaldehyde was readily monitored as a function of time. In combination with 1-1 water nonexcitation and WALTZ 13C decoupling, this method proved to be superior in sensitivity and selectivity to direct 1H or 13C detection. PMID:2779419

  11. 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).

  12. Simultaneous imaging of 13C metabolism and 1H structure: technical considerations and potential applications.

    PubMed

    Gordon, Jeremy W; Fain, Sean B; Niles, David J; Ludwig, Kai D; Johnson, Kevin M; Peterson, Eric T

    2015-05-01

    Real-time imaging of (13)C metabolism in vivo has been enabled by recent advances in hyperpolarization. As a result of the inherently low natural abundance of endogenous (13)C nuclei, hyperpolarized (13)C images lack structural information that could be used to aid in motion detection and anatomical registration. Motion before or during the (13)C acquisition can therefore result in artifacts and misregistration that may obscure measures of metabolism. In this work, we demonstrate a method to simultaneously image both (1)H and (13)C nuclei using a dual-nucleus spectral-spatial radiofrequency excitation and a fully coincident readout for rapid multinuclear spectroscopic imaging. With the appropriate multinuclear hardware, and the means to simultaneously excite and receive on both channels, this technique is straightforward to implement requiring little to no increase in scan time. Phantom and in vivo experiments were performed with both Cartesian and spiral trajectories to validate and illustrate the utility of simultaneous acquisitions. Motion compensation of dynamic metabolic measurements acquired during free breathing was demonstrated using motion tracking derived from (1)H data. Simultaneous multinuclear imaging provides structural (1)H and metabolic (13)C images that are correlated both spatially and temporally, and are therefore amenable to joint (1)H and (13)C analysis and correction of structure-function images. PMID:25810146

  13. 13C-NMR study of labeled vinyl groups in paramagnetic myoglobin derivatives.

    PubMed

    Sankar, S S; La Mar, G N; Smith, K M; Fujinari, E M

    1987-04-01

    The 13C-NMR spectra of high-spin met-aquo myoglobin, spin-equilibrium met-azido myoglobin, low-spin met-cyano myoglobin, deoxy myoglobin and carbonmonoxy myoglobin from sperm whale reconstituted with hemin 13C enriched at both vinyl alpha or beta positions have been recorded. In all cases the labeled vinyl 13C signals are clearly resolved and useful spectra could be obtained within approx. 15 minutes. The decoupling of multiplet structure due to attached proton(s) has led to the specific assignment of vinyl 13C alpha signals in all paramagnetic derivatives and the 13C beta signals in met-cyano myoglobin. In all other cases, the collapse of the proton multiplet structure as a function of 1H decoupling frequency has located, but not assigned, the attached 1H resonance positions which are obscured by the intense diamagnetic envelope in the 1H-NMR spectrum. The resulting vinyl 13C hyperfine shifts follow Curie behavior, and the patterns closely resemble those in the appropriate model complexes in the same oxidation/spin/ligation state, except that the protein exhibits more in-plane asymmetry. The hyperfine shift patterns are indicative of dominant pi contact shifts for all ferric complexes. Deoxy myoglobin vinyl 13C and 1H contact shifts provide little evidence for pi bonding. PMID:3828362

  14. Dephosphorylation and biodistribution of 1-13C-phospholactate in vivo†

    PubMed Central

    Shchepin, Roman V.; Pham, Wellington; Chekmenev, Eduard Y.

    2015-01-01

    Here, we present a new approach for the delivery of a metabolic contrast agent for in vivo molecular imaging. The use of a phosphate-protecting group that facilitates parahydrogen-induced polarization of 1-13C-phospholactate potentially enables the in vivo administration of a hydrogenated hyperpolarized adduct. When injected, nonhyperpolarized 1-13C-phospholactate is retained in the vasculature during its metabolic conversion to 1-13C-lactate by blood phosphatases as demonstrated here using a mucin 1 mouse model of breast cancer and ex vivo high-resolution 13C NMR. This multisecond process is a suitable mechanism for the delivery of relatively short-lived 13C and potentially 15N hyperpolarized contrast agents using –OH phosphorylated small molecules, which is demonstrated here for the first time as an example of 1-13C-phospholactate. Through this approach, DL-1-13C-lactate is taken up by tissues and organs including the liver, kidneys, brain, heart, and tumors according to a timescale amenable to hyperpolarized magnetic resonance imaging. PMID:24995802

  15. 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

  16. 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

  17. Comprehensive signal assignment of 13C-labeled lignocellulose using multidimensional solution NMR and 13C chemical shift comparison with solid-state NMR.

    PubMed

    Komatsu, Takanori; Kikuchi, Jun

    2013-09-17

    A multidimensional solution NMR method has been developed using various pulse programs including HCCH-COSY and (13)C-HSQC-NOESY for the structural characterization of commercially available (13)C labeled lignocellulose from potatoes (Solanum tuberosum L.), chicory (Cichorium intybus), and corn (Zea mays). This new method allowed for 119 of the signals in the (13)C-HSQC spectrum of lignocelluloses to be assigned and was successfully used to characterize the structures of lignocellulose samples from three plants in terms of their xylan and xyloglucan structures, which are the major hemicelluloses in angiosperm. Furthermore, this new method provided greater insight into fine structures of lignin by providing a high resolution to the aromatic signals of the β-aryl ether and resinol moieties, as well as the diastereomeric signals of the β-aryl ether. Finally, the (13)C chemical shifts assigned in this study were compared with those from solid-state NMR and indicated the presence of heterogeneous dynamics in the polysaccharides where rigid cellulose and mobile hemicelluloses moieties existed together. PMID:24010724

  18. Determination of [{sup 13}C]pyrene sequestration in sediment microcosms using flash pyrolysis--GC--MS and {sup 13}C NMR

    SciTech Connect

    Guthrie, E.A.; Bortiatynski, J.M.; Hardy, K.S.; Kovach, E.M.; Van Heemst, J.D.H.; Hatcher, P.G.; Richman, J.E.

    1999-01-01

    In this study, the use of a {sup 13}C-labeled pollutant probe, [{sup 13}C]pyrene, and the application of flash pyrolysis--GC--MS and CPMAS {sup 13}C NMR provided analytical capabilities to study pyrene interactions with soluble and insoluble compartments of sedimentary organic matter (S{sub D}OM) during whole sediments incubations in aerated microcosms. Surface sediments were collected from a site of previous hydrocarbon contamination in New Orleans, LA. Over a period of 60 days, humic acid and humin fractions of S{sub D}OM accumulated increasing amounts of pyrene that were resistant to exhaustive extraction with organic solvents. The sequestered pyrene was evident in CPMAS {sup 13}C NMR spectra of humin fractions. The amount of sequestered pyrene in humic materials was quantified by flash pyrolysis--GC--MS, a technique that destroys the three-dimensional structure of macromolecular S{sub D}OM. Noncovalent binding of pyrene to humic materials in S{sub D}OM was greater in sediments incubated with biological activity than biocide-treated sediments. The combined analytical approaches demonstrate that the sequestered pyrene, or bound residue, is noncovalently associated with S{sub D}OM and has not undergone structural alteration. Implications of these data are discussed in reference to S{sub D}OM diagenesis and long-term availability of bound pollutant residues in sediments.

  19. 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

  20. High-field dissolution dynamic nuclear polarization of [1-(13)C]pyruvic acid.

    PubMed

    Yoshihara, Hikari A I; Can, Emine; Karlsson, Magnus; Lerche, Mathilde H; Schwitter, Juerg; Comment, Arnaud

    2016-05-14

    [1-(13)C]pyruvate is the most widely used hyperpolarized metabolic magnetic resonance imaging agent. Using a custom-built 7.0 T polarizer operating at 1.0 K and trityl radical-doped [1-(13)C]pyruvic acid, unextrapolated solution-state (13)C polarization greater than 60% was measured after dissolution and rapid transfer to a spectrometer magnet, demonstrating the signal enhancement attainable using optimized hardware. Slower rates of polarization under these conditions can be largely overcome with higher radical concentrations. PMID:27093499

  1. 13C NMR spectroscopy of methane adsorbed in SAPO-11 molecular sieve

    NASA Astrophysics Data System (ADS)

    Koskela, Tuomas; Ylihautala, Mika; Vaara, Juha; Jokisaari, Jukka

    1996-10-01

    Static 13C and 13C-{ 1H} NMR spectra of carbon-13 enriched methane ( 13CH 4) adsorbed into SAPO-11 molecular sieve were recorded at variable temperatures. Moreover, the corresponding MAS NMR spectra were measured. These experiments reveal a temperature-dependent, anisotropic and asymmetric 13C nuclear shielding tensor. Ab initio model calculations of methane in the field of a positive point charge suggest that the deformation of the shielding tensor may be related to the interaction between the methane molecule and the charge-compensating protons. A comparison with existing Xe data is made.

  2. 13C Nuclear magnetic resonance studies of kerogen from Cretaceous black shales thermally altered by basaltic intrusions and laboratory simulations

    USGS Publications Warehouse

    Dennis, L.W.; Maciel, G.E.; Hatcher, P.G.; Simoneit, B.R.T.

    1982-01-01

    Cretaceous black shales from DSDP Leg 41, Site 368 in the Eastern Atlantic Ocean were thermally altered during the Miocene by an intrusive basalt. The sediments overlying and underlying the intrusive body were subjected to high temperatures (up to ~ 500??C) and, as a result, their kerogen was significantly altered. The extent of this alteration has been determined by examination by means of 13C nuclear magnetic resonance, using cross polarization/magic-angle spinning (CP/MAS). Results indicate that the kerogen becomes progressively more aromatic in the vicinity of the intrusive body. Laboratory heating experiments, simulating the thermal effects of the basaltic intrusion, produced similar results on unaltered shale from the drill core. The 13C CP/MAS results appear to provide a good measure of thermal alteration. ?? 1982.

  3. The B 2Σ+→X 2Σ+, 2-v'' progression in the spectrum of 13C16O+

    NASA Astrophysics Data System (ADS)

    Kepa, R.; Malak, Z.; Szajna, W.; Zachwieja, M.

    2002-03-01

    Emission spectra of the 2-v'' progression (1≤v''≤6) in the B 2Σ+→X 2Σ+ system of 13C16O+ have been photographically recorded at a resolution that was high enough to achieve a clear separation of the spin components for most of the observed rovibronic transitions. Least-squares methods were used to reduce the measured line wavenumbers to the molecular constants appearing in the effective Hamiltonian taken from the work of Amiot et al (Amiot C, Maillard J P and Chauville J 1981 J. Mol. Spectrosc. 87 196-218). Merging of the data for the v' = 2 progression with previous measurements in the v' = 0 and 1 progressions resulted in considerably improved equilibrium molecular constants, RKR potential curves, Franck-Condon factors and r centroids for the B→X system of 13C16O+.

  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. 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.

  6. 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.

  7. Trimethylation Enhancement Using (13)C-Diazomethane ((13)C-TrEnDi): Increased Sensitivity and Selectivity of Phosphatidylethanolamine, Phosphatidylcholine, and Phosphatidylserine Lipids Derived from Complex Biological Samples.

    PubMed

    Canez, Carlos R; Shields, Samuel W J; Bugno, Magdalena; Wasslen, Karl V; Weinert, Hillary P; Willmore, William G; Manthorpe, Jeffrey M; Smith, Jeffrey C

    2016-07-19

    Significant sensitivity enhancements in the tandem mass spectrometry-based analysis of complex mixtures of several phospholipid classes has been achieved via (13)C-TrEnDi. (13)C-TrEnDi-modified phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidylcholine (PC) lipids extracted from HeLa cells demonstrated greater sensitivity via precursor ion scans (PISs) than their unmodified counterparts. Sphingomyelin (SM) species exhibited neither an increased nor decreased sensitivity following modification. The use of isotopically labeled diazomethane enabled the distinction of modified PE and modified PC species that would yield isobaric species with unlabeled diazomethane. (13)C-TrEnDi created a PE-exclusive PIS of m/z 202.1, two PS-exclusive PISs of m/z 148.1 and m/z 261.1, and a PIS of m/z 199.1 for PC species (observed at odd m/z values) and SM species (observed at even m/z values). The standardized average area increase after TrEnDi modification was 10.72-fold for PE species, 2.36-fold for PC, and 1.05-fold for SM species. The sensitivity increase of PS species was not quantifiable, as there were no unmodified PS species identified prior to derivatization. (13)C-TrEnDi allowed for the identification of 4 PE and 7 PS species as well as the identification and quantitation of an additional 4 PE and 4 PS species that were below the limit of detection (LoD) prior to modification. (13)C-TrEnDi also pushed 24 PE and 6 PC lipids over the limit of quantitation (LoQ) that prior to modification were above the LoD only. PMID:27275841

  8. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    DOE PAGESBeta

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; et al

    2014-09-10

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has anmore » exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, probably the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs while processes within leaves or during phloem loading may contribute to the overall autotrophic – heterotrophic difference in carbon isotope compositions.« less

  9. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; Wu, R.; Yao, B.; Zhao, Y.; Lin, G.; Wu, B.; Lu, Q.; Meng, P.

    2014-09-01

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, probably the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs while processes within leaves or during phloem loading may contribute to the overall autotrophic - heterotrophic difference in carbon isotope compositions.

  10. Microbial transformations of free versus sorbed alanine analyzed by position-specific 13C and 14C labeling and 13C-PLFA analysis

    NASA Astrophysics Data System (ADS)

    Apostel, Carolin; Dippold, Michaela; Bore, Ezekiel; Kuzyakov, Yakov

    2015-04-01

    Sorption of charged or partially charged low molecular weight organic substances (LMWOS) to soil mineral surfaces delays microbial uptake and therefore mineralization of LMWOS to CO2, as well as all other biochemical transformations. We used position-specific labeling, a tool of isotope applications novel to soil sciences, to compare the transformation mechanisms of sorbed and non-sorbed alanine in soil. Alanine as an amino acid links C- and N-cycles in soil and therefore is a model representative for the pool of LMWOS. To assess transformations of sorbed alanine, we combined position-specifically and uniformly 13C and 14C labeled alanine tracer solution with a loamy haplic luvisol that had previously been sterilized by γ-radiation. After shaking the mixtures, the supernatant was removed, as was all non-sorbed alanine by repeated shaking with millipore water. The labeled soil was added to non-sterilized soil from the same site. To compare the effect of sorption, soil labeled with the same position-specifically labeled tracers without previous sorption was prepared and incubated as well. We captured the respired CO2 and determined its 14C-activity at increasing time steps. The incorporation of 14C into microbial biomass was determined by CFE, and utilization of individual C positions by distinct microbial groups was evaluated by 13C-PLFA analysis. A dual peak in the respired CO2 revealed the influence of two sorption mechanisms. Microbial uptake and transformation of the sorbed alanine was 3 times slower compared to non-sorbed alanine. To compare the fate of individual C atoms independent of their concentration and pool size in soil, we introduced the divergence index (DI). The DI reveals the convergent or divergent behaviour of C from individual molecule positions during microbial utilization. The DI revealed, that alanines C-1 position was mainly oxidized to CO2, while its C-2 and C-3 were preferentially incorporated in microbial biomass and PLFAs. This indicates

  11. 13C MR imaging of methionine-rich gliomas at 4.7T: a pilot study.

    PubMed

    Sasao, Akira; Hirai, Toshinori; Iriguchi, Norio; Nakamura, Hideo; Kudo, Mareina; Sasao, Ako; Yamashita, Yasuyuki

    2011-01-01

    We explored the feasibility of using carbon-13 ((13)C) magnetic resonance imaging ((13)C-MRI) to depict (13)C-labeled methionine-enriched gliomas at 4.7 tesla. We transplanted 2 types of glioma cells separately to 2 subcutaneous tissue sites on the backs of mice weighing 15 to 20 g. After confirming tumor growth, we used (13)C-MRI and (1)H-MRI to scan 4 mice that had been administered (13)C-labeled methionine and 2 control mice. (13)C-MRI of all 4 transplanted mice administered with (13)C-labeled methionine revealed 2 areas of hyperintensity that corresponded to the tumor sites on (1)H-MR images, but no such areas were visualized in transplanted controls. Our data suggest that (13)C-MRI can show the accumulation of (13)C-labeled tracer by gliomas. PMID:21720117

  12. Separation of extra- and intracellular metabolites using hyperpolarized 13C diffusion weighted MR

    NASA Astrophysics Data System (ADS)

    Koelsch, Bertram L.; Sriram, Renuka; Keshari, Kayvan R.; Leon Swisher, Christine; Van Criekinge, Mark; Sukumar, Subramaniam; Vigneron, Daniel B.; Wang, Zhen J.; Larson, Peder E. Z.; Kurhanewicz, John

    2016-09-01

    This work demonstrates the separation of extra- and intracellular components of glycolytic metabolites with diffusion weighted hyperpolarized 13C magnetic resonance spectroscopy. Using b-values of up to 15,000 s mm-2, a multi-exponential signal response was measured for hyperpolarized [1-13C] pyruvate and lactate. By fitting the fast and slow asymptotes of these curves, their extra- and intracellular weighted diffusion coefficients were determined in cells perfused in a MR compatible bioreactor. In addition to measuring intracellular weighted diffusion, extra- and intracellular weighted hyperpolarized 13C metabolites pools are assessed in real-time, including their modulation with inhibition of monocarboxylate transporters. These studies demonstrate the ability to simultaneously assess membrane transport in addition to enzymatic activity with the use of diffusion weighted hyperpolarized 13C MR. This technique could be an indispensible tool to evaluate the impact of microenvironment on the presence, aggressiveness and metastatic potential of a variety of cancers.

  13. Fusion cross section of 12C+13C at sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Zhang, N. T.; Tang, X. D.; Chen, H.; Chesneanu, D.; Straticiuc, M.; Trache, L.; Burducea, I.; Li, K. A.; Li, Y. J.; Ghita, D. G.; Margineanu, R.; Pantelica, A.; Gomoiu, C.

    2016-02-01

    In the recent work at Notre Dame, correlations between three carbon isotope fusion systems have been studied and it is found that the fusion cross sections of 12C+13Cand 13C+13C provide an upper limit on the fusion cross section of the astrophysically important 12C+12C reaction.The aim of this work is to continue such research by measuring the fusion cross section of the 12C+13C reaction to lower energies. In this experiment, the off-line activity measurement was performed in the ultra-low background laboratory 12C+13C and the fusion cross section for has been determined in the energy range of Ec.m. =2.5-6.8 MeV. Comparison between this work and several models is also presented.

  14. Strongly polarizing weakly coupled 13C nuclear spins with optically pumped nitrogen-vacancy center

    PubMed Central

    Wang, Ping; Liu, Bao; Yang, Wen

    2015-01-01

    Enhancing the polarization of nuclear spins surrounding the nitrogen-vacancy (NV) center in diamond has recently attracted widespread attention due to its various applications. Here we present an analytical formula that not only provides a clear physical picture for the recently observed polarization reversal of strongly coupled13C nuclei over a narrow range of magnetic field [H. J. Wang et al., Nat. Commun. 4, 1940 (2013)], but also demonstrates the possibility to strongly polarize weakly coupled13C nuclei. This allows sensitive magnetic field control of the 13C nuclear spin polarization for NMR applications and significant suppression of the 13C nuclear spin noise to prolong the NV spin coherence time. PMID:26521962

  15. 13C-DEPLETED MICROBIAL LIPIDS INDICATE SEASONAL METHANOTROPHIC ACTIVITY IN SHALLOW ESTUARINE SEDIMENTS

    EPA Science Inventory

    Compound specific isotope analysis was combined with phospholipid fatty acid (PLFA) analysis to identify methanotrophic activity in members of the sedimentary microbial community in the Altamaha and Savannah River estuaries in Georgia. 13C-depleted PLFAs indicate methane utilizat...

  16. Separation of extra- and intracellular metabolites using hyperpolarized (13)C diffusion weighted MR.

    PubMed

    Koelsch, Bertram L; Sriram, Renuka; Keshari, Kayvan R; Leon Swisher, Christine; Van Criekinge, Mark; Sukumar, Subramaniam; Vigneron, Daniel B; Wang, Zhen J; Larson, Peder E Z; Kurhanewicz, John

    2016-09-01

    This work demonstrates the separation of extra- and intracellular components of glycolytic metabolites with diffusion weighted hyperpolarized (13)C magnetic resonance spectroscopy. Using b-values of up to 15,000smm(-2), a multi-exponential signal response was measured for hyperpolarized [1-(13)C] pyruvate and lactate. By fitting the fast and slow asymptotes of these curves, their extra- and intracellular weighted diffusion coefficients were determined in cells perfused in a MR compatible bioreactor. In addition to measuring intracellular weighted diffusion, extra- and intracellular weighted hyperpolarized (13)C metabolites pools are assessed in real-time, including their modulation with inhibition of monocarboxylate transporters. These studies demonstrate the ability to simultaneously assess membrane transport in addition to enzymatic activity with the use of diffusion weighted hyperpolarized (13)C MR. This technique could be an indispensible tool to evaluate the impact of microenvironment on the presence, aggressiveness and metastatic potential of a variety of cancers. PMID:27434780

  17. Preparation of 13C/15N-labeled oligomers using the polymerase chain reaction

    DOEpatents

    Chen, Xian; Gupta, Goutam; Bradbury, E. Morton

    2001-01-01

    Preparation of .sup.13 C/.sup.15 N-labeled DNA oligomers using the polymerase chain reaction (PCR). A PCR based method for uniform (.sup.13 C/.sup.15 N)-labeling of DNA duplexes is described. Multiple copies of a blunt-ended duplex are cloned into a plasmid, each copy containing the sequence of interest and restriction Hinc II sequences at both the 5' and 3' ends. PCR using bi-directional primers and uniformly .sup.13 C/.sup.15 N-labeled dNTP precursors generates labeled DNA duplexes containing multiple copies of the sequence of interest. Twenty-four cycles of PCR, followed by restriction and purification, gave the uniformly .sup.13 C/.sup.15 N-labeled duplex sequence with a 30% yield. Such labeled duplexes find significant applications in multinuclear magnetic resonance spectroscopy.

  18. Natural abundance measurements of 13C indicate increased deep soil carbon mineralization after forest disturbance

    NASA Astrophysics Data System (ADS)

    Diochon, Amanda; Kellman, Lisa

    2008-07-01

    Northern forest soils represent globally important stores of carbon (C), yet there is no consensus about how they are altered by the widespread practice of harvesting that dominates many forested landscapes. Here we present the first study to systematically investigate the utility of δ 13C and C content depth profiles to infer temporal changes in belowground carbon cycling processes following disturbance in a pure C3 ecosystem. We document carbon concentration and δ 13C depth profile enrichment trends consistent with a kinetic fractionation arising from soil organic carbon (SOC) humification across a northern forest chronosequence (1, 15, 45, 80 and 125+ yrs). Reduced soil C storage that coincided with observed soil profile δ 13C-enrichment patterns which intensified following clearcut harvesting, pointed to losses of SOC in the deeper (>20 cm) mineral soil. This study suggests the δ 13C approach may assist in identifying mechanisms responsible for soil C storage changes in disturbed C3 forest ecosystems.

  19. 2H-DNP-enhanced 2H–13C solid-state NMR correlation spectroscopy

    PubMed Central

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

    2015-01-01

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

  20. Spectroscopic study and astronomical detection of doubly 13C-substituted ethyl cyanide

    NASA Astrophysics Data System (ADS)

    Margulès, L.; Belloche, A.; Müller, H. S. P.; Motiyenko, R. A.; Guillemin, J.-C.; Garrod, R. T.; Menten, K. M.

    2016-05-01

    Context. We have performed a spectral line survey called Exploring Molecular Complexity with ALMA (EMoCA) toward Sagittarius B2(N) between 84.1 and 114.4 GHz with the Atacama Large Millimeter/submillimeter Array (ALMA) in its Cycles 0 and 1. Line intensities of the main isotopic species of ethyl cyanide and its singly 13C-substituted isotopomers observed toward the hot molecular core Sagittarius B2(N2) suggest that the doubly 13C-substituted isotopomers should also be detectable. Aims: We want to determine the spectroscopic parameters of all three doubly 13C-substituted isotopologues of ethyl cyanide to search for them in our ALMA data. Methods: We investigated the laboratory rotational spectra of the three species between 150 GHz and 990 GHz. We searched for emission lines produced by these species in the ALMA spectrum of Sagittarius B2(N2). We modeled their emission and the emission of the 12C and singly 13C-substituted isotopologues assuming local thermodynamic equilibrium. Results: 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. Conclusions: 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 ν19 = 1 at ~1130 K and up to ν13 + ν21 = 2 at ~600 K for the isotopologues with one 13C atom in

  1. A procedure to validate and correct the 13C chemical shift calibration of RNA datasets.

    PubMed

    Aeschbacher, Thomas; Schubert, Mario; Allain, Frédéric H-T

    2012-02-01

    Chemical shifts reflect the structural environment of a certain nucleus and can be used to extract structural and dynamic information. Proper calibration is indispensable to extract such information from chemical shifts. Whereas a variety of procedures exist to verify the chemical shift calibration for proteins, no such procedure is available for RNAs to date. We present here a procedure to analyze and correct the calibration of (13)C NMR data of RNAs. Our procedure uses five (13)C chemical shifts as a reference, each of them found in a narrow shift range in most datasets deposited in the Biological Magnetic Resonance Bank. In 49 datasets we could evaluate the (13)C calibration and detect errors or inconsistencies in RNA (13)C chemical shifts based on these chemical shift reference values. More than half of the datasets (27 out of those 49) were found to be improperly referenced or contained inconsistencies. This large inconsistency rate possibly explains that no clear structure-(13)C chemical shift relationship has emerged for RNA so far. We were able to recalibrate or correct 17 datasets resulting in 39 usable (13)C datasets. 6 new datasets from our lab were used to verify our method increasing the database to 45 usable datasets. We can now search for structure-chemical shift relationships with this improved list of (13)C chemical shift data. This is demonstrated by a clear relationship between ribose (13)C shifts and the sugar pucker, which can be used to predict a C2'- or C3'-endo conformation of the ribose with high accuracy. The improved quality of the chemical shift data allows statistical analysis with the potential to facilitate assignment procedures, and the extraction of restraints for structure calculations of RNA. PMID:22252483

  2. (13)C-Breath testing in animals: theory, applications, and future directions.

    PubMed

    McCue, Marshall D; Welch, Kenneth C

    2016-04-01

    The carbon isotope values in the exhaled breath of an animal mirror the carbon isotope values of the metabolic fuels being oxidized. The measurement of stable carbon isotopes in carbon dioxide is called (13)C-breath testing and offers a minimally invasive method to study substrate oxidation in vivo. (13)C-breath testing has been broadly used to study human exercise, nutrition, and pathologies since the 1970s. Owing to reduced use of radioactive isotopes and the increased convenience and affordability of (13)C-analyzers, the past decade has witnessed a sharp increase in the use of breath testing throughout comparative physiology-especially to answer questions about how and when animals oxidize particular nutrients. Here, we review the practical aspects of (13)C-breath testing and identify the strengths and weaknesses of different methodological approaches including the use of natural abundance versus artificially-enriched (13)C tracers. We critically compare the information that can be obtained using different experimental protocols such as diet-switching versus fuel-switching. We also discuss several factors that should be considered when designing breath testing experiments including extrinsic versus intrinsic (13)C-labelling and different approaches to model nutrient oxidation. We use case studies to highlight the myriad applications of (13)C-breath testing in basic and clinical human studies as well as comparative studies of fuel use, energetics, and carbon turnover in multiple vertebrate and invertebrate groups. Lastly, we call for increased and rigorous use of (13)C-breath testing to explore a variety of new research areas and potentially answer long standing questions related to thermobiology, locomotion, and nutrition. PMID:26660654

  3. Galacto-oligosaccharides have prebiotic activity in a dynamic in vitro colon model using a (13)C-labeling technique.

    PubMed

    Maathuis, Annet J H; van den Heuvel, Ellen G; Schoterman, Margriet H C; Venema, Koen

    2012-07-01

    Galacto-oligosaccharides (GOS) are considered to be prebiotic, although the contribution of specific members of the microbiota to GOS fermentation and the exact microbial metabolites that are produced upon GOS fermentation are largely unknown. We aimed to determine this using uniformly (13)C-labeled GOS. The normal (control) medium and unlabeled or (13)C-labeled GOS was added to a dynamic, validated, in vitro model of the large-intestine containing an adult-type microbiota. Liquid-chromatography MS was used to measure the incorporation of (13)C label into metabolites. 16S-rRNA stable isotope probing coupled to a phylogenetic micro-array was used to determine label incorporation in microbial biomass. The primary members within the complex microbiota that were directly involved in GOS fermentation were shown to be Bifidobacterium longum, B. bifidum, B. catenulatum, Lactobacillus gasseri, and L. salivarius, in line with the prebiotic effect of GOS, although some other species incorporated (13)C label also. GOS fermentation led to an increase in acetate (+49%) and lactate (+23%) compared with the control. Total organic acid production was 8.50 and 7.52 mmol/g of carbohydrate fed for the GOS and control experiments, respectively. At the same time, the cumulative production of putrefactive metabolites (branched-chain fatty acids and ammonia) was reduced by 55%. Cross-feeding of metabolites from primary GOS fermenters to other members of the microbiota was observed. Our findings support a prebiotic role for GOS and its potential to act as a synbiotic in combination with certain probiotic strains. PMID:22623395

  4. Continuous flow stable isotope methods for study of δ13C fractionation during halomethane production and degradation

    USGS Publications Warehouse

    Kalin, Robert M.; Hamilton, John T.G.; Harper, David B.; Miller, Laurence G.; Lamb, Clare; Kennedy, James T.; Downey, Angela; McCauley, Sean; Goldstein, Allen H.

    2001-01-01

    Gas chromatography/mass spectrometry/isotope ratio mass spectrometry (GC/MS/IRMS) methods for δ13C measurement of the halomethanes CH3Cl, CH3Br, CH3I and methanethiol (CH3SH) during studies of their biological production, biological degradation, and abiotic reactions are presented. Optimisation of gas chromatographic parameters allowed the identification and quantification of CO2, O2, CH3Cl, CH3Br, CH3I and CH3SH from a single sample, and also the concurrent measurement of δ13C for each of the halomethanes and methanethiol. Precision of δ13C measurements for halomethane standards decreased (±0.3, ±0.5 and ±1.3‰) with increasing mass (CH3Cl, CH3Br, CH3I, respectively). Given that carbon isotope effects during biological production, biological degradation and some chemical (abiotic) reactions can be as much as 100‰, stable isotope analysis offers a precise method to study the global sources and sinks of these halogenated compounds that are of considerable importance to our understanding of stratospheric ozone destruction. 

  5. Individual protein balance strongly influences δ15N and δ13C values in Nile tilapia, Oreochromis niloticus

    NASA Astrophysics Data System (ADS)

    Gaye-Siessegger, Julia; Focken, Ulfert; Abel, Hansjörg; Becker, Klaus

    Although stable isotope ratios in animals have often been used as indicators of the trophic level and for the back-calculation of diets, few experiments have been done under standardized laboratory conditions to investigate factors influencing δ15N and δ13C values. An experiment using Nile tilapia [Oreochromis niloticus (L.)] was therefore carried out to test the effect of different dietary protein contents (35.4, 42.3, and 50.9%) on δ15N and δ13C values of the whole tilapia. The fish were fed the isoenergetic and isolipidic semi-synthetic diets at a relatively low level. δ15N and δ13C values of the lipid-free body did not differ between the fish fed the diets with different protein contents, but the trophic shift for N and C isotopes decreased with increasing protein accretion in the individual fish, for N from 6.5‰ to 4‰ and for C in the lipid-free body from 4‰ to 2.5‰. This is the first study showing the strong influence of the individual protein balance to the degree to which the isotopic signature of dietary protein was modified in tissue protein of fish. The extrapolation of the trophic level or the reconstruction of the diet of an animal from stable isotope ratios without knowledge of the individual physiological condition and the feeding rate may lead to erroneous results.

  6. Biosynthetic preparation of L-(/sup 13/C)- and (/sup 15/N)glutamate by Brevibacterium flavum

    SciTech Connect

    Walker, T.E.; London, R.E.

    1987-01-01

    The biosynthesis of isotopically labeled L-glutamic acid by the microorganism Brevibacterium flavum was studied with a variety of carbon-13-enriched precursors. The purpose of this study was twofold: (i) to develop techniques for the efficient preparation of labeled L-glutamate with a variety of useful labeling patterns which can be used for other metabolic studies, and (ii) to better understand the metabolic events leading to label scrambling in these strains. B. flavum, which is used commercially for the production of monosodium glutamate, has the capability of utilizing glucose or acetate as a sole carbon source, and important criterion from the standpoint of developing labeling strategies. Unfortunately, singly labeled glucose precursors lead to excessive isotopic dilution which reduces their usefulness. Studies with (3-/sup 13/C)pyruvate indicate that this problem can in principle be overcome by using labeled three-carbon precursors; however, conditions could not be found which would lead to an acceptable yield of isotopically labeled L-glutamate. In contrast, (1-/sup 13/C)- or (2-/sup 13/C)acetate provides relatively inexpensive, readily available precursors for the production of selectively labeled, high enriched L-glutamate. The preparation of L-(/sup 15/N)glutamate from (/sup 15/N)ammonium sulfate was carried out and is a very effective labeling strategy. Analysis of the isotopic distribution in labeled glutamate provides details about the metabolic pathways in these interesting organisms.

  7. Uranyl nitrate inhibits lactate gluconeogenesis in isolated human and mouse renal proximal tubules: A {sup 13}C-NMR study

    SciTech Connect

    Renault, Sophie; Faiz, Hassan; Gadet, Rudy; Ferrier, Bernard; Martin, Guy; Baverel, Gabriel; Conjard-Duplany, Agnes

    2010-01-01

    As part of a study on uranium nephrotoxicity, we investigated the effect of uranyl nitrate in isolated human and mouse kidney cortex tubules metabolizing the physiological substrate lactate. In the millimolar range, uranyl nitrate reduced lactate removal and gluconeogenesis and the cellular ATP level in a dose-dependent fashion. After incubation in phosphate-free Krebs-Henseleit medium with 5 mM L-[1-{sup 13}C]-, or L-[2-{sup 13}C]-, or L-[3-{sup 13}C]lactate, substrate utilization and product formation were measured by enzymatic and NMR spectroscopic methods. In the presence of 3 mM uranyl nitrate, glucose production and the intracellular ATP content were significantly reduced in both human and mouse tubules. Combination of enzymatic and NMR measurements with a mathematical model of lactate metabolism revealed an inhibition of fluxes through lactate dehydrogenase and the gluconeogenic enzymes in the presence of 3 mM uranyl nitrate; in human and mouse tubules, fluxes were lowered by 20% and 14% (lactate dehydrogenase), 27% and 32% (pyruvate carboxylase), 35% and 36% (phosphoenolpyruvate carboxykinase), and 39% and 45% (glucose-6-phosphatase), respectively. These results indicate that natural uranium is an inhibitor of renal lactate gluconeogenesis in both humans and mice.

  8. 13C and 15N fractionation of CH4/N2 mixtures during photochemical aerosol formation: Relevance to Titan

    NASA Astrophysics Data System (ADS)

    Sebree, Joshua A.; Stern, Jennifer C.; Mandt, Kathleen E.; Domagal-Goldman, Shawn D.; Trainer, Melissa G.

    2016-05-01

    The ratios of the stable isotopes that comprise each chemical species in Titan's atmosphere provide critical information towards understanding the processes taking place within its modern and ancient atmosphere. Several stable isotope pairs, including 12C/13C and 14N/15N, have been measured in situ or probed spectroscopically by Cassini-borne instruments, space telescopes, or through ground-based observations. Current attempts to model the observed isotope ratios incorporate fractionation resulting from atmospheric diffusion, hydrodynamic escape, and primary photochemical processes. However, the effect of a potentially critical pathway for isotopic fractionation - organic aerosol formation and subsequent deposition onto the surface of Titan - has not been considered due to insufficient data regarding fractionation during aerosol formation. To better understand the nature of this process, we have conducted a laboratory study to measure the isotopic fractionation associated with the formation of Titan aerosol analogs, commonly referred to as 'tholins', via far-UV irradiation of several methane (CH4) and dinitrogen (N2) mixtures. Analysis of the δ13C and δ15N isotopic signatures of the photochemical aerosol products using an isotope ratio mass spectrometer (IRMS) show that fractionation direction and magnitude are dependent on the initial bulk composition of the gas mixture. In general, the aerosols showed enrichment in 13C and 14N, and the observed fractionation trends can provide insight into the chemical mechanisms controlling photochemical aerosol formation.

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

    PubMed

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

    2006-02-01

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

  10. Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite.

    PubMed

    Drake, Henrik; Åström, Mats E; Heim, Christine; Broman, Curt; Åström, Jan; Whitehouse, Martin; Ivarsson, Magnus; Siljeström, Sandra; Sjövall, Peter

    2015-01-01

    Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C13C as light as -69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to -125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane. PMID:25948095

  11. Extreme 13C depletion of carbonates formed during oxidation of biogenic methane in fractured granite

    PubMed Central

    Drake, Henrik; Åström, Mats E.; Heim, Christine; Broman, Curt; Åström, Jan; Whitehouse, Martin; Ivarsson, Magnus; Siljeström, Sandra; Sjövall, Peter

    2015-01-01

    Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C13C as light as −69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to −125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane. PMID:25948095

  12. Perfusion and diffusion sensitive 13C stimulated-echo MRSI for metabolic imaging of cancer.

    PubMed

    Larson, Peder E Z; Hurd, Ralph E; Kerr, Adam B; Pauly, John M; Bok, Robert A; Kurhanewicz, John; Vigneron, Daniel B

    2013-06-01

    Metabolic imaging with hyperpolarized [1-(13)C]-pyruvate can rapidly probe tissue metabolic profiles in vivo and has been shown to provide cancer imaging biomarkers for tumor detection, progression, and response to therapy. This technique uses a bolus injection followed by imaging within 1-2 minutes. The observed metabolites include vascular components and their generation is also influenced by cellular transport. These factors complicate image interpretation, especially since [1-(13)C]lactate, a metabolic product that is a biomarker of cancer, is also produced by red blood cells. It would be valuable to understand the distribution of metabolites between the vasculature, interstitial space, and intracellular compartments. The purpose of this study was to better understand this compartmentalization by using a perfusion and diffusion-sensitive stimulated-echo acquisition mode (STEAM) MRSI acquisition method tailored to hyperpolarized substrates. Our results in mouse models showed that among metabolites, the injected substrate (13)C-pyruvate had the largest vascular fraction overall while (13)C-alanine had the smallest vascular fraction. We observed a larger vascular fraction of pyruvate and lactate in the kidneys and liver when compared to back muscle and prostate tumor tissue. Our data suggests that (13)C-lactate in prostate tumor tissue voxels was the most abundant labeled metabolite intracellularly. This was shown in STEAM images that highlighted abnormal cancer cell metabolism and suppressed vascular (13)C metabolite signals. PMID:23260391

  13. Development of a 13C-optimized 1.5-mm high temperature superconducting NMR probe

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Vijaykumar; Hooker, Jerris W.; Withers, Richard S.; Nast, Robert E.; Brey, William W.; Edison, Arthur S.

    2013-10-01

    We report a 1.5-mm NMR probe based on high temperature superconductors operating at 14.1 T optimized for 13C detection. The probe has a total sample volume of about 35 microliters (μL) with an active volume of 20 μL and provides exceptional mass sensitivity for 13C detection. The probe also has excellent 1H sensitivity and employs a 2H lock; 15N irradiation capability can be added in the future. The coils are cooled to about 20 K using a standard Agilent cryogenic refrigeration system, and the sample temperature is regulated near room temperature. The coil design considerations are discussed in detail. This probe is ideal for directly detected 13C NMR experiments for natural products chemistry and metabolomics applications, for which 35 μL is an optimal sample volume. The outstanding 13C sensitivity of this probe allowed us to directly determine the 13C connectivity on 1.1 mg of natural abundance histidine using an INADEQUATE experiment. We demonstrated the utility of this probe for 13C-based metabolomics using a synthetic mixture of common natural abundance metabolites whose concentrations ranged from 1 to 5 mM (40-200 nmol).

  14. R-Matrix Analysis of the 13C(α,n)16O Reaction

    NASA Astrophysics Data System (ADS)

    Kock, Arthur; Rogachev, Grigory

    2015-10-01

    The 13C(α,n)16O reaction plays a crucial role in the main s-process occurring in low-mass thermally-pulsing asymptotic giant branch (TP-AGB) stars, which produces about half of all nuclei heavier than iron. However, direct measurements of this reaction cross section near the Gamow-peak energy are currently not possible due to very small reaction cross sections. Additionally, available cross-section data at higher energy have some inconsistencies, leading to significant uncertainties in low energy extrapolations. A global R-matrix fit was conducted, using all available data for the 13C(α,n)16O, 13C(α, α)13C, and 16O(n,n)16O reactions. Of particular importance was the inclusion of the fixed ANC for the 1 / 2 + state at 6 . 356 MeV in 17O, which was measured recently using the sub-Coulomb α-transfer reaction, as well as the new 13C+ α elastic-scattering data measured in the low-energy region 1 . 6 - 3 . 8 MeV. Important constraining information on various resonances was found, and the uncertainty for the astrophysical 13C(α,n)16O reaction rate was dramatically reduced. Much work on the analysis was done by A. K. Nurmukhanbetova from National Laboratory Astana in Astana, Kazakhstan.

  15. 13C-labelled microdialysis studies of cerebral metabolism in TBI patients☆

    PubMed Central

    Carpenter, Keri L.H.; Jalloh, Ibrahim; Gallagher, Clare N.; Grice, Peter; Howe, Duncan J.; Mason, Andrew; Timofeev, Ivan; Helmy, Adel; Murphy, Michael P.; Menon, David K.; Kirkpatrick, Peter J.; Carpenter, T. Adrian; Sutherland, Garnette R.; Pickard, John D.; Hutchinson, Peter J.

    2014-01-01

    Human brain chemistry is incompletely understood and better methodologies are needed. Traumatic brain injury (TBI) causes metabolic perturbations, one result of which includes increased brain lactate levels. Attention has largely focussed on glycolysis, whereby glucose is converted to pyruvate and lactate, and is proposed to act as an energy source by feeding into neurons’ tricarboxylic acid (TCA) cycle, generating ATP. Also reportedly upregulated by TBI is the pentose phosphate pathway (PPP) that does not generate ATP but produces various molecules that are putatively neuroprotective, antioxidant and reparative, in addition to lactate among the end products. We have developed a novel combination of 13C-labelled cerebral microdialysis both to deliver 13C-labelled substrates into brains of TBI patients and recover the 13C-labelled metabolites, with high-resolution 13C NMR analysis of the microdialysates. This methodology has enabled us to achieve the first direct demonstration in humans that the brain can utilise lactate via the TCA cycle. We are currently using this methodology to make the first direct comparison of glycolysis and the PPP in human brain. In this article, we consider the application of 13C-labelled cerebral microdialysis for studying brain energy metabolism in patients. We set this methodology within the context of metabolic pathways in the brain, and 13C research modalities addressing them. PMID:24361470

  16. (13) C Breath Tests Are Feasible in Patients With Extracorporeal Membrane Oxygenation Devices.

    PubMed

    Bednarsch, Jan; Menk, Mario; Malinowski, Maciej; Weber-Carstens, Steffen; Pratschke, Johann; Stockmann, Martin

    2016-07-01

    Temporary extracorporeal membrane oxygenation (ECMO) has been established as an essential part of therapy in patients with pulmonary or cardiac failure. As physiological gaseous exchange is artificially altered in this patient group, it is debatable whether a (13) C-breath test can be carried out. In this proof of technical feasibility report, we assess the viability of the (13) C-breath test LiMAx (maximum liver function capacity) in patients on ECMO therapy. All breath probes for the test device were obtained directly via the membrane oxygenator. Data of four patients receiving liver function assessment with the (13) C-breath test LiMAx while having ECMO therapy were analyzed. All results were compared with validated scenarios of the testing procedures. The LiMAx test could successfully be carried out in every case without changing ECMO settings. Clinical course of the patients ranging from multiorgan failure to no sign of liver insufficiency was in accordance with the results of the LiMAx liver function test. The (13) C-breath test is technically feasible in the context of ECMO. Further evaluation of (13) C-breath test in general would be worthwhile. The LiMAx test as a (13) C-breath test accessing liver function might be of particular predictive interest if patients with ECMO therapy develop multiorgan failure. PMID:26527580

  17. Development of a 13C-Optimized 1.5-mm High Temperature Superconducting NMR Probe

    PubMed Central

    Ramaswamy, Vijaykumar; Hooker, Jerris W.; Withers, Richard S.; Nast, Robert E.; Brey, William W.; Edison, Arthur S.

    2013-01-01

    We report a 1.5-mm NMR probe based on high temperature superconductors operating at 14.1 T optimized for 13C detection. The probe has a total sample volume of about 35 microliters (μL) with an active volume of 20 μL and provides exceptional mass sensitivity for 13C detection. The probe also has excellent 1H sensitivity and employs a 2H channel lock; 15N irradiation capability can be added in the future. The coils are cooled to about 20 K using a standard Agilent cryogenic refrigeration system, and the sample temperature is regulated near room temperature. The coil design considerations are discussed in detail. This probe is ideal for directly detected 13C NMR experiments for natural products chemistry and metabolomics applications, for which 35 μL is an optimal sample volume. The outstanding 13C sensitivity of this probe allowed us to directly determine the 13C connectivity on 1.1 mg of natural abundance histidine using an INADEQUATE experiment. We demonstrated the utility of this probe for 13C-based metabolomics using a synthetic mixture of common natural abundance metabolites whose concentrations ranged from 1 to 5 mM (40 to 200 nmol). PMID:23969086

  18. [2,4-13C2]-β-Hydroxybutyrate Metabolism in Human Brain

    PubMed Central

    Pan, Jullie W.; de Graaf, Robin A.; Petersen, Kitt F.; Shulman, Gerald I.; Hetherington, Hoby P.; Rothman, Douglas L.

    2010-01-01

    Summary Infusions of [2,4-13C2]-β-hydroxybutyrate and 1H–13C polarization transfer spectroscopy were used in normal human subjects to detect the entry and metabolism of β-hydroxybutyrate in the brain. During the 2-hour infusion study, 13C label was detectable in the β-hydroxybutyrate resonance positions and in the amino acid pools of glutamate, glutamine, and aspartate. With a plasma concentration of 2.25 ± 0.24 mmol/L (four volunteers), the apparent tissue β-hydroxybutyrate concentration reached 0.18 ± 0.06 mmol/L during the last 20 minutes of the study. The relative fractional enrichment of 13C-4-glutamate labeling was 6.78 ± 1.71%, whereas 13C-4-glutamine was 5.68 ± 1.84%. Steady-state modeling of the 13C label distribution in glutamate and glutamine suggests that, under these conditions, the consumption of the β-hydroxybutyrate is predominantly neuronal, used at a rate of 0.032 ± 0.009 mmol · kg−1 · min−1, and accounts for 6.4 ± 1.6% of total acetyl coenzyme A oxidation. These results are consistent with minimal accumulation of cerebral ketones with rapid utilization, implying blood–brain barrier control of ketone oxidation in the nonfasted adult human brain. PMID:12142574

  19. [2,4-13 C2 ]-beta-Hydroxybutyrate metabolism in human brain.

    PubMed

    Pan, Jullie W; de Graaf, Robin A; Petersen, Kitt F; Shulman, Gerald I; Hetherington, Hoby P; Rothman, Douglas L

    2002-07-01

    Infusions of [2,4-13C2]-beta-hydroxybutyrate and 1H-13C polarization transfer spectroscopy were used in normal human subjects to detect the entry and metabolism of beta-hydroxybutyrate in the brain. During the 2-hour infusion study, 13C label was detectable in the beta-hydroxybutyrate resonance positions and in the amino acid pools of glutamate, glutamine, and aspartate. With a plasma concentration of 2.25 +/- 0.24 mmol/L (four volunteers), the apparent tissue beta-hydroxybutyrate concentration reached 0.18 +/- 0.06 mmol/L during the last 20 minutes of the study. The relative fractional e