Science.gov

Sample records for 15n natural abundance

  1. Natural-abundance 15N NMR studies of Turkey ovomucoid third domain. Assignment of peptide 15N resonances to the residues at the reactive site region via proton-detected multiple-quantum coherence

    NASA Astrophysics Data System (ADS)

    Ortiz-Polo, Gilberto; Krishnamoorthi, R.; Markley, John L.; Live, David H.; Davis, Donald G.; Cowburn, David

    Heteronuclear two-dimensional 1H{ 15N} multiple-quantum (MQ) spectroscopy has been applied to a protein sample at natural abundance: ovomucoid third domain from turkey ( Meleagris gallopavo), a serine proteinase inhibitor of 56 amino acid residues. Peptide amide 1H NMR assignments obtained by two-dimensional 1H{ 1H} NMR methods (R. Krishnamoorthi and J. L. Markley, unpublished data) led to identification of the corresponding 1H{ 15N} MQ coherence cross peaks. From these, 15N NMR chemical shifts were determined for several specific backbone amide groups of amino acid residues located around the reactive site region of the inhibitor. The results suggest that amide 15N chemical shifts, which are readily obtained in this way, may serve as sensitive probes for conformational studies of proteins.

  2. [Responses of Soil and Plant 15N Natural Abundance to Long-term N Addition in an N-Saturated Pinus massoniana Forest in Southwest China].

    PubMed

    Liu, Wen-jing; Kang, Rong-hua; Zhang, Ting; Zhu, Jing; Duan, Lei

    2015-08-01

    Increasing N deposition in China will possibly cause N saturation of forest ecosystem, further resulting in a series of serious environmental problems. In order to explore the response of forest ecosystem to N deposition in China, and further evaluate and predict the N status of ecosystem, the 15N natural abundance (delta 15N) of soil and plants was measured in a typical Masson pine (Pinus massoniana) forest in southwest China to examine the potential use of delta 15N enrichment factor (epsilon(p/s)) as an effective indicator of N status. Long-term high N addition could significantly increase delta 15N of soil and plants, which was suggested by an on-going N fertilizing experiment with NH4NO3 or NaNO3 for 7 years. Meanwhile, delta 15N of soil and plants under NH, deposition was significantly higher than that under NO- deposition, suggesting different responses of ecosystem to different N-forms of deposition. The "N enrichment factor (epsilon(p/s)) had positive correlations with N deposition, N nitrification, and N leaching in the soil water. Linear correlation between "N enrichment factor and N deposition was found for all Masson pine forests investigated in this and previous studies in China, demonstrating that 15N enrichment factor could be used as an indicator of N status. The NH3 emission control should also be carried out accompanying with NOx emission control in the future, because NH4- deposition had significantly greater impact on the forest ecosystem than NO3- deposition with the same equivalence. PMID:26592030

  3. Natural 15N- and 13C-abundance as indicators of forest nitrogen status and soil carbon dynamics

    SciTech Connect

    Garten Jr, Charles T; Hanson, Paul J; Todd Jr, Donald E; Lu, Benwhea Bonnie; Brice, Deanne Jane

    2007-09-01

    This book highlights new and emerging uses of stable isotope analysis in a variety of ecological disciplines. While the use of natural abundance isotopes in ecological research is now relatively standard, new techniques and ways of interpreting patterns are developing rapidly. The second edition of this book provides a thorough, up-to-date examination of these methods of research. As part of the Ecological Methods and Concepts series which provides the latest information on experimental techniques in ecology, this book looks at a wide range of techniques that use natural abundance isotopes to: {sm_bullet} follow whole ecosystem element cycling {sm_bullet} understand processes of soil organic matter formation {sm_bullet} follow the movement of water in whole watersheds {sm_bullet} understand the effects of pollution in both terrestrial and aquatic environments {sm_bullet} study extreme systems such as hydrothermal vents {sm_bullet}follow migrating organisms In each case, the book explains the background to the methodology, looks at the underlying principles and assumptions, and outlines the potential limitations and pitfalls. Stable Isotopes in Ecology and Environmental Science is an ideal resource for both ecologists who are new to isotopic analysis, and more experienced isotope ecologists interested in innovative techniques and pioneering new uses.

  4. Natural abundances of 15N and 13C in leaves of some N2-fixing and non-N2-fixing trees and shrubs in Syria.

    PubMed

    Kurdali, F; Al-Shamma'a, M

    2009-09-01

    A survey study was conducted on man-made plantations located at two different areas in the arid region of Syria to determine the variations in natural abundances of the (15)N and (13)C isotopes in leaves of several woody legume and non-legume species, and to better understand the consequence of such variations on nitrogen fixation and carbon assimilation. In the first study area (non-saline soil), the delta(15)N values in four legume species (Acacia cyanophylla,-1.73 per thousand Acacia farnesiana,-0.55 per thousand Prosopis juliflora,-1.64 per thousand; and Medicago arborea,+1.6 \\textperthousand) and one actinorhizal plant (Elaeagnus angustifolia,-0.46 to-2.1 per thousand) were found to be close to that of the atmospheric value pointing to a major contribution of N(2) fixing in these species; whereas, delta(15)N values of the non-fixing plant species were highly positive. delta(13)C per thousand; in leaves of the C3 plants were found to be affected by plant species, ranging from a minimum of-28.67 per thousand; to a maximum of-23 per thousand. However, they were relatively similar within each plant species although they were grown at different sites. In the second study area (salt affected soil), a higher carbon discrimination value (Delta(13)C per thousand) was exhibited by P. juliflora, indicating that the latter is a salt tolerant species; however, its delta(15)N was highly positive (+7.03 per thousand) suggesting a negligible contribution of the fixed N(2). Hence, it was concluded that the enhancement of N(2) fixation might be achieved by selection of salt-tolerant Rhizobium strains. PMID:20183233

  5. NMR profiling of biomolecules at natural abundance using 2D 1H-15N and 1H-13C multiplicity-separated (MS) HSQC spectra

    NASA Astrophysics Data System (ADS)

    Chen, Kang; Freedberg, Darón I.; Keire, David A.

    2015-02-01

    2D NMR 1H-X (X = 15N or 13C) HSQC spectra contain cross-peaks for all XHn moieties. Multiplicity-edited1H-13C HSQC pulse sequences generate opposite signs between peaks of CH2 and CH/CH3 at a cost of lower signal-to-noise due to the 13C T2 relaxation during an additional 1/1JCH period. Such CHn-editing experiments are useful in assignment of chemical shifts and have been successfully applied to small molecules and small proteins (e.g. ubiquitin) dissolved in deuterated solvents where, generally, peak overlap is minimal. By contrast, for larger biomolecules, peak overlap in 2D HSQC spectra is unavoidable and peaks with opposite phases cancel each other out in the edited spectra. However, there is an increasing need for using NMR to profile biomolecules at natural abundance dissolved in water (e.g., protein therapeutics) where NMR experiments beyond 2D are impractical. Therefore, the existing 2D multiplicity-edited HSQC methods must be improved to acquire data on nuclei other than 13C (i.e.15N), to resolve more peaks, to reduce T2 losses and to accommodate water suppression approaches. To meet these needs, a multiplicity-separated1H-X HSQC (MS-HSQC) experiment was developed and tested on 500 and 700 MHz NMR spectrometers equipped with room temperature probes using RNase A (14 kDa) and retroviral capsid (26 kDa) proteins dissolved in 95% H2O/5% D2O. In this pulse sequence, the 1/1JXH editing-period is incorporated into the semi-constant time (semi-CT) X resonance chemical shift evolution period, which increases sensitivity, and importantly, the sum and the difference of the interleaved 1JXH-active and the 1JXH-inactive HSQC experiments yield two separate spectra for XH2 and XH/XH3. Furthermore we demonstrate improved water suppression using triple xyz-gradients instead of the more widely used z-gradient only water-suppression approach.

  6. Comparing the influence of wildfire and prescribed burns on watershed nitrogen biogeochemistry using 15N natural abundance in terrestrial and aquatic ecosystem components.

    PubMed

    Stephan, Kirsten; Kavanagh, Kathleen L; Koyama, Akihiro

    2015-01-01

    We evaluated differences in the effects of three low-severity spring prescribed burns and four wildfires on nitrogen (N) biogeochemistry in Rocky Mountain headwater watersheds. We compared paired (burned/unburned) watersheds of four wildfires and three spring prescribed burns for three growing seasons post-fire. To better understand fire effects on the entire watershed ecosystem, we measured N concentrations and ?15N in both the terrestrial and aquatic ecosystems components, i.e., soil, understory plants in upland and riparian areas, streamwater, and in-stream moss. In addition, we measured nitrate reductase activity in foliage of Spiraea betulifolia, a dominant understory species. We found increases of ?15N and N concentrations in both terrestrial and aquatic ecosystem N pools after wildfire, but responses were limited to terrestrial N pools after prescribed burns indicating that N transfer from terrestrial to aquatic ecosystem components did not occur in low-severity prescribed burns. Foliar ?15N differed between wildfire and prescribed burn sites; the ?15N of foliage of upland plants was enriched by 2.9 ‰ (difference between burned and unburned watersheds) in the first two years after wildfire, but only 1.3 ‰ after prescribed burns. In-stream moss ?15N in wildfire-burned watersheds was enriched by 1.3 ‰, but there was no response by moss in prescription-burned watersheds, mirroring patterns of streamwater nitrate concentrations. S. betulifolia showed significantly higher nitrate reductase activity two years after wildfires relative to corresponding unburned watersheds, but no such difference was found after prescribed burns. These responses are consistent with less altered N biogeochemistry after prescribed burns relative to wildfire. We concluded that ?15N values in terrestrial and aquatic plants and streamwater nitrate concentrations after fire can be useful indicators of the magnitude and duration of fire effects and the fate of post-fire available N. PMID:25885257

  7. Comparing the Influence of Wildfire and Prescribed Burns on Watershed Nitrogen Biogeochemistry Using 15N Natural Abundance in Terrestrial and Aquatic Ecosystem Components

    PubMed Central

    Stephan, Kirsten; Kavanagh, Kathleen L.; Koyama, Akihiro

    2015-01-01

    We evaluated differences in the effects of three low-severity spring prescribed burns and four wildfires on nitrogen (N) biogeochemistry in Rocky Mountain headwater watersheds. We compared paired (burned/unburned) watersheds of four wildfires and three spring prescribed burns for three growing seasons post-fire. To better understand fire effects on the entire watershed ecosystem, we measured N concentrations and ?15N in both the terrestrial and aquatic ecosystems components, i.e., soil, understory plants in upland and riparian areas, streamwater, and in-stream moss. In addition, we measured nitrate reductase activity in foliage of Spiraea betulifolia, a dominant understory species. We found increases of ?15N and N concentrations in both terrestrial and aquatic ecosystem N pools after wildfire, but responses were limited to terrestrial N pools after prescribed burns indicating that N transfer from terrestrial to aquatic ecosystem components did not occur in low-severity prescribed burns. Foliar ?15N differed between wildfire and prescribed burn sites; the ?15N of foliage of upland plants was enriched by 2.9 ‰ (difference between burned and unburned watersheds) in the first two years after wildfire, but only 1.3 ‰ after prescribed burns. In-stream moss ?15N in wildfire-burned watersheds was enriched by 1.3 ‰, but there was no response by moss in prescription-burned watersheds, mirroring patterns of streamwater nitrate concentrations. S. betulifolia showed significantly higher nitrate reductase activity two years after wildfires relative to corresponding unburned watersheds, but no such difference was found after prescribed burns. These responses are consistent with less altered N biogeochemistry after prescribed burns relative to wildfire. We concluded that ?15N values in terrestrial and aquatic plants and streamwater nitrate concentrations after fire can be useful indicators of the magnitude and duration of fire effects and the fate of post-fire available N. PMID:25885257

  8. Differences in animal 13C, 15N and D abundance between a polluted and an unpolluted coastal site: Likely indicators of sewage uptake by a marine food web

    NASA Astrophysics Data System (ADS)

    Rau, G. H.; Sweeney, R. E.; Kaplan, I. R.; Mearns, A. J.; Young, D. R.

    1981-12-01

    In comparing a control vs. a sewage-affected nearshore site off southern California, the natural relative abundances of 13C, 15N and D in Dover sole and Ridgeback prawn muscle were found to be significantly different. This between-site shift in animal isotope abundance is of the type expected if sewage organic materials were an important food source for animals in the latter site. Use of stable isotope natural abundance to trace the incorporation and movement of sewage-derived organics in marine food webs is suggested.

  9. Litterfall 15N Abundance Indicates Declining Soil N Availability in a Free Air CO2-Enrichment Experiment

    E-print Network

    Post, Wilfred M.

    Litterfall 15N Abundance Indicates Declining Soil N Availability in a Free Air CO2-Enrichment in different treatment rings at the free-air CO2 enrichment (FACE) experiment at Oak Ridge National Laboratory Abstract: Forest productivity increases in response to carbon dioxide (CO2) enrichment of the atmosphere

  10. 15N and 13C abundances in the Antartic Ocean with emphasis on the biogeochemical structure of the food web

    NASA Astrophysics Data System (ADS)

    Wada, Eitaro; Terazaki, Makoto; Kabaya, Yuko; Nemoto, Takahisa

    1987-06-01

    Distributions of ? 15N and ? 13C for biogenic substances in the Antarctic Ocean were investigated to construct a biogeochemical framework for assessing the Antarctic ecosystem. Phytoplankton exhibited particularly low ? 15N (0.5%) and 13C (-26.9%) values in pelagic plankton samples. High nitrate concentrations, and high PCO 2 in the surface waters on the southern side of the polar front and the resulting slow growth rate of phytoplankton under low light intensity are suggested as possible factors in causing the low isotopic compositions. Mean fractionation factors of 1.029 and 1.006 were estimated for photosynthetic carbon fixation and for the assimilation of inorganic nitrogeneous compounds (ammonium plus nitrate) during algal growth, respectively. Enrichment of 15N with increasing trophic level was confirmed for Antarctic ecosystems: ?15N animal% = 3.3 (trophic level -1) + ?5N algae, whereas 13C content did not increase in the same manner. Differences in lipid content among animals may be the main factor in causing this ? 13C anomaly. 15N and 13C abundance of sedimentary organic nitrogen differed from phytoplankton and settling particles. An exact mechanism for explaining the high ? 15N (around 5%) is not known. The very high ? 13C value of -20.5% at Sta. 3B may originate in ice algae that had grown under CO 2-limited conditions. Particles collected by sediment traps gave characteristically low ? 15N values (-3.0 to 0.9%), strongly suggesting a phytoplankton origin. The ? 15N and ? 13C values of settling material showed similar vertical profiles with depth which might arise from temporal variation of algal growth.

  11. Revision of the 15N(p,?)16O reaction rate and oxygen abundance in H-burning zones

    E-print Network

    A. Caciolli; C. Mazzocchi; V. Capogrosso; D. Bemmerer; C. Broggini; P. Corvisiero; H. Costantini; Z. Elekes; A. Formicola; Zs. Fulop; G. Gervino; A. Guglielmetti; C. Gustavino; Gy. Gyurky; G. Imbriani; M. Junker; A. Lemut; M. Marta; R. Menegazzo; S. Palmerini; P. Prati; V. Roca; C. Rolfs; C. Rossi Alvarez; E. Somorjai; O. Straniero; F. Strieder; F. Terrasi; H. P. Trautvetter; A. Vomiero

    2011-07-22

    The NO cycle takes place in the deepest layer of a H-burning core or shell, when the temperature exceeds T {\\simeq} 30 {\\cdot} 106 K. The O depletion observed in some globular cluster giant stars, always associated with a Na enhancement, may be due to either a deep mixing during the RGB (red giant branch) phase of the star or to the pollution of the primordial gas by an early population of massive AGB (asymptotic giant branch) stars, whose chemical composition was modified by the hot bottom burning. In both cases, the NO cycle is responsible for the O depletion. The activation of this cycle depends on the rate of the 15N(p,{\\gamma})16O reaction. A precise evaluation of this reaction rate at temperatures as low as experienced in H-burning zones in stellar interiors is mandatory to understand the observed O abundances. We present a new measurement of the 15N(p,{\\gamma})16O reaction performed at LUNA covering for the first time the center of mass energy range 70-370 keV, which corresponds to stellar temperatures between 65 {\\cdot} 106 K and 780 {\\cdot}106 K. This range includes the 15N(p,{\\gamma})16O Gamow-peak energy of explosive H-burning taking place in the external layer of a nova and the one of the hot bottom burning (HBB) nucleosynthesis occurring in massive AGB stars. With the present data, we are also able to confirm the result of the previous R-matrix extrapolation. In particular, in the temperature range of astrophysical interest, the new rate is about a factor of 2 smaller than reported in the widely adopted compilation of reaction rates (NACRE or CF88) and the uncertainty is now reduced down to the 10% level.

  12. Assessing denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction

    USGS Publications Warehouse

    Smith, R.L.; Böhlke, J.K.; Garabedian, S.P.; Revesz, K.M.; Yoshinari, T.

    2004-01-01

    Denitrification was measured within a nitrate-contaminated aquifer on Cape Cod, Massachusetts, using natural gradient tracer tests with 15N nitrate. The aquifer contained zones of relatively high concentrations of nitrite (up to 77 ??M) and nitrous oxide (up to 143 ??M) and has been the site of previous studies examining ground water denitrification using the acetylene block technique. Small-scale (15-24 m travel distance) tracer tests were conducted by injecting 15N nitrate and bromide as tracers into a depth interval that contained nitrate, nitrite, nitrous oxide, and excess nitrogen gas. The timing of the bromide breakthrough curves at down-gradient wells matched peaks in 15N abundance above background for nitrate, nitrite, nitrous oxide, and nitrogen gas after more than 40 days of travel. Results were simulated with a one-dimensional transport model using linked reaction kinetics for the individual steps of the denitrification reaction pathway. It was necessary to include within the model spatial variations in background concentrations of all nitrogen oxide species. The model indicated that nitrite production (0.036-0.047 ??mol N (L aquifer)-1 d -1) was faster than the subsequent denitrification steps (0.013-0.016 ??mol N (L aquifer)-1 d-1 for nitrous oxide and 0.013-0.020 ??mol N (L aquifer)-1 d-1 for nitrogen gas) and that the total rate of reaction was slower than indicated by both acetylene block tracer tests and laboratory incubations. The rate of nitrate removal by denitrification was much slower than the rate of transport, indicating that nitrate would migrate several kilometers down-gradient before being completely consumed.

  13. Nitrate reductase 15N discrimination in Arabidopsis thaliana, Zea mays, Aspergillus niger, Pichea angusta, and Escherichia coli

    PubMed Central

    Carlisle, Eli; Yarnes, Chris; Toney, Michael D.; Bloom, Arnold J.

    2014-01-01

    Stable 15N isotopes have been used to examine movement of nitrogen (N) through various pools of the global N cycle. A central reaction in the cycle involves the reduction of nitrate (NO?3) to nitrite (NO?2) catalyzed by nitrate reductase (NR). Discrimination against 15N by NR is a major determinant of isotopic differences among N pools. Here, we measured in vitro 15N discrimination by several NRs purified from plants, fungi, and a bacterium to determine the intrinsic 15N discrimination by the enzyme and to evaluate the validity of measurements made using 15N-enriched NO?3. Observed NR isotope discrimination ranged from 22 to 32‰ (kinetic isotope effects of 1.022–1.032) among the different isozymes at natural abundance 15N (0.37%). As the fractional 15N content of substrate NO?3 increased from natural abundance, the product 15N fraction deviated significantly from that expected based on substrate enrichment and 15N discrimination measured at natural abundance. Additionally, isotopic discrimination by denitrifying bacteria used to reduce NO?3 and NO?2 in some protocols became a greater source of error as 15N enrichment increased. We briefly discuss potential causes of the experimental artifacts with enriched 15N and recommend against the use of highly enriched 15N tracers to study N discrimination in plants or soils. PMID:25071800

  14. ? 15 N constraints on long-term nitrogen balances in temperate forests

    EPA Science Inventory

    Natural abundance ?15N of ecosystems integrates nitrogen (N) inputs and losses, and thus reflects factors that control the long-term development of ecosystem N balances. We here report N and carbon (C) content of forest vegetation and soils, and associated ?15N, across nine Doug...

  15. Nicotine, acetanilide and urea multi-level2H-,13C- and15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry

    USGS Publications Warehouse

    Schimmelmann, A.; Albertino, A.; Sauer, P.E.; Qi, H.; Molinie, R.; Mesnard, F.

    2009-01-01

    Accurate determinations of stable isotope ratios require a calibration using at least two reference materials with different isotopic compositions to anchor the isotopic scale and compensate for differences in machine slope. Ideally, the S values of these reference materials should bracket the isotopic range of samples with unknown S values. While the practice of analyzing two isotopically distinct reference materials is common for water (VSMOW-SLAP) and carbonates (NBS 19 and L-SVEC), the lack of widely available organic reference materials with distinct isotopic composition has hindered the practice when analyzing organic materials by elemental analysis/isotope ratio mass spectrometry (EA-IRMS). At present only L-glutamic acids USGS40 and USGS41 satisfy these requirements for ??13C and ??13N, with the limitation that L-glutamic acid is not suitable for analysis by gas chromatography (GC). We describe the development and quality testing of (i) four nicotine laboratory reference materials for on-line (i.e. continuous flow) hydrogen reductive gas chromatography-isotope ratio mass-spectrometry (GC-IRMS), (ii) five nicotines for oxidative C, N gas chromatography-combustion-isotope ratio mass-spectrometry (GC-C-IRMS, or GC-IRMS), and (iii) also three acetanilide and three urea reference materials for on-line oxidative EA-IRMS for C and N. Isotopic off-line calibration against international stable isotope measurement standards at Indiana University adhered to the 'principle of identical treatment'. The new reference materials cover the following isotopic ranges: ??2Hnicotine -162 to -45%o, ??13Cnicotine -30.05 to +7.72%, ?? 15Nnicotine -6.03 to +33.62%; ??15N acetanilide +1-18 to +40.57%; ??13Curea -34.13 to +11.71%, ??15Nurea +0.26 to +40.61% (recommended ?? values refer to calibration with NBS 19, L-SVEC, IAEA-N-1, and IAEA-N-2). Nicotines fill a gap as the first organic nitrogen stable isotope reference materials for GC-IRMS that are available with different ??13N values. Comparative ??13C and ??15N on-line EA-IRMS data from 14 volunteering laboratories document the usefulness and reliability of acetanilides and ureas as EA-IRMS reference materials.

  16. Food Resources of Stream Macronivertebrates Determined by Natural-Abundance stable C and N Isotopes and a 15N Tracer Addition

    SciTech Connect

    Mulholland, P. J.

    2000-01-01

    Trophic relationships were examined using natural-abundance {sup 13}C and {sup 15}N analyses and a {sup 15}N-tracer addition experiment in Walker Branch, a 1st-order forested stream in eastern Tennessee. In the {sup 15}N-tracer addition experiment, we added {sup 15}NH{sub 4} to stream water over a 6-wk period in early spring, and measured {sup 15}N:{sup 14}N ratios in different taxa and biomass compartments over distance and time. Samples collected from a station upstream from the {sup 15}N addition provided data on natural-abundance {sup 13}C:{sup 12}C and {sup 15}N:{sup 14}N ratios. The natural-abundance {sup 15}N analysis proved to be of limited value in identifying food resources of macroinvertebrates because {sup 15}N values were not greatly different among food resources. In general, the natural-abundance stable isotope approach was most useful for determining whether epilithon or detritus were important food resources for organisms that may use both (e.g., the snail Elimia clavaeformis), and to provide corroborative evidence of food resources of taxa for which the {sup 15}N tracer results were not definitive. The {sup 15}N tracer results showed that the mayflies Stenonema spp. and Baetis spp. assimilated primarily epilithon, although Baetis appeared to assimilate a portion of the epilithon (e.g., algal cells) with more rapid N turnover than the bulk pool sampled. Although Elimia did not reach isotopic equilibrium during the tracer experiment, application of a N-turnover model to the field data suggested that it assimilated a combination of epilithon and detritus. The amphipod Gammarus minus appeared to depend mostly on fine benthic organic matter (FBOM), and the coleopteran Anchytarsus bicolor on epixylon. The caddisfly Diplectrona modesta appeared to assimilate primarily a fast N-turnover portion of the FBOM pool, and Simuliidae a fast N-turnover component of the suspended particulate organic matter pool rather than the bulk pool sampled. Together, the natural-abundance stable C and N isotope analyses and the experimental {sup 15}N tracer approach proved to be very useful tools for identifying food resources in this stream ecosystem.

  17. Application of the 15N-Gas Flux method for measuring in situ N2 and N2O fluxes due to denitrification in natural and semi-natural terrestrial ecosystems and comparison with the acetylene inhibition technique

    NASA Astrophysics Data System (ADS)

    Sgouridis, F.; Ullah, S.; Stott, A.

    2015-08-01

    Soil denitrification is considered the most un-constrained process in the global N cycle due to uncertain in situ N2 flux measurements, particularly in natural and semi-natural terrestrial ecosystems. 15N tracer approaches can provide in situ measurements of both N2 and N2O simultaneously, but their use has been limited to fertilised agro-ecosystems due to the need for large 15N additions in order to detect 15N2 production against the high atmospheric N2. For 15N-N2 analyses, we have used an "in house" laboratory designed and manufactured N2 preparation instrument which can be interfaced to any commercial continuous flow isotope ratio mass spectrometer (CF-IRMS). The N2 prep unit has gas purification steps, a copper based reduction furnace, and allows the analysis of small gas injection volumes (4 ?L) for 15N-N2 analysis. For the analysis of N2O, an automated Tracegas Pre-concentrator (Isoprime Ltd) coupled to an IRMS was used to measure the 15N-N2O (4 mL gas injection volume). Consequently, the coefficient of variation for the determination of isotope ratios for N2 in air and in standard N2O (0.5 ppm) was better than 0.5 %. The 15N Gas-Flux method was adapted for application in natural and semi-natural land use types (peatlands, forests and grasslands) by lowering the 15N tracer application rate to 0.04-0.5 kg 15N ha-1. For our chamber design (volume / surface = 8:1) and a 20 h incubation period, the minimum detectable flux rates were 4 ?g N m-2 h-1 and 0.2 ng N m-2 h-1 for the N2 and N2O fluxes respectively. The N2 flux ranged between 2.4 and 416.6 ?g N m-2 h-1, and the grassland soils showed on average 3 and 14 times higher denitrification rates than the woodland and organic soils respectively. The N2O flux was on average 20 to 200 times lower than the N2 flux, while the denitrification product ratio (N2O/N2 + N2O) was low, ranging between 0.03 and 13 %. Total denitrification rates measured by the acetylene inhibition technique under the same field conditions correlated (r = 0.58) with the denitrification rates measured under the 15N Gas-Flux method but were underestimated by a factor of 4 and this was attributed to the incomplete inhibition of N2O reduction to N2 under relatively high soil moisture content. The results show that the 15N Gas-Flux method can be used for quantifying N2 and N2O production rates in natural terrestrial ecosystems, thus significantly improving our ability to constrain ecosystem N budgets.

  18. Vertical ?13C and ?15N changes during pedogenesis

    NASA Astrophysics Data System (ADS)

    Brunn, Melanie; Spielvogel, Sandra; Wells, Andrew; Condron, Leo; Oelmann, Yvonne

    2015-04-01

    The natural abundance of soil organic matter (SOM) stable C and N isotope ratios are subjected to vertical changes throughout the soil profile. This vertical distribution is a widely reported phenomenon across varieties of ecosystems and constitutes important insights of soil carbon cycling. In most ecosystems, SOM becomes enriched in heavy isotopes by several per mill in the first few centimeters of the topsoil. The enrichment of 13C in SOM with soil depth is attributed to biological and physical-chemical processes in soil e.g., plant physiological impacts, microbial decomposition, sorption and transport processes. Such vertical trends in 13C and 15N abundance have rarely been related to SOM composition during pedogenesis. The aims of our study were to investigate short and long-term ?13C and ?15N depth changes and their interrelations under progressing pedogenesis and ecosystem development. We sampled soils across the well studied fordune progradation Haast-chronosequence, a dune ridge system under super-humid climate at the West Coast of New Zealand's South Island (43° 53' S, 169° 3' E). Soils from 11 sites with five replicates each covered a time span of around 2870 yr of soil development (from Arenosol to Podzol). Vertical changes of ?13C and ?15N values of SOM were investigated in the organic layers and in 1-cm depth intervals of the upper 10 cm of the mineral soil. With increasing soil depth SOM became enriched in ?13C by 1.9 ± SE 0.1 o and in ?15N by 6.0 ± 0.4 ‰?Litter ?13C values slightly decreased with increasing soil age (r = -0.61; p = 0.00) likely due to less efficient assimilation linked to nutrient limitations. Fractionation processes during mycorrhizal transfer appeared to affect ?15N values in the litter. We found a strong decrease of ?15N in the early succession stages ? 300 yr B.P. (r = -0.95; p = 0.00). Positive relations of vertical 13C and 15N enrichment with soil age might be related to decomposition and appeared to be affected by a change of hydrology, nutrient limitations, secondary minerals and root impacts. The investigation of vertical changes of soil organic matter (SOM) stable isotope ratios provides the opportunity to detect combined processes that enhance our understanding of terrestrial ecosystem functioning and pedogenetic processes leading to stabilization/destabilization in soil and therefore addressing the soil's sink/source function.

  19. Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15N tracer field studies

    USGS Publications Warehouse

    Templer, P.H.; Mack, M.C.; Chapin, F. S., III; Christenson, L.M.; Compton, J.E.; Crook, H.D.; Currie, W.S.; Curtis, C.J.; Dail, D.B.; D'Antonio, C. M.; Emmett, B.A.; Epstein, H.E.; Goodale, C.L.; Gundersen, P.; Hobbie, S.E.; Holland, K.; Hooper, D.U.; Hungate, B.A.; Lamontagne, S.; Nadelhoffer, K.J.; Osenberg, C.W.; Perakis, S.S.; Schleppi, P.; Schimel, J.; Schmidt, I.K.; Sommerkorn, M.; Spoelstra, J.; Tietema, A.; Wessel, W.W.; Zak, D.R.

    2012-01-01

    Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3–18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C: N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N·ha-1·yr-1 above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.

  20. Relative Magnitude and Controls of in Situ N2 and N2O Fluxes due to Denitrification in Natural and Seminatural Terrestrial Ecosystems Using (15)N Tracers.

    PubMed

    Sgouridis, Fotis; Ullah, Sami

    2015-12-15

    Denitrification is the most uncertain component of the nitrogen (N) cycle, hampering our ability to assess its contribution to reactive N (Nr) removal. This uncertainty emanates from the difficulty in measuring in situ soil N2 production and from the high spatiotemporal variability of the process itself. In situ denitrification was measured monthly between April 2013 and October 2014 in natural (organic and forest) and seminatural ecosystems (semi-improved and improved grasslands) in two UK catchments. Using the (15)N-gas flux method with low additions of (15)NO3(-) tracer, a minimum detectable flux rate of 4 ?g N m(-2) h(-1) and 0.2 ng N m(-2) h(-1) for N2 and N2O, respectively, was achieved. Denitrification rates were lower in organic and forest (8 and 10 kg N ha(-1) y(-1), respectively) than in semi-improved and improved grassland soils (13 and 25 kg N ha(-1) y(-1), respectively). The ratio of N2O/N2 + N2O was low and ranged from <1% to 7% across the sites. Variation in denitrification was driven by differences in soil respiration, nitrate, C:N ratio, bulk density, moisture, and pH across the sites. Overall, the contribution of denitrification to Nr removal in natural ecosystems was ?50% of the annual atmospheric Nr deposition, making these ecosystems vulnerable to chronic N saturation. PMID:26509488

  1. Chemical method for nitrogen isotopic analysis of ammonium at natural abundance.

    PubMed

    Liu, Dongwei; Fang, Yunting; Tu, Ying; Pan, Yuepeng

    2014-04-15

    We report a new chemical method to determine the (15)N natural abundance (?(15)N) for ammonium (NH4(+)) in freshwater (e.g., precipitation) and soil KCl extract. This method is based on the isotopic analysis of nitrous oxide (N2O). Ammonium is initially oxidized to nitrite (NO2(-)) by hypobromite (BrO(-)) using previously established procedures. NO2(-) is then quantitatively converted into N2O by hydroxylamine (NH2OH) under strongly acid conditions. The produced N2O is analyzed by a commercially available purge and cryogenic trap system coupled to an isotope ratio mass spectrometer (PT-IRMS). On the basis of a typical analysis size of 4 mL, the standard deviation of ?(15)N measurements is less than 0.3‰ and often better than 0.1‰ (3 to 5 replicates). Compared to previous methods, the technique here has several advantages and the potential to be used as a routine method for (15)N/(14)N analysis of NH4(+): (1) substantially simplified preparation procedures and reduced preparation time particularly compared to the methods in which diffusion or distillation is involved since all reactions occur in the same vial and separation of NH4(+) from solution is not required; (2) more suitability for low volume samples including those with low N concentration, having a blank size of 0.6 to 2 nmol; (3) elimination of the use of extremely toxic reagents (e.g., HN3) and/or the use of specialized denitrifying bacterial cultures which may be impractical for many laboratories. PMID:24654992

  2. Stem injection of 15N–NH4NO3 into mature Sitka spruce (Picea sitchensis)

    PubMed Central

    Nair, Richard; Weatherall, Andrew; Perks, Mike; Mencuccini, Maurizio

    2014-01-01

    Stem injection techniques can be used to introduce 15N into trees to overcome a low variation in natural abundance and label biomass with a distinct 15N signature, but have tended to target small and young trees, of a variety of species, with little replication. We injected 98 atom% 15N ammonium nitrate (NH4NO3) solution into 13 mature, 9- to 13-m tall edge-profile Sitka spruce trees in order to produce a large quantity of labelled litter, examining the distribution of the isotope throughout the canopy after felling in terms of both total abundance of 15N and relative distribution of the isotope throughout individual trees. Using a simple mass balance of the canopy alone, based on observed total needle biomass and modelled branch biomass, all of the isotope injected was accounted for, evenly split between needles and branches, but with a high degree of variability both within individual trees, and among trees. Both 15N abundance and relative within-canopy distribution were biased towards the upper and middle crown in foliage. Recovery of the label in branches was much more variable than in needles, possibly due to differences in nitrogen allocation for both growth and storage, which differ seasonally between foliage and woody biomass. PMID:25335951

  3. Stem injection of 15N-NH4NO3 into mature Sitka spruce (Picea sitchensis).

    PubMed

    Nair, Richard; Weatherall, Andrew; Perks, Mike; Mencuccini, Maurizio

    2014-10-01

    Stem injection techniques can be used to introduce (15)N into trees to overcome a low variation in natural abundance and label biomass with a distinct (15)N signature, but have tended to target small and young trees, of a variety of species, with little replication. We injected 98 atom% (15)N ammonium nitrate (NH4NO3) solution into 13 mature, 9- to 13-m tall edge-profile Sitka spruce trees in order to produce a large quantity of labelled litter, examining the distribution of the isotope throughout the canopy after felling in terms of both total abundance of (15)N and relative distribution of the isotope throughout individual trees. Using a simple mass balance of the canopy alone, based on observed total needle biomass and modelled branch biomass, all of the isotope injected was accounted for, evenly split between needles and branches, but with a high degree of variability both within individual trees, and among trees. Both (15)N abundance and relative within-canopy distribution were biased towards the upper and middle crown in foliage. Recovery of the label in branches was much more variable than in needles, possibly due to differences in nitrogen allocation for both growth and storage, which differ seasonally between foliage and woody biomass. PMID:25335951

  4. Long-term 15N tracking from biological N fixation across different plant and humus components of the boreal forest

    NASA Astrophysics Data System (ADS)

    Arroniz-Crespo, Maria; Jones, David L.; Zackrisson, Olle; Nilsson, Marie-Charlotte; DeLuca, Thomas H.

    2014-05-01

    Biological N2 fixation by cyanobacteria associated with feather mosses is an important cog in the nitrogen (N) cycle of boreal forests; still, our understanding of the turnover and fate of N fixed by this association remains greatly incomplete. The 15N signature of plants and soil serves as a powerful tool to explore N dynamics in forest ecosystems. In particular, in the present study we aimed to investigate the contribution of N2 fixation to ?15N signatures of plants and humus component of the boreal forest. Here we present results from a long-term (7 years) tacking of labelled 15N2 across the humus layer, seedlings of the tree species Pinus sylvestris, two common dwarf shrub species (Empetrum hermaphroditum and Vaccinium vitis-idaea) and the feather moss Pleurozium schreibery. The enriched experiment was conducted in 2005 in a natural boreal forest in northern Sweden. Two different treatments (10% 15N2 headspace enrichment and control) were setup in nine different plots (0.5 x 0.5 m) within the forest. We observed a significant reduction of ?15N signature of the 15N-enriched moss that could be explained by a growth dilution effect. Nevertheless, after 5 years since 15N2 enrichment some of the label 15N was still detected on the moss and in particular in the dead tissue. We could not detect a clear transfer of the labelled 15N2 from the moss-cyanobacteria system to other components of the ecosystem. However, we found consistence relationship through time between increments of ?15N signature of some of the forest components in plots which exhibited higher N fixation rates in the moss. In particular, changes in natural abundance ?15N that could be associated with N fixation were more apparent in the humus layer, the dwarf shrub Vaccinium vitis-idaea and the pine seedlings when comparing across plots and years.

  5. QUANTITATIVE 15N NMR SPECTROSCOPY

    EPA Science Inventory

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

  6. Differential incorporation of natural spawners vs. artificially planted salmon carcasses in a stream food web: Evidence from delta 15N of juvenile coho salmon

    EPA Science Inventory

    Placement of salmon carcasses is a common restoration technique in Oregon and Washington streams, with the goal of improving food resources and productivity of juvenile salmon. To explore the effectiveness of this restoration technique, we measured the ?15N of juvenile coho salmo...

  7. The Nature of Dark Energy from deep Cluster Abundance

    E-print Network

    P. Solevi; R. Mainini; S. A. Bonometto

    2004-12-02

    We show that using the redshift dependence of the deep cluster abundance to detect the nature of Dark Energy is a serious challenge. We compare the expected differences between flat LCDM models, with different Omega_mo, with the difference between LCDM and dynamical DE models. In the former case, cluster abundances in comoving volume and geometrical factors act in the same direction, yielding a significant difference between the expected angular densities. On the contrary, when we keep a constant Omega_mo and change the DE nature,abundances in comoving volume and geometrical factors act in the opposite direction, so that the expected differences in angular densities reduce to small factors.

  8. Highly 15N-Enriched Chondritic Clasts in the Isheyevo Meteorite

    SciTech Connect

    Bonal, L; Huss, G R; Krot, A N; Nagashima, K; Ishii, H A; Bradley, J P; Hutcheon, I D

    2009-01-14

    The metal-rich carbonaceous chondrites (CB and CH) have the highest whole-rock {sup 15}N enrichment ({delta}{sup 15}N up to +1500{per_thousand}), similar to {delta}{sup 15}N values reported in micron-sized regions (hotspots) of Interplanetary Dust Particles (IDPs) of possibly cometary origin and fine-grained matrices of unmetamorphosed chondrites. These {sup 15}N-rich hotspots are commonly attributed to low-temperature ion-molecule reactions in the protosolar molecular cloud or in the outer part of the protoplanetary disk. The nature of the whole-rock {sup 15}N enrichment of the metal-rich chondrites is not understood. We report a discovery of a unique type of primitive chondritic clasts in the CH/CB-like meteorite Isheyevo, which provides important constraints on the origin of {sup 15}N anomaly in metal-rich chondrites and nitrogen-isotope fractionation in the Solar System. These clasts contain tiny chondrules and refractory inclusions (5-15 {micro}m in size), and abundant ferromagnesian chondrule fragments (1-50 {micro}m in size) embedded in the partly hydrated, fine-grained matrix material composed of olivines, pyroxenes, poorly-organized aromatic organics, phyllosilicates and other hydrous phases. The mineralogy and oxygen isotope compositions of chondrules and refractory inclusions in the clasts are similar to those in the Isheyevo host, suggesting formation at similar heliocentric distances. In contrast to the previously known extraterrestrial samples, the fine-grained material in the clasts is highly and rather uniformly enriched in {sup 15}N, with bulk {delta}{sup 15}N values ranging between +1000 and +1300{per_thousand}; the {delta}{sup 15}N values in rare hotspots range from +1400 to +4000{per_thousand}. Since fine-grained matrices in the lithic clasts are the only component containing thermally unprocessed (during CAI and chondrule formation or during impact melting) materials that accreted into the metal rich chondrite parent body(ies), the {sup 15}N-enriched clasts as present in Isheyevo probably represent the major primordial carrier of {sup 15}N anomaly in these meteorites. The rather uniform and very high bulk {sup 15}N enrichment of the Isheyevo chondritic clasts, in contrast to rare hotspots of possibly molecular cloud origin in cometary IDPs, indicates that the nitrogen-isotope fractionation recorded by these clasts, containing abundant solar system materials, could have resulted from processes in the protoplanetary disk (e.g., ultraviolet photodissociation of {sup 15}N{sub 2} followed by trapping {sup 15}N atoms into NH-bearing ices) rather than solely by inheritance from the protosolar molecular cloud. If this is the case, the unique {sup 15}N-rich signature of the clasts could have resulted from nitrogen-isotope fractionation in cold and optically thin parts of the protoplanetary disk.

  9. C natural abundance of two mycoheterotrophic and a putative partially

    E-print Network

    are significantly more enriched in 13 C than co-occurring autotrophic plants but lack significant 15 N enrichment plants and can grow fully autotrophically under controlled conditions. · Our results suggest in 13 C and 15 N compared with autotrophic understorey plants New PhytologistResearch 590 New

  10. Human and climate impact on ¹?N natural abundance of plants and soils in high-mountain ecosystems: a short review and two examples from the Eastern Pamirs and Mt. Kilimanjaro.

    PubMed

    Zech, Michael; Bimüller, Carolin; Hemp, Andreas; Samimi, Cyrus; Broesike, Christina; Hörold, Claudia; Zech, Wolfgang

    2011-09-01

    Population pressure increasingly endangers high-mountain ecosystems such as the pastures in the Eastern Pamirs and the mountain forests on Mt. Kilimanjaro. At the same time, these ecosystems constitute the economic basis for millions of people living there. In our study, we, therefore, aimed at characterising the land-use effects on soil degradation and N-cycling by determining the natural abundance of (15)N. A short review displays that ?(15)N of plant-soil systems may often serve as an integrated indicator of N-cycles with more positive ?(15)N values pointing towards N-losses. Results for the high-mountain pastures in the Eastern Pamirs show that intensively grazed pastures are significantly enriched in (15)N compared to the less-exploited pastures by 3.5 ‰, on average. This can be attributed to soil organic matter degradation, volatile nitrogen losses, nitrogen leaching and a general opening of the N-cycle. Similarly, the intensively degraded savanna soils, the cultivated soils and the soils under disturbed forests on the foothill of Mt. Kilimanjaro reveal very positive ?(15)N values around 6.5 ‰. In contrast, the undisturbed forest soils in the montane zone are more depleted in (15)N, indicating that here the N-cycle is relatively closed. However, significantly higher ?(15)N values characterise the upper montane forest zone at the transition to the subalpine zone. We suggest that this reflects N-losses by the recently monitored and climate change and antropogenically induced increasing fire frequency pushing the upper montane rainforest boundary rapidly downhill. Overall, we conclude that the analysis of the (15)N natural abundance in high-mountain ecosystems is a purposeful tool for detecting land-use- or climate change-induced soil degradation and N-cycle opening. PMID:21745030

  11. 13C/12C and 15N/14N Isotope Analysis to Characterize Natural Degradation of Atrazine: Evidence from Parent and Daughter Compound Values

    NASA Astrophysics Data System (ADS)

    Elsner, Martin; Meyer, Armin

    2013-04-01

    The mobile and still herbicidal metabolites desethylatrazine (DEA) and desisopropylatrazine (DIA) are frequently detected together with its parent compound atrazine (Atz) in the aquatic environment. Interpretation of their transformation state is often difficult with current methods, which are mainly measuring concentrations. Alternatively, compound specific isotope analyses (CSIA) has become a novel tool to detect degradation processes of contaminants in groundwater. The aim of our study was to investigate on the lab scale 13C/12C and 15N/14N isotope trends in parent and daughter compounds associated with different degradation scenarios of atrazine likely to occur in the environment. Thus atrazine was dealkylated with (i) permanganate and (ii) the bacterium Rhodococcus sp. NI86/21. In both transformations, 13C/12C ratios of atrazine increased strongly (epsilon carbon/permanganate = -4.6 ± 0.6 ‰ and epsilon carbon/Rhodoccoccus = -3.8 ± 0.2 ‰) whereas nitrogen isotope fractionation was small. 13C/12C ratios of DEA showed the following trends. (i) When DEA was formed as only product (Atz + permanganate) 13C/12C remained constant, close to the initial value of Atz. (ii) When DEA was formed together with deisopropylatrazine (biodegradation of Atz) 13C/12C increased, but only within 2‰. (iii) When DEA and DIA was further biodegraded, 13C/12C increased for both metabolites up to 9‰. Thus strong enrichment of 13C/12C in the metabolites in comparison to Atz can give strong testimony for further breakdown of the metabolite.

  12. N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

    USGS Publications Warehouse

    Thorn, K.A.; Cox, L.G.

    2009-01-01

    The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS 15N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by 15N NMR. Liquid state 15N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection (1H-15N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

  13. Monitoring the refinement of crystal structures with (15)N solid-state NMR shift tensor data.

    PubMed

    Kalakewich, Keyton; Iuliucci, Robbie; Mueller, Karl T; Eloranta, Harriet; Harper, James K

    2015-11-21

    The (15)N chemical shift tensor is shown to be extremely sensitive to lattice structure and a powerful metric for monitoring density functional theory refinements of crystal structures. These refinements include lattice effects and are applied here to five crystal structures. All structures improve based on a better agreement between experimental and calculated (15)N tensors, with an average improvement of 47.0 ppm. Structural improvement is further indicated by a decrease in forces on the atoms by 2-3 orders of magnitude and a greater similarity in atom positions to neutron diffraction structures. These refinements change bond lengths by more than the diffraction errors including adjustments to X-Y and X-H bonds (X, Y = C, N, and O) of 0.028 ± 0.002 Å and 0.144 ± 0.036 Å, respectively. The acquisition of (15)N tensors at natural abundance is challenging and this limitation is overcome by improved (1)H decoupling in the FIREMAT method. This decoupling dramatically narrows linewidths, improves signal-to-noise by up to 317%, and significantly improves the accuracy of measured tensors. A total of 39 tensors are measured with shifts distributed over a range of more than 400 ppm. Overall, experimental (15)N tensors are at least 5 times more sensitive to crystal structure than (13)C tensors due to nitrogen's greater polarizability and larger range of chemical shifts. PMID:26590548

  14. Monitoring the refinement of crystal structures with 15N solid-state NMR shift tensor data

    NASA Astrophysics Data System (ADS)

    Kalakewich, Keyton; Iuliucci, Robbie; Mueller, Karl T.; Eloranta, Harriet; Harper, James K.

    2015-11-01

    The 15N chemical shift tensor is shown to be extremely sensitive to lattice structure and a powerful metric for monitoring density functional theory refinements of crystal structures. These refinements include lattice effects and are applied here to five crystal structures. All structures improve based on a better agreement between experimental and calculated 15N tensors, with an average improvement of 47.0 ppm. Structural improvement is further indicated by a decrease in forces on the atoms by 2-3 orders of magnitude and a greater similarity in atom positions to neutron diffraction structures. These refinements change bond lengths by more than the diffraction errors including adjustments to X-Y and X-H bonds (X, Y = C, N, and O) of 0.028 ± 0.002 Å and 0.144 ± 0.036 Å, respectively. The acquisition of 15N tensors at natural abundance is challenging and this limitation is overcome by improved 1H decoupling in the FIREMAT method. This decoupling dramatically narrows linewidths, improves signal-to-noise by up to 317%, and significantly improves the accuracy of measured tensors. A total of 39 tensors are measured with shifts distributed over a range of more than 400 ppm. Overall, experimental 15N tensors are at least 5 times more sensitive to crystal structure than 13C tensors due to nitrogen's greater polarizability and larger range of chemical shifts.

  15. Chlorine-36 abundance in natural and synthetic perchlorate

    SciTech Connect

    Heikoop, Jeffrey M; Dale, M; Sturchio, Neil C; Caffee, M; Belosa, A D; Heraty, Jr., L J; Bohike, J K; Hatzinger, P B; Jackson, W A; Gu, B

    2009-01-01

    Perchlorate (ClO{sub 4}{sup -}) is ubiquitous in the environment. It occurs naturally as a product of atmospheric photochemical reactions, and is synthesized for military, aerospace, and industrial applications. Nitrate-enriched soils of the Atacama Desert (Chile) contain high concentrations of natural ClO{sub 4}{sup -}; nitrate produced from these soils has been exported worldwide since the mid-1800's for use in agriculture. The widespread introduction of synthetic and agricultural ClO{sub 4}{sup -} into the environment has complicated attempts to understand the geochemical cycle of ClO{sub 4}{sup -}. Natural ClO{sub 4}{sup -} samples from the southwestern United States have relatively high {sup 36}Cl abundances ({sup 36}Cl/Cl = 3,100 x 10{sup -15} to 28,800 x 10{sup -15}), compared with samples of synthetic ({sup 36}Cl/Cl = 0.0 x 10{sup -15} to 40 x 10{sup -15}) and Atacama Desert ({sup 36}Cl/Cl = 0.9 x 10{sup -15} to 590 x 10{sup -15}) ClO{sub 4}{sup -}. These data give a lower limit for the initial {sup 36}Cl abundance of natural ClO{sub 4}{sup -} and provide temporal and other constraints on its geochemical cycle.

  16. THE EFFECTS OF PARAMAGNETIC RELAXATION REAGENTS ON 15N SPIN RELAXATION AND THE USE OF GD(DPM)3 AS A NITROGEN-15 NUCLEAR MAGNETIC RESONANCE SPIN LABEL

    EPA Science Inventory

    Electron-nuclear relaxation times (T(1) sup e's) for (15)N and (13)C in natural abundance are measured for a series of amines of a wide range of pK(a)s using four paramagnetic relaxation reagents that are soluable in organic solutions. Cr(acac)3 and Cr(dpm)3 are seen to affect th...

  17. Stable isotope natural abundance of nitrous oxide emitted from Antarctic tundra soils: effects of sea animal excrement depositions.

    PubMed

    Zhu, Renbin; Liu, Yashu; Li, Xianglan; Sun, Jianjun; Xu, Hua; Sun, Liguang

    2008-11-01

    Nitrous oxide (N2O), a greenhouse gas, is mainly emitted from soils during the nitrification and denitrification processes. N2O stable isotope investigations can help to characterize the N2O sources and N2O production mechanisms. N2O isotope measurements have been conducted for different types of global terrestrial ecosystems. However, no isotopic data of N2O emitted from Antarctic tundra ecosystems have been reported although the coastal ice-free tundra around Antarctic continent is the largest sea animal colony on the global scale. Here, we report for the first time stable isotope composition of N2O emitted from Antarctic sea animal colonies (including penguin, seal and skua colonies) and normal tundra soils using in situ field observations and laboratory incubations, and we have analyzed the effects of sea animal excrement depositions on stable isotope natural abundance of N2O. For all the field sites, the soil-emitted N2O was 15N- and 18O-depleted compared with N2O in local ambient air. The mean delta values of the soil-emitted N2O were delta15N = -13.5 +/- 3.2 per thousand and delta18O = 26.2 +/- 1.4 per thousand for the penguin colony, delta15N = -11.5 +/- 5.1 per thousand and delta18O = 26.4 +/- 3.5 per thousand for the skua colony and delta15N = -18.9 +/- 0.7 per thousand and delta18O = 28.8 +/- 1.3 per thousand for the seal colony. In the soil incubations, the isotopic composition of N2O was measured under N2 and under ambient air conditions. The soils incubated under the ambient air emitted very little N2O (2.93 microg N2O--N kg(-1)). Under N2 conditions, much more N2O was formed (9.74 microg N2O--N kg(-1)), and the mean delta15N and delta18O values of N2O were -19.1 +/- 8.0 per thousand and 21.3 +/- 4.3 per thousand, respectively, from penguin colony soils, and -17.0 +/- 4.2 per thousand and 20.6 +/- 3.5 per thousand, respectively, from seal colony soils. The data from in situ field observations and laboratory experiments point to denitrification as the predominant N2O source from Antarctic sea animal colonies. PMID:18932270

  18. Novel labeling technique illustrates transfer of 15N2 from Sphagnum moss to vascular plants via diazotrophic nitrogen fixation

    NASA Astrophysics Data System (ADS)

    Thorp, N. R.; Vile, M. A.; Wieder, R.

    2013-12-01

    We used 15N2 gas to trace nitrogen (N) from biological N2-fixation to vascular plant uptake in an Alberta bog in order to determine if neighboring bog plants acquire recently fixed N from diazotrophs associating with Sphagnum mosses. Recent evidence indicates high rates of N2-fixation in Sphagnum mosses of Alberta bogs (Vile et al. 2013). Our previous work has shown that mosses can assimilate fixed N from associated diazotrophs as evidenced by the high N content of mosses despite minimal inputs from atmospheric deposition, retranslocation, and N mineralization. Therefore, the potential exists for vascular plants to obtain N from ';leaky' tissues of live mosses, however, this phenomenon has not been tested previously. Here we document the potential for relatively rapid transfer to vascular plants of N fixed by Sphagnum moss-associated diazotrophs. We utilized the novel approach of incubating mosses in 15N2 to allow the process of diazotrophic N2-fixation to mechanistically provide the 15N label, which is subsequently transferred to Sphagnum mosses. The potential for vascular bog natives to tap this N was assessed by planting the vascular plants in the labeled moss. Sphagnum mosses (upper 3 cm of live plants) were incubated in the presence of 98 atom % 15N2 gas for 48 hours. Two vascular plants common to Alberta bogs; Picea mariana and Vaccinium oxycoccus were then placed in the labeled mosses, where the mosses served as the substrate. Tissue samples from these plants were collected at three time points during the incubation; prior to 15N2 exposure (to determine natural abundance 15N), and at one and two months after 15N2 exposure. Roots and leaves were separated and run separately on a mass spectrometer to determine 15N concentrations. Sphagnum moss capitula obtained N from N2-fixation (?15N of -2.43 × 0.40, 122.76 × 23.78, 224.92 × 68.37, 143.74 × 54.38 prior to, immediately after, and at 1 and 2 months after exposure to 15N2, respectively). Nitrogen was transferred to P. mariana roots (mean ?15N at 1 and 2 months of 15.26 × 3.30 and 16.19 × 1.21) more than shoots (mean ?15N at 1 and 2 months of 6.57 × 0.52 and 4.67×0.17) (initial ?15N values of roots and shoots of 2.16 × 0.37 and 5.54 × 0.35, respectively). Nitrogen also was transferred to V. oxycoccos roots (?15N at 2 months of 21.46 × 3.61) more than shoots (?15N 2 months of -2.17 × 0.23) (initial ?15N values of roots and shoots of -6.41 × 0.21 and -6.85 × 0.15, respectively). A two-way ANOVA and Tukey's HSD verified that both vascular plants' roots were significantly enriched with 15N (P. mariana roots; p < 0.0001, V. oxycoccus roots; p < 0.0001) after 1 month. These results indicate that bog vascular plants may derive considerable nitrogen from biological N2-fixation taking place in Sphagnum moss capitula. The experiment was subsequently repeated in-situ.

  19. PARTITIONING THE RELATIVE INFLUENCE OF SOIL N, MYCORRHIZAE, AND FOLIAR N UPTAKE ON FOLIAR ?15N PATTERNS: CAN WE DETECT FOLIAR UPTAKE OF REACTIVE N?

    NASA Astrophysics Data System (ADS)

    Vallano, D.; Sparks, J. P.

    2009-12-01

    Vegetation is an important sink for atmospheric reactive N in N-limited systems and may be capable of incorporating reactive N compounds directly into leaves through the foliar uptake pathway. A proxy for atmospheric reactive N entering vegetation would be useful to estimate the impact of direct foliar N uptake on plant metabolism. Natural abundance foliar N isotopic composition (?15N) is a practical tool for this purpose because plant-available N sources often have different isotopic compositions. Current understanding of foliar ?15N suggests these values primarily represent the integration of soil ?15N, direct foliar N uptake, mycorrhizal fractionation, and within-plant fractionations. Using a potted plant mesocosm system, we estimated the influence of mycorrhizae on foliar ?15N patterns in red maple (Acer rubrum) seedlings along an N deposition gradient in New York State. We found that mycorrhizal associations altered foliar ?15N in red maple seedlings from 0.03 - 1.01‰ across sites. Along the same temporal and spatial scales, we examined the influence of soil ?15N, foliar N uptake, and mycorrhizae on foliar ?15N in adult stands of American beech (Fagus grandifolia), black birch (Betula lenta), red maple (A. rubrum), and red oak (Quercus rubra). Using multiple regression models, atmospheric NO2 concentration explained 0%, 69%, 23%, and 45% of the residual variation in foliar ?15N remaining in American beech, red maple, red oak, and black birch, respectively, after accounting for soil ?15N. Our results suggest that foliar ?15N may be used to estimate pollution-derived atmospheric reactive N entering vegetation via the foliar N uptake pathway.

  20. Elevated 15N/14N in particulate organic matter, zooplankton, and diatom frustule-bound nitrogen in the ice-covered water column of the Bering Sea eastern shelf

    NASA Astrophysics Data System (ADS)

    Morales, Laura V.; Granger, Julie; Chang, Bonnie X.; Prokopenko, Maria G.; Plessen, Birgit; Gradinger, Rolf; Sigman, Daniel M.

    2014-11-01

    We conducted a survey of the natural abundance 15N/14N ratio (?15N) of particulate organic matter (POM), diatom frustule-bound nitrogen (?15NDB), and zooplankton from water column material collected with net tows across the eastern Bering Sea shelf in late winter of 2007 and 2008, to investigate the N dynamics of primary and secondary production in relation to the presence of seasonal sea ice. The data reveal a pattern of increasing ?15N northward and eastward (POM: 2.1-14.7‰; frustule-bound N: 4.9-20.7‰; zooplankton: 6.4-18.0‰), with POM ?15N reaching ~9‰ higher than that of water-column nitrate. Higher ?15N in each of these plankton fractions was largely associated with stations covered by sea ice. POM ?15N collected concurrently from within sea ice was not sufficiently 15N-enriched to explain the elevated water-column values. Rather, the ?15N of water-column POM under sea ice appears to derive from the assimilation of ammonium released from shelf sediments. Water-column ammonium ?15N was between 28‰ and 63‰, most likely due to partial nitrification in the sediment and overlying water column. The high ?15N of this ammonium is effectively transmitted to phytoplankton under sea ice because light limitation from the ice cover delays the springtime nitrate assimilation that yields algal biomass with a lower ?15N. Despite this seasonal explanation, published ?15N data from sediment traps, summertime zooplankton, and surface sediment indicate that a shoreward and northward ?15N increase - albeit of a weaker magnitude - is perennial, suggesting that the ?15N of the total annual fixed N supply (including both ammonium and nitrate) also increases shoreward and northward. This requires that the partial nitrification of ammonium underlying the spatial pattern in ?15N is at least partly coupled to denitrification in the sediments that preferentially removes 14N, causing the total fixed N reservoir on the shelf to evolve toward higher ?15N. Shelf geometry and the consequent benthic-pelagic coupling of N cycling thus seem to underlie the spatial pattern in the mean annual ?15N of plankton, while sea-ice cover causes the high ?15N of ammonium on the shelf to be most strongly reflected by the production occurring in the winter and early spring. Our results provide a basis for tracing the geographic and seasonal origins and trophic transfer of N in the Bering shelf ecosystem.

  1. CHANGE IN NATURAL ABUNDANCE OF 15N AND ESTIMATION OF N LOSSES FROM DAIRY MANURE DURING STORAGE BY MASS BALANCE AND NITROGEN-TO-PHOSPHORUS RATIO

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The main objective was to evaluate methodologies to estimate N losses from stored dairy manure. Manure with high N (HN) and low N (LN) content was obtained from two groups of cows assigned diets of 17 and 15% CP (DM), respectively. Manure collected from the barn floor was diluted with water to 10% ...

  2. The Titan 14N/ 15N and 12C/ 13C isotopic ratios in HCN from Cassini/CIRS

    NASA Astrophysics Data System (ADS)

    Vinatier, Sandrine; Bézard, Bruno; Nixon, Conor A.

    2007-11-01

    We report the detection of H 13CN and HC 15N in mid-infrared spectra recorded by the Composite Infrared Spectrometer (CIRS) aboard Cassini, along with the determination of the 12C/ 13C and 14N/ 15N isotopic ratios. We analyzed two sets of limb spectra recorded near 13-15° S (Tb flyby) and 83° N (T4 flyby) at 0.5 cm -1 resolution. The spectral range 1210-1310 cm -1 was used to retrieve the temperature profile in the range 145-490 km at 13° S and 165-300 km at 83° N. These two temperature profiles were then incorporated in the atmospheric model to retrieve the abundance profile of H 12C 14N, H 13CN and HC 15N from their bands at 713, 706 and 711 cm -1, respectively. The HCN abundance profile was retrieved in the range 90-460 km at 15° S and 165-305 km at 83° N. There is no evidence for vertical variations of the isotopic ratios. Constraining the isotopic abundance profiles to be proportional to the HCN one, we find C12/C13=89-18+22 at 15° S, and 68-12+16 at 83° N, two values that are statistically consistent. A combination of these results yields a 12C/ 13C value equal to 75±12. This global result, as well as the 15° S one, envelop the value in Titan's methane ( 82.3±1) [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779-784] measured at 10° S and is slightly lower than the terrestrial inorganic standard value (89). The 14N/ 15N isotopic ratio is found equal to 56-13+16 at 15° S and 56-9+10 at 83° N. Combining the two values yields 14N/ 15N = 56 ± 8, which corresponds to an enrichment in 15N of about 4.9 compared with the terrestrial ratio. These results agree with the values obtained from previous ground-based millimeter observations [Hidayat, T., Marten, A., Bézard, B., Gautier, D., Owen, T., Matthews, H.E., Paubert, G., 1997. Icarus 126, 170-182; Marten, A., Hidayat, T., Biraud, Y., Moreno, R., 2002. Icarus 158, 532-544]. The 15N/ 14N ratio found in HCN is ˜3 times higher than in N 2 [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779-784], which implies a large fractionation process in the HCN photochemistry.

  3. Diversity and abundance of phosphonate biosynthetic genes in nature

    PubMed Central

    Yu, Xiaomin; Doroghazi, James R.; Janga, Sarath C.; Zhang, Jun Kai; Circello, Benjamin; Griffin, Benjamin M.; Labeda, David P.; Metcalf, William W.

    2013-01-01

    Phosphonates, molecules containing direct carbon–phosphorus bonds, compose a structurally diverse class of natural products with interesting and useful biological properties. Although their synthesis in protozoa was discovered more than 50 y ago, the extent and diversity of phosphonate production in nature remains poorly characterized. The rearrangement of phosphoenolpyruvate (PEP) to phosphonopyruvate, catalyzed by the enzyme PEP mutase (PepM), is shared by the vast majority of known phosphonate biosynthetic pathways. Thus, the pepM gene can be used as a molecular marker to examine the occurrence and abundance of phosphonate-producing organisms. Based on the presence of this gene, phosphonate biosynthesis is common in microbes, with ?5% of sequenced bacterial genomes and 7% of genome equivalents in metagenomic datasets carrying pepM homologs. Similarly, we detected the pepM gene in ?5% of random actinomycete isolates. The pepM-containing gene neighborhoods from 25 of these isolates were cloned, sequenced, and compared with those found in sequenced genomes. PEP mutase sequence conservation is strongly correlated with conservation of other nearby genes, suggesting that the diversity of phosphonate biosynthetic pathways can be predicted by examining PEP mutase diversity. We used this approach to estimate the range of phosphonate biosynthetic pathways in nature, revealing dozens of discrete groups in pepM amplicons from local soils, whereas hundreds were observed in metagenomic datasets. Collectively, our analyses show that phosphonate biosynthesis is both diverse and relatively common in nature, suggesting that the role of phosphonate molecules in the biosphere may be more important than is often recognized. PMID:24297932

  4. [superscript 15]N-[superscript 15]N Proton Assisted Recoupling in Magic Angle Spinning NMR

    E-print Network

    Lewandowski, Jozef R.

    We describe a new magic angle spinning (MAS) NMR experiment for obtaining [superscript 15]N?[superscript 15]N correlation spectra. The approach yields direct information about the secondary and tertiary structure of proteins, ...

  5. Natural-abundance 17O NMR of monosaccharides

    NASA Astrophysics Data System (ADS)

    Gerothanassis, Ioannis P.; Lauterwein, Jürgen; Sheppard, Norman

    Natural-abundance "high-resolution" 17O NMR spectra of D-glucose, D-mannose, D-galactose, and some methoxy derivatives of D-glucose were recorded in aqueous solution. The sensitivity and spectral resolution was improved by optimizing the accumulation and manipulation of data. The water solvent peak was suppressed through use of 17O-depleted water or displaced by addition of paramagnetic shift reagents. With Dy 3+ the 17O NMR spectrum of D-glucose remained unaltered; however, the water peak was shifted outside the carbohydrate spectral region. The 17O NMR resonances were assigned from earlier data for some specifically 17O-enriched monosaccharide derivatives. The anomeric hydroxyl resonances could also be located because of their exchange with the 17O-depleted water. Although the chemical shifts of the monosacharides generally parallel the sequence of chemical shifts for simple primary and secondary alcohols and substituted ethers, several exceptions were found and discussed in terms of steric and electrostatic repulsive forces between oxygens.

  6. ?15N as a Potential Paleoenvironmental Proxy for Nitrogen Loading in Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Black, H. D.; Andrus, C. F.; Rick, T.; Hines, A.

    2013-12-01

    Stable isotope analysis of Eastern Oyster (Crassostrea virginica) and other mollusk shells from archaeological sites is a useful means of acquiring paleoenvironmental data. Recently, nitrogen isotopes have been identified as a potential new proxy in these shells. ?15N content in mollusk shells is affected by numerous anthropogenic and natural influences and may be used as an environmental proxy for nitrogen loading conditions. Chesapeake Bay is well known for both historic and modern pollution problems from numerous anthropogenic sources, such as fertilizer runoff, sewage discharge, and densely populated land use and serves as an ideal study location for long-term nitrogen loading processes. Longer records of these processes may be recorded in abundant archaeological remains around the bay, however, little is known about the stability of ?15N and %N in shell material over recent geologic time. In this study, 90 archaeological C. virginica shells were collected by the Smithsonian Institution from the Rhode River Estuary within Chesapeake Bay and range in age from ~150 to 3200 years old. Twenty-two modern C. virginica shells were also collected from nearby beds in the bay. All shell samples were subsampled from the resilifer region of the calcitic shell using a hand-held micro drill and were analyzed using EA-IRMS analysis to determine the potential temporal variability of ?15N and %N as well as creating a baseline for ancient nitrogen conditions in the bay area. Modern POM water samples and C. virginica soft tissues were also analyzed in this study to determine the degree of seasonal variation of ?15N and %N in Chesapeake Bay.

  7. Protein Retention Assessment of Four Levels of Poultry By-Product Substitution of Fishmeal in Rainbow Trout (Oncorhynchus mykiss) Diets Using Stable Isotopes of Nitrogen (?15N) as Natural Tracers

    PubMed Central

    Badillo, Daniel; Herzka, Sharon Z.; Viana, Maria Teresa

    2014-01-01

    This is second part from an experiment where the nitrogen retention of poultry by-product meal (PBM) compared to fishmeal (FM) was evaluated using traditional indices. Here a quantitative method using stable isotope ratios of nitrogen (?15N values) as natural tracers of nitrogen incorporation into fish biomass is assessed. Juvenile rainbow trout (Oncorhynchus mykiss) were fed for 80 days on isotopically distinct diets in which 0, 33, 66 and 100% of FM as main protein source was replaced by PBM. The diets were isonitrogenous, isolipidic and similar in gross energy content. Fish in all treatments reached isotopic equilibrium by the end of the experiment. Two-source isotope mixing models that incorporated the isotopic composition of FM and PBM as well as that of formulated feeds, empirically derived trophic discrimination factors and the isotopic composition of fish that had reached isotopic equilibrium to the diets were used to obtain a quantitative estimate of the retention of each source of nitrogen. Fish fed the diets with 33 and 66% replacement of FM by PBM retained poultry by-product meal roughly in proportion to its level of inclusion in the diets, whereas no differences were detected in the protein efficiency ratio. Coupled with the similar biomass gain of fishes fed the different diets, our results support the inclusion of PBM as replacement for fishmeal in aquaculture feeds. A re-feeding experiment in which all fish were fed a diet of 100% FM for 28 days indicated isotopic turnover occurred very fast, providing further support for the potential of isotopic ratios as tracers of the retention of specific protein sources into fish tissues. Stable isotope analysis is a useful tool for studies that seek to obtain quantitative estimates of the retention of different protein sources. PMID:25226392

  8. Electron paramagnetic resonance of the N2V- defect in 15N -doped synthetic diamond

    NASA Astrophysics Data System (ADS)

    Green, B. L.; Dale, M. W.; Newton, M. E.; Fisher, D.

    2015-10-01

    Nitrogen is the dominant impurity in the majority of natural and synthetic diamonds, and the family of nitrogen vacancy-type (NnV ) defects are crucial in our understanding of defect dynamics in these diamonds. A significant gap is the lack of positive identification of N2V- , the dominant charge state of N2V in diamond that contains a significant concentration of electron donors. In this paper, we employ isotopically-enriched diamond to identify the EPR spectrum associated with 15N2V- and use the derived spin Hamiltonian parameters to identify 14N2V- in a natural isotopic abundance sample. The electronic wave function of the N2V- ground state and previous lack of identification is discussed. The N2V- EPR spectrum intensity is shown to correlate with the H2 optical absorption over an order of magnitude in concentration.

  9. Carbon and nitrogen biogeochemistry in the ocean: A study using stable isotope natural abundance

    NASA Technical Reports Server (NTRS)

    Rau, G. H.; Desmarais, David J.

    1985-01-01

    Determining the biogeochemical pathways traveled by carbon and nitrogen in the ocean is fundamental to the understanding of how the ocean participates in the cycling of these elements within the biosphere. Because biological production, metabolism, and respiration can significantly alter the natural abundance of C-13 and N-15, these abundances can provide important information about the nature of these biological processes and their variability in the marine environment. The research initially seeks to characterize the spatial and temporal patterns of stable isotope abundances in organic matter, and to relate these abundances to C and N biogeochemical processes within selected areas of the northeastern Pacific Ocean.

  10. Natural Abundance 14C Content of Dibutyl Phthalate (DBP) from Three Marine Algae

    PubMed Central

    Namikoshi, Michio; Fujiwara, Takeshi; Nishikawa, Teruaki; Ukai, Kazuyo

    2006-01-01

    Analysis of the natural abundance 14C content of dibutyl phthalate (DBP) from two edible brown algae, Undaria pinnatifida and Laminaria japonica, and a green alga, Ulva sp., revealed that the DBP was naturally produced. The natural abundance 14C content of di-(2-ethylhexyl) phthalate (DEHP) obtained from the same algae was about 50–80% of the standard sample and the 14C content of the petrochemical (industrial) products of DBP and DEHP were below the detection limit.

  11. Theoretical and experimental study of 15N NMR protonation shifts.

    PubMed

    Semenov, Valentin A; Samultsev, Dmitry O; Krivdin, Leonid B

    2015-06-01

    A combined theoretical and experimental study revealed that the nature of the upfield (shielding) protonation effect in 15N NMR originates in the change of the contribution of the sp(2)-hybridized nitrogen lone pair on protonation resulting in a marked shielding of nitrogen of about 100?ppm. On the contrary, for amine-type nitrogen, protonation of the nitrogen lone pair results in the deshielding protonation effect of about 25?ppm, so that the total deshielding protonation effect of about 10?ppm is due to the interplay of the contributions of adjacent natural bond orbitals. A versatile computational scheme for the calculation of 15N NMR chemical shifts of protonated nitrogen species and their neutral precursors is proposed at the density functional theory level taking into account solvent effects within the supermolecule solvation model. PMID:25891386

  12. Evaluating the source of streamwater nitrate using ?15N and ?18O in nitrate in two watersheds in New Hampshire, USA

    USGS Publications Warehouse

    Pardo, Linda H.; Kendall, Carol; Pett-Ridge, Jennifer; Chang, Cecily C.Y.

    2004-01-01

    The natural abundance of nitrogen and oxygen isotopes in nitrate can be a powerful tool for identifying the source of nitrate in streamwater in forested watersheds, because the two main sources of nitrate, atmospheric deposition and microbial nitrification, have distinct ?18O values. Using a simple mixing model, we estimated the relative fractions in streamwater derived from these sources for two forested watersheds with markedly different streamwater nitrate outputs. In this study, we monitored ?15N and ?18O of nitrate biweekly in atmospheric deposition and in streamwater for 20 months at the Hubbard Brook Experimental Forest, New Hampshire, USA (moderate nitrogen export), and monthly in streamwater at the Bowl Research Natural Area, New Hampshire, USA (high nitrogen export). For rain, ?18O values ranged from +47 to +77‰ (mean: +58‰) and ?15N from ?5 to +1‰ (mean: ?3‰); for snow, ?18O values ranged from +52 to +75‰ (mean: +67‰) and ?15N from ?3 to +2‰ (mean: ?1‰). Streamwater nitrate, in contrast to deposition, had ?18O values between +12 and +33‰ (mean: +18‰) and ?15N between ?3 and +6‰ (mean: 0‰). Since nitrate produced by nitrification typically has ?18O values ranging from ?5 to +15‰, our field data suggest that most of the nitrate lost from the watersheds in streamflow was nitrified within the catchment. Our results confirm the importance of microbial nitrogen transformations in regulating nitrogen losses from forested ecosystems and suggest that hydrologic storage may be a factor in controlling catchment nitrate losses.

  13. Transposases are the most abundant, most ubiquitous genes in nature

    PubMed Central

    Aziz, Ramy K.; Breitbart, Mya; Edwards, Robert A.

    2010-01-01

    Genes, like organisms, struggle for existence, and the most successful genes persist and widely disseminate in nature. The unbiased determination of the most successful genes requires access to sequence data from a wide range of phylogenetic taxa and ecosystems, which has finally become achievable thanks to the deluge of genomic and metagenomic sequences. Here, we analyzed 10 million protein-encoding genes and gene tags in sequenced bacterial, archaeal, eukaryotic and viral genomes and metagenomes, and our analysis demonstrates that genes encoding transposases are the most prevalent genes in nature. The finding that these genes, classically considered as selfish genes, outnumber essential or housekeeping genes suggests that they offer selective advantage to the genomes and ecosystems they inhabit, a hypothesis in agreement with an emerging body of literature. Their mobile nature not only promotes dissemination of transposable elements within and between genomes but also leads to mutations and rearrangements that can accelerate biological diversification and—consequently—evolution. By securing their own replication and dissemination, transposases guarantee to thrive so long as nucleic acid-based life forms exist. PMID:20215432

  14. Natural variability in abundance of prevalent soybean proteins.

    PubMed

    Natarajan, Savithiry S

    2010-12-01

    Soybean is an inexpensive source of protein for humans and animals. Genetic modifications (GMO) to soybean have become inevitable on two fronts, both quality and yield will need to improve to meet increasing global demand. To ensure the safety of the crop for consumers it is important to determine the natural variation in seed protein constituents as well as any unintended changes that may occur in the GMO as a result of genetic modification. Understanding the natural variation of seed proteins in wild and cultivated soybeans that have been used in conventional soybean breeding programs is critical for determining unintended protein expression in GMO soybeans. In recent years, proteomic technologies have been used as an effective analytical tool for examining modifications of protein profiles. We have standardized and applied these technologies to determine and quantify the spectrum of proteins present in soybean seed. We used two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), and liquid chromatography mass spectrometry (LC-MS) for the separation, quantification, and identification of different classes of soybean seed proteins. We have observed significant variations in different classes of proteins, including storage, allergen and anti-nutritional protein profiles, between non-GMO cultivated and wild soybean varieties. This information is useful for scientists and regulatory agencies to determine whether the unintended expression of proteins found in transgenic soybean is within the range of natural variation. PMID:20709130

  15. Measuring denitrification after grassland renewal and grassland conversion to cropland by using the 15N gas-flux method

    NASA Astrophysics Data System (ADS)

    Buchen, Caroline; Eschenbach, Wolfram; Flessa, Heinz; Giesemann, Anette; Lewicka-Szczebak, Dominika; Well, Reinhard

    2015-04-01

    Denitrification, the reduction of oxidized forms of inorganic N to N2O and N2 is an important pathway of gaseous nitrogen losses. Measuring denitrification, especially the reduction of N2O to N2, expressed in the product ratio (N2O/(N2O + N2)), is rather difficult and hence rarely performed under field conditions. But using the 15N gas-flux method allows determining N transformation processes in their natural environment. In order to develop effective climate mitigation strategies understanding the N2O source is essential. We used the 15N gas-flux method to determine N2O and N2 emissions following grassland renewal and conversion techniques. Therefore we selected three different treatments: control (C), mechanical grassland renovation (GR) (autumn 2013) and grassland conversion to maize (GM) (spring 2014) from field plot trials on two different sites (Histic Gleysoil and Plaggic Anthrosol) near Oldenburg, Lower Saxony, Germany. We applied 15N labeled KNO3- (60 atom. % 15N) at a rate equivalent to common farming practices (150 kg N*ha-1) using needle injection of fertilizer solution in three different depths (10 cm, 15 cm, 20 cm) for homogeneous soil labeling up to 30 cm in microplots. During the first 10 days after application (May 2014) gas flux measurements from closed chambers were performed every second day and then weekly following a period of 8 weeks. Gas samples were analyzed for ?15N of N2 and N2O by IRMS according to Lewicka-Szczebak et al. (2013). Concentration and 15N enrichment of NO3- in soil water was determined on weekly samples using the SPIN-MAS technique (Stange et al. 2007). Fluxes of N2 and N2O evolved from the 15N labeled soil nitrogen pool were calculated using the equations of Spott et al. (2006). Peak events of N2 and N2O emissions occurred during the first 10 days of measurement, showing differences in soil types, as well as treatment variations. N2 fluxes up to 178 g*ha-1*day-1 and N2O fluxes up to 280 g*ha-1*day-1 were measured on the Plaggic Anthrosol in the GR treatment, while on the Histic Gleysoil, the GM treatment showed highest fluxes with N2 fluxes up to 1260 g*ha-1*day-1 and N2O fluxes up to 747 g*ha-1*day-1. Alike the product ratio of initial fluxes was higher on the Plaggic Anthrosol and lower on the Histic Gleysoil. Data analysis is still in progress and further results will be provided. References: Lewicka-Szczebak, D., R. Well, A. Giesemann, L. Rohe and U. Wolf (2013). "An enhanced technique for automated determination of 15N signatures of N2, (N2+N2O) and N2O in gas samples." Rapid Communications in Mass Spectrometry 27(13): 1548-1558. Spott, O., R. Russow, B. Apelt and C. F. Stange (2006). "A 15N-aided artificial atmosphere gas flow technique for online determination of soil N2 release using the zeolite Köstrolith SX6®." Rapid Communications in Mass Spectrometry 20(22): 3267-3274. Stange, F., O. Spott, B. Apelt and R. W. Russow (2007). "Automated and rapid online determination of 15N abundance and concentration of ammonium, nitrite, or nitrate in aqueous samples by the SPINMAS technique." Isotopes in Environmental and Health Studies 43(3): 227-236.

  16. Synthesizing physical and microbial controls on isotopic composition of nitrate in rivers: a model for increasing precision of natural abundance-based assessments

    NASA Astrophysics Data System (ADS)

    Wells, N. S.; Clough, T. J.; Baisden, W. T.

    2009-12-01

    Precise and accurate tracers of nitrate (NO3-) transformations in river systems are needed to successfully mitigate the threat it poses to water quality. Natural abundances of NO3- isotopes (?15N-NO3- and ?18O-NO3-) have the potential to act as just such tracers, but their use is currently limited by the frequent inability to differentiate between terrestrial NO3- sources and in-stream NO3- processing. The model we have developed provides a framework for assessing the impact of hydrodynamic conditions on ?15N-NO3 and ?18O-NO3- abundances, enabling a more accurate determination of in-stream nitrogen (N) transformations. The differential advection-diffusion model used to describe fluxes between two boxes (water column and sediments) overlays three layers of NO3- processing: 1) denitrification within the water column, 2) nitrification of reduced N inputs, and 3) denitrification within the sediments. This model highlights the importance of stream hydrology and sediment composition in defining the apparent isotopic fractionation effect measured in the water column. Isotope fractionation during diffusive sediment-water exchange appears to result in an underestimation of microbial processes. Fundamental hydrologic stream characteristics input into the base equations were used to parameterize the importance of diffusive transport within a given reach, resulting in a quantitative compensation for its variable effect able to increases accuracy of denitrification measurements under low-flow conditions. This model represents the first effort to quantity the role of sediments and hydrology in controlling NO3- dual-isotope biogeochemistry in rivers, thus providing a foundation for making isotope-based source identification applicable across a wider range of biophysical conditions. We will also discuss field application of the model using NO3- isotope composition profiles from streams and ditches in agriculturally- dominated catchments in New Zealand.

  17. A novel method for determination of the (15) N isotopic composition of Rubisco in wheat plants exposed to elevated atmospheric carbon dioxide.

    PubMed

    Aranjuelo, Iker; Molero, Gemma; Avice, Jean Christophe; Bourguignon, Jacques

    2015-02-01

    Although ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is mostly known as a key enzyme involved in CO2 assimilation during the Calvin cycle, comparatively little is known about its role as a pool of nitrogen storage in leaves. For this purpose, we developed a protocol to purify Rubisco that enables later analysis of its (15) N isotope composition (?(15) N) at the natural abundance and (15) N-labeled plants. In order to test the utility of this protocol, durum wheat (Triticum durum var. Sula) exposed to an elevated CO2 concentration (700 vs 400 µmol mol(-1) ) was labeled with K(15) NO3 (enriched at 2 atom %) during the ear development period. The developed protocol proves to be selective, simple, cost effective and reproducible. The study reveals that (15) N labeling was different in total organic matter, total soluble protein and the Rubisco fraction. The obtained data suggest that photosynthetic acclimation in wheat is caused by Rubisco depletion. This depletion may be linked to preferential nitrogen remobilization from Rubisco toward grain filling. PMID:25272325

  18. Nitrogen Isotopic Ratios in Cometary NH2: Implication for 15N-fractionation in Ammonia

    NASA Astrophysics Data System (ADS)

    Shinnaka, Yoshiharu; Kawakita, Hideyo; Jehin, Emmanuël; Decock, Alice; Hutsemékers, Damien; Manfroid, Jean; Arai, Akira

    2015-11-01

    Isotopic ratios in cometary molecules are diagnostic for the physico-chemical conditions where molecules formed and are processed, from the interstellar medium to the solar nebula. Usually temperatures at the molecular formation control the fractionation of the heavier element in molecular species, e.g., D-fractionation in water.In cometary volatiles, the 14N/15N ratios in CN have been well observed (Manfroid et al. 2009, A&A, 503, 613, and reference therein) and is consistent with the ratio in HCN (a most probable parent of CN) measured in few comets (Bockelée-Morvan et al. 2008, ApJ, 679, L49). Those ratios are enriched compared to the proto-solar value by a factor of ~3. In contrast to those Nitriles, there are only few reports on 14N/15N ratios in Ammonia (as Amine) (Rousselot et al. 2014, ApJ, 780, L17; Shinnaka et al. 2014, ApJ, 782, L16). Ammonia (NH3) is usually the most abundant and HCN is the second most abundant N-bearing volatiles in cometary ice. Especially, recent observations of 15NH2 revealed the 14N/15N ratios in NH3 are comparable to those of CN. However, from the viewpoint of theoretical work, the enrichment of 15N in cometary NH3 cannot be reproduced by current chemical network models. Information about the diversity of the 14N/15N ratios in NH3 of individual comets is needed to understand the formation mechanisms/environments of NH3 in the early solar system.To clarify the diversity of the 14N/15N ratios in cometary NH3, we determine the 14N/15N ratios in NH3 for more than ten comets individually which include not only Oort cloud comets but also short period comets by using the high-resolution optical spectra of NH2. These spectra were obtained with both the UVES mounted on the VLT in Chile and the HDS on the Subaru Telescope in Hawaii.The derived 14N/15N ratios in NH3 for more than ten comets show high 15N-enrichment compared with the elemental abundances of nitrogen in the Sun by about factor of ~3 and has no large diversity depending on these dynamical properties. We discuss about the origin of the formation conditions of cometary NH3 and its physico-chemical evolution in the solar nebula based on our and other results.This work was supported by JSPS, 15J10864 (Y. Shinnaka).

  19. Two new organic reference materials for ?13C and ?15N measurements and a new value for the ?13C 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 ?13C value of ?26.24‰ relative to VPDB and a ?15N 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 ?13C value of +37.76‰ and a ?15N value of +47.57‰. The ?13C and ?15N values of both materials were measured against the international reference materials NBS 19 calcium carbonate (?13C?=?+1.95‰), L-SVEC lithium carbonate (?13C?=??46.48‰), IAEA-N-1 ammonium sulfate (?15N?=?0.43‰), and USGS32 potassium nitrate (?15N?=?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 ?13C is better than 0.13‰, and that of ?15N is better than 0.13‰ in 100-?g 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 ?13C 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.

  20. Natural Abundance 17O NMR Spectroscopy of Rat Brain In Vivo

    PubMed Central

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

    2008-01-01

    Oxygen is an abundant element that is present in almost all biologically relevant molecules. NMR observation of oxygen has been relatively limited since the NMR-active isotope, oxygen-17, is only present at a 0.037% natural abundance. Furthermore, as a spin 5/2 nucleus oxygen-17 has a moderately strong quadrupole moment which leads to fairly broad resonances (T2* = 1 - 4 ms). However, the similarly short T1 relaxation constants allow substantial signal averaging, whereas the large chemical shift range (> 300 ppm) improves the spectral resolution of 17O NMR. Here it is shown that high-quality, natural abundance 17O NMR spectra can be obtained from rat brain in vivo at 11.74 T. The chemical shifts and line widths of more than 20 oxygen-containing metabolites are established and the sensitivity and potential for 17O-enriched NMR studies are estimated. PMID:18456525

  1. Fine Root Production and Mortality From 15N Tracer Studies

    E-print Network

    Post, Wilfred M.

    Fine Root Production and Mortality From 15N Tracer Studies (and some other stuff on soil 13C Root Production and Mortality · Mass balance 15N tracer method (Hendricks et al., 1997) Labeling soil plots with enriched 15N Temporal measurements · mass of N in fine root structural pool (mi and mf) · 15

  2. Plant Characteristics Associated with Natural Enemy Abundance at Michigan Native Plants

    E-print Network

    Landis, Doug

    BEHAVIOR Plant Characteristics Associated with Natural Enemy Abundance at Michigan Native Plants A. K. FIEDLER1 AND D. A. LANDIS Department of Entomology, 204 Center for Integrated Plant Systems populations by providing them with plant resources such as pollen and nectar. Insects are known to respond

  3. Seed Abundance for Waterfowl in Wetlands Managed by the Illinois Department of Natural Resources

    E-print Network

    Articles Seed Abundance for Waterfowl in Wetlands Managed by the Illinois Department of Natural-making. During 2005­ 2007, we used a multistage sampling design to estimate moist-soil plant seed production (kg Resources and modeled variation in seed biomass. Average seed biomass among all sites ranged from 1,030.0 6

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

    DOE PAGESBeta

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

    2015-06-22

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

  5. Species richness and relative abundance of birds in natural and anthropogenic fragments of Brazilian Atlantic forest.

    PubMed

    dos Anjos, Luiz

    2004-06-01

    Bird communities were studied in two types of fragmented habitat of Atlantic forest in the State of Paraná, southern Brazil; one consisted of forest fragments that were created as a result of human activities (forest remnants), the other consisted of a set of naturally occurring forest fragments (forest patches). Using quantitative data obtained by the point counts method in 3 forest patches and 3 forest remnants during one year, species richness and relative abundance were compared in those habitats, considering species groups according to their general feeding habits. Insectivores, omnivores, and frugivores presented similar general tendencies in both habitats (decrease of species number with decreasing size and increasing isolation of forest fragment). However, these tendencies were different, when considering the relative abundance data: the trunk insectivores presented the highest value in the smallest patch while the lowest relative abundance was in the smallest remnant. In the naturally fragmented landscape, time permitted that the loss of some species of trunk insectivores be compensated for the increase in abundance of other species. In contrast, the remnants essentially represented newly formed islands that are not yet at equilibrium and where future species losses would make them similar to the patches. PMID:15258661

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  7. Increased natural mortality at low abundance can generate an Allee effect in a marine fish.

    PubMed

    Kuparinen, Anna; Hutchings, Jeffrey A

    2014-10-01

    Negative density-dependent regulation of population dynamics promotes population growth at low abundance and is therefore vital for recovery following depletion. Inversely, any process that reduces the compensatory density-dependence of population growth can negatively affect recovery. Here, we show that increased adult mortality at low abundance can reverse compensatory population dynamics into its opposite-a demographic Allee effect. Northwest Atlantic cod (Gadus morhua) stocks collapsed dramatically in the early 1990s and have since shown little sign of recovery. Many experienced dramatic increases in natural mortality, ostensibly attributable in some populations to increased predation by seals. Our findings show that increased natural mortality of a magnitude observed for overfished cod stocks has been more than sufficient to fundamentally alter the dynamics of density-dependent population regulation. The demographic Allee effect generated by these changes can slow down or even impede the recovery of depleted populations even in the absence of fishing. PMID:26064531

  8. Increased natural mortality at low abundance can generate an Allee effect in a marine fish

    PubMed Central

    Kuparinen, Anna; Hutchings, Jeffrey A.

    2014-01-01

    Negative density-dependent regulation of population dynamics promotes population growth at low abundance and is therefore vital for recovery following depletion. Inversely, any process that reduces the compensatory density-dependence of population growth can negatively affect recovery. Here, we show that increased adult mortality at low abundance can reverse compensatory population dynamics into its opposite—a demographic Allee effect. Northwest Atlantic cod (Gadus morhua) stocks collapsed dramatically in the early 1990s and have since shown little sign of recovery. Many experienced dramatic increases in natural mortality, ostensibly attributable in some populations to increased predation by seals. Our findings show that increased natural mortality of a magnitude observed for overfished cod stocks has been more than sufficient to fundamentally alter the dynamics of density-dependent population regulation. The demographic Allee effect generated by these changes can slow down or even impede the recovery of depleted populations even in the absence of fishing. PMID:26064531

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

    PubMed

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

    2015-10-01

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

  10. Determination of lithium isotopes at natural abundance levels by atomic absorption spectrometry

    USGS Publications Warehouse

    Meier, A.L.

    1982-01-01

    The relationships of the absorption of 6Li and 7Li hollow cathode lamp emissions are used to determine lithium isotopic composition in the natural abundance range of geologic materials. Absorption was found to have a nonlinear dependence upon total lithium concentration and isotopic composition. A method using nonlinear equations to describe the relationship of the absorption of 6Li and 7Li lamp radiation is proposed as a means of calculating isotopic composition that is independent of total lithium concentration.

  11. Compound-specific ?15N and chlorin preservation in surface sediments of the Peru Margin with implications for ancient bulk ?15N records

    NASA Astrophysics Data System (ADS)

    Junium, Christopher K.; Arthur, Michael A.; Freeman, Katherine H.

    2015-07-01

    Understanding the processes that control the preservation of paleoceanographic proxies is of clear importance. Surface sediments from the Peru Margin oxygen-minimum zone are subject to lateral and downslope transport by bottom currents that decrease organic matter (OM) quality. Indicators of bulk OM quality (pyrolysis hydrogen index, pyrolysis S1 + S2 and C/N) demonstrate significant degradation between 150 and 400 m water depth, within the oxygen-minimum zone. Concentrations of the three most abundant chlorins (chlorophyllone, pheophytin and pyropheophytin) decrease from 750 to 150 nmol g TOC-1 from 150 to 400 m water depth though the relative abundances of the chlorins in an individual sample do not change. This suggests that the three chlorins have similar reactivity over the ambient conditions. Values for ?15N of bulk sediments (?15Nbulk) decrease by 3‰ from the inner shelf to the upper slope (1000 m) but co-occurring compound-specific ?15N values (?15Nchlorin) do not decrease downslope. The low variability of ?15Nchlorin values supports a single source for the chlorins, and demonstrates the recalcitrance of ?15Nchlorin values despite degradation. This set of observation raises questions about which type of OM fraction best records 'primary' signatures. We assess two possible models to guide our interpretation of these disparate datasets (1) that decreasing ?15Nbulk values are the result of degradation of a 15N-enriched fraction during downslope transport, and that ?15Nchlorin values reflect primary values; (2) that ?15Nbulk values are primary and that chlorins are derived from material transported from upslope. These data reaffirm that in active sedimentary environments such as the Eastern Tropical Pacific, transport of OM can significantly alter bulk geochemical parameters of OM integrity, but the impacts on the ?15N record of bulk sediments and chlorins are less clear, and require more study to be thoroughly understood.

  12. The Continuing Search for the Location of 15N-Enriched Nitrogen in ACFER 182

    NASA Astrophysics Data System (ADS)

    Grady, M. M.; Pillinger, C. T.; Arden, J. W.

    1992-07-01

    Acfer 182 is an unusual chondrite, with abundant small chondrules and CAIs (mean diameter ca. 100 micrometers), and rich in metal (ca. 15 vol%). It is closely related to ALH 85085, and, like that meteorite, is highly enriched in ^15N (bulk delta^15N ca. +600o/oo; delta^15N(sub)max = +1584o/oo at 900 degrees C; ref. 1). Stepped combustion of Acfer 182 (see figure) releases ^15N over a wide temperature range, indicating that its carriers must be dispersed throughout the meteorite, possibly occurring in carbonaceous material, fine-grained matrix, clasts, and metal. The highest relative abundance of ^15N is found in phase "N(sub)C", so far unidentified mineralogically, with a C/N ca. 10, which releases its nitrogen on combustion of the whole rock at 850-950 degrees C. N(sub)C is more apparent in Acfer 182 than ALH 85085, accounting for ca. 8 ppm of the total nitrogen inventory of 85.4 ppm. An attempt to isolate NC by physical means proved unsuccessful [1], therefore chemical treatments were tried: an HF/HCl-resistant residue was prepared from 9 g of fragments. Examination of the remaining material confirmed that it was dominantly composed of Mg-Al spinels, chromite, hibonite, and Cr-rich sulphides. Approximately two thirds of the original amount of nitrogen in the sample has been lost on dissolution (see figure), including any associated with Fe-Ni metal. There has been a reduction of over 50% of the nitrogen that was released up to 500 degrees C and presumed present in a carbonaceous component, without significant change in delta^15N value or C/N ratio. The most visible difference between results from the whole-rock and HF/HCl-resistant residue is that the combustion temperature of NC has decreased to 550-700 degrees C, with a concomitant drop in delta^15N from +1584o/oo to +1274o/oo It is unlikely that a minor (even heavier) sub-fraction of the ^15N-rich material has been removed; now that N(sub)C combusts at a temperature closer to the more abundant "organic" nitrogen, it is probable that mixing lowers the observed delta^15N. N(sub)C itself does not seem to be totally immune from the acid attack: only 3 ppm remain from the original concentration of 8 ppm in the whole-rock meteorite. N(sub)C has still not been identified, but is further operationally defined. The combustion temperature of N(sub)C in the acid-resistant residue constrains its identification: nitrogen present as Si3N4 or substituted in SiC does not seem likely, unless the minerals are extremely fine-grained or exceptionally radiation-damaged. It is possible that N(sub)C is hosted by a mineral not previously suggested as a presolar grain, assuming that the ^15N-enrichments described are indicative of such an origin. The more complex problem of how isotopically heavy nitrogen is so completely distributed throughout the meteorite may become more easy to address once the most likely source of the ^15N-enrichment is positively identified. One possibility is that parent-body processing, including shock, degassed a component of interstellar origin, which subsequently exchanged with or nitrified other phases. Reference: [1] Grady, M. M. and Pillinger, C. T. (1992) Earth Planet. Sci. Lett. (submitted)

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

    PubMed

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

    2005-06-29

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

  14. Effect of Environmental Factors on Cyanobacterial Abundance and Cyanotoxins Production in Natural and Drinking Water, Bangladesh.

    PubMed

    Affan, Abu; Khomavis, Hisham S; Al-Harbi, Salim Marzoog; Haque, Mahfuzul; Khan, Saleha

    2015-02-01

    Cyanobacterial blooms commonly appear during the summer months in ponds, lakes and reservoirs in Bangladesh. In these areas, fish mortality, odorous water and fish and human skin irritation and eye inflammation have been reported. The influence of physicochemical factors on the occurrence of cyanobacteria and its toxin levels were evaluated in natural and drinking water in Bangladesh. A highly sensitive immunosorbent assay was used to detect microcystins (MCs). Cyanobacteria were found in 22 of 23 samples and the dominant species were Microcystis aeruginosa, followed by Microcystisflosaquae, Anabeana crassa and Aphanizomenon flosaquae. Cyanobacterial abundance varied from 39 to 1315 x 10(3) cells mL(-1) in natural water and 31 to 49 x 10(3) cells mL(-1) in tap water. MC concentrations were 25-82300 pg mL(-1) with the highest value measured in the fish research pond, followed by Ishakha Lake. In tap water, MC concentrations ranged from 30-32 pg mL(-1). The correlation between nitrate-nitrogen (NO3-N) concentration and cyanobacterial cell abundance was R2 = 0.62 while that between cyanobacterial abundance and MC concentration was R2 = 0.98. The increased NO3-N from fish feed, organic manure, poultry and dairy farm waste and fertilizer from agricultural land eutrophicated the water bodies and triggered cyanobacterial bloom formation. The increased amount of cyanobacteria produced MCs, subsequently reducing the water quality. PMID:26364354

  15. Widespread foliage d15 N depletion under elevated CO2

    E-print Network

    Thomas, David D.

    Widespread foliage d15 N depletion under elevated CO2: inferences for the nitrogen cycle H O R M O an integrated assessment of the nitrogen (N) cycle and whether it is influenced by rising atmospheric CO2 within the plant/mycorrhizal system. Keywords: elevated CO2, FACE, foliage 15 N, nitrogen cycle Received

  16. The distribution of nitrate 15 N in marine sediments

    E-print Network

    Sigman, Daniel M.

    The distribution of nitrate 15 N/14 N in marine sediments and the impact of benthic nitrogen loss on the isotopic composition of oceanic nitrate Moritz F. Lehmann a,*, Daniel M. Sigman b , Daniel C. McCorkle c 15 N/14 N ratios of porewater nitrate in sediments from the Bering Sea basin, where microbial nitrate

  17. Plant community change mediates the response of foliar ?(15)N to CO 2 enrichment in mesic grasslands.

    PubMed

    Polley, H Wayne; Derner, Justin D; Jackson, Robert B; Gill, Richard A; Procter, Andrew C; Fay, Philip A

    2015-06-01

    Rising atmospheric CO2 concentration may change the isotopic signature of plant N by altering plant and microbial processes involved in the N cycle. CO2 may increase leaf ?(15)N by increasing plant community productivity, C input to soil, and, ultimately, microbial mineralization of old, (15)N-enriched organic matter. We predicted that CO2 would increase aboveground productivity (ANPP; g biomass m(-2)) and foliar ?(15)N values of two grassland communities in Texas, USA: (1) a pasture dominated by a C4 exotic grass, and (2) assemblages of tallgrass prairie species, the latter grown on clay, sandy loam, and silty clay soils. Grasslands were exposed in separate experiments to a pre-industrial to elevated CO2 gradient for 4 years. CO2 stimulated ANPP of pasture and of prairie assemblages on each of the three soils, but increased leaf ?(15)N only for prairie plants on a silty clay. ?(15)N increased linearly as mineral-associated soil C declined on the silty clay. Mineral-associated C declined as ANPP increased. Structural equation modeling indicted that CO2 increased ANPP partly by favoring a tallgrass (Sorghastrum nutans) over a mid-grass species (Bouteloua curtipendula). CO2 may have increased foliar ?(15)N on the silty clay by reducing fractionation during N uptake and assimilation. However, we interpret the soil-specific, ?(15)N-CO2 response as resulting from increased ANPP that stimulated mineralization from recalcitrant organic matter. By contrast, CO2 favored a forb species (Solanum dimidiatum) with higher ?(15)N than the dominant grass (Bothriochloa ischaemum) in pasture. CO2 enrichment changed grassland ?(15)N by shifting species relative abundances. PMID:25604918

  18. FOLIAR NITROGEN CONCENTRATIONS AND NATURAL ABUNDANCE OF 15N SUGGEST NITROGEN ALLOCATION PATTERNS OF DOUGLAS-FIR AND MYCORRHIZAL FUNGI DURING DEVELOPMENT IN ELEVATED CARBON DIOXIDE CONCENTRATION AND TEMPERATURE

    EPA Science Inventory

    In an experiment using Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir) seedlings and a 2x2 factorial design in enclosed mesocosms, temperatures were maintained at ambient or +3.5 degrees C above ambient, and CO2 levels were maintained at ambient or 179 ppm above ambient. Two ...

  19. Natural-abundance 17O NMR spectra of some inorganic and biologically important phosphates

    NASA Astrophysics Data System (ADS)

    Gerothanassis, Ioannis P.; Sheppard, Norman

    A number of optimization techniques were employed to obtain 17O NMR spectra at natural abundance for a variety of inorganic and orgnic phosphates and polyphosphates. 17O chemical shifts and some JPO coupling constants are reported for the orthophosphate series of ions from H 3PO 4 to PO 43-, the pyrophosphate ion, P 2O 74-, the linear tripolyphosphate ion, P 3O 105-, and the cyclic trimetaphosphate ion, P 3O 93-; and for disodium DL-?-glycerophosphate and monosodium adenosine monophosphate. 17O- depleted water enables much improved results to be obtained in acqueous solutions.

  20. Changes in protein abundance are observed in bacterial isolates from a natural host.

    PubMed

    Rees, Megan A; Stinear, Timothy P; Goode, Robert J A; Coppel, Ross L; Smith, Alexander I; Kleifeld, Oded

    2015-01-01

    Bacterial proteomic studies frequently use strains cultured in synthetic liquid media over many generations. It is uncertain whether bacterial proteins expressed under these conditions will be the same as the repertoire found in natural environments, or when bacteria are infecting a host organism. Thus, genomic and proteomic characterization of bacteria derived from the host environment in comparison to reference strains grown in the lab, should aid understanding of pathogenesis. Isolates of Corynebacterium pseudotuberculosis were obtained from the lymph nodes of three naturally infected sheep and compared to a laboratory reference strain using bottom-up proteomics, after whole genome sequencing of each of the field isolates. These comparisons were performed following growth in liquid media that allowed us to reach the required protein amount for proteomic analysis. Over 1350 proteins were identified in the isolated strains, from which unique proteome features were revealed. Several of the identified proteins demonstrated a significant abundance difference in the field isolates compared to the reference strain even though there were no obvious differences in the DNA sequence of the corresponding gene or in nearby non-coding DNA. Higher abundance in the field isolates was observed for proteins related to hypoxia and nutrient deficiency responses as well as to thiopeptide biosynthesis. PMID:26528441

  1. Changes in protein abundance are observed in bacterial isolates from a natural host

    PubMed Central

    Rees, Megan A.; Stinear, Timothy P.; Goode, Robert J. A.; Coppel, Ross L.; Smith, Alexander I.; Kleifeld, Oded

    2015-01-01

    Bacterial proteomic studies frequently use strains cultured in synthetic liquid media over many generations. It is uncertain whether bacterial proteins expressed under these conditions will be the same as the repertoire found in natural environments, or when bacteria are infecting a host organism. Thus, genomic and proteomic characterization of bacteria derived from the host environment in comparison to reference strains grown in the lab, should aid understanding of pathogenesis. Isolates of Corynebacterium pseudotuberculosis were obtained from the lymph nodes of three naturally infected sheep and compared to a laboratory reference strain using bottom-up proteomics, after whole genome sequencing of each of the field isolates. These comparisons were performed following growth in liquid media that allowed us to reach the required protein amount for proteomic analysis. Over 1350 proteins were identified in the isolated strains, from which unique proteome features were revealed. Several of the identified proteins demonstrated a significant abundance difference in the field isolates compared to the reference strain even though there were no obvious differences in the DNA sequence of the corresponding gene or in nearby non-coding DNA. Higher abundance in the field isolates was observed for proteins related to hypoxia and nutrient deficiency responses as well as to thiopeptide biosynthesis. PMID:26528441

  2. Natural abundances of carbon isotopes in acetate from a coastal marine sediment

    NASA Technical Reports Server (NTRS)

    Blair, N. E.; Martens, C. S.; Des Marais, D. J.

    1987-01-01

    Measurements of the natural abundances of carbon isotopes were made in acetate samples isolated from the anoxic marine sediment of Cape Lookout Bight, North Carolina. The typical value of the total acetate carbon isotope ratio (delta 13C) was -16.1 +/- 0.2 per mil. The methyl and carboxyl groups were determined to be -26.4 +/- 0.3 and -6.0 +/- 0.3 per mil, respectively, for one sample. The isotopic composition of the acetate is thought to have resulted from isotopic discriminations that occurred during the cycling of that molecule. Measurements of this type, which have not been made previously in the natural environment, may provide information about the dominant microbial pathways in anoxic sediments as well as the processes that influence the carbon isotopic composition of biogenic methane from many sources.

  3. 15N/14N variations in Cretaceous Atlantic sedimentary sequences: implication for past changes in marine nitrogen biogeochemistry

    USGS Publications Warehouse

    Rau, G.H.; Arthur, M.A.; Dean, W.E.

    1987-01-01

    At two locations in the Atlantic Ocean (DSDP Sites 367 and 530) early to middle Cretaceous organic-carbon-rich beds ("black shales") were found to have significantly lower ??15N values (lower 15N/14N ratios) than adjacent organic-carbon-poor beds (white limestones or green claystones). While these lithologies are of marine origin, the black strata in particular have ??15N values that are significantly lower than those previously found in the marine sediment record and most contemporary marine nitrogen pools. In contrast, black, organic-carbon-rich beds at a third site (DSDP Site 603) contain predominantly terrestrial organic matter and have C- and N-isotopic compositions similar to organic matter of modern terrestrial origin. The recurring 15N depletion in the marine-derived Cretaceous sequences prove that the nitrogen they contain is the end result of an episodic and atypical biogeochemistry. Existing isotopic and other data indicate that the low 15N relative abundance is the consequence of pelagic rather than post-depositional processes. Reduced ocean circulation, increased denitrification, and, hence, reduced euphotic zone nitrate availability may have led to Cretaceous phytoplankton assemblages that were periodically dominated by N2-fixing blue-green algae, a possible source of this sediment 15N-depletion. Lack of parallel isotopic shifts in Cretaceous terrestrially-derived nitrogen (Site 603) argues that the above change in nitrogen cycling during this period did not extend beyond the marine environment. ?? 1987.

  4. Solid-state 15N NMR studies of tobacco leaves.

    PubMed

    Ma, Zhiru; Barich, Dewey H; Solum, Mark S; Pugmire, Ronald J

    2004-01-28

    Nitrogen-containing compounds are one important class of constituents in tobacco because of various pharmacological and biological properties. Three types of tobacco leaves (burley, bright, and oriental) were studied using solid-state (15)N NMR cross polarization with magic-angle spinning, dipolar dephasing and five pi replicated magic angle turning (FIREMAT) experiments. The results show that burley tobacco leaves contain significantly more pyridinic nitrogen than that of bright or oriental tobacco leaves. The principal values of (15)N chemical shift tensors of nitrogen functional groups were obtained from the FIREMAT data. Possible assignments of solid-state (15)N NMR resonances were made using nitrogen chemical shift tensors in some model compounds or isotropic chemical shift values from liquid NMR results. To the best of our knowledge, this is the first solid-state (15)N NMR study of tobacco plant material. PMID:14733498

  5. ?15N Value Does Not Reflect Fasting in Mysticetes

    PubMed Central

    Aguilar, Alex; Giménez, Joan; Gómez–Campos, Encarna; Cardona, Luís; Borrell, Asunción

    2014-01-01

    The finding that tissue ?15N values increase with protein catabolism has led researchers to apply this value to gauge nutritive condition in vertebrates. However, its application to marine mammals has in most occasions failed. We investigated the relationship between ?15N values and the fattening/fasting cycle in a model species, the fin whale, a migratory capital breeder that experiences severe seasonal variation in body condition. We analyzed two tissues providing complementary insights: one with isotopic turnover (muscle) and one that keeps a permanent record of variations in isotopic values (baleen plates). In both tissues ?15N values increased with intensive feeding but decreased with fasting, thus contradicting the pattern previously anticipated. The apparent inconsistency during fasting is explained by the fact that a) individuals migrate between different isotopic isoscapes, b) starvation may not trigger significant negative nitrogen balance, and c) excretion drops and elimination of 15N-depleted urine is minimized. Conversely, when intensive feeding is resumed in the northern grounds, protein anabolism and excretion start again, triggering 15N enrichment. It can be concluded that in whales and other mammals that accrue massive depots of lipids as energetic reserves and which have limited access to drinking water, the ?15N value is not affected by fasting and therefore cannot be used as an indicatior of nutritive condition. PMID:24651388

  6. Abundance and phenology patterns of two pond-breeding salamanders determine species interactions in natural populations.

    PubMed

    Anderson, Thomas L; Hocking, Daniel J; Conner, Christopher A; Earl, Julia E; Harper, Elizabeth B; Osbourn, Michael S; Peterman, William E; Rittenhouse, Tracy A G; Semlitsch, Raymond D

    2015-03-01

    Phenology often determines the outcome of interspecific interactions, where early-arriving species often dominate interactions over those arriving later. The effects of phenology on species interactions are especially pronounced in aquatic systems, but the evidence is largely derived from experimental studies. We examined whether differences in breeding phenology between two pond-breeding salamanders (Ambystoma annulatum and A. maculatum) affected metamorph recruitment and demographic traits within natural populations, with the expectation that the fall-breeding A. annulatum would negatively affect the spring-breeding A. maculatum. We monitored populations of each species at five ponds over 4 years using drift fences. Metamorph abundance and survival of A. annulatum were affected by intra- and interspecific processes, whereas metamorph size and date of emigration were primarily influenced by intraspecific effects. Metamorph abundance, snout-vent length, date of emigration and survival for A. maculatum were all predicted by combinations of intra- and interspecific effects, but often showed negative relationships with A. annulatum metamorph traits and abundance. Size and date of metamorphosis were strongly correlated within each species, but in opposite patterns (negative for A. annulatum and positive for A. maculatum), suggesting that the two species use alternative strategies to enhance terrestrial survival and that these factors may influence their interactions. Our results match predictions from experimental studies that suggest recruitment is influenced by intra- and interspecific processes which are determined by phenological differences between species. Incorporating spatiotemporal variability when modeling population dynamics is necessary to understand the importance of phenology in species interactions, especially as shifts in phenology occur under climate change. PMID:25413866

  7. Measuring long-lived 13C2 state lifetimes at natural abundance.

    PubMed

    Claytor, Kevin; Theis, Thomas; Feng, Yesu; Warren, Warren

    2014-02-01

    Long-lived disconnected eigenstates (for example, the singlet state in a system with two nearly equivalent carbons, or the singlet-singlet state in a system with two chemically equivalent carbons and two chemically equivalent hydrogens) hold the potential to drastically extend the lifetime of hyperpolarization in molecular tracers for in vivo magnetic resonance imaging (MRI). However, a first-principles calculation of the expected lifetime (and thus selection of potential imaging agents) is made very difficult because of the large variety of relevant intra- and intermolecular relaxation mechanisms. As a result, all previous measurements relied on costly and time consuming syntheses of (13)C labeled compounds. Here we show that it is possible to determine (13)C singlet state lifetimes by detecting the naturally abundant doubly-labeled species. This approach allows for rapid and low cost screening of potential molecular biomarkers bearing long-lived states. PMID:24457544

  8. Anti-Gal: an abundant human natural antibody of multiple pathogeneses and clinical benefits.

    PubMed

    Galili, Uri

    2013-09-01

    Anti-Gal is the most abundant natural antibody in humans, constituting ~ 1% of immunoglobulins. Anti-Gal is naturally produced also in apes and Old World monkeys. The ligand of anti-Gal is a carbohydrate antigen called the '?-gal epitope' with the structure Gal?1-3Gal?1-4GlcNAc-R. The ?-gal epitope is present as a major carbohydrate antigen in non-primate mammals, prosimians and New World monkeys. Anti-Gal can contributes to several immunological pathogeneses. Anti-Gal IgE produced in some individuals causes allergies to meat and to the therapeutic monoclonal antibody cetuximab, all presenting ?-gal epitopes. Aberrant expression of the ?-gal epitope or of antigens mimicking it in humans may result in autoimmune processes, as in Graves' disease. ?-Gal epitopes produced by Trypanosoma cruzi interact with anti-Gal and induce 'autoimmune like' inflammatory reactions in Chagas' disease. Anti-Gal IgM and IgG further mediate rejection of xenografts expressing ?-gal epitopes. Because of its abundance, anti-Gal may be exploited for various clinical uses. It increases immunogenicity of microbial vaccines (e.g. influenza vaccine) presenting ?-gal epitopes by targeting them for effective uptake by antigen-presenting cells. Tumour lesions are converted into vaccines against autologous tumour-associated antigens by intra-tumoral injection of ?-gal glycolipids, which insert into tumour cell membranes. Anti-Gal binding to ?-gal epitopes on tumour cells targets them for uptake by antigen-presenting cells. Accelerated wound healing is achieved by application of ?-gal nanoparticles, which bind anti-Gal, activate complement, and recruit and activate macrophages that induce tissue regeneration. This therapy may be of further significance in regeneration of internally injured tissues such as ischaemic myocardium and injured nerves. PMID:23578170

  9. Anti-Gal: an abundant human natural antibody of multiple pathogeneses and clinical benefits

    PubMed Central

    Galili, Uri

    2013-01-01

    Summary Anti-Gal is the most abundant natural antibody in humans, constituting ? 1% of immunoglobulins. Anti-Gal is naturally produced also in apes and Old World monkeys. The ligand of anti-Gal is a carbohydrate antigen called the ‘?-gal epitope’ with the structure Gal?1-3Gal?1-4GlcNAc-R. The ?-gal epitope is present as a major carbohydrate antigen in non-primate mammals, prosimians and New World monkeys. Anti-Gal can contributes to several immunological pathogeneses. Anti-Gal IgE produced in some individuals causes allergies to meat and to the therapeutic monoclonal antibody cetuximab, all presenting ?-gal epitopes. Aberrant expression of the ?-gal epitope or of antigens mimicking it in humans may result in autoimmune processes, as in Graves' disease. ?-Gal epitopes produced by Trypanosoma cruzi interact with anti-Gal and induce ‘autoimmune like’ inflammatory reactions in Chagas' disease. Anti-Gal IgM and IgG further mediate rejection of xenografts expressing ?-gal epitopes. Because of its abundance, anti-Gal may be exploited for various clinical uses. It increases immunogenicity of microbial vaccines (e.g. influenza vaccine) presenting ?-gal epitopes by targeting them for effective uptake by antigen-presenting cells. Tumour lesions are converted into vaccines against autologous tumour-associated antigens by intra-tumoral injection of ?-gal glycolipids, which insert into tumour cell membranes. Anti-Gal binding to ?-gal epitopes on tumour cells targets them for uptake by antigen-presenting cells. Accelerated wound healing is achieved by application of ?-gal nanoparticles, which bind anti-Gal, activate complement, and recruit and activate macrophages that induce tissue regeneration. This therapy may be of further significance in regeneration of internally injured tissues such as ischaemic myocardium and injured nerves. PMID:23578170

  10. Time-dependent extinction rate and species abundance in a tangled-nature model of biological evolution

    E-print Network

    Christensen, Kim

    Time-dependent extinction rate and species abundance in a tangled-nature model of biological ecology consisting of a web of interacting individuals, a tangle-nature model. The reproduction rate properties. The macrodynamics exhibit intermittent two-mode switching with a gradually decreasing extinction

  11. Rivermouth Alteration of Agricultural Impacts on Consumer Tissue ?15N

    PubMed Central

    Larson, James H.; Richardson, William B.; Vallazza, Jon M.; Nelson, John C.

    2013-01-01

    Terrestrial agricultural activities strongly influence riverine nitrogen (N) dynamics, which is reflected in the ?15N of riverine consumer tissues. However, processes within aquatic ecosystems also influence consumer tissue ?15N. As aquatic processes become more important terrestrial inputs may become a weaker predictor of consumer tissue ?15N. In a previous study, this terrestrial-consumer tissue ?15N connection was very strong at river sites, but was disrupted by processes occurring in rivermouths (the ‘rivermouth effect’). This suggested that watershed indicators of N loading might be accurate in riverine settings, but could be inaccurate when considering N loading to the nearshore of large lakes and oceans. In this study, the rivermouth effect was examined on twenty-five sites spread across the Laurentian Great Lakes. Relationships between agriculture and consumer tissue ?15N occurred in both upstream rivers and at the outlets where rivermouths connect to the nearshore zone, but agriculture explained less variation and had a weaker effect at the outlet. These results suggest that rivermouths may sometimes be significant sources or sinks of N, which would cause N loading estimates to the nearshore zone that are typically made at discharge gages further upstream to be inaccurate. Identifying definitively the controls over the rivermouth effect on N loading (and other nutrients) will require integration of biogeochemical and hydrologic models. PMID:23935980

  12. On the nature of sn stars. I. A detailed abundance study

    NASA Astrophysics Data System (ADS)

    Saffe, C.; Levato, H.

    2014-02-01

    The sn stars were first discoved by Abt & Levato when studying the spectral types in different open clusters. These stars present sharp Balmer lines, sharp metallic lines (C II, Si II, Ca II, Ti II, Fe II), and broad coreless He I lines. Some of the sn stars seem to be related to CP stars. Initially Abt & Levato proposed a shell-like nature to explain the sn stars, although this scenario was subsequently questioned. There is no general agreement about their origin. We aim to derive abundances for a sample of 9 stars, including sn and non-sn stars, to determine the possible relation between sn and CP stars and compare their chemical abundances. That most sn stars belong to open clusters allows us to search for a possible relation with fundamental parameters, including the age and rotation. We also study the possible contribution of different effects to the broad He I lines observed in these stars, such as Stark broadening and the possible He-stratification. Effective temperature and gravity were estimated by Strömgren photometry and then refined by requiring ionization and excitation equilibrium of Fe lines. We derived the abundances by fitting the observed spectra with synthetic spectra using an iterative procedure with the SYNTHE and ATLAS9 codes. We derived metallic abundances of 23 different chemical elements for 9 stars and obtained low projected rotational velocities for the sn stars in our sample (vsini up to 69 km s-1). We also compared 5 stars that belong to the same cluster (NGC 6475) and show that the sn characteristics appear in the 3 stars with the lower rotational velocity. However, the apparent preference of sn stars for objects with the lower vsini values should be taken with caution due to the small number of objects studied here. We analysed the photospheric chemical composition of sn stars and show that approximately ~40% of them display chemical peculiarities (such as He-weak and HgMn stars) within a range of temperature of 10 300 K-14 500 K. However, there are also sn stars with solar or nearly-solar (i.e. non-CP) chemical composition. We have studied the possible contribution of different processes to the broad He I lines present in the sn stars. Although NLTE effects could not be completely ruled out, it seems that NLTE is not directly related to the broad He I profiles observed in the sn stars. The broad-line He I 4026 Å is the clearest example of the sn characteristics in our sample. We succesfully fit this line in 4 out of 7 sn stars by using the appropriate Stark broadening tables, while small differences appear in the other 3 stars. Studying the plots of abundance vs. depth for the He I lines resulted in some sn stars probably being stratified in He. However, a further study of variability in the He I lines would help for determining whether a possible non-uniform He superficial distribution could also play a role in these sn stars. We conclude that the broad He I lines that characterize the sn class could be modelled (at least in some of these stars) by the usual radiative transfer process with Stark broadening, without needing another broadening mechanism. The observed line broadening in sn stars seems to be related to the "normal" He line formation that originates in these atmospheres.

  13. Solid-State (87)Sr NMR Spectroscopy at Natural Abundance and High Magnetic Field Strength.

    PubMed

    Faucher, Alexandra; Terskikh, Victor V; Ye, Eric; Bernard, Guy M; Wasylishen, Roderick E

    2015-12-10

    Twenty-five strontium-containing solids were characterized via (87)Sr NMR spectroscopy at natural abundance and high magnetic field strength (B0 = 21.14 T). Strontium nuclear quadrupole coupling constants in these compounds are sensitive to the strontium site symmetry and range from 0 to 50.5 MHz. An experimental (87)Sr chemical shift scale is proposed, and available data indicate a chemical shift range of approximately 550 ppm, from -200 to +350 ppm relative to Sr(2+)(aq). In general, magnetic shielding increased with strontium coordination number. Experimentally measured chemical shift anisotropy is reported for stationary samples of solid powdered SrCl2·6H2O, SrBr2·6H2O, and SrCO3, with ?aniso((87)Sr) values of +28, +26, and -65 ppm, respectively. NMR parameters were calculated using CASTEP, a gauge including projector augmented wave (GIPAW) DFT-based program, which addresses the periodic nature of solids using plane-wave basis sets. Calculated NMR parameters are in good agreement with those measured. PMID:26565918

  14. Archaeal community diversity and abundance changes along a natural salinity gradient in estuarine sediments

    PubMed Central

    Webster, Gordon; O'Sullivan, Louise A.; Meng, Yiyu; Williams, Angharad S.; Sass, Andrea M.; Watkins, Andrew J.; Parkes, R. John; Weightman, Andrew J.

    2014-01-01

    Archaea are widespread in marine sediments, but their occurrence and relationship with natural salinity gradients in estuarine sediments is not well understood. This study investigated the abundance and diversity of Archaea in sediments at three sites [Brightlingsea (BR), Alresford (AR) and Hythe (HY)] along the Colne Estuary, using quantitative real-time PCR (qPCR) of 16S rRNA genes, DNA hybridization, Archaea 16S rRNA and mcrA gene phylogenetic analyses. Total archaeal 16S rRNA abundance in sediments were higher in the low-salinity brackish sediments from HY (2–8 × 107 16S rRNA gene copies cm?3) than the high-salinity marine sites from BR and AR (2 × 104–2 × 107 and 4 × 106–2 × 107 16S rRNA gene copies cm?3, respectively), although as a proportion of the total prokaryotes Archaea were higher at BR than at AR or HY. Phylogenetic analysis showed that members of the ‘Bathyarchaeota’ (MCG), Thaumarchaeota and methanogenic Euryarchaeota were the dominant groups of Archaea. The composition of Thaumarchaeota varied with salinity, as only ‘marine’ group I.1a was present in marine sediments (BR). Methanogen 16S rRNA genes from low-salinity sediments at HY were dominated by acetotrophic Methanosaeta and putatively hydrogentrophic Methanomicrobiales, whereas the marine site (BR) was dominated by mcrA genes belonging to methylotrophic Methanococcoides, versatile Methanosarcina and methanotrophic ANME-2a. Overall, the results indicate that salinity and associated factors play a role in controlling diversity and distribution of Archaea in estuarine sediments. PMID:25764553

  15. Soil organic matter stability in agricultural land: New insights using ?15N, ?13C and C:N ratio

    NASA Astrophysics Data System (ADS)

    Mao, Yanling; Heiling, Maria; De Clercq, Tim; Resch, Christian; Aigner, Martina; Mayr, Leo; Vanlauwe, Bernard; Thuita, Moses; Steier, Peter; Leifeld, Jens; Merckx, Roel; Spiegel, Heide; Cepuder, Peter; Nguyen, Minh-Long; Zaman, Mohammad; Dercon, Gerd

    2014-05-01

    Soil organic matter (SOM) contains three times more carbon than in the atmosphere or terrestrial vegetation. This major pool of organic carbon is sensitive to climate change, but the mechanisms for carbon stabilization in soils are still not well understood and the ultimate potential for carbon stabilization is unknown. For predicting SOM dynamics, it is necessary to gain information on the turnover rates or stability of different soil organic carbon pools. The common method to determine stability and age of SOM is the 14C radio carbon technique, which is very expensive and therefore limited in use. Conen et al. (2008) developed a model to estimate the SOM stability based on the isotopic discrimination of 15N natural abundance by soil micro-organisms, and the decreasing C:N ratio during organic matter decomposition. This model has been developed for permanent grasslands in the Swiss Alps under steady-state conditions. The objective of our study was to validate whether this model could be used or adapted, in combination with 13C isotope signatures of SOM, to predict the relative age and stability of SOM fractions in more disturbed agricultural ecosystems. The present study was carried out on soils collected from six long-term experimental trials (from 12 to 50 years) under different agricultural management practices (e.g. no tillage vs conventional tillage, and mulch, fertilizer, green or animal manure application), located in Austria, Belgium, Kenya and China. Top and subsoil were sampled until 80-100 cm depth. Particulate organic matter (POM) fraction was obtained by wet sieving (> 63?m) after sonification and density separation (<1.8 g cm-3). Carbon and nitrogen contents and their stable isotopic ratios (i.e. 15N and 13C) were measured in POM and bulk soils. The mineral associated matter fraction (mOM), as the protected carbon, was calculated by difference to the bulk soil organic carbon. The relative age of the SOM was calculated using the Conen model and preliminary validated by 14C dating. At all sites, the POM has a higher C:N ratio and a lower ?15N signature compared to the mOM fraction. The POM in top soil layers (<30 cm) has a lower C:N ratio than in deep soil. The C:N ratio and ?15N of POM was influenced by agricultural management. The mOM fraction has 53 to 2063 times longer turnover rate than POM, the relative age of the SOM raised with increasing soil depth. The combination of the above results with ?13C data lead to a more comprehensive understanding of the processes underlying SOM dynamics. Tillage practices increased the bulk ?13C signature of the SOM in the deeper subsoil, suggesting the presence of more stable decomposed materials. The results of this research seem to indicate that the model, developed for grasslands, can be used to determine the stability of SOM in agricultural ecosystems. The C:N ratio and ?15N signature of the POM and mOM fraction follow the expected model pattern. The isotopic ?13C signature can further enhance the understanding of the processes driving SOM stability.

  16. Relation of desert pupfish abundance to selected environmental variables in natural and manmade habitats in the Salton Sea basin

    USGS Publications Warehouse

    Martin, B.A.; Saiki, M.K.

    2005-01-01

    We assessed the relation between abundance of desert pupfish, Cyprinodon macularius, and selected biological and physicochemical variables in natural and manmade habitats within the Salton Sea Basin. Field sampling in a natural tributary, Salt Creek, and three agricultural drains captured eight species including pupfish (1.1% of the total catch), the only native species encountered. According to Bray-Curtis resemblance functions, fish species assemblages differed mostly between Salt Creek and the drains (i.e., the three drains had relatively similar species assemblages). Pupfish numbers and environmental variables varied among sites and sample periods. Canonical correlation showed that pupfish abundance was positively correlated with abundance of western mosquitofish, Gambusia affinis, and negatively correlated with abundance of porthole livebearers, Poeciliopsis gracilis, tilapias (Sarotherodon mossambica and Tilapia zillii), longjaw mudsuckers, Gillichthys mirabilis, and mollies (Poecilia latipinnaandPoecilia mexicana). In addition, pupfish abundance was positively correlated with cover, pH, and salinity, and negatively correlated with sediment factor (a measure of sediment grain size) and dissolved oxygen. Pupfish abundance was generally highest in habitats where water quality extremes (especially high pH and salinity, and low dissolved oxygen) seemingly limited the occurrence of nonnative fishes. This study also documented evidence of predation by mudsuckers on pupfish. These findings support the contention of many resource managers that pupfish populations are adversely influenced by ecological interactions with nonnative fishes. ?? Springer 2005.

  17. Natural abundance (?¹?N) indicates shifts in nitrogen relations of woody taxa along a savanna-woodland continental rainfall gradient.

    PubMed

    Soper, Fiona M; Richards, Anna E; Siddique, Ilyas; Aidar, Marcos P M; Cook, Garry D; Hutley, Lindsay B; Robinson, Nicole; Schmidt, Susanne

    2015-05-01

    Water and nitrogen (N) interact to influence soil N cycling and plant N acquisition. We studied indices of soil N availability and acquisition by woody plant taxa with distinct nutritional specialisations along a north Australian rainfall gradient from monsoonal savanna (1,600-1,300 mm annual rainfall) to semi-arid woodland (600-250 mm). Aridity resulted in increased 'openness' of N cycling, indicated by increasing ?(15)N(soil) and nitrate:ammonium ratios, as plant communities transitioned from N to water limitation. In this context, we tested the hypothesis that ?(15)N(root) xylem sap provides a more direct measure of plant N acquisition than ?(15)N(foliage). We found highly variable offsets between ?(15)N(foliage) and ?(15)N(root) xylem sap, both between taxa at a single site (1.3-3.4 ‰) and within taxa across sites (0.8-3.4 ‰). As a result, ?(15)N(foliage) overlapped between N-fixing Acacia and non-fixing Eucalyptus/Corymbia and could not be used to reliably identify biological N fixation (BNF). However, Acacia ?(15)N(root) xylem sap indicated a decline in BNF with aridity corroborated by absence of root nodules and increasing xylem sap nitrate concentrations and consistent with shifting resource limitation. Acacia dominance at arid sites may be attributed to flexibility in N acquisition rather than BNF capacity. ?(15)N(root) xylem sap showed no evidence of shifting N acquisition in non-mycorrhizal Hakea/Grevillea and indicated only minor shifts in Eucalyptus/Corymbia consistent with enrichment of ?(15)N(soil) and/or decreasing mycorrhizal colonisation with aridity. We propose that ?(15)N(root) xylem sap is a more direct indicator of N source than ?(15)N(foliage), with calibration required before it could be applied to quantify BNF. PMID:25502440

  18. Production of (15)N-labeled ?-amanitin in Galerina marginata.

    PubMed

    Luo, Hong; DuBois, Brandon; Sgambelluri, R Michael; Angelos, Evan R; Li, Xuan; Holmes, Daniel; Walton, Jonathan D

    2015-09-01

    ?-Amanitin is the major causal constituent of deadly Amanita mushrooms that account for the majority of fatal mushroom poisonings worldwide. It is also an important biochemical tool for the study of its target, RNA polymerase II. The commercial supply of this bicyclic peptide comes from Amanita phalloides, the death cap mushroom, which is collected from the wild. Isotopically labeled amanitin could be useful for clinical and forensic applications, but ?-amanitin has not been chemically synthesized and A. phalloides cannot be cultured on artificial medium. Using Galerina marginata, an unrelated saprotrophic mushroom that grows and produces ?-amanitin in culture, we describe a method for producing (15)N-labeled ?-amanitin using growth media containing (15)N as sole nitrogen source. A key to success was preparing (15)N-enriched yeast extract via a novel method designated "glass bead-assisted maturation." In the presence of the labeled yeast extract and (15)N-NH4Cl, ?-amanitin was produced with >97% isotope enrichment. The labeled product was confirmed by HPLC, high-resolution mass spectrometry, and NMR. PMID:26100667

  19. Natural abundance 17O nuclear magnetic resonance and computational modeling studies of lithium based liquid electrolytes

    NASA Astrophysics Data System (ADS)

    Deng, Xuchu; Hu, Mary Y.; Wei, Xiaoliang; Wang, Wei; Chen, Zhong; Liu, Jun; Hu, Jian Zhi

    2015-07-01

    Natural abundance 17O NMR measurements were conducted on electrolyte solutions consisting of Li[CF3SO2NSO2CF3] (LiTFSI) dissolved in the solvents of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and their mixtures at various concentrations. It was observed that 17O chemical shifts of solvent molecules change with the concentration of LiTFSI. The chemical shift displacements of carbonyl oxygen are evidently greater than those of ethereal oxygen, strongly indicating that Li+ ion is coordinated with carbonyl oxygen rather than ethereal oxygen. To understand the detailed molecular interaction, computational modeling of 17O chemical shifts was carried out on proposed solvation structures. By comparing the predicted chemical shifts with the experimental values, it is found that a Li+ ion is coordinated with four double bond oxygen atoms from EC, PC, EMC and TFSI- anion. In the case of excessive amount of solvents of EC, PC and EMC the Li+ coordinated solvent molecules are undergoing quick exchange with bulk solvent molecules, resulting in average 17O chemical shifts. Several kinds of solvation structures are identified, where the proportion of each structure in the liquid electrolytes investigated depends on the concentration of LiTFSI.

  20. Calibration of an elastic recoil setup for D/H-ratios close to natural abundance

    NASA Astrophysics Data System (ADS)

    Ros, L.; Borysiuk, M.; Kristiansson, P.; Abdel, N.; Elfman, M.; Nilsson, E. J. C.; Pallon, J.

    2014-08-01

    Nominally Anhydrous Minerals (NAM) in the Earth's mantle contain trace amounts of hydrogen, as a result of the NAM's ability to incorporate hydroxyl ions. The isotopic composition of these hydrogen reservoirs is for the Earth's crust, well characterized. The knowledge of the isotopic composition of the Earth's interior on the other hand is limited. It is believed that the hydrogen composition in the interior is isotopically heterogeneous and that there may exist several reservoirs of hydrogen, characterized by different deuterium/hydrogen-ratios. Characterization of these hydrogen reservoirs can provide valuable information about the mass transport of hydrogen during the evolution of the planet. In this work we present a variant of the proton-proton scattering technique with which we are capable of performing simultaneous measurements of deuterium and hydrogen. The method has been tested with a 2.9 MeV deuteron beam on a polyethylene standard, with D/H ratio close to the natural abundance, and on a thin sample of Muscovite with a hydrogen concentration of 4800 wt-ppm. This is followed by a discussion about limitations and capabilities of the technique.

  1. Natural abundance deuterium and 18-oxygen effects on the precision of the doubly labeled water method

    NASA Technical Reports Server (NTRS)

    Horvitz, M. A.; Schoeller, D. A.

    2001-01-01

    The doubly labeled water method for measuring total energy expenditure is subject to error from natural variations in the background 2H and 18O in body water. There is disagreement as to whether the variations in background abundances of the two stable isotopes covary and what relative doses of 2H and 18O minimize the impact of variation on the precision of the method. We have performed two studies to investigate the amount and covariance of the background variations. These were a study of urine collected weekly from eight subjects who remained in the Madison, WI locale for 6 wk and frequent urine samples from 14 subjects during round-trip travel to a locale > or = 500 miles from Madison, WI. Background variation in excess of analytical error was detected in six of the eight nontravelers, and covariance was demonstrated in four subjects. Background variation was detected in all 14 travelers, and covariance was demonstrated in 11 subjects. The median slopes of the regression lines of delta2H vs. delta18O were 6 and 7, respectively. Modeling indicated that 2H and 18O doses yielding a 6:1 ratio of final enrichments should minimize this error introduced to the doubly labeled water method.

  2. The Determination of the Natural Abundance of the Isotopes of Chlorine: An Introductory Experiment in Mass Spectrometry.

    ERIC Educational Resources Information Center

    O'Malley, Rebecca M.

    1982-01-01

    Describes a laboratory experiment which introduces basic principles and experimental techniques of mass spectrometry for fourth year undergraduate (B.Sc.) students. Laboratory procedures, background information, and discussion of results are provided for the experiment in which the natural isotopic abundance of chlorine is determined. (Author/JN)

  3. Seasonal variation in natural abundance of 2H and 18O in urine samples from rural Nigeria.

    PubMed

    Harbison, Justin E; Dugas, Lara R; Brieger, William; Tayo, Bamidele O; Alabi, Tunrayo; Schoeller, Dale A; Luke, Amy

    2015-07-01

    The doubly labeled water (DLW) method is used to measure free-living energy expenditure in humans. Inherent to this technique is the assumption that natural abundances of stable isotopes (2)H and (18)O in body water remain constant over the course of the measurement period and after elimination of the loading dose of DLW will return to the same predose level. To determine variability in the natural abundances of (2)H and (18)O in humans living in a region with seasonal shifts in rain patterns and sources of drinking water, over the course of 12 mo we collected weekly urine samples from four individuals living in southwest Nigeria as well as samples of their drinking water. From ongoing regional studies of hypertension, obesity, and energy expenditure, we estimated average water turnover rate, urine volumes, and sodium and potassium excretion. Results suggest that (2)H and (18)O in urine, mean concentrations of urinary sodium and potassium, urine volume, and total body turnover differed significantly from dry to rainy season. Additionally, seasonal weather variables (mean monthly maximum temperatures, total monthly rainfall, and minimum relative humidity) were all significantly associated with natural abundances in urine. No seasonal difference was observed in drinking water samples. Findings suggest that natural abundances in urine may not remain constant as assumed, and studies incorporating DLW measurements across the transition of seasons should interpret results with caution unless appropriate doses of the tracers are used. PMID:25977450

  4. The structural analysis of Cardo silicone polyimides by high resolution solid-state 13C, 15N and 29Si NMR

    NASA Astrophysics Data System (ADS)

    Shinohara, Masaaki; Saito, Koji; Hatakeyama, Moriaki; Yuasa, Masatoshi; Furukawa, Nobuyuki

    1998-01-01

    It is well-known that polymers containing a fluorene moiety (so-called 'Cardo-type polymers') have high thermal stability, good mechanical properties and excellent solubility in common organic solvents. For the benefit of the full use of these polyimides in industrial applications, cross-linked Cardo silicone polyimides, which have both high thermal stability and high resistivity to organic solvents, were designed. The cross-link density was determined by solid-state 13C and 29Si NMR because no other direct method for the determination of the cross-link density is available. Furthermore, natural abundance CPMAS 13C and 15N NMR measurements were made for three different forms of Cardo silicone polyimides which exhibit a high oxygen permselective property. An explanation for the gas separation mechanism is given.

  5. Implications of scaled ?15N fractionation for community predator-prey body mass ratio estimates in size-structured food webs.

    PubMed

    Reum, Jonathan C P; Jennings, Simon; Hunsicker, Mary E

    2015-11-01

    Nitrogen stable isotope ratios (?(15) N) may be used to estimate community-level relationships between trophic level (TL) and body size in size-structured food webs and hence the mean predator to prey body mass ratio (PPMR). In turn, PPMR is used to estimate mean food chain length, trophic transfer efficiency and rates of change in abundance with body mass (usually reported as slopes of size spectra) and to calibrate and validate food web models. When estimating TL, researchers had assumed that fractionation of ?(15) N (??(15) N) did not change with TL. However, a recent meta-analysis indicated that this assumption was not as well supported by data as the assumption that ??(15) N scales negatively with the ?(15) N of prey. We collated existing fish community ?(15) N-body size data for the Northeast Atlantic and tropical Western Arabian Sea with new data from the Northeast Pacific. These data were used to estimate TL-body mass relationships and PPMR under constant and scaled ??(15) N assumptions, and to assess how the scaled ??(15) N assumption affects our understanding of the structure of these food webs. Adoption of the scaled ??(15) N approach markedly reduces the previously reported differences in TL at body mass among fish communities from different regions. With scaled ??(15) N, TL-body mass relationships became more positive and PPMR fell. Results implied that realized prey size in these size-structured fish communities are less variable than previously assumed and food chains potentially longer. The adoption of generic PPMR estimates for calibration and validation of size-based fish community models is better supported than hitherto assumed, but predicted slopes of community size spectra are more sensitive to a given change or error in realized PPMR when PPMR is small. PMID:26046788

  6. Backbone dynamics of barstar: a (15)N NMR relaxation study.

    PubMed

    Sahu, S C; Bhuyan, A K; Majumdar, A; Udgaonkar, J B

    2000-12-01

    Backbone dynamics of uniformly (15)N-labeled barstar have been studied at 32 degrees C, pH 6.7, by using (15)N relaxation data obtained from proton-detected 2D (1)H-(15)N NMR spectroscopy. (15)N spin-lattice relaxation rate constants (R(1)), spin-spin relaxation rate constants (R(2)), and steady-state heteronuclear (1)H-(15)N NOEs have been determined for 69 of the 86 (excluding two prolines and the N-terminal residue) backbone amide (15)N at a magnetic field strength of 14.1 Tesla. The primary relaxation data have been analyzed by using the model-free formalism of molecular dynamics, using both isotropic and axially symmetric diffusion of the molecule, to determine the overall rotational correlation time (tau(m)), the generalized order parameter (S(2)), the effective correlation time for internal motions (tau(e)), and NH exchange broadening contributions (R(ex)) for each residue. As per the axially symmetric diffusion, the ratio of diffusion rates about the unique and perpendicular axes (D( parallel)/D( perpendicular)) is 0.82 +/- 0.03. The two results have only marginal differences. The relaxation data have also been used to map reduced spectral densities for the NH vectors of these residues at three frequencies: 0, omega(H), and omega(N), where omega(H),(N) are proton and nitrogen Larmor frequencies. The value of tau(m) obtained from model-free analysis of the relaxation data is 5.2 ns. The reduced spectral density analysis, however, yields a value of 5.7 ns. The tau(m) determined here is different from that calculated previously from time-resolved fluorescence data (4.1 ns). The order parameter ranges from 0.68 to 0.98, with an average value of 0.85 +/- 0.02. A comparison of the order parameters with the X-ray B-factors for the backbone nitrogens of wild-type barstar does not show any considerable correlation. Model-free analysis of the relaxation data for seven residues required the inclusion of an exchange broadening term, the magnitude of which ranges from 2 to 9.1 s(-1), indicating the presence of conformational averaging motions only for a small subset of residues. PMID:11056034

  7. Natural abundance deuterium nuclear magnetic resonance spectroscopy: Study of the biosynthesis of monoterpenes

    SciTech Connect

    Leopold, M.F.

    1990-01-01

    Deuterium NMR spectroscopy at natural abundance (D NMR-na) is a new technique for exploring the biosynthesis of small molecules such as monoterpenes. The analysis of relative site-specific deuterium integration values is an effective means of measuring isotope effects, and examining the regio- and stereochemistry of biosynthetic reactions. The deuterium integration values of linalyl acetate and limonene isolated from the same source were consistent and showed that proton abstraction from the postulated {alpha}-terpinyl cation intermediate to form limonene is regioselective from the methyl derived from the Cs methyl of the precursor, geranyl diphosphate. This regiochemistry was observed in limonene samples from different sources and the measured primary kinetic isotope effect ranged from 0.25 to in excess of 100 (no deuterium was removed within experimental error). Various {alpha}- and {beta}-pinene samples were isolated and D NMR-na analysis showed evidence of isotopically sensitive partitioning of the pinylcation in the formation of these products. This spectral analysis supported published radiolabeling studies but did not require synthesis of substrates or enzyme purification. The formation of 3-carene occurs without isomerization of the double bond which was previously postulated. The olefinic deuterium of the bicyclic compound was traced to the depleted deuterium at C{sub 2} of isopentyl diphosphate by D NMR-na data and this supported unpublished radiolabeling studies. Study of irregular monoterpenes, chrysanthemyl acetate and lyratyl acetate, showed partitioning of dimethylallyl diphosphate (DMAPP) by chrysanthemyl cyclase. The {alpha}-secondary kinetic isotope effect of 1.06-1.12, obtained from relative deuterium integration values, suggested that S{sub N}1 ionization of one molecule of DMAPP is the first step in the condensation reaction.

  8. Synthesis of 15 alpha-hydroxyestrogen 15-N-acetylglucosaminides.

    PubMed

    Suzuki, E; Namba, S; Kurihara, H; Goto, J; Matsuki, Y; Nambara, T

    1995-03-01

    The synthesis of 15-N-acetylglucosaminides of 15 alpha-hydroxyesterone, 15 alpha-hydroxyestradiol, and 15 alpha-hydroxyestriol (estetrol) is described. The latter two were prepared by condensation of 2-acetamido-1 alpha-chloro-1,2-dideoxy-3,4,6-trio-O-acetyl-D-glucopyranose with appropriately protected 15 alpha-hydroxyestrogens by the Koenigs-Knorr reaction employing cadmium carbonate as a catalyst. Subsequent removal of protecting groups with methanolic potassium hydroxide provided the desired conjugates. 15 alpha-Hydroxyestrone 15-N-acetylglucosaminide was synthesized from the corresponding 15 alpha-hydroxyestradiol derivative by Jones oxidation followed by brief alkaline hydrolysis. These conjugates underwent enzymatic hydrolysis with beta-N-acetylglucosaminidase from Jack beans to produce 15 alpha-hydroxyestrogens. PMID:7792832

  9. Marking Drosophila suzukii (Diptera: Drosophilidae) With Rubidium or 15N.

    PubMed

    Klick, J; Yang, W Q; Bruck, D J

    2015-06-01

    Drosophila suzukii Matsumura (Diptera: Drosophilidae) has caused significant economic damage to berry and stone fruit production regions. Markers that are systemic in plants and easily transferred to target organisms are needed to track D. suzukii exploitation of host resources and trophic interactions. High and low concentrations of the trace element, rubidium (Rb), and the stable isotope, 15N, were tested to mark D. suzukii larvae feeding on fruits of enriched strawberry plants grown in containers under greenhouse conditions. Fly marker content and proportion of flies marked 1, 7, and 14 d after emergence from enriched fruits and fly dry mass were analyzed. Nearly 100% of the flies analyzed 14 d after emerging from 15N-enriched plants were marked, whereas only 30-75% and 0-3% were marked 14 d after emerging from high and low Rb concentration plants, respectively. Rapid Rb decay, strong 15N persistence, and the economics of using these markers in the field to elucidate D. suzukii pest ecology are discussed. PMID:26470275

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

    SciTech Connect

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

    2015-06-22

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

  11. Increased seawater temperature increases the abundance and alters the structure of natural Vibrio populations associated with the coral Pocillopora damicornis

    PubMed Central

    Tout, Jessica; Siboni, Nachshon; Messer, Lauren F.; Garren, Melissa; Stocker, Roman; Webster, Nicole S.; Ralph, Peter J.; Seymour, Justin R.

    2015-01-01

    Rising seawater temperature associated with global climate change is a significant threat to coral health and is linked to increasing coral disease and pathogen-related bleaching events. We performed heat stress experiments with the coral Pocillopora damicornis, where temperature was increased to 31°C, consistent with the 2–3°C predicted increase in summer sea surface maxima. 16S rRNA amplicon sequencing revealed a large shift in the composition of the bacterial community at 31°C, with a notable increase in Vibrio, including known coral pathogens. To investigate the dynamics of the naturally occurring Vibrio community, we performed quantitative PCR targeting (i) the whole Vibrio community and (ii) the coral pathogen Vibrio coralliilyticus. At 31°C, Vibrio abundance increased by 2–3 orders of magnitude and V. coralliilyticus abundance increased by four orders of magnitude. Using a Vibrio-specific amplicon sequencing assay, we further demonstrated that the community composition shifted dramatically as a consequence of heat stress, with significant increases in the relative abundance of known coral pathogens. Our findings provide quantitative evidence that the abundance of potential coral pathogens increases within natural communities of coral-associated microbes as a consequence of rising seawater temperature and highlight the potential negative impacts of anthropogenic climate change on coral reef ecosystems. PMID:26042096

  12. 15N in tree rings as a bio-indicator of changing nitrogen cycling in tropical forests: an evaluation at three sites using two sampling methods

    PubMed Central

    van der Sleen, Peter; Vlam, Mart; Groenendijk, Peter; Anten, Niels P. R.; Bongers, Frans; Bunyavejchewin, Sarayudh; Hietz, Peter; Pons, Thijs L.; Zuidema, Pieter A.

    2015-01-01

    Anthropogenic nitrogen deposition is currently causing a more than twofold increase of reactive nitrogen input over large areas in the tropics. Elevated 15N abundance (?15N) in the growth rings of some tropical trees has been hypothesized to reflect an increased leaching of 15N-depleted nitrate from the soil, following anthropogenic nitrogen deposition over the last decades. To find further evidence for altered nitrogen cycling in tropical forests, we measured long-term ?15N values in trees from Bolivia, Cameroon, and Thailand. We used two different sampling methods. In the first, wood samples were taken in a conventional way: from the pith to the bark across the stem of 28 large trees (the “radial” method). In the second, ?15N values were compared across a fixed diameter (the “fixed-diameter” method). We sampled 400 trees that differed widely in size, but measured ?15N in the stem around the same diameter (20 cm dbh) in all trees. As a result, the growth rings formed around this diameter differed in age and allowed a comparison of ?15N values over time with an explicit control for potential size-effects on ?15N values. We found a significant increase of tree-ring ?15N across the stem radius of large trees from Bolivia and Cameroon, but no change in tree-ring ?15N values over time was found in any of the study sites when controlling for tree size. This suggests that radial trends of ?15N values within trees reflect tree ontogeny (size development). However, for the trees from Cameroon and Thailand, a low statistical power in the fixed-diameter method prevents to conclude this with high certainty. For the trees from Bolivia, statistical power in the fixed-diameter method was high, showing that the temporal trend in tree-ring ?15N values in the radial method is primarily caused by tree ontogeny and unlikely by a change in nitrogen cycling. We therefore stress to account for tree size before tree-ring ?15N values can be properly interpreted. PMID:25914707

  13. Constraining the S factor of 15N(p,g)16O at Astrophysical Energies

    E-print Network

    P. J. LeBlanc; G. Imbriani; J. Goerres; M. Junker; R. Azuma; M. Beard; D. Bemmerer; A. Best; C. Broggini; A. Caciolli; P. Corvisiero; H. Costantini; M. Couder; R. deBoer; Z. Elekes; S. Falahat; A. Formicola; Zs. Fulop; G. Gervino; A. Guglielmetti; C. Gustavino; Gy. Gyurky; F. Kaeppeler; A. Kontos; R. Kuntz; H. Leiste; A. Lemut; Q. Li; B. Limata; M. Marta; C. Mazzocchi; R. Menegazzo; S. O'Brien; A. Palumbo; P. Prati; V. Roca; C. Rolfs; C. Rossi Alvarez; E. Somorjai; E. Stech; O. Straniero; F. Strieder; W. Tan; F. Terrasi; H. P. Trautvetter; E. Uberseder; M. Wiescher

    2010-11-10

    The 15N(p,g)16O reaction represents a break out reaction linking the first and second cycle of the CNO cycles redistributing the carbon and nitrogen abundances into the oxygen range. The reaction is dominated by two broad resonances at Ep = 338 keV and 1028 keV and a Direct Capture contribution to the ground state of 16O. Interference effects between these contributions in both the low energy region (Ep < 338 keV) and in between the two resonances (338 15N(p,g)16O reaction has been remeasured covering the energy range from Ep=1800 keV down to 130 keV. The results have been analyzed in the framework of a multi-level R-matrix theory and a S(0) value of 39.6 keV b has been found.

  14. Direct measurement of the 15N(p,gamma)16O total cross section at novae energies

    E-print Network

    D Bemmerer; A Caciolli; R Bonetti; C Broggini; F Confortola; P Corvisiero; H Costantini; Z Elekes; A Formicola; Zs Fulop; G Gervino; A Guglielmetti; C Gustavino; Gy Gyurky; M Junker; B Limata; M Marta; R Menegazzo; P Prati; V Roca; C Rolfs; C Rossi Alvarez; E Somorjai; O Straniero

    2009-02-04

    The 15N(p,gamma)16O reaction controls the passage of nucleosynthetic material from the first to the second carbon-nitrogen-oxygen (CNO) cycle. A direct measurement of the total 15N(p,gamma)16O cross section at energies corresponding to hydrogen burning in novae is presented here. Data have been taken at 90-230 keV center-of-mass energy using a windowless gas target filled with nitrogen of natural isotopic composition and a bismuth germanate summing detector. The cross section is found to be a factor two lower than previously believed.

  15. Assessment of the natural variation of low abundant metabolic proteins in soybean seeds using proteomics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using two-dimensional polyacrylamide gel electrophoresis and mass spectrometry, we investigated the distribution of the low abundant proteins that are involved in soybean seed development in four wild and twelve cultivated soybean genotypes. We found proteomic variation of these proteins within and...

  16. -Amino acids, although less abundant than their -analogues, are also present in peptides and other natural

    E-print Network

    -Amino acids, although less abundant than their -analogues, are also present in peptides and other. A number of methods for synthesis and transformations leading to -amino acids in diastereomerically and enantiomerically enriched forms have been reported.1 The synthesis of modified peptides containing -amino acids

  17. Cosmic abundance of iron and nature of primitive material in meteorites.

    NASA Technical Reports Server (NTRS)

    Kerridge, J.

    1972-01-01

    Comparison of solar abundance data with bulk analyses of type-I carbonaceous meteorites and microprobe analyses of type-I phyllosilicates. The comparison seems to lend support to Kerridge's (1971) hypothesis that the apparently primitive chemistry of such meteorites may be the result of a major component dominating the analysis and that this component may be unaltered solar system condensate.

  18. An sup 15 N NMR method for the characterization of organic sulfur in coal and coal products via iminosulfurane formation

    SciTech Connect

    Franz, J.A.; Lamb, C.N.; Linehan, J.C.

    1991-09-01

    The indirect of organic sulfur by {sup 15}N NMR spectroscopy in the solid state is feasible by facile reactions providing the iminosulfurane structures. Unfortunately, nitrogen chemical shifts appear to be insufficiently sensitive to the nature of the sulfur substituent to be useful for structural studies. Further work is underway to determine the {sup 15}N chemical shifts of iminosulfuranes formed from dibenzothiophene, 4-4{prime}-dimethoxydiphenyl sulfide, and a sulfur-containing, methylated asphaltene to determine the sensitivity of {sup 15}N shifts to a broader variation of aromatic structure. Although double cross-polarization experiments or rotational echo experiments could make use of iminosulfurane formation for detection of carbon in proximity to sulfur, the difficulties in quantitation using these methods are not encouraging for coal product mixtures. 6 refs., 1 fig., 1 tab.

  19. Toward hyperpolarized molecular imaging of HIV: synthesis and longitudinal relaxation properties of 15N-Azidothymidine

    PubMed Central

    Shchepin, Roman V.; Chekmenev, Eduard Y.

    2015-01-01

    Previously unreported 15N labeled Azidothymidine (AZT) was prepared as an equimolar mixture of two isotopomers: 1-15N-AZT and 3-15N-AZT. Polarization decay of 15N NMR signal was studied in high (9.4 T) and low (~50 mT) magnetic fields. 15N T1 values were 45 ± 5 s (1-15N-AZT) and 37 ± 2 s (3-15N-AZT) at 9.4 T, and 140 ± 16 s (3-15N-AZT) at 50 mT. 15N-AZT can be potentially 15N hyperpolarized by several methods. These sufficiently long 15N-AZT T1 values potentially enable hyperpolarized in vivo imaging of 15N-AZT, because of the known favorable efficient (i.e., of the time scale shorter than the longest reported here 15N T1) kinetics of uptake of injected AZT. Therefore, 3-15N-AZT can be potentially used for HIV molecular imaging using hyperpolarized magnetic resonance imaging. PMID:25156931

  20. Natural Abundance of Mass 47 in CO2 Emitted in Car Exhaust and Human Breath

    NASA Astrophysics Data System (ADS)

    Affek, H. P.; Eiler, J. M.

    2004-12-01

    Atmospheric CO2 is widely studied using records of concentration, ? 13C and ? 18O, although the number and variability of sources and sinks prevents these alone from uniquely defining the budget. CO2 of mass 47 (mainly 13C18O16O) provides an additional potential tracer, but little is known about its ability to differentiate among various budget components. We present study of differences in 13C18O16O abundance between combustion and respiration. We define ? 47 as the difference in permil between the measured R47 (=[mass 47]/[mass 44]) and R47 expected for CO2 whose isotopes are distributed randomly among all isotopologues. Previous studies have shown that ? 47 values at thermodynamic equilibrium vary between zero at 1000\\deg C and 0.9\\permil at room temperature, raising the possibility that it could differentiate between CO2 produced by high temperature processes, such as combustion, and that produced in respiration. Values of ? 47 are non-linear in mixing. Therefore, it is useful to discuss the ? 47=(R47/R47ST-1)1000, where R47ST is the R47 expected for CO2 having ? 13C-VPDB=0, ? 18O-VSMOW=0 and ? 47=0. We used a Keeling plot approach to estimate ? 13C, ? 18O, ? 47 and ? 47 in CO2 from car exhaust and from human breath. Air sampled at 10am in the Caltech campus in Pasadena, CA, varied in CO2 concentration from 383 to 404ppm, in ? 13C and ? 18O from -9.2 to -10.2\\permil and from 40.7 to 42.0\\permil, respectively, in ? 47 of from 32.6 to 34.0\\permil, and in ? 47 from 0.73 to 0.96\\permil. We then sampled at varying distances from a car exhaust pipe. The intercepts in Keeling plots defined by these data, reflecting the car exhaust end-member, were similar to the values obtained very close to the exhaust pipe: ? 13C was found to equal -24.4±0.2\\permil, similar to the measured value of the gasoline used; ? 18O =30.0±0.4\\permil; ? 47=6.7±0.6\\permil; and ? 47=0.41±0.03\\permil. Both ? 18O and ? 47 are consistent with that expected for thermodynamic equilibrium at 200\\deg C between water and CO2 generated by combustion of gasoline-air mixtures. This temperature is lower than that of the catalytic converter, suggesting re-equilibration in the cooling exhaust as it travels through the tail pipe. This can explain why the ? 18O of CO2 from car exhaust is substantially greater than that of O2 in air. Samples of CO2 in human breath had ? 13C and ? 18O values broadly similar to those of car exhaust (-22.3±0.2 and 34.4±0.3\\permil, respectively), ? 47 of 13.5±0.4\\permil, but ? 47 of 0.74±0.02\\permil, far higher than exhaust and similar to that of background Pasadena air. ? 13C of human breath is similar to that of car exhaust, much as other respiration and fossil-fuel sources of CO2 generally overlap. Similarly, ? 18O of human breath and soil respiration are close to that of car exhaust. Therefore, conventional stable isotope constraints do not easily differentiate fossil-fuel and respiratory sources. In contrast, the ? 47 value of CO2 from car exhaust is easily differentiated from those of CO2 in human breath, largely due to enhanced thermodynamic stability of 13C18O16O at the low temperatures characteristic of respiration. Hence, ? 47 is a potentially useful tracer to distinguish anthropogenic, mostly combustion, CO2 sources from natural, low temperature, sources.

  1. Compound-Specific ?15N Amino Acid Measurements in Littoral Mussels in the California Upwelling Ecosystem: A New Approach to Generating Baseline ?15N Isoscapes for Coastal Ecosystems

    PubMed Central

    Vokhshoori, Natasha L.; McCarthy, Matthew D.

    2014-01-01

    We explored ?15N compound-specific amino acid isotope data (CSI-AA) in filter-feeding intertidal mussels (Mytilus californianus) as a new approach to construct integrated isoscapes of coastal primary production. We examined spatial ?15N gradients in the California Upwelling Ecosystem (CUE), determining bulk ?15N values of mussel tissue from 28 sites between Port Orford, Oregon and La Jolla, California, and applying CSI-AA at selected sites to decouple trophic effects from isotopic values at the base of the food web. Bulk ?15N values showed a strong linear trend with latitude, increasing from North to South (from ?7‰ to ?12‰, R2?=?0.759). In contrast, CSI-AA trophic position estimates showed no correlation with latitude. The ?15N trend is therefore most consistent with a baseline ?15N gradient, likely due to the mixing of two source waters: low ?15N nitrate from the southward flowing surface California Current, and the northward transport of the California Undercurrent (CUC), with15N-enriched nitrate. This interpretation is strongly supported by a similar linear gradient in ?15N values of phenylalanine (?15NPhe), the best AA proxy for baseline ?15N values. We hypothesize ?15NPhe values in intertidal mussels can approximate annual integrated ?15N values of coastal phytoplankton primary production. We therefore used ?15NPhe values to generate the first compound-specific nitrogen isoscape for the coastal Northeast Pacific, which indicates a remarkably linear gradient in coastal primary production ?15N values. We propose that ?15NPhe isoscapes derived from filter feeders can directly characterize baseline ?15N values across major biochemical provinces, with potential applications for understanding migratory and feeding patterns of top predators, monitoring effects of climate change, and study of paleo- archives. PMID:24887109

  2. Unveiling the Nature of the "Green Pea" Galaxies: Oxygen and Nitrogen Chemical Abundances

    NASA Astrophysics Data System (ADS)

    Amorín, R. O.; Pérez-Montero, E.; Vílchez, J. M.

    2011-07-01

    We present recent results on the oxygen and nitrogen chemical abundances in the extremely compact, low-mass starburst galaxies at redshifts 0.1-0.3 usually referred to as "green pea" galaxies. We show that they are metal-poor galaxies (~1/5 solar) with lower oxygen abundances than star-forming galaxies of similar mass and N/O ratios unusually high for galaxies of the same metallicity. Recent, rapid, and massive inflows of cold gas, possibly coupled with enriched outflows from supernova winds, are used to explain the results. This is consistent with the known "pea" galaxy properties and suggest that these rare objects are experiencing a short and extreme phase in their evolution.

  3. Nature's Starships. I. Observed Abundances and Relative Frequencies of Amino Acids in Meteorites

    E-print Network

    Cobb, Alyssa K

    2014-01-01

    The class of meteorites called carbonaceous chondrites are examples of material from the solar system which have been relatively unchanged from the time of their initial formation. These meteorites have been classified according to the temperatures and physical conditions of their parent planetesimals. We collate available data on amino acid abundance in these meteorites and plot the concentrations of different amino acids for each meteorite within various meteorite subclasses. We plot average concentrations for various amino acids across meteorites separated by subclass and petrologic type. We see a predominance in the abundance and variety of amino acids in CM2 and CR2 meteorites. The range in temperature corresponding to these subclasses indicates high degrees of aqueous alteration, suggesting aqueous synthesis of amino acids. Within the CM2 and CR2 subclasses, we identify trends in relative frequencies of amino acids to investigate how common amino acids are as a function of their chemical complexity. The...

  4. Nature's starships. I. Observed abundances and relative frequencies of amino acids in meteorites

    SciTech Connect

    Cobb, Alyssa K.; Pudritz, Ralph E. E-mail: pudritz@physics.mcmaster.ca

    2014-03-10

    The class of meteorites called carbonaceous chondrites are examples of material from the solar system which have been relatively unchanged from the time of their initial formation. These meteorites have been classified according to the temperatures and physical conditions of their parent planetesimals. We collate available data on amino acid abundance in these meteorites and plot the concentrations of different amino acids for each meteorite within various meteorite subclasses. We plot average concentrations for various amino acids across meteorites separated by subclass and petrologic type. We see a predominance in the abundance and variety of amino acids in CM2 and CR2 meteorites. The range in temperature corresponding to these subclasses indicates high degrees of aqueous alteration, suggesting aqueous synthesis of amino acids. Within the CM2 and CR2 subclasses, we identify trends in relative frequencies of amino acids to investigate how common amino acids are as a function of their chemical complexity. These two trends (total abundance and relative frequencies) can be used to constrain formation parameters of amino acids within planetesimals. Our organization of the data supports an onion shell model for the temperature structure of planetesimals. The least altered meteorites (type 3) and their amino acids originated near cooler surface regions. The most active amino acid synthesis likely took place at intermediate depths (type 2). The most altered materials (type 1) originated furthest toward parent body cores. This region is likely too hot to either favor amino acid synthesis or for amino acids to be retained after synthesis.

  5. Rotational spectrum of deuterated and 15N ethyl cyanides: CH_3CHDCN and CH_2DCH_2CN and of CH_3CH_2C15N

    NASA Astrophysics Data System (ADS)

    Margulès, L.; Motiyenko, R.; Demyk, K.; Tercero, B.; Cernicharo, J.; Sheng, M.; Weidmann, M.; Gripp, J.; Mäder, H.; Demaison, J.

    2009-01-01

    Context: Ethyl cyanide is an abundant molecule in hot molecular clouds. Its rotational spectrum is very dense and several hundreds of rotational transitions within the ground state have been identified in molecular clouds in the 40-900 GHz frequency range. Lines from 13C isotopically substituted ethyl cyanide were identified in Orion. Aims: To enable the search and the possible detection of other isotopologues of ethyl cyanide in interstellar objects, we have studied the rotational spectrum of deuterated ethyl cyanide: CH2DCH2CN (in-plane and out-of-plane) and CH3CHDCN and the spectrum of 15N substituted ethyl cyanide CH3CH2C15N. Using these experimental data, we have searched for these species in Orion. Methods: The rotational spectrum of each species in the ground state was measured in the microwave and millimeter-submillimeter wavelength range using a waveguide Fourier Transform spectrometer (8-17 GHz) and a source-modulated spectrometer employing backward-wave oscillators (BWOs) (150-260 and 580-660 GHz). More than 300 lines were identified for each species, for J values in the range 71-80 and Ka values in the range 28-31 depending on the isotopologues. The experimental spectra were analyzed using a Watson's Hamiltonian in the A-reduction. Results: From the fitting procedure, accurate spectroscopic constants were derived for each of the species. These new sets of spectroscopic constants enable us to predict reliably the rotational spectrum (lines frequencies and intensities) in the 4-1000 GHz frequency range and for J and Ka up to 80 and 31, respectively. Combined with IRAM 30 m antenna observations of Orion, this experimental study allowed us to detect 15N substituted ethyl cyanide CH3CH2C15N for the first time in Orion. The derived column density and rotational temperature are 1013 cm-2 and 150 K for the plateau and 3 × 1014 cm-2 and 300 K for the hot core. The deuterated species were searched for but were not detected. The upper limit to the column density of each deuterated isotopologues was 1014 cm-2. Full version of Tables [see full textsee full textsee full textsee full text] to [see full textsee full textsee full textsee full text] are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/493/565 Tables [see full textsee full textsee full textsee full text] to [see full textsee full textsee full textsee full text] are only available in electronic form at http://www.aanda.org

  6. Does human activity impact the natural antibiotic resistance background? Abundance of antibiotic resistance genes in 21 Swiss lakes.

    PubMed

    Czekalski, Nadine; Sigdel, Radhika; Birtel, Julia; Matthews, Blake; Bürgmann, Helmut

    2015-08-01

    Antibiotic resistance genes (ARGs) are emerging environmental contaminants, known to be continuously discharged into the aquatic environment via human and animal waste. Freshwater aquatic environments represent potential reservoirs for ARG and potentially allow sewage-derived ARG to persist and spread in the environment. This may create increased opportunities for an eventual contact with, and gene transfer to, human and animal pathogens via the food chain or drinking water. However, assessment of this risk requires a better understanding of the level and variability of the natural resistance background and the extent of the human impact. We have analyzed water samples from 21 Swiss lakes, taken at sampling points that were not under the direct influence of local contamination sources and analyzed the relative abundance of ARG using quantitative real-time PCR. Copy numbers of genes mediating resistance to three different broad-spectrum antibiotic classes (sulfonamides: sul1, sul2, tetracyclines: tet(B), tet(M), tet(W) and fluoroquinolones: qnrA) were normalized to copy numbers of bacterial 16S rRNA genes. We used multiple linear regression to assess if ARG abundance is related to human activities in the catchment, microbial community composition and the eutrophication status of the lakes. Sul genes were detected in all sampled lakes, whereas only four lakes contained quantifiable numbers of tet genes, and qnrA remained below detection in all lakes. Our data indicate higher abundance of sul1 in lakes with increasing number and capacity of wastewater treatment plants (WWTPs) in the catchment. sul2 abundance was rather related to long water residence times and eutrophication status. Our study demonstrates the potential of freshwater lakes to preserve antibiotic resistance genes, and provides a reference for ARG abundance from lake systems with low human impact as a baseline for assessing ARG contamination in lake water. PMID:25913323

  7. Chlorophyll a specific ?14C, ?13C and ?15N values in stream periphyton: implications for aquatic food web studies

    NASA Astrophysics Data System (ADS)

    Ishikawa, N. F.; Yamane, M.; Suga, H.; Ogawa, N. O.; Yokoyama, Y.; Ohkouchi, N.

    2015-07-01

    We determined the isotopic composition of chlorophyll a in periphytic algae attached to a streambed substrate (periphyton). The samples were collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Stable isotope ratios of carbon (?13C) and nitrogen (?15N) and natural radiocarbon abundances (?14C) were measured in chlorophyll a (?13Cchl, ?15Nchl and ?14Cchl) and bulk (?13Cbulk, ?15Nbulk and ?14Cbulk) for periphyton, pure aquatic primary producer (Cladophora sp.) and terrestrial primary producer (Quercus glauca). Periphyton ?13Cbulk and ?13Cchl values did not necessarily correspond to ?13Cbulk for an algal-grazing specialist (Mayfly larva, Epeorus latifolium), suggesting that periphyton ?13C values do not faithfully trace carbon transfer between primary producers and primary consumers. Periphyton ?14Cchl values (-258 ‰ in April and -190 ‰ in October) were slightly lower than ?14Cbulk values (-228 ‰ in April and -179 ‰ in October), but were close to the ?14C value for dissolved inorganic carbon (DIC) (-217 ± 31 ‰), which is a mixture of weathered carbonates (?14C = -1000 ‰) and dissolved atmospheric CO2 (?14C approximately +30 ‰ in 2013). ?14Cchl values were also close to ?14Cbulk for E. latifolium (-215 ‰ in April and -199 ‰ in October) and Cladophora sp. (-210 ‰), whereas the ?14Cbulk value for Q. glauca (+27 ‰) was closer to ?14C for atmospheric CO2. Although the bulk isotopic composition of periphyton is recognised as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89 to 95 % algal carbon (derived from 14C-depleted DIC) and 5 to 11 % terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).

  8. Key words: Airborne measures, gamma-ray spectrometry, isotopic abundance, MCA_Rad system, natural radioactivity,

    E-print Network

    Roma "La Sapienza", Università di

    _Rad system, natural radioactivity, potential natural radioactivity content map, ZaNaI system. INTRODUCTION reports a part of the results of the Research Project "Measurement of natural radioactivity and mapping of Tuscany Region. The aim of this project is to realize the thematic maps of radioactivity content

  9. Using ?15N of Chironomidae as an index of nitrogen sources and processing within watersheds as part of EPA's National Aquatic Resource Surveys

    NASA Astrophysics Data System (ADS)

    Brooks, J. R.; Compton, J.; Herlihy, A.; Sobota, D. J.; Stoddard, J.; Weber, M.

    2014-12-01

    Nitrogen (N) removal in watersheds is an important regulating ecosystem service that can help reduce N pollution in the nation's waterways. However, processes that remove N such as denitrification are generally determined at point locations. Measures that integrate N processing within watersheds and over time would be particularly useful for assessing the degree of this vital service. Because most N removal processes isotopically enrich the N remaining, ?15N from basal food-chain organisms in aquatic ecosystems can provide information on watershed N processing. As part of EPA's National Aquatic Resource Surveys (NARS), we measured ?15N of Chironomidae in lakes, rivers and streams because these larval aquatic insects were found in abundance in almost every lake and stream in the U.S. Using information on nitrogen loading to the watershed, and total N concentrations within the water, we assessed when elevated chironomid ?15N would indicate N removal rather than possible enriched sources of N. Chironomid ?15N values ranged from -4 to +20 ‰, and were higher in rivers and streams than in lakes (median = 7.6 ‰ vs. 4.8 ‰, respectively), indicating that N was processed to a greater degree in lotic chironomids than in lentic ones. For both, ?15N increased with watershed-level agricultural land cover and N loading, and decreased as precipitation increased. In rivers and streams with high synthetic N loading, we found lower N concentrations in streams with higher chironomid ?15N values, suggesting greater N removal. At low levels of synthetic N loading, the pattern reversed, and streams with enriched chironomid ?15N had higher N concentrations, suggesting enriched sources such as manure or sewage. Our results indicate that chironomid ?15N values can provide valuable information about watershed-level N inputs and processing for national water quality monitoring efforts.

  10. Sensitivity of D15 N of nitrate, surface suspended and deep sinking

    E-print Network

    Sigman, Daniel M.

    Sensitivity of D15 N of nitrate, surface suspended and deep sinking particulate nitrogen by summertime ammonium recycling. Deep sediment trap PN d15 N also displayed seasonal decreases (from $4 to $1 balance between net nitrate supply and exported PN that links sinking flux d15 N to nitrate utilization

  11. Compound specific amino acid ?15N in marine sediments: A new approach for studies of the marine nitrogen cycle

    NASA Astrophysics Data System (ADS)

    Batista, Fabian C.; Ravelo, A. Christina; Crusius, John; Casso, Michael A.; McCarthy, Matthew D.

    2014-10-01

    The nitrogen (N) isotopic composition (?15N) of bulk sedimentary N (?15Nbulk) is a common tool for studying past biogeochemical cycling in the paleoceanographic record. Empirical evidence suggests that natural fluctuations in the ?15N of surface nutrient N are reflected in the ?15N of exported planktonic biomass and in sedimentary ?15Nbulk. However, ?15Nbulk is an analysis of total combustible sedimentary N, and therefore also includes mixtures of N sources and/or selective removal or preservation of N-containing compounds. Compound-specific nitrogen isotope analyses of individual amino acids (?15NAA) are novel measurements with the potential to decouple ?15N changes in nutrient N from trophic effects, two main processes that can influence ?15Nbulk records. As a proof of concept study to examine how ?15NAA can be applied in marine sedimentary systems, we compare the ?15NAA signatures of surface and sinking POM sources with shallow surface sediments from the Santa Barbara Basin, a sub-oxic depositional environmental that exhibits excellent preservation of sedimentary organic matter. Our results demonstrate that ?15NAA signatures of both planktonic biomass and sinking POM are well preserved in such surface sediments. However, we also observed an unexpected inverse correlation between ?15N value of phenylalanine (?15NPhe; the best AA proxy for N isotopic value at the base of the food web) and calculated trophic position. We used a simple N isotope mass balance model to confirm that over long time scales, ?15NPhe values should in fact be directly dependent on shifts in ecosystem trophic position. While this result may appear incongruent with current applications of ?15NAA in food webs, it is consistent with expectations that paleoarchives will integrate N dynamics over much longer timescales. We therefore propose that for paleoceanographic applications, key ?15NAA parameters are ecosystem trophic position, which determines relative partitioning of 15N into source AA versus trophic AA pools, and the integrated ?15NAA of all common protein AA (?15NTHAA), which serves as a proxy for the ?15N of nutrient N. Together, we suggest that these can provide a coupled picture of regime shifts in planktonic ecosystem structure, ?15N at the base of food webs, and possibly additional information about nutrient dynamics.

  12. Paleobiological Implications of the Isotopic Signatures ( 13C, 15N) of Fossil Mammal Collagen in Scladina Cave (Sclayn, Belgium)

    NASA Astrophysics Data System (ADS)

    Bocherens, Hervé; Billiou, Daniel; Patou-Mathis, Marylène; Bonjean, Dominique; Otte, Marcel; Mariotti, André

    1997-11-01

    An isotopic investigation of upper Pleistocene mammal bones and teeth from Scladina cave (Sclayn, Belgium) demonstrated the very good quality of collagen preservation. A preliminary screening of the samples used the amount of nitrogen in whole bone and dentine in order to estimate the preserved amount of collagen before starting the extraction process. The isotopic abundances of fossil specimens from still-extant species are consistent with their trophic position. Moreover, the 15N isotopic abundance is higher in dentine than in bone in bears and hyenas, a phenomenon already observed in modern specimens. These results demonstrate that the isotopic compositions of samples from Scladina cave can be interpreted in ecological terms. Mammoths exhibit a high 15N isotopic abundance relative to other herbivores, as was the case in Siberian and Alaskan samples. These results suggest distinctive dietary adaptations in herbivores living in the mammoth steppe. Cave bears are clearly isotopically different from coeval brown bears, suggesting an ecological separation between species, with a pure vegetarian diet for cave bear and an omnivorous diet for brown bear.

  13. Dynamic Nuclear Polarization NMR Enables the Analysis of Sn-Beta Zeolite Prepared with Natural Abundance 119Sn Precursors

    PubMed Central

    2015-01-01

    The catalytic activity of tin-containing zeolites, such as Sn-Beta, is critically dependent on the successful incorporation of the tin metal center into the zeolite framework. However, synchrotron-based techniques or solid-state nuclear magnetic resonance (ssNMR) of samples enriched with 119Sn isotopes are the only reliable methods to verify framework incorporation. This work demonstrates, for the first time, the use of dynamic nuclear polarization (DNP) NMR for characterizing zeolites containing ?2 wt % of natural abundance Sn without the need for 119Sn isotopic enrichment. The biradicals TOTAPOL, bTbK, bCTbK, and SPIROPOL functioned effectively as polarizing sources, and the solvent enabled proper transfer of spin polarization from the radical’s unpaired electrons to the target nuclei. Using bCTbK led to an enhancement (?) of 75, allowing the characterization of natural-abundance 119Sn-Beta with excellent signal-to-noise ratios in <24 h. Without DNP, no 119Sn resonances were detected after 10 days of continuous analysis. PMID:24697321

  14. 15N2 formation and fast oxygen isotope exchange during pulsed 15N18O exposure of MnOx/CeO2

    SciTech Connect

    Kwak, Ja Hun; Szanyi, Janos

    2014-12-23

    Pulsing 15N18O onto an annealed 1% Mn16Ox/Ce16O2 catalyst resulted in very fast oxygen isotope exchange and 15N2 formation at 295 K. In the 1st 15N18O pulse, due to the presence of large number of surface oxygen defects, extensive 15N218O and 15N2 formations were observed. In subsequent pulses oxygen isotope exchange dominated as a result of highly labile oxygen in the oxide. We gratefully acknowledge the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy/Vehicle Technologies Program for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  15. Synthesis of 13C and 15N labeled 2,4-dinitroanisole.

    PubMed

    Jagadish, Bhumasamudram; Field, Jim A; Chorover, Jon; Sierra-Alvarez, Reyes; Abrell, Leif; Mash, Eugene A

    2014-05-30

    Syntheses of [(13)C6]-2,4-dinitroanisole (ring-(13)C6) from [(13)C6]-anisole (ring-(13)C6) and [(15)N2]-2,4-dinitroanisole from anisole using in situ generated acetyl nitrate and [(15)N]-acetyl nitrate, respectively, are described. Treatment of [(13)C6]-anisole (ring-(13)C6) with acetyl nitrate generated in 100% HNO3 gave [(13)C6]-2,4-dinitroanisole (ring-(13)C6) in 83% yield. Treatment of anisole with [(15)N]-acetyl nitrate generated in 10?N [(15)N]-HNO3 gave [(15)N2 ]-2,4-dinitroanisole in 44% yield after two cycles of nitration. Byproducts in the latter reaction included [(15)N]-2-nitroanisole and [(15)N]-4-nitroanisole. PMID:24596018

  16. Changes in the natural abundance of 13 in breath due to lipopolysacchride-induced acute

    E-print Network

    Turner, Monica G.

    that includes the mobilization of amino acids from muscle tissue (net muscle protein breakdown was increased critical for survival, from restricted chickens was found to become naturally enriched with 13 C compared with ad libitum fed chickens. This observation implies that frac- tionation (discrimination of the 13 C

  17. Nitrate dynamics in natural plants: insights based on the concentration and natural isotope abundances of tissue nitrate

    PubMed Central

    Liu, Xue-Yan; Koba, Keisuke; Makabe, Akiko; Liu, Cong-Qiang

    2014-01-01

    The dynamics of nitrate (NO?3), a major nitrogen (N) source for natural plants, has been studied mostly through experimental N addition, enzymatic assay, isotope labeling, and genetic expression. However, artificial N supply may not reasonably reflect the N strategies in natural plants because NO?3 uptake and reduction may vary with external N availability. Due to abrupt application and short operation time, field N addition, and isotopic labeling hinder the elucidation of in situ NO?3-use mechanisms. The concentration and natural isotopes of tissue NO?3 can offer insights into the plant NO?3 sources and dynamics in a natural context. Furthermore, they facilitate the exploration of plant NO?3 utilization and its interaction with N pollution and ecosystem N cycles without disturbing the N pools. The present study was conducted to review the application of the denitrifier method for concentration and isotope analyses of NO?3 in plants. Moreover, this study highlights the utility and advantages of these parameters in interpreting NO?3 sources and dynamics in natural plants. We summarize the major sources and reduction processes of NO?3 in plants, and discuss the implications of NO?3 concentration in plant tissues based on existing data. Particular emphasis was laid on the regulation of soil NO?3 and plant ecophysiological functions in interspecific and intra-plant NO?3 variations. We introduce N and O isotope systematics of NO?3 in plants and discuss the principles and feasibilities of using isotopic enrichment and fractionation factors; the correlation between concentration and isotopes (N and O isotopes: ?18O and ?17O); and isotope mass-balance calculations to constrain sources and reduction of NO?3 in possible scenarios for natural plants are deliberated. Finally, we offer a preliminary framework of intraplant ?18O-NO?3 variation, and summarize the uncertainties in using tissue NO?3 parameters to interpret plant NO?3 utilization. PMID:25101106

  18. Inferring the nature of anthropogenic threats from long-term abundance records.

    PubMed

    Shoemaker, Kevin T; Akçakaya, H Resit

    2015-02-01

    Diagnosing the processes that threaten species persistence is critical for recovery planning and risk forecasting. Dominant threats are typically inferred by experts on the basis of a patchwork of informal methods. Transparent, quantitative diagnostic tools would contribute much-needed consistency, objectivity, and rigor to the process of diagnosing anthropogenic threats. Long-term census records, available for an increasingly large and diverse set of taxa, may exhibit characteristic signatures of specific threatening processes and thereby provide information for threat diagnosis. We developed a flexible Bayesian framework for diagnosing threats on the basis of long-term census records and diverse ancillary sources of information. We tested this framework with simulated data from artificial populations subjected to varying degrees of exploitation and habitat loss and several real-world abundance time series for which threatening processes are relatively well understood: bluefin tuna (Thunnus maccoyii) and Atlantic cod (Gadus morhua) (exploitation) and Red Grouse (Lagopus lagopus scotica) and Eurasian Skylark (Alauda arvensis) (habitat loss). Our method correctly identified the process driving population decline for over 90% of time series simulated under moderate to severe threat scenarios. Successful identification of threats approached 100% for severe exploitation and habitat loss scenarios. Our method identified threats less successfully when threatening processes were weak and when populations were simultaneously affected by multiple threats. Our method selected the presumed true threat model for all real-world case studies, although results were somewhat ambiguous in the case of the Eurasian Skylark. In the latter case, incorporation of an ancillary source of information (records of land-use change) increased the weight assigned to the presumed true model from 70% to 92%, illustrating the value of the proposed framework in bringing diverse sources of information into a common rigorous framework. Ultimately, our framework may greatly assist conservation organizations in documenting threatening processes and planning species recovery. PMID:25065712

  19. New method for estimating bacterial cell abundances in natural samples by use of sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Cleaves, H. James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L.

    2004-01-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.

  20. Dietary fibre-rich resistant starches promote ammonia detoxification in the human colon as measured by lactose-[(15)N2]ureide.

    PubMed

    Wutzke, Klaus D; Tisztl, Michael; Salewski, Birgit; Glass, Änne

    2015-12-01

    Three resistant starches (RSs), namely fibre of potatoes (FP), wrinkle pea starch (WPS), and high amylose maize starch (HAMS) with different dietary fibre contents, were supplemented in adults to evaluate their effects on urinary nitrogen and ammonia excretion as well as on faecal nitrogen excretion by means of lactose-[(15)N2]ureide ((15)N-LU) degradation. Twenty subjects received a regular diet either without or with the supplementation of FP, WPS, and HAMS in a randomized order. After administration of (15)N-LU, urine and faeces were collected over 48 and 72 h, respectively, whereas blood was collected after 6 h. The (15)N-abundances were measured by isotope ratio mass spectrometry. In comparison to the dry run, supplementation with RS significantly lowered renal (15)N-excretion (dry run: 43.2?%, FP: 34.6?%, WPS: 37.9?%, HAMS: 36.4?%) as well as the corresponding (15)NH3-excretion (dry run: 0.08?%, FP: 0.06?%, HAMS: 0.05?%), clearly indicating a reduced colonic nitrogen generation at high dietary fibre intake. PMID:26499512

  1. Resolving the bulk ? 15N values of ancient human and animal bone collagen via compound-specific nitrogen isotope analysis of constituent amino acids

    NASA Astrophysics Data System (ADS)

    Styring, Amy K.; Sealy, Judith C.; Evershed, Richard P.

    2010-01-01

    Stable nitrogen isotope analysis is a fundamental tool in assessing dietary preferences and trophic positions within contemporary and ancient ecosystems. In order to assess more fully the dietary contributions to human tissue isotope values, a greater understanding of the complex biochemical and physiological factors which underpin bulk collagen ? 15N values is necessary. Determinations of ? 15N values of the individual amino acids which constitute bone collagen are necessary to unravel these relationships, since different amino acids display different ? 15N values according to their biosynthetic origins. A range of collagen isolates from archaeological faunal and human bone ( n = 12 and 11, respectively), representing a spectrum of terrestrial and marine protein origins and diets, were selected from coastal and near-coastal sites at the south-western tip of Africa. The collagens were hydrolysed and ? 15N values of their constituent amino acids determined as N-acetylmethyl esters (NACME) via gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). The analytical approach employed accounts for 56% of bone collagen nitrogen. Reconstruction of bulk bone collagen ? 15N values reveals a 2‰ offset from bulk collagen ? 15N values which is attributable to the ? 15N value of the amino acids which cannot currently be determined by GC-C-IRMS, notably arginine which comprises 53% of the nitrogen unaccounted for (23% of the total nitrogen). The ? 15N values of individual amino acids provide insights into both the contributions of various amino acids to the bulk ? 15N value of collagen and the factors influencing trophic position and the nitrogen source at the base of the food web. The similarity in the ? 15N values of alanine, glutamate, proline and hydroxyproline reflects the common origin of their amino groups from glutamate. The depletion in the ? 15N value of threonine with increasing trophic level indicates a fundamental difference between the biosynthetic pathway of threonine and the other amino acids. The ? 15N value of phenylalanine does not change significantly with trophic level, reflecting its conservative nature as an essential amino acid, and thus represents the isotopic composition of the nitrogen at the base of the food web. ? 15N Glu-Phe values in particular are shown to reflect trophic level nitrogen sources within a food web. In relation to the reconstruction of ancient human diet the contribution of marine and terrestrial protein are strongly reflected in ? 15N Glu-Phe values. Differences in nitrogen metabolism are also shown to have an influence upon individual amino acid ? 15N values with ? 15N Glu-Phe values emphasising differences between the different physiological adaptations. The latter is demonstrated in tortoises, which can excrete nitrogen in the form of uric acid and urea and display negative ? 15N Glu-Phe values whereas those for marine and terrestrial mammals are positive. The findings amplify the potential advantages of compound-specific nitrogen isotope analysis in the study of nitrogen flow within food webs and in the reconstruction of past human diets.

  2. Coffinite, USiO4, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?

    PubMed

    Mesbah, Adel; Szenknect, Stephanie; Clavier, Nicolas; Lozano-Rodriguez, Janeth; Poinssot, Christophe; Den Auwer, Christophe; Ewing, Rodney C; Dacheux, Nicolas

    2015-07-20

    Coffinite, USiO4, is the second most abundant U(4+) mineral on Earth, and its formation by the alteration of the UO2 in spent nuclear fuel in a geologic repository may control the release of radionuclides to the environment. Despite its abundance in nature, the synthesis and characterization of coffinite have eluded researchers for decades. On the basis of the recent synthesis of USiO4, we can now define the experimental conditions under which coffinite is most efficiently formed. Optimal formation conditions are defined for four parameters: pH, T, heating time, and U/Si molar ratio. The adjustment of pH between 10 and 12 leads probably to the formation of a uranium(IV) hydroxo-silicate complex that acts as a precursor of uranium(IV) silicate colloids and then of coffinite. Moreover, in this pH range, the largest yield of coffinite formation (as compared with those of the two competing byproduct phases, nanometer-scale UO2 and amorphous SiO2) is obtained for 250 °C, 7 days, and 100% excess silica. PMID:26145720

  3. A New Method for Estimating Bacterial Abundances in Natural Samples using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Cleaves, H. James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L.

    2004-01-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert were heated to a temperature of 500 C for several seconds under reduced pressure. The sublimate was collected on a cold finger and the amount of adenine released from the samples then determined by high performance liquid chromatography (HPLC) with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approx. l0(exp 5) to l0(exp 9) E. coli cell equivalents per gram. For most of these samples, the sublimation based cell counts were in agreement with total bacterial counts obtained by traditional DAPI staining. The simplicity and robustness of the sublimation technique compared to the DAPI staining method makes this approach particularly attractive for use by spacecraft instrumentation. NASA is currently planning to send a lander to Mars in 2009 in order to assess whether or not organic compounds, especially those that might be associated with life, are present in Martian surface samples. Based on our analyses of the Atacama Desert soil samples, several million bacterial cells per gam of Martian soil should be detectable using this sublimation technique.

  4. Determination of ?18O and ?15N in Nitrate

    USGS Publications Warehouse

    Revesz, K.; Böhlke, J.K.; Yoshinari, T.

    1997-01-01

    The analyses of both O and N isotopic compositions of nitrate have many potential applications in studies of nitrate sources and reactions in hydrology, oceanography, and atmospheric chemistry, but simple and precise methods for these analyses have yet to be developed. Testing of a new method involving reaction of potassium nitrate with catalyzed graphite (C + Pd + Au) at 520 °C resulted in quantitative recovery of N and O from nitrate as free CO2, K2CO3, and N2. The ?18O values of nitrate reference materials were obtained by analyzing both the CO2 and K2CO3 from catalyzed graphite combustion. Provisional values of ?18OVSMOW for the internationally distributed KNO3 reference materials IAEA-N3 and USGS-32 were both equal to +22.7 ± 0.5‰. Because the fraction of free CO2 and the isotopic fractionation factor between CO2 and K2CO3 were constant in the combustion products, the ?18O value of KNO3 could be calculated from measurements of the ?18O of free CO2. Thus, ?18OKNO3 = a?18Ofree?CO2 ? b, where a and b were equal to 0.9967 and 3.3, respectively, for the specific conditions of the experiments. The catalyzed graphite combustion method can be used to determine ?18O of KNO3 from measurements of ?18O of free CO2 with reproducibility on the order of ±0.2‰ or better if local reference materials are prepared and analyzed with the samples. Reproducibility of ?15N was ±0.1‰ after trace amounts of CO were removed.

  5. Stable Isotope Probing with 15N Achieved by Disentangling the Effects of Genome G+C Content and Isotope Enrichment on DNA Density? †

    PubMed Central

    Buckley, Daniel H.; Huangyutitham, Varisa; Hsu, Shi-Fang; Nelson, Tyrrell A.

    2007-01-01

    Stable isotope probing (SIP) of nucleic acids is a powerful tool that can identify the functional capabilities of noncultivated microorganisms as they occur in microbial communities. While it has been suggested previously that nucleic acid SIP can be performed with 15N, nearly all applications of this technique to date have used 13C. Successful application of SIP using 15N-DNA (15N-DNA-SIP) has been limited, because the maximum shift in buoyant density that can be achieved in CsCl gradients is approximately 0.016 g ml?1 for 15N-labeled DNA, relative to 0.036 g ml?1 for 13C-labeled DNA. In contrast, variation in genome G+C content between microorganisms can result in DNA samples that vary in buoyant density by as much as 0.05 g ml?1. Thus, natural variation in genome G+C content in complex communities prevents the effective separation of 15N-labeled DNA from unlabeled DNA. We describe a method which disentangles the effects of isotope incorporation and genome G+C content on DNA buoyant density and makes it possible to isolate 15N-labeled DNA from heterogeneous mixtures of DNA. This method relies on recovery of “heavy” DNA from primary CsCl density gradients followed by purification of 15N-labeled DNA from unlabeled high-G+C-content DNA in secondary CsCl density gradients containing bis-benzimide. This technique, by providing a means to enhance separation of isotopically labeled DNA from unlabeled DNA, makes it possible to use 15N-labeled compounds effectively in DNA-SIP experiments and also will be effective for removing unlabeled DNA from isotopically labeled DNA in 13C-DNA-SIP applications. PMID:17369331

  6. Factors Driving the Abundance of Ixodes ricinus Ticks and the Prevalence of Zoonotic I. ricinus-Borne Pathogens in Natural Foci

    PubMed Central

    Fernández-de-Mera, Isabel G.; Acevedo, Pelayo; Gortázar, Christian; de la Fuente, José

    2012-01-01

    Environmental factors may drive tick ecology and therefore tick-borne pathogen (TBP) epidemiology, which determines the risk to animals and humans of becoming infected by TBPs. For this reason, the aim of this study was to analyze the influence of environmental factors on the abundance of immature-stage Ixodes ricinus ticks and on the prevalence of two zoonotic I. ricinus-borne pathogens in natural foci of endemicity. I. ricinus abundance was measured at nine sites in the northern Iberian Peninsula by dragging the vegetation with a cotton flannelette, and ungulate abundance was measured by means of dung counts. In addition to ungulate abundance, data on variables related to spatial location, climate, and soil were gathered from the study sites. I. ricinus adults, nymphs, and larvae were collected from the vegetation, and a representative subsample of I. ricinus nymphs from each study site was analyzed by PCR for the detection of Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum DNA. Mean prevalences of these pathogens were 4.0% ± 1.8% and 20.5% ± 3.7%, respectively. Statistical analyses confirmed the influence of spatial factors, climate, and ungulate abundance on I. ricinus larva abundance, while nymph abundance was related only to climate. Interestingly, cattle abundance rather than deer abundance was the main driver of B. burgdorferi sensu lato and A. phagocytophilum prevalence in I. ricinus nymphs in the study sites, where both domestic and wild ungulates coexist. The increasing abundance of cattle seems to increase the risk of other hosts becoming infected by A. phagocytophilum, while reducing the risk of being infected by B. burgdorferi sensu lato. Controlling ticks in cattle in areas where they coexist with wild ungulates would be more effective for TBP control than reducing ungulate abundance. PMID:22286986

  7. Sources of ?15N variability in sinking particulate nitrogen in the Cariaco Basin, Venezuela

    NASA Astrophysics Data System (ADS)

    Montes, Enrique; Thunell, Robert; Muller-Karger, Frank E.; Lorenzoni, Laura; Tappa, Eric; Troccoli, Luis; Astor, Yrene; Varela, Ramón

    2013-09-01

    Ten years of monthly observations of the ?15N of sinking particulate nitrogen (?15N-PN (in ‰ versus atmospheric N2)=[(15N/14N)sample/(15N/14N)standard)-1]1000) in the Cariaco Basin, Venezuela, confirm that the basin's bottom sediments store information about nitrogen dynamics related to seasonal and interannual variability in regional surface ocean processes. During the upwelling period of the southern Caribbean Sea (February-April), the ?15N-PN is similar to that of the thermocline nitrate (˜3.5‰). This nitrate is imported into the Cariaco Basin with Subtropical Underwater (SUW), which wells up near the coast. Thus, particles generated by phytoplankton photosynthesis during this productive period bear a sub-tropical North Atlantic isotopic imprint of N2 fixation (low compared to the global average of nitrate ?15N?5‰). During the non-upwelling period when surface waters are stratified (September-November), the ?15N-PN is also 3.5-4.0‰, and reflects a mixture of local N2 fixation within the mixed layer, inputs of terrigenous organic matter and SUW nitrate consumption by phytoplankton below the mixed layer, which most likely exerts the strongest control on the ?15N-PN signal during this time. In the transition periods of May-July and December-January, the ?15N-PN increases to 4.5-6.5‰. This coincides with maxima of continental material fluxes (terrestrial PON ?15N is >6‰) into the Cariaco Basin. The ?15N signal in the sediments of the Cariaco Basin thus provides information about the relative strength of the local coastal upwelling, the relative input of continental material via river runoff, and local N2 fixation. The findings contribute to interpretations of the basin's paleoclimatic nitrogen cycle variations based on observations of the sedimentary ?15N record at this location.

  8. Soil processes drive seasonal variation in retention of 15N tracers in a deciduous forest catchment.

    PubMed

    Goodale, Christine L; Fredriksen, Guinevere; Weiss, Marissa S; McCalley, K; Sparks, Jed P; Thomas, Steven A

    2015-10-01

    Seasonal patterns of stream nitrate concentration have long been interpreted as demonstrating the central role of plant uptake in regulating stream nitrogen loss from forested catchments. Soil processes are rarely considered as important drivers of these patterns. We examined seasonal variation in N retention in a deciduous forest using three whole-ecosystem 15N tracer additions: in late April (post-snowmelt, pre-leaf-out), late July (mid-growing- season), and late October (end of leaf-fall). We expected that plant 15N uptake would peak in late spring and midsummer, that immobilization in surface litter and soil would peak the following autumn leaf-fall, and that leaching losses would vary inversely with 15N retention. Similar to most other 15N tracer studies, we found that litter and soils dominated ecosystem retention of added 15N. However, 15N recovery in detrital pools varied tremendously by season, with > 90% retention in spring and autumn and sharply reduced 15N retention in late summer. During spring, over half of the 15N retained in soil occurred within one day in the heavy (mineral-associated) soil fraction. During summer, a large decrease in 15N retention one week after addition coincided with increased losses of 15NO3- to soil leachate and seasonal increases in soil and stream NO3- concentrations, although leaching accounted for only a small fraction of the lost 15N (< 0.2%). Uptake of 15N into roots did not vary by season and accounted for < 4% of each tracer addition. Denitrification or other processes that lead to N gas loss may have consumed the rest. These measurements of 15N movement provide strong evidence for the dominant role of soil processes in regulating seasonal N retention and losses in this catchment and perhaps others with similar soils. PMID:26649387

  9. Effects of climate on deer bone ?15N and ?13C: Lack of precipitation effects on ?15N 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 ?15N and ?13C 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 ?15N and local amount of precipitation. Results presented here similarly show an increase in ?15N 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 ?13C 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 ?15N which correlate with amount of precipitation. Only when deer deviated from their normal feeding pattern by consuming C 4 plants or grasses did their ?15N 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 ?15N 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).

  10. Complete Measurement of Stable Isotopes in N2O (?15N, ?15N?, ?15N?, ?18O, ?17O) Using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS)

    NASA Astrophysics Data System (ADS)

    Leen, J. B.; Gupta, M.

    2014-12-01

    Nitrate contamination in water is a worldwide environmental problem and source apportionment is critical to managing nitrate pollution. Fractionation caused by physical, chemical and biological processes alters the isotope ratios of nitrates (15N/14N, 18O/16O and 17O/16O) and biochemical nitrification and denitrification impart different intramolecular site preference (15N14NO vs. 14N15NO). Additionally, atmospheric nitrate is anomalously enriched in 17O compared to other nitrate sources. The anomaly (?17O) is conserved during fractionation processes, providing a tracer of atmospheric nitrate. All of these effects can be used to apportion nitrate in soil. Current technology for measuring nitrate isotopes is complicated and costly - it involves conversion of nitrate to nitrous oxide (N2O), purification, preconcentration and measurement by isotope ratio mass spectrometer (IRMS). Site specific measurements require a custom IRMS. There is a pressing need to make this measurement simpler and more accessible. Los Gatos Research has developed a next generation mid-infrared Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) analyzer to quantify all stable isotope ratios of N2O (?15N, ?15N?, ?15N?, ?18O, ?17O). We present the latest performance data demonstrating the precision and accuracy of the OA-ICOS based measurement. At an N2O concentration of 322 ppb, the analyzer quantifies [N2O], ?15N, ?15Na, ?15Nb, and ?18O with a precision of ±0.05 ppb, ±0.4 ‰, ±0.45 ‰, and ±0.6 ‰, and ±0.8 ‰ respectively (1?, 100s; 1?, 1000s for ?18O). Measurements of gas standards demonstrate accuracy better than ±1 ‰ for isotope ratios over a wide dynamic range (200 - 100,000 ppb). The measurement of ?17O requires a higher concentration (1 - 50 ppm), easily obtainable through conversion of nitrates in water. For 10 ppm of N2O, the instrument achieves a ?17O precision of ±0.05 ‰ (1?, 1000s). This performance is sufficient to quantify atmospheric nitrate in soil and groundwater and may be used to differentiate other sources of nitrate for which the range of ?17O values is much smaller. By measuring ?15N, ?15N?, ?15N?, ?18O and ?17O, our instrument will help researchers unravel the complicated nitrate mixing problem to determine the sources and sinks of nitrate pollution.

  11. Sources of material for 'loess' deposits at 15°N in North Africa

    NASA Astrophysics Data System (ADS)

    McLaren, Sue; Smalley, Ian; O'Hara-Dhand, Ken

    2014-05-01

    Africa is not a loess-rich continent. Lacking are the large expanses of glacial terrain and the high cold mountain regions, which would have provided the material and processes for loess deposits. African geomorphology and climatic history did not favour the formation of major loess deposits. However, within the African setting there are situations which could lead to particle formation and loess deposition. Loess deposits are made from 'large' dust (i.e. particles around 30µm). Small dust (around 3µm) is generated in large amounts in Africa, and distributed over large distances. Large dust is not generated in significant amounts in Africa, and this accounts for the relative lack of loess deposits. It is a relative lack; examination of the map of loess distribution in the World by Scheidig 1934 (still the best world loess map) shows some possible loess in Africa. In particular there is a band across the continent at around 15°N. We propose some possible sources for this material, and fit these sources into a recently revised deterministic model of loess deposit formation. And look at some exotic but possible indicators of the loessic nature of the 15°N band. Three possible material sources are: (1). The Fonta-Djalon highlands to the west of the loess band, (2). The Bodélé Depression, towards the centre of the loess band, and (3). The Ethiopian highlands to the east. There is a convenient river associated with the loess band; the Niger rises in the Fonta-Djalon region and carries material through the loess zone. The catchment of the Niger is well placed to receive large dust material from the Bodélé depression. Most Bodélé material is small dust carried away in high suspension but small amounts of large dust could be transported to the Niger catchment. Material from the Ethiopian highlands makes up the Nile silt but again some could be transported to the west to contribute to the loess band- which is a modest loess deposit. The deposit can be examined with respect to the deterministic model of loess deposit formation which sets out four event aspects which must be accommodated. PTDC: provenance (of material), transportation, deposition and change- all need to be considered when loess deposit genesis is examined. In the case of the 15°N loess the P actions are speculative, and probably not very effective. In fact the deposits they deliver, as mapped by Scheidig, still have to be established as genuine loess. There are indicators of loessic nature; one is that they are favoured by tunnel nesting birds, in particular bee-eaters. Merops apiaster (the European bee-eater) travels large distances to nest in the European loess. The bee-eater nesting zones map nicely on to European loess distribution. In the 15°N zone there is a concentration of nesting activity by the Northern Carmine bee-eater (Merops nubicus) and we take this as an indicator of ground nature.

  12. Female offspring desertion and male-only care increase with natural and experimental increase in food abundance

    PubMed Central

    Eldegard, Katrine; Sonerud, Geir A.

    2009-01-01

    In species with biparental care, one parent may escape the costs of parental care by deserting and leaving the partner to care for the offspring alone. A number of theoretical papers have suggested a link between uniparental offspring desertion and ecological factors, but empirical evidence is scarce. We investigated the relationship between uniparental desertion and food abundance in a natural population of Tengmalm's owl Aegolius funereus, both by means of a 5-year observational study and a 1-year experimental study. Parents and offspring were fitted with radio-transmitters in order to reveal the parental care strategy (i.e. care or desert) of individual parents, and to keep track of the broods post-fledging. We found that 70 per cent of the females from non-experimental nests deserted, while their partner continued to care for their joint offspring alone. Desertion rate was positively related to natural prey population densities and body reserves of the male partner. In response to food supplementation, a larger proportion of the females deserted, and females deserted the offspring at an earlier age. Offspring survival during the post-fledging period tended to be lower in deserted than in non-deserted broods. We argue that the most important benefit of deserting may be remating (sequential polyandry). PMID:19324835

  13. Female offspring desertion and male-only care increase with natural and experimental increase in food abundance.

    PubMed

    Eldegard, Katrine; Sonerud, Geir A

    2009-05-01

    In species with biparental care, one parent may escape the costs of parental care by deserting and leaving the partner to care for the offspring alone. A number of theoretical papers have suggested a link between uniparental offspring desertion and ecological factors, but empirical evidence is scarce. We investigated the relationship between uniparental desertion and food abundance in a natural population of Tengmalm's owl Aegolius funereus, both by means of a 5-year observational study and a 1-year experimental study. Parents and offspring were fitted with radio-transmitters in order to reveal the parental care strategy (i.e. care or desert) of individual parents, and to keep track of the broods post-fledging. We found that 70 per cent of the females from non-experimental nests deserted, while their partner continued to care for their joint offspring alone. Desertion rate was positively related to natural prey population densities and body reserves of the male partner. In response to food supplementation, a larger proportion of the females deserted, and females deserted the offspring at an earlier age. Offspring survival during the post-fledging period tended to be lower in deserted than in non-deserted broods. We argue that the most important benefit of deserting may be remating (sequential polyandry). PMID:19324835

  14. Abiotic stress protection by ecologically abundant dimethylsulfoniopropionate and its natural and synthetic derivatives: insights from Bacillus subtilis.

    PubMed

    Broy, Sebastian; Chen, Chiliang; Hoffmann, Tamara; Brock, Nelson L; Nau-Wagner, Gabriele; Jebbar, Mohamed; Smits, Sander H J; Dickschat, Jeroen S; Bremer, Erhard

    2015-07-01

    Dimethylsulfoniopropionate (DMSP) is an abundant osmolyte and anti-stress compound produced primarily in marine ecosystems. After its release into the environment, microorganisms can exploit DMSP as a source of sulfur and carbon, or accumulate it as an osmoprotectant. However, import systems for this ecophysiologically important compatible solute, and its stress-protective properties for microorganisms that do not produce it are insufficiently understood. Here we address these questions using a well-characterized set of Bacillus subtilis mutants to chemically profile the influence of DMSP import on stress resistance, the osmostress-adaptive proline pool and on osmotically controlled gene expression. We included in this study the naturally occurring selenium analogue of DMSP, dimethylseleniopropionate (DMSeP), as well as a set of synthetic DMSP derivatives. We found that DMSP is not a nutrient for B.?subtilis, but it serves as an excellent stress protectant against challenges conferred by sustained high salinity or lasting extremes in both low and high growth temperatures. DMSeP and synthetic DMSP derivatives retain part of these stress protective attributes, but DMSP is clearly the more effective stress protectant. We identified the promiscuous and widely distributed ABC transporter OpuC as a high-affinity uptake system not only for DMSP, but also for its natural and synthetic derivatives. PMID:25384455

  15. Paleoenvironmental implications of taxonomic variation among ?15N values of chloropigments

    USGS Publications Warehouse

    Higgins, Meytal B.; Wolfe-Simon, Felisa; Robinson, Rebecca S.; Qin, Yelun; Saito, Mark A.; Pearson, Ann

    2011-01-01

    Natural variations in the ratios of nitrogen isotopes in biomass reflect variations in nutrient sources utilized for growth. In order to use ?15N values of chloropigments of photosynthetic organisms to determine the corresponding ?15N values of biomass – and by extension, surface waters – the isotopic offset between chlorophyll and biomass must be constrained. Here we examine this offset in various geologically-relevant taxa, grown using nutrient sources that may approximate ocean conditions at different times in Earth’s history. Phytoplankton in this study include cyanobacteria (diazotrophic and non-diazotrophic), eukaryotic algae (red and green), and anoxygenic photosynthetic bacteria (Proteobacteria), as well as environmental samples from sulfidic lake water. Cultures were grown using N2, NO3?, and NH4+ as nitrogen sources, and were examined under different light regimes and growth conditions. We find surprisingly high variability in the isotopic difference (?15Nbiomass ? ?15Nchloropigment) for prokaryotes, with average values for species ranging from ?12.2‰ to +11.7‰. We define this difference as ?por, a term that encompasses diagenetic porphyrins and chlorins, as well as chlorophyll. Negative values of ?por reflect chloropigments that are 15N-enriched relative to biomass. Notably, this enrichment appears to occur only in cyanobacteria. The average value of ?por for freshwater cyanobacterial species is ?9.8 ± 1.8‰, while for marine cyanobacteria it is ?0.9 ± 1.3‰. These isotopic effects group environmentally but not phylogenetically, e.g., ?por values for freshwater Chroococcales resemble those of freshwater Nostocales but differ from those of marine Chroococcales. Our measured values of ?por for eukaryotic algae (range = 4.7–8.7‰) are similar to previous reports for pure cultures. For all taxa studied, values of ?por do not depend on the type of nitrogen substrate used for growth. The observed environmental control of ?por suggests that values of ?por could be useful for determining the fractional burial of eukaryotic vs. cyanobacterial organic matter in the sedimentary record.

  16. ?15N constraints on long-term nitrogen balances in temperate forests

    USGS Publications Warehouse

    Perakis, S.S.; Sinkhorn, E.R.; Compton, J.E.

    2011-01-01

    Biogeochemical theory emphasizes nitrogen (N) limitation and the many factors that can restrict N accumulation in temperate forests, yet lacks a working model of conditions that can promote naturally high N accumulation. We used a dynamic simulation model of ecosystem N and ?15N to evaluate which combination of N input and loss pathways could produce a range of high ecosystem N contents characteristic of forests in the Oregon Coast Range. Total ecosystem N at nine study sites ranged from 8,788 to 22,667 kg ha?1 and carbon (C) ranged from 188 to 460 Mg ha?1, with highest values near the coast. Ecosystem ?15N displayed a curvilinear relationship with ecosystem N content, and largely reflected mineral soil, which accounted for 96–98% of total ecosystem N. Model simulations of ecosystem N balances parameterized with field rates of N leaching required long-term average N inputs that exceed atmospheric deposition and asymbiotic and epiphytic N2-fixation, and that were consistent with cycles of post-fire N2-fixation by early-successional red alder. Soil water ?15NO3 ? patterns suggested a shift in relative N losses from denitrification to nitrate leaching as N accumulated, and simulations identified nitrate leaching as the primary N loss pathway that constrains maximum N accumulation. Whereas current theory emphasizes constraints on biological N2-fixation and disturbance-mediated N losses as factors that limit N accumulation in temperate forests, our results suggest that wildfire can foster substantial long-term N accumulation in ecosystems that are colonized by symbiotic N2-fixing vegetation.

  17. 15N CSA tensors and 15N-1H dipolar couplings of protein hydrophobic core residues investigated by static solid-state NMR

    NASA Astrophysics Data System (ADS)

    Vugmeyster, Liliya; Ostrovsky, Dmitry; Fu, Riqiang

    2015-10-01

    In this work, we assess the usefulness of static 15N NMR techniques for the determination of the 15N chemical shift anisotropy (CSA) tensor parameters and 15N-1H dipolar splittings in powder protein samples. By using five single labeled samples of the villin headpiece subdomain protein in a hydrated lyophilized powder state, we determine the backbone 15N CSA tensors at two temperatures, 22 and -35 °C, in order to get a snapshot of the variability across the residues and as a function of temperature. All sites probed belonged to the hydrophobic core and most of them were part of ?-helical regions. The values of the anisotropy (which include the effect of the dynamics) varied between 130 and 156 ppm at 22 °C, while the values of the asymmetry were in the 0.32-0.082 range. The Leu-75 and Leu-61 backbone sites exhibited high mobility based on the values of their temperature-dependent anisotropy parameters. Under the assumption that most differences stem from dynamics, we obtained the values of the motional order parameters for the 15N backbone sites. While a simple one-dimensional line shape experiment was used for the determination of the 15N CSA parameters, a more advanced approach based on the "magic sandwich" SAMMY pulse sequence (Nevzorov and Opella, 2003) was employed for the determination of the 15N-1H dipolar patterns, which yielded estimates of the dipolar couplings. Accordingly, the motional order parameters for the dipolar interaction were obtained. It was found that the order parameters from the CSA and dipolar measurements are highly correlated, validating that the variability between the residues is governed by the differences in dynamics. The values of the parameters obtained in this work can serve as reference values for developing more advanced magic-angle spinning recoupling techniques for multiple labeled samples.

  18. 15N/ 14N and 18O/ 16O stable isotope ratios of nitrous oxide produced during denitrification in temperate forest soils

    NASA Astrophysics Data System (ADS)

    Snider, David M.; Schiff, Sherry L.; Spoelstra, John

    2009-02-01

    Anaerobic incubations of upland and wetland temperate forest soils from the same watershed were conducted under different moisture and temperature conditions. Rates of nitrous oxide (N 2O) production by denitrification of nitrate ( NO3-) and the stable isotopic composition of the N 2O (? 15N, ? 18O) were measured. In all soils, N 2O production increased with elevated temperature and soil moisture. At each temperature and moisture level, the rate of N 2O production in the wetland soil was greater than in the upland soil. The 15N isotope effect (?) (product - substrate) ranged from -20‰ to -29‰. These results are consistent with other published estimates of 15N fractionation from both single species culture experiments and soil incubation studies from different ecosystems. A series of incubations were conducted with 18O-enriched water (H 2O) to determine if significant oxygen exchange (O-exchange) occurred between H 2O and N 2O precursors during denitrification. The exchange of H 2O-O with nitrite ( NO2-) and/or nitric oxide (NO) oxygen has been documented in single organism culture studies but has not been demonstrated in soils prior to this study. The fraction of N 2O-O derived from H 2O-O was confined to a strikingly narrow range that differed between soil types. H 2O-O incorporation into N 2O produced from upland and wetland soils was 86% to 94% and 64% to 70%, respectively. Neither the temperature, soil moisture, nor the rate of N 2O production influenced the magnitude of O-exchange. With the exception of one treatment, the net 18O isotope effect (? net) (product-substrate) ranged from +37‰ to +43‰. Most previous studies that have reported 18O isotope effects for denitrification of NO3- to N 2O have failed to account for the effect of oxygen exchange with H 2O. When high amounts of O-exchange occur after fractionation during reductive O-loss, the 18O-enrichment is effectively lost or diminished and ? 18O-N 2O values will be largely dictated by ? 18O-H 2O values and subsequent fractionation. The process and extent of O-exchange, combined with the magnitude of oxygen isotope fractionation at each reduction step, appear to be the dominant controls on the observed oxygen isotope effect. In these experiments, significant oxygen isotope fractionation was observed to occur after the majority of water O-exchange. Due to the importance of O-exchange, the net oxygen isotope effect for N 2O production in soils can only be determined using ? 18O-H 2O addition experiments with ? 18O-H 2O close to natural abundance. The results of this study support the continued use of ? 15N-N 2O analysis to fingerprint N 2O produced from the denitrification of NO3-. The utilization of 18O/ 16O ratios of N 2O to study N 2O production pathways in soil environments is complicated by oxygen exchange with water, which is not usually quantified in field studies. The oxygen isotope fractionation observed in this study was confined to a narrow range, and there was a clear difference in water O-exchange between soil types regardless of temperature, soil moisture, and N 2O production rate. This suggests that 18O/ 16O ratios of N 2O may be useful in characterizing the actively denitrifying microbial community.

  19. Nitrogen-15-labeled deoxynucleosides. 3. Synthesis of (3- sup 15 N)-2 prime -deoxyadenosine

    SciTech Connect

    Rhee, Young-Sook; Jones, R.A. )

    1990-10-24

    The synthesis of (3-{sup 15}N)-labeled adenine has been reported by several groups. Each of these syntheses followed essentially the same route, in which the {sup 15}N is introduced by nitration of 4-bromoimidazole under forcing conditions using ({sup 15}N)-HNO{sub 3}. The authors have devised an alternate route which uses an azo coupling reaction for introduction of the {sup 15}N and proceeds through the intermediacy of (5-{sup 15}N)-labeled 5-aminoimidazole-4-carboxamide (AICA). An unrelated route to the (5-{sup 15}N)-labeled 5-amino-imidazole ribonucleoside (AIRs) was recently reported. AICA is a versatile precursor, which is most commonly used for entry into the guanine or isoguanine families, although it is usually used as the AICA-riboside rather than the heterocycle itself. The authors have found that AICA also can be used for the adenine family by cyclization to hypoxanthine using diethoxymethyl acetate in DMF at reflux. Although these conditions are more vigorous than those required for cyclization of 4,5-diaminopyrimidines using this reagent, the reaction works well. In addition, they report high-yield enzymatic conversion of (3-{sup 15}N)-adenine to (3-{sup 15}N)-2{prime}-deoxyadenosine.

  20. Accessible NMR Experiments Studying the Hydrodynamics of [subscript 15]N-Enriched Ubiquitin at Low Fields

    ERIC Educational Resources Information Center

    Thompson, Laura E.; Rovnyak, David

    2007-01-01

    We have recently developed and implemented two experiments in biomolecular NMR for an undergraduate-level biophysical chemistry laboratory with commercially available [subscript 15]N-enriched human ubiquitin. These experiments take advantage of [subscript 15]N direct detection of the NMR signal. The first experiment develops skills in acquiring…

  1. Accessible NMR Experiments Studying the Hydrodynamics of [superscript 15]N-Enriched Ubiquitin at Low Fields

    ERIC Educational Resources Information Center

    Thompson, Laura E.; Rovnyak, David

    2007-01-01

    We have recently developed and implemented two experiments in biomolecular NMR for an undergraduate-level biophysical chemistry laboratory with commercially available [superscript 15]N-enriched human ubiquitin. These experiments take advantage of [superscript 15]N direct detection of the NMR signal. The first experiment develops skills in…

  2. Increased Plant Uptake of Nitrogen from 15N Depleted Fertilizer Using Plant Growth-Promoting Rhizobacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The techniques of 15N isotope have been very useful for determining the behavior and fate of N in soil, including the use efficiency of applied N fertilizers by plants. Our objective in this study was to use 15N isotope techniques to demonstrate that a model plant growth-promoting rhizobacteria (PGP...

  3. Disturbance and topography shape nitrogen availability and ?15N over long-term forest succession

    EPA Science Inventory

    Forest disturbance and long-term succession can promote open N cycling that increases N loss and soil ?15N values. We examined soil and foliar patterns in N and ?15N, and soil N mineralization, across a topographically complex montane forest landscape influenced by human logging ...

  4. Measurement of Dipolar Couplings in a Uniformly 13C,15N-Labeled Membrane Protein: Distances

    E-print Network

    Griffin, Robert G.

    Measurement of Dipolar Couplings in a Uniformly 13C,15N-Labeled Membrane Protein: Distances between. The measured distances are in reasonable agreement with ones reported in recent diffraction structures of light are the first example of long-range MAS NMR distance measurements in a U-13C,15N-labeled macromolecule

  5. Variations of 15N in eastern oysters (Crassostrea virginica) as a baseline to

    E-print Network

    Hilderbrand, Robert H.

    Variations of 15N in eastern oysters (Crassostrea virginica) as a baseline to assess waste nitrogen examined via fieldwork and modeling to answer four questions 1) 15N in oysters as indicator of nitrogen sources 2) What sample size optimizes effort and error? 3) Can oysters from multiple collection sites

  6. 15N and13C NMR investigation of hydroxylamine-derivatized humic substances

    USGS Publications Warehouse

    Thorn, K.A.; Arterburn, J.B.; Mikita, M.A.

    1992-01-01

    Five fulvic and humic acid samples of diverse origins were derivatized with 15N-labeled hydroxylamine and analyzed by liquid-phase 15N NMR spectrometry. The 15N NMR spectra indicated that hydroxylamine reacted similarly with all samples and could discriminate among carbonyl functional groups. Oximes were the major derivatives; resonances attributable to hydroxamic acids, the reaction products of hydroxylamine with esters, and resonances attributable to the tautomeric equilibrium position between the nitrosophenol and monoxime derivatives of quinones, the first direct spectroscopic evidence for quinones, also were evident. The 15N NMR spectra also suggested the presence of nitriles, oxazoles, oxazolines, isocyanides, amides, and lactams, which may all be explained in terms of Beckmann reactions of the initial oxime derivatives. INEPT and ACOUSTIC 15N NMR spectra provided complementary information on the derivatized samples. 13C NMR spectra of derivatized samples indicated that the ketone/quinone functionality is incompletely derivatized with hydroxylamine. ?? 1991 American Chemical Society.

  7. Resonance strengths in the 14N(p, ?)15O and 15N(p, ? ?)12C reactions

    E-print Network

    Michele Marta; Erik Trompler; Daniel Bemmerer; Roland Beyer; Carlo Broggini; Antonio Caciolli; Martin Erhard; Zsolt Fülöp; Eckart Grosse; György Gyürky; Roland Hannaske; Arnd R. Junghans; Roberto Menegazzo; Chithra Nair; Ronald Schwengner; Tamás Szücs; Simone Vezzú; Andreas Wagner; Dmitry Yakorev

    2010-06-01

    The 14N(p, \\gamma)15O reaction is the slowest reaction of the carbon-nitrogen-oxygen cycle of hydrogen burning in stars. As a consequence, it determines the rate of the cycle. The 15N(p, \\alpha \\gamma)12C reaction is frequently used in inverse kinematics for hydrogen depth profiling in materials. The 14N(p, \\gamma)15O and 15N(p, \\alpha \\gamma)12C reactions have been studied simultaneously, using titanium nitride targets of natural isotopic composition and a proton beam. The strengths of the resonances at Ep = 1058 keV in 14N(p, \\gamma)15O and at Ep = 897 and 430 keV in 15N(p, \\alpha \\gamma)12C have been determined with improved precision, relative to the well-known resonance at Ep = 278 keV in 14N(p, \\gamma)15O. The new recommended values are \\omega \\gamma = 0.353$\\pm$0.018, 362$\\pm$20, and 21.9$\\pm$1.0 eV for their respective strengths. In addition, the branching ratios for the decay of the Ep = 1058 keV resonance in 14N(p, \\gamma)15O have been redetermined. The data reported here should facilitate future studies of off-resonant capture in the 14N(p, \\gamma)15O reaction that are needed for an improved R-matrix extrapolation of the cross section. In addition, the data on the 430 keV resonance in 15N(p, \\alpha \\gamma)12C may be useful for hydrogen depth profiling.

  8. Disturbance and topography shape nitrogen availability and ?15 N over long-term forest succession

    USGS Publications Warehouse

    Perakis, Steven; Tepley, Alan J.; Compton, Jana

    2015-01-01

    Forest disturbance and long-term succession towards old-growth are thought to increase nitrogen (N) availability and N loss, which should increase soil ?15N values. We examined soil and foliar patterns in N and ?15N, and soil N mineralization, across 800 years of forest succession in a topographically complex montane landscape influenced by human logging and wildfire. In contrast to expectations, we found that disturbance caused declines in surface mineral soil ?15N values, both in logged forests measured 40–50 years after disturbance, and in unlogged forests disturbed by severe wildfire within the last 200 years. Both symbiotic N fixation and N transfers from disturbed vegetation and detritus could lower soil ?15N values after disturbance. A more important role for symbiotic N fixation is suggested by lower soil ?15N values in slow-successional sites with slow canopy closure, which favors early-successional N fixers. Soil ?15N values increased only marginally throughout 800 years of succession, reflecting soil N uptake by vegetation and strong overall N retention. Although post-disturbance N inputs lowered surface soil ?15N values, steady-state mass balance calculations suggest that wildfire combustion of vegetation and detritus can dominate long-term N loss and increase whole-ecosystem ?15N. On steeper topography, declining soil ?15N values highlight erosion and accelerated soil turnover as an additional abiotic control on N balances. We conclude for N-limited montane forests that soil ?15N and N availability are less influenced by nitrate leaching and denitrification loss than by interactions between disturbance, N fixation, and erosion.

  9. Studies of minute quantities of natural abundance molecules using 2D heteronuclear correlation spectroscopy under 100kHz MAS

    DOE PAGESBeta

    Nishiyama, Y.; Kobayashi, T.; Malon, M.; Singappuli-Arachchige, D.; Slowing, I. I.; Pruski, M.

    2015-02-16

    Two-dimensional 1H{13C} heteronuclear correlation solid-state NMR spectra of naturally abundant solid materials are presented, acquired using the 0.75-mm magic angle spinning (MAS) probe at spinning rates up to 100 kHz. In spite of the miniscule sample volume (290 nL), high-quality HSQC-type spectra of bulk samples as well as surface-bound molecules can be obtained within hours of experimental time. The experiments are compared with those carried out at 40 kHz MAS using a 1.6-mm probe, which offered higher overall sensitivity due to a larger rotor volume. The benefits of ultrafast MAS in such experiments include superior resolution in 1H dimension withoutmore »resorting to 1H–1H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. As a result, the HMQC spectra of surface-bound species can be also acquired under 100 kHz MAS, although the dephasing of transverse magnetization has significant effect on the efficiency transfer under MAS alone.« less

  10. Using natural abundance radiocarbon to trace the flux of petrocarbon to the seafloor following the Deepwater Horizon oil spill.

    PubMed

    Chanton, Jeffrey; Zhao, Tingting; Rosenheim, Brad E; Joye, Samantha; Bosman, Samantha; Brunner, Charlotte; Yeager, Kevin M; Diercks, Arne R; Hollander, David

    2015-01-20

    In 2010, the Deepwater Horizon accident released 4.6–6.0 × 10(11) grams or 4.1 to 4.6 million barrels of fossil petroleum derived carbon (petrocarbon) as oil into the Gulf of Mexico. Natural abundance radiocarbon measurements on surface sediment organic matter in a 2.4 × 10(10) m(2) deep-water region surrounding the spill site indicate the deposition of a fossil-carbon containing layer that included 1.6 to 2.6 × 10(10) grams of oil-derived carbon. This quantity represents between 0.5 to 9.1% of the released petrocarbon, with a best estimate of 3.0–4.9%. These values may be lower limit estimates of the fraction of the oil that was deposited on the seafloor because they focus on a limited mostly deep-water area of the Gulf, include a conservative estimate of thickness of the depositional layer, and use an average background or prespill radiocarbon value for sedimentary organic carbon that produces a conservative value. A similar approach using hopane tracer estimated that 4–31% of 2 million barrels of oil that stayed in the deep sea settled on the bottom. Converting that to a percentage of the total oil that entered into the environment (to which we normalized our estimate) converts this range to 1.8 to 14.4%. Although extrapolated over a larger area, our independent estimate produced similar values. PMID:25494527

  11. Natural Abundance 43Ca NMR as a Tool for Exploring Calcium Biomineralization: Renal Stone Formation and Growth

    SciTech Connect

    Bowers, Geoffrey M.; Kirkpatrick, Robert J.

    2011-12-07

    Renal stone diseases are a global health issue with little effective therapeutic recourse aside from surgery and shock-wave lithotripsy, primarily because the fundamental chemical mechanisms behind calcium biomineralization are poorly understood. In this work, we show that natural abundance 43Ca NMR at 21.1 T is an effective means to probe the molecular-level Ca2+ structure in oxalate-based kidney stones. We find that the 43Ca NMR resonance of an authentic oxalate-based kidney stone cannot be explained by a single pure phase of any common Ca2+-bearing stone mineral. Combined with XRD results, our findings suggest an altered calcium oxalate monohydrate-like Ca2+ coordination environment for some fraction of Ca2+ in our sample. The evidence is consistent with existing literature hypothesizing that nonoxalate organic material interacts directly with Ca2+ at stone surfaces and is the primary driver of renal stone aggregation and growth. Our findings show that 43Ca NMR spectroscopy may provide unique and crucial insight into the fundamental chemistry of kidney stone formation, growth, and the role organic molecules play in these processes.

  12. In VivoQuantitation of Cerebral Metabolite Concentrations Using Natural Abundance 13C MRS at 1.5 T

    NASA Astrophysics Data System (ADS)

    Blüml, Stefan

    1999-02-01

    A method for the quantitation of cerebral metabolites on a clinical MR scanner by natural abundance13C MRSin vivois described. Proton-decoupled spectra were acquired with a power deposition within FDA guidelines using a novel coil design.myo-Inositol, quantified by a separate proton MRS, and readily detectable in13C MRS, was used as an internal reference. Normal concentrations, measured in four control subjects, age 7 months to 12 years, were glutamate 9.9 ± 0.7, glutamine 5.6 ± 1.0, and NAA 8.8 ± 2.8 mmol/kg. In a patient diagnosed with Canavan disease, examined four times, glutamate was reduced to 46% of normal, 4.6 ± 0.5 mmol/kg. NAA was increased by 50% to 13.2 ± 1.6 mmol/kg in13C MRS, consistent with the 41% increase to 12.3 ± 1.1 from control 8.7 ± 1.1 mmol/kg assayed by1H MRS. Limited concentration of glutamate may impact on glutamatergic neurons and excitatory neurotransmission in Canavan disease. Quantitation of cerebral glutamate in human brain may have clinical value in human neuropathologies in which glutamate is believed to play a central role.

  13. Abundance of non-native crabs in intertidal habitats of New England with natural and artificial structure

    PubMed Central

    Lovely, Christina M.; Judge, Michael L.

    2015-01-01

    Marine habitats containing complex physical structure (e.g., crevices) can provide shelter from predation for benthic invertebrates. To examine effects of natural and artificial structure on the abundance of intertidal juvenile crabs, 2 experiments were conducted in Kingston Bay, Massachusetts, USA, from July to September, 2012. In the first experiment, structure was manipulated in a two-factor design that was placed in the high intertidal for 3 one-week periods to test for both substrate type (sand vs. rock) and the presence or absence of artificial structure (mesh grow-out bags used in aquaculture, ?0.5 m2 with 62 mm2 mesh openings). The Asian shore crab, Hemigrapsus sanguineus, and small individuals of the green crab, Carcinus maenas, were observed only in the treatments of rocks and mesh bag plus rocks. Most green crabs were small (<6 mm in carapace width) whereas H. sanguineus occurred in a wide range of sizes. In the second experiment, 3 levels of oyster-shell treatments were established using grow-out bags placed on a muddy sand substrate in the low intertidal zone: mesh grow-out bags without shells, grow-out bags with oyster shells, and grow-out bags containing live oysters. Replicate bags were deployed weekly for 7 weeks in a randomized complete block design. All crabs collected in the bags were juvenile C. maenas (1–15 mm carapace width), and numbers of crabs differed 6-fold among treatments, with most crabs present in bags with live oysters (29.5 ± 10.6 m?2 [mean ± S.D.]) and fewest in bags without shells (4.9 ± 3.7 m?2). Both C. maenas and H. sanguineus occurred in habitats with natural structure (cobble rocks). The attraction of juvenile C. maenas to artificial structure consisting of plastic mesh bags containing both oyster shells and living oysters could potentially impact oyster aquaculture operations. PMID:26401456

  14. Abundance of non-native crabs in intertidal habitats of New England with natural and artificial structure.

    PubMed

    Lovely, Christina M; O'Connor, Nancy J; Judge, Michael L

    2015-01-01

    Marine habitats containing complex physical structure (e.g., crevices) can provide shelter from predation for benthic invertebrates. To examine effects of natural and artificial structure on the abundance of intertidal juvenile crabs, 2 experiments were conducted in Kingston Bay, Massachusetts, USA, from July to September, 2012. In the first experiment, structure was manipulated in a two-factor design that was placed in the high intertidal for 3 one-week periods to test for both substrate type (sand vs. rock) and the presence or absence of artificial structure (mesh grow-out bags used in aquaculture, ?0.5 m(2) with 62 mm(2) mesh openings). The Asian shore crab, Hemigrapsus sanguineus, and small individuals of the green crab, Carcinus maenas, were observed only in the treatments of rocks and mesh bag plus rocks. Most green crabs were small (<6 mm in carapace width) whereas H. sanguineus occurred in a wide range of sizes. In the second experiment, 3 levels of oyster-shell treatments were established using grow-out bags placed on a muddy sand substrate in the low intertidal zone: mesh grow-out bags without shells, grow-out bags with oyster shells, and grow-out bags containing live oysters. Replicate bags were deployed weekly for 7 weeks in a randomized complete block design. All crabs collected in the bags were juvenile C. maenas (1-15 mm carapace width), and numbers of crabs differed 6-fold among treatments, with most crabs present in bags with live oysters (29.5 ± 10.6 m(-2) [mean ± S.D.]) and fewest in bags without shells (4.9 ± 3.7 m(-2)). Both C. maenas and H. sanguineus occurred in habitats with natural structure (cobble rocks). The attraction of juvenile C. maenas to artificial structure consisting of plastic mesh bags containing both oyster shells and living oysters could potentially impact oyster aquaculture operations. PMID:26401456

  15. Importance of bacterivory and preferential selection toward diatoms in larvae of Crepidula fornicata (L.) assessed by a dual stable isotope (13C, 15N) labeling approach

    NASA Astrophysics Data System (ADS)

    Leroy, Fanny; Riera, Pascal; Jeanthon, Christian; Edmond, Frédérique; Leroux, Cédric; Comtet, Thierry

    2012-05-01

    In Europe, the gastropod Crepidula fornicata is an invasive species characterized by a long reproductive period (from February to November). Thus, its larvae are exposed to variations in available food sources (in terms of quantity and quality). We aimed to investigate if bacteria could contribute to larval food both in presence or absence of phytoplankton, and to compare these results to seasonal variations of bacteria and phytoplankton abundances at a coastal site in the English Channel. First, ingestion of fluorescent beads of 0.5 to 2 ?m diameter, showed that larvae were able to ingest particles of typical bacterial size. Then we used a dual stable isotope labeling approach which consisted in labeling a bacterial pelagic community with 15N and a diatom (Chaetoceros gracilis) culture with 13C, and supplying larvae with 15N-labeled bacteria, 13C-labeled diatoms, and both labeled sources. This technique has, to our knowledge, never been applied to invertebrate larvae. After 24 h of experiment, larvae were significantly enriched in all treatments: + 21.5‰ (??13C) when supplied with diatoms, + 1364‰ (??15N) when supplied with bacteria, and + 24‰ (??13C) and + 135‰ (??15N) when supplied with the two mixed sources. These results indicated that bacteria can contribute to the larval nutrition in C. fornicata, even in the presence of phytoplankton. Our results however suggested that larvae of C. fornicata preferentially used diatoms and showed that the supply of free bacteria did not alter the uptake of diatoms. Considering the seasonal variations of bacteria and phytoplankton abundances at the study site, these results suggested that bacteria may constitute a complementary resource for the larvae of C. fornicata when phytoplankton is abundant and may become a substitute resource when phytoplankton is less available. This approach offers promising perspectives to trace food sources and assess nitrogen and carbon fluxes between planktotrophic larvae and their preys.

  16. Geometry of 2,5-dihydrofuran from the free jet rotational spectra of the 13C and 18O isotopic species in natural abundance

    NASA Astrophysics Data System (ADS)

    Melandri, S.; Velino, B.; Caminati, W.

    2001-05-01

    The rotational spectra of all singly substituted 13C and 18O isotopic species of the ground vibrational state of 2,5-dihydrofuran have been measured in natural abundance with millimeter-wave free jet technique and the rs and r0 heavy atom geometries have been determined.

  17. Compound-specific 15N analysis of amino acids in 15N tracer experiments provide an estimate of newly synthesised soil protein from inorganic and organic substrates

    NASA Astrophysics Data System (ADS)

    Charteris, Alice; Michaelides, Katerina; Evershed, Richard

    2015-04-01

    Organic N concentrations far exceed those of inorganic N in most soils and despite much investigation, the composition and cycling of this complex pool of SOM remains poorly understood. A particular problem has been separating more recalcitrant soil organic N from that actively cycling through the soil system; an important consideration in N cycling studies and for the soil's nutrient supplying capacity. The use of 15N-labelled substrates as stable isotope tracers has contributed much to our understanding of the soil system, but the complexity and heterogeneity of soil organic N prevents thorough compound-specific 15N analyses of organic N compounds and makes it difficult to examine any 15N-labelled organic products in any detail. As a result, a significant proportion of previous work has either simply assumed that since the majority of soil N is organic, all of the 15N retained in the soil is organic N (e.g. Sebilo et al., 2013) or subtracted 15N-labelled inorganic compounds from bulk values (e.g. Pilbeam et al., 1997). While the latter approach is more accurate, these methods only provide an estimate of the bulk 15N value of an extremely complex and non-uniformly labelled organic pool. A more detailed approach has been to use microbial biomass extraction (Brookes et al., 1985) and subsequent N isotopic analysis to determine the 15N value of biomass-N, representing the fraction of 15N assimilated by microbes or the 15N cycling through the 'living' or 'active' portion of soil organic N. However, this extraction method can only generate estimates and some lack of confidence in its validity and reliability remains. Here, we present an alternative technique to obtain a measure of the assimilation of an applied 15N substrate by the soil microbial biomass and an estimate of the newly synthesized soil protein, which is representative of the magnitude of the active soil microbial biomass. The technique uses a stable isotope tracer and compound-specific 15N analysis, but unlike previous works analyses for amino acids (representing organic products) rather than ammonium (NH4+) and nitrate (NO3-). Amino acids are commonly referred to as 'the building blocks of life' as they form the proteins which regulate life's essential biochemical reactions. Proteinaceous matter generally comprises 20-40% of total soil N and is ubiquitous in living organisms, so is a likely 'organic product' of microbial activity/assimilation. Hence, we consider it likely that amino acids represent the major organic nitrogenous products and a reasonable 'proxy' for/measure of the assimilation of an applied 15N substrate by the soil microbial biomass and an estimate of the newly synthesized soil protein. Brookes, P. C. et al. Soil Biol Biochem. 1985, 17, 837-842. Jenkinson, D. S. et al. Soil Biol Biochem. 2004, 36, 5-7. Nannipieri, P. et al. Plant Soil. 1999, 208, 43-56. Pilbeam, C. J. et al. J Agr Sci. 1997, 128, 415-424. Sebilo, M. et al. PNAS. 2013, 110, 18185-18189.

  18. Nitrogen stable isotope composition (?15N) of vehicle-emitted NOx.

    PubMed

    Walters, Wendell W; Goodwin, Stanford R; Michalski, Greg

    2015-02-17

    The nitrogen stable isotope ratio of NOx (?(15)N-NOx) has been proposed as a regional indicator for NOx source partitioning; however, knowledge of ?(15)N values from various NOx emission sources is limited. This study presents a detailed analysis of ?(15)N-NOx emitted from vehicle exhaust, the largest source of anthropogenic NOx. To accomplish this, NOx was collected from 26 different vehicles, including gasoline and diesel-powered engines, using a modification of a NOx collection method used by the United States Environmental Protection Agency, and ?(15)N-NOx was analyzed. The vehicles sampled in this study emitted ?(15)N-NOx values ranging from -19.1 to 9.8‰ that negatively correlated with the emitted NOx concentrations (8.5 to 286 ppm) and vehicle run time because of kinetic isotope fractionation effects associated with the catalytic reduction of NOx. A model for determining the mass-weighted ?(15)N-NOx from vehicle exhaust was constructed on the basis of average commute times, and the model estimates an average value of -2.5 ± 1.5‰, with slight regional variations. As technology improvements in catalytic converters reduce cold-start emissions in the future, it is likely to increase current ?(15)N-NOx values emitted from vehicles. PMID:25621737

  19. Steroselective synthesis and application of L-( sup 15 N) amino acids

    SciTech Connect

    Unkefer, C.J. ); Lodwig, S.N. . Div. of Science)

    1991-01-01

    We have developed two general approaches to the stereoselective synthesis of {sup 15}N- and {sup 13}C-labeled amino acids. First, labeled serine, biosynthesized using the methylotrophic bacterium M. extorquens AM1, serves as a chiral precursor for the synthesis of other amino acids. For example, pyridoxal phosphate enzymes can be used for the conversion of L-({alpha}-{sup 15}N)serine to L-({alpha}-{sup 15}N)tyrosine, L-({alpha}-{sup 15}N)tryptophan, and L-({alpha}-{sup 15}N)cysteine. In the second approach, developed by Oppolzer and Tamura, an electrophilic amination'' reagent, 1-chloro-1-nitrosocyclohexane, was used to convert chiral enolates into L-{alpha}-amino acids. We prepared 1-chloro-1-({sup 15}N) nitrosocyclohexane and used it to aminate chiral enolates to produce L-({alpha}-{sup 15}N)amino acids. The stereoselectivity of this scheme using the Oppolzer sultam chiral auxiliary is remarkable, producing enantiomer ratios of 200 to 1. 22 refs., 4 figs.

  20. Mammalian DNA ?15N exhibits 40‰ intramolecular variation and is unresponsive to dietary protein level

    PubMed Central

    Strable, Maggie S.; Tschanz, Carolyn L.; Varamini, Behzad; Chikaraishi, Yoshito; Ohkouchi, Naohiko; Brenna, J. Thomas

    2014-01-01

    We report the first high precision characterization of molecular and intramolecular ?15N of nucleosides derived from mammalian DNA. The influence of dietary protein level on brain amino acids and deoxyribonucleosides was determined to investigate whether high protein turnover would alter amino acid 15N or 13C. Pregnant guinea pig dams were fed control diets, or high or low levels of dietary protein throughout gestation, and all pups were fed control diets. Cerebellar DNA of offspring was extracted at 2 and 120 days of life, nucleosides isolated and ?15N and ?13C characterized. Mean diet ?15N = 0.45±0.33‰, compared to cerebellar whole tissue and DNA ?15N = +4.1±0.7‰ and ?4.5±0.4‰, respectively. Cerebellar deoxythymidine (dT), deoxycytidine (dC), deoxyadenosine (dA), and deoxyguanosine (dG) ?15N were +1.4±0.4, ?2.1±0.9, ?7.2±0.3, and ?10.4±0.5‰, respectively. There were no changes in amino acid or deoxyribonucleoside ?15N due to dietary protein level. Using known metabolic relationships, we developed equations to calculate the intramolecular ?15N originating from aspartate (asp) in purines (pur) or pyrimidines (pyr), glutamine (glu), and glycine (gly) to be ?15NASP-PUR, ?15NASP-PYR, ?15NGLN, and ?15NGLY +11.9±2.3‰, +7.0±2.0‰, ?9.1±2.4‰, and ?31.8±8.9‰, respectively. A subset of twelve amino acids from food and brain had mean ?15N of 4.3±3.2‰ and 13.8±3.1‰, respectively, and ?15N for gly and asp were 12.6±2.2‰ and 15.2±0.8‰, respectively. A separate isotope tracer study detected no significant turnover of cerebellar DNA in the first six months of life. The large negative ?15N difference between gly and cerebellar purine N at the gly (7) position implies either that there is a major isotope effect during DNA synthesis, or that in utero gly has a different isotope ratio during rapid growth and metabolism than in adult life. Our data show that cerebellar nucleoside intramolecular ?15N vary over more than 40‰ and are not influenced by dietary protein level or age. PMID:22095504

  1. Variable ?15N Diet-Tissue Discrimination Factors among Sharks: Implications for Trophic Position, Diet and Food Web Models

    PubMed Central

    Olin, Jill A.; Hussey, Nigel E.; Grgicak-Mannion, Alice; Fritts, Mark W.; Wintner, Sabine P.; Fisk, Aaron T.

    2013-01-01

    The application of stable isotopes to characterize the complexities of a species foraging behavior and trophic relationships is dependent on assumptions of ?15N diet-tissue discrimination factors (?15N). As ?15N values have been experimentally shown to vary amongst consumers, tissues and diet composition, resolving appropriate species-specific ?15N values can be complex. Given the logistical and ethical challenges of controlled feeding experiments for determining ?15N values for large and/or endangered species, our objective was to conduct an assessment of a range of reported ?15N values that can hypothetically serve as surrogates for describing the predator-prey relationships of four shark species that feed on prey from different trophic levels (i.e., different mean ?15N dietary values). Overall, the most suitable species-specific ?15N values decreased with increasing dietary-?15N values based on stable isotope Bayesian ellipse overlap estimates of shark and the principal prey functional groups contributing to the diet determined from stomach content analyses. Thus, a single ?15N value was not supported for this speciose group of marine predatory fishes. For example, the ?15N value of 3.7‰ provided the highest percent overlap between prey and predator isotope ellipses for the bonnethead shark (mean diet ?15N = 9‰) whereas a ?15N value < 2.3‰ provided the highest percent overlap between prey and predator isotope ellipses for the white shark (mean diet ?15N = 15‰). These data corroborate the previously reported inverse ?15N-dietary ?15N relationship when both isotope ellipses of principal prey functional groups and the broader identified diet of each species were considered supporting the adoption of different ?15N values that reflect the predators’ ?15N-dietary value. These findings are critical for refining the application of stable isotope modeling approaches as inferences regarding a species’ ecological role in their community will be influenced with consequences for conservation and management actions. PMID:24147026

  2. Variable ?(15)N diet-tissue discrimination factors among sharks: implications for trophic position, diet and food web models.

    PubMed

    Olin, Jill A; Hussey, Nigel E; Grgicak-Mannion, Alice; Fritts, Mark W; Wintner, Sabine P; Fisk, Aaron T

    2013-01-01

    The application of stable isotopes to characterize the complexities of a species foraging behavior and trophic relationships is dependent on assumptions of ?(15)N diet-tissue discrimination factors (?(15)N). As ?(15)N values have been experimentally shown to vary amongst consumers, tissues and diet composition, resolving appropriate species-specific ?(15)N values can be complex. Given the logistical and ethical challenges of controlled feeding experiments for determining ?(15)N values for large and/or endangered species, our objective was to conduct an assessment of a range of reported ?(15)N values that can hypothetically serve as surrogates for describing the predator-prey relationships of four shark species that feed on prey from different trophic levels (i.e., different mean ?(15)N dietary values). Overall, the most suitable species-specific ?(15)N values decreased with increasing dietary-?(15)N values based on stable isotope Bayesian ellipse overlap estimates of shark and the principal prey functional groups contributing to the diet determined from stomach content analyses. Thus, a single ?(15)N value was not supported for this speciose group of marine predatory fishes. For example, the ?(15)N value of 3.7‰ provided the highest percent overlap between prey and predator isotope ellipses for the bonnethead shark (mean diet ?(15)N = 9‰) whereas a ?(15)N value < 2.3‰ provided the highest percent overlap between prey and predator isotope ellipses for the white shark (mean diet ?(15)N = 15‰). These data corroborate the previously reported inverse ?(15)N-dietary ?(15)N relationship when both isotope ellipses of principal prey functional groups and the broader identified diet of each species were considered supporting the adoption of different ?(15)N values that reflect the predators' ?(15)N-dietary value. These findings are critical for refining the application of stable isotope modeling approaches as inferences regarding a species' ecological role in their community will be influenced with consequences for conservation and management actions. PMID:24147026

  3. Cumulative fission yields of short-lived isotopes under natural-abundance-boron-carbide-moderated neutron spectrum

    SciTech Connect

    Finn, Erin C.; Metz, Lori A.; Greenwood, Lawrence R.; Pierson, Bruce; Wittman, Richard S.; Friese, Judah I.; Kephart, Rosara F.

    2015-04-09

    The availability of gamma spectroscopy data on samples containing mixed fission products at short times after irradiation is limited. Due to this limitation, data interpretation methods for gamma spectra of mixed fission product samples, where the individual fission products have not been chemically isolated from interferences, are not well-developed. The limitation is particularly pronounced for fast pooled neutron spectra because of the lack of available fast reactors in the United States. Samples containing the actinide isotopes 233, 235, 238U, 237Np, and 239Pu individually were subjected to a 2$ pulse in the Washington State University 1 MW TRIGA reactor. To achieve a fission-energy neutron spectrum, the spectrum was tailored using a natural abundance boron carbide capsule to absorb neutrons in the thermal and epithermal region of the spectrum. Our tailored neutron spectrum is unique to the WSU reactor facility, consisting of a soft fission spectrum that contains some measurable flux in the resonance region. This results in a neutron spectrum at greater than 0.1 keV with an average energy of 70 keV, similar to fast reactor spectra and approaching that of 235U fission. Unique fission product gamma spectra were collected from 4 minutes to 1 week after fission using single-crystal high purity germanium detectors. Cumulative fission product yields measured in the current work generally agree with published fast pooled fission product yield values from ENDF/B-VII, though a bias was noted for 239Pu. The present work contributes to the compilation of energy-resolved fission product yield nuclear data for nuclear forensic purposes.

  4. Acceleration of Natural-Abundance Solid-State MAS NMR Measurements on Bone by Paramagnetic Relaxation from Gadolinium-DTPA

    PubMed Central

    Mroue, Kamal H.; Zhang, Rongchun; Zhu, Peizhi; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

    2014-01-01

    Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA = Diethylenetriamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the 1H T1 values were calculated from data collected by 1H spin-inversion recovery method detected in natural-abundance 13C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the 1H T1 values can be successfully reduced by a factor of 3.5 using as low as 10 mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the 13C CPMAS spectra. These results obtained from 13C-detected CPMAS experiments were further confirmed using 1H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans. PMID:24881032

  5. Continuous field measurement of N2O isotopologues using FTIR spectroscopy following 15N addition

    NASA Astrophysics Data System (ADS)

    Phillips, R. L.; Griffith, D. W.; Dijkstra, F. A.; Lugg, G.; Lawrie, R.; Macdonald, B.

    2012-12-01

    Anthropogenic additions of fertilizer nitrogen (N) have significantly increased the mole fraction of nitrous oxide (N2O) in the troposphere. Tracking the fate of fertilizer N and its transformation to N2O is important to advance knowledge of greenhouse gas emissions from soils. Transport and transformations are frequently studied using 15N labeling experiments, but instruments capable of continuous measurements of 15N-N2O at the surface of soil have only recently come to the fore. Our primary aim was to quantify emissions of N2O and the fraction of 15N emitted as N2O from an agricultural soil following 15N addition using a mobile Fourier Transform Infrared (FTIR) spectrometer. We set up a short-term field experiment on a coastal floodplain site near Nowra, New South Wales. We deployed an automated chamber system connected to a multi-pass cell (optical pathlength 24 m) and low resolution FTIR spectrometer to measure fluxes of all N2O isotopologues collected from five 0.25 m2 chambers every three hours. We measured N2O fluxes pre and post-application of 15N-labeled substrate as potassium nitrate (KNO3) or urea [CO(NH2)2] to the soil surface. Root mean square uncertainties for all isotopologue measurements were less than 0.3 nmol mol-1 for 1 minute average concentration measurements, and minimum detectable fluxes for each isotopologue were <0.1 ng N m-2 s-1. Emissions of all N2O isotopologues were evident immediately following 15N addition. Emissions of 14N15NO, 15N14NO and 15N15NO isotopologues subsided within 10 d, but 14N14NO fluxes were evident over the entire experiment. The figure provides an overview of the emissions. Cumulative 15N-N2O fluxes (sum of the three 15N isotopologues) per chamber for the 14 days following 15N addition ranged from 1.5 to 10.3 mg 15N-N2O m-2. The chambers were destructively sampled after 2 weeks and 15N analyzed in soil and plant material using isotope ratio mass spectrometry. Approximately 1% (range 0.7 - 1.9%) of the total amount of 15N applied was emitted as N2O. Average fractions of 15N recovered in soil, root, shoot, and microbial biomass pools varied between trials but were approximately 0.4, 0.08, 0.1 and 0.03, respectively. The results indicate that the portable FTIR spectroscopic technique can effectively trace transfer of 15N to the atmosphere as N2O after 15N addition, allowing for powerful quantification of N2O emissions under field conditions.

  6. Preparation of 13C/15N-labeled oligomers using the polymerase chain reaction

    DOEpatents

    Chen, Xian (Los Alamos, NM); Gupta, Goutam (Santa Fe, NM); Bradbury, E. Morton (Santa Fe, NM)

    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.

  7. Eastern oyster (Crassostrea virginica) ?15N as a bioindicator of nitrogen sources: Observations and modeling

    PubMed Central

    Fertig, B.; Carruthers, T.J.B.; Dennison, W.C.; Fertig, E.J.; Altabet, M.A.

    2013-01-01

    Stable nitrogen isotopes (?15N) in bioindicators are increasingly employed to identify nitrogen sources in many ecosystems and biological characteristics of the eastern oyster (Crassostrea virginica) make it an appropriate species for this purpose. To assess nitrogen isotopic fractionation associated with assimilation and baseline variations in oyster mantle, gill, and muscle tissue ?15N, manipulative fieldwork in Chesapeake Bay and corresponding modeling exercises were conducted. This study (1) determined that five individuals represented an optimal sample size; (2) verified that ?15N in oysters from two locations converged after shared deployment to a new location reflecting a change in nitrogen sources; (3) identified required exposure time and temporal integration (four months for muscle, two to three months for gill and mantle); and (4) demonstrated seasonal ?15N increases in seston (summer) and oysters (winter). As bioindicators, oysters can be deployed for spatial interpolation of nitrogen sources, even in areas lacking extant populations. PMID:20381097

  8. Carbon-rich Presolar Grains from Massive Stars: Subsolar 12C/13C and 14N/15N Ratios and the Mystery of 15N

    NASA Astrophysics Data System (ADS)

    Pignatari, M.; Zinner, E.; Hoppe, P.; Jordan, C. J.; Gibson, B. K.; Trappitsch, R.; Herwig, F.; Fryer, C.; Hirschi, R.; Timmes, F. X.

    2015-08-01

    Carbon-rich grains with isotopic anomalies compared to the Sun are found in primitive meteorites. They were made by stars, and carry the original stellar nucleosynthesis signature. Silicon carbide grains of Type X and C and low-density (LD) graphites condensed in the ejecta of core-collapse supernovae. We present a new set of models for the explosive He shell and compare them with the grains showing 12C/13C and 14N/15N ratios lower than solar. In the stellar progenitor H was ingested into the He shell and not fully destroyed before the explosion. Different explosion energies and H concentrations are considered. If the supernova shock hits the He-shell region with some H still present, the models can reproduce the C and N isotopic signatures in C-rich grains. Hot-CNO cycle isotopic signatures are obtained, including a large production of 13C and 15N. The short-lived radionuclides 22Na and 26Al are increased by orders of magnitude. The production of radiogenic 22Ne from the decay of 22Na in the He shell might solve the puzzle of the Ne-E(L) component in LD graphite grains. This scenario is attractive for the SiC grains of type AB with 14N/15N ratios lower than solar, and provides an alternative solution for SiC grains originally classified as nova grains. Finally, this process may contribute to the production of 14N and 15N in the Galaxy, helping to produce the 14N/15N ratio in the solar system.

  9. Chlorophyll a-specific ?14C, ?13C and ?15N values in stream periphyton: implications for aquatic food web studies

    NASA Astrophysics Data System (ADS)

    Ishikawa, N. F.; Yamane, M.; Suga, H.; Ogawa, N. O.; Yokoyama, Y.; Ohkouchi, N.

    2015-11-01

    Periphytic algae attached to a streambed substrate (periphyton) are an important primary producer in stream ecosystems. We determined the isotopic composition of chlorophyll a in periphyton collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Stable isotope ratios of carbon (?13C) and nitrogen (?15N) and natural radiocarbon abundances (?14C) were measured in chlorophyll a (?13Cchl, ?15Nchl and ?14Cchl) and bulk (?13Cbulk, ?15Nbulk and ?14Cbulk) for periphyton, a pure aquatic primary producer (Cladophora sp.) and a terrestrial primary producer (Quercus glauca). Periphyton ?13Cbulk and ?13Cchl values did not necessarily correspond to ?13Cbulk for an algal-grazing specialist (Epeorus latifolium). Periphyton ?14Cchl values (-258 ‰ in April and -190 ‰ in October) were slightly lower than ?14Cbulk values (-228 ‰ in April and -179 ‰ in October) but were close to the ?14C value for dissolved inorganic carbon (DIC; -217 ± 31 ‰), which is a mixture of weathered carbonates (?14C = -1000 ‰), CO2 derived from aquatic and terrestrial organic matters (variable ?14C) and dissolved atmospheric CO2 (?14C approximately +30 ‰ in 2013). ?14Cchl values were also close to ?14Cbulk for E. latifolium (-215 ‰ in April and -199 ‰ in October) and Cladophora sp. (-210 ‰), whereas the ?14Cbulk value for Q. glauca (+27 ‰) was closer to ?14C for atmospheric CO2. Although the bulk isotopic composition of periphyton is recognised as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89 to 95 % algal carbon (derived from 14C-depleted DIC) and 5 to 11 % terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).

  10. 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.

  11. Species specific and environment induced variation of ?13C and ?15N in alpine plants

    PubMed Central

    Yang, Yang; Siegwolf, Rolf T. W.; Körner, Christian

    2015-01-01

    Stable carbon and nitrogen isotope signals in plant tissues integrate plant-environment interactions over long periods. In this study, we hypothesized that humid alpine life conditions are narrowing the scope for significant deviations from common carbon, water and nitrogen relations as captured by stable isotope signals. We explored the variation in ?13C and ?15N in 32 plant species from tissue type to ecosystem scale across a suite of locations at c. Two thousand five hundred meter elevation in the Swiss Alps. Foliar ?13C and ?15N varied among species by about 3–4‰ and 7–8‰ respectively. However, there was no overall difference in means of ?13C and ?15N for species sampled in different plant communities or when bulk plant dry matter harvests of different plant communities were compared. ?13C was found to be highly species specific, so that the ranking among species was mostly maintained across 11 habitats. However, ?15N varied significantly from place to place in all species (a range of 2.7‰) except in Fabaceae (Trifolium alpinum) and Juncaceae (Luzula lutea). There was also a substantial variation among individuals of the same species collected next to each other. No difference was found in foliar ?15N of non-legumes, which were either collected next to or away from the most common legume, T. alpinum. ?15N data place Cyperaceae and Juncaceae, just like Fabaceae, in a low discrimination category, well separated from other families. Soil ?15N was higher than in plants and increased with soil depth. The results indicate a high functional diversity in alpine plants that is similar to that reported for low elevation plants. We conclude that the surprisingly high variation in ?13C and ?15N signals in the studied high elevation plants is largely species specific (genetic) and insensitive to obvious environmental cues. PMID:26097487

  12. Changing gull diet in a changing world: a 150-year stable isotope (?13C, ?15N) record from feathers collected in the Pacific Northwest of North America.

    PubMed

    Blight, Louise K; Hobson, Keith A; Kyser, T Kurt; Arcese, Peter

    2015-04-01

    The world's oceans have undergone significant ecological changes following European colonial expansion and associated industrialization. Seabirds are useful indicators of marine food web structure and can be used to track multidecadal environmental change, potentially reflecting long-term human impacts. We used stable isotope (?(13)C, ?(15)N) analysis of feathers from glaucous-winged gulls (Larus glaucescens) in a heavily disturbed region of the northeast Pacific to ask whether diets of this generalist forager changed in response to shifts in food availability over 150 years, and whether any detected change might explain long-term trends in gull abundance. Sampled feathers came from birds collected between 1860 and 2009 at nesting colonies in the Salish Sea, a transboundary marine system adjacent to Washington, USA and British Columbia, Canada. To determine whether temporal trends in stable isotope ratios might simply reflect changes to baseline environmental values, we also analysed muscle tissue from forage fishes collected in the same region over a multidecadal timeframe. Values of ?(13)C and ?(15)N declined since 1860 in both subadult and adult gulls (?(13)C, ~ 2-6‰; ?(15)N, ~4-5‰), indicating that their diet has become less marine over time, and that birds now feed at a lower trophic level than previously. Conversely, forage fish ?(13)C and ?(15)N values showed no trends, supporting our conclusion that gull feather values were indicative of declines in marine food availability rather than of baseline environmental change. Gradual declines in feather isotope values are consistent with trends predicted had gulls consumed less fish over time, but were equivocal with respect to whether gulls had switched to a more garbage-based diet, or one comprising marine invertebrates. Nevertheless, our results suggest a long-term decrease in diet quality linked to declining fish abundance or other anthropogenic influences, and may help to explain regional population declines in this species and other piscivores. PMID:25369474

  13. Determination of gamma-ray widths in $^{15}$N using nuclear resonance fluorescence

    E-print Network

    T. Szücs; D. Bemmerer; A. Caciolli; Zs. Fülöp; R. Massarczyk; C. Michelagnoli; T. P. Reinhardt; R. Schwengner; M. P. Takács; C. A. Ur; A. Wagner; L. Wagner

    2015-10-27

    The stable nucleus $^{15}$N is the mirror of $^{15}$O, the bottleneck in the hydrogen burning CNO cycle. Most of the $^{15}$N level widths below the proton emission threshold are known from just one nuclear resonance fluorescence (NRF) measurement, with limited precision in some cases. A recent experiment with the AGATA demonstrator array determined level lifetimes using the Doppler Shift Attenuation Method (DSAM) in $^{15}$O. As a reference and for testing the method, level lifetimes in $^{15}$N have also been determined in the same experiment. The latest compilation of $^{15}$N level properties dates back to 1991. The limited precision in some cases in the compilation calls for a new measurement in order to enable a comparison to the AGATA demonstrator data. The widths of several $^{15}$N levels have been studied with the NRF method. The solid nitrogen compounds enriched in $^{15}$N have been irradiated with bremsstrahlung. The $\\gamma$-rays following the deexcitation of the excited nuclear levels were detected with four HPGe detectors. Integrated photon-scattering cross sections of ten levels below the proton emission threshold have been measured. Partial gamma-ray widths of ground-state transitions were deduced and compared to the literature. The photon scattering cross sections of two levels above the proton emission threshold, but still below other particle emission energies have also been measured, and proton resonance strengths and proton widths were deduced. Gamma and proton widths consistent with the literature values were obtained, but with greatly improved precision.

  14. Determination of gamma-ray widths in $^{15}$N using nuclear resonance fluorescence

    E-print Network

    Szücs, T; Caciolli, A; Fülöp, Zs; Massarczyk, R; Michelagnoli, C; Reinhardt, T P; Schwengner, R; Takács, M P; Ur, C A; Wagner, A; Wagner, L

    2015-01-01

    The stable nucleus $^{15}$N is the mirror of $^{15}$O, the bottleneck in the hydrogen burning CNO cycle. Most of the $^{15}$N level widths below the proton emission threshold are known from just one nuclear resonance fluorescence (NRF) measurement, with limited precision in some cases. A recent experiment with the AGATA demonstrator array determined level lifetimes using the Doppler Shift Attenuation Method (DSAM) in $^{15}$O. As a reference and for testing the method, level lifetimes in $^{15}$N have also been determined in the same experiment. The latest compilation of $^{15}$N level properties dates back to 1991. The limited precision in some cases in the compilation calls for a new measurement in order to enable a comparison to the AGATA demonstrator data. The widths of several $^{15}$N levels have been studied with the NRF method. The solid nitrogen compounds enriched in $^{15}$N have been irradiated with bremsstrahlung. The $\\gamma$-rays following the deexcitation of the excited nuclear levels were dete...

  15. Determination of ? -ray widths in 15N using nuclear resonance fluorescence

    NASA Astrophysics Data System (ADS)

    Szücs, T.; Bemmerer, D.; Caciolli, A.; Fülöp, Zs.; Massarczyk, R.; Michelagnoli, C.; Reinhardt, T. P.; Schwengner, R.; Takács, M. P.; Ur, C. A.; Wagner, A.; Wagner, L.

    2015-07-01

    Background: The stable nucleus 15N is the mirror of 15O, the bottleneck in the hydrogen burning CNO cycle. Most of the 15N level widths below the proton emission threshold are known from just one nuclear resonance fluorescence (NRF) measurement, with limited precision in some cases. A recent experiment with the AGATA demonstrator array determined level lifetimes using the Doppler shift attenuation method in 15O. As a reference and for testing the method, level lifetimes in 15N have also been determined in the same experiment. Purpose: The latest compilation of 15N level properties dates back to 1991. The limited precision in some cases in the compilation calls for a new measurement to enable a comparison to the AGATA demonstrator data. The widths of several 15N levels have been studied with the NRF method. Method: The solid nitrogen compounds enriched in 15N have been irradiated with bremsstrahlung. The ? rays following the deexcitation of the excited nuclear levels were detected with four high-purity germanium detectors. Results: Integrated photon-scattering cross sections of 10 levels below the proton emission threshold have been measured. Partial ? -ray widths of ground-state transitions were deduced and compared to the literature. The photon-scattering cross sections of two levels above the proton emission threshold, but still below other particle emission energies have also been measured, and proton resonance strengths and proton widths were deduced. Conclusions: Gamma and proton widths consistent with the literature values were obtained, but with greatly improved precision.

  16. Stable ?15N and ?13C isotope ratios in aquatic ecosystems

    PubMed Central

    Wada, Eitaro

    2009-01-01

    In the past 20 years, rapid progress in stable isotope (SI) studies has allowed scientists to observe natural ecosystems from entirely new perspectives. This report addresses the fundamental concepts underlying the use of the SI ratio. The unique characteristics of the SI ratio make it an interdisciplinary parameter that acts as a chemical fingerprint of biogenic substances and provides a key to the world of isotopomers. Variations in SI ratios of biogenic substances depend on the isotopic compositions of reactants, the pathways and kinetic modes of reaction dynamics, and the physicochemical conditions. In fact, every biogenic material has its own isotopic composition, its “dynamic SI fingerprint”, which is governed by its function and position in the material flow. For example, the relative SI ratio in biota is determined by dietary lifestyle, e.g., the modes of drinking, eating, and excreting, and appears highly regular due to the physicochemical differences of isotopomers. Our primary goal here is to elucidate the general principals of isotope partitioning in major biophilic elements in molecules, biogenic materials, and ecosystems (Wada, E. et al., 1995). To this end, the nitrogen and carbon SI distribution ratios (?15N and ?13C, respectively) are used to examine materials cycling, food web structures, and their variability in various kinds of watershed-including aquatic ecosystems to elucidate an “isotopically ordered world”. PMID:19282646

  17. Using PLFA Biomarkers and Natural Abundance Stable and Radiocarbon Isotopes to Characterize the Microbial Ecology and Metabolism of Methane Cycling

    NASA Astrophysics Data System (ADS)

    Mills, C. T.; Mandernack, K. W.; Slater, G. F.; Dias, R. F.

    2008-12-01

    Methane generated in the subsurface is a major source of atmospheric CH4, but its release is mitigated by CH4-oxidizing bacteria (methanotrophs). Therefore, it is important to understand the ecology of methanotroph communities in various environments. Phospholipid fatty acid (PLFA) analyses are a particularly useful method for characterizing these communities for two reasons: (1) Many type I and II methanotrophs produce specific PLFA biomarkers that can be used to estimate their populations, and (2) because CH4 is often very depleted in 13C and sometimes 14C, natural abundance ?13CPLFA and ?14CPLFA values can be used to trace the flow of CH4- derived carbon through microbial ecosystems. We used these tools to evaluate the role of methanotrophs in carbon flow in three different environments: (1) a soil column overlying a coal bed methane (CBM) seep in southwest CO, and pristine, oligotrophic groundwaters within (2) sedimentary and (3) granitic host rocks in Japan. In the soil column impacted by CBM seepage, concentrations of the biomarker PLFAs for type I (16:1?8cis) and type II (18:1?8cis) methanotrophs were as high as 13 and 18 nmoles (g dry soil)-1, respectively. Depth profiles of methanotroph PLFA concentrations varied over different sampling dates indicating dynamic populations. ?13CPLFA values of the CBM soils (-25.1 to - 66.9‰) were substantially more negative than those for the control soil (-14.5 to -32.5‰) indicating that CBM is an important carbon source for the CBM-impacted soil microbial community. ?14CPLFA values (-351 to -936‰) indicate the importance of 14C-dead CBM as a carbon source to the microbial communities, contributing 32 to 66% of total carbon in PLFA structures isolated from shallow soils and 67 to 97% for those isolated from deeper soils. The biomarker for type II methanotrophs, comprised 3 and 18% of total PLFAs in sedimentary and granitic groundwaters, respectively. The ?14C values determined for type II methanotroph PLFAs in the sedimentary (- 861‰) and granite (-867‰) waters were very similar to the ?14C values of dissolved inorganic carbon (DIC) in each water (ca -850‰) suggesting that type II methanotrophs ultimately derive all of their carbon from DIC. In contrast, ?13C values of type II PLFAs in the sedimentary (- 93‰) and granite (-60‰) waters indicate that these organisms use different carbon assimilation schemes in each environment. These studies show the utility of PLFA biomarkers and ?13CPLFA and ?14CPLFA values to characterize the in situ metabolisms of methanotrophic bacteria and overall CH4 recycling in diverse environments.

  18. Estimating modal abundances from the spectra of natural and laboratory pyroxene mixtures using the modified Gaussian model

    NASA Technical Reports Server (NTRS)

    Sunshine, Jessica M.; Pieters, Carle M.

    1993-01-01

    The modified Gaussian model (MGM) is used to explore spectra of samples containing multiple pyroxene components as a function of modal abundance. The MGM allows spectra to be analyzed directly, without the use of actual or assumed end-member spectra and therefore holds great promise for remote applications. A series of mass fraction mixtures created from several different particle size fractions are analyzed with the MGM to quantify the properties of pyroxene mixtures as a function of both modal abundance and grain size. Band centers, band widths, and relative band strengths of absorptions from individual pyroxenes in mixture spectra are found to be largely independent of particle size. Spectral properties of both zoned and exsolved pyroxene components are resolved in exsolved samples using the MGM, and modal abundances are accurately estimated to within 5-10 percent without predetermined knowledge of the end-member spectra.

  19. N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

    SciTech Connect

    Thorn, Kevin A.; Cox, Larry G.

    2009-02-28

    The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS ¹?N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by ¹?N NMR. Liquid state ¹?N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection (¹H–¹?N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

  20. Bacterial abundance and aerobic microbial activity across natural and oyster aquaculture habitats during summer conditions in a northeastern Pacific estuary.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We measured sediment properties and the abundance and functional diversity of microbes in Willapa Bay, Washington, USA, to test the response of sediment microbes to oyster aquaculture. Sites spanned the estuary gradient (salinity 24-30) and six different habitat types: eelgrass (Zostera marina), uns...

  1. Why is Mineral-Associated Organic Matter Enriched in 15N? Evidence from Grazed Pasture Soil

    NASA Astrophysics Data System (ADS)

    Baisden, W. T.; Wells, N. S.; Mudge, P. L.; Clough, T. J.; Schipper, L. A.; Ghani, A.; Stevenson, B.

    2014-12-01

    Throughout the scientific literature, measurements across soil depth and density fractions suggest that, with few exceptions, mineral-associated organic matter (OM) has higher ?15N than non-mineral-associated OM. This implies that the ?15N difference between N inputs and mineral-stabilized OM may characterize the microbial processes involved in stabilization and mineral association. Yet current understanding of observed N isotope fractionation in terrestrial ecosystems suggests the large isotope effects are expressed during inorganic N transformations from NH4 to gaseous loss pathways of NH3 volatilization and denitrification. How can the relative importance of N isotope fractionation during OM stabilization versus loss pathways be resolved? We recently examined N isofluxes when a temporary nitrogen excess is created by urine deposition in a New Zealand dairy pasture. We found that the N isotopic composition of volatilized NH3, and NO3 available for leaching or denitrification could not be linked back to the added N using Rayleigh distillation models. Instead, the results imply that the added N was immobilized, and the N available for losses was increasingly derived from mineralization of organic matter during the course of the experiment. These results are consistent with recent evidence of enhanced OM mineralization in urine patches, understanding of N isotope mass balances and long-standing evidence that gross mineralization and immobilization fluxes greatly exceed net mineralization and nitrification, except at very high N saturation. These results suggest that where 15N enrichment occurs due to fractionating loss pathways, the isotope effects are primarily transmitted to immobilized N, forming 15N enriched stabilized OM. This further explains earlier findings that the ?15N of soil OM represents an integrated indicator of losses, reflecting the intensity and duration of pastoral agriculture. We suggest that development of an indicator based on ?15N in mineral-associated OM might relate mineralization rates to the ?15N of stabilized or immobilized N.

  2. Sewage derive [sup 15]N in the Baltic traced in fucus

    SciTech Connect

    Hobbie, J.E.; Fry, B. ); Larsson, U.; Elmgren, R. )

    1990-01-09

    Himmerfjarden, a fjord-like bay on the eastern shore of the Baltic, receives treated sewage from 250,000 inhabitants. Because the inorganic N in the effluent is enriched in [sup 15]N through denitrification, nitrification, and ammonia volatilization, an analysis of the distribution of [sup 15]N in the Bay tells how far from the source the sewage nitrogen moves. The attached macroalga Fucus vesiculosus was collected in early May from rocky shore at 0-0.5 m depth and the [sup 15]N content of the tips of the fronds analyzed. This N represents uptake and storage during the previous six months and growth during March and April. The [delta][sup 15]N was uniformly high (11-13[per thousand]) in the main body of the Bay within 15 km from the sewage source. Beyond 15 km values decreased with distance to a low of 4.6[per thousand] at 35 km, where the Bay ends and the coastal waters begin. Using the 11-13 and 4.6[per thousand] as endmembers, the percentage of sewage N making up the Fucus at any point may be calculated. The [delta][sub 15]N of particulate organic matter in the offshore Baltic waters was around 0[per thousand] and Fucus had an [delta][sup 15]N about 1.5[per thousand] higher than the POM. From this and other evidence we conclude that there is a belt of coastal water with an elevated [delta][sup 15]N lying along the east coast of the Baltic. This presumably derives from sewage and perhaps from agriculture and is potentially of use as a tracer of coastal zone/pelagic zone interactions.

  3. The C14N/C15N Ratio in Diffuse Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Ritchey, A. M.; Federman, S. R.; Lambert, D. L.

    2015-05-01

    We report the first detection of C15N in diffuse molecular gas from a detailed examination of CN absorption lines in archival spectra, obtained with the Ultraviolet and Visual Echelle Spectrograph of the Very Large Telescope of stars probing local diffuse clouds. Absorption from the C15N isotopologue is confidently detected (at ? 4? ) in three out of the four directions studied and appears as a very weak feature between the main 12CN and 13CN absorption components. Column densities for each CN isotopologue are determined through profile fitting, after accounting for weak additional line-of-sight components of 12CN, which are seen in the absorption profiles of CH and CH+ as well. The weighted mean value of C14N/C15N for the three sight lines with detections of C15N is 274 ± 18. Since the diffuse molecular clouds toward our target stars have relatively high gas kinetic temperatures and relatively low visual extinctions, their C14N/C15N ratios should not be affected by chemical fractionation. The mean C14N/C15N ratio that we obtain should therefore be representative of the ambient 14N/15N ratio in the local interstellar medium. Indeed, our mean value agrees well with that derived from millimeter-wave observations of CN, HCN, and HNC in local molecular clouds. Based on observations made with the Very Large Telescope of the European Southern Observatory, Paranal, Chile, under programs 065.I-0526, 071.C-0367, 071.C-0513, 076.C-0431, and 092.C-0019.

  4. Structure effects in the $^{15}$N($n,?$)$^{16}$N radiative capture reaction from the Coulomb dissociation of $^{16}$N

    E-print Network

    Neelam; Shubhchintak; R. Chatterjee

    2015-10-10

    Purpose : The aim of this paper is to calculate the $^{15}$N($n, \\gamma$)$^{16}$N radiative capture cross section and its subsequent reaction rate by an indirect method and in that process investigate the effects of spectroscopic factors of different levels of $^{16}$N to the cross section. Method : A fully quantum mechanical Coulomb breakup theory under the aegis of post-form distorted wave Born approximation is used to calculate the Coulomb breakup of $^{16}$N on Pb at 100 MeV/u. This is then related to the photodisintegration cross section of $^{16}$N($\\gamma, n$)$^{15}$N and subsequently invoking the principle of detailed balance, the $^{15}$N($n, \\gamma$)$^{16}$N capture cross section is calculated. Results : The non-resonant capture cross section is calculated with spectroscopic factors from the shell model and those extracted (including uncertainties) from two recent experiments. The data seems to favor a more single particle nature for the low-lying states of $^{16}$N. The total neutron capture rate is also calculated by summing up non-resonant and resonant (significant only at temperatures greater than 1 GK) contributions and comparison is made with other charged particle capture rates. In the typical temperature range of $0.1-1.2$ GK, almost all the contribution to the reaction rate comes from capture cross sections below 0.25 MeV. Conclusion : We have attempted to resolve the discrepancy in the spectroscopic factors of low-lying $^{16}$N levels and conclude that it would certainly be useful to perform a Coulomb dissociation experiment to find the low energy capture cross section for the reaction, especially below 0.25 MeV.

  5. Comparison of pollinators and natural enemies: a meta-analysis of landscape and local effects on abundance and richness in crops.

    PubMed

    Shackelford, Gorm; Steward, Peter R; Benton, Tim G; Kunin, William E; Potts, Simon G; Biesmeijer, Jacobus C; Sait, Steven M

    2013-11-01

    To manage agroecosystems for multiple ecosystem services, we need to know whether the management of one service has positive, negative, or no effects on other services. We do not yet have data on the interactions between pollination and pest-control services. However, we do have data on the distributions of pollinators and natural enemies in agroecosystems. Therefore, we compared these two groups of ecosystem service providers, to see if the management of farms and agricultural landscapes might have similar effects on the abundance and richness of both. In a meta-analysis, we compared 46 studies that sampled bees, predatory beetles, parasitic wasps, and spiders in fields, orchards, or vineyards of food crops. These studies used the proximity or proportion of non-crop or natural habitats in the landscapes surrounding these crops (a measure of landscape complexity), or the proximity or diversity of non-crop plants in the margins of these crops (a measure of local complexity), to explain the abundance or richness of these beneficial arthropods. Compositional complexity at both landscape and local scales had positive effects on both pollinators and natural enemies, but different effects on different taxa. Effects on bees and spiders were significantly positive, but effects on parasitoids and predatory beetles (mostly Carabidae and Staphylinidae) were inconclusive. Landscape complexity had significantly stronger effects on bees than it did on predatory beetles and significantly stronger effects in non-woody rather than in woody crops. Effects on richness were significantly stronger than effects on abundance, but possibly only for spiders. This abundance-richness difference might be caused by differences between generalists and specialists, or between arthropods that depend on non-crop habitats (ecotone species and dispersers) and those that do not (cultural species). We call this the 'specialist-generalist' or 'cultural difference' mechanism. If complexity has stronger effects on richness than abundance, it might have stronger effects on the stability than the magnitude of these arthropod-mediated ecosystem services. We conclude that some pollinators and natural enemies seem to have compatible responses to complexity, and it might be possible to manage agroecosystems for the benefit of both. However, too few studies have compared the two, and so we cannot yet conclude that there are no negative interactions between pollinators and natural enemies, and no trade-offs between pollination and pest-control services. Therefore, we suggest a framework for future research to bridge these gaps in our knowledge. PMID:23578337

  6. Accurate measurement of 15N-13C residual dipolar couplings in nucleic acids.

    PubMed

    Jaroniec, Christopher P; Boisbouvier, Jérôme; Tworowska, Izabela; Nikonowicz, Edward P; Bax, Ad

    2005-03-01

    New 3D HCN quantitative J (QJ) pulse schemes are presented for the precise and accurate measurement of one-bond 15N1/9-13C1', 15N1/9-13C6/8, and 15N1/9-13C2/4 residual dipolar couplings (RDCs) in weakly aligned nucleic acids. The methods employ 1H-13C multiple quantum (MQ) coherence or TROSY-type pulse sequences for optimal resolution and sensitivity. RDCs are obtained from the intensity ratio of H1'-C1'-N1/9 (MQ-HCN-QJ) or H6/8-C6/8-N1/9 (TROSY-HCN-QJ) correlations in two interleaved 3D NMR spectra, with dephasing intervals of zero (reference spectrum) and approximately 1/(2J(NC)) (attenuated spectrum). The different types of 15N-13C couplings can be obtained by using either the 3D MQ-HCN-QJ or TROSY-HCN-QJ pulse scheme, with the appropriate setting of the duration of the constant-time 15N evolution period and the offset of two frequency-selective 13C pulses. The methods are demonstrated for a uniformly 13C, 15N-enriched 24-nucleotide stem-loop RNA sequence, helix-35psi, aligned in the magnetic field using phage Pf1. For measurements of RDCs systematic errors are found to be negligible, and experiments performed on a 1.5 mM helix-35psi sample result in an estimated precision of ca. 0.07 Hz for 1D(NC), indicating the utility of the measured RDCs in structure validation and refinement. Indeed, for a complete set of 15N1/9-13C1', 15N1/9-13C6/8, and 15N1/9-13C2/4 dipolar couplings obtained for the stem nucleotides, the measured RDCs are in excellent agreement with those predicted for an NMR structure of helix-35psi, refined using independently measured observables, including 13C-1H, 13C-13C and 1H-1H dipolar couplings. PMID:15803396

  7. Structure effects in the 15N(n ,? )16N radiative capture reaction from the Coulomb dissociation of 16N

    NASA Astrophysics Data System (ADS)

    Neelam, Shubhchintak, Chatterjee, R.

    2015-10-01

    Background: The 15N(n ,? )16N reaction plays an important role in red giant stars and also in inhomogeneous big bang nucleosynthesis. However, there are controversies regarding spectroscopic factors of the four low-lying states of 16N, which have direct bearing on the total direct capture cross section and also on the reaction rate. Direct measurements of the capture cross section at low energies are scarce and available only at three energies below 500 keV. Purpose: The aim of this paper is to calculate the 15N(n ,? )16N radiative capture cross section and its subsequent reaction rate by an indirect method and in that process investigate the effects of spectroscopic factors of different levels of 16N to the cross section. Method: A fully quantum mechanical Coulomb breakup theory under the aegis of post-form distorted wave Born approximation is used to calculate the Coulomb breakup of 16N on Pb at 100 MeV/u . This is then related to the photodisintegration cross section of 16N(? ,n )15N and subsequently invoking the principle of detailed balance, the 15N(n ,? )16N capture cross section is calculated. Results: The nonresonant capture cross section is calculated with spectroscopic factors from the shell model and those extracted (including uncertainties) from two recent experiments. The data seem to favor a more single particle nature for the low-lying states of 16N. The total neutron capture rate is also calculated by summing up nonresonant and resonant (significant only at temperatures greater than 1 GK) contributions and comparison is made with other charged particle capture rates. In the typical temperature range of 0.1 -1.2 GK, almost all the contributions to the reaction rate come from capture cross sections below 0.25 MeV. Conclusion: We have attempted to resolve the discrepancy in the spectroscopic factors of low-lying 16N levels and conclude that it would certainly be useful to perform a Coulomb dissociation experiment to find the low energy capture cross section for the reaction, especially below 0.25 MeV.

  8. Multiple regression models of ?13C and ?15N for fish populations in the eastern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Radabaugh, Kara R.; Peebles, Ernst B.

    2014-08-01

    Multiple regression models were created to explain spatial and temporal variation in the ?13C and ?15N values of fish populations on the West Florida Shelf (eastern Gulf of Mexico, USA). Extensive trawl surveys from three time periods were used to acquire muscle samples from seven groundfish species. Isotopic variation (?13Cvar and ?15Nvar) was calculated as the deviation from the isotopic mean of each fish species. Static spatial data and dynamic water quality parameters were used to create models predicting ?13Cvar and ?15Nvar in three fish species that were caught in the summers of 2009 and 2010. Additional data sets were then used to determine the accuracy of the models for predicting isotopic variation (1) in a different time period (fall 2010) and (2) among four entirely different fish species that were collected during summer 2009. The ?15Nvar model was relatively stable and could be applied to different time periods and species with similar accuracy (mean absolute errors 0.31-0.33‰). The ?13Cvar model had a lower predictive capability and mean absolute errors ranged from 0.42 to 0.48‰. ?15N trends are likely linked to gradients in nitrogen fixation and Mississippi River influence on the West Florida Shelf, while ?13C trends may be linked to changes in algal species, photosynthetic fractionation, and abundance of benthic vs. planktonic basal resources. These models of isotopic variability may be useful for future stable isotope investigations of trophic level, basal resource use, and animal migration on the West Florida Shelf.

  9. Oak loss increases foliar nitrogen, ?(15)N and growth rates of Betula lenta in a northern temperate deciduous forest.

    PubMed

    Falxa-Raymond, Nancy; Patterson, Angelica E; Schuster, William S F; Griffin, Kevin L

    2012-09-01

    Oak forests dominate much of the eastern USA, but their future is uncertain due to a number of threats and widespread failure of oak regeneration. A sudden loss of oaks (Quercus spp.) could be accompanied by major changes in forest nitrogen (N) cycles with important implications for plant nutrient uptake and tree species composition. In this study, we measured the changes in N use and growth rates of black birch trees (Betula lenta L.) following oak girdling at the Black Rock Forest in southeastern New York, USA. Data were collected from nine experimental plots composed of three treatments: 100% oaks girdled (OG), 50% oaks girdled (O50) and control (C). Foliar N concentration and foliar (15)N abundance increased significantly in the oak-girdled plots relative to the control, indicating that the loss of oaks significantly altered N cycling dynamics. As mineralization and nitrification rates increase following oak loss, black birch trees increase N absorption as indicated by higher foliar N content and increased growth rates. Foliar N concentration increased by 15.5% in the O50 and 30.6% in the OG plots relative to the control, while O50 and OG plots were enriched in (15)N by 1.08‰ and 3.33‰, respectively (P?

  10. Seasonal Abundance of the Greenbug and its Natural Enemies in Grain Sorghum in the Texas High Plains. 

    E-print Network

    Teetes, George L.; Lopez, Ector G.; Schaefer, Curtis A.

    1975-01-01

    August as the total greenbug popu- lstion was declining rapidly. Lysiphlebus testaceipes (Cresson) was the most abundant primary parasite of the greenbug. Other primary parasites reared from mummies were Diaeretiella rapae (51' Intosh) and Aphelinum... nigritus (Howard). Hyperparasites (parasites of parasites) reared from mummies were Charips sp., Pachj~neuron siphonophorae (Ashmead), Asaphes lucens ( Provancher), and Aphidencyrtus aphidivorus (Mayr). Charips sp., ar~d P. siphonophorae were the most...

  11. First results on the incorporation and excretion of 15N from orally administered urea in lactating pony mares.

    PubMed

    Schubert, R; Zander, R; Gruhn, K; Hennig, A

    1991-05-01

    Two lactating pony mares were given oral offers of 20 g 15N urea [95 atom-% 15N-excess (15N')] on 6 subsequent days. About 80% of the consumed 15N' were excreted via urine and faeces, but only about 2% via milk. The 15N' secreted via milk-lysine only amounted to 0.04% of the 15N' intake. The recovery was about 90% in each case. Tissues with active metabolism had an unexpectedly high labelling (greater than 0.3 atom-% 15N'). The low extent of the conversion of oral urea N into milk-lysine speaks against an essential participation of the enteral synthesis in meeting the amino acid requirement of lactating mares. It was already concluded from this results that the determination of the amino acid requirement will be necessary for this group of performance. PMID:1888274

  12. Deuterium abundances

    E-print Network

    M. Lemoine; J. Audouze; L. Ben Jaffel; P. Feldman; R. Ferlet; G. Hebrard; E. B. Jenkins; C. Mallouris; W. Moos; K. Sembach; G. Sonneborn; A. Vidal-Madjar; D. G. York

    1999-03-02

    We discuss the measurements of deuterium abundances in high redshift quasar absorbers, in the solar system and in the interstellar medium. We present new results that indicate spatial variations of the deuterium abundance in the interstellar medium at the level of 50% over scales possibly as small as 10 pc, and discuss plausible causes for the origin of these variations.

  13. A density functional study of 15N chemical shielding tensors in quinolines

    NASA Astrophysics Data System (ADS)

    Behzadi, Hadi; Esrafili, Mehdi D.; Beheshtian, Javad; Hadipour, Nasser L.; van der Spoel, David

    2009-07-01

    DFT calculations were carried out to characterize the 15N shielding tensors in quinolines. This computational study is intended to shed light on the differences between two groups of quinolines: series A (7-chloro 4-aminoalkyls quinolines) and series B (quinolines, 3-, 5-, 6-, 8-amino quinolines and 4,8-dichloro quinoline). Unlike the quinolines in series B, the series A quinolines show considerable ?-hematin inhibition activity which is essential for quinoline-based drugs. The results show that the substitution position significantly affects the ?11 and ?22 components of 15N shielding tensors of quinolines. The 15N shielding components are noticeably different for the two series and can be related to their ability to interact with hematin.

  14. Biological N Demand and the Interpretation of ?15N in soils and sediments. (Invited)

    NASA Astrophysics Data System (ADS)

    Inglett, P.

    2010-12-01

    Many studies in aquatic systems utilize changes in isotopic ratios of organic matter to infer N sources and cycling, however the interpretation and processes invoked to explain relative patterns and changes is often conflicting between studies. Here we present a discussion of how N demand in contrasting systems leads to differences in soil/sediment ?15N arising from nitrogen fixation and discrimination during N uptake/assimilation into autotrophic biomass N. Both processes are affected by phosphorus level, the primary determinant of N limitation. Mineralization and laboratory plant growth studies confirm the magnitude of macrophyte discrimination relative to diagenesis in affecting soil ?15N in a wetland system. Results of these studies have implications for interpretation of ?15N in aquatic systems dominated by organic N transformation and accumulation.

  15. Biosynthesis of calystegines: 15N NMR and kinetics of formation in root cultures of Calystegia sepium.

    PubMed

    Scholl, Yvonne; Schneider, Bernd; Dräger, Birgit

    2003-02-01

    Calystegines are nortropane alkaloids bearing between three and five hydroxyl groups in various positions. [15N]Tropinone was administered to root cultures of Calystegia sepium and the incorporation into calystegines was followed. Increase of label in calystegines was measured by one-dimensional 15N NMR and inverse-detected 2D NMR techniques. The results show that tropinone and pseudotropine are metabolites in the biosynthetic pathway of calystegines. The velocity of calystegine accumulation was followed kinetically by transfer of root cultures from 15N-enriched medium to 14N-medium and analysis by GC-MS. A constant calystegine formation with no interference by excretion or degradation was observed. A biosynthetic rate for individual calystegines at each time point was calculated, the maximum was 0.4 mg/day/g of biomass. This allowed the velocity of individual biosynthetic steps to be estimated. PMID:12620344

  16. Hyperpolarized 15N-pyridine Derivatives as pH-Sensitive MRI Agents

    PubMed Central

    Jiang, Weina; Lumata, Lloyd; Chen, Wei; Zhang, Shanrong; Kovacs, Zoltan; Sherry, A. Dean; Khemtong, Chalermchai

    2015-01-01

    Highly sensitive MR imaging agents that can accurately and rapidly monitor changes in pH would have diagnostic and prognostic value for many diseases. Here, we report an investigation of hyperpolarized 15N-pyridine derivatives as ultrasensitive pH-sensitive imaging probes. These molecules are easily polarized to high levels using standard dynamic nuclear polarization (DNP) techniques and their 15N chemical shifts were found to be highly sensitive to pH. These probes displayed sharp 15N resonances and large differences in chemical shifts (?? >90?ppm) between their free base and protonated forms. These favorable features make these agents highly suitable candidates for the detection of small changes in tissue pH near physiological values. PMID:25774436

  17. The loss of organic nitrogen during marine primary production may be significantly overestimated when using 15N substrates

    PubMed Central

    Flynn, K. J.; Berry, L. S.

    1999-01-01

    Field studies indicate that natural phytoplankton populations may release very significant amounts (20 to 40%) of newly assimilated dissolved inorganic nitrogen (DIN) as dissolved organic nitrogen (DON). In laboratory cultures, however, it is usually possible to account for at least 90% of nitrogen added to the system as DIN plus cell nitrogen. Here we show that the bulk of the missing nitrogen may be accounted for as dissolved free and dissolved combined amino acids. In cultures (which usually have a biomass density at least an order of magnitude greater than is present in offshore waters), the contribution of DON to system nitrogen thus appears to be minor. It is proposed that this difference may be explained if the levels of DON represent equilibrium between release–leakage and transport back into the algae. It is demonstrated, using a dynamic model of algal nitrogen physiology, that this mechanism can explain both laboratory and field observations. Simulations of incubations with DI15N reproduce the reported levels of loss in field incubations. However, because of isotope disequilibria between system components the 15N protocol may significantly overestimate the net loss of nitrogen from the algal cells. The arguments apply equally to studies of bacterial production of DON and to questions concerning the release of other dissolved organics by healthy phytoplankton. The significance of dynamic equilibria between the organisms and the medium may be missed in laboratory studies conducted with high biomass cultures.

  18. 15N Fractionation in Star-Forming Regions and Solar System Objects

    NASA Technical Reports Server (NTRS)

    Wirstrom, Eva; Milam, Stefanie; Adande, GIlles; Charnley, Steven; Cordiner, Martin

    2015-01-01

    A central issue for understanding the formation and evolution of matter in the early Solar System is the relationship between the chemical composition of star-forming interstellar clouds and that of primitive Solar System materials. The pristinemolecular content of comets, interplanetary dust particles and carbonaceous chondrites show significant bulk nitrogen isotopic fractionation relative to the solar value, 14N15N 440. In addition, high spatial resolution measurements in primitive materials locally show even more extreme enhancements of 14N15N 100.

  19. Abiotic and biotic factors associated with the presence of Anopheles arabiensis immatures and their abundance in naturally occurring and man-made aquatic habitats

    PubMed Central

    2012-01-01

    Background Anopheles arabiensis (Diptera: Culicidae) is a potential malaria vector commonly present at low altitudes in remote areas in Reunion Island. Little attention has been paid to the environmental conditions driving larval development and abundance patterns in potential habitats. Two field surveys were designed to determine whether factors that discriminate between aquatic habitats with and without An. arabiensis larvae also drive larval abundance, comparatively in man-made and naturally occurring habitats. Methods In an initial preliminary survey, a representative sample of aquatic habitats that would be amenable to an intensive long-term study were selected and divided into positive and negative sites based on the presence or absence of Anopheles arabiensis larvae. Subsequently, a second survey was prompted to gain a better understanding of biotic and abiotic drivers of larval abundance, comparatively in man-made and naturally occurring habitats in the two studied locations. In both surveys, weekly sampling was performed to record mosquito species composition and larval density within individual habitats, as well as in situ biological characteristics and physico-chemical properties. Results Whilst virtually any stagnant water body could be a potential breeding ground for An. arabiensis, habitats occupied by their immatures had different structural and biological characteristics when compared to those where larvae were absent. Larval occurrence seemed to be influenced by flow velocity, macrofauna diversity and predation pressure. Interestingly, the relative abundance of larvae in man-made habitats (average: 0.55 larvae per dip, 95%CI [0.3–0.7]) was significantly lower than that recorded in naturally occurring ones (0.74, 95%CI [0.5–0.8]). Such differences may be accounted for in part by varying pressures that could be linked to a specific habitat. Conclusions If the larval ecology of An. arabiensis is in general very complex and factors affecting breeding site productivity sometimes not easy to highlight, our results, however, highlight lower populations of An. arabiensis immatures compared to those reported in comparable studies conducted in the African continent. Overall, this low larval abundance, resulting from both abiotic and biotic factors, suggests that vector control measures targeting larval habitats are likely to be successful in Reunion, but these could be better implemented by taking environmental variability into account. PMID:22608179

  20. Leaf ?(15)N as a physiological indicator of the responsiveness of N2-fixing alfalfa plants to elevated [CO2], temperature and low water availability.

    PubMed

    Ariz, Idoia; Cruz, Cristina; Neves, Tomé; Irigoyen, Juan J; Garcia-Olaverri, Carmen; Nogués, Salvador; Aparicio-Tejo, Pedro M; Aranjuelo, Iker

    2015-01-01

    The natural (15)N/(14)N isotope composition (?(15)N) of a tissue is a consequence of its N source and N physiological mechanisms in response to the environment. It could potentially be used as a tracer of N metabolism in plants under changing environmental conditions, where primary N metabolism may be complex, and losses and gains of N fluctuate over time. In order to test the utility of ?(15)N as an indicator of plant N status in N2-fixing plants grown under various environmental conditions, alfalfa (Medicago sativa L.) plants were subjected to distinct conditions of [CO2] (400 vs. 700 ?mol mol(-1)), temperature (ambient vs. ambient +4°C) and water availability (fully watered vs. water deficiency-WD). As expected, increased [CO2] and temperature stimulated photosynthetic rates and plant growth, whereas these parameters were negatively affected by WD. The determination of ?(15)N in leaves, stems, roots, and nodules showed that leaves were the most representative organs of the plant response to increased [CO2] and WD. Depletion of heavier N isotopes in plants grown under higher [CO2] and WD conditions reflected decreased transpiration rates, but could also be related to a higher N demand in leaves, as suggested by the decreased leaf N and total soluble protein (TSP) contents detected at 700 ?mol mol(-1) [CO2] and WD conditions. In summary, leaf ?(15)N provides relevant information integrating parameters which condition plant responsiveness (e.g., photosynthesis, TSP, N demand, and water transpiration) to environmental conditions. PMID:26322051

  1. Leaf ?15N as a physiological indicator of the responsiveness of N2-fixing alfalfa plants to elevated [CO2], temperature and low water availability

    PubMed Central

    Ariz, Idoia; Cruz, Cristina; Neves, Tomé; Irigoyen, Juan J.; Garcia-Olaverri, Carmen; Nogués, Salvador; Aparicio-Tejo, Pedro M.; Aranjuelo, Iker

    2015-01-01

    The natural 15N/14N isotope composition (?15N) of a tissue is a consequence of its N source and N physiological mechanisms in response to the environment. It could potentially be used as a tracer of N metabolism in plants under changing environmental conditions, where primary N metabolism may be complex, and losses and gains of N fluctuate over time. In order to test the utility of ?15N as an indicator of plant N status in N2-fixing plants grown under various environmental conditions, alfalfa (Medicago sativa L.) plants were subjected to distinct conditions of [CO2] (400 vs. 700 ?mol mol?1), temperature (ambient vs. ambient +4°C) and water availability (fully watered vs. water deficiency—WD). As expected, increased [CO2] and temperature stimulated photosynthetic rates and plant growth, whereas these parameters were negatively affected by WD. The determination of ?15N in leaves, stems, roots, and nodules showed that leaves were the most representative organs of the plant response to increased [CO2] and WD. Depletion of heavier N isotopes in plants grown under higher [CO2] and WD conditions reflected decreased transpiration rates, but could also be related to a higher N demand in leaves, as suggested by the decreased leaf N and total soluble protein (TSP) contents detected at 700 ?mol mol?1 [CO2] and WD conditions. In summary, leaf ?15N provides relevant information integrating parameters which condition plant responsiveness (e.g., photosynthesis, TSP, N demand, and water transpiration) to environmental conditions. PMID:26322051

  2. Biogenic N2 and ?15 N-N2 As Proxies for N-Loss in the Eastern Tropical North Pacific: A Lagrangian Float Experiment.

    NASA Astrophysics Data System (ADS)

    Bourbonnais, A.; Altabet, M. A.; McNeil, C. L.; Larkum, J.; Reed, A. C.; D'Asaro, E. A.

    2014-12-01

    A large portion of the ocean's bioavailable N, a macronutrient limiting primary productivity, is lost in oxygen minimum zones (OMZs). Mesoscale processes (e.g. eddies, meandering currents), can transport highly productive waters from the coasts, increasing the downward flux of organic material, a substrate for N-loss, and thus can act as N-loss hotspots in OMZs. However, due to their transient nature, these mesoscale events are difficult to monitor using traditional shipboard observations. We deployed biogeochemical Lagrangian floats in the eastern tropical North Pacific during a research cruise in May/June 2014, where transport of high chlorophyll waters from the coast were inferred from satellite imagery. These Lagrangian floats are automonous platforms with the ability to follow isopycnals and were equipped with a suite of gas tension devices and other sensors to measure N2(g), O2, NO3- and NO2- concentrations. We concurrently collected discrete samples to calibrate and complement float measurements. We present here biogenic N2, i.e. N2 produced by local N-loss processes and derived from measured N2/Ar and ?15N-N2 anomaly, i.e. the difference between ?15N-N2 observed and at equilibrium for in-situ temperature and salinity, during a ~4 weeks Lagrangian experiment. During N-loss, the product (N2) is depleted in 15N because of kinetic isotope fractionation. While biogenic N2 only reached up to ~10 µmol/kg, the ?15N-N2 anomalies were relatively low (down to ~-0.4‰). The ?15N-N2 anomalies are low compared to values always >-0.1‰) for equivalent biogenic N2 in the OMZ of the eastern tropical South Pacific. We will discuss the implication of these results for the global oceanic N budget.

  3. Solution 1H, 15N NMR spectroscopic characterization of substrate-bound, cyanide-inhibited human heme oxygenase: water occupation of the distal cavity.

    PubMed

    Li, Yiming; Syvitski, Ray T; Auclair, Karine; Ortiz de Montellano, Paul; La Mar, Gerd N

    2003-11-01

    A solution NMR spectroscopic study of the cyanide-inhibited, substrate-bound complex of uniformly (15)N-labeled human heme oxygenase, hHO, has led to characterization of the active site with respect to the nature and identity of strong hydrogen bonds and the occupation of ordered water molecules within both the hydrogen bonding network and an aromatic cluster on the distal side. [(1)H-(15)N]-HSQC spectra confirm the functionalities of several key donors in particularly robust H-bonds, and [(1)H-(15)N]HSQC-NOESY spectra lead to the identification of three additional robust H-bonds, as well as the detection of two more relatively strong H-bonds whose identities could not be established. The 3D NMR experiments provided only a modest, but important, extension of assignments because of the loss of key TOCSY cross-peaks due to the line broadening from a dynamic heterogeneity in the active site. Steady-state NOEs upon saturating the water signal locate nine ordered water molecules in the immediate vicinity of the H-bond donors, six of which are readily identified in the crystal structure. The additional three are positioned in available spaces to account for the observed NOEs. (15)N-filtered steady-state NOEs upon saturating the water resonances and (15)N-filtered NOESY spectra demonstrate significant negative NOEs between water molecules and the protons of five aromatic rings. Many of the NOEs can be rationalized by water molecules located in the crystal structure, but strong water NOEs, particularly to the rings of Phe47 and Trp96, demand the presence of at least an additional two immobilized water molecules near these rings. The H-bond network appears to function to order water molecules to provide stabilization for the hydroperoxy intermediate and to serve as a conduit to the active site for the nine protons required per HO turnover. PMID:14583035

  4. Retrieving nitrogen isotopic signatures from fresh leaf reflectance spectra: disentangling ?15N from biochemical and structural leaf properties

    PubMed Central

    Hellmann, Christine; Große-Stoltenberg, André; Lauströ, Verena; Oldeland, Jens; Werner, Christiane

    2015-01-01

    Linking remote sensing methodology to stable isotope ecology provides a promising approach to study ecological processes from small to large spatial scales. Here, we show that ?15N can be detected in fresh leaf reflectance spectra of field samples along a spatial gradient of increasing nitrogen input from an N2-fixing invasive species. However, in field data it is unclear whether ?15N directly influences leaf reflectance spectra or if the relationship is based on covariation between ?15N and foliar nitrogen content or other leaf properties. Using a 15N-labeling approach, we experimentally varied ?15N independently of any other leaf properties in three plant species across different leaf developmental and physiological states. ?15N could successfully be modeled by means of partial least squares (PLSs) regressions, using leaf reflectance spectra as predictor variables. PLS models explained 53–73% of the variation in ?15N within species. Several wavelength regions important for predicting ?15N were consistent across species and could furthermore be related to known absorption features of N-containing molecular bonds. By eliminating covariation with other leaf properties as an explanation for the relationship between reflectance and ?15N, our results demonstrate that 15N itself has an inherent effect on leaf reflectance spectra. Thus, our study substantiates the use of spectroscopic measurements to retrieve isotopic signatures for ecological studies and encourages future development. Furthermore, our results highlight the great potential of optical measurements for up-scaling isotope ecology to larger spatial scales. PMID:25983740

  5. Seasonal variation in species composition and abundance of demersal fish and invertebrates in a Seagrass Natural Reserve on the eastern coast of the Shandong Peninsula, China

    NASA Astrophysics Data System (ADS)

    Xu, Qiang; Guo, Dong; Zhang, Peidong; Zhang, Xiumei; Li, Wentao; Wu, Zhongxin

    2015-09-01

    Seagrass habitats are structurally complex ecosystems, which support high productivity and biodiversity. In temperate systems the density of seagrass may change seasonally, and this may influence the associated fish and invertebrate community. Little is known about the role of seagrass beds as possible nursery areas for fish and invertebrates in China. To study the functioning of a seagrass habitat in northern China, demersal fish and invertebrates were collected monthly using traps, from February 2009 to January 2010. The density, leaf length and biomass of the dominant seagrass Zostera marina and water temperature were also measured. The study was conducted in a Seagrass Natural Reserve (SNR) on the eastern coast of the Shandong Peninsula, China. A total of 22 fish species and five invertebrate species were recorded over the year. The dominant fish species were Synechogobius ommaturus, Sebastes schlegelii, Pholis fangi, Pagrus major and Hexagrammos otakii and these species accounted for 87% of the total number of fish. The dominant invertebrate species were Charybdis japonica and Octopus variabilis and these accounted for 98% of the total abundance of invertebrates. There was high temporal variation in species composition and abundance. The peak number of fish species occurred in August-October 2009, while the number of individual fish and biomass was highest during November 2009. Invertebrate numbers and biomass was highest in March, April, July and September 2009. Temporal changes in species abundance of fishes and invertebrates corresponded with changes in the shoot density and leaf length of the seagrass, Zostera marina.

  6. Variations of ?(15)N-Values and Hydrolyzable Amino Acids in Settling Particles in the Ocean.

    PubMed

    Schäfer, P; Ittekkot, V; Gravenhorst, G; Langel, R; Reineking, A

    1997-07-01

    Abstract The modification of nitrogen isotopic signals during particle sedimentation in the sea is of great interest for the use of sedimentary ?(15)N-values as a paleoceanographic tool. The effect of organic matter degradation on such modification was studied by analyzing nitrogen, hydrolyzable amino acids (THAA) and ?(15)N-values in a suit of marine settling particles collected from the Bay of Bengal, Indian Ocean, by using time-series sediment traps, and in underlying sediments. The flux of settling particles showed temporal variations which are related to the monsoons, the major climatic feature of this marine region. During high flux periods settling particles are enriched in nitrogenous material that is less degraded and exhibit higher ?(15)N-values than particles showing characteristics of degradation. At the sediment surface more than 95% of the settling particulate nitrogen is lost and the ?(15)N-values of the residual sedimentary nitrogen are higher than those of settling particles. The observed increase is interpreted to be due to fractionation during degradation of organic matter. PMID:22087496

  7. The use of delta(15)N in assessing sewage stress on coral reefs.

    PubMed

    Risk, Michael J; Lapointe, Brian E; Sherwood, Owen A; Bedford, Bradley J

    2009-06-01

    While coral reefs decline, scientists argue, and effective strategies to manage land-based pollution lag behind the extent of the problem. There is need for objective, cost-effective, assessment methods. The measurement of stable nitrogen isotope ratios, delta(15)N, in tissues of reef organisms shows promise as an indicator of sewage stress. The choice of target organism will depend upon study purpose, availability, and other considerations such as conservation. Algae are usually plentiful and have been shown faithfully to track sewage input. The organic matrix of bivalve shells can provide time series spanning, perhaps, decades. Gorgonians have been shown to track sewage, and can provide records potentially centuries-long. In areas where baseline data are lacking, which is almost everywhere, delta(15)N in gorgonians can provide information on status and trends. In coral tissue, delta(15)N combined with insoluble residue determination can provide information on both sewage and sediment stress in areas lacking baseline data. In the developed world, delta(15)N provides objective assessment in a field complicated by conflicting opinions. Sample handling and processing are simple and analysis costs are low. This is a method deserving widespread application. PMID:19286230

  8. The Predischarge Chromophore in Bacteriorhodopsin: A 15 N Solid-State NMR

    E-print Network

    Griffin, Robert G.

    The Predischarge Chromophore in Bacteriorhodopsin: A 15 N Solid-State NMR Study of the L with respect to the mechanism of light-driven proton transport because it selectively releases the Schiff base (SB) proton to the extracellular proton channel in the LfM transition. Here we extend our solid- state

  9. Synthesis and structural investigations of La 13Si 18Al 12O 15N 39

    NASA Astrophysics Data System (ADS)

    Esmaeilzadeh, Saeid; Schnick, Wolfgang

    2003-03-01

    A high temperature synthesis procedure using a radiofrequency (RF) furnace has been applied for preparation of the lanthanum containing sialon La 13Si 18Al 12O 15N 39. Single crystals of La 13Si 18Al 12O 15N 39 were obtained by reacting a mixture of Si 3N 4, SiO 2, AlN and La metal. Single-crystal X-ray diffraction analysis of La 13Si 18Al 12O 15N 39 revealed a cubic crystal structure with a unit cell parameter a=13.495(4) Å and the space group I 4¯3m . Thus La 13Si 18Al 12O 15N 39 is isostructural with Sr 3Ln 10Si 18Al 12O 18N 36 (Ln=Ce, Pr and Nd), with the significant difference of La occupying not only the crystallographic rare earth metal sites, but also the strontium sites found in Sr 3Ln 10Si 18Al 12O 18N 36 (Ln=Ce, Pr, Nd).

  10. [Use of the stable nitrogen isotope 15N in assessing liver metabolism in hormonal contraception].

    PubMed

    Metzner, C; Jung, K; Laue, R; Wagenknecht, C; Graubaum, H J; Kranz, D; Seifert, P

    1990-01-01

    In 37 women with long-term use of oral contraceptives (average use 13.4 years) and 12 women who had not taken oral contraceptives for at least 5 years we determined the serum enzymes ALAT, ASAT, Gamma-GT and conducted the 15N-ammonium test as a marker of partial metabolic performance of the liver. In addition we studied total protein, protein fractions in the serum and haematologic parameter. 18 out of 37 women showed a morbid result in the 15N-ammonium test. In 4 of these 18 women morphological changes representing hepatic damage caused by contraceptives could be detected. On the average ALAT, Gamma-GT and 15N-ammonium test in both groups are clearly different. Because the enzymic levels are being in the normal range, only the 15N ammonium test enables to give a hepatotoxic evidence. It is possible to conclude that long-term use of oral contraceptives influences the liver metabolism. PMID:2314186

  11. Structural insights from 15N relaxation data for an anisotropic collagen peptide

    E-print Network

    Lawson, Catherine L.

    Structural insights from 15N relaxation data for an anisotropic collagen peptide Jianxi Xiao-bonding is thought to play an important role in defining collagen recognition sites or regions that contain disease causing collagen mutations. For collagen model peptides, structure determination by standard NMR

  12. Nitrate Removal in Two Relict Oxbow Urban Wetlands: A 15N Mass-balance Approach

    EPA Science Inventory

    A 15N-tracer method was used to quantify nitrogen (N) removal processes in two relict oxbow wetlands located adjacent to the Minebank Run restored stream reach in Baltimore County (Maryland, USA) during summer 2009 and early spring 2010. A mass-balance approach was used to determ...

  13. 15N Uptake from Manure and Fertilizer Sousrces by Three Consecutive Crops Under Controlled Conditions.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The North Central “La Comarca Lagunera” region (25° 31’ N, 103° 14’ W), is one of the most important dairy production areas of Mexico. We conducted the first isotopic nitrogen (15N) labeled manure study in Mexico to assess the potential to supply nitrogen (N) to three consecutive forage crops with a...

  14. Direct Use of 15 N Relaxation Rates as Experimental Restraints on Molecular

    E-print Network

    Clore, G. Marius

    Direct Use of 15 N Relaxation Rates as Experimental Restraints on Molecular Shape and Orientation interproton distance restraints that are the mainstay of conventional NMR structure determination.1 While restraints derived from chemical shift perturbation mapping can facilitate protein docking,3

  15. Using macroalgal ?15N bioassay to detect cruise ship waste water effluent inputs in Skagway, AK

    EPA Science Inventory

    Nitrogen stable isotopes are a powerful tool for tracking sources of N to marine ecosystems. I used green macroalgae as a bioassay organism to evaluate if the ?15N signature of cruise ship waste water effluent (CSWWE) could be detected in Skagway Harbor, AK. Opportunistic green...

  16. Using a Macroalgal ?15N Bioassay to Detect Cruise Ship Waste Water Effluent Inputs

    EPA Science Inventory

    Nitrogen stable isotopes are a powerful tool for tracking sources of N to marine ecosystems. I used green macroalgae as a bioassay organism to evaluate if the ?15N signature of cruise ship waste water effluent (CSWWE) could be detected in Skagway Harbor, AK. Opportunistic green...

  17. Tracing Nitrogen through Landscapes to Coastal Wetlands using d15N of Larval Fish

    EPA Science Inventory

    Our objective was to evaluate the use of the nitrogen stable isotope value (d15N) of larval fish as an indicator of incipient anthropogenic nitrogen loading to coastal wetlands in the Great Lakes. We sampled coastal wetlands in five Lake Superior south shore tributaries that had ...

  18. [Dynamics of amino acid and protein metabolism of laying hens after the administration of 15N-labeled wheat protein. 3. Incorporation of 15N into egg shell, egg white and egg yolk].

    PubMed

    Gruhn, K; Kirchner, E

    1987-01-01

    12 colostomized laying hybrids received a ration meeting their requirement of 15N labelled wheat with a 15N excess (15N') of 14.37 atom-% over 4 days. The 15N' of the total ration amounted to 4.47 atom-%. Each hen consumed 135 mg 15N' per day. On another 4 days the same rations with non labelled wheat were fed. The 12 hens laid 56 eggs during the 8 days of the experiment. They were divided into egg shell, white and yolk of egg. In addition, the protein of the white and yolk of egg was precipitated with trichloric acetic acid (TCA) and the nitrogen in these fractions was determined. On average of the 56 eggs, the N quota in the egg shell was 5.3%, in the white of egg 49.1% and in the yolk 45.6%. The atom-% 15N' in the shells of the eggs laid on the first day of the experiment was on average 0.21, whereas only 0.03 and 0.02 atom-% 15N' resp. could be detected in the white and yolks of the eggs. On the first day after the last 15N application the atom-% 15N' in the egg shell and the white of egg was highest and amounted to 2.33 and 2.43 atom-% resp. The highest value of 1.83 atom-% 15N' in the yolk was ascertained 3 days after the last 15N intake. The mean quota of TCA-precipitable N in the white of egg is 97.6% and in the yolk 94.4% of the respective total N. The atom-% 15N' in the non-protein N-compounds was higher than in the protein fractions. PMID:3689145

  19. Determining Degradation and Synthesis Rates of Arabidopsis Proteins Using the Kinetics of Progressive 15N Labeling of Two-dimensional Gel-separated Protein Spots*

    PubMed Central

    Li, Lei; Nelson, Clark J.; Solheim, Cory; Whelan, James; Millar, A. Harvey

    2012-01-01

    The growth and development of plant tissues is associated with an ordered succession of cellular processes that are reflected in the appearance and disappearance of proteins. The control of the kinetics of protein turnover is central to how plants can rapidly and specifically alter protein abundance and thus molecular function in response to environmental or developmental cues. However, the processes of turnover are largely hidden during periods of apparent steady-state protein abundance, and even when proteins accumulate it is unclear whether enhanced synthesis or decreased degradation is responsible. We have used a 15N labeling strategy with inorganic nitrogen sources coupled to a two-dimensional fluorescence difference gel electrophoresis and mass spectrometry analysis of two-dimensional IEF/SDS-PAGE gel spots to define the rate of protein synthesis (KS) and degradation (KD) of Arabidopsis cell culture proteins. Through analysis of MALDI-TOF/TOF mass spectra from 120 protein spots, we were able to quantify KS and KD for 84 proteins across six functional groups and observe over 65-fold variation in protein degradation rates. KS and KD correlate with functional roles of the proteins in the cell and the time in the cell culture cycle. This approach is based on progressive 15N labeling that is innocuous for the plant cells and, because it can be used to target analysis of proteins through the use of specific gel spots, it has broad applicability. PMID:22215636

  20. Carbon-rich presolar grains from massive stars. Subsolar 12C/13C and 14N/15N ratios and the mystery of 15N

    E-print Network

    Pignatari, M; Hoppe, P; Jordan, C J; Gibson, B K; Trappitsch, R; Herwig, F; Fryer, C; Hirschi, R; Timmes, F X

    2015-01-01

    Carbon-rich grains with isotopic anomalies compared to the Sun are found in primitive meteorites. They were made by stars, and carry the original stellar nucleosynthesis signature. Silicon carbide grains of Type X and C, and low-density graphites condensed in the ejecta of core-collapse supernovae. We present a new set of models for the explosive He shell and compare them with the grains showing 12C/13C and 14N/15N ratios lower than solar. In the stellar progenitor H was ingested into the He shell and not fully destroyed before the explosion. Different explosion energies and H concentrations are considered. If the SN shock hits the He-shell region with some H still present, the models can reproduce the C and N isotopic signatures in C-rich grains. Hot-CNO cycle isotopic signatures are obtained, including a large production of 13C and 15N. The short-lived radionuclides 22Na and 26Al are increased by orders of magnitude. The production of radiogenic 22Ne from the decay of 22Na in the He shell might solve the pu...

  1. Do Low 15N Values in Paleozoic Epeiric Basins Indicate High Rates of N Fixation?

    NASA Astrophysics Data System (ADS)

    Tuite, M. L.; Macko, S. A.

    2011-12-01

    As a consequence of the high energetic requirements of dinitrogen (N2) fixation, organic N produced by diazotrophic microorganisms typically exhibits ?15N values similar to atmospheric N2 (approximately 0%). Because the ?15N of organic-rich Paleozoic epeiric basin sediments often has values in the vicinity of 0%, it is frequently asserted that N2 fixation was the primary source of new reactive N for productivity. There are two broad reasons why recourse to widespread and intensive N fixation as the primary source of the organic N is problematic. First, there are substantial physiological and ecological constraints on marine N fixation that limit its extent in modern oceans primarily to open ocean basins. Second, preservation of an unaltered isotopic signature of diazotrophy in underlying sediments is not a likely outcome of oxic and anoxic diagenetic alteration and repeated cycles of mineralization and assimilation. Constraining the sources of reactive N for primary productivity is critical to understanding the N cycle in Paleozoic epeiric seas. In this study we report ?15N values from high organic matter Middle Ordovician through Late Devonian dysoxic and euxinic basinal sediments. We propose a nitrogen isotope mass balance model that incorporates the microbial ecology of a stratified water column and the biochemical stoichiometry of primary production and organic matter diagenesis. Results from the model support our contention that high rates of N fixation over extended time periods were not the cause of depleted nitrogen isotope values in organic-rich Paleozoic basinal sediments. Rather, the depleted values were a consequence of a diminished role for nitrification and subsequent N loss via denitrification and anammox, and the preferential preservation of a substantially 15N-depleted chlorophyll-influenced lipid fraction. The model may be applicable to earlier and later geological periods where high organic matter sediments feature depleted ?15N values.

  2. Thousand Year Archives of the Bulk and Compound-Specific ?15N of Export Production From the North Pacific Subtropical Gyre Indicate Increasing Nitrogen Fixation Over the Past 150 Years

    NASA Astrophysics Data System (ADS)

    Sherwood, O.; Batista, F. C.; Brown, J. T.; Guilderson, T. P.; McCarthy, M.

    2012-12-01

    Stable nitrogen isotopic analysis of amino acids (?15N-AA) preserved in proteins has emerged as a powerful new tool to explore trophic levels and nutrient cycling in nature. To date, little has been done to explore ?15N-AA in paleo-studies of the marine nitrogen cycle. We analysed the bulk and AA-specific ?15N in the long-lived, deep-sea, proteinaceous coral Gerardia. By feeding on sinking particulate organic matter, proteinaceous corals integrate the biogeochemical signature of recently exported production within discrete skeletal growth layers. Sub-decadal resolution time-series records spanning the time period 1000 AD to present were generated from specimens of Gerardia collected from the main Hawaiian Islands, Cross Seamount, and French Frigate Shoals in the North Pacific Subtropical Gyre (NPSG). Records of bulk ?15N from the three different locations, geographically separated by up to 1000 km, showed remarkably similar long term trends. Bulk ?15N remained relatively stable from ~1000-1850 years AD, and then decreased by a total of 2 ‰ from ~1850 AD to the present. The ?15N-AA of the "trophic" group of amino acids indicated no significant changes in trophic level or microbial re-synthesis of export production over this time period. The ?15N of "source" amino acids was significantly correlated with corresponding values of bulk ?15N, with the ?15N of phenylalanine decreasing from 4.2 to 2.1‰. The latter value is similar to recent measurements of subsurface nitrate ?15N near Hawaii, suggesting that the ?15N of phenylalanine may be used to quantitatively track changes in the isotopic signature of nitrate at the base of the food web. Using a simple isotopic mass balance between upwelled nitrate and nitrogen fixation we calculate a 30% increase in nitrogen fixation in the NPSG since ~1850. These results provide invaluable long-term context for recent observations, and highlight profound changes in the marine biogeochemical cycling of nitrogen over the past 150 years in this climatically-sensitive area of the world ocean.

  3. Constraints on abundance, composition, and nature of X-ray amorphous components of soils and rocks at Gale crater, Mars

    NASA Astrophysics Data System (ADS)

    Dehouck, Erwin; McLennan, Scott M.; Meslin, Pierre-Yves; Cousin, Agnès.

    2014-12-01

    X-ray diffraction patterns of the three samples analyzed by Curiosity's Chemistry and Mineralogy (CheMin) instrument during the first year of the Mars Science Laboratory mission—the Rocknest sand, and the John Klein and Cumberland drill fines, both extracted from the Sheepbed mudstone—show evidence for a significant amorphous component of unclear origin. We developed a mass balance calculation program that determines the range of possible chemical compositions of the crystalline and amorphous components of these samples within the uncertainties of mineral abundances derived from CheMin data. In turn, the chemistry constrains the minimum abundance of amorphous component required to have realistic compositions (all oxides ? 0 wt %): 21-22 wt % for Rocknest and 15-20 wt % for Cumberland, in good agreement with estimates derived from the diffraction patterns (~27 and ~31 wt %, respectively). Despite obvious differences between the Rocknest sand and the Sheepbed mudstone, the amorphous components of the two sites are chemically very similar, having comparable concentrations of SiO2, TiO2, Al2O3, Cr2O3, FeOT, CaO, Na2O, K2O, and P2O5. MgO tends to be lower in Rocknest, although it may also be comparable between the two samples depending on the exact composition of the smectite in Sheepbed. The only unambiguous difference is the SO3 content, which is always higher in Rocknest. The observed similarity suggests that the two amorphous components share a common origin or formation process. The individual phases possibly present within the amorphous components include: volcanic (or impact) glass, hisingerite (or silica + ferrihydrite), amorphous sulfates (or adsorbed SO42-), and nanophase ferric oxides.

  4. Determination of Natural 14C Abundances in Dissolved Organic Carbon in Organic-Rich Marine Sediment Porewaters by Thermal Sulfate Reduction

    NASA Astrophysics Data System (ADS)

    Johnson, L.; Komada, T.

    2010-12-01

    The abundances of natural 14C in dissolved organic carbon (DOC) in the marine environment hold clues regarding the processes that influence the biogeochemical cycling of this large carbon reservoir. At present, UV irradiation is the widely accepted method for oxidizing seawater DOC for determination of their 14C abundances. This technique yields precise and accurate values with low blanks, but it requires a dedicated vacuum line, and hence can be difficult to implement. As an alternative technique that can be conducted on a standard preparatory vacuum line, we modified and tested a thermal sulfate reduction method that was previously developed to determine ?13C values of marine DOC (Fry B. et al., 1996. Analysis of marine DOC using a dry combustion method. Mar. Chem., 54: 191-201.) to determine the 14C abundances of DOC in marine sediment porewaters. In this method, the sample is dried in a 100 ml round-bottom Pyrex flask in the presence of excess oxidant (K2SO4) and acid (H3PO4), and combusted at 550 deg.C. The combustion products are cryogenically processed to collect and quantify CO2 using standard procedures. Materials we have oxidized to date range from 6-24 ml in volume, and 95-1500 ?gC in size. The oxidation efficiency of this method was tested by processing known amounts of reagent-grade dextrose and sucrose (as examples of labile organic matter), tannic acid and humic acid (as examples of complex natural organic matter), and porewater DOC extracted from organic-rich nearshore sediments. The carbon yields for all of these materials averaged 99±4% (n=18). The 14C abundances of standard materials IAEA C-6 and IAEA C-5 processed by this method using >1mgC aliquots were within error of certified values. The size and the isotopic value of the blank were determined by a standard dilution technique using IAEA C-6 and IAEA C-5 that ranged in size from 150 to 1500 ?gC (n=4 and 2, respectively). This yielded a blank size of 6.7±0.7 ?gC, and a blank isotopic value of 0.54±0.05 fMC. The size of the blank agreed well with that determined directly by processing variable volumes of UV-irradiated deionized water (5.6±0.7 ?gC, n=9). The size of the blank amounts to <~5% of the size of porewater DOC samples that are typically recovered from organic-rich sediment cores (~100-500 ?gC). The fMC value of the blank suggests that there may be multiple sources of extraneous carbon that range in 14C abundance. In order to assess the fidelity of 14C abundances in natural porewater DOC oxidized by thermal sulfate reduction, we oxidized porewater DOC samples collected from the central floor of the Santa Monica Basin, California Borderland, using both this method and UV irradiation (the latter carried out at the Druffel laboratory, University of California Irvine). The fMC values obtained by the two methods agreed within error. Carbon yields from the two methods also agreed closely. These findings show that thermal sulfate reduction may be a promising method to oxidize small, concentrated marine DOC samples for 14C analysis.

  5. Isotopic variability of cave bears (?15N, ?13C) across Europe during MIS 3

    NASA Astrophysics Data System (ADS)

    Krajcarz, Magdalena; Pacher, Martina; Krajcarz, Maciej T.; Laughlan, Lana; Rabeder, Gernot; Sabol, Martin; Wojtal, Piotr; Bocherens, Hervé

    2016-01-01

    Collagen, the organic fraction of bone, records the isotopic parameters of consumed food for carbon (?13C) and nitrogen (?15N). This relationship of isotopic signature between diet and tissue is an important tool for the study of dietary preferences of modern and fossil animal species. Since the first information on the isotopic signature of cave bear was reported, numerous data from Europe have become available. The goal of this work is to track the geographical variation of cave bear collagen isotopic values in Europe during Marine Isotopic Stage 3 (about 60,000-25,000 yr BP). In this study the results of new ?13C and ?15N isotopic analyses of cave bear collagen from four Central-Eastern European sites are presented, as well as a review of all published isotopic data for cave bears of the same period. The main conclusion is a lack of geographical East-West pattern in the variations of ?13C and ?15N values of cave bear collagen. Moreover, no relationship was found between cave bear taxonomy and isotopic composition. The cave bears from Central-Eastern Europe exhibit ?13C and ?15N values near the average of the range of Central, Western and Southern European cave bears. Despite the fact that most cave bear sites follow an altitudinal gradient, separate groups of sites exhibit shift in absolute values of ?13C, what disturbs an altitude-related isotopic pattern. The most distinct groups are: high Alpine sites situated over 1500 m a.s.l. - in terms of ?13C; and two Romanian sites Pe?tera cu Oase and Ur?ilor - in case of ?15N. Although the cave bear isotopic signature is driven by altitude, the altitudinal adjustment of isotopic data is not enough to explain the isotopic dissimilarity of these cave bears. The unusually high ?15N signature of mentioned Romanian sites is an isolated case in Europe. Cave bears from relatively closely situated Central-Eastern European sites and other Romanian sites are more similar to Western European than to Romanian populations in terms of isotopic composition, and probably ecology.

  6. Biomarkers: d13C and d15N Distribution Tightly Coupled to Nutrient Dynamics and Viral Lysing in a Microbial Mat From Death Valley, California

    NASA Astrophysics Data System (ADS)

    Hewson, I.; Archer, R.; Mahaffey, C.; Scott, J.; Tsapin, A.

    2002-12-01

    Extrapolations into ancient biomes make many assumptions and inferences regarding life modes and environmental habitat. While definition of a stromatolite as an extinct microbial biome by petrographic analysis is promising, Life interacts with is environment, actively manipulating energy flow across chemical disequilibria gradients, harvesting energy crucial for physiological maintenance and reproduction. Such structuring of communities in turn, leaves specific chemical/isotopic imprints related to physiological processes of prokaryotic communities specific to each oxidation/redox horizon. We examine stable isotopic d13C signals (d13C and d15N) as potential biomarkers reflecting bacterial physiology and microbial community nutrient-energy dynamics. While isotopes may reveal ancient chemical structuring of microbial mats, we also turn to invoking viral lysing of bacterial hosts in nutrient cycling within modern extreme environments as well as ancient stromatic structures of early Earth. Our records of d13C indicate extreme enrichment(-12%) for Corg in our extant mat due to CO2 limitation across a hypersaline diffusive barrier at the mat's surface. d15N is lowest at the mat's surface (indicating N2- fixation) where nitrogen- fixing cyanobacteria Microcoleus sp. are present . Viruses are extremely abundant in the microbial mat, exceeding bacterial abundances by a factor of ten. The ratio of viruses to bacteria was very high (VBR = 39 ñ 10) compared with abundances in marine sediments. Distribution of viruses closely follows distribution of bacteria, suggesting bacteria as primary hosts. The ratio of viruses to bacteria is inversely correlated to the concentration of organic C suggesting virus abundance is responsive to host substrate availability. High ratios of viruses to bacteria in mid-mat horizons (2.5 - 3.7 cm) above increasing levels of d13C in deeper horizons, coupled with a lack of increase in bacteria, suggests that viral lysis contributes to significant downward organic C (polysaccaride exudates) transport within the mat. Subsequent accumulation of d13C as well as heavier d15N in deeper sediment(denitrification)horizons elucidates tight nutrient coupling between evaporite substrate, nitrogen fixing primary producers and downcore zones of active denitrification and sulphate reduction. Discrepencies between d13C of ancient stromatolites (in line with C-3 photosynthetic pathways) and modern analogues (Badwater, CA) suggest a migration of microbial mats towards more extreme environments through time. A methodology for isotopically testing environmental and physiological responses in the geological record is presented here.

  7. **1**5N-NMR INVESTIGATION OF HYDROXYLAMINE DERIVATIZED HUMIC SUBSTANCES.

    USGS Publications Warehouse

    Thorn, Kevin A.; Arterburn, Jeffrey B.; Mikita, Michael A.

    1986-01-01

    Humic substances are the most abundant naturally occurring refactory organic compounds in soils and water. They have a broad range of physical, chemical and physiological properties. In soils, humic substances contribute to the cation exchange capacity, help maintain the physical structure, and play a role in plant growth and nutrition. In aquatic systems, humic substances serve to regulate the levels of inorganic constituents, yield trihalomethanes upon chlorination, and transport or concentrate organic and inorganic pollutants. The oxygen containing functional groups of humic and fulvic acids are believed to play a key role in the chemical properties of humic substances. This study was undertaken to gain additional information on the specific types of oxygen functionalities in humic substances. Since the analysis of hydroxyl moieties had been earlier established, we focused our attention on the analysis of ketone and aldehyde functional groups in humic substances.

  8. MUSIC and Aromatic Residues: Amino Acid Type-Selective 1H- 15N Correlations, III

    NASA Astrophysics Data System (ADS)

    Schubert, Mario; Oschkinat, Hartmut; Schmieder, Peter

    2001-12-01

    Amino acid type-selective experiments can help to remove ambiguities in automated assignment procedures for 15N/13C-labeled proteins. Here we present five triple-resonance experiments that yield amino acid type-selective 1H-15N correlations for aromatic amino acids. Four of the novel experiments are based on the MUSIC coherence transfer scheme that replaces the initial INEPT transfer and is selective for CH2. The MUSIC sequence is combined with selective excitation pulses to create experiments for Trp (W-HSQC) as well as Phe, Tyr, and His (FYH-HSQC). In addition, an experiment selective for Trp H?1-N?1 is presented. The new experiments are recorded as two-dimensional experiments and their performance is demonstrated with the application to a protein domain of 115 amino acids.

  9. MUSIC and aromatic residues: amino acid type-selective (1)H-(15)N correlations, III.

    PubMed

    Schubert, M; Oschkinat, H; Schmieder, P

    2001-12-01

    Amino acid type-selective experiments can help to remove ambiguities in automated assignment procedures for (15)N/(13)C-labeled proteins. Here we present five triple-resonance experiments that yield amino acid type-selective (1)H-(15)N correlations for aromatic amino acids. Four of the novel experiments are based on the MUSIC coherence transfer scheme that replaces the initial INEPT transfer and is selective for CH(2). The MUSIC sequence is combined with selective excitation pulses to create experiments for Trp (W-HSQC) as well as Phe, Tyr, and His (FYH-HSQC). In addition, an experiment selective for Trp H(epsilon1)-N(epsilon1) is presented. The new experiments are recorded as two-dimensional experiments and their performance is demonstrated with the application to a protein domain of 115 amino acids. PMID:11740893

  10. Determination of the ?15N of total nitrogen in solids; RSIL lab code 2893

    USGS Publications Warehouse

    Revesz, Kinga; Qi, Haiping; Coplen, Tyler B.

    2006-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2893 is to determine the ?(15N/14N), abbreviated as ?15N , of total nitrogen in solid samples. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total nitrogen in a solid sample into N2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines relative difference in the isotope-amount ratios of stable nitrogen isotopes (15N/14N)of the product N2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in a tin capsule and loaded into the Costech Zero Blank Autosampler of the EA. Under computer control, samples are dropped into a heated reaction tube that contains an oxidant, where the combustion takes place in a helium atmosphere containing an excess of oxygen gas. Combustion products are transported by a helium carrier through a reduction tube to remove excess oxygen and convert all nitrous oxides into N2 and through a drying tube to remove water. The gas-phase products, mainly CO2 and N2, are separated by a gas chromatograph. The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Finnigan MAT (now Thermo Scientific) ConFlo II interface, which also is used to inject N2 reference gas and helium for sample dilution. The IRMS is a Thermo Scientific Delta V Plus CF-IRMS. It has a universal triple collector, two wide cups with a narrow cup in the middle, capable of measuring mass/charge (m/z) 28, 29, 30, simultaneously. The ion beams from N2 are as follows: m/z 28 = N2 = 14N14N; m/z 29 = N2 = 14N15N primarily; m/z 30 = NO = 14N16O primarily, which is a sign of contamination or incomplete reduction.

  11. Food webs of two intermittently open estuaries receiving 15N-enriched sewage effluent

    NASA Astrophysics Data System (ADS)

    Hadwen, Wade L.; Arthington, Angela H.

    2007-01-01

    Carbon and nitrogen stable isotope signatures were used to assess the response of food webs to sewage effluent discharged into two small intermittently open estuaries in northern New South Wales, Australia. One of these systems, Tallows Creek, has a history of direct sewage inputs, whilst the other, Belongil Creek, receives wastewater via an extensive wetland treatment system. The food webs of both systems were driven by algal sources of carbon, reflecting high autotrophic productivity in response to the nutrients entering the system from sewage effluent. All aquatic biota collected from Tallows Creek had significantly enriched ?15N signatures relative to their conspecifics from Belongil Creek, indicating that sewage nitrogen had been assimilated and transferred throughout the Tallows Creek food web. These ?15N values were higher than those reported from studies in permanently open estuaries receiving sewage effluent. We suggest that these enriched signatures and the transfer of nitrogen throughout the entire food web reflect differences in hydrology and associated nitrogen cycling processes between permanently open and intermittently open estuaries. Although all organisms in Tallows Creek were generally 15N-enriched, isotopically light (less 15N-enriched) individuals of estuary perchlet ( Ambassis marianus) and sea mullet ( Mugil cephalus) were also collected. These individuals were most likely recent immigrants into Tallows Creek, as this system had only recently been opened to the ocean. This isotopic discrimination between resident (enriched) and immigrant (significantly less enriched) individuals can provide information on fish movement patterns and the role of heavily polluted intermittently open estuaries in supporting commercially and recreationally valuable estuarine species.

  12. Community 15N isoscapes to resolve plant-plant-interactions at the spatial scale

    NASA Astrophysics Data System (ADS)

    Hellmann, Christine; Rascher, Katherine G.; Máguas, Cristina; Werner, Christiane

    2014-05-01

    Isoscapes have greatly improved our ability to understand biogeochemical processes on continental to global scales. However, the isoscapes framework may also have significant potential to resolve the spatial component of within-community interactions. For example, exotic plant invaders often exert strong impacts on ecosystem functioning, particularly regarding water-, carbon- and nutrient-cycles, but the spatial extent of such alterations is largely unknown. Here we show that massive N input by the N2-fixing exotic invasive Acacia longifolia to a Portuguese dune system can be traced using spatially resolved information on native plants' leaf ?15N. We found isotopic signatures of N to differ strongly between the native system (?15N c. -10 o) and the atmospherically derived N in A. longifolia phyllodes (?15N c. 0 o). Thus, sources of N for native plants could be readily distinguished. Leaf ?15N of a native, non-fixing species was increasingly enriched the closer the plant grew to the invader, indicating uptake of fixed N provided by A. longifolia. The enrichment was evident far beyond the stands of the invader, demonstrating that A. longifolia affected N budgets of native species up to a distance of 8 m exceeding the margin of the canopy. Furthermore, using the isoscapes approach, we were able to quantify the total area of N enrichment and could thus show that the area affected by invasion was at least 3.5 times larger than the area actually occupied by the invader. However, a native N2-fixing species had no such effects. Thus, downscaling isoscapes to the community level opens new frontiers in quantifying the spatial dimension of functional changes associated with plant invasions. Moreover, considering the feasibility and applicability of this approach, it may provide a promising tool to identify, quantify and monitor different types of functional plant-plant interactions within communities at a spatially explicit scale.

  13. Individual protein balance strongly influences ?15N and ?13C 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 ?15N and ?13C 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 ?15N and ?13C values of the whole tilapia. The fish were fed the isoenergetic and isolipidic semi-synthetic diets at a relatively low level. ?15N and ?13C 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.

  14. Seasonal ?13C and ?15N isoscapes of fish populations along a continental shelf trophic gradient

    NASA Astrophysics Data System (ADS)

    Radabaugh, Kara R.; Hollander, David J.; Peebles, Ernst B.

    2013-10-01

    The West Florida Shelf, located in the eastern Gulf of Mexico, transitions from a eutrophic ecosystem dominated by the Mississippi River plume to mesotrophic and oligotrophic ecosystems off the coast of peninsular Florida. Three extensive trawl surveys in this region were used to acquire samples of fish muscle, benthic algae from sea urchin stomach contents, and filtered particulate organic matter (POM) to create ?13C and ?15N isoscapes. Muscle ?15N from three widely distributed fish species, Synodus foetens (inshore lizardfish), Calamus proridens (littlehead porgy), and Syacium papillosum (dusky flounder), exhibited strong longitudinal correlations (Pearson?s r=-0.67 to -0.90, p<0.001) that coincided with the principal trophic gradient, whereas ?13C values of fish muscle and benthic algae were correlated with depth (Pearson?s r=-0.34 to -0.73, p<0.05). Correlations between isotopic values and surface concentrations of chlorophyll and particulate organic carbon (POC) imply linkages between the isotopic baseline and transitions from eutrophic to oligotrophic waters. The ?13C depth gradient and the ?15N longitudinal gradient were consistent between seasons and years, providing a foundation for future stable isotope studies of animal migration in the Gulf of Mexico.

  15. Quantitative structure-property relationships in boron nitrides: the 15N- and 11B chemical shifts.

    PubMed

    Marian, C M; Gastreich, M

    2001-01-01

    Nuclear Magnetic Resonance (NMR) chemical shifts(delta) for elements in solids may often be approached by ab initio cluster calculations. We employ this technique to investigate the influence of structural alterations on the 15N and 11B chemical shifts in boron nitrides--in both hexagonal and cubic modifications. Within a given class of connectivity, i.e., three- or fourfold coordinated nitrogen, for the first time, an almost linear correlation between the 15N chemical shift and N-B bond lengths could be established. Also, the 11B shifts in hexagonal boron nitride correlate with the B-N bond distance; however, the effect is less pronounced. For the value of the chemical shift (CS), the decisive property is the average bond length at the atom in focus. Variations of CS are predominantly caused by changes in the paramagnetic deshielding. Further, second-nearest neighbor effects on the shieldings at 15N nuclei are quantified by subtraction schemes. The present work is closely related to the verification of models for amorphous high-demand Si/B/N ceramics. PMID:11407601

  16. Combining Denitrifying Bacteria and Laser Spectroscopy for Isotopic Analyses (?(15)N, ?(18)O) of Dissolved Nitrate.

    PubMed

    Soto, David X; Koehler, Geoff; Hobson, Keith A

    2015-07-21

    We present a novel approach for nitrogen (?(15)N) and oxygen (?(18)O) isotopic analysis of nitrate in water based on the isotopic analysis of N2O produced from the conversion of NO3(-) by cultured denitrifying bacteria and off-axis integrated cavity output spectroscopy (OA-ICOS). The headspace N2O was manually injected into an OA-ICOS isotopic N2O laser analyzer through a syringe septum port. Sample analysis time was ?300 s. The use of OA-ICOS technology yields accurate and precise ?(15)N and ?(18)O results for dissolved nitrate samples when nonlinearity issues are considered. This new isotope analytical technique thus improves the isotopic analysis of nitrates by (i) providing accurate measurements of ?(15)N and ?(18)O without preconcentration, (ii) eliminating interferences by other gas substances (i.e., H2O and CO2), and (iii) reducing extensive maintenance and costs of isotope ratio mass spectrometers (IRMS). This approach will greatly streamline the identification and quantification of nitrate sources in aquatic systems. PMID:26151723

  17. Impact of seaweed beachings on dynamics of ?(15)N isotopic signatures in marine macroalgae.

    PubMed

    Lemesle, Stéphanie; Mussio, Isabelle; Rusig, Anne-Marie; Menet-Nédélec, Florence; Claquin, Pascal

    2015-08-15

    A fine-scale survey of ?(15)N, ?(13)C, tissue-N in seaweeds was conducted using samples from 17 sampling points at two sites (Grandcamp-Maisy (GM), Courseulles/Mer (COU)) along the French coast of the English Channel in 2012 and 2013. Partial triadic analysis was performed on the parameter data sets and revealed the functioning of three areas: one estuary (EstA) and two rocky areas (GM(?), COU(?)). In contrast to oceanic and anthropogenic reference points similar temporal dynamics characterized ?(15)N signatures and N contents at GM(?) and COU(?). Nutrient dynamics were similar: the N-concentrations in seawater originated from the River Seine and local coastal rivers while P-concentrations mainly from these local rivers. ?(15)N at GM(?) were linked to turbidity suggesting inputs of autochthonous organic matter from large-scale summer seaweed beachings made up of a mixture of Rhodophyta, Phaeophyta and Chlorophyta species. This study highlights the coupling between seaweed beachings and nitrogen sources of intertidal macroalgae. PMID:26095988

  18. Denitrification in nitrate-rich streams: Application of N2:Ar and 15N-tracer methods in intact cores

    USGS Publications Warehouse

    Smith, L.K.; Voytek, M.A.; Böhlke, J.K.; Harvey, J.W.

    2006-01-01

    Rates of benthic denitrification were measured using two techniques, membrane inlet mass spectrometry (MIMS) and isotope ratio mass spectrometry (IRMS), applied to sediment cores from two NO3--rich streams draining agricultural land in the upper Mississippi River Basin. Denitrification was estimated simultaneously from measurements of N 2:Ar (MIMS) and 15N[N2] (IRMS) after the addition of low-level 15NO3- tracer ( 15N:N = 0.03-0.08) in stream water overlying intact sediment cores. Denitrification rates ranged from about 0 to 4400 lmol N??m -2??h-1 in Sugar Creek and from 0 to 1300 ??mol N??m-2??h-1 in Iroquois River, the latter of which possesses greater streamflow discharge and a more homogeneous streambed and water column. Within the uncertainties of the two techniques, there is good agreement between the MIMS and IRMS results, which indicates that the production of N2 by the coupled process of nitrification/denitrification was relatively unimportant and surface-water NO3- was the dominant source of NO3- for benthic denitrification in these streams. Variation in stream NO3- concentration (from about 20 ??mol/L during low discharge to 1000 ??mol/L during high discharge) was a significant control of benthic denitrification rates, judging from the more abundant MIMS data. The interpretation that NO3- concentration directly affects denitrification rate was corroborated by increased rates of denitrification in cores amended with NO 3-. Denitrification in Sugar Creek removed ???11% per day of the instream NO3- in late spring and removed roughly 15-20% in late summer. The fraction of NO3- removed in Iroquois River was less than that of Sugar Creek. Although benthic denitrification rates were relatively high during periods of high stream flow, when NO3 concentrations were also high, the increase in benthic denitrification could not compensate for the much larger increase in stream NO3- fluxes during high flow. Consequently, fractional NO3- losses were relatively low during high flow. ?? 2006 by the Ecological Society of America.

  19. Penguin tissue as a proxy for relative krill abundance in East Antarctica during the Holocene

    PubMed Central

    Huang, Tao; Sun, Liguang; Long, Nanye; Wang, Yuhong; Huang, Wen

    2013-01-01

    Antarctic krill (Euphausia superba) is a key component of the Southern Ocean food web. It supports a large number of upper trophic-level predators, and is also a major fishery resource. Understanding changes in krill abundance has long been a priority for research and conservation in the Southern Ocean. In this study, we performed stable isotope analyses on ancient Adélie penguin tissues and inferred relative krill abundance during the Holocene epoch from paleodiets of Adélie penguin (Pygoscelis adeliae), using inverse of ?15N (ratio of 15N/14N) value as a proxy. We find that variations in krill abundance during the Holocene are in accord with episodes of regional climate changes, showing greater krill abundance in cold periods. Moreover, the low ?15N values found in modern Adélie penguins indicate relatively high krill availability, which supports the hypothesis of krill surplus in modern ages due to recent hunt for krill-eating seals and whales by humans. PMID:24076768

  20. Macroalgae ?15N values in well-mixed estuaries: Indicator of anthropogenic nitrogen input or macroalgae metabolism?

    NASA Astrophysics Data System (ADS)

    Raimonet, Mélanie; Guillou, Gaël; Mornet, Françoise; Richard, Pierre

    2013-03-01

    Although nitrogen stable isotope ratio (?15N) in macroalgae is widely used as a bioindicator of anthropogenic nitrogen inputs to the coastal zone, recent studies suggest the possible role of macroalgae metabolism in ?15N variability. Simultaneous determinations of ?15N of dissolved inorganic nitrogen (DIN) along the land-sea continuum, inter-species variability of ?15N and its sensitivity to environmental factors are necessary to confirm the efficiency of macroalgae ?15N in monitoring nitrogen origin in mixed-use watersheds. In this study, ?15N of annual and perennial macroalgae (Ulva sp., Enteromorpha sp., Fucus vesiculosus and Fucus serratus) are compared to ?15N-DIN along the Charente Estuary, after characterizing ?15N of the three main DIN sources (i.e. cultivated area, pasture, sewage treatment plant outlet). During late winter and spring, when human activities produce high DIN inputs, DIN sources exhibit distinct ?15N signals in nitrate (NO) and ammonium (NH): cultivated area (+6.5 ± 0.6‰ and +9.0 ± 11.0‰), pasture (+9.2 ± 1.8‰ and +12.4‰) and sewage treatment plant discharge (+16.9 ± 8.7‰ and +25.4 ± 5.9‰). While sources show distinct ?N- in this multiple source catchment, the overall mixture of NO sources - generally >95% DIN - leads to low variations of ?N-NO at the mouth of the estuary (+7.7 to +8.4‰). Even if estuarine ?N-NO values are not significantly different from pristine continental and oceanic site (+7.3‰ and +7.4‰), macroalgae ?15N values are generally higher at the mouth of the estuary. This highlights high anthropogenic DIN inputs in the estuary, and enhanced contribution of 15N-depleted NH in oceanic waters. Although seasonal variations in ?N-NO are low, the same temporal trends in macroalgae ?15N values at estuarine and oceanic sites, and inter-species differences in ?15N values, suggest that macroalgae ?15N values might be modified by the metabolic response of macroalgae to environmental parameters (e.g., temperature, light, DIN concentrations). Differences between annual and perennial macroalgae indicate both a higher integration time of perennial compared to annual macroalgae and the possible role of passive versus active uptake mechanisms. Further studies are required to characterize the sensitivity of macroalgae fractionation to variable environmental conditions and uptake mechanisms.

  1. Seasonal Abundance and Natural Inoculativity of Insect Vectors of Xylella fastidiosa in Oklahoma Tree Nurseries and Vineyards.

    PubMed

    Overall, Lisa M; Rebek, Eric J

    2015-12-01

    Xylella fastidiosa is the causative agent of diseases of perennial plants including peach, plum, elm, oak, pecan, and grape. This bacterial pathogen is transmitted by xylem-feeding insects. In recent years, Pierce's disease of grape has been detected in 10 counties in central and northeastern Oklahoma, prompting further investigation of the disease epidemiology in this state. We surveyed vineyards and tree nurseries in Oklahoma for potential insect vectors to determine species composition, infectivity, and natural inoculativity of commonly captured insect vectors. Yellow sticky cards were used to sample insect fauna at each location. Insects were removed from sticky cards and screened for X. fastidiosa using immunocapture-PCR to determine their infectivity. A second objective was to test the natural inoculativity of insect vectors that are found in vineyards. Graphocephala versuta (Say), Graphocephala coccinea (Forster), Paraulacizes irrorata (F.), Oncometopia orbona (F.), Cuerna costalis (F.), and Entylia carinata Germar were collected from vineyards and taken back to the lab to determine their natural inoculativity. Immunocapture-PCR was used to test plant and insect samples for presence of X. fastidiosa. The three most frequently captured species from vineyards and tree nurseries were G. versuta, Clastoptera xanthocephala Germar, and O. orbona. Of those insects screened for X. fastidiosa, 2.4% tested positive for the bacterium. Field-collected G. versuta were inoculative to both ragweed and alfalfa. Following a 7-d inoculation access period, a higher percentage of alfalfa became infected than ragweed. Results from this study provide insight into the epidemiology of X. fastidiosa in Oklahoma. PMID:26331482

  2. What's on the menu? Assessing microbial carbon sources and cycling in soils using natural abundance radiocarbon analysis

    NASA Astrophysics Data System (ADS)

    Mahmoudi, N.; Burns, L.; Mancini, S.; Fulthorpe, R.; Slater, G. F.

    2011-12-01

    Organic matter in soils is composed of diverse materials in various stages of decomposition. Soil organic matter is not in a single pool but rather in multiple carbon pools with different intrinsic turnover times that can be on annual to decadal and even millennial timescales. Microorganisms can influence the total amount of carbon stored in soils and the turnover rates of these different pools. However, the links between microbes and their ability to utilize these various carbon pools are not well understood. Moreover, microbes have been shown to co-utilize a number of available carbon sources rather than a single carbon source under soil conditions which creates difficulties in identifying microbial carbon sources in the natural environment. Compound-specific radiocarbon analysis of microbial phospholipid fatty acids (PLFA) has become a useful tool in elucidating microbial carbon sources in complex environments with multiple carbon sources. We investigated microbial carbon cycling at an industrial site in Ontario which included a variety of carbon sources including vegetation, PAHs and natural organic matter (NOM). Using this approach, the 14C content of microbial membrane lipids (which reflects their carbon source) can be compared to surrounding carbon sources in order to assess which carbon source they are metabolizing and incorporating into their lipids. In addition, we assessed microbial community structure and diversity by analyzing amplified bacterial, eukaryotic and archaeal rDNA fragments with denaturing gel gradient electrophoresis (DGGE). The ?14C value for PLFAs ranged from +54 to -697% which indicates that microbial carbon sources across soils differ. The ?14CPLFA for some soils is consistent with modern carbon sources while ?14CPLFA for other soils is consistent with natural organic matter including older pools of carbon. The microbial communities at this site are not metabolizing PAHs but rather they are utilizing various pools of natural organic matter as a carbon source. Moreover, our radiocarbon analysis of total organic carbon (TOC) and non-solvent extracted residue (representative of NOM) support the notion that soil organic matter is not homogenous and is comprised of multiple carbon fractions with different intrinsic turnover times. DNA fingerprinting revealed consistent levels of diversity across soils with the greatest diversity observed in the bacteria, followed by eukarya and finally archaea which had the lowest observed diversity. It was previously thought that there is a pool of refractory organic compounds that are biologically inert in soil however our findings indicate that microbes are able to utilize almost all available carbon sources in soil. These finding brings forth questions regarding the influence of microbes on soil organic matter stabilization and the bioavailability of different carbon pools.

  3. Mangrove isotopic (?15N and ?13C) fractionation across a nitrogen vs. phosphorus limitation gradient

    USGS Publications Warehouse

    Mckee, Karen L.; Feller, Ilka C.; Popp, Marianne; Wanek, Wolfgang

    2002-01-01

    Mangrove islands in Belize are characterized by a unique switching from nitrogen (N) to phosphorus (P) limitation to tree growth from shoreline to interior. Fertilization has previously shown that Rhizophora mangle (red mangrove) fringe trees (5–6 m tall) growing along the shoreline are N limited; dwarf trees (!1.5 m tall) in the forestinterior are P limited; and transition trees (2–4 m tall) are co-limited by both N and P.  Growth patterns paralleled a landward decrease in soil flushing by tides and an increase in bioavailable N, but P availability remained consistently low across the gradient. Stable isotopic composition was measured in R. mangle leaves to aid in explaining this nutrient switching pattern and growth variation. Along control transects, leaf !15N decreased from "0.10‰ (fringe) to #5.38‰ (dwarf). The !15N of N-fertilized trees also varied spatially, but the values were consistently more negative (by $3‰) compared to control trees. Spatial variation in !15N values disappeared when the trees were fertilized with P, and values averaged "0.12‰, similar to that in control fringe trees. Neither variation in source inputs nor microbial fractionation could fully account for the observed patterns in !15N. The results instead suggest that the lower !15N values in transition and dwarf control trees were due to plant fractionation as a consequence of slower growth and lower N demand. P fertilization increased N demand and decreased fractionation. Although leaf !13C was unaffected by fertilization, values increased from fringe (#28.6‰) to transition (#27.9‰) to dwarf (#26.4‰) zones, indicating spatial variation in environmental stresses affecting stomatal conductance or carboxylation. The results thus suggest an interaction of external supply, internal demand, and plant ability to acquire nutrients under different hydro-edaphic conditions that vary across this tree-height gradient. The findings not only aid in understanding mangrove discrimination of nitrogen and carbon isotopes, but also have implications for identifying nutrient loading and other stress conditions in coastal systems dominated by mangroves.

  4. A 15N-poor isotopic composition for the solar system as shown by Genesis solar wind samples.

    PubMed

    Marty, B; Chaussidon, M; Wiens, R C; Jurewicz, A J G; Burnett, D S

    2011-06-24

    The Genesis mission sampled solar wind ions to document the elemental and isotopic compositions of the Sun and, by inference, of the protosolar nebula. Nitrogen was a key target element because the extent and origin of its isotopic variations in solar system materials remain unknown. Isotopic analysis of a Genesis Solar Wind Concentrator target material shows that implanted solar wind nitrogen has a (15)N/(14)N ratio of 2.18 ± 0.02 × 10(-3) (that is, ?40% poorer in (15)N relative to terrestrial atmosphere). The (15)N/(14)N ratio of the protosolar nebula was 2.27 ± 0.03 × 10(-3), which is the lowest (15)N/(14)N ratio known for solar system objects. This result demonstrates the extreme nitrogen isotopic heterogeneity of the nascent solar system and accounts for the (15)N-depleted components observed in solar system reservoirs. PMID:21700869

  5. Structure effects in the $^{15}$N($n,\\gamma$)$^{16}$N radiative capture reaction from the Coulomb dissociation of $^{16}$N

    E-print Network

    Neelam,; Chatterjee, R

    2015-01-01

    Purpose : The aim of this paper is to calculate the $^{15}$N($n, \\gamma$)$^{16}$N radiative capture cross section and its subsequent reaction rate by an indirect method and in that process investigate the effects of spectroscopic factors of different levels of $^{16}$N to the cross section. Method : A fully quantum mechanical Coulomb breakup theory under the aegis of post-form distorted wave Born approximation is used to calculate the Coulomb breakup of $^{16}$N on Pb at 100 MeV/u. This is then related to the photodisintegration cross section of $^{16}$N($\\gamma, n$)$^{15}$N and subsequently invoking the principle of detailed balance, the $^{15}$N($n, \\gamma$)$^{16}$N capture cross section is calculated. Results : The non-resonant capture cross section is calculated with spectroscopic factors from the shell model and those extracted (including uncertainties) from two recent experiments. The data seems to favor a more single particle nature for the low-lying states of $^{16}$N. The total neutron capture rate i...

  6. 13C and 15N allocations of two alpine species from early and late snowmelt locations reflect their different growth strategies

    PubMed Central

    Baptist, Florence; Tcherkez, Guillaume; Aubert, Serge; Pontailler, Jean-Yves; Choler, Philippe; Nogués, Salvador

    2009-01-01

    Intense efforts are currently devoted to disentangling the relationships between plant carbon (C) allocation patterns and soil nitrogen (N) availability because of their consequences for growth and more generally for C sequestration. In cold ecosystems, only a few studies have addressed whole-plant C and/or N allocation along natural elevational or topographical gradients. 12C/13C and 14N/15N isotope techniques have been used to elucidate C and N partitioning in two alpine graminoids characterized by contrasted nutrient economies: a slow-growing species, Kobresia myosuroides (KM), and a fast-growing species, Carex foetida (CF), located in early and late snowmelt habitats, respectively, within the alpine tundra (French Alps). CF allocated higher labelling-related 13C content belowground and produced more root biomass. Furthermore, assimilates transferred to the roots were preferentially used for growth rather than respiration and tended to favour N reduction in this compartment. Accordingly, this species had higher 15N uptake efficiency than KM and a higher translocation of reduced 15N to aboveground organs. These results suggest that at the whole-plant level, there is a compromise between N acquisition/reduction and C allocation patterns for optimized growth. PMID:19401411

  7. Why so low? Making sense of 15N-depleted nitrogen isotope values in the Late Cretaceous.

    NASA Astrophysics Data System (ADS)

    Junium, C. K.; Meyers, S. R.; Arthur, M. A.

    2014-12-01

    Sedimentary organic matter from Cretaceous Oceanic Anoxic Events is characterized by universally low ?15N values. This observation has generated significant curiosity in the paleoceanographic community and has resulted in several conceptual models that aim to explain the 15N-depletion. The unifying element in these hypotheses is widespread anoxia and a series of nitrogen and/or metal cycling feedbacks. To address these hypotheses I will examine an interval in the middle Turonian (92.0 to 90.8 Ma) that demonstrates the impacts of redox and climate variability on nitrogen cycle dynamics. New N-isotope measurements from ODP Site 1259, Demerara Rise (DR) reveal ?15N values that range from +0.2‰ to -3.5‰ and oscillate by 1.5‰ to 3‰ over 1.6 Ma. A new astronomical time scale reveals a strong ~100 ka cyclicity in ?15N with little variance at ~400 ka through the mid-Turonian. The highest ?15N values and the largest amplitude ~100 ka cycles are found within the proposed glacial interval and cooler sea surface temperatures. The persistence of the ~100 ka ?15N cycle and ?15N maxima suggests a strong link between oceanic ventilation/circulation, climate, and the oscillations in ?15N are readily explained by variations in oxidation and expansion in the extent of denitrification within anoxic intermediate waters. These data confirm the strong link between water column redox variability and low ?15N values, but the exact mechanism of the 15N-depletion remains elusive.

  8. The perils and promises of microbial abundance: novel natures and model ecosystems, from artisanal cheese to alien seas.

    PubMed

    Paxson, Heather; Helmreich, Stefan

    2014-04-01

    Microbial life has been much in the news. From outbreaks of Escherichia coli to discussions of the benefits of raw and fermented foods to recent reports of life forms capable of living in extreme environments, the modest microbe has become a figure for thinking through the presents and possible futures of nature, writ large as well as small. Noting that dominant representations of microbial life have shifted from an idiom of peril to one of promise, we argue that microbes--especially when thriving as microbial communities--are being upheld as model ecosystems in a prescriptive sense, as tokens of how organisms and human ecological relations with them could, should, or might be. We do so in reference to two case studies: the regulatory politics of artisanal cheese and the speculative research of astrobiology. To think of and with microbial communities as model ecosystems offers a corrective to the scientific determinisms we detect in some recent calls to attend to the materiality of scientific objects. PMID:24941610

  9. Submillimeter Observations of Titan: Global Measures of Stratospheric Temperature, CO, HCN, HC3N, and the Isotopic Ratios 12C/13C and 14N/15N

    NASA Astrophysics Data System (ADS)

    Gurwell, Mark A.

    2004-11-01

    Interferometric observations of the atmosphere of Titan were performed with the Submillimeter Array on two nights in 2004 February to investigate the global average vertical distributions of several molecular species above the tropopause. Rotational transitions of CO, isomers of HCN, and HC3N were simultaneously recorded. The abundance of CO is determined to be 51+/-4 parts per million (ppm), constant with altitude. The vertical profile of HCN is dependent on the assumed temperature but generally increases from 30 parts per billion at the condensation altitude (~83 km) to 5 ppm at ~300 km. Furthermore, the central core of the HCN emission is strong and can be reproduced only if the upper stratospheric temperature increases with altitude. The isotopic ratios are determined to be 12C/13C=132+/-25 and 14N/15N=94+/-13 assuming the Coustenis & Bézard temperature profile. If the Lellouch temperature profile is assumed, the ratios decrease to 12C/13C=108+/-20 and 14N/15N=72+/-9. The vertical profile of HC3N is consistent with that derived by Marten et al.

  10. 13C natural abundance in serum retinol acts as a biomarker for increases in dietary provitamin A.

    PubMed

    Howe, Julie A; Valentine, Ashley R; Hull, Angela K; Tanumihardjo, Sherry A

    2009-02-01

    The natural isotopic composition of 13C and 12C in tissues is largely determined by the diet. Sources of provitamin A carotenoids (e.g., vegetables) typically have a lower 13C to 12C ratio (13C:12C) than preformed vitamin A sources (i.e., dairy and meat) from corn-fed animals, which are prevalent in the US. The 13C:12C of serum retinol (13C:12C-retinol) was evaluated as a biomarker for vegetable intake in a 3-mo dietary intervention designed to promote weight-loss by increased vegetable consumption or reduced calorie and fat intake. Subjects were 21-50 y of age with a BMI between 30-40 kg/m2 and were enrolled from one geographic area in the US. The high vegetable group (n=20) was encouraged to increase daily vegetable and fruit consumption to 0.95 liter vegetables and 0.24-0.35 liter fruits. The caloric reduction group (n=17) was encouraged to lower caloric intake by 500 kcal and consume

  11. Localization of 15N uptake in a Tibetan alpine Kobresia pasture

    NASA Astrophysics Data System (ADS)

    Schleuß, Per-Marten; Kuzyakov, Yakov

    2014-05-01

    The Kobresia Pygmea ecotone covers approximately 450.000 km2 and is of large global and regional importance due several socio-ecological aspects. For instance Kobresia pastures store high amounts of carbon, nitrogen and other nutrients, represent large grazing areas for herbivores, provide a fast regrowth after grazing events and protect against mechanical degradation and soil erosion. However, Kobresia pastures are assumed to be a grazing induced and are accompanied with distinct root mats varying in thickness between 5-30 cm. Yet, less is known about the morphology and the functions of this root mats, especially in the background of a progressing degradation due to changes of climate and management. Thus we aimed to identify the importance of single soil layers for plant nutrition. Accordingly, nitrogen uptake from different soil depths and its remain in above-ground biomass (AGB), belowground biomass (BGB) and soil were determined by using a 15N pulse labeling approach during the vegetation period in summer 2012. 15N urea was injected into six different soil depths (0.5 cm, 2.5 cm, 7.5 cm, 12.5 cm, 17.5 cm, 22.5 cm / for each 4 replicates) and plots were sampled 45 days after the labeling. For soil and BGB samples were taken in strict sample intervals of 0-1 cm, 1-5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm. Results indicate that total recovery (including AGB, BGB and soil) was highest, if tracer was injected into the top 5 cm and subsequently decreased with decreasing injection depth. This is especially the case for the 15N recovery of BGB, which is clearly attributed to the root density and strongly decreased with soil depth. In contrast, the root activity derived from the 15N content of roots increased with soil depth, which is primary associated to a proportionate increase of living roots related to dead roots. However, most 15N was captured in plant biomass (67.5-85.3 % of total recovery), indicating high 15N uptake efficiency possibly due to N limitation of Kobresia ecosystems. Considering only the nitrogen uptake of AGB hardly any differences appeared between the six injection depths. Nevertheless, it could be shown, that 50.4 % percent of total variance of AGB nitrogen uptake could be explained by combining root density and root activity. Concluding, from the upper root mat horizons highest amounts of nitrogen were taken up by plants, because root densities are correspondingly high. However, in deeper root mat layers the root activity increases and accordingly plays a key role for plant nitrogen supply in this depth. Underlying causes for increasing root activities may be better soil moisture conditions, lower variation of soil temperature and/or a higher access to plant available nitrogen in deeper soil layers.Please fill in your abstract text.

  12. Increased ectomycorrhizal fungal abundance after long-term fertilization and warming of two arctic tundra ecosystems.

    PubMed

    Clemmensen, Karina E; Michelsen, Anders; Jonasson, Sven; Shaver, Gaius R

    2006-01-01

    Shrub abundance is expected to increase with enhanced temperature and nutrient availability in the Arctic, and associated changes in abundance of ectomycorrhizal (EM) fungi could be a key link between plant responses and longer-term changes in soil organic matter storage. This study quantifies the response in EM fungal abundance to long-term warming and fertilization in two arctic ecosystems with contrasting responses of the EM shrub Betula nana. Ergosterol was used as a biomarker for living fungal biomass in roots and organic soil and ingrowth bags were used to estimate EM mycelial production. We measured 15N and 13C natural abundance to identify the EM-saprotrophic divide in fungal sporocarps and to validate the EM origin of mycelia in the ingrowth bags. Fungal biomass in soil and EM mycelial production increased with fertilization at both tundra sites, and with warming at one site. This was caused partly by increased dominance of EM plants and partly by stimulation of EM mycelial growth. We conclude that cycling of carbon and nitrogen through EM fungi will increase when strongly nutrient-limited arctic ecosystems are exposed to a warmer and more nutrient-rich environment. This has potential consequences for below-ground litter quality and quantity, and for accumulation of organic matter in arctic soils. PMID:16866945

  13. Competitive 15N kinetic isotope effects of nitrogenase-catalyzed dinitrogen reduction.

    PubMed

    Sra, Amandeep K; Hu, Yilin; Martin, Glen E; Snow, Daniel D; Ribbe, Markus W; Kohen, Amnon

    2004-10-13

    Biological N2 fixation is achieved under ambient conditions by enzymatic catalysis. The enzyme nitrogenase has been studied extensively, but the N2 chemical reduction step is, by far, not rate limiting and hard to examine. A new method was developed that allows studying the reduction transition state within the enzyme's complex kinetic cascade by means of the 15N kinetic isotope effect on the reaction's second-order rate constant, V/K. A value of 1.7% +/- 0.2% was measured. PMID:15469259

  14. Uptake of stormwater nitrogen in bioretention systems demonstrated from 15N tracer techniques

    NASA Astrophysics Data System (ADS)

    Houdeshel, D.; Hultine, K. R.; Pomeroy, C. A.

    2012-12-01

    Bioretention stormwater management systems are engineered ecosystems that capture urban stormwater in order to reduce the harmful effects of stormwater pollution on receiving waters. Bioretention systems have been shown to be effective at reducing the volume of runoff, and thereby reduce the nutrient loading to receiving waters from urban areas. However, little work has been done to evaluate the treatment processes that are responsible for reductions in effluent nitrogen (N). We hypothesize that the pulses of inorganic nitrogen associated with urban runoff events are captured in the plat tissues within these systems and not adsorbed to the soil media, thus creating a long-term, sustainable treatment approach to reducing the total nutrient loading to receiving waters. Nitrogen treatment performance was tested on two bioretention systems in Salt Lake City, UT: 1) an upland native community that does not require irrigation in semi-arid climates, and 2) a wetland community that requires 250 l of daily irrigation to offset the relatively high evaporative demand in the region. Each cell is sized to treat a 2.5 cm storm from a 140 m2 impervious surface: the area of the bioretention system is 10 m2. To test the N removal performance of each system, runoff events were simulated to represent an average precipitation regime using a synthetic stormwater blend starting in January, 2012. Effluent was collected from an underdrain and analyzed for total nitrogen (TN); mass removal was calculated for each month by subtracting the TN mass added to the garden minus the TN mass that flowed out of the garden. To test the hypothesis that plants assimilate stormwater N, 4 g of 100 atom% 15N NH4NO3 tracer was used as the N source in the synthetic stormwater during the first 2,000 l synthetic storm event in May. This isotopic label was calculated to enrich the total N pool of each garden to 100‰ 15N/14Nair. New growth was harvested from each plant in both cells and analyzed for 15N before the isotopic label was introduced and weekly thereafter. In May 2012, the upland garden captured 6.2 grams of TN from the added stormwater (55% of TN added), and the wetland garden captured 7.1 grams of TN from the added stormwater (67% of TN added). Within two weeks of adding the label, the 15N ratio increased 500‰ to 3,000‰ in all plant tissues tested in both systems. The results of the isotopic labeling experiment support the hypothesis that the plants used in both vegetated bioretention systems directly contribute to stormwater N treatment through N assimilation.

  15. Determination of the ?15N of nitrate in solids; RSIL lab code 2894

    USGS Publications Warehouse

    Coplen, Tyler B.; Qi, Haiping; Revesz, Kinga; Casciotti, Karen; Hannon, Janet E.

    2007-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2894 is to determine the ?15N of nitrate (NO3-) in solids. The nitrate fraction of the nitrogen species is dissolved by water (called leaching) and can be analyzed by the bacterial method covered in RSIL lab code 2899. After leaching, the ?15N of the dissolved NO3- is analyzed by conversion of the NO3- to nitrous oxide (N2O), which serves as the analyte for mass spectrometry. A culture of denitrifying bacteria is used in the enzymatic conversion of NO3- to N2O, which follows the pathway shown in equation 1: NO3- ? NO2- ? NO ? 1/2 N2O (1) Because the bacteria Pseudomonas aureofaciens lack N2O reductive activity, the reaction stops at N2O, unlike the typical denitrification reaction that goes to N2. After several hours, the conversion is complete, and the N2O is extracted from the vial, separated from volatile organic vapor and water vapor by an automated -65 °C isopropanol-slush trap, a Nafion drier, a CO2 and water removal unit (Costech #021020 carbon dioxide absorbent with Mg(ClO4)2), and trapped in a small-volume trap immersed in liquid nitrogen with a modified Finnigan MAT (now Thermo Scientific) GasBench 2 introduction system. After the N2O is released, it is further purified by gas chromatography before introduction to the isotope-ratio mass spectrometer (IRMS). The IRMS is a Thermo Scientific Delta V Plus continuous flow IRMS (CF-IRMS). It has a universal triple collector, consisting of two wide cups with a narrow cup in the middle; it is capable of simultaneously measuring mass/charge (m/z) of the N2O molecule 44, 45, and 46. The ion beams from these m/z values are as follows: m/z = 44 = N2O = 14N14N16O; m/z = 45 = N2O = 14N15N16O or 14N14N17O; m/z = 46 = N2O = 14N14N18O. The 17O contributions to the m/z 44 and m/z 45 ion beams are accounted for before ?15N values are reported.

  16. Determination of the ?15N and ?18O of nitrate in water; RSIL lab code 2900

    USGS Publications Warehouse

    Coplen, Tyler B.; Qi, Haiping; Revesz, Kinga; Casciotti, Karen; Hannon, Janet E.

    2007-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2900 is to determine the ?15N and ?18O of nitrate (NO3-) in water. The ?15N and ?18O of the dissolved NO3- are analyzed by converting the NO3- to nitrous oxide (N2O), which serves as the analyte for mass spectrometry. A culture of denitrifying bacteria is used in the enzymatic conversion of the NO3- to N2O, which follows the pathway shown in equation 1: NO3- ? NO2- ? NO ? 1/2 N2O (1) Because the bacteria Pseudomonas aureofaciens lack N2O reductive activity, the reaction stops at N2O, unlike the typical denitrification reaction that goes to N2. After several hours, the conversion is complete, and the N2O is extracted from the vial, separated from volatile organic vapor and water vapor by an automated -65 °C isopropanol-slush trap, a Nafion drier, a CO2 and water removal unit (Costech #021020 carbon dioxide absorbent with Mg(ClO4)2), and trapped in a small-volume trap immersed in liquid nitrogen with a modified Finnigan MAT (now Thermo Scientific) GasBench 2 introduction system. After the N2O is released, it is further purified by gas chromatography before introduction to the isotope-ratio mass spectrometer (IRMS). The IRMS is a Thermo Scientific Delta V Plus continuous flow IRMS (CF-IRMS). It has a universal triple collector, consisting of two wide cups with a narrow cup in the middle; it is capable of simultaneously measuring mass/charge (m/z) of the N2O molecule 44, 45, and 46. The ion beams from these m/z values are as follows: m/z = 44 = N2O = 14N14N16O; m/z = 45 = N2O = 14N15N16O or 14N14N17O; m/z = 46 = N2O = 14N14N18O. The 17O contributions to the m/z 44 and m/z 45 ion beams are accounted for before ?15N values are reported.

  17. Determination of the ?15N of nitrate in water; RSIL lab code 2899

    USGS Publications Warehouse

    Coplen, Tyler B.; Qi, Haiping; Revesz, Kinga; Casciotti, Karen; Hannon, Janet E.

    2007-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2899 is to determine the ?15N of nitrate (NO3-) in water. The ?15N of the dissolved NO3- is analyzed by conversion of the NO3- to nitrous oxide (N2O), which serves as the analyte for mass spectrometry. A culture of denitrifying bacteria is used in the enzymatic conversion of the NO3- to N2O, which follows the pathway shown in equation 1: NO3- ? NO2- ? NO ? 1/2 N2O (1) Because the bacteria Pseudomonas aureofaciens lack N2O reductive activity, the reaction stops at N2O, unlike the typical denitrification reaction that goes to N2. After several hours, the conversion is complete, and the N2O is extracted from the vial, separated from volatile organic vapor and water vapor by an automated -65 °C isopropanol-slush trap, a Nafion drier, a CO2 and water removal unit (Costech #021020 carbon dioxide absorbent with Mg(ClO4)2), and trapped in a small-volume trap immersed in liquid nitrogen with a modified Finnigan MAT (now Thermo Scientific) GasBench 2 introduction system. After the N2O is released, it is further purified by gas chromatography before introduction to the isotope-ratio mass spectrometer (IRMS). The IRMS is a Thermo Scientific Delta V Plus continuous flow IRMS (CF-IRMS). It has a universal triple collector, consisting of two wide cups with a narrow cup in the middle; it is capable of simultaneously measuring mass/charge (m/z) of the N2O molecule 44, 45, and 46. The ion beams from these m/z values are as follows: m/z = 44 = N2O = 14N14N16O; m/z = 45 = N2O = 14N15N16O or 14N14N17O; m/z = 46 = N2O = 14N14N18O. The 17O contributions to the m/z 44 and m/z 45 ion beams are accounted for before ?15N values are reported.

  18. Determination of the ?15N and ?18O of nitrate in solids; RSIL lab code 2897

    USGS Publications Warehouse

    Coplen, Tyler B.; Qi, Haiping; Revesz, Kinga; Casciotti, Karen; Hannon, Janet E.

    2007-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2897 is to determine the ?15N and ?18O of nitrate (NO3-) in solids. The NO3- fraction of the nitrogen species is dissolved by water (called leaching) and can be analyzed by the bacterial method covered in RSIL lab code 2900. After leaching, the ?15N and ?18O of the dissolved NO3- is analyzed by conversion of the NO3- to nitrous oxide (N2O), which serves as the analyte for mass spectrometry. A culture of denitrifying bacteria is used in the enzymatic conversion of NO3- to N2O, which follows the pathway shown in equation 1: NO3- ? NO2- ? NO ? 1/2 N2O (1) Because the bacteria Pseudomonas aureofaciens lack N2O reductive activity, the reaction stops at N2O, unlike the typical denitrification reaction that goes to N2. After several hours, the conversion is complete, and the N2O is extracted from the vial, separated from volatile organic vapor and water vapor by an automated -65 °C isopropanol-slush trap, a Nafion drier, a CO2 and water removal unit (Costech #021020 carbon dioxide absorbent with Mg(ClO4)2), and trapped in a small-volume trap immersed in liquid nitrogen with a modified Finnigan MAT (now Thermo Scientific) GasBench 2 introduction system. After the N2O is released, it is further purified by gas chromatography before introduction to the isotope-ratio mass spectrometer (IRMS). The IRMS is a Thermo Scientific Delta V Plus continuous flow IRMS (CF-IRMS). It has a universal triple collector, consisting of two wide cups with a narrow cup in the middle; it is capable of simultaneously measuring mass/charge (m/z) of the N2O molecule 44, 45, and 46. The ion beams from these m/z values are as follows: m/z = 44 = N2O = 14N14N16O; m/z = 45 = N2O = 14N15N16O or 14N14N17O; m/z = 46 = N2O = 14N14N18O. The 17O contributions to the m/z 44 and m/z 45 ion beams are accounted for before ?15N values are reported.

  19. Optical Microscopy Characterization for Borehole U-15n#12 in Support of NCNS Source Physics Experiment

    SciTech Connect

    Wilson, Jennifer E.; Sussman, Aviva Joy

    2015-05-22

    Optical microscopy characterization of thin sections from corehole U-15n#12 is part of a larger material characterization effort for the Source Physics Experiment (SPE). The SPE program was conducted in Nevada with a series of explosive tests designed to study the generation and propagation of seismic waves inside Stock quartz monzonite. Optical microscopy analysis includes the following: 1) imaging of full thin sections (scans and mosaic maps); 2) high magnification imaging of petrographic texture (grain size, foliations, fractures, etc.); and 3) measurement of microfracture density.

  20. Changes in Natural Abundance Carbon Stable isotopes of Human Blood and Saliva After 24 Days of Controlled Carbohydrate Supplementation

    NASA Astrophysics Data System (ADS)

    Kraft, R. A.; Jahren, A. H.; Baer, D. J.; Caballero, B.

    2008-12-01

    With the advent of corporate agriculture, large-scale economic decisions have given rise to unique global environmental effects. Emphasis on corn production results in dramatic changes in nitrogen and water cycling via the intensive cultivation practices necessary to support Zea mays (Tilman, 1998). In particular, consumption of corn derived food additive high-fructose corn syrup (HFCS) has increased more than 1000% since 1970 and may be associated with the epidemics of obesity and diabetes (Bray et al., 2004). Plausible mechanisms for an adverse effect of fructose load on glucose homeostasis have been proposed (Havel, 2005). The unusually heavy 13C signature of corn, as compared to other plants, offers the opportunity to develop a biomarker for sugar consumption. Among the many experiments that are needed to establish such a technique, the demonstration of change in 13C signature of human tissues with known change in carbohydrate consumption is foremost. Here we report on a controlled feeding study performed in cooperation with the United States Department of Agriculture (USDA), to test the effect of supplementation of human diet with carbohydrate of known ?13C value. During this study, 13 individuals were fed a typical American diet (32% calories from fat, 15% calories from protein, 53% carbohydrate) for ~six months. Each participant was fed a random sequence of carbohydrate supplements (50 grams of supplement per day): 1. resistant maltodextrin (?13C = -10.59‰); 2. maltodextrin (?13C = -23.95‰); 3. a 50-50 mixture of the two (?13C = -15.94‰). After 24 days of feeding, subjects showed enrichment in blood serum that was significantly correlated (p = 0.0038) with the ?13C value of the supplement. However, blood clot and saliva showed no such correlation, suggesting that the half-lives of these substrates may render them unsuitable for carbohydrate dietary reconstruction over day-to-month timescales. All subjects of the study showed a net enrichment in the ?13C value of their blood and saliva relative to baseline: blood clot was enriched by 0.27‰; blood serum by 0.50‰ and saliva by 1.12‰. We believe this overall enrichment resulted from a 13C-enriched bulk diet (?13C = - 20.42‰) relative to the subjects free-living diet. Evidence for this derives from inspection of foods within the bulk diet provided, compared to published profiles of the typical American diet. We will discuss possible complicating factors, such as differential absorption and metabolism of the supplements according to solubility and caloric value. These results are encouraging for the development of a ?13C blood serum biomarker that, in the company of other tests, could be used to indicate a change in carbohydrate intake. Bray, G.A., Nielsen, S.J. and Popkin, B.M., 2004. Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. American Journal of Clinical Nutrition, 79: 537-543. Havel, P.J., 2005. Dietary fructose: Implications for dysregulation of energy homeostasis and lipid/carbohydrate metabolism. Nutrition Reviews, 63(5): 133-157. Tilman D., 1998. The greening of the green revolution. Nature, 396:211-212.

  1. Abundances of Primordial Elements

    NASA Astrophysics Data System (ADS)

    Kennicutt, Robert

    1996-05-01

    The primordial isotopic abundances of hydrogen, helium, and lithium provide an important test of big-bang nucleosynthesis (BBN) theory and constraints on the baryonic density of the universe. Recent advances in astronomical instrumentation, including the advent of the Keck 10m telescope and the Hubble Space Telescope (HST), have provided tighter measurements of these abundances and stimulated a re-examination of the standard BBN model in the light of these new data. This talk will review recent measurements of the cosmic abundances of D, ^4He, ^3He, and ^7Li and their implications for the cosmological baryon density and BBN. Recent observations of deuterium in the local interstellar medium with HST and in high-redshift intergalactic clouds with Keck have substantially reduced the uncertainty in the D/H value and provide better estimates of the effects of stellar processing on the measured abundance. Progress has also been made in the empirical determination of the primordial He and Li abundances, as measured from metal-poor ionized gas clouds and stars, respectively. Most of the remaining errors in these measurements are systematic in nature, involving uncertainties in line blending (D), atomic emissivities and ionization corrections (^4He), and in the effects of stellar processing on the observed abundance ratios (all species). Recent disagreements in the literature over the validity of the standard BBN model rest critically on how these systematic errors are estimated and propagated. A conservative assessment of the uncertainties suggests that the measured abundances are consistent with the standard model (N_? = 3) for a reasonable range of baryonic densities. Future improvements in the measurement of D/H and ^4He/H should provide an incisive test of the standard model and definitive limits on the cosmological nucleon-to-photon ratio and baryon density.

  2. 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 (?(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 ?(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 ?(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

  3. The coral ?15N record of terrestrial nitrate loading varies with river catchment land use

    NASA Astrophysics Data System (ADS)

    Yamazaki, A.; Watanabe, T.; Tsunogai, U.; Hasegawa, H.; Yamano, H.

    2015-03-01

    We analysed the nitrogen isotopes in two coral cores (?15Ncoral) from the mouth of the Todoroki River, Ishigaki Island, Japan, to examine whether the ?15Ncoral reflects the run-off of nitrate related to the land use in the river catchment. The two coral cores were used to examine the seasonal variation in ?15Ncoral for 14 years (CORE1; 1993-2007) and the annual variation of ?15Ncoral for 52 years (CORE2; 1958-2010). In CORE1, the 5-month running mean of ?15Ncoral was positively correlated with that of monthly precipitation, excluding all strong precipitation events (>150 mm d-1). In CORE2, the ?15Ncoral mean in the earlier period (1958-1980) was 1.0 ‰ greater than that in the later period (1981-2010). The annual averages of ?15Ncoral are positively correlated with the total precipitation in the rainy season (May-June) for both time periods. The difference in the ?15Ncoral between the earlier and later periods is probably caused by the land use changed from paddy fields with 15N-rich manure to sugar cane fields in the early 1980s. Although some uncertainties still remain regarding the precision of ?15N coral proxy records, this study emphasises the clear potential for their use in reconstructing terrestrial nitrate discharge records from corals.

  4. NMR monitoring of accumulation and folding of 15N-labeled protein overexpressed in Pichia pastoris.

    PubMed

    de Lamotte, F; Boze, H; Blanchard, C; Klein, C; Moulin, G; Gautier, M F; Delsuc, M A

    2001-07-01

    Postgenomic studies have led to an increasing demand for isotope-labeled proteins. We present a method for producing large quantities of truly native (15)N-labeled protein. Based on the secretion capabilities of the yeast Pichia pastoris, the recombinant protein is easily purified in a single step as it is secreted. Control of all nitrogen sources permits very high labeling yields. As a result, accumulation and folding of the recombinant protein can be monitored by heteronuclear NMR without purification. Comparison of sample spectra with the spectrum of the purified recombinant protein allows detection of the secreted protein in the culture and monitoring of its folding, from the start of the induction phase. The detection limit for a (15)N-labeled protein is estimated as 20 microM and corresponds, for a 10-kDa protein, to a load of 40 mg/liter in the fermentor. This concentration is reached by most reported preparations in P. pastoris. Further concentration by ultrafiltration would compensate for lower production. This procedure may be useful in many structural genomics and combinatorial chemistry screening projects where most protein productions meet the requirements for this method. PMID:11437608

  5. Covalent binding of aniline to humic substances. 2. 15N NMR studies of nucleophilic addition reactions

    USGS Publications Warehouse

    Thorn, K.A.; Pettigrew, P.J.; Goldenberg, W.S.; Weber, E.J.

    1996-01-01

    Aromatic amines are known to undergo covalent binding with humic substances in the environment. Although previous studies have examined reaction conditions and proposed mechanisms, there has been no direct spectroscopic evidence for the covalent binding of the amines to the functional groups in humic substances. In order to further elucidate the reaction mechanisms, the Suwannee River and IHSS soil fulvic and humic acids were reacted with 15N-labeled aniline at pH 6 and analyzed using 15N NMR spectrometry. Aniline underwent nucleophilic addition reactions with the quinone and other carbonyl groups in the samples and became incorporated in the form of anilinohydroquinone, anilinoquinone, anilide, imine, and heterocyclic nitrogen, the latter comprising 50% or more of the bound amine. The anilide and anilinohydroquinone nitrogens were determined to be susceptible to chemical exchange by ammonia. In the case of Suwannee River fulvic acid, reaction under anoxic conditions and pretreatment with sodium borohydride or hydroxylamine prior to reaction under oxic conditions resulted in a decrease in the proportion of anilinohydroquinone nitrogen incorporated. The relative decrease in the incorporation of anilinohydroquinone nitrogen with respect to anilinoquinone nitrogen under anoxic conditions suggested that inter- or intramolecular redox reactions accompanied the nucleophilic addition reactions.

  6. Abrupt recent shift in ?13C and ?15N values in Adélie penguin eggshell in Antarctica

    PubMed Central

    Emslie, Steven D.; Patterson, William P.

    2007-01-01

    Stable isotope values of carbon (?13C) and nitrogen (?15N) in blood, feathers, eggshell, and bone have been used in seabird studies since the 1980s, providing a valuable source of information on diet, foraging patterns, and migratory behavior in these birds. These techniques can also be applied to fossil material when preservation of bone and other tissues is sufficient. Excavations of abandoned Adélie penguin (Pygoscelis adeliae) colonies in Antarctica often provide well preserved remains of bone, feathers, and eggshell dating from hundreds to thousands of years B.P. Herein we present an ?38,000-year time series of ?13C and ?15N values of Adélie penguin eggshell from abandoned colonies located in three major regions of Antarctica. Results indicate an abrupt shift to lower-trophic prey in penguin diets within the past ?200 years. We posit that penguins only recently began to rely on krill as a major portion of their diet, in conjunction with the removal of baleen whales and krill-eating seals during the historic whaling era. Our results support the “krill surplus” hypothesis that predicts excess krill availability in the Southern Ocean after this period of exploitation. PMID:17620620

  7. Quantifying foliar uptake of gaseous nitrogen dioxide using enriched foliar delta15N values.

    PubMed

    Vallano, Dena M; Sparks, Jed P

    2008-01-01

    The magnitude and impact of gaseous nitrogen dioxide (NO(2)) directly entering the leaves were investigated using foliar nitrogen isotopic composition (delta(15)N) values in tomato (Lycopersicon esculentum) and tobacco (Nicotiana tabacum). Using a hydroponics-fumigation system, (15)NO(2) (20 and 40 ppb) was supplied to shoot systems and (50 and 500 microM) was supplied to root systems. Morphological, stable isotope and nitrate reductase activity (NRA) analyses were used to quantify foliar NO(2) uptake and to examine whether realistic concentrations of NO(2) influenced plant metabolism. Nicotiana tabacum and L. esculentum incorporated 15 and 11%, respectively, of (15)NO(2)-N into total biomass via foliar uptake under low supply. On a mass basis, N. tabacum and L. esculentum incorporated 3.3 +/- 0.9 and 3.1 +/- 0.8 mg of (15)NO(2)-N into biomass, respectively, regardless of availability. There were no strong effects on biomass accumulation or allocation, leaf delta(13)C values, or leaf or root NRA in response to NO(2) exposure. Foliar NO(2 )uptake may contribute a significant proportion of N to plant metabolism under N-limited conditions, does not strongly influence growth at 40 ppb, and may be traced using foliar delta(15)N values. PMID:18069953

  8. Molecular Investigation of the Short-term Sequestration of Natural Abundance 13C -labelled Cow Dung in the Surface Horizons of a Temperate Grassland Soil

    NASA Astrophysics Data System (ADS)

    Dungait, J.; Bol, R.; Evershed, R. P.

    2004-12-01

    An adequate understanding of the carbon (C) sequestration potential of grasslands requires that the quantity and residence times of C inputs be measured. Herbivore dung is largely comprised of plant cell wall material, a significant source of stable C in intensively grazed temperate grassland ecosystems that contributes to the soil carbon budget. Our work uses compound-specific isotope analysis to identify the pattern of input of dung-derived compounds from natural abundance 13C/-labelled cow dung into the surface horizons of a temperate grassland soil over one year. C4 dung (? 13C \\-12.6 ‰ ) from maize fed cows was applied to a temperate grassland surface (? 13C \\-29.95 ‰ ) at IGER-North Wyke (Devon, UK), and dung remains and soil cores beneath the treatments collected at ? = 7, 14, 28, 56, 112, 224 and 372 days. Bulk dung carbon present in the 0\\-1 cm and 1\\-5 cm surface horizons of a grassland soil over one year was estimated using ? 13C between C4 dung and C3 dung, after Bol {\\et al.} (2000). The major biochemical components of dung were quantified using proximate forage fibre analyses, after Goering and Van Soest (1970) and identified using `wet' chemical and GC-MS methods. Plant cell wall polysaccharides and lignin were found to account for up to 67 {%} of dung dry matter. Hydrolysed polysaccharides were prepared as alditol acetates for analyses (after Docherty {\\et al.}, 2001), and a novel application of an off-line pyrolysis method applied to measure lignin-derived phenolic compounds (after Poole & van Bergen, 2002). This paper focuses on major events in the incorporation of dung carbon, estimated using natural abundance 13C&-slash;labelling technique. This revealed a major bulk input of dung carbon after a period of significant rainfall with a consequent decline in bulk soil ? 13C values until the end of the experiment (Dungait {\\et al.}, submitted). Findings will be presented revealing contribution of plant cell wall polysaccharides and lignin to these bulk ? 13C values, and their potential for sequestration considered. References: Bol, R., Amelung, W., Friedrich, C. Ostle, N. (2000). Tracing dung-derived carbon in temperate grassland using 13C natural abundance measurements. Soil Biology and Biochemistry, 32, 1337-1343. Goering and Van Soest (1970). Forage fibre analysis (apparatus, reagents, procedures and some applications). In: USDA-ARS Agricultural Handbook, 379. U. S. Government Printing Office, Washington D.C. Docherty, G., Jones, V. and Evershed, R.P. (2001). Practical and theoretical considerations in the gas chromatography/combustion/isotope ratio mass spectrometry ? 13C analysis of small polyfunctional compounds. Rapid Communications in Mass Spectrometry, 15, 730-738. Poole, I. & van Bergen, P. F. (2002). Carbon isotope ratio analysis of organic moieties from fossil mummified wood: establishing optimum conditions for off-line pyrolysis extraction using gas chromatography/mass spectrometry. Rapid Communications in Mass Spectrometry, 16, 1976-1981. Dungait, J. A. J., Bol, R. and Evershed, R.P. (submitted). The Fate of Dung Carbon in Temperate Grassland Soil: 1. Preliminary Findings Based on Bulk Stable Carbon Isotope Determinations. Isotopes in Health and Environmental Studies

  9. Nitrogen use efficiency evaluation of aerobic rice under field capacity water potential using 15N isotopic tracer technique

    NASA Astrophysics Data System (ADS)

    Wahid, Ahmad Nazrul Abd; Rahim, Sahibin Abd; Rahim, Khairuddin Abdul; Harun, Abdul Rahim

    2015-09-01

    This study was carried out to evaluate the efficiency use of the nitrogen fertilizer on aerobic rice varieties MR219-4 and MR219-9 which were grown aerobically under field capacity water potential at the controlled environment area or shield house. Direct 15N isotope tracer method was used in this study, whereby the 15N isotope was utilized as a tracer for nitrogen nutrient uptake. 15N isotope presence in the samples is determined by using emission spectrometer analysis and percentage of total nitrogen is determined by using Kjeldahl method. 15N atom access value contained in the sample will be used in determining the effectiveness of the use of nitrogen in fertilizers through the specific calculation formulas. In this work, the data several data of nitrogen derived from fertilizer (Ndff), total nitrogen, nitrogen uptake and nitrogen use efficiency was obtained.

  10. Detection of 2,4,6-Trinitrotoluene-Utilizing Anaerobic Bacteria by 15N and 13C Incorporation ?

    PubMed Central

    Gallagher, Erin M.; Young, Lily Y.; McGuinness, Lora M.; Kerkhof, Lee J.

    2010-01-01

    2,4,6-Trinitrotoluene (15N or 13C labeled) was added to Norfolk Harbor sediments to test whether anaerobic bacteria use TNT for growth. Stable-isotope probing (SIP)-terminal restriction fragment length polymorphism (TRFLP) detected peaks in the [15N]TNT cultures (60, 163, and 168 bp). The 60-bp peak was also present in the [13C]TNT cultures and was related to Lysobacter taiwanensis. PMID:20081008

  11. Using dual-bacterial denitrification to improve ?15N determinations of nitrates containing mass-independent 17O

    USGS Publications Warehouse

    Coplen, T.B.; Böhlke, J.K.; Casciotti, K.L.

    2004-01-01

    The bacterial denitrification method for isotopic analysis of nitrate using N2O generated from Pseudomonas aureofaciens may overestimate ??15N values by as much as 1-2??? for samples containing atmospheric nitrate because of mass-independent 17O variations in such samples. By analyzing such samples for ??15N and ??18O using the denitrifier Pseudomonas chlororaphis, one obtains nearly correct ??15N values because oxygen in N 2O generated by P. chlororaphis is primarily derived from H 2O. The difference between the apparent ??15N value determined with P. aureofaciens and that determined with P. chlororaphis, assuming mass-dependent oxygen isotopic fractionation, reflects the amount of mass-independent 17O in a nitrate sample. By interspersing nitrate isotopic reference materials having substantially different ?? 18O values with samples, one can normalize oxygen isotope ratios and determine the fractions of oxygen in N2O derived from the nitrate and from water with each denitrifier. This information can be used to improve ??15N values of nitrates having excess 17O. The same analyses also yield estimates of the magnitude of 17O excess in the nitrate (expressed as ??17O) that may be useful in some environmental studies. The 1-?? uncertainties of ??15N, ??18O and ??17O measurements are ??0.2, ??0.3 and ??5???, respectively. Copyright ?? 2004 John Wiley & Sons, Ltd.

  12. Chain packing in glassy polymers by natural-abundance 13C-13C spin diffusion using 2D centerband-only detection of exchange.

    PubMed

    Singh, Manmilan; Schaefer, Jacob

    2011-03-01

    The proximities of specific subgroups of nearest-neighbor chains in glassy polymers are revealed by distance-dependent (13)C-(13)C dipolar couplings and spin diffusion. The measurement of such proximities is practical even with natural-abundance levels of (13)C using a 2D version of centerband-only detection of exchange (CODEX). Two-dimensional CODEX is a relaxation-compensated experiment that avoids the problems associated with variations in T(1)(C)'s due to dynamic site heterogeneity in the glass. Isotropic chemical shifts are encoded in the t(1) preparation times before and after mixing, and variations in T(2)'s are compensated by an S(0) reference (no mixing). Data acquisition involves acquisition of an S(0) reference signal on alternate scans, and the active control of power amplifiers, to achieve stability and accuracy over long accumulation times. The model system to calibrate spin diffusion is the polymer itself. For a mixing time of 200 ms, only (13)C-(13)C pairs separated by one or two bonds (2.5 Å) show cross peaks, which therefore identify reference intrachain proximities. For a mixing time of 1200 ms, 5 Å interchain proximities appear. The resulting cross peaks are used in a simple and direct way to compare nonrandom chain packing for two commercial polycarbonates with decidedly different mechanical properties. PMID:21306158

  13. MILLIMETER-WAVE OBSERVATIONS OF CN AND HNC AND THEIR {sup 15}N ISOTOPOLOGUES: A NEW EVALUATION OF THE {sup 14}N/{sup 15}N RATIO ACROSS THE GALAXY

    SciTech Connect

    Adande, G. R.; Ziurys, L. M.

    2012-01-10

    The N = 1 {yields} 0 transitions of CN and C{sup 15}N (X{sup 2}{Sigma}{sup +}), as well as the J = 1 {yields} 0 lines of HN{sup 13}C and H{sup 15}NC, have been observed toward 11 molecular clouds using the new 3 mm ALMA-type receiver of the 12 m telescope of the Arizona Radio Observatory. These sources span a wide range of distances from the Galactic center and are all regions of star formation. From these observations, {sup 14}N/{sup 15}N ratios have been determined using two independent methods. First, the measurements of C{sup 14}N and C{sup 15}N were directly compared to establish this ratio, correcting for high opacities when needed, as indicated by the nitrogen hyperfine intensities. Second, the ratio was calculated from the quantity [HN{sup 13}C]/[H{sup 15}NC], determined from the HNC data, and then scaled by {sup 12}C/{sup 13}C ratios previously established, i.e., the so-called double isotope method. Values from both methods are in reasonable agreement, and fall in the range {approx}120-400, somewhat lower than previous {sup 14}N/{sup 15}N ratios derived from HCN. The ratios exhibit a distinct positive gradient with distance from the Galactic center, following the relationship{sup 14}N/{sup 15}N = 21.1 (5.2) kpc{sup -1} D{sub GC} + 123.8 (37.1). This gradient is consistent with predictions of Galactic chemical evolution models in which {sup 15}N has a secondary origin in novae, while primary and secondary sources exist for {sup 14}N. The local interstellar medium value was found to be {sup 4}N/{sup 15}N = 290 {+-} 40, in agreement with the ratio found in nearby diffuse clouds and close to the value of 272 found in Earth's atmosphere.

  14. Effect of body size and body mass on ? 13 C and ? 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 ? 13C is independent of body size and that variation in ? 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 ? 13C and ? 15N variation in captivity. However, if sampling comprises a wide range of body sizes from various species, the variation of ? 13C and ? 15N with body size can be investigated. While correlation between body size and ? 13C and ? 15N can be due to ontogenetic diet shifts, stability in such values throughout the size spectrum can be considered an indication that ? 13C and ? 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 ? 13C and ? 15N with body size and body mass of coastal fishes and cephalopods. It was concluded that muscle ? 13C and ? 15N did not vary with body size or mass for all bony fishes with only one exception, the dragonet Callionymus lyra. Muscle ? 13C and ? 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 ? 13C or ? 15N, for most species analysed and within the size ranges sampled. The assumption that ? 13C is independent of body size and that variation in ? 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.

  15. Creating 13C- and 15N-enriched tree leaf litter for decomposition experiments

    NASA Astrophysics Data System (ADS)

    Szlavecz, K. A.; Pitz, S.; Chang, C.; Bernard, M.

    2013-12-01

    Labeling plant material with heavy isotopes of carbon and nitrogen can produce a traceable nutrient signal that can be followed into the different trophic levels and decomposer food web. We treated 60 tree saplings with 13C-enriched CO2 gas and 15N-enriched ammonium nitrate over a three-month period to create dually-labeled plant material for future decomposition experiments. The trees included both early (Red maple, Sweetgum, Tulip poplar) and late (American beech, White oak) successional deciduous tree species, and a conifer, White pine. We constructed a 2.4 m × 2.4 m × 2.4 m environmental chamber that was climate-controlled using an air conditioning system. An Arduino microcontroller interfaced with a Vaisala GMP343 CO2 probe maintained a CO2 concentration between 500-520 ppm by controlling a solenoid valve on the CO2 tank regulator. The trees were placed into the chamber in August 2012 and remained until senescence unless they were lost to death or disease. Ammonium nitrate was added twice, in September and October. Leaf samples were collected prior to the start of the experiment and after senescence, whereas root samples were collected only in December. Samples were dried, ground and analyzed using an isotope ratio mass spectrometer. American beech and White oak had 40% mortality, and 34% of tulip poplar trees were removed because of powdery mildew overgrowth or death. Most tulip poplar trees exhibited a second leaf out following senescence in late September. Nearly 1 kg of litter was produced with tulip poplar representing over half of the total mass. Levels of enrichment varied greatly by species. Beech (-14.2‰) and White oak (-4.8‰) had low levels of enrichment in comparison to early successional species such as Sweetgum (41.7‰) and Tulip poplar (30.7‰ [first leaf fall] and 238.0‰ [second leaf fall]). Leaf enrichment with 15N followed a similar pattern, though it was achieved at a higher level with ?15N values varying from 271.6‰ to 1354.2‰ at the end of the experiment. Enrichment of roots was significantly higher than leaves (?13C range: 111.5-219.2‰; ?15N range: 1516.9-3939.3‰) indicating that nutrients were translocated away from leaves prior to senescence, which is supported by the increase in C:N ratio between the initial (19.0) and final (60.1) leaf sampling. Despite the variable levels of enrichment, leaves from all species were sufficiently labeled for use in future studies aimed at tracking the transformation of carbon and nitrogen during decomposition. The greatest challenges were treating diseases and pests and creating ideal growing conditions for many species within the same chamber. Reducing the number of individuals and better pest management will lead to even higher level enrichment in the future.

  16. 1H, 13C, and 15N resonance assignments of murine amelogenin, an enamel biomineralization protein.

    SciTech Connect

    Buchko, Garry W.; Bekhazi, Jacky G.; Cort, John R.; Valentine, Nancy B.; Snead, Malcolm L.; Shaw, Wendy J.

    2008-06-01

    Amelogenin is the predominant matrix protein in developing dental enamel. Making extensive use of residue-specific 15N-labeled amino acids samples, the majority of the main and side chain resonances for murine amelogenin were assigned in 2% aqueous acetic acid at pH 3.0. This research was performed at Pacific Northwest National Laboratory, operated by Battelle for the US-DOE. A large part of this research was performed at the W.R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by U.S. Department of Energy’s Office of Biological and Environmental Research (BER) program located at Pacific Northwest National Laboratory (PNNL).

  17. Measurement of the neutron capture cross section of {sup 15}N J

    SciTech Connect

    MeiBner, N.J.; Schatz, H.; Herndl, H.; Wiescher, M.

    1995-10-01

    Neutron capture reactions on fight nuclei may be of considerable importance for the s-process nucleosynthesis in red giant stars as well as in inhomogeneous big bang scenarios and high entropy supernovae neutrino bubbles. To determine the reaction rates for such different temperature conditions, the cross sections need to be known for a wide energy range. The reaction {sup 15}N(n,{gamma}) represents an important link in the reaction seququences for the production of heavier isotopes in such scenarios. At high temperature conditions, the cross section is not only influenced by a non resonant a-wave contribution but also by a non resonant p-wave contribution and higher energy resonances. The (n,{gamma}) cross section has been measured at the Forschungszentrum Karlsruhe for different neutron energies using a fast cyclic neutron activation technique. The technique and the results will be presented.

  18. Memoirs of the Queensland Museum | Nature 2011 55(2) www.qm.qld.gov.au 451 Predator pressure, herbivore abundance and plant

    E-print Network

    , herbivore abundance and plant damage along a subtropical altitudinal gradient Darren BITO Environmental., Kitching, R.L. & Ødegaard, F. 2011 20 19: Predator pressure, herbivore abundance and plant damage along distribution of species, but also changes in trophic interactions. Studying changes in herbivory and herbivore

  19. Line lists for the A2PI-X2Sigma+ (red) and {B2Sigma+-X2Sigma} (violet) Systems of CN, 13C14N, and 12C15N, and Application to Astronomical Spectra

    E-print Network

    Sneden, Christopher; Ram, Ram S; Brooke, James S A; Bernath, Peter

    2014-01-01

    New red and violet system line lists for the CN isotopologues 13C14N and 12C15N have been generated. These new transition data are combined with those previously derived for 12C14N, and applied to the determination of CNO abundances in the solar photosphere and in four red giant stars: Arcturus, the bright very low-metallicity star HD 122563, and carbon-enhanced metal-poor stars HD 196944 and HD 201626. When lines of both red and violet system lines are detectable in a star, their derived N abundances are in good agreement. The mean N abundances determined in this work generally are also in accord with published values.

  20. Search for d3/2 single particle strength in 15N in Unbound Levels

    NASA Astrophysics Data System (ADS)

    Mertin, C. E.; Caussyn, D. D.; Crisp, A. M.; Keeley, N.; Kemper, K. W.; Momotyuk, O.; Roeder, B. T.; Volya, A.

    2013-10-01

    The population of states in the nucleus 15N provides the opportunity to investigate both single particle and cluster structures in the 1p and 2s1d shells. Single, two, three and four particle transfer reactions selectively excite states in 15N thus providing a way to explore current nuclear structure models. Narrow structures are observed in the various transfer reactions up to at least 20 MeV in excitation well above the neutron (10.8 MeV) and proton (10.2 MeV) separation energies. In the present work new results for the reaction 14N(d,p) are presented that explore possible single particle strengths up to 18 MeV in excitation. The beam energies used in the present work were between 10.5 and 16 MeV. An early work with a beam energy of 8 MeV clearly populated strong sharp levels at 10.07 and 11.23 MeV and the present work confirms their existence. In addition, very weak broader levels are populated at 12.13 and 12.5 MeV but no other structures are found experimentally at higher excitation energies. The results of shell model calculations that include the 1p and 2s1d shells will be presented. The centroid energies for the 1d5/2 and 2s1/2 single particle strength have been obtained through comparison with FRESCO calculations. This work was supported by the NSF, DOE and Florida State University.

  1. A pipeline for 15N metabolic labeling and phosphoproteome analysis in Arabidopsis thaliana.

    PubMed

    Minkoff, Benjamin B; Burch, Heather L; Sussman, Michael R

    2014-01-01

    Within the past two decades, the biological application of mass spectrometric technology has seen great advances in terms of innovations in hardware, software, and reagents. Concurrently, the burgeoning field of proteomics has followed closely (Yates et al., Annu Rev Biomed Eng 11:49-79, 2009)-and with it, importantly, the ability to globally assay altered levels of posttranslational modifications in response to a variety of stimuli. Though many posttranslational modifications have been described, a major focus of these efforts has been protein-level phosphorylation of serine, threonine, and tyrosine residues (Schreiber et al., Proteomics 8:4416-4432, 2008). The desire to examine changes across signal transduction cascades and networks in their entirety using a single mass spectrometric analysis accounts for this push-namely, preservation and enrichment of the transient yet informative phosphoryl side group. Analyzing global changes in phosphorylation allows inferences surrounding cascades/networks as a whole to be made. Towards this same end, much work has explored ways to permit quantitation and combine experimental samples such that more than one replicate or experimental condition can be identically processed and analyzed, cutting down on experimental and instrument variability, in addition to instrument run time. One such technique that has emerged is metabolic labeling (Gouw et al., Mol Cell Proteomics 9:11-24, 2010), wherein biological samples are labeled in living cells with nonradioactive heavy isotopes such as (15)N or (13)C. Since metabolic labeling in living organisms allows one to combine the material to be processed at the earliest possible step, before the tissue is homogenized, it provides a unique and excellent method for comparing experimental samples in a high-throughput, reproducible fashion with minimal technical variability. This chapter describes a pipeline used for labeling living Arabidopsis thaliana plants with nitrogen-15 ((15)N) and how this can be used, in conjunction with a technique for enrichment of phosphorylated peptides (phosphopeptides), to determine changes in A. thaliana's phosphoproteome on an untargeted, global scale. PMID:24057376

  2. Stable Carbon and Nitrogen isoscapes of the California Coast: integrated ?15N and ?13C of suspended particulate organic matter inferred from tissues of the California Mussel (mytilus californianus)

    NASA Astrophysics Data System (ADS)

    Vokhshoori, N. L.; McCarthy, M. D.

    2011-12-01

    Spatial maps of isotopic variability in a single species, or isoscapes, can characterize the natural variability in carbon (C) and nitrogen (N) isotope ratios across ecosystems on broad spatial scales, trace the signature of a source across a given area, as well as constrain animal migration patterns (Graham et al. 2002). In this study, isoscapes of stable carbon (13C) and nitrogen (15N) isotopes were constructed using intertidal mussels for northeast Pacific coastal waters of California. In this region biogeochemical cycling is primarily controlled by upwelling intensity and large-scale transport of the California Current System (CCS). We hypothesize that sampling specific tissues of filter-feeding organisms can provide an integrated measure of variation in 15N and 13C of the suspended particulate organic matter (POM) pool vs. latitude within the CCS, as well indicate main sources of both organic C and N to littoral food webs. California mussels (mytilus californianus) were collected from 28 sites between Coos Bay, OR and La Jolla, CA in the winter of 2009-2010 and summer of 2011, and adductor tissue was analyzed for ?13C and ?15N. Mussel size classes were chosen to provide ~ 1 yr integrated signal. Spatial trends in ?15N from the winter sampling show a strong linear trend in increasing ?15N values with latitude north to south (?15N values range from 7 % to 12%) consistent with slowly attenuating northward transport of 15N-depleted nitrate via California Undercurrent (Altabet et al. 1999). The ?13C values have no strong north to south correlation, but exhibit strong location-specific variability. The ?13C values range between -13 % and -18%. We propose the site-specific signature of ?13C indicates relative source of primary productin to POM at a given region (i.e. kelp, phytoplankton, zooplankton). Overall, these results suggest that isoscapes for filter-feeding organisms may offer a more accurate integrated picture of 15N and 13C values of POM than is possible from sediment traps or discrete time sampling of POM. The average latitudinal trends we observe may also be useful in interpreting stable isotopic values of higher trophic animals in the CA current system. Keywords: isoscape, California Current, stable isotope, geographic variation

  3. Abundance coefficients, a new method for measuring microorganism relative abundance

    USGS Publications Warehouse

    Forester, R.M.

    1977-01-01

    A new method of measuring the relative abundance of microorganisms by using a set of interrelated coefficients, termed 'abundance coefficients' or 'AC', is proposed. These coefficients provide a means of recording abundance for geometric density categories, and each density measurement represents an approximation of the Poisson parameter ??t. The AC is the natural logarithm of a 'characteristic value,' which is a particular number for each geometric density category. The 'characteristic values' are based upon a probabilistic error statement derived from the Poisson formula, and they present evidence for separation of the geometric category boundaries by e = 2.71828. The proposed AC provide a means for recording species abundance in a manner suitable for arithmetic manipulation, for population structure studies, and for the determination of practical limits for defining the presence or absence of a species. Further, these coefficients provide for both intrasample and intersample abundance comparisons. ?? 1977 Plenum Publishing Corporation.

  4. First Measurements of 15N Fractionation in N2H+ toward High-mass Star-forming Cores

    NASA Astrophysics Data System (ADS)

    Fontani, F.; Caselli, P.; Palau, A.; Bizzocchi, L.; Ceccarelli, C.

    2015-08-01

    We report on the first measurements of the isotopic ratio 14N/15N in N2H+ toward a statistically significant sample of high-mass star-forming cores. The sources belong to the three main evolutionary categories of the high-mass star formation process: high-mass starless cores, high-mass protostellar objects, and ultracompact H ii regions. Simultaneous measurements of the 14N/15N ratio in CN have been made. The 14N/15N ratios derived from N2H+ show a large spread (from ?180 up to ?1300), while those derived from CN are in between the value measured in the terrestrial atmosphere (?270) and that of the proto-solar nebula (?440) for the large majority of the sources within the errors. However, this different spread might be due to the fact that the sources detected in the N2H+ isotopologues are more than those detected in the CN ones. The 14N/15N ratio does not change significantly with the source evolutionary stage, which indicates that time seems to be irrelevant for the fractionation of nitrogen. We also find a possible anticorrelation between the 14N/15N (as derived from N2H+) and the H/D isotopic ratios. This suggests that 15N enrichment could not be linked to the parameters that cause D enrichment, in agreement with the prediction by recent chemical models. These models, however, are not able to reproduce the observed large spread in 14N/15N, pointing out that some important routes of nitrogen fractionation could be still missing in the models. Based on observations carried out with the IRAM-30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

  5. Studying ancient crop provenance: implications from ?(13)C and ?(15)N values of charred barley in a Middle Bronze Age silo at Ebla(NW Syria).

    PubMed

    Fiorentino, Girolamo; Caracuta, Valentina; Casiello, Grazia; Longobardi, Francesco; Sacco, Antonio

    2012-02-15

    The discovery of a storeroom full of barley and other cereals (L.9512) in the proto-historic site of Ebla has provided a unique opportunity to study the centralized storage system of the early city-state from a different perspective. Epigraphic evidence available within the site reveals a complex system of taxation which included gathering grain tributes from satellite sites and redistributing semi-finished products such as flour. In this paper, we intend to explore the possibilities of a combined approach to studying the storage system, based on estimated barley grain volumes and ?(13)C-?(15)N analyses. This approach is used to distinguish between grain from different harvesting sites and to identify any grain cultivated using special agricultural practices (e.g. manuring or irrigation). The basic assumption for this kind of analysis is that the growth-site conditions, natural or anthropogenic, of harvested cereals are reflected in their grain size and ?(13)C-?(15)N values. Since the remains found in the storeroom were charred, the first task was to evaluate the effect of carbonization on the ?(13)C-?(15)N and the size of the grains. Thus, the effect of charring was tested on modern samples of Syrian barley landraces. Once it had been ascertained that fresh grains reduced to charred remains retain their original biometric and isotopic traits, the ancient material was examined. Thirteen groups were identified, each characterized by a specific average volume and specific carbon and nitrogen values. The analysis revealed that what had first appeared to be a homogeneous concentration of grain was in fact an assemblage of barley harvested from different sites. PMID:22223320

  6. Analysis of the structure of synthetic and natural melanins by solid-phase

    SciTech Connect

    Duff, G.A.; Roberts, J.E.; Foster, N.

    1988-09-06

    The structures of one synthetic and two natural melanins are examined by solid-state NMR using cross polarization, magic angle sample spinning, and high-power proton decoupling. The structural features of synthetic dopa malanin are compared to those of melanin from malignant melanoma cells grown in culture and sepia melanin from squid ink. Natural abundance /sup 13/C and /sup 15/N spectra show resonances consistent with known pyrrolic and indolic structures within the heterogeneous biopolymer; /sup 13/C spectra indicate the presence of aliphatic residues in all three materials. These solid-phase experiments illustrate the promise of solid-phase NMR for elucidating structural from insoluble biomaterials.

  7. delta15N and delta13C diet-tissue discrimination factors for large sharks under semi-controlled conditions.

    PubMed

    Hussey, Nigel E; Brush, Jaclyn; McCarthy, Ian D; Fisk, Aaron T

    2010-04-01

    Stable isotopes (delta(15)N and delta(13)C) are being widely applied in ecological research but there has been a call for ecologists to determine species- and tissue-specific diet discrimination factors ((13)C and (15)N) for their study animals. For large sharks stable isotopes may provide an important tool to elucidate aspects of their ecological roles in marine systems, but laboratory based controlled feeding experiments are impractical. By utilizing commercial aquaria, we estimated (15)N and (13)C of muscle, liver, vertebral cartilage and a number of organs of three large sand tiger (Carcharias taurus) and one large lemon shark (Negaprion brevirostris) under a controlled feeding regime. For all sharks mean+/-SD for (15)N and (13)C in lipid extracted muscle using lipid extracted prey data were 2.29 per thousand+/-0.22 and 0.90 per thousand+/-0.33, respectively. The use of non-lipid extracted muscle and prey resulted in very similar (15)N and (13)C values but mixing of lipid and non-lipid extracted data produced variable estimates. Values of (15)N and (13)C in lipid extracted liver and prey were 1.50 per thousand+/-0.54 and 0.22 per thousand+/-1.18, respectively. Non-lipid extracted diet discrimination factors in liver were highly influenced by lipid content and studies that examine stable isotopes in shark liver, and likely any high lipid tissue, should strive to remove lipid effects through standardising C:N ratios, prior to isotope analysis. Mean vertebral cartilage (15)N and (13)C values were 1.45 per thousand+/-0.61 and 3.75 per thousand+/-0.44, respectively. Organ (15)N and (13)C values were more variable among individual sharks but heart tissue was consistently enriched by approximately 1-2.5 per thousand. Minimal variability in muscle and liver delta(15)N and delta(13)C sampled at different intervals along the length of individual sharks and between liver lobes suggests that stable isotope values are consistent within tissues of individual animals. To our knowledge, these are the first reported diet-tissue discrimination factors for large sharks under semi-controlled conditions, and are lower than those reported for teleost fish. PMID:19800980

  8. The effect of drought and interspecific interactions on the depth of water uptake in deep- and shallow-rooting grassland species as determined by ?18O natural abundance

    NASA Astrophysics Data System (ADS)

    Hoekstra, N. J.; Finn, J. A.; Lüscher, A.

    2014-03-01

    Increased incidence of weather drought, as predicted under climate change, has the potential to negatively affect grassland production. Compared to monocultures, vertical belowground niche complementarity between shallow- and deep-rooting species may be an important mechanism resulting in higher yields and higher resistance to drought in grassland mixtures. However, very little is known about the belowground responses in grassland systems and increased insight into these processes may yield important information both to predict the effect of future climate change and better design agricultural systems to cope with this. This study assessed the effect of a 10-week experimental summer drought on the depth of water uptake of two shallow-rooting species (Lolium perenne L. and Trifolium repens L.) and two deep-rooting species (Chicorium intybus L. and Trifolium pratense L.) in grassland monocultures and four-species-mixtures by using the natural abundance ?18O isotope method. We tested the following hypotheses: (1) drought results in a shift of water uptake to deeper soil layers, (2) deep-rooting species take up a higher proportion of water from deeper soil layers relative to shallow-rooting species, (3) as a result of interspecific interactions in mixtures, the water uptake of shallow-rooting species become shallower when grown together with deep-rooting species and vice versa, resulting in reduced niche overlap. The natural abundance ?18O technique provided novel insights into the depth of water uptake of deep- and shallow- rooting grassland species and revealed large shifts in response to drought and interspecific interactions. Compared to control conditions, drought reduced the proportional water uptake from 0-10 cm soil depth (PCWU0-10) of L. perenne, T. repens and C. intybus in monocultures by on average 54%. In contrast, the PCWU0-10 of T. pratense in monoculture increased by 44%, and only when grown in mixture did the PCWU0-10 of T. pratense decrease under drought conditions. In line with hypothesis 2, in monoculture, the PCWU0-10 of shallow-rooting species L. perenne and T. repens was 0.53 averaged over the two drought treatments, compared to 0.16 for the deep-rooting C. intybus. Surprisingly, in monoculture, water uptake by T. pratense was shallower than for the shallow-rooting species (PCWU0-10 = 0.68). Interspecific interactions in mixtures resulted in a shift in the depth of water uptake by the different species. As hypothesised, the shallow-rooting species L. perenne and T. repens tended to become shallower, and the deep-rooting T. pratense made a dramatic shift to deeper soil layers (reduction in PCWU0-10 of 58% on average) in mixture compared to monoculture. However, these shifts did not result in a reduction in the proportional similarity of the proportional water uptake from different soil depth intervals (niche overlap) in mixtures compared to monocultures. There was no clear link between interspecific differences in depth of water uptake and drought resistance. C. intybus, the species with water uptake from the deepest soil layers was one of the species most affected by drought. However, T. pratense, the species with the highest plasticity in depth of water uptake, was least affected by drought, suggesting an indirect effect of rooting depth on drought resistance. Our results show that niche complementarity in the depth of water uptake between shallow- and deep-rooting species may have contributed to the diversity effect in mixtures.

  9. The effect of drought and interspecific interactions on depth of water uptake in deep- and shallow-rooting grassland species as determined by ?18O natural abundance

    NASA Astrophysics Data System (ADS)

    Hoekstra, N. J.; Finn, J. A.; Hofer, D.; Lüscher, A.

    2014-08-01

    Increased incidence of drought, as predicted under climate change, has the potential to negatively affect grassland production. Compared to monocultures, vertical belowground niche complementarity between shallow- and deep-rooting species may be an important mechanism resulting in higher yields and higher resistance to drought in grassland mixtures. However, very little is known about the belowground responses in grassland systems and increased insight into these processes may yield important information both to predict the effect of future climate change and better design agricultural systems to cope with this. This study assessed the effect of a 9-week experimental summer drought on the depth of water uptake of two shallow-rooting species (Lolium perenne L. and Trifolium repens L.) and two deep-rooting species (Cichorium intybus L. and Trifolium pratense L.) in grassland monocultures and four-species mixtures by using the natural abundance ?18O isotope method. We tested the following three hypotheses: (1) drought results in a shift of water uptake to deeper soil layers, (2) deep-rooting species take up a higher proportion of water from deeper soil layers relative to shallow-rooting species, and (3) as a result of interspecific interactions in mixtures, the water uptake of shallow-rooting species becomes shallower when grown together with deep-rooting species and vice versa, resulting in reduced niche overlap. The natural abundance ?18O technique provided novel insights into the depth of water uptake of deep- and shallow- rooting grassland species and revealed large shifts in depth of water uptake in response to drought and interspecific interactions. Compared to control conditions, drought reduced the proportional water uptake from 0-10 cm soil depth (PCWU0-10) of L. perenne, T. repens and C. intybus in monocultures by on average 54%. In contrast, the PCWU0-10 of T. pratense in monoculture increased by 44%, and only when grown in mixture did the PCWU0-10 of T. pratense decrease under drought conditions. In line with hypothesis (2), in monoculture, the PCWU0-10 of shallow-rooting species L. perenne and T. repens was 0.53 averaged over the two drought treatments, compared to 0.16 for the deep-rooting C. intybus. Surprisingly, in monoculture, water uptake by T. pratense was shallower than for the shallow-rooting species (PCWU0-10 = 0.68). Interspecific interactions in mixtures resulted in a shift in the depth of water uptake by the different species. As hypothesised, the shallow-rooting species L. perenne and T. repens tended to become shallower, and the deep-rooting T. pratense made a dramatic shift to deeper soil layers (reduction in PCWU0-10 of 58% on average) in mixture compared to monoculture. However, these shifts did not result in a reduction in the proportional similarity of the proportional water uptake from different soil depth intervals (niche overlap) in mixtures compared to monocultures. There was no clear link between interspecific differences in depth of water uptake and the reduction of biomass production under drought compared to control conditions (drought resistance). Cichorium intybus, the species with water uptake from the deepest soil layers was one of the species most affected by drought. Interestingly, T. pratense, which was least affected by drought, also had the greatest plasticity in depth of water uptake. This suggests that there may be an indirect effect of rooting depth on drought resistance, as it determines the potential plasticity in the depth of water uptake.

  10. Non-lethal approach identifies variability of ?15N values in the fin rays of Atlantic Goliath Grouper, Epinephelus itajara

    PubMed Central

    Goddard, Ethan A.; Hollander, David J.; Koenig, Christopher C.; Stallings, Christopher D.

    2015-01-01

    The Atlantic Goliath Grouper, Epinephelus itajara, is critically endangered throughout its range but has begun to show initial signs of recovery in Florida state waters. As the population continues to rebound, researchers face a pressing need to fill the knowledge gaps about this iconic species. Here, we examined the ?15N isotopic records in fin rays collected from Atlantic Goliath Grouper, and related changes of isotopic ratios over time to life history characteristics. Fin-ray analysis was used as a non-lethal technique to sample individuals from two locations at similar latitudes from the west and east coasts of Florida, USA. ?15N data were acquired by mechanically separating the annuli of each fin ray and then analyzing the material in an Irradiance Elemental Analyzer Mass Spectrometer. The ?15N values were consistent among individuals within populations from each coast of Florida, and mirrored the expected changes over the lives of the fish. Overall, differences were found between ?15N values at juvenile life history phases versus adult phases, but the patterns associated with these differences were unique to each coastal group. We demonstrated, for the first time, that ?15N values from fin rays can be used to assess the life histories of Atlantic Goliath Grouper. The non-lethal strategies outlined here can be used to acquire information essential to the management of species of concern, such as those that are threatened or endangered. PMID:26082864

  11. High Resolution 13C MRI With Hyperpolarized Urea: In Vivo T2 Mapping and 15N Labeling Effects

    PubMed Central

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

    2014-01-01

    13C steady state free precession (SSFP) magnetic resonance imaging and effective spin-spin relaxation time (T2) mapping were performed using hyperpolarized [13C] urea and [13C, 15N2] urea injected intravenously in rats. 15N 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 [13C, 15N2] 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. [13C] 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 [13C, 15N2] 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 [13C, 15N2] urea giving a greater than four-fold increase in signal-to-noise ratio [13C] over urea. PMID:24235273

  12. Sources of nitrate in the Arno River waters: Constraints from d15N and d18O

    USGS Publications Warehouse

    Nisi, Barbara; Vaselli, Orlando; Buccianti, Antonella; Silva, Steven R.

    2005-01-01

    Running waters in anthropogenically affected areas are susceptible to nitrate contamination. Source identification is a fundamental step for the development of effective remediation. Previous studies pointed to pollution by nitrogen-bearing contaminants in the Arno Basin. In this paper, eleven surface water samples have been analysed for main and trace components and 15N/14N and 18O/16O ratios, with the aim of identifying for the first time the origin of nitrate in the Arno River Basin so that further investigations can appropriately be designed. d18O(NO3)and d15N(NO3) values have allowed to hypothesise the main sources of nitrate, as follows: i) mineralized fertilizer, ii) soil-organic nitrogen, iii) manure and septic waste. The anomalously high d15N and d18O values in the Chiana (d15N=24.9‰ and d18O=15.5‰) and Usciana tributaries (d15N=30.1‰ and d18O=7.2‰) show a low probability of belonging to the same population as that of the other samples and can be related to denitrification process of nitrate from animal waste/sewage and/or an industrial process (e.g. tanneries).

  13. Non-lethal approach identifies variability of ? (15)N values in the fin rays of Atlantic Goliath Grouper, Epinephelus itajara.

    PubMed

    Tzadik, Orian E; Goddard, Ethan A; Hollander, David J; Koenig, Christopher C; Stallings, Christopher D

    2015-01-01

    The Atlantic Goliath Grouper, Epinephelus itajara, is critically endangered throughout its range but has begun to show initial signs of recovery in Florida state waters. As the population continues to rebound, researchers face a pressing need to fill the knowledge gaps about this iconic species. Here, we examined the ? (15)N isotopic records in fin rays collected from Atlantic Goliath Grouper, and related changes of isotopic ratios over time to life history characteristics. Fin-ray analysis was used as a non-lethal technique to sample individuals from two locations at similar latitudes from the west and east coasts of Florida, USA. ? (15)N data were acquired by mechanically separating the annuli of each fin ray and then analyzing the material in an Irradiance Elemental Analyzer Mass Spectrometer. The ? (15)N values were consistent among individuals within populations from each coast of Florida, and mirrored the expected changes over the lives of the fish. Overall, differences were found between ? (15)N values at juvenile life history phases versus adult phases, but the patterns associated with these differences were unique to each coastal group. We demonstrated, for the first time, that ? (15)N values from fin rays can be used to assess the life histories of Atlantic Goliath Grouper. The non-lethal strategies outlined here can be used to acquire information essential to the management of species of concern, such as those that are threatened or endangered. PMID:26082864

  14. Late Holocene Plankton Domain Shifts in the North Pacific Subtropical Gyre Revealed by Amino Acid Specific ?13C and ?15N Records from Proteinaceous Deep-Sea Corals

    NASA Astrophysics Data System (ADS)

    Sherwood, O.; McMahon, K.; Guilderson, T. P.; Mccarthy, M. D.

    2014-12-01

    Recent observations from station ALOHA have framed a new paradigm about the dynamic nature of subtropical ocean gyres. These vast regions are now known to vary physically and biologically, over a range of timescales, with important implications for the export of carbon to the deep ocean. In the largest of these gyres, the North Pacific subtropical gyre (NPSG), primary production has increased in recent decades despite a reduction in nutrient supply to surface waters. This is thought to be the result of a shift in plankton community structure from mostly eukaryotes to mostly dinitrogen-fixing prokaryotes. It remains uncertain, however, whether the recent plankton community domain shift can be linked to cyclical climate variability or a long-term global warming trend. To establish historical trends, we analyzed nitrogen (?15N) and carbon (?13C) isotopic records preserved in the skeletons of extraordinarily long-lived, proteinaceous deep-sea corals, which feed on, and therefore serve as a proxy for, exported productivity. Specimens of Hawaiian gold coral (Kulamanamana haumeaae) were collected from the Hawaiian archipelago and sampled across the skeletal growth rings to generate high-resolution (5 yr), millennial-length records of "bulk" ?15N and ?13C. After a millennium of relatively minor fluctuation, ?15N decreased by up to 2 per mil between 1850 and the present. Analysis of amino-acid-specific ?15N on a subset of the samples, combined with isotopic mass balance between nitrate and nitrogen fixation, implied a 17 to 27 % increase in nitrogen fixation as the underlying cause for the observed trends. This interpretation is supported by analysis of the ?13C of essential amino acids, which serve as isotopic fingerprints of primary producer origin. Together, these independent lines of evidence describe a domain shift from a dominantly eukaryotic to dinitrogen-fixing prokaryotic plankton community. This shift has been ongoing since the end of the Little Ice Age, concurrent with increasing temperatures in the northern hemisphere, and most likely the result of increasing stratification and nutrient limitation in the NPSG. These results highlight the value of novel paleo-archives combined with amino-acid-specific isotope methods in addressing unresolved problems in marine biogeochemistry and climate change.

  15. Structural Dynamics of the Potassium Channel Blocker ShK: SRLS Analysis of (15)N Relaxation.

    PubMed

    Meirovitch, Eva; Tchaicheeyan, Oren; Sher, Inbal; Norton, Raymond S; Chill, Jordan H

    2015-12-10

    The 35-residue ShK peptide binds with high affinity to voltage-gated potassium channels. The dynamics of the binding surface was studied recently with (microsecond to millisecond) (15)N relaxation dispersion and (picosecond to nanosecond) (15)N spin relaxation of the N-H bonds. Relaxation dispersion revealed microsecond conformational-exchange-mediated exposure of the functionally important Y23 side chain to the peptide surface. The spin relaxation parameters acquired at 14.1 and 16.45 T have been subjected to model-free (MF) analysis, which yielded a squared generalized order parameter, S(2), of approximately 0.85 for virtually all of the N-H bonds. Only a "rigid backbone" evaluation could be inferred. We ascribe this limited information to the simplicity of MF in the context of challenging data. To improve the analysis, we apply the slowly relaxing local structure (SRLS) approach, which is a generalization of MF. SRLS describes N-H bond dynamics in ShK in terms of a local potential, u, ranging from 10 to 18.5 kBT, and a local diffusion rate, D2, ranging from 4.2 × 10(8) to 2.4 × 10(10) s(-1). This analysis shows that u is outstandingly strong for Y23 and relatively weak for K22, whereas D2 is slow for Y23 and fast for K22. These observations are relevant functionally because of the key role of the K22-Y23 dyad in ShK binding to potassium channels. The disulfide-bond network exhibits a medium-strength potential and an alternating wave-like D2 pattern. This is indicative of moderate structural restraints and motional plasticity, in support of, although not directly correlated with, the microsecond binding-related conformational exchange process detected previously. Thus, new information on functionally important residues in ShK and its overall conformational stability emerged from the SRLS analysis, as compared with the previous MF-based estimate of backbone dynamics as backbone rigidity. PMID:26551165

  16. Astrophysical S factor for the {sup 15}N(p,{gamma}){sup 16}O reaction

    SciTech Connect

    Mukhamedzhanov, A. M.; La Cognata, M.; Kroha, V.

    2011-04-15

    The R-matrix approach has proved to be very useful in extrapolating the astrophysical factor down to astrophysically relevant energies, since the majority of measurements are not available in this region. However, such an approach has to be critically considered when no complete knowledge of the reaction model is available. To get reliable results in such cases one has to use all the available information from independent sources and, accordingly, fix or constrain variations of the parameters. In this paper we present a thorough R-matrix analysis of the {sup 15}N(p,{gamma}){sup 16}O reaction, which provides a path from the CN cycle to the CNO bi-cycle and CNO tri-cycle. The measured astrophysical factor for this reaction is dominated by resonant capture through two strong J{sup {pi}}=1{sup -} resonances at E{sub R}=312 and 962 keV and direct capture to the ground state. Recently, a new measurement of the astrophysical factor for the {sup 15}N(p,{gamma}){sup 16}O reaction has been published [P. J. LeBlanc et al., Phys. Rev. C 82, 055804 (2010)]. The analysis has been done using the R-matrix approach with unconstrained variation of all parameters including the asymptotic normalization coefficient (ANC). The best fit has been obtained for the square of the ANC C{sup 2}=539.2 fm{sup -1}, which exceeds the previously measured value by a factor of {approx_equal}3. Here we present a new R-matrix analysis of the Notre Dame-LUNA data with the fixed within the experimental uncertainties square of the ANC C{sup 2}=200.34 fm{sup -1}. Rather than varying the ANC we add the contribution from a background resonance that effectively takes into account contributions from higher levels. Altogether we present ten fits, seven unconstrained and three constrained. For the unconstrained fit with the boundary condition B{sub c}=S{sub c}(E{sub 2}), where E{sub 2} is the energy of the second level, we get S(0)=39.0{+-}1.1 keVb and normalized {chi}-tilde{sup 2}=1.84, i.e., the result which is similar to LeBlanc et al. From all our fits we get the range 33.1{<=}S(0){<=}40.1 keVb which overlaps with the result of LeBlanc et al. We address also the physical interpretation of the fitting parameters.

  17. Potential probe for examining opiate-receptor interactions: model compound study of dynamic effects on /sup 15/N INEPT enhancements

    SciTech Connect

    Schilling, K.H.; Mikita, M.A.

    1987-10-01

    Model systems were chosen in an attempt to mimic the proton exchange environment of an agonist nitrogen in an opiate-receptor interaction. The two model systems studied were an ammonium: 18-crown-6 ether complex and a quinuclidine-trifluoroacetic acid ion pair. Each system was examined for their effects on /sup 15/N NMR INEPT enhancements. Both models were found to retard proton exchange dynamics, as observed by increased enhancements relative to free ions in neutral aqueous solutions. These results suggest that the confinement of a protonated nitrogen, such as that expected in receptor binding, may alter exchange dynamics to favor INEPT enhancements, while unbound agonists would remain unenhanced. As a result, /sup 15/N NMR INEPT enhancements from a solution of receptor subtypes with an appropriate /sup 15/N-labeled agonist may present a means of exploring the dynamics of direct opiate-receptor interactions.

  18. Nitrogen mineralization from selected /sup 15/N-labelled crop residues and humus as affected by inorganic nitrogen

    SciTech Connect

    Santos, J.A.

    1987-01-01

    The use of cover crops or crop residues as a source of N to succeeding crops has become a matter of increasing importance for economic and environmental reason. Greenhouse and field studies were conducted to determine the N contribution of four /sup 15/N labelled crop residues, rye (Secale cereale L.), wheat (Triticum aestivum L.), crimson clover (Trifolium encarnatum L.), and hairy vetch (Vicia sativa L.), to successive crops and to evaluate the effect of different organic (ON) and inorganic N (IN) combinations on mineralization of the above residues. Total /sup 15/N recovery from the residues ranged from 51% to 85% and 4% to 74% for the greenhouse and field studies, respectively.

  19. Influence of solar cycle and chemistry on tropical (10°N-15°N) mesopause variabilities

    NASA Astrophysics Data System (ADS)

    Ramesh, K.; Sridharan, S.; Vijaya Bhaskara Rao, S.

    2015-05-01

    Monthly averaged zonal mean temperature and ozone volume mixing ratios obtained from "Sounding of the Atmosphere using Broadband Emission Radiometry" instrument on board "Thermosphere Ionosphere Mesosphere Energetics and Dynamics" satellite for the years 2002-2012 are used to study the seasonal and solar cycle variabilities of tropical (10°N-15°N) mesopause structure. The mesopause temperature and ozone mixing ratios are positively correlated with solar cycle due to changes in CO2 and O, respectively. Although the seasonal variation in mesopause temperatures is quite small, the mesopause altitudes are comparatively higher (~99-100 km) in April and lower (~95 km) in September. The factors controlling the tropical mesopause structure are investigated by taking the mesopause variability for the year 2011 as a case study as it resembles the long-term mean seasonal variation. It is found that the radiative cooling due to 15 µm CO2 infrared emissions is the only cooling mechanism in the mesopause region. The net heating rates obtained from (i) solar heating by O2 and O3, (ii) chemical heating due to seven major exothermic reactions, (iii) O3 long-wave radiative heating, and (iv) CO2 cooling are smaller (~20 K/d) in April and larger (~85 K/d) in September at lower thermosphere (~99-101 km). The downward heat conduction from the lower thermosphere forces the mesopause to lower heights in September, although no downward heat conduction is observed in April.

  20. 15N solid-state NMR as a probe of flavin H-bonding.

    PubMed

    Cui, Dongtao; Koder, Ronald L; Dutton, P Leslie; Miller, Anne-Frances

    2011-06-23

    Flavins mediate a wide variety of chemical reactions in biology. To learn how one cofactor can be made to execute different reactions in different enzymes, we are developing solid-state NMR (SSNMR) to probe the flavin electronic structure, via the (15)N chemical shift tensor principal values (?(ii)). We find that SSNMR has superior responsiveness to H-bonds, compared to solution NMR. H-bonding to a model of the flavodoxin active site produced an increase of 10 ppm in the ?(11) of N5, although none of the H-bonds directly engage N5, and solution NMR detected only a 4 ppm increase in the isotropic chemical shift (?(iso)). Moreover SSNMR responded differently to different H-bonding environments, as H-bonding with water caused ?(11) to decrease by 6 ppm, whereas ?(iso) increased by less than 1 ppm. Our density functional theoretical (DFT) calculations reproduce the observations, validating the use of computed electronic structures to understand how H-bonds modulate the flavin's reactivity. PMID:21619002

  1. Amino acid composition and ?15N of suspended matter in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Gaye, B.; Nagel, B.; Dähnke, K.; Rixen, T.; Lahajnar, N.; Emeis, K.-C.

    2013-08-01

    Sedimentation in the ocean is fed by large aggregates produced in the surface mixed layer that sink rapidly through the water column. These particles sampled by sediment traps have often been proposed to interact by disaggregation and scavenging with a pool of fine suspended matter with very slow sinking velocities and thus a long residence time. We investigated the amino acid composition and stable nitrogen isotopic ratios of suspended matter sampled during the late SW monsoon season in the Arabian Sea and compared them to those of sinking particles to investigate organic matter degradation/modification during passage through the water column. We found that amino acid (AA) composition of mixed layer suspended matter corresponds more to fresh plankton and their aggregates, whereas AA composition of suspended matter in the sub-thermocline water column deviated progressively from mixed layer composition. We conclude that suspended matter in deep waters and in the mixed layers of oligotrophic stations is dominated by fine material that has a long residence time and organic matter that is resistant to degradation. Whereas SPM in areas of high primary productivity is essentially derived from fresh plankton and thus has a strong imprint of the subsurface nitrate source, SPM at oligotrophic stations and at subthermocline depths appears to exchange amino acids with the DOC pool influencing also the ?15N values.

  2. Ammonia 15N/14N Isotope Ratio in the Jovian Atmosphere

    NASA Technical Reports Server (NTRS)

    Mahaffy, P.R.; Niemann, H. B.; Atreya, S. K.; Wong, M. H.; Owen, T. C; Einaudi, Franco (Technical Monitor)

    2000-01-01

    Data from the Galileo Probe Mass Spectrometer has been used to derive the N-15/N-14 isotope ratio in ammonia at Jupiter. Although the mass spectral interference from the water contribution to 18 amu makes an accurate derivation of the (N-15)H3/(N-14)H3 ratio difficult from measurements of the singly ionized signals at 18 and 17 amu, this interference is not present in the doubly charged 8.5 and 9.0 amu signals from (N-14)H3++ and (N-15)H3++ respectively. Although the count rate from the 9 amu signal is low during the direct sampling of the atmosphere, the ammonia signal was considerably enhanced during the first enrichment cell (EC1) experiment that measured gas sampled between 0.8 and 2.8 bar. Count rates at 9 amu in the EC1 experiment reach 60/second and measure ammonia sampled from 0.88 to 2.8 bar. In the EC1 measurements the 8.5 amu signal is not measured directly, but can be calculated from the ammonia contribution to 17 amu and the ratio of NH3 ions of a double to single charged observed during a high resolution mass scan taken near the end of the descent. The high resolution scan gives this ratio from ammonia sampled much deeper in the atmosphere. These results are described and compared with Infrared Space Observatory-Short Wavelength Spectrometer (ISO-SWS) observations that give this ratio at 400 mbar.

  3. Mean lifetimes and equilibrium abundances in the fast CN cycle.

    NASA Technical Reports Server (NTRS)

    Caughlan, G. R.; Fowler, W. A.

    1972-01-01

    It is shown that the production of small nitrogen to carbon ratios is possible, in contrast to the equilibrium production in the ordinary CN cycle. Associated with such a production are high ratios of C-13/C-12 and of N-15/N-14. The final ratios depend on the conditions under which cessation of hydrogen burning occurs under astrophysical circumstances. A table showing proton capture mean lifetimes of CN nuclei is provided together with tables of the equilibrium abundances in a fast CN cycle. The ratios of final abundances of nitrogen to carbon as functions of temperature are also presented.

  4. Combined use of 15N and 18O of nitrate and 11B to evaluate nitrate contamination in groundwater

    USGS Publications Warehouse

    Seiler, R.L.

    2005-01-01

    Isotopic composition of NO3 (??15NNO3 and ??18ONO3) and B (??11B) were used to evaluate NO3 contamination and identify geochemical processes occurring in a hydrologically complex Basin and Range valley in northern Nevada with multiple potential sources of NO3. Combined use of these isotopes may be a useful tool in identifying NO3 sources because NO3 and B co-migrate in many environmental settings, their isotopes are fractionated by different environmental processes, and because wastewater and fertilizers may have distinct isotopic signatures for N and B. The principal cause of elevated NO3 concentrations in residential parts of the study area is wastewater and not natural NO3 or fertilizers. This is indicated by some samples with elevated NO3 concentrations plotting along ??15NNO3 and NO3 mixing lines between natural NO3 from the study area and theoretical septic-system effluent. This conclusion is supported by the presence of caffeine in one sample and the absence of samples with elevated NO3 concentrations that fall along mixing lines between natural NO3 and theoretical percolate below fertilized lawns. Nitrogen isotopes alone could not be used to determine NO3 sources in several wells because denitrification blurred the original isotopic signatures. The range of ??11B values in native ground water in the study area (-8.2??? to +21.2???) is large. The samples with the low ??11B values have a geochemical signature characteristic of hydrothermal systems. Physical and chemical data suggest B is not being strongly fractionated by adsorption onto clays. ??11B values from local STP effluent (-2.7???) and wash water from a domestic washing machine (-5.7???) were used to plot mixing lines between wastewater and native ground water. In general, wells with elevated NO3 concentrations fell along mixing lines between wastewater and background water on plots of ??11B against 1/B and Cl/B. Combined use of ??15N and ??11B in the study area was generally successful in identifying contaminant sources and processes that are occurring, however, it is likely to be more successful in simpler settings with a well-characterized ??11B value for background wells.

  5. Nitrogen isotope abundances in the recent solar wind.

    PubMed

    Kim, J S; Kim, Y; Marti, K; Kerridge, J F

    1995-06-01

    Although lunar crystalline rocks are essentially devoid of nitrogen, the same is not true of the lunar regolith. The nitrogen contents of individual regolith samples (which can be as high as 0.012% by mass) correlate strongly with abundances of noble gases known to be implanted in the lunar surface by solar radiation, indicating that lunar regolith nitrogen is also predominantly of solar origin. The large variability in 15N/14N ratios measured in different regolith samples may thus reflect long-term changes in the isotopic composition of the solar radiation. But attempts to explain these variations have been hampered by the lack of any firm constraint on 15N/14N in the present solar wind. Here we report measurements of nitrogen isotopes from two lunar samples that have had simple (and relatively recent) exposure histories. We find that nitrogen implanted in the lunar surface during the past 10(5) to 5 x 10(7) years has a 15N/14N ratio approximately 40% higher than that in the terrestrial atmosphere, which is substantially lower than most previous estimates. This isotopic signature probably represents the best measure of 15N/14N in the present-day solar wind. PMID:7760930

  6. 1H and 15N nuclear magnetic resonance assignment and secondary structure of the cytotoxic ribonuclease alpha-Sarcin.

    PubMed Central

    Campos-Olivas, R.; Bruix, M.; Santoro, J.; Martínez del Pozo, A.; Lacadena, J.; Gavilanes, J. G.; Rico, M.

    1996-01-01

    The ribosome-inactivating protein alpha-Sarcin (alpha S) is a 150-residue fungal ribonuclease that, after entering sensitive cells, selectively cleaves a single phosphodiester bond in an universally conserved sequence of the major rRNA to inactivate the ribosome and thus exert its cytotoxic action. As a first step toward establishing the structure-dynamics-function relationships in this system, we have carried out the assignment of the 1H and 15N NMR spectrum of alpha S on the basis of homonuclear (1H-1H) and heteronuclear (1H-15N) two-dimensional correlation spectra of a uniformly 15N-labeled sample, and two selectively 15N-labeled (Tyr and Phe) samples, as well as a single three-dimensional experiment. The secondary structure of alpha S, as derived from the characteristic patterns of dipolar connectivities between backbone protons, conformational chemical shifts, and the protection of backbone amide protons against exchange, consists of a long N-terminal beta-hairpin, a short alpha-helical segment, and a C-terminal beta-sheet of five short strands arranged in a + 1, + 1, + 1, + 1 topology, connected by long loops in which the 13 Pro residues are located. PMID:8732769

  7. Variation in hair ?13C and ?15N values in long-tailed macaques (Macaca fascicularis) from Singapore

    USGS Publications Warehouse

    Schillaci, Michael A.; Castellini, J. Margaret; Stricker, Craig A.; Jones-Engel, Lisa; Lee, Benjamin P.Y.-H.

    2014-01-01

    Much of the primatology literature on stable isotope ratios of carbon (?13C) and nitrogen (?15N) has focused on African and New World species, with comparatively little research published on Asian primates. Here we present hair ?13C and ?15N isotope values for a sample of 33 long-tailed macaques from Singapore. We evaluate the suggestion by a previous researcher that forest degradation and biodiversity loss in Singapore have led to a decline in macaque trophic level. The results of our analysis indicated significant spatial variability in ?13C but not ?15N. The range of variation in ?13C was consistent with a diet based on C3 resources, with one group exhibiting low values consistent with a closed canopy environment. Relative to other macaque species from Europe and Asia, the macaques from Singapore exhibited a low mean ?13C value but mid-range mean ?15N value. Previous research suggesting a decline in macaque trophic level is not supported by the results of our study.

  8. Contrasting food web linkages for the grazing pathway in 3 temperate forested streams using {sup 15}N as a tracer

    SciTech Connect

    Tank, J.L.; Mulholland, P.J.; Meyer, J.L.; Bowden, W.B.; Webster, J.R.; Peterson, B.J.

    1998-11-01

    Nitrogen is a critical element controlling the productivity and dynamics of stream ecosystems and many streams are limited by the supply of biologically available nitrogen. The authors are learning more about the fate of inorganic nitrogen entering streams through {sup 15}N tracer additions. The Lotic Intersite Nitrogen Experiment (LINX) is studying the uptake, cycling, and fate of {sup 15}N-NH{sub 4} in the stream food web of 10 streams draining different biomes. Using the {sup 15}N tracer method and data from 3 sites in the study, the authors can differentiate patterns in the cycling of nitrogen through the grazing pathway (N from the epilithon to grazing macroinvertebrates) for 3 temperate forested streams. Here, they quantify the relationship between the dominant grazer and its proposed food resource, the epilithon, by comparing {sup 15}N levels of grazers with those of the epilithon, as well as the biomass, nitrogen content, and chlorophyll a standing stocks of the epilithon in 3 streams.

  9. Improved determination of the astrophysical S(0) factor of the (15)N(p,alpha)(12)C reaction 

    E-print Network

    La Cognata, M.; Goldberg, V. Z.; Mukhamedzhanov, A. M.; Spitaleri, C.; Tribble, Robert E.

    2009-01-01

    COMMUNICATIONS PHYSICAL REVIEW C 80, 012801(R) (2009) Improved determination of the astrophysical S(0) factor of the 15N( p, ?)12C reaction M. La Cognata,1 V. Z. Goldberg,2 A. M. Mukhamedzhanov,2 C. Spitaleri,1,* and R. E. Tribble2 1DMFCI, Universita` di...

  10. Heteronuclear transverse and longitudinal relaxation in AX4 spin systems: Application to 15N relaxations in 15NH4+

    PubMed Central

    Werbeck, Nicolas D.; Hansen, D. Flemming

    2014-01-01

    The equations that describe the time-evolution of transverse and longitudinal 15N magnetisations in tetrahedral ammonium ions, 15NH4+, are derived from the Bloch-Wangsness-Redfield density operator relaxation theory. It is assumed that the relaxation of the spin-states is dominated by (1) the intra-molecular 15N–1H and 1H–1H dipole–dipole interactions and (2) interactions of the ammonium protons with remote spins, which also include the contribution to the relaxations that arise from the exchange of the ammonium protons with the bulk solvent. The dipole–dipole cross-correlated relaxation mechanisms between each of the 15N–1H and 1H–1H interactions are explicitly taken into account in the derivations. An application to 15N-ammonium bound to a 41 kDa domain of the protein DnaK is presented, where a comparison between experiments and simulations show that the ammonium ion rotates rapidly within its binding site with a local correlation time shorter than approximately 1 ns. The theoretical framework provided here forms the basis for further investigations of dynamics of AX4 spin systems, with ammonium ions in solution and bound to proteins of particular interest. PMID:25128779

  11. Plant community change mediates the response of foliar delta15N to CO2 enrichment in mesic grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rising atmospheric CO2 concentration may change the isotopic signature of plant N by altering plant and microbial processes involved in the N cycle. Isotope fractionation theory and limited experimental evidence indicate that CO2 may increase leaf delta15N by increasing plant community productivity,...

  12. First Experimental Measurement of the {sup 18}O(p,{alpha}){sup 15}N Reaction at Astrophysical Energies

    SciTech Connect

    La Cognata, M.; Sergi, M. L.; Spitaleri, C.; Cherubini, S.; Gulino, M.; Kiss, G.; Lamia, L.; Pizzone, R. G.; Romano, S.; Mukhamedzhanov, A.; Goldberg, V.; Tribble, R.; Coc, A.; Hammache, F.; Sereville, N. de; Tumino, A.

    2010-11-24

    The {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N reactions are of primary importance in several as-trophysical scenarios, including nucleosynthesis inside Asymptotic Giant Branch stars and oxygen and nitrogen isotopic ratios in meteorite grains. They are also key reactions to understand exotic systems such as R-Coronae Borealis stars and novae. Thus, the measurement of their cross sections in the low energy region can be crucial to reduce the nuclear uncertainty on theoretical predictions, because the resonance parameters are poorly determined. The Trojan Horse Method, in its newly developed form particularly suited to investigate low-energy resonances, has been applied to the {sup 2}H({sup 18}O,{alpha}{sup 15}N)n and {sup 2}H({sup 17}O,{alpha}{sup 14}N)n reactions to deduce the {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N cross sections at low energies. Resonances in the {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N excitation functions have been studied and the resonance parameters deduced.

  13. Variation in hair ?13C and ?15N values in long-tailed macaques (Macaca fascicularis) from Singapore

    PubMed Central

    Castellini, J. Margaret; Stricker, Craig A.; Jones-Engel, Lisa; Lee, Benjamin P.Y.-H.; O'Hara, Todd M.

    2015-01-01

    Much of the primatology literature on stable isotope ratios of carbon (?13C) and nitrogen (?15N) has focused on African and New World species, with comparatively little research published on Asian primates. Here we present hair ?13C and ?15N isotope values for a sample of 33 long-tailed macaques from Singapore. We evaluate the suggestion by a previous researcher that forest degradation and biodiversity loss in Singapore have led to a decline in macaque trophic level. The results of our analysis indicated significant spatial variability in ?13C but not ?15N. The range of variation in ?13C was consistent with a diet based on C3 resources, with one group exhibiting low values consistent with a closed canopy environment. Relative to other macaque species from Europe and Asia, the macaques from Singapore exhibited a low mean ?13C value but mid-range mean ?15N value. Previous research suggesting a decline in macaque trophic level is not supported by the results of our study. PMID:23729223

  14. Measurement of 13C-15N Distances in Uniformly 13C Labeled Biomolecules: J-Decoupled REDOR

    E-print Network

    Griffin, Robert G.

    Measurement of 13C-15N Distances in Uniformly 13C Labeled Biomolecules: J-Decoupled REDOR C. PVised Manuscript ReceiVed September 10, 1999 Measurement of distances between pairs of heteronuclei is important of the pos- sibility of measuring several distances in a single sample. However, in REDOR experiments

  15. Nitrate removal in stream ecosystems measured by 15N addition experiments: 2. Denitrification

    SciTech Connect

    Mulholland, Patrick J; Hall, Robert; Sobota, Daniel; Dodds, Walter; Findlay, Stuart; Grimm, Nancy; Hamilton, Stephen; McDowell, William; O'Brien, Jon; Tank, Jennifer; Ashkenas, Linda; Cooper, Lee W; Dahm, Cliff; Gregory, Stanley; Johnson, Sherri; Meyer, Judy; Peterson, Bruce; Poole, Geoff; Valett, H. Maurice; Webster, Jackson; Arango, Clay; Beaulieu, Jake; Bernot, Melody; Burgin, Amy; Crenshaw, Chelsea; Helton, Ashley; Johnson, Laura; Niederlehner, Bobbie; Potter, Jody; Sheibley, Rich; Thomas, Suzanne

    2009-01-01

    We measured denitrification rates using a field {sup 15}N-NO{sub 3}{sup -} tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (S{sub Wden}) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N{sub 2} production rates far exceeded N{sub 2}O production rates in all streams. The fraction of total NO{sub 3}{sup -} removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NH{sub 4}{sup +} concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling S{sub Wden} were specific discharge (discharge/width) and NO{sub 3}{sup -} concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (U{sub den}) and NO{sub 3}{sup -} concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although U{sub den} increased with increasing NO{sub 3}{sup -} concentration, the efficiency of NO{sub 3}{sup -} removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO{sub 3}{sup -} load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO{sub 3}{sup -} concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO{sub 3}{sup -} concentration.

  16. Nitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification

    USGS Publications Warehouse

    Mulholland, P.J.; Hall, R.O., Jr.; Sobota, D.J.; Dodds, W.K.; Findlay, S.E.G.; Grimm, N. B.; Hamilton, S.K.; McDowell, W.H.; O'Brien, J. M.; Tank, J.L.; Ashkenas, L.R.; Cooper, L.W.; Dahm, C. N.; Gregory, S.V.; Johnson, S.L.; Meyer, J.L.; Peterson, B.J.; Poole, G.C.; Valett, H.M.; Webster, J.R.; Arango, C.P.; Beaulieu, J.J.; Bernot, M.J.; Burgin, A.J.; Crenshaw, C.L.; Helton, A.M.; Johnson, L.T.; Niederlehner, B.R.; Potter, J.D.; Sheibley, R.W.; Thomasn, S.M.

    2009-01-01

    We measured denitrification rates using a field 15N-NO- 3 tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (SWden) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N2 production rates far exceeded N2O production rates in all streams. The fraction of total NO-3 removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NHz 4 concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling SWden were specific discharge (discharge / width) and NO-3 concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (Uden) and NO- 3 concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although Uden increased with increasing NO- 3 concentration, the efficiency of NO-3 removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO-3 load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO-3 concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO-3 concentration. ?? 2009.

  17. Proton-decoupled CPMG: A better experiment for measuring 15N R2 relaxation in disordered proteins

    NASA Astrophysics Data System (ADS)

    Yuwen, Tairan; Skrynnikov, Nikolai R.

    2014-04-01

    15N R2 relaxation is one of the most informative experiments for characterization of intrinsically disordered proteins (IDPs). Small changes in nitrogen R2 rates are often used to determine how IDPs respond to various biologically relevant perturbations such as point mutations, posttranslational modifications and weak ligand interactions. However collecting high-quality 15N relaxation data can be difficult. Of necessity, the samples of IDPs are often prepared with low protein concentration and the measurement time can be limited because of rapid sample degradation. Furthermore, due to hardware limitations standard experiments such as 15N spin-lock and CPMG can sample the relaxation decay only to ca. 150 ms. This is much shorter than 15N T2 times in disordered proteins at or near physiological temperature. As a result, the sampling of relaxation decay profiles in these experiments is suboptimal, which further lowers the precision of the measurements. Here we report a new implementation of the proton-decoupled (PD) CPMG experiment which allows one to sample 15N R2 relaxation decay up to ca. 0.5-1 s. The new experiment has been validated through comparison with the well-established spin-lock measurement. Using dilute samples of denatured ubiquitin, we have demonstrated that PD-CPMG produces up to 3-fold improvement in the precision of the data. It is expected that for intrinsically disordered proteins the gains may be even more substantial. We have also shown that this sequence has a number of favorable properties: (i) the spectra are recorded with narrow linewidth in nitrogen dimension; (ii) 15N offset correction is small and easy to calculate; (iii) the experiment is immune to various spurious effects arising from solvent exchange; (iv) the results are stable with respect to pulse miscalibration and rf field inhomogeneity; (v) with minimal change, the pulse sequence can also be used to measure R2 relaxation of 15N? spins in arginine side chains. We anticipate that the new experiment will be a valuable addition to the NMR toolbox for studies of IDPs.

  18. Simple approach for the preparation of 15?15N2-enriched water for nitrogen fixation assessments: evaluation, application and recommendations

    PubMed Central

    Klawonn, Isabell; Lavik, Gaute; Böning, Philipp; Marchant, Hannah K.; Dekaezemacker, Julien; Mohr, Wiebke; Ploug, Helle

    2015-01-01

    Recent findings revealed that the commonly used 15N2 tracer assay for the determination of dinitrogen (N2) fixation can underestimate the activity of aquatic N2-fixing organisms. Therefore, a modification to the method using pre-prepared 15?15N2-enriched water was proposed. Here, we present a rigorous assessment and outline a simple procedure for the preparation of 15?15N2-enriched water. We recommend to fill sterile-filtered water into serum bottles and to add 15?15N2 gas to the water in amounts exceeding the standard N2 solubility, followed by vigorous agitation (vortex mixing ? 5 min). Optionally, water can be degassed at low-pressure (?950 mbar) for 10 min prior to the 15?15N2 gas addition to indirectly enhance the 15?15N2 concentration. This preparation of 15?15N2-enriched water can be done within 1 h using standard laboratory equipment. The final 15N-atom% excess was 5% after replacing 2–5% of the incubation volume with 15?15N2-enriched water. Notably, the addition of 15?15N2-enriched water can alter levels of trace elements in the incubation water due to the contact of 15?15N2-enriched water with glass, plastic and rubber ware. In our tests, levels of trace elements (Fe, P, Mn, Mo, Cu, Zn) increased by up to 0.1 nmol L?1 in the final incubation volume, which may bias rate measurements in regions where N2 fixation is limited by trace elements. For these regions, we tested an alternative way to enrich water with 15?15N2. The 15?15N2 was injected as a bubble directly to the incubation water, followed by gentle shaking. Immediately thereafter, the bubble was replaced with water to stop the 15?15N2 equilibration. This approach achieved a 15N-atom% excess of 6.6 ± 1.7% when adding 2 mL 15?15N2 per liter of incubation water. The herein presented methodological tests offer guidelines for the 15N2 tracer assay and thus, are crucial to circumvent methodological draw-backs for future N2 fixation assessments. PMID:26300853

  19. Simple approach for the preparation of (15-15)N2-enriched water for nitrogen fixation assessments: evaluation, application and recommendations.

    PubMed

    Klawonn, Isabell; Lavik, Gaute; Böning, Philipp; Marchant, Hannah K; Dekaezemacker, Julien; Mohr, Wiebke; Ploug, Helle

    2015-01-01

    Recent findings revealed that the commonly used (15)N2 tracer assay for the determination of dinitrogen (N2) fixation can underestimate the activity of aquatic N2-fixing organisms. Therefore, a modification to the method using pre-prepared (15-15)N2-enriched water was proposed. Here, we present a rigorous assessment and outline a simple procedure for the preparation of (15-15)N2-enriched water. We recommend to fill sterile-filtered water into serum bottles and to add (15-15)N2 gas to the water in amounts exceeding the standard N2 solubility, followed by vigorous agitation (vortex mixing ? 5 min). Optionally, water can be degassed at low-pressure (?950 mbar) for 10 min prior to the (15-15)N2 gas addition to indirectly enhance the (15-15)N2 concentration. This preparation of (15-15)N2-enriched water can be done within 1 h using standard laboratory equipment. The final (15)N-atom% excess was 5% after replacing 2-5% of the incubation volume with (15-15)N2-enriched water. Notably, the addition of (15-15)N2-enriched water can alter levels of trace elements in the incubation water due to the contact of (15-15)N2-enriched water with glass, plastic and rubber ware. In our tests, levels of trace elements (Fe, P, Mn, Mo, Cu, Zn) increased by up to 0.1 nmol L(-1) in the final incubation volume, which may bias rate measurements in regions where N2 fixation is limited by trace elements. For these regions, we tested an alternative way to enrich water with (15-15)N2. The (15-15)N2 was injected as a bubble directly to the incubation water, followed by gentle shaking. Immediately thereafter, the bubble was replaced with water to stop the (15-15)N2 equilibration. This approach achieved a (15)N-atom% excess of 6.6 ± 1.7% when adding 2 mL (15-15)N2 per liter of incubation water. The herein presented methodological tests offer guidelines for the (15)N2 tracer assay and thus, are crucial to circumvent methodological draw-backs for future N2 fixation assessments. PMID:26300853

  20. Retrospective characterization of ontogenetic shifts in killer whale diets via ?13C and ?15N analysis of teeth

    USGS Publications Warehouse

    Newsome, Seth D.; Etnier, Michael A.; Monson, Daniel H.; Fogel, Marilyn L.

    2009-01-01

    Metabolically inert, accretionary structures such as the dentin growth layers in teeth provide a life history record of individual diet with near-annual resolution. We constructed ontogenetic ?13C and ?15N profiles by analyzing tooth dentin growth layers from 13 individual killer whales Orcinus orca collected in the eastern northeast Pacific Ocean between 1961 and 2003. The individuals sampled were 6 to 52 yr old, representing 2 ecotypes—resident and transient—collected across ~25° of latitude. The average isotopic values of transient individuals (n = 10) are consistent with a reliance on mammalian prey, while the average isotopic values of residents (n = 3) are consistent with piscivory. Regardless of ecotype, most individuals show a decrease in ?15N values of ~2.5‰ through the first 3 yr of life, roughly equivalent to a decrease of one trophic level. We interpret this as evidence of gradual weaning, after which, ontogenetic shifts in isotopic values are highly variable. A few individuals (n = 2) maintained relatively stable ?15N and ?13C values throughout the remainder of their lives, whereas ?15N values of most (n = 11) increased by ~1.5‰, suggestive of an ontogenetic increase in trophic level. Significant differences in mean ?13C and ?15N values among transients collected off California suggest that individuality in prey preferences may be prevalent within this ecotype. Our approach provides retrospective individual life history and dietary information that cannot be obtained through traditional field observations of free-ranging and elusive species such as killer whales, including unique historic ecological information that pre-dates modern studies. By providing insights into individual diet composition, stable isotope analysis of teeth and/or bones may be the only means of evaluating a number of hypothesized historical dietary shifts in killer whales of the northeast Pacific Ocean

  1. Retrospective characterization of ontogenetic shifts in killer whale diets via ?13C and ?15N analysis of teeth

    USGS Publications Warehouse

    Newsome, Seth D.; Etnier, Michael A.; Monson, Daniel H.; Fogel, Marilyn L.

    2009-01-01

    Metabolically inert, accretionary structures such as the dentin growth layers in teeth provide a life history record of individual diet with near-annual resolution. We constructed ontogenetic ??13C and ??15N profiles by analyzing tooth dentin growth layers from 13 individual killer whales Orcinus orca collected in the eastern northeast Pacific Ocean between 1961 and 2003. The individuals sampled were 6 to 52 yr old, representing 2 ecotypes-resident and transient - collected across ???25?? of latitude. The average isotopic values of transient individuals (n = 10) are consistent with a reliance on mammalian prey, while the average isotopic values of residents (n = 3) are consistent with piscivory. Regardless of ecotype, most individuals show a decrease in ??15N values of ???2.5% through the first 3 yr of life, roughly equivalent to a decrease of one trophic level. We interpret this as evidence of gradual weaning, after which, ontogenetic shifts in isotopic values are highly variable. A few individuals (n = 2) maintained relatively stable ??15N and ??13C values throughout the remainder of their lives, whereas ??15N values of most (n = 11) increased by ???1.5%, suggestive of an ontogenetic increase in trophic level. Significant differences in mean ??13C and ??15N values among transients collected off California suggest that individuality in prey preferences may be prevalent within this ecotype. Our approach provides retrospective individual life history and dietary information that cannot be obtained through traditional field observations of free-ranging and elusive species such as killer whales, including unique historic ecological information that pre-dates modern studies. By providing insights into individual diet composition, stable isotope analysis of teeth and/or bones may be the only means of evaluating a number of hypothesized historical dietary shifts in killer whales of the northeast Pacific Ocean. ?? Inter-Research 2009.

  2. Stable isotope tracking of endangered sea turtles: validation with satellite telemetry and ?15N analysis of amino acids.

    PubMed

    Seminoff, Jeffrey A; Benson, Scott R; Arthur, Karen E; Eguchi, Tomoharu; Dutton, Peter H; Tapilatu, Ricardo F; Popp, Brian N

    2012-01-01

    Effective conservation strategies for highly migratory species must incorporate information about long-distance movements and locations of high-use foraging areas. However, the inherent challenges of directly monitoring these factors call for creative research approaches and innovative application of existing tools. Highly migratory marine species, such as marine turtles, regularly travel hundreds or thousands of kilometers between breeding and feeding areas, but identification of migratory routes and habitat use patterns remains elusive. Here we use satellite telemetry in combination with compound-specific isotope analysis of amino acids to confirm that insights from bulk tissue stable isotope analysis can reveal divergent migratory strategies and within-population segregation of foraging groups of critically endangered leatherback sea turtles (Dermochelys coriacea) across the Pacific Ocean. Among the 78 turtles studied, we found a distinct dichotomy in ?(15)N values of bulk skin, with distinct "low ?(15)N" and "high ?(15)N" groups. ?(15)N analysis of amino acids confirmed that this disparity resulted from isotopic differences at the base of the food chain and not from differences in trophic position between the two groups. Satellite tracking of 13 individuals indicated that their bulk skin ?(15)N value was linked to the particular foraging region of each turtle. These findings confirm that prevailing marine isoscapes of foraging areas can be reflected in the isotopic compositions of marine turtle body tissues sampled at nesting beaches. We use a Bayesian mixture model to show that between 82 and 100% of the 78 skin-sampled turtles could be assigned with confidence to either the eastern Pacific or western Pacific, with 33 to 66% of all turtles foraging in the eastern Pacific. Our forensic approach validates the use of stable isotopes to depict leatherback turtle movements over broad spatial ranges and is timely for establishing wise conservation efforts in light of this species' imminent risk of extinction in the Pacific. PMID:22666354

  3. Measurement of (1)H-(15)N and (1)H-(13)C residual dipolar couplings in nucleic acids from TROSY intensities.

    PubMed

    Ying, Jinfa; Wang, Jinbu; Grishaev, Alex; Yu, Ping; Wang, Yun-Xing; Bax, Ad

    2011-09-01

    Analogous to the recently introduced ARTSY method for measurement of one-bond (1)H-(15)N residual dipolar couplings (RDCs) in large perdeuterated proteins, we introduce methods for measurement of base (13)C-(1)H and (15)N-(1)H RDCs in protonated nucleic acids. Measurements are based on quantitative analysis of intensities in (1)H-(15)N and (13)C-(1)H TROSY-HSQC spectra, and are illustrated for a 71-nucleotide adenine riboswitch. Results compare favorably with those of conventional frequency-based measurements in terms of completeness and convenience of use. The ARTSY method derives the size of the coupling from the ratio of intensities observed in two TROSY-HSQC spectra recorded with different dephasing delays, thereby minimizing potential resonance overlap problems. Precision of the RDC measurements is limited by the signal-to-noise ratio, S/N, achievable in the 2D TROSY-HSQC reference spectrum, and is approximately given by 30/(S/N) Hz for (15)N-(1)H and 65/(S/N) Hz for (13)C-(1)H. The signal-to-noise ratio of both (1)H-(15)N and (1)H-(13)C spectra greatly benefits when water magnetization during the experiments is not perturbed, such that rapid magnetization transfer from bulk water to the nucleic acid, mediated by rapid amino and hydroxyl hydrogen exchange coupled with (1)H-(1)H NOE transfer, allows for fast repetition of the experiment. RDCs in the mutated helix 1 of the riboswitch are compatible with nucleotide-specifically modeled, idealized A-form geometry and a static orientation relative to the helix 2/3 pair, which differs by ca 6° relative to the X-ray structure of the native riboswitch. PMID:21947918

  4. Stable Isotope Tracking of Endangered Sea Turtles: Validation with Satellite Telemetry and ?15N Analysis of Amino Acids

    PubMed Central

    Seminoff, Jeffrey A.; Benson, Scott R.; Arthur, Karen E.; Eguchi, Tomoharu; Dutton, Peter H.; Tapilatu, Ricardo F.; Popp, Brian N.

    2012-01-01

    Effective conservation strategies for highly migratory species must incorporate information about long-distance movements and locations of high-use foraging areas. However, the inherent challenges of directly monitoring these factors call for creative research approaches and innovative application of existing tools. Highly migratory marine species, such as marine turtles, regularly travel hundreds or thousands of kilometers between breeding and feeding areas, but identification of migratory routes and habitat use patterns remains elusive. Here we use satellite telemetry in combination with compound-specific isotope analysis of amino acids to confirm that insights from bulk tissue stable isotope analysis can reveal divergent migratory strategies and within-population segregation of foraging groups of critically endangered leatherback sea turtles (Dermochelys coriacea) across the Pacific Ocean. Among the 78 turtles studied, we found a distinct dichotomy in ?15N values of bulk skin, with distinct “low ?15N” and “high ?15N” groups. ?15N analysis of amino acids confirmed that this disparity resulted from isotopic differences at the base of the food chain and not from differences in trophic position between the two groups. Satellite tracking of 13 individuals indicated that their bulk skin ?15N value was linked to the particular foraging region of each turtle. These findings confirm that prevailing marine isoscapes of foraging areas can be reflected in the isotopic compositions of marine turtle body tissues sampled at nesting beaches. We use a Bayesian mixture model to show that between 82 and 100% of the 78 skin-sampled turtles could be assigned with confidence to either the eastern Pacific or western Pacific, with 33 to 66% of all turtles foraging in the eastern Pacific. Our forensic approach validates the use of stable isotopes to depict leatherback turtle movements over broad spatial ranges and is timely for establishing wise conservation efforts in light of this species’ imminent risk of extinction in the Pacific. PMID:22666354

  5. ?-Hole bonding in 15N-labeled N-Benzyl- N-(4-iodo-tetrafluorobenzyl)-amine: Synthesis, crystal structure and solid-state structure calculations

    NASA Astrophysics Data System (ADS)

    Raouafi, Noureddine; Mayer, Peter; Boujlel, Khaled; Schöllhorn, Bernd

    2011-03-01

    Reductive amination of 4-iodo-tetrafluorobenzaldehyde 2 and 15N-enriched benzylamine yielded the title compound 1. Single crystal X-ray diffraction (XRD) revealed that the product crystallizes in the triclinic system of the P-1 space group. The structure is consisting of infinite one-dimensional chair like chains, based on intermolecular N···I halogen bonding. Only intermolecular weak hydrogen bonds N sbnd H···F and C sbnd H···F are observed. Representative XRD data have been compared to the results of theoretical semi-empirical calculations in the solid-state obtained using the PM6 method. Charges of I, N and F atoms are calculated from Natural Bond Orbital (NBO) and Electrostatic Potential Surface maps have been estimated by applying second-order Møller-Plesset (MP2) perturbation theory, and confirmed clearly the assumption of ?-hole bonding formation.

  6. Robust Abundance Estimation in Animal Abundance Surveys with Imperfect Detection

    EPA Science Inventory

    Surveys of animal abundance are central to the conservation and management of living natural resources. However, detection uncertainty complicates the sampling process of many species. One sampling method employed to deal with this problem is depletion (or removal) surveys in whi...

  7. Simultaneous Occurrences of Denitrification and DNRA in Groundwaters: An In Situ 15N Tracer Study

    NASA Astrophysics Data System (ADS)

    Jahangir, M. M.; Johnston, P.; Khalil, M. I.; Groffman, P. M.; Richards, K. G.

    2011-12-01

    Understanding nitrogen (N) transformations in groundwater ecosystems is important for the management of N in agricultural systems and to mitigate the effects of reactive N on the environment. In situ groundwater denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were determined at three depths: subsoil (grassland only), bedrock-interface and bedrock (5, 12 and 20 m below ground level, bgl) in intensively managed grassland and arable farming systems. The grassland site had poorly drained soil overlying Ordovician sediments of sandstones and shales. The arable (spring barley) had well drained soil overlying limestone. Denitrification rates were quantified directly using the 15N-enriched nitrate "push-pull" method. Mean (±SE) denitrification rates were significantly higher (p<0.05) in JC (163±153 ?g kg-1 d-1) than in OP (3.9±2.0 ?g kg-1 d-1). In situ denitrification rates were consistently higher at bedrock-interface than in subsoil and bedrock (p>0.05) where the later two were similar. This indicates that denitrification processes are not limited to shallow groundwater rather it is an important process in shallow to deeper groundwaters along groundwater flow paths. In situ N2O/N2O+N2 ratios were significantly higher in OP (0.18±0.02) than in JC (0.08±0.02). Mean (±SE) DNRA rates in JC (3.5±2.3 ?g N kg-1 d-1) were significantly higher (p<0.05) than in OP (2.4±2.1 ?g N kg-1 d-1) and rates were higher at bedrock-interface than in subsoil and bedrock. Total nitrate losses via denitrification plus DNRA were 25 and 0.5% of the injected nitrate, respectively in JC and OP, where contribution of DNRA was low. Poorly drained top and subsoils can create favourable conditions (low dissolved oxygen/redox potential and longer residence time) in groundwater to convert nitrate to benign N2 and NH4+. Conversely, high N input on free draining sites with high dissolved oxygen and redox potential, groundwater can be vulnerable to nitrate contamination and indirect N2O emissions. The contrasting rates of denitrification and DNRA between sites suggest that it can be an important sink for nitrate in some sites, but not in others, depending on hydrogeologic conditions. The strong variation with hydrogeologic conditions suggests that we should be able to spatially predict sites with significant subsurface denitrification capacity.

  8. Comparison of three 15N methods to correct for microbial contamination when assessing in situ protein degradability of fresh forages.

    PubMed

    Kamoun, M; Ammar, H; Théwis, A; Beckers, Y; France, J; López, S

    2014-11-01

    The use of stable (15)N as a marker to determine microbial contamination in nylon bag incubation residues to estimate protein degradability was investigated. Three methods using (15)N were compared: (15)N-labeled forage (dilution method, LF), (15)N enrichment of rumen solids-associated bacteria (SAB), and (15)N enrichment of rumen liquid-associated bacteria (LAB). Herbage from forages differing in protein and fiber contents (early-cut Italian ryegrass, late-cut Italian ryegrass, and red clover) were freeze-dried and ground and then incubated in situ in the rumen of 3 steers for 3, 6, 12, 24, and 48 h using the nylon bag technique. The (15)N-labeled forages were obtained by fertilizing the plots where herbage was grown with (15)NH4 (15)NO3. Unlabeled forages (obtained from plots fertilized with NH4NO3) were incubated at the same time that ((15)NH4)2SO4 was continuously infused into the rumen of the steers, and then pellets of labeled SAB and LAB were isolated by differential centrifugation of samples of ruminal contents. The proportion of bacterial N in the incubation residues increased from 0.09 and 0.45 g bacterial N/g total N at 3 h of incubation to 0.37 and 0.85 g bacterial N/g total N at 48 h of incubation for early-cut and late-cut ryegrass, respectively. There were differences (P < 0.001) between uncorrected N degradability values and those corrected for microbial contamination with all of the methods. Apparent N degradability of the low-N, high-fiber forage (late-cut ryegrass) was 0.51, whereas the corrected values were 0.85, 0.84, and 0.77 for the LF, SAB, and LAB methods, respectively. With early-cut ryegrass and red clover, the differences between uncorrected and corrected values ranged between 6% and 13%, with small differences among the labeling methods. Generally, methods using labeled forage or labeled SAB and LAB provided similar corrected degradability values. The accuracy in estimating the extent of degradation of protein in the rumen from in situ disappearance curves is improved when values are corrected for microbial contamination of the bag residue. PMID:25349353

  9. Backbone dynamics of free barnase and its complex with barstar determined by 15N NMR relaxation study.

    PubMed

    Sahu, S C; Bhuyan, A K; Udgaonkar, J B; Hosur, R V

    2000-10-01

    Backbone dynamics of uniformly 15N-labeled free barnase and its complex with unlabelled barstar have been studied at 40 degrees C, pH 6.6, using 15N relaxation data obtained from proton-detected 2D [1H]-15N NMR spectroscopy. 15N spin-lattice relaxation rate constants (R1), spin-spin relaxation rate constants (R2), and steady-state heteronuclear [1H]-15N NOEs have been measured at a magnetic field strength of 14.1 Tesla for 91 residues of free barnase and for 90 residues out of a total of 106 in the complex (excluding three prolines and the N-terminal residue) backbone amide 15N sites of barnase. The primary relaxation data for both the cases have been analyzed in the framework of the model-free formalism using both isotropic and axially symmetric models of the rotational diffusion tensor. As per the latter, the overall rotational correlation times (tau(m)) are 5.0 and 9.5 ns for the free and complexed barnase, respectively. The average order parameter is found to be 0.80 for free barnase and 0.86 for the complex. However, the changes are not uniform along the backbone and for about 5 residues near the binding interface there is actually a significant decrease in the order parameters on complex formation. These residues are not involved in the actual binding. For the residues where the order parameter increases, the magnitudes vary significantly. It is observed that the complex has much less internal mobility, compared to free barnase. From the changes in the order parameters, the entropic contribution of NH bond vector motion to the free energy of complex formation has been calculated. It is apparent that these motion's cause significant unfavorable contributions and therefore must be compensated by many other favorable contributions to effect tight complex formation. The observed variations in the motion and their different locations with regard to the binding interface may have important implications for remote effects and regulation of the enzyme action. PMID:11101215

  10. Shifts in Ross Sea food web structure as indicated by ?15N and ?13C values of fossil Antarctic seals

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    As climate change continues to mount, there is a growing need for understanding its effects on biological-physical interactions of marine ecosystems. Assessing the effects of anthropogenic activities on the coastal marine ecosystem involves understanding the underlying mechanisms driving these changes as well as establishing baselines of the natural system. Preliminary findings have indicated shifts in bulk carbon (C) and nitrogen (N) isotopic values of southern elephant seal (Mirounga leonina) samples, collected in the Dry Valleys of Antarctica in the Ross Sea region, over approximately the last 7,000 years. These shifts could result from 1) seals changing their foraging location and/or diet over this time, 2) climate change-induced shifts in the biogeochemistry at the base of the food web, or 3) some combination of both processes. We explored the patterns of long-term change in Ross Sea food web structure by examining the stable isotope values of three top predators in this system, Weddell seals (Leptonychotes weddellii), leopard seals (Hydrurga leptonyx), and crabeater seals (Lobodon carcinophagus). Fossil seal samples were collected in the Dry Valleys during the austral summer of 2012/13 and then analyzed for bulk C and N isotopes via an elemental analyzer/isotope-ratio mass spectrometer (EA/IRMS). Our initial findings indicate that C isotopic values of fossil seal samples from Weddell, leopard, and crabeater seals were more enriched than isotopic values of modern seals of the same species (e.g., ?13C = -22.79 × 0.92 ‰ and -26.71 × 0.50 ‰ for fossil and modern crabeater seals, respectively). Given the relatively consistent diet of crabeater seals, these findings suggest a shift in baseline food web structure occurred over the last 10,000 years, either through changes in foraging location or local shifts in biogeochemistry. For all species, N isotopic values are widely variable (e.g., 7.28 to 16.0 ?15N ‰ for the Weddell seal), which may be a result of greatly changing diets in the last ~10,000 years, or a changing baseline N value for the Ross Sea. Seal bones will be radiocarbon-dated to isolate the key shifts in C and N isotopic values. Once those major shifts are temporally constrained, compound-specific isotopic analysis of the bone samples will be used to tease apart the diet vs. baseline effects on the bulk isotopic signatures of the seals. Our results suggests that during the last ~10,000 years, there was a fundamental shift in Ross Sea food web structure likely related to long term climatic variability.

  11. Compound-specific amino acid ?15N patterns in marine algae: Tracer potential for cyanobacterial vs. eukaryotic organic nitrogen sources in the ocean

    NASA Astrophysics Data System (ADS)

    McCarthy, Matthew D.; Lehman, Jennifer; Kudela, Raphael

    2013-02-01

    Stable nitrogen isotopic analysis of individual amino acids (?15N-AA) has unique potential to elucidate the complexities of food webs, track heterotrophic transformations, and understand diagenesis of organic nitrogen (ON). While ?15N-AA patterns of autotrophs have been shown to be generally similar, prior work has also suggested that differences may exist between cyanobacteria and eukaryotic algae. However, ?15N-AA patterns in differing oceanic algal groups have never been closely examined. The overarching goals of this study were first to establish a more quantitative understanding of algal ?15N-AA patterns, and second to examine whether ?15N-AA patterns have potential as a new tracer for distinguishing prokaryotic vs. eukaryotic N sources. We measured ?15N-AA from prokaryotic and eukaryotic phytoplankton cultures and used a complementary set of statistical approaches (simple normalization, regression-derived fractionation factors, and multivariate analyses) to test for variations. A generally similar ?15N-AA pattern was confirmed for all algae, however significant AA-specific variation was also consistently identified between the two groups. The relative ?15N fractionation of Glx (glutamine + glutamic acid combined) vs. total proteinaceous N appeared substantially different, which we hypothesize could be related to differing enzymatic forms. In addition, the several other AA (most notably glycine and leucine) appeared to have strong biomarker potential. Finally, we observed that overall patterns of ?15N values in algae correspond well with the Trophic vs. Source-AA division now commonly used to describe variable AA ?15N changes with trophic transfer, suggesting a common mechanistic basis. Overall, these results show that autotrophic ?15N-AA patterns can differ between major algal evolutionary groupings for many AA. The statistically significant multivariate results represent a first approach for testing ideas about relative eukaryotic vs. prokaryotic ON sources in the sea.

  12. Solving the woolly mammoth conundrum: amino acid 15N-enrichment suggests a distinct forage or habitat

    PubMed Central

    Schwartz-Narbonne, Rachel; Longstaffe, Fred J.; Metcalfe, Jessica Z.; Zazula, Grant

    2015-01-01

    Understanding woolly mammoth ecology is key to understanding Pleistocene community dynamics and evaluating the roles of human hunting and climate change in late Quaternary megafaunal extinctions. Previous isotopic studies of mammoths’ diet and physiology have been hampered by the ‘mammoth conundrum’: woolly mammoths have anomalously high collagen ?15N values, which are more similar to coeval carnivores than herbivores, and which could imply a distinct diet and (or) habitat, or a physiological adaptation. We analyzed individual amino acids from collagen of adult woolly mammoths and coeval species, and discovered greater ?15N enrichment in source amino acids of woolly mammoths than in most other herbivores or carnivores. Woolly mammoths consumed an isotopically distinct food source, reflective of extreme aridity, dung fertilization, and (or) plant selection. This dietary signal suggests that woolly mammoths occupied a distinct habitat or forage niche relative to other Pleistocene herbivores. PMID:26056037

  13. Ratios of 15N/12C and 4He/12C inclusive electroproduction cross sections in the nucleon resonance region

    SciTech Connect

    Peter Bosted; Robert Fersch

    2007-12-14

    The ratio of inclusive electron scattering cross sections for 15N/12C was determined in the kinematic range 0.8<2 GeV and 0.2<1 GeV2 using 2.285 GeV electrons and the CLAS detector at Jefferson Lab. The ratio exhibits only slight resonance structure, as predicted by a phenomenological model, and also by quark-hadron duality. Within the super-scaling quasi-elastic model, slight evidence is found for a 1 MeV lower effective nucleon binding energy in 15N than in 12C. Ratios of 4He/12C using 1.6 to 2.5 GeV electrons are in good agreement with the phenomenological model.

  14. Solving the woolly mammoth conundrum: amino acid 15N-enrichment suggests a distinct forage or habitat

    NASA Astrophysics Data System (ADS)

    Schwartz-Narbonne, Rachel; Longstaffe, Fred J.; Metcalfe, Jessica Z.; Zazula, Grant

    2015-06-01

    Understanding woolly mammoth ecology is key to understanding Pleistocene community dynamics and evaluating the roles of human hunting and climate change in late Quaternary megafaunal extinctions. Previous isotopic studies of mammoths’ diet and physiology have been hampered by the ‘mammoth conundrum’: woolly mammoths have anomalously high collagen ?15N values, which are more similar to coeval carnivores than herbivores, and which could imply a distinct diet and (or) habitat, or a physiological adaptation. We analyzed individual amino acids from collagen of adult woolly mammoths and coeval species, and discovered greater ?15N enrichment in source amino acids of woolly mammoths than in most other herbivores or carnivores. Woolly mammoths consumed an isotopically distinct food source, reflective of extreme aridity, dung fertilization, and (or) plant selection. This dietary signal suggests that woolly mammoths occupied a distinct habitat or forage niche relative to other Pleistocene herbivores.

  15. Use of a 15N tracer to determine linkages between a mangrove and an upland freshwater swamp

    NASA Astrophysics Data System (ADS)

    MacKenzie, R. A.; Cormier, N.

    2005-05-01

    Mangrove forests and adjacent upland freshwater swamps are important components of subsistence-based economies of Pacific islands. Mangroves provide valuable firewood (Rhizophora apiculata) and mangrove crabs (Scylla serrata); intact freshwater swamps are often used for agroforestry (e.g., taro cultivation). While these two systems are connected hydrologically via groundwater and surface flows, little information is available on how they may be biogeochemically or ecologically linked. For example, mangrove leaf litter was once thought to be an important food source for resident and transient nekton and invertebrates, but this value may have been overestimated. Instead, nutrients or allochthonous material (e.g., phytoplankton, detritus) delivered via groundwater or surface water from upland freshwater swamps may play a larger role in mangrove food webs. Understanding the linkages between these two ecologically and culturally important ecosystems will help us to understand the potential impacts of hydrological alterations that occur when roads or bridges are constructed through them. We conducted a 15N tracer study in the Yela watershed on the island of Kosrae, Federated States of Micronesia. K15NO3 was continually added at trace levels for 4 weeks to the Yela River in an upland freshwater swamp adjacent to a mangrove forest. Nitrate and ammonium pools, major primary producers, macroinvertebrates, and fish were sampled from stations 5 m upstream (freshwater swamp) and 138, 188, 213, and 313 m downstream (mangrove) from the tracer addition. Samples were collected once a week prior to, during, and after the 15N addition for a total of 6 weeks. Preliminary results revealed no significant enrichment (< 1 ‰) in the 15N isotope composition of either resident shrimp (Macrobrachium sp.) or mudskipper fish (Periophthalmus sp.). However, the 15N signature of ammonium pools was enriched 10-60 ‰ by the end of the third week. These results suggest that the tracer was present in the mangrove but was either unavailable to higher organisms or was incorporated into organic matter not utilized by shrimp or mudskippers.

  16. Evaluating mercury biomagnification in fish from a tropical marine environment using stable isotopes (delta13C and delta15N).

    PubMed

    Al-Reasi, Hassan A; Ababneh, Fuad A; Lean, David R

    2007-08-01

    Concentrations of total mercury (T-Hg) and methylmercury (MeHg) were measured in zooplankton and 13 fish species from a coastal food web of the Gulf of Oman, an arm of the Arabian Sea between Oman and Iran. Stable isotope ratios (delta13C and delta15N) also were determined to track mercury biomagnification. The average concentration of T-Hg in zooplankton was 21 +/- 8.0 ng g(-1) with MeHg accounting 10% of T-Hg. Total mercury levels in fish species ranged from 3.0 ng g(-1) (Sardinella longiceps) to 760 ng g(-1) (Rhizoprionodon acutus) with relatively lower fraction of MeHg (72%) than that found in other studies. The average trophic difference (Deltadelta13C) between zooplankton and planktivorous fish (Selar crumenopthalmus, Rastrelliger kanagurta, and S. longiceps) was higher (3.4 per thousandth) than expected, suggesting that zooplankton may not be the main diet or direct carbon source for these fish species. However, further sampling would be required to compensate for temporal changes in zooplankton and the influence of their lipid content. Trophic position inferred by delta15N and and slopes of the regression equations (log10[T-Hg] = 0.13[delta15N] - 3.57 and log10[MeHg] = 0.14[delta15N] - 3.90) as estimates of biomagnification indicate that biomagnification of T-Hg and MeHg was lower in this tropical ocean compared to what has been observed in arctic and temperate ecosystems and tropical African lakes. The calculated daily intake of methylmercury in the diet of local people through fish consumption was well below the established World Health Organization (WHO) tolerable daily intake threshold for most of the fish species except Euthynnus affinis, Epinephelus epistictus, R. acutus, and Thunnus tonggol, illustrating safe consumption of the commonly consumed fish species. PMID:17702328

  17. Imprint of oaks on nitrogen availability and ?15N in California grassland-savanna: A case of enhanced N inputs?

    USGS Publications Warehouse

    Perakis, S.S.; Kellogg, C.H.

    2007-01-01

    Woody vegetation is distributed patchily in many arid and semi-arid ecosystems, where it is often associated with elevated nitrogen (N) pools and availability in islands of fertility. We measured N availability and ?15N in paired blue-oak versus annual grass dominated patches to characterize the causes and consequences of spatial variation in N dynamics of grassland-savanna in Sequoia-Kings Canyon National Park. We found significantly greater surface soil N pools (0–20 cm) in oak patches compared to adjacent grass areas across a 700 m elevation gradient from foothills to the savanna-forest boundary. N accumulation under oaks was associated with a 0.6‰ depletion in soil ?15N relative to grass patches. Results from a simple ?15N mass balance simulation model, constrained by surface soil N and ?15N measured in the field, suggest that the development of islands of N fertility under oaks can be traced primarily to enhanced N inputs. Net N mineralization and percent nitrification in laboratory incubations were consistently higher under oaks across a range of experimental soil moisture regimes, suggesting a scenario whereby greater N inputs to oak patches result in net N accumulation and enhanced N cycling, with a potential for greater nitrate loss as well. N concentrations of three common herbaceous annual plants were nearly 50% greater under oak than in adjacent grass patches, with community composition shifted towards more N-demanding species under oaks. We find that oaks imprint distinct N-rich islands of fertility that foster local feedback between soil N cycling, plant N uptake, and herbaceous community composition. Such patch-scale differences in N inputs and plant–soil interactions increase biogeochemical heterogeneity in grassland-savanna ecosystems and may shape watershed-level responses to chronic N deposition.

  18. Application of Nitrogen and Carbon Stable Isotopes (?15N and ?13C) to Quantify Food Chain Length and Trophic Structure

    PubMed Central

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

    2014-01-01

    Increasingly, stable isotope ratios of nitrogen (?15N) and carbon (?13C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using ?15N, and carbon range (CR) using ?13C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in ?15N or ?13C from source to consumer) between trophic levels and among food chains. ?15N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. ?13C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of ?13C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of ecological systems. PMID:24676331

  19. Variation in ?13C and ?15N diet–vibrissae trophic discrimination factors in a wild population of California sea otters

    USGS Publications Warehouse

    Newsome, Seth D.; Bentall, Gena B.; Tinker, M. Tim; Oftedal, Olav T.; Ralls, Katherine; Estes, James A.; Fogel, Marilyn L.

    2010-01-01

    The ability to quantify dietary inputs using stable isotope data depends on accurate estimates of isotopic differences between a consumer (c) and its diet (d), commonly referred to as trophic discrimination factors (TDFs) and denoted by ?c-d. At present, TDFs are available for only a few mammals and are usually derived in captive settings. The magnitude of TDFs and the degree to which they vary in wild populations is unknown. We determined ?13C and ?15N TDFs for vibrissae (i.e., whiskers), a tissue that is rapidly becoming an informative isotopic substrate for ecologists, of a wild population of sea otters for which individual diet has been quantified through extensive observational study. This is one of the very few studies that report TDFs for free-living wild animals feeding on natural diets. Trophic discrimination factors of 2.2? ± 0.7? for ?13C and 3.5? ± 0.6? for ?15N (mean ± SD) were similar to those reported for captive carnivores, and variation in individual ?13C TDFs was negatively but significantly related to sea urchin consumption. This pattern may relate to the lipid-rich diet consumed by most sea otters in this population and suggests that it may not be appropriate to lipid-extract prey samples when using the isotopic composition of keratinaceous tissues to examine diet in consumers that frequently consume lipid-rich foods, such as many marine mammals and seabirds. We suggest that inherent variation in TDFs should be included in isotopically based estimates of trophic level, food chain length, and mixing models used to quantify dietary inputs in wild populations; this practice will further define the capabilities and limitations of isotopic approaches in ecological studies.

  20. Validating the Incorporation of 13C and 15N in a Shorebird That Consumes an Isotopically Distinct Chemosymbiotic Bivalve

    PubMed Central

    van Gils, Jan A.; Ahmedou Salem, Mohamed Vall

    2015-01-01

    The wealth of field studies using stable isotopes to make inferences about animal diets require controlled validation experiments to make proper interpretations. Despite several pleas in the literature for such experiments, validation studies are still lagging behind, notably in consumers dwelling in chemosynthesis-based ecosystems. In this paper we present such a validation experiment for the incorporation of 13C and 15N in the blood plasma of a medium-sized shorebird, the red knot (Calidris canutus canutus), consuming a chemosymbiotic lucinid bivalve (Loripes lucinalis). Because this bivalve forms a symbiosis with chemoautotrophic sulphide-oxidizing bacteria living inside its gill, the bivalve is isotopically distinct from ‘normal’ bivalves whose food has a photosynthetic basis. Here we experimentally tested the hypothesis that isotope discrimination and incorporation dynamics are different when consuming such chemosynthesis-based prey. The experiment showed that neither the isotopic discrimination factor, nor isotopic turnover time, differed between birds consuming the chemosymbiotic lucinid and a control group consuming a photosynthesis-based bivalve. This was true for 13C as well as for 15N. However, in both groups the 15N discrimination factor was much higher than expected, which probably had to do with the birds losing body mass over the course of the experiment. PMID:26458005

  1. Tracing the diet of the monitor lizard Varanus mabitang by stable isotope analyses (?15N, ?13C)

    NASA Astrophysics Data System (ADS)

    Struck, Ulrich; Altenbach, Alexander; Gaulke, Maren; Glaw, Frank

    2002-09-01

    In this study, we used analyses of stable isotopes of nitrogen (?15N) and carbon (?13C) to determine the trophic ecology of the monitor lizard Varanus mabitang. Stable isotopes from claws, gut contents, and soft tissues were measured from the type specimen. Samples from Varanus olivaceus, Varanus prasinus, Varanus salvator, the herbivorous agamid lizard Hydrosaurus pustulatus, and some plant matter were included for comparison. Our data show a rapid decrease in ?13C (about10‰) from food plants towards gut contents and soft tissues of herbivorous species. For the varanids, we found a significant linear correlation of decreasing ?13C and increasing ?15N from herbivorous towards carnivorous species. In terms of trophic isotope ecology, the type specimen of V. mabitang is a strict herbivore. Thus it differs significantly in its isotopic composition from the morphologically next closest related species V. olivaceus. The most highly carnivorous species is V. salvator, while ?15N values for V. prasinus and V. olivaceus are intermediate. Claws provide very valuable samples for such measurements, because they can be sampled from living animals without harm. Additionally, their range of variability is relatively small in comparison with measurements from soft tissues.

  2. 15N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose

    USGS Publications Warehouse

    Thorn, K.A.; Kennedy, K.R.

    2002-01-01

    The five major reductive degradation products of TNT-4ADNT (4-amino-2,6-dinitrotoluene), 2ADNT (2-amino-4,6-dinitrotoluene), 2,4DANT (2,4-diamino-6-nitrotoluene), 2,6DANT (2,6-diamino-4-nitrotoluene), and TAT (2,4,6-triaminotoluene)-labeled with 15N in the amine positions, were reacted with the IHSS soil humic acid and analyzed by 15N NMR spectrometry. In the absence of catalysts, all five amines underwent nucleophilic addition reactions with quinone and other carbonyl groups in the soil humic acid to form both heterocyclic and nonheterocyclic condensation products. Imine formation via 1,2-addition of the amines to quinone groups in the soil humic acid was significant with the diamines and TAT but not the monoamines. Horseradish peroxidase (HRP) catalyzed an increase in the incorporation of all five amines into the humic acid. In the case of the diamines and TAT, HRP also shifted the binding away from heterocyclic condensation product toward imine formation. A comparison of quantitative liquid phase with solid-state CP/MAS 15N NMR indicated that the CP experiment underestimated imine and heterocyclic nitrogens in humic acid, even with contact times optimal for observation of these nitrogens. Covalent binding of the mono- and diamines to 4-methylcatechol, the HRP catalyzed condensation of 4ADNT and 2,4DANT to coniferyl alcohol, and the binding of 2,4DANT to lignocellulose with and without birnessite were also examined.

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  4. 15N NMR investigation of the reduction and binding of TNT in an aerobic bench scale reactor simulating windrow composting

    USGS Publications Warehouse

    Thorn, K.A.; Pennington, J.C.; Hayes, C.A.

    2002-01-01

    T15NT was added to a soil of low organic carbon content and composted for 20 days in an aerobic bench scale reactor. The finished whole compost and fulvic acid, humic acid, humin, and lignocellulose fractions extracted from the compost were analyzed by solid-state CP/MAS and DP/MAS 15N NMR. 15N NMR spectra provided direct spectroscopic evidence for reduction of TNT followed by covalent binding of the reduced metabolites to organic matter of the composted soil, with the majority of metabolite found in the lignocellulose fraction, by mass also the major fraction of the compost. In general, the types of bonds formed between soil organic matter and reduced TNT amines in controlled laboratory reactions were observed in the spectra of the whole compost and fractions, confirming that during composting TNT is reduced to amines that form covalent bonds with organic matter through aminohydroquinone, aminoquinone, heterocyclic, and imine linkages, among others. Concentrations of imine nitrogens in the compost spectra suggestthat covalent binding bythe diamines 2,4DANT and 2,6DANT is a significant process in the transformation of TNT into bound residues. Liquid-phase 15N NMR spectra of the fulvic acid and humin fractions provided possible evidence for involvement of phenoloxidase enzymes in covalent bond formation.

  5. Differentiation of Histidine Tautomeric States using 15N Selectively Filtered 13C Solid-State NMR Spectroscopy

    PubMed Central

    Miao, Yimin; Cross, Timothy A.; Fu, Riqiang

    2014-01-01

    The histidine imidazole ring in proteins usually contains a mixture of three possible tautomeric states (two neutral - ? and ? states and a charged state) at physiological pHs. Differentiating the tautomeric states is critical for understanding how the histidine residue participates in many structurally and functionally important proteins. In this work, one dimensional 15N selectively filtered 13C solid-state NMR spectroscopy is proposed to differentiate histidine tautomeric states and to identify all 13C resonances of the individual imidazole rings in a mixture of tautomeric states. When 15N selective 180° pulses are applied to the protonated or non-protonated nitrogen region, the 13C sites that are bonded to the non-protonated or protonated nitrogen sites can be identified, respectively. A sample of 13C,15N labeled histidine powder lyophilized from a solution at pH 6.3 has been used to illustrate the usefulness of this scheme by uniquely assigning resonances of the neutral ? and charged states from the mixture. PMID:25026459

  6. The effects of sex, tissue type, and dietary components on stable isotope discrimination factors (?13C and ?15N) in mammalian omnivores.

    PubMed

    Kurle, Carolyn M; Koch, Paul L; Tershy, Bernie R; Croll, Donald A

    2014-01-01

    We tested the effects of sex, tissue, and diet on stable isotope discrimination factors (?(13)C and ?(15)N) for six tissues from rats fed four diets with varied C and N sources, but comparable protein quality and quantity. The ?(13)C and ?(15)N values ranged from 1.7-4.1‰ and 0.4-4.3‰, respectively. Females had higher ?(15)N values than males because males grew larger, whereas ?(13)C values did not differ between sexes. Differences in ?(13)C values among tissue types increased with increasing variability in dietary carbon sources. The ?(15)N values increased with increasing dietary ?(15)N values for all tissues except liver and serum, which have fast stable isotope turnover times, and differences in ?(15)N values among tissue types decreased with increasing dietary animal protein. Our results demonstrate that variability in dietary sources can affect ?(13)C values, protein source affects ?(15)N values even when protein quality and quantity are controlled, and the isotope turnover rate of a tissue can influence the degree to which diet affects ?(15)N values. PMID:24787278

  7. Quantification of (15)N-nitrate in urine with gas chromatography combustion isotope ratio mass spectrometry to estimate endogenous NO production.

    PubMed

    Houben, Els; Hamer, Henrike M; Luypaerts, Anja; De Preter, Vicky; Evenepoel, Pieter; Rutgeerts, Paul; Verbeke, Kristin

    2010-01-15

    The use of stable isotope labeled substrates and subsequent analysis of urinary nitrate, forms a noninvasive test for evaluation of the in vivo NO metabolism. The present paper describes a new method for simultaneous quantification of (15)N-nitrate and total nitrate with gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS). Nitrate, isolated from urine with a nitrate selective resin, was reduced to nitrite using copperized cadmium. Subsequently, Sudan I was formed by diazotation. Sudan II was added as internal standard, and both molecules were analyzed with GC-C-IRMS as tert-butyldimethylsilyl derivatives. The accuracy was determined during a recovery study of two different known nitrate concentrations and two (15)N-enrichments. A recovery of 101.6% and 103.9% for total nitrate and 107.6% and 91.2% for (15)N-nitrate was obtained, respectively. The validated method was applied on complete 72 h urine collections after intravenous administration of (15)N-nitrate and (15)N-arginine in humans. On average, 51.8% (47.0-71.0%) of administered (15)N-nitrate was excreted, while 0.68% (0.44-1.17%) of (15)N-arginine was metabolized to nitrate. In conclusion, this method can be used for accurate simultaneous determination of (15)N-nitrate and total nitrate concentrations in urine and can be applied in clinical studies for noninvasive evaluation of NO metabolism in vivo. PMID:20000695

  8. Using d15 N in Fish Larvae as an Indicator of Watershed Sources of Anthropogenic Nitrogen: Response at Multiple Spatial Scales

    EPA Science Inventory

    The nitrogen stable isotope, 15N, is an effective tool to track anthropogenic N sources to aquatic ecosystems. It may be difficult to identify potential N sources, however, where 15N responds similarly to multiple, concurrent activities in the watershed that cause higher nutrient...

  9. 15N Isotopic Crop Exchange Residue Studies Suggest that IPCC N Input Methodologies to Assess N2O-N Emissions Should be Reevaluated

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is difficult to quantify nitrogen (N) losses from agricultural systems to the environment, however we can use 15N isotopic techniques to conduct site specific studies to increase our knowledge about N management and fate. This manuscript synthesizes the review of two selected 15N isotopic studies...

  10. Quantitative analysis of 15N labeled positional isomers of glutamine and citrulline via electrospray ionization tandem mass spectrometry of their dansyl derivatives

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The enteral metabolism of glutamine and citrulline are intertwined because, while glutamine is one of the main fuel sources for the enterocyte, citrulline is one of its products. It has been shown that the administration of 15N labeled glutamine results in the incorporation of the 15N label into cit...

  11. Reconstruction of the oceanic nitrate inventory in the Pliocene Caribbean Sea: Foraminifera-bound ?15N - A new approach

    NASA Astrophysics Data System (ADS)

    Straub, M.; Haug, G. H.; Sigman, D. M.; Ren, H.

    2010-12-01

    The nitrate budget in the low-latitude surface ocean is mainly controlled by the opposing effects of denitrification and nitrate fixation. The state of the global ocean nitrate inventory highly affects primary production, which allows sequestering CO2 into the deep ocean. This may influence climate variability and control warm and cold periods in Earth history. Studies have shown that nitrogen isotopes reflect the nutrient status of the upper water column and therefore can be used as proxy for the state of the ocean’s ‘biological pump’. The nitrate inventory has mostly been reconstructed based on bulk sedimentary N-isotope measurements, which can be affected by syn- and post-sedimentary processes. Promising approaches to circumvent these potential biases are based on measurements of foraminifera-bound ?15N isotopes. In the subtropical and tropical ocean, planktonic foraminifera are a main component of the sinking particle flux. The organic compounds encapsulated within the foraminiferal tests are protected from sedimentary diagenetic processes and record a pristine signal of the nitrate composition of the upper water column. The novel method used in this study employs denitrifying bacteria (Pseudomonas chlororaphis and Pseudomonas aureofaciens) to produce nitrous oxide (N2O), recovered from the nitrate extracted from the organic matter sheltered within the foraminifera shell. The extracted N2O is analyzed for ?15N with a Gas bench II - IRMS and yields results with reproducible isotopic measurements of samples with nitrate concentrations down to 1 ?M. Previous data from the investigated site (ODP Leg 165, Site 999A, Caribbean Sea), spanning the last 30’000 yrs using the same method, indicate a systematic difference between glacial and interglacial values. The glacial state is characterized by high ?15N values around ~ 5 ‰ (suggesting less N-fixation) and the interglacial by low ?15N values around ~ 3 ‰ (N-fixation increase). Pliocene data from foraminifera-bound ?15N of Globigerinoides ruber, Globigerinoides sacculifer and Orbulina universa reveal evidence for similar changes in the mean ocean nitrate behavior during glacial/interglacial cycles. Additionally, major climatic impacts like the onset of the Northern Hemisphere Glaciation and the progressive closure of the Panama Canal also seem to affect the oceanic nitrate cycle. The basic findings from the measured interval between 5.0 Ma to 1.9 Ma suggest that the dominating processes of N-fixation and denitrification were to some extent linked to the major climatic changes within this time period.

  12. TEA: Thermal Equilibrium Abundances

    NASA Astrophysics Data System (ADS)

    Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver

    2015-05-01

    TEA (Thermal Equilibrium Abundances) calculates gaseous molecular abundances under thermochemical equilibrium conditions. Given a single T,P point or a list of T,P pairs (the thermal profile of an atmosphere) and elemental abundances, TEA calculates mole fractions of the desired molecular species. TEA uses 84 elemental species and thermodynamical data for more then 600 gaseous molecular species, and can adopt any initial elemental abundances.

  13. Non-homogeneity of isotopic labelling in 15N gas flux studies: theory, some observations and possible lessons

    NASA Astrophysics Data System (ADS)

    Well, Reinhard; Buchen, Caroline; Deppe, Marianna; Eschenbach, Wolfram; Gattinger, Andreas; Giesemann, Anette; Krause, Hans-Martin; Lewicka-Szczebak, Dominika

    2015-04-01

    Quantifying dinitrogen (N2) and nitrous oxide (N2O) fluxes from different soil N pools and processes can be accomplished using the 15N tracer technique but this is subject to four different sources of bias (i. - iv.). This approach includes 15N labelling of selected N pools in soil and subsequent isotope analysis of all relevant N pools as well as of gas samples from enclosures, i.e. mixtures of soil-derived and atmospheric N2 and N2O. Depending on the processes of interest, there may be 15N labelling of one or several N pools, were several labelling treatment are needed in the latter case (e.g. Müller et al., 2004). Measuring pool-derived N2 or N2O has been shown to include two calculation problems, (i.) arising from multiple pools (e.g. Arah, 1992) and (ii.) dealing with the non-random distribution of N2 and N2O mole masses (Hauck et al., 1958). Non-randomness can be solved if m/z 28, 29 and 30 are correctly analysed and the 15N enrichment of one (to distinguish two pools, i.e. soil and atmosphere) or two pools (in case of three pools) is known (Spott & Stange, 2008). Moreover (iii.), NO3- pools generating N2 and N2O via denitrification can be identical or different, e.g. if N2O evolved from higher enriched NO3- in deeper soil was more reduced to N2 compared to N2O evolved from N2O from shallow soil with lower enrichment, or vice versa. Apportioning N2O fluxes to NH4+ (nitrification and/or nitrifier denitrification) and NO3- (denitrification) is often conducted by NO3-labeling, measuring ?15N of emitted N2O and applying mixing equations were the measured 15N enrichment of NH4+and NO3-pool is used. However, this assumes that the average 15N enrichment of NH4+and NO3-in the soil is identical to the enrichment in the active soil domain producing N2 and/or N2O. Violation of this precondition must lead to bias in source apportionment (iv.), but to our knowledge this has not been investigated until now. Here we present conceptual models and model calculations addressing cases iii. and iv.. Furthermore we present some experimental data illustrating this. These include two data sets from denitrification experiments exhibiting substantial deviations in 15N enrichment between the N pools producing N2 and N2O. Moreover, results from a lab incubation study to quantify NH4+-derived N2O with increasing NH4+ amendment under conditions favouring nitrification are shown, were non-labelled NH4+ was added together with 15N labelled NO3-. Here we found large deviations between the 15N enrichment of NO3- in extracted soil water and the 15N enrichment of the labelled N pool as calculated from N2O isotopologues (Bergsma et al., 2001). We think that this reflects type iv. bias, probably because enrichment of NO3- in anoxic micro-sites was less diluted by non-labelled NO3- from nitrification compared to NO3- in oxic zones. Our data analysis provides a means to overcome bias iv. and thus to obtain correct source apportionment. References: Arah, J.R.M. (1992): Soil Sci. Soc. Am. J. 56, 795 - 800, 1992. Bergsma, T. et al. (2001): Env. Sci. & Technol. 35(21): 4307-4312. Hauck, R.D., et al.(1958): Soil Science 86, 287 - 291, 1958. Lewicka-Szczebak, D. et al.(2013): Rapid Comm. Mass Spectrom., 27 1548-1558. Müller, C. et al. (2004): Soil Biol. Biochem. 36(4): 619-632. Mulvaney, R.L.(1984):. Soil Sci. Soc. Am. J. 48:690 - 692. Spott, O, et al.. (2006): Rapid Comm. Mass Spectrom., 20: 3267-3274. Spott, O. and C. F. Stange (2007): Rapid Comm. Mass Spectrom., 21: 2398-2406.

  14. Compound-specific 15N stable isotope probing of N assimilation by the soil microbial biomass: a new methodological paradigm in soil N cycling

    NASA Astrophysics Data System (ADS)

    Charteris, A. F.; Knowles, T. D. J.; Michaelides, K.; Evershed, R. P.

    2015-10-01

    A compound-specific nitrogen-15 stable isotope probing (15N-SIP) technique is described which allows investigation of the fate of inorganic- or organic-N amendments to soils. The technique uses gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) to determine the ?15N values of individual amino acids (AAs; determined as N-acetyl, O-isopropyl derivatives) as proxies of biomass protein production. The ?15N values are used together with AA concentrations to quantify N assimilation of 15N-labelled substrates by the soil microbial biomass. The utility of the approach is demonstrated through incubation experiments using inorganic 15N-labelled substrates ammonium (15NH4+) and nitrate (15NO3-) and an organic 15N-labelled substrate, glutamic acid (15N-Glu). Assimilation of all the applied substrates was undetectable based on bulk soil properties, i.e. % total N (% TN), bulk soil N isotope composition and AA concentrations, all of which remained relatively constant throughout the incubation experiments. In contrast, compound-specific AA ?15N values were highly sensitive to N assimilation, providing qualitative and quantitative insights into the cycling and fate of the applied 15N-labelled substrates. The utility of this 15N-AA-SIP technique is considered in relation to other currently available methods for investigating the microbially-mediated assimilation of nitrogenous substrates into the soil organic N pool. This approach will be generally applicable to the study of N cycling in any soil, or indeed, in any complex ecosystem.

  15. Temporal variation in mycorrhizal diversity and carbon and nitrogen stable isotope abundance in the wintergreen meadow orchid Anacamptis morio.

    PubMed

    Ercole, Enrico; Adamo, Martino; Rodda, Michele; Gebauer, Gerhard; Girlanda, Mariangela; Perotto, Silvia

    2015-02-01

    Many adult orchids, especially photoautotrophic species, associate with a diverse range of mycorrhizal fungi, but little is known about the temporal changes that might occur in the diversity and functioning of orchid mycorrhiza during vegetative and reproductive plant growth. Temporal variations in the spectrum of mycorrhizal fungi and in stable isotope natural abundance were investigated in adult plants of Anacamptis morio, a wintergreen meadow orchid. Anacamptis morio associated with mycorrhizal fungi belonging to Tulasnella, Ceratobasidium and a clade of Pezizaceae (Ascomycetes). When a complete growing season was investigated, multivariate analyses indicated significant differences in the mycorrhizal fungal community. Among fungi identified from manually isolated pelotons, Tulasnella was more common in autumn and winter, the pezizacean clade was very frequent in spring, and Ceratobasidium was more frequent in summer. By contrast, relatively small variations were found in carbon (C) and nitrogen (N) stable isotope natural abundance, A. morio samples showing similar (15)N enrichment and (13)C depletion at the different sampling times. These observations suggest that, irrespective of differences in the seasonal environmental conditions, the plant phenological stages and the associated fungi, the isotopic content in mycorrhizal A. morio remains fairly constant over time. PMID:25382295

  16. Determination of the delta(15N/14N)of Ammonium (NH4+) in Water: RSIL Lab Code 2898

    USGS Publications Warehouse

    Hannon, Janet E.; Böhlke, John Karl

    2008-01-01

    The purpose of the technique described by Reston Stable Isotope Laboratory (RSIL) lab code 2898 is to determine the N isotopic composition, delta(15N/14N), abbreviated as d15N, of ammonium (NH4+) in water (freshwater and saline water). The procedure involves converting dissolved NH4+ into NH3 gas by raising the pH of the sample to above 9 with MgO and subsequently trapping the gas quantitatively as (NH4)2SO4 on a glass fiber (GF) filter. The GF filter is saturated with NaHSO4 and pressure sealed between two gas-permeable polypropylene filters. The GF filter 'sandwich' floats on the surface of the water sample in a closed bottle. NH3 diffuses from the water through the polypropylene filter and reacts with NaHSO4, forming (NH4)2SO4 on the GF filter. The GF filter containing (NH4)2SO4 is dried and then combusted with a Carlo Erba NC 2500 elemental analyzer (EA), which is used to convert total nitrogen in a solid sample into N2 gas. The EA is connected to a continuous-flow isotope-ratio mass spectrometer (CF-IRMS), which determines the relative difference in ratios of the amounts of the stable isotopes of nitrogen (15N and 14N) of the product N2 gas and a reference N2 gas. The filters containing the samples are compressed in tin capsules and loaded into a Costech Zero-Blank Autosampler on the EA. Under computer control, samples then are dropped into a heated reaction tube that contains an oxidant, where combustion takes place in a He atmosphere containing an excess of O2 gas. To remove S-O gases produced from the NaHSO4, a plug of Ag-coated Cu wool is inserted at the bottom of the reaction tube. Combustion products are transported by a He carrier through a reduction furnace to remove excess O2, toconvert all nitrogen oxides to N2, and to remove any remaining S-O gases. The gases then pass through a drying tube to remove water. The gas-phase products, mainly N2 and a small amount of background CO2, are separated by a gas chromatograph (GC). The gas is then introduced into the IRMS through a Finnigan ConFlo II interface. The ConFlo II interface is used to introduce not only sample into the IRMS but also N2 reference gas and He for sample dilution. The flash combustion is quantitative, so no isotopic fractionation is involved. The IRMS is a Finnigan Delta V CF-IRMS with 10 cups and is capable of detecting ion beams with mass/charge (m/z) 28, 29, 30. The ion beams from N2 are as follows: m/z 28 = 14N14N, m/z 29 = 14N15N, and m/z 30 = 15N15N. The ion beam with m/z 30 also represents 14N16O, which may indicate contamination or incomplete reduction.

  17. Similarities and differences in 13C and 15N stable isotope ratios in two non-lethal tissue types from shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820)

    USGS Publications Warehouse

    DeVries, R. J.; Schramm, Harold L., Jr.

    2015-01-01

    We tested the hypothesis that ?13C and ?15N signatures of pectoral spines would provide measures of ?13C and ?15N similar to those obtained from fin clips for adult shovelnose sturgeon Scaphirhynchus platorynchus. Thirty-two shovelnose sturgeon (fork length [FL] = 500–724 mm) were sampled from the lower Mississippi River, USA on 23 February 2013. Isotopic relationships between the two tissue types were analyzed using mixed model analysis of covariance. Tissue types differed significantly for both ?13C (P < 0.01; spine: mean = ?23.83, SD = 0.62; fin clip: mean = ?25.74, SD = 0.97) and ?15N (P = 0.01; spine: mean = 17.01, SD = 0.51; fin clip: mean = 17.19, SD = 0.62). Neither FL nor the FL × tissue type interaction had significant (P > 0.05) effects on ?13C. Fin clip ?13C values were highly variable and weakly correlated (r = 0.16, P = 0.40) with those from pectoral spines. We found a significant FL-tissue type interaction for ?15N, reflecting increasing ?15N with FL for spines and decreasing ?15N with FL for fin clips. These results indicate that spines are not a substitute for fin clip tissue for measuring ?13C and ?15N for shovelnose sturgeon in the lower Mississippi River, but the two tissues have different turnover rates they may provide complementary information for assessing trophic position at different time scales.

  18. Endogenous and environmental factors influence the dietary fractionation of 13C and 15N in hissing cockroaches Gromphadorhina portentosa.

    PubMed

    McCue, Marshall D

    2008-01-01

    Since DeNiro and Epstein's discovery that the (13)C and (15)N isotopic signatures of animals approximate those of their respective diets, the measurement of stable isotope signatures has become an important tool for ecologists studying the diets of wild animals. This study used Madagascar hissing cockroaches (Gromphadorhina portentosa) to examine several preexisting hypotheses about the relationship between the isotopic composition of an animal and its diet. Contrary to my predictions, the results revealed that the tissues of adult cockroaches raised for two generations on a diet of known isotopic composition did not demonstrate enrichment of heavy stable isotopes. Moreover, the (15)N signatures of cockroaches were neither influenced by periods of rapid growth (i.e., 300-fold increase in dry body mass over 120 d) nor by imposed periods of starvation lasting up to 80 d. The offspring born to mothers raised on known diets were enriched in (15)N. Diet-switching experiments showed that turnover times of (13)C were highly correlated with age and ranged from 9 to 10 d to 60 to 75 d in subadults and adults, respectively. Adults subjected to diet switches differed from the subadults in that the adults achieved equilibrated isotopic signatures that were shifted approximately 1.0 per thousand toward their respective original diets. Lipid fractions of adult cockroaches averaged 2.9 per thousand more depleted in (13)C than in lipid-free fractions, but no changes in (13)C were observed in aging adults. Exposure to reduced ambient temperature from 33 degrees C to 23 degrees C over 120 d did not influence isotopic signatures of tissues. Overall, the results of this study reveal that different endogenous and exogenous factors can influence the isotopic signatures of cockroaches. These findings reinforce the need to conduct controlled studies to further examine environmental factors that influence the relationships between the isotopic signatures of animals and their diets. PMID:18040969

  19. Changes in soil nitrogen storage and ?15N with woody plant encroachment in a subtropical savanna parkland landscape

    NASA Astrophysics Data System (ADS)

    Boutton, T. W.; Liao, J. D.

    2010-09-01

    Subtropical woodlands dominated by N-fixing tree legumes have largely replaced grasslands in the Rio Grande Plains, southwestern United States, during the past century. To evaluate the impact of this vegetation change on the N cycle, we measured the mass and isotopic composition (?15N) of N in the soil system of remnant grasslands and woody plant stands ranging in age from 10 to 130 years. Nitrogen accumulated at linear rates following woody encroachment in the litter (0.10-0.14 g N m-2 yr-1), roots (0.63-0.98 g N m-2 yr-1), and soils (0.75-3.50 g N m-2 yr-1), resulting in a 50%-150% increase in N storage in the soil system (0-30 cm) in woody stands older than 60 years. Simultaneous decreases in soil ?15N of up to 2‰ in the upper 30 cm of the profile are consistent with a scenario in which N inputs have exceeded losses following woody encroachment and suggest N accrual was derived from symbiotic N fixation by tree legumes and/or differential atmospheric N deposition to wooded areas. Vertical uplift and lateral transfer of N by the more deeply and intensively rooted woody plants may have contributed to N accumulation in wooded areas, but soil ?15N values are inconsistent with this explanation. N accumulation following woody encroachment may alter soil N availability, species interactions and successional dynamics, flux rates of key trace gases such as NOX and N2O and ecosystem C sequestration. Given the geographic dimensions of woody encroachment, these results may have implications for atmospheric composition and the climate system.

  20. Alkaline Hydrolysis/Polymerization of 2,4,6-Trinitrotoluene: Characterization of Products by 13C and 15N NMR

    USGS Publications Warehouse

    Thorn, K.A.; Thorne, P.G.; Cox, L.G.

    2004-01-01

    Alkaline hydrolysis has been investigated as a nonbiological procedure for the destruction of 2,4,6-trinitrotoluene (TNT) in explosives contaminated soils and munitions scrap. Nucleophilic substitutions of the nitro and methyl groups of TNT by hydroxide ion are the initial steps in the alkaline degradation of TNT. Potential applications of the technique include both in situ surface liming and ex situ alkaline treatment of contaminated soils. A number of laboratory studies have reported the formation of an uncharacterized polymeric material upon prolonged treatment of TNT in base. As part of an overall assessment of alkaline hydrolysis as a remediation technique, and to gain a better understanding of the chemical reactions underlying the hydrolysis/polymerization process, the soluble and precipitate fractions of polymeric material produced from the calcium hydroxide hydrolysis of unlabeled and 15N-labeled TNT were analyzed by elemental analysis and 13C and 15N nuclear magnetic resonance spectroscopy. Spectra indicated that reactions leading to polymerization included nucleophilic displacement of nitro groups by hydroxide ion, formation of ketone, carboxyl, alcohol, ether, and other aliphatic carbons, conversion of methyl groups to diphenyl methylene carbons, and recondensation of aromatic amines and reduced forms of nitrite, including ammonia and possibly hydroxylamine, into the polymer. Compared to the distribution of carbons in TNT as 14% sp 3- and 86% sp2-hybridized, the precipitate fraction from hydrolysis of unlabeled TNT contained 33% sp3- and 67% sp 2-hybridized carbons. The concentration of nitrogen in the precipitate was 64% of that in TNT. The 15N NMR spectra showed that, in addition to residual nitro groups, forms of nitrogen present in the filtrate and precipitate fractions include aminohydroquinone, primary amide, indole, imine, and azoxy, among others. Unreacted nitrite was recovered in the filtrate fraction. The toxicities and susceptibilities to microbial or chemical degradation of the polymeric materials remain unknown.

  1. Assessing sources of nitrate contamination in the Shiraz urban aquifer (Iran) using the ?(15)N and ?(18)O dual-isotope approach.

    PubMed

    Amiri, Haleh; Zare, Mohammad; Widory, David

    2015-01-01

    Nitrate ([Formula: see text]) is one of the major threats to the quality of the drinking water taken from the Shiraz aquifer. This aquifer undergoes high anthropogenic pressures from multiple local urban (including uncontrolled sewage systems), agricultural and industrial activities, resulting in [Formula: see text] concentrations as high as 149 mg L(-1), well above the 50 mg L(-1) guideline defined by the World Health Organisation. We coupled here classical chemical and dual isotope (?(15)N and ?(18)O of [Formula: see text]) approaches trying to characterize sources and potential processes controlling the budget of this pollutant. Chemical data indicate that nitrate in this aquifer is explained by distinct end-members: while mineral fertilizers isotopically show to have no impact, our isotope approach identifies natural soil nitrification and organic [Formula: see text] (manure and/or septic waste) as the two main contributors. Isotope data suggest that natural denitrification may occur within the aquifer, but this conclusion is not supported by the study of other chemical parameters. PMID:25941866

  2. Partitioning Residue-derived and Residue-induced Emissions of N2O Using 15N-labelled Crop Residues

    NASA Astrophysics Data System (ADS)

    Farrell, R. E.; Carverhill, J.; Lemke, R.; Knight, J. D.

    2014-12-01

    Estimates of N2O emissions in Canada indicate that 17% of all agriculture-based emissions are associated with the decomposition of crop residues. However, research specific to the western Canadian prairies (including Saskatchewan) has shown that the N2O emission factor for N sources in this region typically ranges between 0.2 and 0.6%, which is well below the current IPCC default emission factor of 1.0%. Thus, it stands to reason that emissions from crop residues should also be lower than those calculated using the current IPCC emission factor. Current data indicates that residue decomposition, N mineralization and N2O production are affected by a number of factors such as C:N ratio and chemical composition of the residue, soil type, and soil water content; thus, a bench-scale incubation study was conducted to examine the effects of soil type and water content on N2O emissions associated with the decomposition of different crop residues. The study was carried out using soils from the Black, Dark Brown, Brown, and Gray soil zones and was conducted at both 50% and 70% water-filled pore space (WFPS); the soils were amended with 15N-labeled residues of wheat, pea, canola, and flax, or with an equivalent amount of 15N-labeled urea; 15N2O production was monitored using a Picarro G5101-i isotopic N2O analyzer. Crop residue additions to the soils resulted in both direct and indirect emissions of N2O, with residue derived emissions (RDE; measured as 15N2O) generally exceeding residue-induced emissions (RIE) at 50% WFPS—with RDEs ranging from 42% to 88% (mean = 58%) of the total N2O. Conversely, at 70% WFPS, RDEs were generally lower than RIEs—ranging from 21% to 83% (mean = 48%). Whereas both water content and soil type had an impact on N2O production, there was a clear and consistent trend in the emission factors for the residues; i.e., emissions were always greatest for the canola residue and lowest for the wheat residue and urea fertilizer; and intermediate for pea and flax. Results of this research demonstrate that—under the right environmental conditions—there is considerable potential for both direct and indirect N2O emissions during crop residue decomposition. Moreover, emission factors for the various crop residues tended to increase in the order: wheat ? urea < pea < flax << canola.

  3. Determination of the ?15N and ?13C of total nitrogen and carbon in solids; RSIL lab code 1832

    USGS Publications Warehouse

    Revesz, Kinga; Qi, Haiping; Coplan, Tyler B.

    2006-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 1832 is to determine the ?(15N/14N), abbreviated as ?15N, and the ?(13C/12C), abbreviated as ?13C, of total nitrogen and carbon in a solid sample. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total nitrogen and carbon in a solid sample into N2 and CO2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines the relative difference in stable nitrogen isotope-amount ratio (15N/14N) of the product N2 gas and the relative difference in stable carbon isotope-amount ratio (13C/12C) of the product CO2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in tin capsules and loaded into a Costech Zero Blank Autosampler on the EA. Under computer control, samples then are dropped into a heated reaction tube that contains an oxidant, where combustion takes place in a helium atmosphere containing an excess of oxygen gas. Combustion products are transported by a helium carrier through a reduction furnace to remove excess oxygen and to convert all nitrous oxides into N2 and through a drying tube to remove water. The gas-phase products, mainly CO2 and N2, are separated by a gas chromatograph. The gas is then introduced into the IRMS through a Finnigan MAT (now Thermo Scientific) ConFlo II interface. The Finnigan MAT ConFlo II interface is used for introducing not only sample into the IRMS but also N2 and CO2 reference gases and helium for sample dilution. The flash combustion is quantitative; no isotopic fractionation is involved. The IRMS is a Thermo Scientific Delta V CF-IRMS. It has a universal triple collector, two wide cups with a narrow cup in the middle; it is capable of measuring mass/charge (m/z) 28, 29, 30 or with a magnet current change 44, 45, 46, simultaneously. The ion beams from these m/z values are as follows: m/z 28 = N2 = 14N/14N; m/z 29 = N2 = 14N/15N primarily; m/z 30 = NO = 14N/16O primarily, which is a sign of contamination or incomplete reduction; m/z 44 = CO2 = 12C16O16O; m/z 45 = CO2 = 13C16O16O primarily; and m/z 46 = CO2 = 12C16O18O primarily.

  4. A new strategy for sequential assignment of intrinsically unstructured proteins based on 15N single isotope labelling.

    PubMed

    Lopez, Juan; Ahuja, Puneet; Gerard, Melanie; Wieruszeski, Jean-Michel; Lippens, Guy

    2013-11-01

    We describe a new efficient strategy for the sequential assignment of amide resonances of a conventional (15)N-(1)H HSQC spectrum of intrinsically unfolded proteins, based on composite NOESY-TOCSY and TOCSY-NOESY mixing times. These composite mixing times lead to a H?-proton mediated unidirectional transfer of amide to amide proton. We have implemented the composite mixing times in an HSQC-NOESY-HSQC manner to obtain directional connectivity between amides of neighbouring residues. We experimentally determine the optimal mixing times for both transfer schemes, and demonstrate its use in the assignment for both a fragment of the neuronal tau protein and for ?-synuclein. PMID:24018100

  5. A priori predictions of the rotational constants for HC13N, HC15N, C5O

    NASA Technical Reports Server (NTRS)

    DeFrees, D. J.; McLean, A. D.

    1989-01-01

    Ab initio molecular orbital theory is used to estimate the rotational constant for several carbon-chain molecules that are candidates for discovery in interstellar space. These estimated rotational constants can be used in laboratory or astronomical searches for the molecules. The rotational constant for HC13N is estimated to be 0.1073 +/- 0.0002 GHz and its dipole moment 5.4 D. The rotational constant for HC15N is estimated to be 0.0724 GHz, with a somewhat larger uncertainty. The rotational constant of C5O is estimated to be 1.360 +/- 2% GHz and its dipole moment 4.4. D.

  6. Nitrogen retention across a gradient of 15N additions to an unpolluted temperate forest soil in Chile

    USGS Publications Warehouse

    Perakis, Steven S.; Compton, J.E.; Hedin, L.O.

    2005-01-01

    Accelerated nitrogen (N) inputs can drive nonlinear changes in N cycling, retention, and loss in forest ecosystems. Nitrogen processing in soils is critical to understanding these changes, since soils typically are the largest N sink in forests. To elucidate soil mechanisms that underlie shifts in N cycling across a wide gradient of N supply, we added 15NH415NO3 at nine treatment levels ranging in geometric sequence from 0.2 kg to 640 kg NA? ha-1A? yr-1 to an unpolluted old-growth temperate forest in southern Chile. We recovered roughly half of tracers in 0-25 cm of soil, primarily in the surface 10 cm. Low to moderate rates of N supply failed to stimulate N leaching, which suggests that most unrecovered 15N was transferred from soils to unmeasured sinks above ground. However, soil solution losses of nitrate increased sharply at inputs > 160 kg NA? ha-1A? yr-1, corresponding to a threshold of elevated soil N availability and declining 15N retention in soil. Soil organic matter (15N in soils at the highest N inputs and may explain a substantial fraction of the 'missing N' often reported in studies of fates of N inputs to forests. Contrary to expectations, N additions did not stimulate gross N cycling, potential nitrification, or ammonium oxidizer populations. Our results indicate that the nonlinearity in N retention and loss resulted directly from excessive N supply relative to sinks, independent of plant-soil-microbial feedbacks. However, N additions did induce a sharp decrease in microbial biomass C:N that is predicted by N saturation theory, and which could increase long-term N storage in soil organic matter by lowering the critical C:N ratio for net N mineralization. All measured sinks accumulated 15N tracers across the full gradient of N supply, suggesting that short-term nonlinearity in N retention resulted from saturation of uptake kinetics, not uptake capacity, in plant, soil, and microbial pools.

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

    SciTech Connect

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

    1994-12-01

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

  8. THE RGB AND AGB STAR NUCLEOSYNTHESIS IN LIGHT OF THE RECENT {sup 17}O(p, {alpha}){sup 14}N AND {sup 18}O(p, {alpha}){sup 15}N REACTION-RATE DETERMINATIONS

    SciTech Connect

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Pizzone, R. G.; Spitaleri, C.; Lamia, L.

    2013-02-20

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on A = 17 and A = 18 oxygen isotopes, overcoming extrapolation procedures and enhancement effects due to electron screening. In particular, the strengths of the 20 keV and 65 keV resonances in the {sup 18}O(p, {alpha}){sup 15}N and {sup 17}O(p, {alpha}){sup 14}N reactions, respectively, have been extracted, as well as the contribution of the tail of the broad 656 keV resonance in the {sup 18}O(p, {alpha}){sup 15}N reaction inside the Gamow window. The strength of the 65 keV resonance in the {sup 17}O(p, {alpha}){sup 14}N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the {sup 17}O + p radiative capture channel. As a result, more accurate reaction rates for the {sup 18}O(p, {alpha}){sup 15}N, {sup 17}O(p, {alpha}){sup 14}N, and {sup 17}O(p, {gamma}){sup 18}F processes have been deduced, devoid of systematic errors due to extrapolation or the electron screening effect. Such rates have been introduced into state-of-the-art red giant branch and asymptotic giant branch (AGB) models for proton-capture nucleosynthesis coupled with extra-mixing episodes. The predicted abundances have been compared with isotopic compositions provided by geochemical analysis of presolar grains. As a result, an improved agreement is found between the models and the isotopic mix of oxide grains of AGB origins, whose composition is the signature of low-temperature proton-capture nucleosynthesis. The low {sup 14}N/{sup 15}N found in SiC grains cannot be explained by the revised nuclear reaction rates and remains a serious problem that has not been satisfactorily addressed.

  9. DNA–protein ?-interactions in nature: abundance, structure, composition and strength of contacts between aromatic amino acids and DNA nucleobases or deoxyribose sugar

    PubMed Central

    Wilson, Katie A.; Kellie, Jennifer L.; Wetmore, Stacey D.

    2014-01-01

    Four hundred twenty-eight high-resolution DNA–protein complexes were chosen for a bioinformatics study. Although 164 crystal structures (38% of those searched) contained no interactions, 574 discrete ?–contacts between the aromatic amino acids and the DNA nucleobases or deoxyribose were identified using strict criteria, including visual inspection. The abundance and structure of the interactions were determined by unequivocally classifying the contacts as either ?–? stacking, ?–? T-shaped or sugar–? contacts. Three hundred forty-four nucleobase–amino acid ?–? contacts (60% of all interactions identified) were identified in 175 of the crystal structures searched. Unprecedented in the literature, 230 DNA–protein sugar–? contacts (40% of all interactions identified) were identified in 137 crystal structures, which involve C–H···? and/or lone–pair···? interactions, contain any amino acid and can be classified according to sugar atoms involved. Both ?–? and sugar–? interactions display a range of relative monomer orientations and therefore interaction energies (up to –50 (–70) kJ mol?1 for neutral (charged) interactions as determined using quantum chemical calculations). In general, DNA–protein ?-interactions are more prevalent than perhaps currently accepted and the role of such interactions in many biological processes may yet to be uncovered. PMID:24744240

  10. 13C and 15N—Chemical Shift Anisotropy of Ampicillin and Penicillin-V Studied by 2D-PASS and CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Antzutkin, Oleg N.; Lee, Young K.; Levitt, Malcolm H.

    1998-11-01

    The principal values of the chemical shift tensors of all13C and15N sites in two antibiotics, ampicillin and penicillin-V, were determined by 2-dimensionalphaseadjustedspinningsideband (2D-PASS) and conventional CP/MAS experiments. The13C and15N chemical shift anisotropies (CSA), and their confidence limits, were evaluated using a Mathematica program. The CSA values suggest a revised assignment of the 2-methyl13C sites in the case of ampicillin. We speculate on a relationship between the chemical shift principal values of many of the13C and15N sites and the ?-lactam ring conformation.

  11. The Solar Argon Abundance

    E-print Network

    Katharina Lodders

    2007-10-24

    The solar argon abundance cannot be directly derived by spectroscopic observations of the solar photosphere. The solar Ar abundance is evaluated from solar wind measurements, nucleosynthetic arguments, observations of B stars, HII regions, planetary nebulae, and noble gas abundances measured in Jupiter's atmosphere. These data lead to a recommended argon abundance of N(Ar) = 91,200(+/-)23,700 (on a scale where Si = 10^6 atoms). The recommended abundance for the solar photosphere (on a scale where log N(H) = 12) is A(Ar)photo = 6.50(+/-)0.10, and taking element settling into account, the solar system (protosolar) abundance is A(Ar)solsys = 6.57(+/-)0.10.

  12. Solar abundance of osmium

    PubMed Central

    Jacoby, George; Aller, Lawrence H.

    1976-01-01

    The abundance parameter, log gfA, where g is the statistical weight of the lower level, f is the oscillator strength, and A is the abundance (by numbers of atoms with respect to hydrogen), has been derived for three lines of osmium by a method of spectrum synthesis. An apparent discordance of the derived abundance with that found from the carbonaceous chondrites is probably to be attributed primarily to errors in the f-values, and blending with unknown contributors. PMID:16592314

  13. sup 1 H and sup 15 N resonance assignments of oxidized flavodoxin from Anacystis nidulans with 3D NMR

    SciTech Connect

    Clubb, R.T. Harvard Medical School, Boston, MA ); Thanabal, V.; Wagner, G. ); Osborne, C. )

    1991-08-06

    Proton and nitrogen-15 sequence-specific nuclear magnetic resonance assignments have been determined for recombinant oxidized flavodoxin from Anacystis nidulans. Assignments were obtained by using {sup 15}N-{sup 1}H heteronuclear three-dimensional (3D) NMR spectroscopy on a uniformly nitrogen-15 enriched sample of the protein, pH 6.6, at 30C. For 165 residues, the backbone and a large fraction of the side-chain proton resonances have been assigned. Medium- and long-range NOE's have been used to characterize the secondary structure. In solution, flavodoxin consists of a five-stranded parallel {beta} sheet involving residues 3-9, 31-37, 49-56, 81-89, 114-117, and 141-144. Medium-range NOE's indicate that presence of several helices. Several {sup 15}N and {sup 1}H resonances of the flavin mononucleotide (FMN) prosthetic group have been assigned. The FMN-binding site has been investigated by using polypeptide-FMN NOE's.

  14. The agricultural history of human-nitrogen interactions as recorded in ice core ?15N-NO3-

    NASA Astrophysics Data System (ADS)

    Felix, J. David; Elliott, Emily M.

    2013-04-01

    The advent and industrialization of the Haber Bosch process in the early twentieth century ushered in a new era of reactive nitrogen distributions on Earth. Since the appearance of the first commercial scale Haber Bosch fertilizer plants, fertilizer application rates have greatly increased in the U.S. While the contributions of fertilizer runoff to eutrophication and anoxic dead zones in coastal regions have been well-documented, the potential influences of increased fertilizer applications on air quality and precipitation chemistry are poorly constrained. Here we combine a 255-year record of precipitation nitrate isotopes preserved in a Greenland ice core, historical reconstructions of fertilizer application rates, and field characterization of the isotopic composition of nitrogen oxides produced biogenically in soils, to provide new constraints on the contributions of biogenic emissions to North American NOx inventories. Our results indicate that increases in twentieth century commercial fertilizer use led to large increases in soil NO, a byproduct released during nitrification and denitrification reactions. These large shifts in soil NO production are evidenced by sharp declines in ice core ?15N-NO3- values. Further, these results suggest that biogenic NOx emissions are underestimated by two to four fold in the U.S. NOx emission inventories used to construct global reactive nitrogen budgets. These results demonstrate that nitrate isotopes in ice cores, coupled with newly constrained ?15N-NOx values for NOx emission sources, provide a novel means for estimating contemporary and historic contributions from individual NOx emission sources to deposition.

  15. Pathways for nitrate release from an alpine watershed: determination using d15N and d18O

    USGS Publications Warehouse

    Campbell, Donald H.; Kendall, Carol; Chang, Cecily C.Y.; Silva, Steven R.; Tonnessen, Kathy A.

    2002-01-01

    [1] Snowpack, snowmelt, precipitation, surface water, and groundwater samples from the Loch Vale watershed in Colorado were analyzed for ??15N and ??18O of nitrate to determine the processes controlling the release of atmospherically deposited nitrogen from alpine and subalpine ecosystems. Although overlap was found between the ??15N(NO3) values for all water types (-4 to +6???), the ??18O(NO3) values for surface water and groundwater (+10 to +30???) were usually distinct from snowpack, snowmelt, and rainfall values (+40 to +70???). During snowmelt, ??18O(NO3) indicated that about half of the nitrate in stream water was the product of microbial nitrification; at other times that amount was greater than half. Springs emerging from talus deposits had high nitrate concentrations and a seasonal pattern in ??18O(NO3) that was similar to the pattern in the streams, indicating that shallow groundwater in talus deposits is a likely source of stream water nitrate. Only a few samples of surface water and groundwater collected during early snowmelt and large summer rain events had isotopic compositions that indicated most of the nitrate came directly from atmospheric deposition with no biological assimilation and release. This study demonstrates the value of the nitrate double-isotope technique for determining nitrogen-cycling processes and sources of nitrate in small, undisturbed watersheds that are enriched with inorganic nitrogen.

  16. Predicting the denitrification capacity of sandy aquifers from in situ measurements using push-pull 15N tracer tests

    NASA Astrophysics Data System (ADS)

    Eschenbach, W.; Well, R.; Walther, W.

    2014-12-01

    Knowledge about the spatial variability of in situ denitrification rates (Dr(in situ)) and their relation to the denitrification capacity in nitrate-contaminated aquifers is crucial to predict the development of groundwater quality. Therefore, 28 push-pull 15N tracer tests for the measurement of in situ denitrification rates were conducted in two sandy Pleistocene aquifers in Northern Germany. The 15N analysis of denitrification derived 15N labelled N2 and N2O dissolved in water samples collected during the push-pull 15N tracer tests was performed by isotope ratio mass spectrometry (IRMS) in the lab and additionally for some tracer tests online in the field with a quadrupole membrane inlet mass spectrometer (MIMS), in order to test the feasibility of on-site real-time 15N analysis. Aquifer material from the same locations and depths as the push-pull injection points was incubated and the initial and cumulative denitrification after one year of incubation (Dcum(365)) as well as the stock of reduced compounds (SRC) was compared with in situ measurements of denitrification. This was done to derive transfer functions suitable to predict Dcum(365) and SRC from Dr(in situ). Dr(in situ) ranged from 0 to 51.5 ?g N kg-1 d-1. Denitrification rates derived from on-site isotope analysis using membrane-inlet mass spectrometry satisfactorily coincided with laboratory analysis by conventional isotope ratio mass spectrometry, thus proving the feasibility of in situ analysis. Dr(in situ) was significantly higher in the sulphidic zone of both aquifers compared to the zone of non-sulphidic aquifer material. Overall, regressions between the Dcum(365) and SRC of the tested aquifer material with Dr(in situ) exhibited only a modest linear correlation for the full data set. But the predictability of Dcum(365) and SRC from Dr(in situ) data clearly increased for aquifer samples from the zone of NO3--bearing groundwater. In the NO3--free aquifer zone a lag phase of denitrification after NO3- injections was observed, which confounded the relationship between reactive compounds and in situ denitrification activity. This finding was attributed to adaptation processes in the microbial community after NO3- injections. Exemplarily, it was demonstrated that the microbial community in the NO3--free zone close below the NO3--bearing zone can be adapted to denitrification by amending wells with NO3--injections for an extended period. In situ denitrification rates were 30 to 65% higher after pre-conditioning with NO3-. Results from this study suggest that such pre-conditioning is crucial for the measurement of Dr(in situ) in deeper aquifer material from the NO3--free groundwater zone and thus for the prediction of Dcum(365) and SRC from Dr(in situ).

  17. Predicting the denitrification capacity of sandy aquifers from in situ measurements using push-pull 15N tracer tests

    NASA Astrophysics Data System (ADS)

    Eschenbach, W.; Well, R.; Walther, W.

    2015-04-01

    Knowledge about the spatial variability of in situ denitrification rates (Dr(in situ)) and their relation to the denitrification capacity in nitrate-contaminated aquifers is crucial to predict the development of groundwater quality. Therefore, 28 push-pull 15N tracer tests for the measurement of in situ denitrification rates were conducted in two sandy Pleistocene aquifers in northern Germany. The 15N analysis of denitrification-derived 15N-labelled N2 and N2O dissolved in water samples collected during the push-pull 15N tracer tests was performed using isotope ratio mass spectrometry (IRMS) in the lab and additionally for some tracer tests online in the field with a quadrupole membrane inlet mass spectrometer (MIMS) in order to test the feasibility of on-site real-time 15N analysis. Aquifer material from the same locations and depths as the push-pull injection points was incubated, and the initial and cumulative denitrification after 1 year of incubation (Dcum(365)) as well as the stock of reduced compounds (SRC) was compared with in situ measurements of denitrification. This was done to derive transfer functions suitable to predict Dcum(365) and SRC from Dr(in situ). Dr(in situ) ranged from 0 to 51.5 ?g N kg-1 d-1. Denitrification rates derived from on-site isotope analysis using MIMS satisfactorily coincided with laboratory analysis by conventional IRMS, thus proving the feasibility of in situ analysis. Dr(in situ) was significantly higher in the sulfidic zone of both aquifers compared to the zone of non-sulfidic aquifer material. Overall, regressions between the Dcum(365) and SRC of the tested aquifer material with Dr(in situ) exhibited only a modest linear correlation for the full data set. However, the predictability of Dcum(365) and SRC from Dr(in situ) data clearly increased for aquifer samples from the zone of NO3--bearing groundwater. In the NO3--free aquifer zone, a lag phase of denitrification after NO3- injections was observed, which confounded the relationship between reactive compounds and in situ denitrification activity. This finding was attributed to adaptation processes in the microbial community after NO3- injections. It was also demonstrated that the microbial community in the NO3--free zone just below the NO3--bearing zone can be adapted to denitrification by NO3- injections into wells for an extended period. In situ denitrification rates were 30 to 65 times higher after pre-conditioning with NO3-. Results from this study suggest that such pre-conditioning is crucial for the measurement of Dr(in situ) in deeper aquifer material from the NO3--free groundwater zone and thus for the prediction of Dcum(365) and SRC from Dr(in situ).

  18. Precision and sensitivity of the measurement of 15N enrichment in D-alanine from bacterial cell walls using positive/negative ion mass spectrometry

    NASA Technical Reports Server (NTRS)

    Tunlid, A.; Odham, G.; Findlay, R. H.; White, D. C.

    1985-01-01

    Sensitive detection of cellular components from specific groups of microbes can be utilized as 'signatures' in the examination of microbial consortia from soils, sediments or biofilms. Utilizing capillary gas chromatography/mass spectrometry and stereospecific derivatizing agents, D-alanine, a component localized in the prokaryotic (bacterial) cell wall, can be detected reproducibly. Enrichments of D-[15N]alanine determined in E. coli grown with [15N]ammonia can be determined with precision at 1.0 atom%. Chemical ionization with methane gas and the detection of negative ions (M - HF)- and (M - F or M + H - HF)- formed from the heptafluorobutyryl D-2 butanol ester of D-alanine allowed as little as 8 pg (90 fmol) to be detected reproducibly. This method can be utilized to define the metabolic activity in terms of 15N incorporation at the level of 10(3)-10(4) cells, as a function of the 15N-14N ratio.

  19. Mechanism of Solid-State Thermolysis of Ammonia Boraine: 15N NMR Study Using Fast Magic-Angle Spinning and Dynamic Nuclear Polarization

    SciTech Connect

    Kobayashi, Takeshi; Gupta, Shalabh; Caporini, Marc A; Pecharsky, Vitalij K; Pruski, Marek

    2014-08-28

    The solid-state thermolysis of ammonia borane (NH3BH3, AB) was explored using state-of-the-art 15N solid-state NMR spectroscopy, including 2D indirectly detected 1H{15N} heteronuclear correlation and dynamic nuclear polarization (DNP)-enhanced 15N{1H} cross-polarization experiments as well as 11B NMR. The complementary use of 15N and 11B NMR experiments, supported by density functional theory calculations of the chemical shift tensors, provided insights into the dehydrogenation mechanism of AB—insights that have not been available by 11B NMR alone. Specifically, highly branched polyaminoborane derivatives were shown to form from AB via oligomerization in the “head-to-tail” manner, which then transform directly into hexagonal boron nitride analog through the dehydrocyclization reaction, bypassing the formation of polyiminoborane.

  20. Short communication: Relationship between the efficiency of utilization of feed nitrogen and 15N enrichment in casein from lactating dairy cows.

    PubMed

    Cabrita, A R J; Fonseca, A J M; Dewhurst, R J

    2014-11-01

    The objective of the present study was to evaluate the relationship between the efficiency of conversion of feed N into milk N [N-use efficiency (NUE)] and (15)N enrichment of milk casein from lactating cows fed corn silage-based diets. Samples of feeds and milk were obtained from 3 experiments with lactating dairy cows. All diets were based on corn silage and were designed to evaluate the effects of (1) diets with different ratios of effective rumen-degradable protein to fermentable metabolizable energy (experiment 1), (2) different proportions of quickly and slowly rumen-degradable protein (experiment 2), and (3) synchronizing the availability of fermentable metabolizable energy and effective rumen-degradable protein in the rumen (experiment 3). Although no significant effect of diet on casein ?(15)N values was detected, casein was more enriched than the diet in each of the experiments. Nitrogen-use efficiency was negatively related to adjusted ?(15)N (casein ?(15)N--diet ?(15)N) for experiments 1 and 2 individually and when combining data from all 3 experiments. The relatively low values for ?(15)N suggest that these productive animals were using dietary N efficiently, with a high proportion of N going to milk protein and less to urea. The weak, although significant, relationship between NUE and adjusted ?(15)N, is consistent with relatively little variation in hepatic deamination and transamination, with variation in rumen efficiency having the predominant effect on NUE. The present study confirms the lower (15)N enrichment in protein when NUE is high and the potential to use N-isotope fractionation as a marker of NUE. PMID:25218747

  1. Nitrate removal in stream ecosystems measured by 15N addition experiments: Total uptake

    SciTech Connect

    Mulholland, Patrick J; Hall, Robert; Tank, Jennifer; Sobota, Daniel; O'Brien, Jon; Webster, Jackson; Valett, H. Maurice; Dodds, Walter; Poole, Geoff; Peterson, Chris G.; Meyer, Judy; McDowell, William; Johnson, Sherri; Hamilton, Stephen; Gregory, Stanley; Grimm, Nancy; Dahm, Cliff; Cooper, Lee W; Ashkenas, Linda; Thomas, Suzanne; Sheibley, Rich; Potter, Jody; Niederlehner, Bobbie; Johnson, Laura; Helton, Ashley; Crenshaw, Chelsea; Burgin, Amy; Bernot, Melody; Beaulieu, Jake; Arango, Clay

    2009-01-01

    We measured uptake length of {sup 15}NO{sub 3}{sup -} in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO{sub 3}{sup -} uptake length. As part of the Lotic Intersite Nitrogen Experiment II project, we chose nine streams in each region corresponding to natural (reference), suburban-urban, and agricultural land uses. Study streams spanned a range of human land use to maximize variation in NO{sub 3}{sup -} concentration, geomorphology, and metabolism. We tested a causal model predicting controls on NO{sub 3}{sup -} uptake length using structural equation modeling. The model included concomitant measurements of ecosystem metabolism, hydraulic parameters, and nitrogen concentration. We compared this structural equation model to multiple regression models which included additional biotic, catchment, and riparian variables. The structural equation model explained 79% of the variation in log uptake length (S{sub Wtot}). Uptake length increased with specific discharge (Q/w) and increasing NO{sub 3}{sup -} concentrations, showing a loss in removal efficiency in streams with high NO{sub 3}{sup -} concentration. Uptake lengths shortened with increasing gross primary production, suggesting autotrophic assimilation dominated NO{sub 3}{sup -} removal. The fraction of catchment area as agriculture and suburban-urban land use weakly predicted NO{sub 3}{sup -} uptake in bivariate regression, and did improve prediction in a set of multiple regression models. Adding land use to the structural equation model showed that land use indirectly affected NO{sub 3}{sup -} uptake lengths via directly increasing both gross primary production and NO{sub 3}{sup -} concentration. Gross primary production shortened S{sub Wtot}, while increasing NO{sub 3}{sup -} lengthened S{sub Wtot} resulting in no net effect of land use on NO{sub 3}{sup -} removal.

  2. Nitrate removal in stream ecosystems measured by 15N addition experiments: Total uptake

    USGS Publications Warehouse

    Hall, R.O., Jr.; Tank, J.L.; Sobota, D.J.; Mulholland, P.J.; O'Brien, J. M.; Dodds, W.K.; Webster, J.R.; Valett, H.M.; Poole, G.C.; Peterson, B.J.; Meyer, J.L.; McDowell, W.H.; Johnson, S.L.; Hamilton, S.K.; Grimm, N. B.; Gregory, S.V.; Dahm, C. N.; Cooper, L.W.; Ashkenas, L.R.; Thomas, S.M.; Sheibley, R.W.; Potter, J.D.; Niederlehner, B.R.; Johnson, L.T.; Helton, A.M.; Crenshaw, C.M.; Burgin, A.J.; Bernot, M.J.; Beaulieu, J.J.; Arangob, C.P.

    2009-01-01

    We measured uptake length of 15NO-3 in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO-3 uptake length. As part of the Lotic Intersite Nitrogen eXperiment II project, we chose nine streams in each region corresponding to natural (reference), suburban-urban, and agricultural land uses. Study streams spanned a range of human land use to maximize variation in NO-3 concentration, geomorphology, and metabolism. We tested a causal model predicting controls on NO-3 uptake length using structural equation modeling. The model included concomitant measurements of ecosystem metabolism, hydraulic parameters, and nitrogen concentration. We compared this structural equation model to multiple regression models which included additional biotic, catchment, and riparian variables. The structural equation model explained 79% of the variation in log uptake length (S Wtot). Uptake length increased with specific discharge (Q/w) and increasing NO-3 concentrations, showing a loss in removal efficiency in streams with high NO-3 concentration. Uptake lengths shortened with increasing gross primary production, suggesting autotrophic assimilation dominated NO-3 removal. The fraction of catchment area as agriculture and suburban-urban land use weakly predicted NO-3 uptake in bivariate regression, and did improve prediction in a set of multiple regression models. Adding land use to the structural equation model showed that land use indirectly affected NO-3 uptake lengths via directly increasing both gross primary production and NO-3 concentration. Gross primary production shortened SWtot, while increasing NO-3 lengthened SWtot resulting in no net effect of land use on NO- 3 removal. ?? 2009.

  3. Abundance, Activity, and Diversity of Ammonia-oxidizing Bacteria and Archaea in Oligotrophic Alpine Lakes of Yosemite National Park, California

    NASA Astrophysics Data System (ADS)

    Beman, J.; Hayden, C.

    2013-12-01

    Lakes play critical roles in biogeochemical cycles as integrators of carbon and nitrogen cycling across watersheds. They are also ';sentinels' that may be strongly affected by environmental change--yet the responses of lake biogeochemical processes are dictated by microbial communities that we still know little about. We quantified nitrification rates, carbon respiration rates, and the abundance and diversity of involved microbes, within lakes located along an elevational gradient in Yosemite National Park, USA. Temperature, atmospheric nitrogen (N) deposition, and exposure to UV all vary along this transect, allowing us to test how these variables may act together to influence microbial biogeochemical processes. We found surprisingly high abundances of ammonia-oxidizing bacteria (AOB)--despite low nutrient conditions and high light levels that may favor other organisms, and/or inhibit AOB. We also examined community composition and diversity of AOB and ammonia-oxidizjng archaea (AOA) using Illumina sequencing of 16S rRNA genes, and measured ammonia oxidation rates using 15N tracer. All of these data are indicative of active N cycling by a dynamic microbial community. In Yosemite and other wilderness areas, atmospheric N deposition supplies a critical nutrient that may alter naturally nutrient-poor ecosystems; in the Sierra Nevada, much of this deposition occurs in the form of ammonium, suggesting a key role for nitrification in converting deposited N into more mobile forms. Our data indicate that oligotrophic alpine lakes may be nitrification hotspots in Yosemite.

  4. Tracing nitrate in a restored river reach using 18O and 15N

    NASA Astrophysics Data System (ADS)

    Huber, Benjamin; Bernasconi, Stefano; Luster, Jörg; Graf Pannatier, Elisabeth

    2010-05-01

    Riparian zones, including alluvial forests are important for biodiversity, flood mitigation and water retention. They can remove nitrate from adjacent upland areas and atmospheric deposition by natural processes such as plant uptake, denitrification and dilution. Riparian zones have become rare since rivers have been canalized to avoid flooding. However, their area might increase in the future with the changing policy for river management in Europe and in Switzerland. A good understanding of flow paths and nitrate sources in catchments is therefore important to assess the soil influence on groundwater quality and to select the most effective land management practices (forest, agriculture, river) to ensure a sustainable water supply of good quality. Numerous studies have investigated either the chemistry of percolation waters in the root zone or the groundwater quality. However, very few have assessed the biochemical transformation of the water composition along its flow path from the soil to the aquifer and the mixing in the aquifer with water from other sources within the catchment. The proposed project aims at identifying the different sources of nitrate in soil- and groundwater (atmospheric deposition, nitrification, fertilizers and manure) and to better understand the N transformations along the flow paths from the soil to the aquifer by analyzing the oxygen and nitrogen isotopes in nitrate. The study is performed within a restored section of the river Thur (Canton Thurgau, Switzerland). It is part of the project cluster RECORD of the ETH domain, Switzerland, which was initiated to increase the mechanistic understanding of coupled hydrological and ecological processes in river corridors. Besides the sampling of river-, ground- and rainwater, soil solutions are collected in the unsaturated zone at three different depths (10, 50, 100 cm) and along two terrestrial transects following approximately the flow paths through different functional process zones (river - gravel bar with fresh fine sediments and densely colonised by canary reed grass - older overbank sediments planted with willows during recent restoration - mixed riparian hardwood forest growing on older overbank sediments - side channel). Samples were collected biweekly from May to October 2009, and will be completed by a seasonal sampling until April 2010 to assess the temporal variability of the major ion composition and the oxygen and nitrogen isotopic composition of nitrate. During floods, the observations were intensified to characterize the disturbance of the N cycle. The highest nitrate concentrations have been measured in the forest soil at 1 m depth (mean value = 612 µmol/L) exceeding the average nitrate concentration in precipitation (37 µmol/L) by a factor 17 and in ground water samples (84 µmol/L) by a factor 7. Based on these first results we assume a nitrogen saturation of the forest soil mainly driven by the high input of organic matter during flooding (silty organic carbon-rich sedimentation). Furthermore, we assume that this high nutrient availability together with the homogenous soil profile are typical for a riparian zone and favor nitrification also at greater depth, releasing nitrate into groundwater. To support these hypotheses we will complete the hydrochemical dataset by the measurement of stable isotopes of oxygen and nitrogen in nitrate.

  5. Preferential flow, nitrogen transformations and 15N balance under urine-affected areas of irrigated and non-irrigated clover-based pastures

    NASA Astrophysics Data System (ADS)

    Pakro, Naser; Dillon, Peter

    1995-12-01

    Urine-affected areas can lead to considerable losses of N by leaching, ammonia volatilisation and denitrification from dairy pastures in the southeast of South Australia. Potable groundwater supplies are considered to have become contaminated by nitrate as a result of leaching from these leguminous pastures. Dairy cow urine, labelled with 15N urea, was applied to micro-plots and mini-lysimeters installed in two adjacent irrigated (white clover-rye grass) and non-irrigated (subterranean clover-annual grasses) paddocks of a dairy farm on four occasions representing different seasonal conditions. These experiments allowed measurement of nitrogen transformations, recovery of 15N in the pasture and soil, and leaching below various depths. Gaseous losses were calculated from the nitrogen balance. The results of the four experiments showed that within a day of urine application up to 40% of the applied urinary-N was leached below a depth of 150 mm as a result of macropore flow in the irrigated paddock, and up to 24% in the non-irrigated one. After application to the irrigated paddock 17% of the urinary-N moved immediately below 300 mm but only 2% below the 450-mm depth. The urinary-N remaining in the soil was converted from urea to ammonium within a day regardless of season. Within the first 7 days of application six times more nitrate was produced in summer than in winter. This has obvious implications for leaching potential. Leaching of 15N from the top 150 mm of soil, following urine applications in all seasons, was between 41% and 62% of the applied 15N in the irrigated paddock and 25-51% in the non-irrigated paddock. However, leaching losses measured at depths of 300 or 450 mm were smaller by a factor of 2-4. The leaching loss of 15N applied in spring in both paddocks was 41% below 150 mm and 12% below 450 mm. Recovery of 15N from the soil-plant system in the 450-nm deep lysimeters was ˜60% of that applied. Estimated ammonia was ˜9% of applied 15N with no paddock or season effect. No denitrification was evident in summer nor in the non-irrigated paddock in winter but 12% of the applied 15N was lost due denitrification following winter application to the irrigated paddock. Estimated 15N loss due to denitrification from urine applied in spring was ˜13% of that applied and no difference was found between paddocks. The combination of mini-lysimeters, micro-plots and 15N measurements enabled the nitrogen budget to be determined during four periods throughout the year.

  6. Sequence-specific sup 1 H and sup 15 N resonance assignments for human dihydrofolate reductase in solution

    SciTech Connect

    Stockman, B.J.; Nirmala, N.R.; Wagner, G. ); Delcamp, T.J.; DeYarman, M.T.; Freisheim, J.H. )

    1992-01-14

    Dihydrofolate reductase is an intracellular target enzyme for folate antagonists, including the anticancer drug methotrexate. In order to design novel drugs with altered binding properties, a detailed description of protein-drug interactions in solution is desirable to understand the specificity of drug binding. As a first step in this process, heteronuclear three-dimensional NMR spectroscopy has been used to make sequential resonance assignments for more than 90% of the residues in human dihydrofolate reductase complexed with methotrexate. Uniform enrichment of the 21.5-kDa protein with {sup 15}N was required to obtain the resonance assignments via heteronuclear 3D NMR spectroscopy since homonuclear 2D spectra did not provide sufficient {sup 1}H resonance dispersion. Medium- and long-range NOE's have been used to characterize the secondary structure of the binary ligand-enzyme complex in solution.

  7. (1)H and (15)N NMR Characterization of the Amine Groups of Heparan Sulfate Related Glucosamine Monosaccharides in Aqueous Solution.

    PubMed

    Beecher, Consuelo N; Larive, Cynthia K

    2015-07-01

    Glucosamine is an important constituent of the heterogeneous glycosaminoglycans heparin and heparan sulfate occurring in N-acetylated and N-sulfated forms, and as the unmodified amine. Though the (1)H and (15)N NMR chemical shifts of N-acetyl- and N-sulfoglucosamine residues have been extensively characterized, this study provides the first direct NMR characterization of the amine groups of glucosamine and 3-O-sulfoglucosamine in aqueous solution. The solvent exchange properties of the amine protons are examined, and the possibility of a salt bridge between the sulfate and amine groups of 3-O-sulfoglucosamine is explored through (1)H NMR pKa measurements but is not supported by the experimental results. PMID:26020565

  8. LINE LISTS FOR THE A {sup 2}?-X {sup 2}?{sup +} (RED) AND B {sup 2}?{sup +}-X {sup 2}?{sup +} (VIOLET) SYSTEMS OF CN, {sup 13}C{sup 14}N, AND {sup 12}C{sup 15}N, AND APPLICATION TO ASTRONOMICAL SPECTRA

    SciTech Connect

    Sneden, Christopher; Lucatello, Sara; Ram, Ram S.; Brooke, James S. A.; Bernath, Peter E-mail: sara.lucatello@oapd.inaf.it E-mail: jsabrooke@gmail.com

    2014-10-01

    New red and violet system line lists for the CN isotopologues {sup 13}C{sup 14}N and {sup 12}C{sup 15}N have been generated. These new transition data are combined with those previously derived for {sup 12}C{sup 14}N, and applied to the determination of CNO abundances in the solar photosphere and in four red giant stars: Arcturus, the bright, very low-metallicity star HD 122563, and the carbon-enhanced metal-poor stars HD 196944 and HD 201626. When both red and violet system lines are detectable in a star, their derived N abundances are in good agreement. The mean N abundances determined in this work are also generally in accord with published values.

  9. Effect of age and ration on diet-tissue isotopic (?13C, ?15N) 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 (?(13)C) and nitrogen (?(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. ?(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 ?(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

  10. Lactoperoxidase-catalyzed oxidation of thiocyanate by hydrogen peroxide: sup 15 N nuclear magnetic resonance and optical spectral studies

    SciTech Connect

    Modi, S.; Deodhar, S.S.; Behere, D.V.; Mitra, S. )

    1991-01-01

    To establish the agent(s) responsible for the activity of the lactoperoxidase (LPO)/SCN{sup {minus}}/H{sub 2}O{sub 2} system, the oxidation of thiocyanate with hydrogen peroxide, catalyzed by lactoperoxidase, has been studied by {sup 15}N NMR and optical spectroscopy at different concentrations of thiocyanate and hydrogen peroxide and at different pHs. The formation of hypothiocyanite ion (OSCN{sup {minus}}) as one of the oxidation products correlated well with activity of the LPO/SCN{sup {minus}}/H{sub 2}O{sub 2} system and was maximum when the concentrations of the H{sub 2}O{sub 2} and SCN{sup {minus}} were nearly the same and the pH was <6.0. At (H{sub 2}O{sub 2})/(SCN{sup {minus}}) = 1, OSCN{sup {minus}} decomposed very slowly back to thiocyanate. When the ratio (H{sub 2}O{sub 2})/(SCN{sup {minus}}) was above 2, formation of CN{sup {minus}} was observed, which was confirmed by {sup 15}N NMR and also by changes in the optical spectrum of LPO. The oxidation of thiocyanate by H{sub 2}O{sub 2} in the presence of LPO does not take place at pH >8.0. Since thiocyanate does not bind to LPO above this pH, the binding of thiocyanate to LPO is considered to be prerequisite for the oxidation of thiocyanate. Maximum inhibition of oxygen uptake by Streptococcus cremoris 972 bacteria was observed when hydrogen peroxide and thiocyanate were present in equimolar amounts and the pH was below 6.0.

  11. Nitrogen Transformations in Wetland Soil Cores Measured by (sup15)N Isotope Pairing and Dilution at Four Infiltration Rates

    PubMed Central

    Stepanauskas, R.; Davidsson, E. T.; Leonardson, L.

    1996-01-01

    The effect of water infiltration rate (IR) on nitrogen cycling in a saturated wetland soil was investigated by applying a (sup15)N isotope dilution and pairing method. Water containing [(sup15)N]nitrate was infiltrated through 10-cm-long cores of sieved and homogenized soil at rates of 72, 168, 267, and 638 mm day(sup-1). Then the frequencies of (sup30)N(inf2), (sup29)N(inf2), (sup15)NO(inf3)(sup-), and (sup15)NH(inf4)(sup+) in the outflow water were measured. This method allowed simultaneous determination of nitrification, coupled and uncoupled denitrification, and nitrate assimilation rates. From 3% (at the highest IR) to 95% (at the lowest IR) of nitrate was removed from the water, mainly by denitrification. The nitrate removal was compensated for by the net release of ammonium and dissolved organic nitrogen. Lower oxygen concentrations in the soil at lower IRs led to a sharper decrease in the nitrification rate than in the ammonification rate, and, consequently, more ammonium leaked from the soil. The decreasing organic-carbon-to-nitrogen ratio (from 12.8 to 5.1) and the increasing light A(inf250)/A(inf365) ratio (from 4.5 to 5.2) indicated an increasing bioavailability of the outflowing dissolved organic matter with increasing IR. The efflux of nitrous oxide was also very sensitive to IR and increased severalfold when a zone of low oxygen concentration was close to the outlet of the soil cores. N(inf2)O then constituted 8% of the total gaseous N lost from the soil. PMID:16535352

  12. Distributions and Transformations of Natural Abundance 14C and 13C in Dissolved and Particulate Lipids in a Major Temperate Estuary

    NASA Astrophysics Data System (ADS)

    Bauer, J. E.; Canuel, E. A.; McIntosh, H.; Barrett, A.; Ferer, E.; Hossler, K.

    2013-12-01

    Limited previous studies have shown major differences in the natural 14C and 13C isotopic signatures and radiocarbon ages of different biochemical classes (e.g., proteins, carbohydrates, lipid, etc.) in river, estuarine and marine dissolved and particulate organic matter (DOM and POM, respectively). Of particular note are the much greater radiocarbon ages of lipophilic materials than other compound classes. Possible explanations for these findings include greater-than-expected inputs of fossil and highly aged lipid-containing organic matter to rivers and estuaries, extended sorptive-protection of lipophilic materials from degradation and/or lower overall reactivities of lipids vs. other major biochemical classes. We measured the Delta 14C and del 13C signatures and 14C ages of lipid classes in DOM and POM in a major temperate estuary, Delaware Bay (USA) over two years. Changes in DOM were also followed during large volume dark and light incubations to assess the microbial and photochemical reactivity and processing of DOM and lipids. Neutral lipids in DOM were among the most highly aged (> 30,000 yrs BP) of any materials measured in natural waters to date, and were significantly older than co-occurring polar lipids (~4,000-5,000 yrs BP). In general, DOM lipid ages were significantly greater than POM lipid ages across the river-estuary transect, arguing against sorptive protection as the major factor explaining greater ages of lipid than those of other compound classes. Both dark and light incubations of DOM resulted in losses of very highly aged material (30-50,000 y BP), with the remnant exported lipids being correspondingly younger. The microbial and photochemical alterations were most pronounced for lipids from freshwater reaches of the system (i.e., the Delaware River). These findings suggest that a) dissolved vs. particulate lipids have fundamentally different sources and/or physico-chemical partitioning, b) different lipid classes (e.g., neutral vs. polar) derive from uniquely aged sources and/or are processed at dissimilar rates, and c) biological and photochemical alteration and physical mixing during estuarine transport of DOM and POM can result in significant changes to the composition and ages of the exported materials. The implications of these findings for land-to-ocean fluxes of carbon and organic matter and impacts on oceanic DOM and POM are also examined.

  13. Natural 13C abundance reveals trophic status of fungi and host-origin of carbon in mycorrhizal fungi in mixed forests

    PubMed Central

    Högberg, Peter; Plamboeck, Agneta H.; Taylor, Andrew F. S.; Fransson, Petra M. A.

    1999-01-01

    Fungi play crucial roles in the biogeochemistry of terrestrial ecosystems, most notably as saprophytes decomposing organic matter and as mycorrhizal fungi enhancing plant nutrient uptake. However, a recurrent problem in fungal ecology is to establish the trophic status of species in the field. Our interpretations and conclusions are too often based on extrapolations from laboratory microcosm experiments or on anecdotal field evidence. Here, we used natural variations in stable carbon isotope ratios (?13C) as an approach to distinguish between fungal decomposers and symbiotic mycorrhizal fungal species in the rich sporocarp flora (our sample contains 135 species) of temperate forests. We also demonstrated that host-specific mycorrhizal fungi that receive C from overstorey or understorey tree species differ in their ?13C. The many promiscuous mycorrhizal fungi, associated with and connecting several tree hosts, were calculated to receive 57–100% of their C from overstorey trees. Thus, overstorey trees also support, partly or wholly, the nutrient-absorbing mycelia of their alleged competitors, the understorey trees. PMID:10411910

  14. A cross-shelf gradient in ?15N stable isotope values of krill and pollock indicates seabird foraging patterns in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Jones, Nathan M.; Hoover, Brian A.; Heppell, Scott A.; Kuletz, Kathy J.

    2014-11-01

    Concurrent measurements of predator and prey ?15N isotope values demonstrated that a cross-shelf isotopic gradient can propagate through a marine food web from forage species to top-tier predators and indicate foraging areas at a scale of tens of kilometers. We measured ?13C and ?15N in muscle tissues of thick-billed murres (Uria lomvia) and black-legged kittiwakes (Rissa tridactyla), and in whole body tissues of walleye pollock (Gadus chalcogrammus) and krill (Thysanoessa spp), sampled across the continental shelf break in the Bering Sea in 2008 and in 2009. We found significant basin-shelf differences at fine scales (<100 km) in ?15N among murres but not kittiwakes, and no such differences in ?13C in either seabird species at that scale. We then quantified the multi-trophic signal and spatial structure of a basin-shelf ?15Nitrogen gradient in the central and southern Bering Sea, and used it to contrast foraging patterns of thick-billed murres and kittiwakes on the open ocean. Seabird muscle ?15N values were compared to baselines created from measurements in krill and pollock tissues sampled concurrently throughout the study area. Krill, pollock, and murre tissues from northern, shallow, shelf habitat (<200 m) were enriched 1-2‰ in ?15N relative to samples taken from deeper habitats (>200 m) to the south and west. Krill ?15N baseline values predicted 35-42% of the variability in murre tissue values. Patterns between kittiwakes and prey were less coherent. The persistence of strong spatial autocorrelation among sample values, and a congruence of geospatial patterns in ?15N among murre and prey tissues, suggest that murres forage repeatedly in specific areas. Murre isotope values showed distinct geospatial stratification, coincident with the spatial distribution of three colonies: St. Paul, St. George, and Bogoslof. This suggests some degree of foraging habitat partitioning among colonies.

  15. Application of (13)C and (15)N stable isotope probing to characterize RDX degrading microbial communities under different electron-accepting conditions.

    PubMed

    Cho, Kun-Ching; Lee, Do Gyun; Fuller, Mark E; Hatzinger, Paul B; Condee, Charles W; Chu, Kung-Hui

    2015-10-30

    This study identified microorganisms capable of using the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) or its metabolites as carbon and/or nitrogen sources under different electron-accepting conditions using (13)C and (15)N stable isotope probing (SIP). Mesocosms were constructed using groundwater and aquifer solids from an RDX-contaminated aquifer. The mesocosms received succinate as a carbon source and one of four electron acceptors (nitrate, manganese(IV), iron(III), or sulfate) or no additional electron acceptor (to stimulate methanogenesis). When RDX degradation was observed, subsamples from each mesocosm were removed and amended with (13)C3- or ring-(15)N3-, nitro-(15)N3-, or fully-labeled (15)N6-RDX, followed by additional incubation and isolation of labeled nucleic acids. A total of fifteen 16S rRNA sequences, clustering in ?- and ?-Proteobacteria, Clostridia, and Actinobacteria, were detected in the (13)C-DNA fractions. A total of twenty seven sequences were derived from different (15)N-DNA fractions, with the sequences clustered in ?- and ?-Proteobacteria, and Clostridia. Interestingly, sequences identified as Desulfosporosinus sp. (in the Clostridia) were not only observed to incorporate the labeled (13)C or (15)N from labeled RDX, but also were detected under each of the different electron-accepting conditions. The data suggest that (13)C- and (15)N-SIP can be used to characterize microbial communities involved in RDX biodegradation, and that the dominant pathway of RDX biodegradation may differ under different electron-accepting conditions. PMID:25935409

  16. Quaternary record of aridity and mean annual precipitation based on ?15N in ratite and dromornithid eggshells from Lake Eyre, Australia.

    PubMed

    Newsome, Seth D; Miller, Gifford H; Magee, John W; Fogel, Marilyn L

    2011-12-01

    The cause(s) of the late Pleistocene megafauna extinction on the Australian continent remains largely unresolved. Unraveling climatic forcing mechanisms from direct or indirect human agents of ecosystem alteration has proven to be extremely difficult in Australia due to the lack of (1) well-dated vertebrate fossils and (2) paleo-environmental and -ecological records spanning the past approximately 100 ka when regional climatic conditions are known to have significantly varied. We have examined the nitrogen isotope composition (?(15)N) of modern emu (Dromaius novaehollandiae) eggshells collected along a precipitation gradient in Australia, along with modern climatological data and dietary ?(15)N values. We then used modern patterns to interpret an approximately 130-ka record of ?(15)N values in extant Dromaius and extinct Genyornis newtoni eggshells from Lake Eyre to obtain a novel mean annual precipitation (MAP) record for central Australia spanning the extinction interval. Our data also provide the first detailed information on the trophic ecology and environmental preferences of two closely related taxa, one extant and one extinct. Dromaius eggshell ?(15)N values show a significant shift to higher values during the Last Glacial Maximum and Holocene, which we interpret to indicate more frequent arid conditions (<200 mm MAP), relative to ?(15)N from samples just prior to the megafauna extinction. Genyornis eggshells had ?(15)N values reflecting wetter nesting conditions overall relative to those of coeval Dromaius, perhaps indicating that Genyornis was more reliant on mesic conditions. Lastly, the Dromaius eggshell record shows a significant decrease in ?(13)C values prior to the extinction, whereas the Genyornis record does not. Neither species showed a concomitant change in ?(15)N prior to the extinction, which suggests that a significant change in vegetation surrounding Lake Eyre occurred prior to an increase in local aridity. PMID:21706333

  17. ?13C and ?15N of moss Haplocladium microphyllum (Hedw.) Broth. for indicating growing environment variation and canopy retention on atmospheric nitrogen deposition

    NASA Astrophysics Data System (ADS)

    Liu, Xue-Yan; Xiao, Hua-Yun; Liu, Cong-Qiang; Li, You-Yi

    Mosses have been recognized as a useful tool for biomonitoring atmospheric deposition and assessing regional environment. This study was carried on whether the same moss growing in areas with identical regional atmospheric deposition while under different growing environments would have the same indicating signals. Similar variations in mean ?13C and ?15N signatures were found between mosses collected from five habitats, with an increasing sequence from mosses under canopies to epilithic mosses, indicating that habitats were potentially regulating ?13C and ?15N values of mosses. Dryer habitats (lower water availability) and input of more aerosol N were the main reasons for higher ?13C and ?15N values of mosses at open sites (especially for epilithic species), while more negative values of mosses under canopies were attributed to their wetter habitats and less uptake of aerosol N. Additionally, ?15N values not ?13C varied linearly with canopy thickness from -7.84‰ (1 m) to -4.71±0.7‰ (4 m), suggesting ?15N was more sensitive for indicating canopy retention. Consequently, isotopic data of mosses under different environments could not be compared for atmospheric deposition research with each other even collected at the same site. Moss ?13C and ?15N were affected not only by regional atmospheric N sources but also by their growing environments. ?15N of epilithic Haplocladium microphyllum at open sites can be taken as confident bio-indicator of atmospheric N deposition, which would deepen the application of stable nitrogen isotope of bryophytes in atmosphere-plant system study.

  18. OXYGEN ABUNDANCES IN CEPHEIDS

    SciTech Connect

    Luck, R. E.; Andrievsky, S. M.; Korotin, S. N.; Kovtyukh, V. V. E-mail: serkor@skyline.od.ua E-mail: scan@deneb1.odessa.ua

    2013-07-01

    Oxygen abundances in later-type stars, and intermediate-mass stars in particular, are usually determined from the [O I] line at 630.0 nm, and to a lesser extent, from the O I triplet at 615.7 nm. The near-IR triplets at 777.4 nm and 844.6 nm are strong in these stars and generally do not suffer from severe blending with other species. However, these latter two triplets suffer from strong non-local thermodynamic equilibrium (NLTE) effects and thus see limited use in abundance analyses. In this paper, we derive oxygen abundances in a large sample of Cepheids using the near-IR triplets from an NLTE analysis, and compare those abundances to values derived from a local thermodynamic equilibrium (LTE) analysis of the [O I] 630.0 nm line and the O I 615.7 nm triplet as well as LTE abundances for the 777.4 nm triplet. All of these lines suffer from line strength problems making them sensitive to either measurement complications (weak lines) or to line saturation difficulties (strong lines). Upon this realization, the LTE results for the [O I] lines and the O I 615.7 nm triplet are in adequate agreement with the abundance from the NLTE analysis of the near-IR triplets.

  19. 1H, 13C and 15N NMR spectral and theoretical studies of some methyl and alkylamino derivatives of 4-halopyridine N-oxides

    NASA Astrophysics Data System (ADS)

    Laihia, K.; Puszko, A.; Linnanto, J.; Kolehmainen, E.

    2006-02-01

    Nine new and three earlier known 4-halogen (Cl and Br) substituted pyridine N-oxides have been prepared and their 1H, 13C and 15N NMR chemical shifts assigned based on PFG 1H, X (X= 13C and 15N) HMQC and HMBC experiments as well as the comparison with our earlier results for substituted pyridine N-oxide derivatives. The 15N resonances of the pyridine nitrogen are 27-40 ppm more shielded in 4-halo-2-alkylamino-6-methyl-5-nitropyridine N-oxide than in parent 4-halopyridine N-oxide. According to quantum chemical ab initio HF/6-311G** calculations the amino tautomer of 4-chloro-2-methylamino-6-methyl-5-nitropyridine N-oxide is more stable than its imino form. Using B3LYP/6-311G** optimized structures both 13C and 15N shifts were calculated by density functional B3LYP/6-311G** CSGT methods for the amino and imino tautomers as well as for the dimeric structure for 4-chloro-2-methylamino-6-methyl-5-nitropyridine N-oxide. The 15N NMR and DFT calculations suggest the prevailing of the dimeric amino form for one congener, which is further supported by ESI-TOF MS data.

  20. De-excitation gamma-rays from the s-hole state in 15N associated with proton decay in 16O

    E-print Network

    K. Kobayashi; H. Akimune; H. Ejiri; H. Fujimura; M. Fujiwara; K. Hara; K. Y. Hara; T. Ishikawa; M. Itoh; Y. Itow; T. Kawabata; M. Nakamura; H. Sakaguchi; Y. Sakemi; M. Shiozawa; H. Takeda; Y. Totsuka; H. Toyokawa; M. Uchida; T. Yamada; Y. Yasuda; H. P. Yoshida; M. Yosoi; R. G. T. Zegers

    2006-04-10

    We have measured de-excitation gamma-rays from the s-hole state in 15N produced via the 16O(p,2p)15N reaction in relation to the study of the nucleon decay and the neutrino neutral-current interaction in water Cherenkov detectors. In the excitation-energy region of the s-hole state between 16 MeV and 40 MeV in 15N, the branching ratio of emitting gamma-rays with the energies at more-than-6 MeV are found to be 15.6+-1.3+0.6-1.0%. Taking into account the spectroscopic factor of the s-hole state, the total emission probability is found to be 3.1%. This is about 1/10 compared with the emission probability of the 6.32 MeV gamma-ray from the 3/2- p-hole state in 15N. Moreover, we searched for a 15.1 MeV gamma-ray from the 12C 1+ state which may be populated after the particle-decay of the s-hole state in 15N. Such a high energy gamma-ray from the hole state would provide a new method to search for mode-independent nucleon decay even if the emission probability is small. No significant signal is found within a statistical uncertainty.

  1. The light element abundances. Proceedings.

    NASA Astrophysics Data System (ADS)

    Crane, P.

    The following topics were discussed at this conference: light elements in the early universe, light elements at high redshifts, galactic evolution, helium abundances, deuterium and 3He abundances, lithium abundances, lithium isotopes, beryllium and boron.

  2. Natural Isotopic Signatures of Variations in Body Nitrogen Fluxes: A Compartmental Model Analysis

    PubMed Central

    Poupin, Nathalie; Mariotti, François; Huneau, Jean-François; Hermier, Dominique; Fouillet, Hélène

    2014-01-01

    Body tissues are generally 15N-enriched over the diet, with a discrimination factor (?15N) that varies among tissues and individuals as a function of their nutritional and physiopathological condition. However, both 15N bioaccumulation and intra- and inter-individual ?15N variations are still poorly understood, so that theoretical models are required to understand their underlying mechanisms. Using experimental ?15N measurements in rats, we developed a multi-compartmental model that provides the first detailed representation of the complex functioning of the body's ?15N system, by explicitly linking the sizes and ?15N values of 21 nitrogen pools to the rates and isotope effects of 49 nitrogen metabolic fluxes. We have shown that (i) besides urea production, several metabolic pathways (e.g., protein synthesis, amino acid intracellular metabolism, urea recycling and intestinal absorption or secretion) are most probably associated with isotope fractionation and together contribute to 15N accumulation in tissues, (ii) the ?15N of a tissue at steady-state is not affected by variations of its P turnover rate, but can vary according to the relative orientation of tissue free amino acids towards oxidation vs. protein synthesis, (iii) at the whole-body level, ?15N variations result from variations in the body partitioning of nitrogen fluxes (e.g., urea production, urea recycling and amino acid exchanges), with or without changes in nitrogen balance, (iv) any deviation from the optimal amino acid intake, in terms of both quality and quantity, causes a global rise in tissue ?15N, and (v) ?15N variations differ between tissues depending on the metabolic changes involved, which can therefore be identified using simultaneous multi-tissue ?15N measurements. This work provides proof of concept that ?15N measurements constitute a new promising tool to investigate how metabolic fluxes are nutritionally or physiopathologically reorganized or altered. The existence of such natural and interpretable isotopic biomarkers promises interesting applications in nutrition and health. PMID:25275306

  3. NMR studies on /sup 15/N-labeled creatine (CR), creatinine (CRN), phosphocreatine (PCR), and phosphocreatinine (PCRN), and on barriers to rotation in creatine kinase-bound creatine in the enzymatic reaction

    SciTech Connect

    Kenyon, G.L.; Reddick, R.E.

    1986-05-01

    Recently, the authors have synthesized /sup 15/N-2-Cr, /sup 15/N-3-Crn, /sup 15/N-2-Crn, /sup 15/N-3-PCrn, /sup 15/N-3-PCr, and /sup 15/N-2-PCr. /sup 1/H, /sup 15/N, /sup 31/P NMR data show that Crn protonates exclusively at the non-methylated ring nitrogen, confirm that PCrn is phosphorylated at the exocyclic nitrogen, and demonstrate that the /sup 31/P-/sup 15/N one-bond coupling constant in /sup 15/N-3-PCr is 18 Hz, not 3 Hz as previously reported by Brindle, K.M., Porteous, R. and Radda, G.K.. The authors have found that creatine kinase is capable of catalyzing the /sup 14/N//sup 15/N positional isotope exchange of 3-/sup 15/N-PCr in the presence of MgADP, but not in its absence. Further, the exchange does not take place when labeled PCr is resynthesized exclusively from the ternary complex E X Cr X MgATP as opposed to either E X Cr or free Cr. This suggests that the enzyme both imparts an additional rotational barrier to creatine in the complex and catalyzes the transfer of phosphoryl group with essentially complete regiospecificity.

  4. Time variations of ?15N of organic nitrogen in deep western subarctic Pacific sediment over the last 145 ka

    NASA Astrophysics Data System (ADS)

    Shigemitsu, Masahito; Watanabe, Yutaka W.; Narita, Hisashi

    2008-10-01

    We present ?15N data of organic nitrogen (?15NON) from a deep western subarctic Pacific (WSAP) sediment core over the last 145 ka. To remove the effect of inorganic nitrogen (IN) on bulk nitrogen (BN), we used the contents of IN and BN, and the isotopic ratios of IN (?15NIN) and BN (?15NBN). The contribution of IN to BN was largest 59% and ?15NIN had lower values than ?15NBN. However, the large contributions of IN to BN and the distinct isotopic values did not largely change any variability associated with ?15NON in the ?15NBN. Thus, it is possible to use ?15NBN in carrying out paleoceanographic research with ?15N at least in the open WSAP. The ?15NON values have been affected by long-term diagenesis making the values lower with depth in the sediment, but the values during less productive colder periods were generally lower compared to those during neighboring productive warmer periods. The results might indicate that ?15NON during the less productive colder periods (i.e., glacial periods) were lower than that during the productive warmer periods (i.e., interglacial periods). Previous studies have reported that the biological production in WSAP, where it is limited by iron at present, during glacial periods was at more reduced level than during interglacials despite there being more eolian dust supply during glacial periods. This indicates that the increase of biological production with enhanced iron supply derived from eolian dust during the glacial periods did not occur. If this is the case and alternatively the iron input from the subsurface layer to the surface-mixed layer by ventilation process is more important as suggested by recent works, the variations in ?15NON would be explained by the variations in the Fe/NO3- ratio in the upwelled water. Although ?15NON has been affected by long-term diagenesis in the sediment, the usage of this isotopic ratio provides new implication regarding the past ocean circulation in the open WSAP.

  5. Trophic ecology of the rocky shore community associated with the Ascophyllum nodosum zone (Roscoff, France): A ? 13C vs ? 15N investigation

    NASA Astrophysics Data System (ADS)

    Riera, Pascal; Escaravage, Carole; Leroux, Cédric

    2009-01-01

    This study aimed to characterize the structure and functioning of the benthic food web associated with the Ascophyllum nodosum zone of the rocky shore of Roscoff by using ? 13C and ? 15N. Several characteristics of the trophic ecology of the invertebrates associated with this mid-littoral habitat and which belong to different functional groups (e.g., grazers, filter-feeders, predators and omnivores) were highlighted. In particular, the filter feeder species (including mostly sponges) used macroalgae-derived organic matter as a substantial food requirement. The results also pointed out an important stable isotopes variability for strict coexisting primary consumers which: (1) is directly related to the high ? 15N range of the food sources; (2) makes it impossible to establish a unique trophic level scale based on ? 15N values, as previously done in coastal environments; and (3) points out the existence of major co-occurring trophic pathways which characterise the Ascophyllum nodosum habitat.

  6. Exogenous proline relieves growth inhibition caused by NaCl in petunia cells: Metabolism of L-( sup 15 M)-proline followed by sup 15 N NMR

    SciTech Connect

    Heyser, J.W.; Chacon, M.J. )

    1989-04-01

    Exogenous proline stimulated the growth of Petunia hybrida cells on 195 mM NaCl 10-fold as compared with cells grown on 195 mM CaCl medium minus proline. L-({sup 15}N)-proline was fed to cells growing on 0 and 195 mM CaCl, and its metabolism was followed by {sup 15}N NMR analysis of cell extracts. Total proline and amino acids were determined by ninhydrin assay. Proline and primary amino acids were easily resolved in NMR spectra and the amount of {sup 15}N-label which remained in proline was determined. Reduced catabolism of proline in cells grown on NaCl was evident. The role of exogenous proline in conferring increased NaCl tolerance in this nonhalophyte will be discussed.

  7. Soil and foliar nutrient and nitrogen isotope composition (?(15)N) at 5 years after poultry litter and green waste biochar amendment in a macadamia orchard.

    PubMed

    Bai, Shahla Hosseini; Xu, Cheng-Yuan; Xu, Zhihong; Blumfield, Timothy J; Zhao, Haitao; Wallace, Helen; Reverchon, Frédérique; Van Zwieten, Lukas

    2015-03-01

    This study aimed to evaluate the improvement in soil fertility and plant nutrient use in a macadamia orchard following biochar application. The main objectives of this study were to assess the effects of poultry litter and green waste biochar applications on nitrogen (N) cycling using N isotope composition (?(15)N) and nutrient availability in a soil-plant system at a macadamia orchard, 5 years following application. Biochar was applied at 10 t ha(-1) dry weight but concentrated within a 3-m diameter zone when trees were planted in 2007. Soil and leaf samples were collected in 2012, and both soil and foliar N isotope composition (?(15)N) and nutrient concentrations were assessed. Both soil and foliar ?(15)N increased significantly in the poultry litter biochar plots compared to the green waste biochar and control plots. A significant relationship was observed between soil and plant ?(15)N. There was no influence of either biochars on foliar total N concentrations or soil NH4 (+)-N and NO3 (-)-N, which suggested that biochar application did not pose any restriction for plant N uptake. Plant bioavailable phosphorus (P) was significantly higher in the poultry litter biochar treatment compared to the green waste biochar treatment and control. We hypothesised that the bioavailability of N and P content of poultry litter biochar may play an important role in increasing soil and plant ?(15)N and P concentrations. Biochar application affected soil-plant N cycling and there is potential to use soil and plant ?(15)N to investigate N cycling in a soil-biochar-tree crop system. The poultry litter biochar significantly increased soil fertility compared to the green waste biochar at 5 years following biochar application which makes the poultry litter a better feedstock to produce biochar compared to green waste for the tree crops. PMID:25266060

  8. The signatures of stable isotopes ? 15N and ? 13C in anadromous and non-anadromous Coilia nasus living in the Yangtze River, and the adjacent sea waters

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Tang, Wenqiao; Dong, Wenxia

    2015-12-01

    Stable isotopes are increasingly used to investigate seasonal migrations of aquatic organisms. This study employed stable isotopes ( ? 13C and ? 15N) for Coilia nasus from the lower Yangtze River and the adjacent East China Sea to distinguish different ecotypic groups, ascertain trophic nutrition positions, and reflect environmental influences on C. nasus. ? 13C signatures of C. nasus sampled from Zhoushan (ZS), Chongming (CM), and Jingjiang (JJ) waters were significantly higher than those from the Poyang Lake (PYL) ( P < 0.05). By contrast, ? 15N signatures of C. nasus in ZS, CM, and JJ groups were significantly lower than those in PYL group ( P < 0.05). Basing on ? 13C and ? 15N signatures, we could distinguish anadromous (ZS, CM, and JJ) and non-anadromous (PYL) groups. The trophic level (TL) of anadromous C. nasus ranged from 2.90 to 3.04, whereas that of non-anadromous C. nasus was 4.38. C. nasus occupied the middle and top nutrition positions in the marine and Poyang Lake food webs, respectively. C. nasus in Poyang Lake were significantly more enriched in ? 15N but depleted in ? 13C, suggesting that anthropogenic nutrient inputs and terrigenous organic carbon are important to the Poyang Lake food web. This study is the first to apply ? 15N and ? 13C to population assignment studies of C. nasus in the Yangtze River and its affiliated waters. Analysis of stable isotopes ( ? 15N and ? 13C) is shown to be a useful tool for discriminating anadromous and non-anadromous C. nasus.

  9. Nitrogen-15 labeled 5S RNA. Identification of uridine base pairs in Escherichia coli 5S RNA by sup 1 H- sup 15 N multiple quantum NMR

    SciTech Connect

    Davis, D.R.; Yamaizumi, Z.; Nishimura, S.; Poulter, C.D. )

    1989-05-02

    Escherichia coli 5S RNA labeled with {sup 15}N at N3 of the uridines was isolated from the S{phi}-187 uracil auxotroph grown on a minimal medium supplemented with (3-{sup 15}N)uracil. {sup 1}H-{sup 15}N multiple quantum filtered and 2D chemical shift correlated spectra gave resonances for the uridine imino {sup 1}H-{sup 15}N units whose protons were exchanging slowly with solvent. Peaks with {sup 1}H/{sup 15}N shifts at 11.6/154.8, 11.7/155.0, 11.8/155.5, 12.1/155.0, and 12.2/155.0 ppm were assigned to GU interactions. Two labile high-field AU resonances at 12.6/156.8 and 12.8/157.3 ppm typical of Au pairs in a shielded environment at the end of a helix were seen. Intense AU signals were also found at 13.4/158.5 and 13.6/159.2 ppm where {sup 1}H-{sup 15}N units in normal Watson-Crick pairs resonate. {sup 1}H resonances at 10.6 and 13.8 ppm were too weak, presumably because of exchange with water, to give peaks in chemical shift correlated spectra. {sup 1}H chemical shifts suggest that the resonance at 13.8 ppm represents a labile AU pair, while the resonance at 10.6 ppm is typical of a tertiary interaction between U and a tightly bound water or a phosphate residue. The NMR data are consistent with proposed secondary structures for 5S RNA.

  10. Heteronuclear NMR studies of cobalamins. 11. sup 15 N NMR studies of the axial nucleotide and amide side chains of cyanocobalamin and dicyanocobamides

    SciTech Connect

    Brown, K.; Brooks, H.B.; Xiang, Zou ); Victor, M.; Ray, A. ); Timkovich, R. )

    1990-11-28

    Spectroscopic and thermodynamic evidence for the structure of cobalamines and dicyanocobalamin (CN){sub 2}Cbl have been previously reported. The structure indicated the occurrence of the so-called tuck-in species. Further observations and characterization of the tuck-in species of (CN){sub 2}Cbl by {sup 15}N NMR spectroscopy are presented herein. These results represent the first observation of the {sup 15}N NMR spectrum of benzimidazole nucleotide of cobalamins. The first NMR observation of the amide protons of cobalamins and their connectivity to the amide nitrogens are also reported. 50 refs., 2 figs., 2 tabs.

  11. Measurement of the 20 and 90 keV Resonances in the {sup 18}O(p,{alpha}){sup 15}N Reaction via the Trojan Horse Method

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Cherubini, S.; Crucilla, V.; Gulino, M.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tumino, A.; Mukhamedzhanov, A. M.; Tribble, R. E.; Banu, A.; Goldberg, V. Z.; Tabacaru, G.; Trache, L.; Irgaziev, B.; Coc, A.

    2008-10-10

    The {sup 18}O(p,{alpha}){sup 15}N reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside asymptotic giant branch stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the {sup 18}O(p,{alpha}){sup 15}N reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances has been deduced and the change in the reaction rate evaluated.

  12. Measurement of the 20 and 90 keV resonances in the 18O(p,alpha)15N reaction via the Trojan horse method.

    PubMed

    La Cognata, M; Spitaleri, C; Mukhamedzhanov, A M; Irgaziev, B; Tribble, R E; Banu, A; Cherubini, S; Coc, A; Crucillà, V; Goldberg, V Z; Gulino, M; Kiss, G G; Lamia, L; Mrazek, J; Pizzone, R G; Puglia, S M R; Rapisarda, G G; Romano, S; Sergi, M L; Tabacaru, G; Trache, L; Trzaska, W; Tumino, A

    2008-10-10

    The 18O(p,alpha)15N reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside asymptotic giant branch stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the 18O(p,alpha)15N reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances has been deduced and the change in the reaction rate evaluated. PMID:18999593

  13. Extended quintessence and the primordial helium abundance

    SciTech Connect

    Chen, Xuelei; Scherrer, Robert J.; Steigman, Gary

    2001-06-15

    In extended quintessence models, a scalar field which couples to the curvature scalar R provides most of the energy density of the universe. We point out that such models can also lead naturally to a decrease in the primordial abundance of helium-4, relieving the tension which currently exists between the primordial helium-4 abundance inferred from observations and the amount predicted by standard big bang nucleosynthesis corresponding to the observed deuterium abundance. Using negative power-law potentials for the quintessence field, we determine the range of model parameters which can lead to an interesting reduction in the helium-4 abundance, and we show that it overlaps with the region allowed by other constraints on extended quintessence models.

  14. Extended quintessence and the primordial helium abundance

    E-print Network

    Chen, X; Steigman, G; Chen, Xuelei; Scherrer, Robert J.; Steigman, Gary

    2001-01-01

    In extended quintessence models, a scalar field which couples to the curvature scalar R provides most of the energy density of the universe. We point out that such models can also lead naturally to a decrease in the primordial abundance of