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Sample records for 15n natural abundance

  1. 15N NATURAL ABUNDANCE AND 15N LABELLING STUDIES IN FOREST ECOSYSTEMS

    EPA Science Inventory

    The relative amounts of the two stable isotopes of Nitrogen (N), 15N, and N, vary predictably in soils and plant tissues of forests and other non-cultivated ecosystems. light fractionations, or discriminations against the heavier N isotope, that can occur as N cycles through vege...

  2. Symbiotic nitrogen fixation in an arid ecosystem measured by sup 15 N natural abundance

    SciTech Connect

    Johnson, G.V. )

    1990-05-01

    Plants dependent on nitrogen fixation have an {sup 15}N abundance similar to the atmosphere, while non-nitrogen fixing plants usually are enriched in {sup 15}N and are similar to soil nitrogen values. The natural abundance of {sup 15}N in leaf tissues and soils was determined to evaluate symbiotic nitrogen fixation by several legumes and actinorhizal species in the Sevilleta Long-term Ecological Research area in central New Mexico. Comparison of {delta}{sup 15}N values for the legume Prosopis glandulosa (mesquite) to adjacent Atriplex canascens (fourwing saltbush) indicated that P. glandulosa obtained 66% of its nitrogen by fixation. The legume Hoffmanseggia jamesii was found to be utilizing soil nitrogen. The {delta}{sup 15}N values for the actinorhizal plants, Elaeagnus angustifolia and Cercocarpus montanus, while below values for soil nitrogen, did not differ from associated non-fixing plants.

  3. Atmospheric nitrogen is a reliable standard for natural 15N abundance measurements

    NASA Astrophysics Data System (ADS)

    Mariotti, Andr

    1983-06-01

    Research based on 15N stable isotope variations in natural compounds is expanding in scientific fields such as biogeochemistry (isotope fractionation effects measurements1-7), metabolic studies8,9, hydrology (research of NO3- pollution origin in aquifers10-14), agronomy (estimate of N2 symbiotic fixation by legumes15-17) and oceanography (determination of the source of sedimentary nitrogen18-21). However, intercomparison of results obtained in different laboratories is a problem due to the lack of intercalibrated standards. Atmospheric nitrogen has been chosen by many investigators as a standard20,22,23 and I present here a simple method for the preparation of atmospheric N2 as a standard for ?15N expression with excellent reproducibility. The results indicate a wide homogeneity in isotopic composition of atmospheric nitrogen which appears to be a reliable standard for 15N natural abundance measurements.

  4. ?15N natural abundance in permafrost soil indicates impact of fire on nitrogen cycle.

    PubMed

    Conen, Franz; Yakutin, Mikhail V; Puchnin, Alexander N; Leifeld, Jens; Alewell, Christine

    2011-03-15

    The impact of fire on the nitrogen (N) cycle of natural ecosystems is arguable. Here we report and interpret an observation from boreal ecosystems in the Lena River basin, Sakha Republic (Yakutia), Russian Federation. Different types of permafrost soil (0-30 cm depth) were sampled along transects (60-150 m length) from the forest edge towards the centre of four separate thermokarst depressions under grassland. The average values of ?(15)N were remarkably similar within three transects, but differed systematically between them. Three findings point towards fire being the cause of the observed pattern. First, the spatial extent of systematic differences in soil ?(15)N coincides with the extent of typical fire scars in the region. Second, soil enrichment in (15)N is larger in the proximity of settlements, where fire is generally more frequent than in more remote places. Third, there is a significant positive correlation between ?(15)N values and the ratio of black C to total N. These findings point towards fire having a marked impact on soil ?(15)N and, accordingly, on the N cycle of this cold and dry ecosystem. PMID:21290453

  5. Rapid, storm-induced changes in the natural abundance of sup 15 N in a planktonic ecosystem, Chesapeake Bay, USA

    SciTech Connect

    Montoya, J.P.; McCarthy, J.J. ); Horrigan, S.G. )

    1991-12-01

    Samples of dissolved inorganic nitrogen (DIN), particulate nitrogen (PN), and two species of zooplankton were collected during two north-south transects of the Chesapeake Bay in the autumn of 1984 (27-28 September and 3-5 October). During the first transect, the natural abundance of {sup 15}N ({delta} {sup 15}N) in the major dissolved and planktonic pools of nitrogen suggested that the {delta}{sup 15}N of PN was largely determined by isotopic fractionation during uptake of NH{sub 4}{sup +} by phytoplankton. Averaged over the transect as a whole, the {delta}{sup 15}N of the herbivorous calanoid copepod Acartia tonsa was 4.1% higher than that of the PN, while the {delta}{sup 15}N of the carnivorous ctenophore Mnemiopsis leidyi was 6.4% higher than that of the PN. In the interval between the two transects, storm-induced mixing of the water column resulted in the injection of NH{sub 4}{sup +} into the surface layer of the bay. In combination with ancillary physical, chemical, and biological data, these changes in {delta}{sup 15}N provided estimates of the isotopic fractionation factor for NH{sub 4}{sup +} uptake by phytoplankton ({alpha} = 1.0065-1.0080) as well as the turnover time of nitrogen in Acartia tonsa (6.0-9.6 days). Despite the changes in {delta}{sup 15}N observed during this cruise, the relative distribution of {sup 15}N between trophic levels was preserved: during the second transect, the difference in {delta}{sup 15}N between Acartia tonsa and PN was 3.6%, and the difference in {delta}{sup 15}N between Mnemiopsis leidyi and PN was 7.3%. These results demonstrate that the natural abundance of {sup 15}N can change dramatically on a time scale of days, and that time-series studies of the natural abundance of {sup 15}N can be a useful complement to studies using tracer additions of {sup 15}N to document nitrogen transformations in planktonic ecosystems.

  6. Plant and Soil Natural Abundance delta-15N: Indicators of Nitrogen Cycling in the Catskill Mountains, New York, USA

    NASA Astrophysics Data System (ADS)

    Templer, P. H.; Lovett, G. M.; Weathers, K.; Arthur, M. A.

    2002-12-01

    We examined the potential use of natural abundance 15N of plants and soils as an indicator of forest nitrogen (N) cycling rates within the Catskill Mountains, NY. These watersheds receive among the highest rates of N deposition in the northeastern United States and are beginning to show signs of N saturation. Many studies have shown a link between increased N cycling rates and 15N enrichment of soil and plant pools. Faster rates of N cycling processes, especially nitrification, lead to fractionation of 14/15N, creating N products that are relatively depleted in 15N. This can lead to enrichment of soil pools, as lighter 14N is lost from the system via leaching or denitrification. Plant N pools can become increasingly enriched as they take up 15N-enriched soil N. Despite similar amounts of N deposition across the Catskill Mountains, forests dominated by different tree species appear to vary in the amount of N retained or lost to nearby streams. To determine if plant and soil 15N could be used as indicators of N cycling rates, we collected foliage, wood, litterfall, organic and mineral soil, and fine roots from single species stands of American beech (Fagus grandifolia), eastern hemlock (Tsuga canadensis), red oak (Quercus rubra), and sugar maple (Acer saccharum). Fine roots and soil 15N were highest within sugar maple stands (p<0.05). Sugar maple soils also had the highest rates of net nitrification and N leaching. Therefore, soil 15N appears to correlate with forest N retention and loss. However, 15N enrichment was highest within foliage, litterfall and wood of beech trees (p<0.05). The decoupling between foliage 15N and N cycling, as well as between 15N of foliage and fine roots, illustrates that it may not be possible to use a single plant pool as an indicator of N cycling rates.

  7. Determination of the natural abundance ?15N of taurine by gas chromatography-isotope ratio measurement mass spectrometry.

    PubMed

    Tea, Illa; Antheaume, Ingrid; Besnard, Jorick; Robins, Richard J

    2010-12-15

    The measurement of the nitrogen isotope ratio of taurine (2-aminoethanesulphonic acid) in biological samples has a large number of potential applications. Taurine is a small water-soluble molecule which is notoriously difficult to analyze due to its polarity and functionality. A method is described which allows the determination of the natural abundance ?(15)N values of taurine and structural analogues, such as 3-amino-1-propanesulphonic acid (APSA), by isotope ratio mass spectrometry interfaced to gas chromatography (GC-irm-MS). The one-step protocol exploits the simultaneous derivatization of both functionalities of these aminosulphonic acids by reaction with triethylorthoacetate (TEOA). Conditions have been established which ensure quantitative reaction thus avoiding any nitrogen isotope fractionation during derivatization and workup. The differences in the ?(15)N values of derivatized and non-derivatized taurine and APSA all fall within the working range of 0.4 (-0.02 to 0.39). When applied to four sources of taurine with various ?(15)N values, the method achieved excellent reproducibility and accuracy. The optimized method enables the determination of the natural abundance ?(15)N values of taurine over the concentration range 1.5-7.84 mol.mL(-1) in samples of biological origin. PMID:21072793

  8. Estimation of biological nitrogen fixation by black locust in short-rotation forests using natural 15N abundance method

    NASA Astrophysics Data System (ADS)

    Veste, M.; Böhm, C.; Quinckenstein, A.; Freese, D.

    2012-04-01

    The importance of short rotation forests and agroforestry systems for woody biomass production for bioenergy will increase in Central Europe within the next decades. In this context, black locust (Robinia pseudoacacia) has a high growth potential especially at marginal, drought-susceptible sites such as occur in Brandenburg State (Eastern Germany). As a pioneer tree species black locust grows under a wide range of site conditions. The native range of black locust in Northern America is classified by a humid to sub-humid climate with a mean annual precipitation of 1020 to 1830 mm. In Central and Eastern Europe, this species is cultivated in a more continental climate with an annual precipitation often below 600 mm. Therefore, black locust is known to be relatively drought tolerant compared to other temperate, deciduous tree species. Because of its N2-fixation ability black locust plays generally an important role for the improvement of soil fertility. This effect is of particular interest at marginal sites in the post-mining landscapes. In order to estimate the N2-fixation potential of black locust at marginal sites leaf samples were taken from black locust trees in short rotation plantations planted between 1995 and 2007 in post-mining sites south of Cottbus (Brandenburg, NE Germany). The variation of the natural 15N abundance was measured to evaluate the biological nitrogen fixation. The nitrogen derived from the atmosphere can be calculated using a two-pool model from the quotient of the natural 15N abundances of the N2-fixing plant and the plant available soil N. Because representatively determining the plant available soil N is difficult, a non-N2-fixing reference plant growing at the same site with a similar root system and temporal N uptake pattern to the N2-fixing plant is often used. In our case we used red oak (Quercus rubra) as a reference. The average nitrogen content in the leaves of black locust ranged from 3.1% (C/N 14.8) in 15 years old trees to 3.4% (C/N 14.4) in 3 year-old trees, respectively. A higher content of nitrogen was found in leaves of re-sprouted trees with 4.3% (C/N 11.5). The estimated percentage of nitrogen derived from the atmosphere (% NdfA) in black locust was 63% - 83% compared to 56% in seabuckthorn (Hippophaë rhamnoides) and 79% in common broom (Genista scuparia). The annual leaf biomass production of black locust varied between 1325 (2 years old trees) and 2576 kg/ha a (4 years old trees). The estimated leaf nitrogen fixed by Robinia was approx. 30.5 - 59.2 kg/ha a. From the results, we can conclude that the biological nitrogen fixation by Robina is an important factor for the nitrogen balance of short-rotation plantations on nutrient poor-soils.

  9. Quantitation of metabolic compartmentation in hyperammonemic brain by natural abundance 13C-NMR detection of 13C-15N coupling patterns and isotopic shifts.

    PubMed

    Lapidot, A; Gopher, A

    1997-02-01

    In the present study, the removal of cerebral ammonia by glutamine synthetase (GS) and by reductive amination of 2-oxoglutarate by glutamate dehydrogenase in the presence of an amino donor group, was determined in hyperammonemic rabbit brains. The 15N enrichments of brain metabolite alpha-amino and amide positions of glutamine, glutamate, and alanine were determined by the indirect detection of 15N-labeled compounds of the 13C-15N spin coupling patterns of natural abundance 13C-NMR spectra. The 13C-NMR spectra of brain extracts were obtained from rabbits infused with 15NH4Cl with or without intraperitoneal infusion of the GS inhibitor, L-methionine DL-sulfoximine, in a reasonable acquisition time period. When 15NH4Cl was infused, [5-15N]glutamine and [2-15N]glutamine concentrations reached 5.2 mumol/100 mg protein and 3.6 mumol/100 mg protein, respectively, which indicates the relatively high activity of reductive amination of 2-oxoglutarate in the glutamate dehydrogenase reaction. The low concentration of [2-15N]glutamate, which is about 30% of that of [2-15N]glutamine obtained in this study, suggests that very little glutamine serves as a precursor of neuronal glutamate. When GS was inhibited by L-methionine DL-sulfoximine, a flux of 15NH4+ via the residual activity of GS was accompanied by an apparent increase of [2-15N]glutamate and [15N]alanine concentrations (2.9 mumol/100 mg protein and 1.8 mumol/100 mg protein, respectively). These findings and those obtained from 13C-13C isotopomer analysis (Lapidot and Gopher, 1994b) suggest that astrocytic 2-oxoglutarate is partially utilized (together with an amino group donor) as a precursor for neuronal glutamate in the hyperammonemic brain when GS is inhibited. This process can partly replace GS activity in metabolizing ammonia in the hyperammonemic rabbit brain. PMID:9057821

  10. 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.

  11. [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

  12. 15N natural abundance during early and late succession in a middle-European dry acidic grassland.

    PubMed

    Beyschlag, W; Hanisch, S; Friedrich, S; Jentsch, A; Werner, C

    2009-09-01

    delta(15)N and total nitrogen content of above- and belowground tissues of 13 plant species from two successional stages (open pioneer community and ruderal grass stage) of a dry acidic grassland in Southern Germany were analysed, in order to evaluate whether resource use partitioning by niche separation and N input by N(2)-fixing legumes are potential determinants for species coexistence and successional changes. Within each stage, plants from plots with different legume cover were compared. Soil inorganic N content, total plant biomass and delta(15)N values of bulk plant material were significantly lower in the pioneer stage than in the ruderal grass community. The observed delta(15)N differences were rather species- than site-specific. Within both stages, there were also species-specific differences in isotopic composition between above- and belowground plant dry matter. Species-specific delta(15)N signatures may theoretically be explained by (i) isotopic fractionation during microbial-mediated soil N transformations; (ii) isotopic fractionation during plant N uptake or fractionation during plant-mycorrhiza transfer processes; (iii) differences in metabolic pathways and isotopic fractionation within the plant; or (iv) partitioning of available N resources (or pools) among plant groups or differential use of the same resources by different species, which seems to be the most probable route in the present case. A significant influence of N(2)-fixing legumes on the N balance of the surrounding plant community was not detectable. This was confirmed by the results of an independent in situ removal experiment, showing that after 3 years there were no measurable differences in the frequency distribution between plots with and without N(2)-fixing legumes. PMID:19689779

  13. 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

  14. Application of Natural Isotopic Abundance (1)H-(13)C- and (1)H-(15)N-Correlated Two-Dimensional NMR for Evaluation of the Structure of Protein Therapeutics.

    PubMed

    Arbogast, Luke W; Brinson, Robert G; Marino, John P

    2016-01-01

    Methods for characterizing the higher-order structure of protein therapeutics are in great demand for establishing consistency in drug manufacturing, for detecting drug product variations resulting from modifications in the manufacturing process, and for comparing a biosimilar to an innovator reference product. In principle, solution NMR can provide a robust approach for characterization of the conformation(s) of protein therapeutics in formulation at atomic resolution. However, molecular weight limitations and the perceived need for stable isotope labeling have to date limited its practical applications in the biopharmaceutical industry. Advances in NMR magnet and console technologies, cryogenically cooled probes, and new rapid acquisition methodologies, particularly selective optimized flip-angle short transient pulse schemes and nonuniform sampling, have greatly ameliorated these limitations. Here, we describe experimental methods for the collection and analysis of 2D (1)H(N)-(15)N-amide- and (1)H-(13)C-methyl-correlated spectra applied to protein drug products at natural isotopic abundance, including representatives from the rapidly growing class of monoclonal antibody (mAb) therapeutics. Practical aspects of experimental setup and data acquisition for both standard and rapid acquisition NMR techniques are described. Furthermore, strategies for the statistical comparison of 2D (1)H(N)-(15)N-amide- and (1)H-(13)C-methyl-correlated spectra are detailed. PMID:26791974

  15. Sensitive measurement of NH4+ 15N/14N (delta 15NH4+) at natural abundance levels in fresh and saltwaters.

    PubMed

    Zhang, Lin; Altabet, Mark A; Wu, Taixing; Hadas, Ora

    2007-07-15

    We report a new method for determining the 15N/14N of NH4+ at natural abundance level in both freshwater and seawater. NH4+ is first quantitatively oxidized to NO2- by hypobromite (BrO-) at pH approximately 12. After the addition of sodium arsenite to consume excess BrO-, yield is verified by colorimetric NO2- determination. NO2- is further reduced to N2O using a 1:1 sodium azide and acetic acid buffer solution using previously established procedures. The product N2O is then analyzed for isotopic composition using a continuous flow purge and cryogenic trap system coupled to an isotope ratio mass spectrometer. Reliable delta 15N values (standard deviation is 0.3 per thousand or better) are obtained over an NH4+ concentration range of 0.5-10 microM using 20 mL volumes of either freshwater or seawater samples. Higher concentration samples are readily diluted to lower concentration. Preexisting NO2- is removed by treatment with sulfanilic acid. There is no interference from any of the nitrogen-containing compounds tested except short-chain aliphatic amino acids (i.e., glycine) which typically are present at very low environmental concentrations. As compared to published methods, our approach is more robust, readily applicable at low concentrations and small sample volumes, and requires less time for preparation and analysis. PMID:17567102

  16. Leaf allocation patterns and 13C and 15N natural abundances of tropical lianas (Passiflora sp.) as dependent on external climbing support.

    PubMed

    Werth, Martin; Spiegel, Ann-Kathrin; Kazda, Marian

    2013-01-01

    The transformation from self-supporting lianas to host-supported climbing lianas is related to re-allocation of biomass and nutrients among plant organs. Therefore, first, variations in leaf mass per area (LMA), leaf carbon and nitrogen allocation and (13)C and (15)N natural abundances were analysed among three tropical Passiflora species (P. edulis, P. ligularis, and P. tripartita) in a greenhouse study. Second, the influence of a climbing support was considered for each species and parameter. P. ligularis leaves were most enriched in (13)C in both treatments when compared with the other two species. This enrichment was caused by a high LMA, which is related to a high internal resistance to CO(2) diffusion. For P. edulis and P. tripartita, ?(13)C was additionally increasing with nitrogen content per area. Generally, there were no differences when considering carbon and nitrogen allocation to leaves of host-supported and self-supporting lianas. The only hints towards increased investment into leaves after the transition from self-supporting to host-supported stages could be seen by a trend to increased leaf areas and masses. ?(13)C values of supported P. edulis or P. tripartita plants were significantly increasing faster than those of non-supported plants once the interactions of leaf mass or nitrogen content per area were accounted for. Hence, the offer of a climbing support had only a minor impact on ?(13)C or ?(15)N values in vitro, but this could be different with increasing age of lianas in vivo. PMID:23134439

  17. 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 δ15N 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 δ15N 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 δ15N differed between wildfire and prescribed burn sites; the δ15N 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 δ15N 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 δ15N 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

  18. 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 δ15N 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 δ15N 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 δ15N differed between wildfire and prescribed burn sites; the δ15N 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 δ15N 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 δ15N 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

  19. Comparative structural analysis of 1-methyladenosine, 7-methylguanosine, ethenoadenosine and their protonated salts IV: 1H, 13C, and 15N NMR studies at natural isotope abundance.

    PubMed Central

    Sierzputowska-Gracz, H; Gopal, H D; Agris, P F

    1986-01-01

    The 1H, 13C, and 15N NMR spectra of neutral and protonated forms of the nucleosides 1-methyladenosine (m1A), 7-methylguanosine (m7G) and ethenoadenosine (EA), as a model compound, have been analyzed in order to assign the site of protonation in m1A and m7G. Protonation of these nucleosides occurs in the pyrimidine ring of m1A and EA and in the imidazole ring of m7G, with the charge being distributed rather than localized. Structural differences for both m1A and m7G were observed in solution and compared with those existing in the crystal state of monomers as well as in tRNA where these nucleosides occur quite often. The protonated nucleoside structures in solution compared favorably in sugar pucker and glycosidic bond conformations with x-ray crystallographic data. Methyl group carbon chemical shifts of the protonated mononucleosides corresponded to those of the methyls of the respective nucleosides in native tRNA structures. Therefore, the tRNA methyl group carbon chemical shifts are indicative of fully protonated nucleosides in the native, three dimensional structure of the nucleic acid. Images PMID:3022235

  20. Litterfall 15N abundance indicates declining soil nitrogen availability in a free-air CO2 enrichment experiment.

    PubMed

    Garten, Charles T; Iversen, Colleen M; Norby, Richard J

    2011-01-01

    Forest productivity increases in response to carbon dioxide (CO2) enrichment of the atmosphere. However, in nitrogen-limited ecosystems, increased productivity may cause a decline in soil nitrogen (N) availability and induce a negative feedback on further enhancement of forest production. In a free-air CO2 enrichment (FACE) experiment, the response of sweetgum (Liquidambar styraciflua L.) productivity to elevated CO2 concentrations [CO2] has declined over time, but documenting an associated change in soil N availability has been difficult. Here we assess the time history of soil N availability through analysis of natural 15N abundance in archived samples of freshly fallen leaf litterfall. Litterfall delta15N declined from 1998 to 2005, and the rate of decline was significantly faster in elevated [CO2]. Declining leaf litterfall delta15N is indicative of a tighter ecosystem N cycle and more limited soil N availability. By integrating N availability over time and throughout the soil profile, temporal dynamics in leaf litterfall delta15N provide a powerful tool for documenting changes in N availability and the critical feedbacks between C and N cycles that will control forest response to elevated atmospheric CO2 concentrations. PMID:21560683

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

    Context. The NO cycle takes place in the deepest layer of a H-burning core or shell, when the temperature exceeds T ? 30 106 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 red giant branch (RGB) phase of the star or to the pollution of the primordial gas by an early population of massive asymptotic giant branch (AGB) stars, whose chemical composition was modified by the hot bottom burning. In both cases, the NO cycle is responsible for the O depletion. Aims: The activation of this cycle depends on the rate of the 15N(p, ?)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. Methods: We present a new measurement of the 15N(p, ?)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 65 106 K and 780 106 K. This range includes the 15N(p, ?)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. Results: 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.

  3. 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.

  4. A new approach to determining the content and 15N abundance of total dissolved nitrogen in aqueous samples: TOC analyser-QMS coupling.

    PubMed

    Russow, R; Kupka, H J; Gtz, A; Apelt, B

    2002-12-01

    The standard method for determining the 15N abundance of total dissolved nitrogen (TDN) in aqueous samples (e.g., soil leachate, sewage, urine) is currently Kjeldahl digestion followed by steam distillation or diffusion to isolate the ammonium, and then 15N measurement using IRMS. However, this technique is both time-consuming and laborious. One way of overcoming these disadvantages could be to couple a TOC analyser to determine the TDN with a sufficient quadrupole MS to determine the 15N abundance. The high TOC analyser (Elementar Analysensysteme Hanau, Germany), which catalytically oxidises the sample's total nitrogen with a high, constant yield to nitrogen monoxide (NO), appeared particularly suitable. The quadrupole-MS ESD 100 (InProcess Instruments Bremen, Germany) proved to be a suitable mass spectrometer for the 15N determination of NO. This combination of instruments was found to provide a workable method in numerous measurements of standard and actual samples. The detection limit concerning the N amount required per analysis is 2 microg, corresponding to an N concentration of 0.7 mg/l in a maximum sample volume of 3ml. Depending on the N concentration, 15N abundances starting from 0.5 at.% can be measured with the required precision of better than 3% (simple standard deviation). For example, measuring the abundance of 0.5 at.% requires about 50 microg N, whereas for 1 at.% or more only about 5 microg N is needed per analysis. PMID:12725425

  5. [Effects of intensive agricultural production on farmland soil carbon and nitrogen contents and their delta13C and delta15N isotope abundances].

    PubMed

    Yang, Guang-Rong; Hao, Xiying; Li, Chun-Li; Wang, Zi-Lin; Li, Yong-Mei

    2012-03-01

    Farmland soil carbon and nitrogen contents under intensive agricultural production are the important indices for the assessment of the soil fertility sustainability. This paper measured the soil pH, electrical conductivity (EC), organic carbon (SOC), total nitrogen (TN), and delta13C and delta15N isotope abundances of four types of farmland, i.e., conventional rice-broad bean rotation field, open vegetable field, 3-year plastic covered greenhouse field, and > 10-year plastic covered greenhouse field, aimed to understand the effects of intensive agricultural production degree on soil properties. In the open vegetable field, 3-year plastic covered greenhouse field, and > 10-year plastic covered greenhouse field, the soil (0-20 cm) pH decreased by 1.1, 0.8, and 0.7, and the soil EC was 4.2, 4.9, and 5.2 folds of that in conventional rice-broad bean rotation field, respectively. With the increasing year of plastic covered greenhouse production, the soil SOC and TN contents decreased after an initial increase. Comparing with those under rice-broad bean rotation, the SOC content in 0-20, 20-40, 40-60, 60-80 and 80-100 cm soil layers in >10-year plastic covered greenhouse decreased by 54%, 46%, 60%, 63%, and 59%, and the TN content decreased by 53%, 53%, 71%, 82%, and 85%, respectively. Intensive agricultural production degree had significant effects on the soil SOC and TN contents and delta13C and delta15N abundances. The delta13C abundance was significantly negatively correlated with the soil SOC, suggesting that the soil delta13C abundance could be regarded as an index for the assessment of carbon cycle in farmland soils under effects of human activities. PMID:22720621

  6. Nicotine, acetanilide and urea multi-level 2H-, 13C- and 15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry.

    PubMed

    Schimmelmann, Arndt; Albertino, Andrea; Sauer, Peter E; Qi, Haiping; Molinie, Roland; Mesnard, François

    2009-11-01

    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 delta values of these reference materials should bracket the isotopic range of samples with unknown delta 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 delta13C and delta15N, 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: delta2H(nicotine) -162 to -45 per thousand, delta13C(nicotine) -30.05 to +7.72 per thousand, delta15N(nicotine) -6.03 to +33.62 per thousand; delta15N(acetanilide) +1.18 to +40.57 per thousand; delta13C(urea) -34.13 to +11.71 per thousand, delta15N(urea) +0.26 to +40.61 per thousand (recommended delta 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 delta15N values. Comparative delta13C and delta15N on-line EA-IRMS data from 14 volunteering laboratories document the usefulness and reliability of acetanilides and ureas as EA-IRMS reference materials. PMID:19844968

  7. 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 1.0221.032) 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

  8. δ 15 N constraints on long-term nitrogen balances in temperate forests

    EPA Science Inventory

    Natural abundance δ15N 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 δ15N, across nine Doug...

  9. ? 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...

  10. 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.

  11. Helium isotopic abundance variation in nature

    SciTech Connect

    Holden, N.E.

    1993-08-01

    The isotopic abundance of helium in nature has been reviewed. This atomic weight value is based on the value of helium in the atmosphere, which is invariant around the world and up to a distance of 100,000 feet. Helium does vary in natural gas, volcanic rocks and gases, ocean floor sediments, waters of various types and in radioactive minerals and ores due to {alpha} particle decay of radioactive nuclides.

  12. Uptake and Reduction of [15N]Nitrate by Intact Soybean Plants in the Dark

    PubMed Central

    Nicholas, Joseph C.; Harper, James E.

    1985-01-01

    Experiments were conducted to determine if nitrate (15N-labeled) was taken up and assimilated by intact soybean (Glycine max [L.] Merr. cv Williams) plants during extended periods of dark. Nitrate was taken up by soybean roots throughout a 12-hour dark period. The 15N-labeled nitrogen was also translocated to the plant shoots, but at a slower rate than the rate of accumulation in the roots. Much of the nitrogen (15N-labeled) was present in a nonreduced form, although considerable soluble-reduced nitrogen (15N-labeled) accumulated throughout the dark period. The 15N-labeled, soluble-reduced nitrogen fraction accounted for nearly 30% of the total 15N found in plant roots and more than 63% of the total 15N found in plant tops after 12 hours of dark. This provided evidence that intact soybean plants take up and metabolize significant quantities of nitrate to reduced N forms in the dark. In addition to nitrate influx during the dark, it was shown that there was a concomitant loss of 15N-labeled nitrogen compounds from previously 15N-labeled plants to a natural abundance 15N nutrient solution. Thus, evidence was obtained which indicated that light was not directly essential for flux and reduction of nitrate by intact soybean plants. PMID:16664059

  13. 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 μL) 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 μg 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 μg 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.

  14. 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

  15. Grass species influence on plant N uptake - Determination of atmospheric N deposition to a semi-natural peat bog site using a 15N labelling approach

    NASA Astrophysics Data System (ADS)

    Hurkuck, Miriam; Brmmer, Christian; Spott, Oliver; Flessa, Heinz; Kutsch, Werner L.

    2014-05-01

    Large areas of natural peat bogs in Northwestern Germany have been converted to arable land and were subjected to draining and peat cutting in the past. The few protected peatland areas remaining are affected by high nitrogen (N) deposition. Our study site - a moderately drained raised bog - is surrounded by highly fertilized agricultural land and livestock production. In this study, we used a 15N pool dilution technique called 'Integrated Total Nitrogen Input' (ITNI) to quantify annual deposition of atmospheric N into biomonitoring pots over a two-year period. Since it considers direct N uptake by plants, it was expected to result in higher N input than conventional methods for determination of N deposition (e.g. micrometeorological approaches, bulk N samplers). Using Lolium multiflorum and Eriophorum vaginatum as monitor plants and low, medium and high levels of fertilization, we aimed to simulate increasing N deposition to planted pots and to allocate airborne N after its uptake by the soil-plant system in aboveground biomass, roots and soil. Increasing N fertilization was positively correlated with biomass production of Eriophorum vaginatum, whereas atmospheric plant N uptake decreased and highest airborne N input of 899.8 67.4 g N d-1 pot-1 was found for low N fertilization. In contrast, Lolium multiflorum showed a clear dependency of N supply on plant N uptake and was highest (688.7 41.4 g N d-1 pot-1) for highly fertilized vegetation pots. Our results suggest that grass species respond differently to increasing N input. While crop grasses such as Lolium multiflorum take up N according to N availability, species adopted to nutrient-limited conditions like Eriophorum vaginatum show N saturation effects with increasing N supply. Total airborne N input ranged from about 24 to 66 kg N ha-1 yr-1 dependent on the used indicator plant and the amount of added fertilizer. Parallel determination of atmospheric N deposition using a micrometeorological approach complemented with bulk samplers was about 24 kg N ha-1 yr-1 during both years of experiments and was thus at the lower range of results obtained by the ITNI method. The low 15N recovery rate of about 50 % during some experiments indicated an underestimation of the applied ITNI approach, resulting in a maximum possible N uptake of twice as high as the determined N input. Most likely, the intensive agricultural land management of the surrounding areas leads to this high N deposition into the protected peatland area. As a result, increasing sensitivity of ombrotrophic vegetation with a subsequent change in plant species composition and a decline in bog-specific vegetation cannot be excluded.

  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. 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...

  18. Assessment of 15N15N16O as a tracer of stratospheric processes

    NASA Astrophysics Data System (ADS)

    Kaiser, Jan; Röckmann, Thomas; Brenninkmeijer, Carl A. M.

    2003-01-01

    Isotopic fractionation of mono-substituted N2O species by the stratospheric sinks, photolysis and reaction with O(1D), has been investigated previously by atmospheric and laboratory measurements. Here, we report on photolysis of the most abundant poly-substituted isotopologue, 15N15N16O. The associated fractionation constant equals the sum of individual fractionation constants at central and terminal nitrogen sites. Based on statistical considerations, a more general ``additivity rule'' is proposed that extends to the remaining poly-substituted N2O species and is compared to predictions from two theories. Atmospheric mixing effects do not lead to measurable deviations from random isotope distributions since variations of isotope ratios are too small. Fractionation by the O(1D) sink likely also follows the ``additivity rule''. Consequently, the stratospheric 15N15N16O abundance is expected to reflect its statistically dictated value. The value of 15N15N16O as a potential new tracer of stratospheric processes may thus be limited, but this remains to be verified by actual measurements.

  19. 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...

  20. Utility of stable isotopes ((13)C and (15)N) to demonstrate comparability between natural and experimental streams for environmental risk assessment.

    PubMed

    Morrall, Donna D; Christman, Steve C; Peterson, Bruce J; Wolheim, Wilfred M; Belanger, Scott E

    2006-09-01

    Environmental safety of contaminants sometimes requires testing at the ecosystem level. Model ecosystems can serve as a surrogate to receiving waters for the assessor. Tools to verify that model ecosystems are good surrogates for natural receiving water systems have been based on structural attributes such as taxa lists. While examining taxa lists can be useful within a geography, they are less informative when comparing across different topographical and climatic regions. This paper illustrates an alternative approach that uses natural abundance ratios of nitrogen and carbon. Comparisons were made between the Procter and Gamble Co. (P and G) Experimental Stream Facility (ESF) and the East Fork Little Miami River (EFLMR). We also conducted stable isotopes releases of nitrogen ((15)NH(4)Cl) in the ESF and EFLMR. Results from the nitrogen releases for the ESF and EFLMR were compared to each other and to stable isotope releases conducted in 9 streams as part of the Lotic Intersite Nitrogen eXperiment (LINX). Preliminary evaluations of nitrogen uptake show that the uptake rate of ammonium for the P and G experimental streams (0.019 m(-1)) is similar to uptake rates in natural streams of similar flow and fits the regression of uptake length and discharge for the LINX streams. Nutrient flow data obtained in this study in most cases verified model (SISTM) predictions. PMID:16139363

  1. 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 (318 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 Nha-1yr-1 above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.

  2. 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

  3. 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.

  4. Two abundant bioaccumulated halogenated compounds are natural products.

    PubMed

    Teuten, Emma L; Xu, Li; Reddy, Christopher M

    2005-02-11

    Methoxylated polybrominated diphenyl ethers (MeO-PBDEs) have been found bioaccumulated in the tissues of a variety of aquatic animals and at concentrations comparable to those of anthropogenic halogenated organic compounds, including polychlorinated biphenyls (PCBs). The origin of the MeO-PBDEs has been uncertain; circumstantial evidence supports a natural and/or an industrial source. By analyzing the natural abundance radiocarbon content of two MeO-PBDEs isolated from a True's beaked whale (Mesoplodon mirus), we show that these compounds were naturally produced. PMID:15705850

  5. Delta15N values of tropical savanna and monsoon forest species reflect root specialisations and soil nitrogen status.

    PubMed

    Schmidt, S; Stewart, G R

    2003-03-01

    A large number of herbaceous and woody plants from tropical woodland, savanna, and monsoon forest were analysed to determine the impact of environmental factors (nutrient and water availability, fire) and biological factors (microbial associations, systematics) on plant delta(15)N values. Foliar delta(15)N values of herbaceous and woody species were not related to growth form or phenology, but a strong relationship existed between mycorrhizal status and plant delta(15)N. In woodland and savanna, woody species with ectomycorrhizal (ECM) associations and putative N(2)-fixing species with ECM/arbuscular (AM) associations had lowest foliar delta(15)N values (1.0-0.6 per thousand ), AM species had mostly intermediate delta(15)N values (average +0.6 per thousand ), while non-mycorrhizal Proteaceae had highest delta(15)N values (+2.9 to +4.1 per thousand ). Similar differences in foliar delta(15)N were observed between AM (average 0.1 and 0.2 per thousand ) and non-mycorrhizal (average +0.8 and +0.3 per thousand ) herbaceous species in woodland and savanna. Leguminous savanna species had significantly higher leaf N contents (1.8-2.5% N) than non-fixing species (0.9-1.2% N) indicating substantial N acquisition via N(2) fixation. Monsoon forest species had similar leaf N contents (average 2.4% N) and positive delta(15)N values (+0.9 to +2.4 per thousand ). Soil nitrification and plant NO(3)(-) use was substantially higher in monsoon forest than in woodland or savanna. In the studied communities, higher soil N content and nitrification rates were associated with more positive soil delta(15)N and plant delta(15)N. In support of this notion, Ficus, a high NO(3)(-) using taxa associated with NO(3)(-) rich sites in the savanna, had the highest delta(15)N values of all AM species in the savanna. delta(15)N of xylem sap was examined as a tool for studying plant delta(15)N relations. delta(15)N of xylem sap varied seasonally and between differently aged Acacia and other savanna species. Plants from annually burnt savanna had significantly higher delta(15)N values compared to plants from less frequently burnt savanna, suggesting that foliar (15)N natural abundance could be used as marker for assessing historic fire regimes. Australian woodland and savanna species had low leaf delta(15)N and N content compared to species from equivalent African communities indicating that Australian biota are the more N depauperate. The largest differences in leaf delta(15)N occurred between the dominant ECM Australian and African savanna (miombo) species, which were depleted and enriched in (15)N, respectively. While the depleted delta(15)N of Australian ECM species are similar to those of previous reports on ECM species in natural plant communities, the (15)N-enriched delta(15)N of African ECM species represent an anomaly. PMID:12647130

  6. 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.

  7. Practical recommendations for the reduction of memory effects in compound-specific 15N/14N-ratio analysis of enriched amino acids by gas chromatography/combustion/isotope ratio mass spectrometry.

    PubMed

    Petzke, Klaus J; Metges, Cornelia C

    2012-01-30

    Gas chromatography/combustion/isotope ratio mass spectrometry (GC-C-IRMS) is a highly sensitive approach which allows the analysis of the (13)C/(12)C and (15)N/(14)N isotope composition of amino acids in the range of natural abundance or in slightly (13)C- and (15)N-enriched samples. However, the accuracy of measurements remains a permanent challenge. Here we show the effect of the presence of slightly (15)N-enriched compounds in physiological samples on the accuracy and reproducibility of (15)N-abundances of amino acids within or between analytical runs. We spiked several individual amino acids with the respective (15)N-labelled isotopomer and measured the (15)N/(14)N ratios of other amino acids in the same sample or in the following analytical runs. Intra- and inter-run memory effects can be observed in (15)N/(14)N ratios of amino acids. Sample throughput is reduced when cleaning runs using standard mixtures are required to restore initial conditions after runs of samples with (15)N-enriched analytes. Possible reasons for the observed phenomenon and its implications for work in the lower (15)N-enrichment range (<0.5 APE) are discussed and include different aspects of gas chromatography, derivatisation, and hot catalytic metal surface effects. Results need to be interpreted with caution if complex physiological samples contain (15)N-enriched amino acids beyond 500 ?(15)N (~0.18 APE). PMID:22173808

  8. Stable isotopes (?13C and ?15N) of organic matrix from coral skeleton

    PubMed Central

    Muscatine, Leonard; Goiran, Claire; Land, Lynton; Jaubert, Jean; Cuif, Jean-Pierre; Allemand, Denis

    2005-01-01

    The evolutionary success of reef-building corals in nutrient-poor tropical waters is attributed to endosymbiotic dinoflagellates. The algae release photosynthetic products to the coral animal cells, augment nutrient flux, and enhance the rate of coral calcification. Natural abundance of stable isotopes (?13C and ?18O) provides answers to modern and paleobiological questions about the effect of photosymbiosis on sources of carbon and oxygen in coral skeletal calcium carbonate. Here we compare 17 species of symbiotic and nonsymbiotic corals to determine whether evidence for photosymbiosis appears in stable isotopes (?13C and ?15N) of an organic skeletal compartment, the coral skeletal organic matrix (OM). Mean OM ?13C in symbiotic and nonsymbiotic corals was similar (-26.08 vs. -24.31), but mean OM ?15N was significantly depleted in 15N in the former (4.09) relative to the latter (12.28), indicating an effect of the algae on OM synthesis and revealing OM ?15N as a proxy for photosymbiosis. To answer an important paleobiological question about the origin of photosymbiosis in reef-building corals, we applied this proxy test to a fossil coral (Pachythecalis major) from the Triassic (240 million years ago) in which OM is preserved. Mean OM ?15N was 4.66, suggesting that P. major was photosymbiotic. The results show that symbiotic algae augment coral calcification by contributing to the synthesis of skeletal OM and that they may have done so as early as the Triassic. PMID:15671164

  9. Cereal grain, rachis and pulse seed amino acid ?15N values as indicators of plant nitrogen metabolism.

    PubMed

    Styring, Amy K; Fraser, Rebecca A; Bogaard, Amy; Evershed, Richard P

    2014-01-01

    Natural abundance ?(15)N values of plant tissue amino acids (AAs) reflect the cycling of N into and within plants, providing an opportunity to better understand environmental and anthropogenic effects on plant metabolism. In this study, the AA ?(15)N values of barley (Hordeum vulgare) and bread wheat (Triticum aestivum) grains and rachis and broad bean (Vicia faba) and pea (Pisum sativum) seeds, grown at the experimental farm stations of Rothamsted, UK and Bad Lauchstdt, Germany, were determined by GC-C-IRMS. It was found that the ?(15)N values of cereal grain and rachis AAs could be largely attributed to metabolic pathways involved in their biosynthesis and catabolism. The relative (15)N-enrichment of phenylalanine can be attributed to its involvement in the phenylpropanoid pathway and glutamate has a ?(15)N value which is an average of the other AAs due to its central role in AA-N cycling. The relative AA ?(15)N values of broad bean and pea seeds were very different from one another, providing evidence for differences in the metabolic routing of AAs to the developing seeds in these leguminous plants. This study has shown that AA ?(15)N values relate to known AA biosynthetic pathways in plants and thus have the potential to aid understanding of how various external factors, such as source of assimilated N, influence metabolic cycling of N within plants. PMID:23790569

  10. 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% ...

  11. 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.

  12. A robust method for ammonium nitrogen isotopic analysis in freshwater and seawater at natural abundance levels

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Altabet, M. A.; Wu, T.; Hadas, O.

    2006-12-01

    Natural ammonium N isotopic abundance has been increasingly used in studies of marine and freshwater biogeochemistry. However, current methods are time-consuming, subject to interference from DON, and not reliable at low concentrations. Our new method for determining the δ15N of ammonium overcomes these difficulties by employing the oxidation of ammonium to nitrite followed by conversion of nitrite to nitrous oxide. In the first step, ammonium is quantitatively oxidized by hypobromite at pH~12. After the addition of sodium arsenite to consume excess hypobromite, yield is verified by colorimetric NO2-measurement using sulfanilamide and naphthyl ethylenediamine (NED). Nitrite is further reduced to N2O by a 1:1 sodium azide and acetic acid buffer solution using previously established procedures. Buffer concentration can be varied according to sample matrix to ensure that a reaction pH between 2 and 4 is reached. The product nitrous oxide is then isotopically analyzed using a continuous flow purge and cryogenic trap system coupled to an isotope ratio mass spectrometer. Reliable δ15N values (±0.31‰) are obtained over a concentration range of 0.5 μM to 20 μM using 20 ml volumes of either fresh or seawater samples. Reagent blanks are very low, about 0.05 μM. There is no interference from any of the nitrogen containing compounds tested except short chain aliphatic amino acid (i.e. glycine) which typically are not present at sufficiently high environmental concentrations to pose a problem.

  13. 13C NMR Metabolomics: Applications at Natural Abundance

    PubMed Central

    2015-01-01

    13C NMR has many advantages for a metabolomics study, including a large spectral dispersion, narrow singlets at natural abundance, and a direct measure of the backbone structures of metabolites. However, it has not had widespread use because of its relatively low sensitivity compounded by low natural abundance. Here we demonstrate the utility of high-quality 13C NMR spectra obtained using a custom 13C-optimized probe on metabolomic mixtures. A workflow was developed to use statistical correlations between replicate 1D 13C and 1H spectra, leading to composite spin systems that can be used to search publicly available databases for compound identification. This was developed using synthetic mixtures and then applied to two biological samples, Drosophila melanogaster extracts and mouse serum. Using the synthetic mixtures we were able to obtain useful 13C13C statistical correlations from metabolites with as little as 60 nmol of material. The lower limit of 13C NMR detection under our experimental conditions is approximately 40 nmol, slightly lower than the requirement for statistical analysis. The 13C and 1H data together led to 15 matches in the database compared to just 7 using 1H alone, and the 13C correlated peak lists had far fewer false positives than the 1H generated lists. In addition, the 13C 1D data provided improved metabolite identification and separation of biologically distinct groups using multivariate statistical analysis in the D. melanogaster extracts and mouse serum. PMID:25140385

  14. 15N-Nitrate signature in low-order streams: effects of land cover and agricultural practices.

    PubMed

    Lefebvre, S; Clment, J C; Pinay, G; Thenail, C; Durand, P; Marmonier, P

    2007-12-01

    Many studies have shown that intensive agricultural practices significantly increase the nitrogen concentration of stream surface waters, but it remains difficult to identify, quantify, and differentiate between terrestrial and in-stream sources or sinks of nitrogen, and rates of transformation. In this study we used the delta15N-NO3 signature in a watershed dominated by agriculture as an integrating marker to trace (1) the effects of the land cover and agricultural practices on stream-water N concentration in the upstream area of the hydrographic network, (2) influence of the in-stream processes on the NO3-N loads at the reach scale (100 m and 1000 m long), and (3) changes in delta15N-NO3 signature with increasing stream order (from first to third order). This study suggests that land cover and fertilization practices were the major determinants of delta15N-NO3 signature in first-order streams. NO3-N loads and delta15N-NO3 signature increased with fertilization intensity. Small changes in delta15N-NO3 signature and minor inputs of groundwater were observed along both types of reaches, suggesting the NO3-N load was slightly influenced by in-stream processes. The variability of NO3-N concentrations and delta15N signature decreased with increasing stream order, and the delta15N signature was positively correlated with watershed areas devoted to crops, supporting a dominant effect of agriculture compared to the effect of in-stream N processing. Consequently, land cover and fertilization practices are integrated in the natural isotopic signal at the third-order stream scale. The GIS analysis of the land cover coupled with natural-abundance isotope signature (delta15N) represents a potential tool to evaluate the effects of agricultural practices in rural catchments and the consequences of future changes in management policies at the regional scale. PMID:18213973

  15. 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.

  16. 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 and 0.144 0.036 , 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.

  17. 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 and 0.144 0.036 , 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

  18. Human and climate impact on ?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; Bimller, Carolin; Hemp, Andreas; Samimi, Cyrus; Broesike, Christina; Hrold, 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

  19. Vertical δ13C and δ15N 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 δ13C and δ15N 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 δ13C and δ15N 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 δ13C by 1.9 ± SE 0.1 o and in δ15N by 6.0 ± 0.4 ‰˙Litter δ13C 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 δ15N values in the litter. We found a strong decrease of δ15N 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.

  20. 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 carbonphosphorus 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

  1. Diversity and abundance of phosphonate biosynthetic genes in nature.

    PubMed

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

    2013-12-17

    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

  2. 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...

  3. Increasing plant use of organic nitrogen with elevation is reflected in nitrogen uptake rates and ecosystem delta15N.

    PubMed

    Averill, Colin; Finzi, Adrien

    2011-04-01

    It is hypothesized that decreasing mean annual temperature and rates of nitrogen (N) cycling causes plants to switch from inorganic to organic forms of N as the primary mode of N nutrition. To test this hypothesis, we conducted field experiments and collected natural-abundance delta15N signatures of foliage, soils, and ectomycorrhizal sporocarps along a steep elevation-climate gradient in the White Mountains, New Hampshire, USA. Here we show that with increasing elevation organic forms of N became the dominant source of N taken up by hardwood and coniferous tree species based on dual-labeled glycine uptake analysis, an important confirmation of an emerging theory for the biogeochemistry of the N cycle. Variation in natural abundance foliar delta15N with elevation was also consistent with increasing organic N uptake, though a simple, mass balance model demonstrated that the uptake of delta15N depleted inorganic N, rather than fractionation upon transfer of N from mycorrhizal fungi, best explains variations in foliar delta15N with elevation. PMID:21661551

  4. 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 4.670.17) (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.

  5. 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.

  6. 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

    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 (?(15)N 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

  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 (δ15N) 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 (δ15N 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. The Titan 14N/ 15N and 12C/ 13C isotopic ratios in HCN from Cassini/CIRS

    NASA Astrophysics Data System (ADS)

    Vinatier, Sandrine; Bzard, 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 7512. This global result, as well as the 15 S one, envelop the value in Titan's methane ( 82.31) [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., Bzard, 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.

  9. Natural-abundance measurement of spin-spin couplings the nitrogen-15 in 1D and 2D NMR spectra by HEED pulse sequences

    NASA Astrophysics Data System (ADS)

    Kup?e, ?rik; Wrackmeyer, Bernd

    Standard pulse sequences frequently employed in NMR studies, such as INEPT, DEPT, HETCOR, phase-sensitive HETCOR, and HETCOR with nongeminal proton decoupling in the F1 dimension, have been extended by Hahn spin echoes. This enables measurement of 15NX and long-range 15N 1H couplings (together with the comparison of their relative signs) at the natural-abundance level of isotopes. The sequences were optimized and verified for X ? 13C, 29Si, 31P, 119Sn, 207Pb, using a wide variety of nitrogen compounds (e.g., pyrroles, nitro compounds, cyanides, cyanates, isocyanates, isothiocyanates, carbodiimides, silylamines, P?N, Si?N, Sn?N, and Pb?N compounds). Both positive and negative 1J( 15N13C) couplings were observed. The trends were reproduced by SCF INDO FPT calculations. Reduced coupling constants 1K119 Sn15 N and 1 K207, 15Pb 15N were all negative. Two-and four-bond 15N 1H couplings were of either sign, whereas vicinal 3J( 15N1H) couplings were always negative, showing a crude linear relationship with V 1J( 15N13C) in the compounds studied. Since the intensity of the residual signal in the HEED experiments is readily adjustable, the measurement of {15}/{14}N isotope shifts, 1? {15}/{14}N(X) , is straightforward. The 1|gD {151}/{14}N( 13C) values determined for rather different bonding situations show a complex behavior and there is no simple relation between 1? values and bond order, s character, or hybridization. A previously proposed classification of {15}/{14} ( NC) isotope shifts is inadequate in the light of the present data. The 1? {15}/{14}N values for 3P(III) chemical shifts are much larger than those for P(V) derivatives. The {15}/{14} isotope effects on 13C and 29Si chemical shifts are similar in magnitude. Unexpectedly, several Pb?N compounds showed 1? {15}/{14}N( 207Pb) values close to zero.

  10. ?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.

  11. Diversity and abundance of phosphonate biosynthetic genes in nature

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phosphonates, molecules containing direct C-P bonds, comprise a structurally diverse class of natural products with interesting and useful biological properties. Although their synthesis in protozoa was discovered more than fifty years ago, the extent and diversity of phosphonate production in natur...

  12. 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.

  13. 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.

  14. 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.

  15. Indirect Measurement of {sup 15}N(p,{alpha}){sup 12}C and {sup 18}O(p,{alpha}){sup 15}N. Applications to the AGB Star Nucleosynthesis

    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.; Tribble, R.; Al-Abdullah, T.; Banu, A.; Fu, C.; Goldberg, V.; Mukhamedzhanov, A.; Tabacaru, G.; Trache, L.

    2008-04-06

    The Trojan Horse Method has been recently applied to the study of reactions involved in fluorine nucleosynthesis inside AGB stars. Fluorine abundance is important since it allows to constrain mixing models from the comparison of the observed fluorine abundances with the ones predicted by models. Anyway direct measurements of the cross section do not extend down to the Gamow peak, which is the astrophysically relevant energy region. In particular the study focuses on the {sup 15}N(p,{alpha}){sup 12}C and the {sup 18}O(p,{alpha}){sup 15}N reactions which can influence fluorine yield as they are part of {sup 19}F production/destruction network.

  16. A 115-year ?15N record of cumulative nitrogen pollution in California serpentine grasslands

    NASA Astrophysics Data System (ADS)

    Vallano, D.; Zavaleta, E. S.

    2010-12-01

    Until the 1980s, Californias biodiverse serpentine grasslands were threatened primarily by development and protected by reserve creation. However, nitrogen (N) fertilization due to increasing fossil fuel emissions in the expanding Bay Area is thought to be contributing to rapid, recent invasion of these ecosystems by exotic annual grasses that are displacing rare and endemic serpentine species. Documenting the cumulative effects of N deposition in this ecosystem can direct policy and management actions to mitigate the role of N deposition in its transformation. Natural abundance stable isotopes of N in vegetation have been increasingly used as bio-indicators of N deposition patterns and subsequent changes to plant N cycling and assimilation. However, the long-term record of atmospheric reactive N enrichment and the resulting changes in ecosystem N dynamics have yet to be adequately reconstructed in many ecosystems. Museum archives of vascular plant tissue are valuable sources of materials to reconstruct temporal and spatial isotopic patterns of N inputs to ecosystems. Here, we present N stable isotope data from archived and current specimens of an endemic California serpentine grassland species, leather oak (Quercus durata), since 1895 across the greater San Francisco Bay region. We measured spatial and temporal trends in stable isotope composition (?15N and ?13C) and concentration (%N and %C) of historical and current samples of leather oak leaves from sites within the Bay Area, impacted by increasing development, and sites northeast of the Bay Area, with significantly lower rates of urbanization and industrialization. Specifically, we sampled dry museum and fresh leaf specimens from serpentine sites within Lake (n=27) and Santa Clara (n=30) counties dating from 1895 to 2010. Leaf ?15N values were stable from 1895 to the 1950s and then decreased strongly throughout the last 50 years as fossil fuel emissions rapidly increased in the Bay Area, indicating that N pollution is being retained in serpentine grassland ecosystems. Leaf ?15N values in the high-deposition region declined at a rate of -0.041 yr-1, while leaf ?15N values in the low-deposition region did not show a strong pattern. In both regions, leaf ?13C values declined through time as atmospheric CO2 concentrations increased in response to fossil fuel combustion (the Suess effect). Leaf %N and %C values did not present any clear patterns at sites within or outside of the Bay Area. We conclude that using natural abundance stable isotope values in leaves can indicate variation in N pollution inputs across wide spatial and temporal scales and that archived plant samples can provide valuable baselines against which to assess changes in regional N cycling and subsequent ecological impacts on vegetation.

  17. 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

  18. Differentiation of natural and synthetic phenylalanine and tyrosine through natural abundance 2H nuclear magnetic resonance.

    PubMed

    Brenna, Elisabetta; Fronza, Giovanni; Fuganti, Claudio; Pinciroli, Matteo

    2003-08-13

    The natural abundance deuterium NMR characterization of samples of the amino acids tyrosine (1) and phenylalanine (2), examined as the acetylated methyl esters 4 and 6, has been performed with the aim to identify by these means the contribution in animals of the hydroxylation of the diet l-phenylalanine (2) to the formation of l-tyrosine (1), a feature previously revealed on the same samples through the determination of the phenolic delta(18)O values. The study, which includes also the NMR examination of benzoic acid (5) from 2 and of tyrosol (7) from 1, substantially fails in providing the required information because the mode of deuterium labeling of tyrosine samples of different origins is quite similar but indicates a dramatic difference in the deuterium labeling pattern of the two amino acids 1 and 2. The most relevant variation is with regard to the deuterium enrichments at the CH(2) and CH positions, which are inverted in the two amino acids of natural derivation. Moreover, whereas the diastereotopic benzylic hydrogen atoms of l-tyrosine (1) appear to be equally deuterium enriched, in l-phenylalanine (2) the (D/H)(3)(R)() > (D/H)(3)(S)(). Similarly, benzoic acid (5) shows separate signals for the aromatic deuterium nuclei, which are quite indicative of the natural or synthetic derivation. The mode of deuterium labeling of the side chain of 1 and 2 is tentatively correlated to the different origins of the two amino acids, natural from animal sources for l-tyrosine and biotechnological probably from genetically modified microorganisms for l-phenylalanine. PMID:12903937

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

    PubMed

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

    2015-11-01

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

  20. Diversity, abundance and natural products of marine sponge-associated actinomycetes.

    PubMed

    Abdelmohsen, Usama Ramadan; Bayer, Kristina; Hentschel, Ute

    2014-03-01

    Actinomycetes are known for their unprecedented ability to produce novel lead compounds of clinical and pharmaceutical importance. This review focuses on the diversity, abundance and methodological approaches targeting marine sponge-associated actinomycetes. Additionally, novel qPCR data on actinomycete abundances in different sponge species and other environmental sources are presented. The natural products literature is covered, and we are here reporting on their chemical structures, their biological activities, as well as the source organisms from which they were isolated. PMID:24496105

  1. A study of 15N- 15N and 15N- 13C spin couplings in some 15N labeled mesoionic 1-oxa and 1-thia-2,3,4-triazoles

    NASA Astrophysics Data System (ADS)

    Ja?wi?ski, J.; Staszewska, O.; Stefaniak, L.; Webb, G. A.

    1996-03-01

    15N- 15N and 15N- 13C spin-spin couplings are reported for seven 15N labeled 1-oxa and 1-thia-2,3,4-triazoles and three sydnonimines. For the former class of compounds the spin-spin coupling data show a close similarity between the N2?N3 and N3?N4 bonds which had not previously been suspected from chemical shift measurements.

  2. 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 δ15N 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.

  3. 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.

  4. Structure, dynamics and mapping of membrane-binding residues of micelle-bound antimicrobial peptides by natural abundance (13)C NMR spectroscopy.

    PubMed

    Wang, Guangshun

    2010-02-01

    Worldwide bacterial resistance to traditional antibiotics has drawn much research attention to naturally occurring antimicrobial peptides (AMPs) owing to their potential as alternative antimicrobials. Structural studies of AMPs are essential for an in-depth understanding of their activity, mechanism of action, and in guiding peptide design. Two-dimensional solution proton NMR spectroscopy has been the major tool. In this article, we describe the applications of natural abundance (13)C NMR spectroscopy that provides complementary information to 2D (1)H NMR. The correlation of (13)Calpha secondary shifts with both 3D structure and heteronuclear (15)N NOE values indicates that natural abundance carbon chemical shifts are useful probes for backbone structure and dynamics of membrane peptides. Using human LL-37-derived peptides (GF-17, KR-12, and RI-10), as well as amphibian antimicrobial and anticancer peptide aurein 1.2 and its analog LLAA, as models, we show that the cross peak intensity plots of 2D (1)H-(13)Calpha HSQC spectra versus residue number present a wave-like pattern (HSQC wave) where key hydrophobic residues of micelle-bound peptides are located in the troughs with weaker intensities, probably due to fast exchange between the free and bound forms. In all the cases, the identification of aromatic phenylalanines as a key membrane-binding residue is consistent with previous intermolecular Phe-lipid NOE observations. Furthermore, mutation of one of the key hydrophobic residues of KR-12 to Ala significantly reduced the antibacterial activity of the peptide mutants. These results illustrate that natural abundance heteronuclear-correlated NMR spectroscopy can be utilized to probe backbone structure and dynamics, and perhaps to map key membrane-binding residues of peptides in complex with micelles. (1)H-(13)Calpha HSQC wave, along with other NMR waves such as dipolar wave and chemical shift wave, offers novel insights into peptide-membrane interactions from different angles. PMID:19682427

  5. Natural variation in stomatal abundance of Arabidopsis thaliana includes cryptic diversity for different developmental processes

    PubMed Central

    Delgado, Dolores; Alonso-Blanco, Carlos; Fenoll, Carmen; Mena, Montaa

    2011-01-01

    Background and Aims Current understanding of stomatal development in Arabidopsis thaliana is based on mutations producing aberrant, often lethal phenotypes. The aim was to discover if naturally occurring viable phenotypes would be useful for studying stomatal development in a species that enables further molecular analysis. Methods Natural variation in stomatal abundance of A. thaliana was explored in two collections comprising 62 wild accessions by surveying adaxial epidermal cell-type proportion (stomatal index) and density (stomatal and pavement cell density) traits in cotyledons and first leaves. Organ size variation was studied in a subset of accessions. For all traits, maternal effects derived from different laboratory environments were evaluated. In four selected accessions, distinct stomatal initiation processes were quantitatively analysed. Key Results and Conclusions Substantial genetic variation was found for all six stomatal abundance-related traits, which were weakly or not affected by laboratory maternal environments. Correlation analyses revealed overall relationships among all traits. Within each organ, stomatal density highly correlated with the other traits, suggesting common genetic bases. Each trait correlated between organs, supporting supra-organ control of stomatal abundance. Clustering analyses identified accessions with uncommon phenotypic patterns, suggesting differences among genetic programmes controlling the various traits. Variation was also found in organ size, which negatively correlated with cell densities in both organs and with stomatal index in the cotyledon. Relative proportions of primary and satellite lineages varied among the accessions analysed, indicating that distinct developmental components contribute to natural diversity in stomatal abundance. Accessions with similar stomatal indices showed different lineage class ratios, revealing hidden developmental phenotypes and showing that genetic determinants of primary and satellite lineage initiation combine in several ways. This first systematic, comprehensive natural variation survey for stomatal abundance in A. thaliana reveals cryptic developmental genetic variation, and provides relevant relationships amongst stomatal traits and extreme or uncommon accessions as resources for the genetic dissection of stomatal development. PMID:21447490

  6. 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).

  7. 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

  8. Natural Abundance (17)O DNP Two-Dimensional and Surface-Enhanced NMR Spectroscopy.

    PubMed

    Perras, Frdric A; Kobayashi, Takeshi; Pruski, Marek

    2015-07-01

    Due to its extremely low natural abundance and quadrupolar nature, the (17)O 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 (17)O is wrought with challenges due to the lack of spin diffusion and low polarization transfer efficiency from (1)H. Here, we demonstrate new DNP-based measurements that extend (17)O solid-state NMR beyond its current capabilities. The use of the PRESTO technique instead of conventional (1)H-(17)O cross-polarization greatly improves the sensitivity and enables the facile measurement of undistorted line shapes and two-dimensional (1)H-(17)O HETCOR NMR spectra as well as accurate internuclear distance measurements at natural abundance. This was applied for distinguishing hydrogen-bonded and lone (17)O sites on the surface of silica gel; the one-dimensional spectrum of which could not be used to extract such detail. Lastly, 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 (17)O nuclide. PMID:26098846

  9. Natural Genetic Variation Influences Protein Abundances in C. elegans Developmental Signalling Pathways

    PubMed Central

    Singh, Kapil Dev; Roschitzki, Bernd; Snoek, L. Basten; Grossmann, Jonas; Zheng, Xue; Elvin, Mark; Kamkina, Polina; Schrimpf, Sabine P.; Poulin, Gino B.; Kammenga, Jan E.; Hengartner, Michael O.

    2016-01-01

    Complex traits, including common disease-related traits, are affected by many different genes that function in multiple pathways and networks. The apoptosis, MAPK, Notch, and Wnt signalling pathways play important roles in development and disease progression. At the moment we have a poor understanding of how allelic variation affects gene expression in these pathways at the level of translation. Here we report the effect of natural genetic variation on transcript and protein abundance involved in developmental signalling pathways in Caenorhabditis elegans. We used selected reaction monitoring to analyse proteins from the abovementioned four pathways in a set of recombinant inbred lines (RILs) generated from the wild-type strains N2 (Bristol) and CB4856 (Hawaii) to enable quantitative trait locus (QTL) mapping. About half of the cases from the 44 genes tested showed a statistically significant change in protein abundance between various strains, most of these were however very weak (below 1.3-fold change). We detected a distant QTL on the left arm of chromosome II that affected protein abundance of the phosphatidylserine receptor protein PSR-1, and two separate QTLs that influenced embryonic and ionizing radiation-induced apoptosis on chromosome IV. Our results demonstrate that natural variation in C. elegans is sufficient to cause significant changes in signalling pathways both at the gene expression (transcript and protein abundance) and phenotypic levels. PMID:26985669

  10. New insights into the structure and chemistry of Titans tholins via13C and 15N solid state nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Derenne, S.; Coelho, C.; Anquetil, C.; Szopa, C.; Rahman, A. S.; McMillan, P. F.; Cor, F.; Pickard, C. J.; Quirico, E.; Bonhomme, C.

    2012-11-01

    Tholins are complex C,N-containing organic compounds produced in the laboratory. They are considered to provide materials that are analogous to those responsible for the haze observed in Titans atmosphere. These compounds present an astrobiological interest due to their ability to release amino acids upon hydrolysis. Their chemical structure has been investigated using a large number of techniques. However, to date no detailed nuclear magnetic resonance (NMR) study has been performed on these materials despite the high potential of this technique for investigating the environment of given nuclei. Here 13C and 15N solid state NMR spectroscopy was applied to obtain new insights into the chemical structure of tholins produced through plasma discharge in gaseous N2sbnd CH4 mixtures designed to simulate the atmosphere of Titan. Due to the low natural abundance of these isotopes, a 13C and 15N-enriched tholin sample was synthesized using isotopically enriched gas precursors. Various pulse sequences including 13C and 15N single pulse, 1Hsbnd 13C and 1Hsbnd 15N cross-polarisation and 1Hsbnd 15Nsbnd 13C double cross-polarisation were used. These techniques allowed complete characterisation of the chemical and structural environments of the carbon and nitrogen atoms. The NMR assignments were supplemented and confirmed by ab initio electronic structure calculations for model structures and molecular fragments.

  11. 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 mol 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

  12. 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

  13. 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

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

    PubMed

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

    2015-10-01

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

  15. 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.

  16. 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.

  17. 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 ...

  18. 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

  19. [(15)N(2)]arginine as a first potential inhaled diagnostic agent to characterize respiratory diseases.

    PubMed

    Krumbiegel, P; Denk, E; Russow, R; Rolle-Kampczyk, U; Metzner, G; Herbarth, O

    2002-01-01

    Conventional diagnosis of the pulmonary tract uses physical methods such as spirometry and oscillometry. However, the inhalation of a chemical diagnostic agent ought to provide novel ways of more specific diagnosis, for instance of inflammatory states of the bronchial and lung mucosa. The stable isotope technique using a (15)N-labeled substrate appears to be a suitable tool for this application. In a pilot study, defined amounts of the amino acid L-[guanidino-(15)N(2)]arginine monohydrochloride (aqueous solution, 20 atom % (15)N) were inhaled as a diagnostic agent by healthy volunteers and pulmonary patients suffering from asthma bronchiale. The amino acid is resorbed and partly metabolized to (15)NO. The exhaled air was collected under defined conditions in 10-L breath bags and analyzed for NO using chemiluminescence. Under standardized test conditions, healthy persons (n = 6) exhaled 0.97 +/- 0.08 micromol NO/m(3) and asthmatic patients (n = 7) 1.17 +/- 0.14 micromol NO/m(3). A better distinction was expected comparing the (15)NO exhalation. The (15)N abundance of NO was determined using a Cryotrap gas chromatography - mass spectrometry set-up. Between 30 and 80 minutes after inhaling 700 mg [(15)N]arginine, a maximum with a plateau of the (15)NO abundance was found in the exhaled air. At this time, healthy and asthmatic subjects exhibited clear differences in their exhaled (15)NO amounts. Under standardized test conditions, the healthy persons (n = 6) exhaled 102.3 +/- 6.7 nmol (15)NO/m(3), whereas asthmatic patients (n = 7) exhaled only 76.1 +/- 10.9 nmol (15)NO/m(3). It is concluded that (15)NO yielded after the inhalation of (15)N-labeled arginine could be a potential marker for demonstrating pathophysiological changes in the lung epithelium. This method could pave a new diagnostic principle of "inhalative breath test." PMID:12396247

  20. 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

  1. Understanding the Nature of Stellar Chemical Abundance Distributions in Nearby Stellar Systems

    NASA Astrophysics Data System (ADS)

    Lee, Duane

    2013-01-01

    Since stars retain, in large part, a signature of their galactic origin in their chemical compositions, we can exploit the chemical abundance distributions that we observe in stellar systems to put constraints on the nature of their progenitors. In this talk, I will discuss the results from two projects aimed at understanding how high resolution spectroscopic observations of nearby stellar systems might be interpreted. The first project presents one possible scenario for the origin of peculiar abundance distributions observed in ultra-faint dwarf satellites of the Milky Way. The second project explores to what extent the distribution of chemical elements in the stellar halo might be used to trace Galactic accretion history from its birth to the present day.

  2. Compound-specific δ15N and chlorin preservation in surface sediments of the Peru Margin with implications for ancient bulk δ15N 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 δ15N of bulk sediments (δ15Nbulk) decrease by 3‰ from the inner shelf to the upper slope (1000 m) but co-occurring compound-specific δ15N values (δ15Nchlorin) do not decrease downslope. The low variability of δ15Nchlorin values supports a single source for the chlorins, and demonstrates the recalcitrance of δ15Nchlorin 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 δ15Nbulk values are the result of degradation of a 15N-enriched fraction during downslope transport, and that δ15Nchlorin values reflect primary values; (2) that δ15Nbulk 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 δ15N record of bulk sediments and chlorins are less clear, and require more study to be thoroughly understood.

  3. Quantitative proteomics using uniform (15)N-labeling, MASCOT, and the trans-proteomic pipeline.

    PubMed

    Palmblad, Magnus; Bindschedler, Laurence V; Cramer, Rainer

    2007-10-01

    Stable isotope labeling combined with MS is a powerful method for measuring relative protein abundances, for instance, by differential metabolic labeling of some or all amino acids with (14)N and (15)N in cell culture or hydroponic media. These and most other types of quantitative proteomics experiments using high-throughput technologies, such as LC-MS/MS, generate large amounts of raw MS data. This data needs to be processed efficiently and automatically, from the mass spectrometer to statistically evaluated protein identifications and abundance ratios. This paper describes in detail an approach to the automated analysis of uniformly (14)N/(15)N-labeled proteins using MASCOT peptide identification in conjunction with the trans-proteomic pipeline (TPP) and a few scripts to integrate the analysis workflow. Two large proteomic datasets from uniformly labeled Arabidopsis thaliana were used to illustrate the analysis pipeline. The pipeline can be fully automated and uses only common or freely available software. PMID:17726679

  4. A selective 15N-to- 1H polarization transfer sequence for more sensitive detection of 15N-choline

    NASA Astrophysics Data System (ADS)

    Pfeilsticker, Jessica A.; Ollerenshaw, Jason E.; Norton, Valerie A.; Weitekamp, Daniel P.

    2010-07-01

    The sensitivity and information content of heteronuclear nuclear magnetic resonance is frequently optimized by transferring spin order of spectroscopic interest to the isotope of highest detection sensitivity prior to observation. This strategy is extended to 15N-choline using the scalar couplings to transfer polarization from 15N to choline's nine methyl 1H spins in high field. A theoretical analysis of a sequence using nonselective pulses shows that the optimal efficiency of this transfer is decreased by 62% as the result of competing 15N- 1H couplings involving choline's four methylene protons. We have therefore incorporated a frequency-selective pulse to support evolution of only the 15N-methyl 1H coupling during the transfer period. This sequence provides a 52% sensitivity enhancement over the nonselective version in in vitro experiments on a sample of thermally polarized 15N-choline in D 2O. Further, the 15N T1 of choline in D 2O was measured to be 217 38 s, the 15N-methyl 1H coupling constant was found to be 0.817 0.001 Hz, and the larger of choline's two 15N-methylene 1H coupling constants was found to be 3.64 0.01 Hz. Possible improvements and applications to in vivo experiments using long-lived hyperpolarized heteronuclear spin order are discussed.

  5. Sequential 1H and 15N NMR resonance assignment and secondary structure of ferrocytochrome c2 from Rhodobacter sphaeroides.

    PubMed

    Gans, P; Simorre, J P; Caffrey, M; Marion, D; Richaud, P; Vermglio, A

    1996-06-01

    Sequence-specific 1H and 15N assignments have been made for the amino acids of the ferrocytochrome c2 from Rhodobacter sphaeroides. Initial assignments were made by analysis of a series of homonuclear 2D COSY, TOCSY, and NOESY spectra obtained with the unlabeled protein. 2D and 3D 1H-15N correlated spectra obtained for a uniformly 15N-labeled ferrocytochrome c2 were used to confirm and extend the assignments. Partial 13C assignments have also been made by means of HSQC experiments on 13C at natural abundance, in particular for about two-thirds of the 13C alpha. Medium-range NOE connectivities, together with 3J(HC alpha NH) coupling constants, indicated the presence of five helices at positions 6-16, 60-68, 74-82, 84-91, and 109-120. No other regular secondary structure was observed. This folding is similar to that previously observed for the ferrocytochrome c2 of Rhodobacter capsulatus in solution, which exhibits approximately 50% sequence identity. Moreover, the rotation rates of the aromatic rings of phenylalanine or tyrosine, when conserved, were similar to those observed for R. capsulatus. Furthermore, C alpha H chemical shifts, which are sensitive to the secondary structure and ring current effects of the heme, appear to be very similar for the two proteins. Consequently, the solution structure of R. sphaeroides ferrocytochrome c2 appears to be very similar to that of R. capsulatus ferrocytochrome c2. These results are compared with the X-ray crystal structure of the R. sphaeroides ferrocytochrome c2. PMID:8827449

  6. Understanding the Nature of Stellar Chemical Abundance Distributions in Nearby Stellar Systems

    NASA Astrophysics Data System (ADS)

    Lee, Duane Morris

    Since stars retain signatures of their galactic origins in their chemical compositions, we can exploit the chemical abundance distributions that we observe in stellar systems to put constraints on the nature of their progenitors. In this thesis, I present results from three projects aimed at understanding how high resolution spectroscopic observations of nearby stellar systems might be interpreted. The first project presents one possible explanation for the origin of peculiar abundance distributions observed in ultra-faint dwarf satellites of the Milky Way. The second project explores to what extent the distribution of chemical elements in the stellar halo can be used to trace Galactic accretion history from the birth of the Galaxy to the present day. Finally, a third project focuses on developing an input optimization algorithm for the second project to produce better estimates of halo accretion histories. In conclusion, I propose some other new ways to use statistical models and techniques along with chemical abundance distribution data to uncover galactic histories.

  7. An Evolutionary Perspective on Global Vegetation \\delta15N Co-variance With Average Annual Precipitation

    NASA Astrophysics Data System (ADS)

    Sechrest, W.; Billmark, K. A.; Shields, L. G.; Swap, R. J.; Macko, S. A.

    2001-12-01

    Recent regional transect studies have shown a significant negative relationship between the \\delta15N value of vegetation and the mean annual precipitation. \\delta15N values provide an indication of the source nitrogen utilized by the plant owing to differential fractionations from biological and chemical processes. The fact that such a relationship exists across a variety of systems is surprising given the abundance of global plant species and the complexity of the nitrogen cycle. This observed pattern suggests that there may be some biological controls on plant utilization of nitrogen that are linked to available water. After observing this relationship in samples collected as a part of the Southern African Regional Science Initiative (SAFARI 2000), we have found that this relationship holds on a global scale for published values of \\delta15N. The critical question remains; is this relationship a result of shared characteristics of related species, or more broadly is there an evolutionary reason for this relationship? Since the \\delta15N values varied with rainfall, we hypothesize that the photosynthetic pathway utilized by plants play a role in this pattern. For example, plants that have evolved C4 metabolism, in other words, plants that have evolved mechanisms to allow for utilization of nutrients in a way more independent of available water than their C3 metabolizing counterparts, may exhibit different \\delta15N with respect to our original relationship. The data collected in conjunction with SAFARI 2000 confirms this hypothesis and as a result we have used modern phylogenetic techniques (using taxonomic information as a surrogate for true phylogenetic relationships between the included plant species) to test whether evolutionary history has played a role in the \\delta15N pattern. We anticipate that by using multidisciplinary tools this study will greatly advance ongoing research in the areas of nitrogen dynamics and vegetative biogeochemical cycling.

  8. 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.

  9. 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

  10. 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

  11. NMR resonance assignments for sparsely 15N labeled proteins.

    PubMed

    Feng, Lianmei; Lee, Han-Seung; Prestegard, James H

    2007-07-01

    For larger proteins, and proteins not amenable to expression in bacterial hosts, it is difficult to deduce structures using NMR methods based on uniform (13)C, (15)N isotopic labeling and observation of just nuclear Overhauser effects (NOEs). In these cases, sparse labeling with selected (15)N enriched amino acids and extraction of a wider variety of backbone-centered structural constraints is providing an alternate approach. A limitation, however, is the absence of resonance assignment strategies that work without uniform (15)N, (13)C labeling or preparation of numerous samples labeled with pairs of isotopically labeled amino acids. In this paper an approach applicable to a single sample prepared with sparse (15)N labeling in selected amino acids is presented. It relies on correlation of amide proton exchange rates, measured from data on the intact protein and on digested and sequenced peptides. Application is illustrated using the carbohydrate binding protein, Galectin-3. Limitations and future applications are discussed. PMID:17487550

  12. /sup 15/N chemical shifts and /sup 13/C-/sup 15/N coupling constants of cyanide complexes

    SciTech Connect

    Sano, M.; Yoshikawa, Y.; Yamatera, H.

    1982-06-01

    The /sup 13/C NMR spectra of cyanide complexes have been reported by Hirota et al. and Pesek et al. However, no reports have been found concerning /sup 15/N resonances and C-N nuclear-spin coupling constants, J/sub C-N/, for cyano complexes. The data for J/sub C-N/ and /sup 15/N and /sup 13/C resonances may be useful in interpreting the NMR spetra of cyano complexes. In this paper, we present the results of the /sup 13/C and /sup 15/N spectra for 13 cyano complexes.

  13. δ15N 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 δ15N 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 δ15N 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 δ15N 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 δ15N value is not affected by fasting and therefore cannot be used as an indicatior of nutritive condition. PMID:24651388

  14. 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

  15. Organic vs. Conventional Grassland Management: Do 15N and 13C Isotopic Signatures of Hay and Soil Samples Differ?

    PubMed Central

    Klaus, Valentin H.; Hölzel, Norbert; Prati, Daniel; Schmitt, Barbara; Schöning, Ingo; Schrumpf, Marion; Fischer, Markus; Kleinebecker, Till

    2013-01-01

    Distinguishing organic and conventional products is a major issue of food security and authenticity. Previous studies successfully used stable isotopes to separate organic and conventional products, but up to now, this approach was not tested for organic grassland hay and soil. Moreover, isotopic abundances could be a powerful tool to elucidate differences in ecosystem functioning and driving mechanisms of element cycling in organic and conventional management systems. Here, we studied the δ15N and δ13C isotopic composition of soil and hay samples of 21 organic and 34 conventional grasslands in two German regions. We also used Δδ15N15N plant - δ15N soil) to characterize nitrogen dynamics. In order to detect temporal trends, isotopic abundances in organic grasslands were related to the time since certification. Furthermore, discriminant analysis was used to test whether the respective management type can be deduced from observed isotopic abundances. Isotopic analyses revealed no significant differences in δ13C in hay and δ15N in both soil and hay between management types, but showed that δ13C abundances were significantly lower in soil of organic compared to conventional grasslands. Δδ15N values implied that management types did not substantially differ in nitrogen cycling. Only δ13C in soil and hay showed significant negative relationships with the time since certification. Thus, our result suggest that organic grasslands suffered less from drought stress compared to conventional grasslands most likely due to a benefit of higher plant species richness, as previously shown by manipulative biodiversity experiments. Finally, it was possible to correctly classify about two third of the samples according to their management using isotopic abundances in soil and hay. However, as more than half of the organic samples were incorrectly classified, we infer that more research is needed to improve this approach before it can be efficiently used in practice. PMID:24205126

  16. Organic vs. conventional grassland management: do (15)N and (13)C isotopic signatures of hay and soil samples differ?

    PubMed

    Klaus, Valentin H; Hlzel, Norbert; Prati, Daniel; Schmitt, Barbara; Schning, Ingo; Schrumpf, Marion; Fischer, Markus; Kleinebecker, Till

    2013-01-01

    Distinguishing organic and conventional products is a major issue of food security and authenticity. Previous studies successfully used stable isotopes to separate organic and conventional products, but up to now, this approach was not tested for organic grassland hay and soil. Moreover, isotopic abundances could be a powerful tool to elucidate differences in ecosystem functioning and driving mechanisms of element cycling in organic and conventional management systems. Here, we studied the ?(15)N and ?(13)C isotopic composition of soil and hay samples of 21 organic and 34 conventional grasslands in two German regions. We also used ??(15)N (?(15)N plant - ?(15)N soil) to characterize nitrogen dynamics. In order to detect temporal trends, isotopic abundances in organic grasslands were related to the time since certification. Furthermore, discriminant analysis was used to test whether the respective management type can be deduced from observed isotopic abundances. Isotopic analyses revealed no significant differences in ?(13)C in hay and ?(15)N in both soil and hay between management types, but showed that ?(13)C abundances were significantly lower in soil of organic compared to conventional grasslands. ??(15)N values implied that management types did not substantially differ in nitrogen cycling. Only ?(13)C in soil and hay showed significant negative relationships with the time since certification. Thus, our result suggest that organic grasslands suffered less from drought stress compared to conventional grasslands most likely due to a benefit of higher plant species richness, as previously shown by manipulative biodiversity experiments. Finally, it was possible to correctly classify about two third of the samples according to their management using isotopic abundances in soil and hay. However, as more than half of the organic samples were incorrectly classified, we infer that more research is needed to improve this approach before it can be efficiently used in practice. PMID:24205126

  17. Phenylalanine ?15N in Paleo Archives as a New Proxy for ?15N of Exported Primary Production

    NASA Astrophysics Data System (ADS)

    McCarthy, M.; Batista, F. C.; Vokhshoori, N. L.; Brown, J. T.; Guilderson, T. P.; Ravelo, A. C.; Sherwood, O.

    2012-12-01

    Compound-specific isotope analysis of individual amino acids (CSI-AA) is emerging as a powerful new tool for studying the paleo nitrogen cycle. Because most detrital organic nitrogen is composed of amino acids, CSI-AA can reveal the mechanistic basis for organic nitrogen diagenesis, preserve a record of past food web structure, and potentially reconstruct the ?15N values of past nitrate and primary production. Within the commonly measured amino acids, the ?15N value of phenylalanine (Phe) appears uniquely promising as a new proxy that reflects the nitrogen isotopic value of the original source. Phe ?15N values remain almost unchanged with trophic transfer through food webs, and also during at least the initial stages of organic matter degradation. Here we synthesize results from both bio-archives and recent sediments, which together suggest that at least in Holocene archives the Phe ?15N value does in fact record the average inorganic nitrogen ?15N value at the base of planktonic food webs. However, several important unknowns also remain. These include the extent of variation in amino acid isotopic fractionation patterns in phylogenetically distinct algal groups. The stability of Phe ?15N values in older sediments where organic matter has undergone extensive diagenesis is also an important research area, which may ultimately establish the temporal limit for application of this approach to study past geological epochs. Together, however, results to date suggest that of Phe ?15N values in paleo archives represent a novel molecular-level proxy which is not tied to any specific organism or group, but rather can provide an integrated estimate of ?15N value of exported primary production.

  18. Natural abundance variations in stable isotopes and their potential uses in animal physiological ecology.

    PubMed

    Gannes, L Z; Martínez del Rio, C; Koch, P

    1998-03-01

    Chemical, biological, and physical processes lead to distinctive "isotopic signatures" in biological materials that allow tracing of the origins of organic substances. Isotopic variation has been extensively used by plant physiological ecologists and by paleontologists, and recently ecologists have adopted the use of stable isotopes to measure ecosystem patterns and processes. To date, animal physiological ecologists have made minimal use of naturally occurring stable isotopes as tracers. Here we provide a review of the current and potential uses of naturally occurring stable isotopes in animal physiological ecology. We outline the physical and biological processes that lead to variation in isotopic abundance in plants and animals. We summarize current uses in animal physiological ecology (diet reconstruction and animal movement patterns), and suggest areas of research where the use of stable isotopes can be fruitful (protein balance and turnover and the allocation of dietary nutrients). We argue that animal physiological ecologists can benefit from including the measurement of naturally occurring stable isotopes in their battery of techniques. We also argue that animal physiologists can make an important contribution to the emerging field of stable isotopes in biology by testing experimentally the plethora of assumptions upon which the techniques rely. PMID:9683412

  19. Natural abundance carbon 13 nuclear magnetic resonance spectroscopy of antifreeze glycoproteins

    SciTech Connect

    Berman, E.; Allerhand, A.; DeVries, A.L.

    1980-05-25

    Natural abundance /sup 13/C NMR spectroscopy (at 67.9 MHz) is used to study an aqueous solution of the antifreeze glycoproteins 3 to 6 from the Antarctic cod. Assignments of resonances to specific carbons of the known Ala-Ala-(..beta..Gal-(1 ..-->.. 3)-..cap alpha..-N-acetylgalactosamine)Thr repeating unit are presented. Some of the carbons of the proline residues of glycoprotein 6 are also identified. Spin-lattice relaxation times (at 30/sup 0/C), linewidths (at 35/sup 0/C), nuclear Overhauser enhancements (at 35/sup 0/C), and the temperature dependence of chemical shifts (from 0/sup 0/ to 75/sup 0/C) all strongly suggest that these antifreeze glycoproteins are predominantly or entirely flexible random coil polymers.

  20. 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

  1. 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

  2. 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 SrCl26H2O, SrBr26H2O, 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

  3. 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 Strmgren 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 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.

  4. Apparent /sup 15/N uptake kinetics resulting from remineralization

    SciTech Connect

    Garside, C.

    1984-01-01

    A computer model of phytoplankton /sup 15/N uptake experiments in which simultaneous remineralization is occurring is used to demonstrate potential artifacts if remineralization is disregarded. In simulated experiments where a range of /sup 15/N additions is made to obtain population kinetics, apparent kinetics can be obtained where none exist. Similarly, in simulated experiments where samples are taken over time there is an apparent decrease in uptake rates with time, which, when plotted against inferred changes in substrate concentration, gives rise to similar kinetics. In actual experiments, such artifacts could obscure any real kinetics and would lead to erroneous estimates of population characteristics.

  5. The 15N NMR powder spectra of semicrystalline nylon 6

    NASA Astrophysics Data System (ADS)

    Powell, Douglas G.; Mathias, Lon J.

    1989-05-01

    The solid state 15N NMR chemical shift anisotropy (CSA) spectra of nylon 6 is reported. Nylon 6 (20 percent 15N enriched) was prepared by anionic polymerization of isotopically enriched caprolactam. The samples observed were prepared by extraction with methanol to remove unreacted caprolactam, then either annealed to promote crystallization or artificially plasticized by immersion in molten caprolactam. The anisotropic linewidth was approximately 200 ppm, intermediate between the range reported for sp2 and sp3 hybridized nitrogens and consistent with the partial double-bond character of the carbon-nitrogen bond in amides.

  6. Refining cotton-wick method for 15N plant labelling.

    NASA Astrophysics Data System (ADS)

    Fustec, Jolle; Mahieu, Stphanie

    2010-05-01

    The symbiosis Fabaceae/Rhizobiaceae plays a critical role in the nitrogen cycle. It gives the plant the ability to fix high amounts of atmospheric N. A part of this N can be transferred to the soil via rhizodeposition. The contribution of Fabaceae to the soil N pool is difficult to measure, since it is necessary for assessing N benefits for other crops, for soil biological activity, and for reducing water pollution in sustainable agriculture (Fustec, 2009). The aim of this study was to test and improve the reliability of the 15N cotton-wick method for measuring the soil N derived from plant rhizodeposition (Mahieu et al., 2007). The effects of the concentration of the 15N-urea labelling solution and of the feeding frequency (continuous or pulses) on the assessment of nitrogen rhizodeposition were studied in two greenhouse experiments using the field pea (Pisum sativum L.) and the non-nodulating isoline P2. The plant parts and the soil were prepared for 15N:14N measurements for assessing N rhizodeposition (Mahieu et al., 2009). The fraction of plants' belowground nitrogen allocated to rhizodeposition in both Frisson pea and P2 was 20 to more than 50% higher when plants were labelled continuously than when they were labelled using fortnightly pulses. Our results suggested that when 15N root enrichment was high, nitrogen rhizodeposition was underestimated only for plants that were 15N-fed by fortnightly pulses, and not in plants 15N-fed continuously. This phenomenon was especially observed for plants relying on symbiotic N fixation for N acquisition; it may be linked to the concentration of the labelling solution. In conclusion, N rhizodeposition assessment was strongly influenced by the 15N-feeding frequency and the concentration of the labelling solution. The estimation of N rhizodeposition was more reliable when plants were labelled continuously with a dilute solution of 15N urea. Fustec et al. 2009. Agron. Sustain. Dev., DOI 10.1051/agro/2009003, in press. Mahieu et al. 2007. Plant Soil 295, 193-205. Mahieu et al. 2009. Soil Biol. Biochem. 41, 2236-2243.

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

    PubMed

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

    2015-02-01

    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 × 10(7) 16S rRNA gene copies cm(-3)) than the high-salinity marine sites from BR and AR (2 × 10(4)-2 × 10(7) and 4 × 10(6)-2 × 10(7) 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

  8. 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

  9. Two new organic reference materials for δ13C and δ15N measurements and a new value for the δ13C of NBS 22 oil

    USGS Publications Warehouse

    Qi, Haiping; Coplen, Tyler B.; Geilmann, Heike; Brand, Willi A.; Bohlke, John Karl

    2003-01-01

    Analytical grade L-glutamic acid is chemically stable and has a C/N mole ratio of 5, which is close to that of many of natural biological materials, such as blood and animal tissue. Two L-glutamic acid reference materials with substantially different 13C and 15N abundances have been prepared for use as organic reference materials for C and N isotopic measurements. USGS40 is analytical grade L-glutamic acid and has a δ13C value of −26.24‰ relative to VPDB and a δ15N value of −4.52‰ relative to N2 in air. USGS41 was prepared by dissolving analytical grade L-glutamic acid with L-glutamic acid enriched in 13C and 15N. USGS41 has a δ13C value of +37.76‰ and a δ15N value of +47.57‰. The δ13C and δ15N values of both materials were measured against the international reference materials NBS 19 calcium carbonate (δ13C = +1.95‰), L-SVEC lithium carbonate (δ13C = −46.48‰), IAEA-N-1 ammonium sulfate (δ15N = 0.43‰), and USGS32 potassium nitrate (δ15N = 180‰) by on-line combustion continuous-flow and off-line dual-inlet isotope-ratio mass spectrometry. Both USGS40 and USGS41 are isotopically homogeneous; reproducibility of δ13C is better than 0.13‰, and that of δ15N is better than 0.13‰ in 100-μg amounts. These two isotopic reference materials can be used for (i) calibrating local laboratory reference materials, and (ii) quantifying drift with time, mass-dependent fractionations, and isotope-ratio-scale contraction in the isotopic analysis of various biological materials. Isotopic results presented in this paper yield a δ13C value for NBS 22 oil of −29.91‰, in contrast to the commonly accepted value of −29.78‰ for which off-line blank corrections probably have not been quantified satisfactorily.

  10. 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.

  11. Natural Abundance 17O Nuclear Magnetic Resonance and Computational Modeling Studies of Lithium Based Liquid Electrolytes

    SciTech Connect

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

    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.

  12. Characterization of Stratum Corneum Molecular Dynamics by Natural-Abundance 13C Solid-State NMR

    PubMed Central

    Bouwstra, Joke A.; Sparr, Emma; Topgaard, Daniel

    2013-01-01

    Despite the enormous potential for pharmaceutical applications, there is still a lack of understanding of the molecular details that can contribute to increased permeability of the stratum corneum (SC). To investigate the influence of hydration and heating on the SC, we record the natural-abundance 13C signal of SC using polarization transfer solid-state NMR methods. Resonance lines from all major SC components are assigned. Comparison of the signal intensities obtained with the INEPT and CP pulse sequences gives information on the molecular dynamics of SC components. The majority of the lipids are rigid at 32C, and those lipids co-exist with a small pool of mobile lipids. The ratio between mobile and rigid lipids increases with hydration. An abrupt change of keratin filament dynamics occurs at RH?=?8085%, from completely rigid to a structure with rigid backbone and mobile protruding terminals. Heating has a strong effect on the lipid mobility, but only a weak influence on the keratin filaments. The results provide novel molecular insight into how the SC constituents are affected by hydration and heating, and improve the understanding of enhanced SC permeability, which is associated with elevated temperatures and SC hydration. PMID:23626744

  13. 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.

  14. 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.

  15. 14N15N detectability in Plutos atmosphere

    NASA Astrophysics Data System (ADS)

    Jessup, Kandis Lea; Gladstone, G. R.; Heays, A. N.; Gibson, S. T.; Lewis, B. R.; Stark, G.

    2013-11-01

    Based on the vapor pressure behavior of Plutos surface ices, Plutos atmosphere is expected to be predominantly composed of N2 gas. Measurement of the N2 isotopologue 15N/14N ratio within Plutos atmosphere would provide important clues to the evolution of Plutos atmosphere from the time of formation to its present state. The most straightforward way of determining the N2 isotopologue 15N/14N ratio in Plutos atmosphere is via spectroscopic observation of the 14N15N gas species. Recent calculations of the 80-100 nm absorption behavior of the 14N2 and 14N15N isotopologues by Heays et al. (Heays, A.N. et al. [2011]. J. Chem. Phys. 135, 244301), Lewis et al. (Lewis, B.R., Heays, A.N., Gibson, S.T., Lefebvre-Brion, H., Lefebvre, R. [2008]. J. Chem. Phys. 129, 164306); Lewis et al. (Lewis, B.R., Gibson, S.T., Zhang, W., Lefebvre-Brion, H., Robbe, J.-M. [2005]. J. Chem. Phys. 122, 144302), and Haverd et al. (Haverd, V.E., Lewis, B.R., Gibson, S.T., Stark, G. [2005]. J. Chem. Phys. 123, 214304) show that the peak magnitudes of the 14N2 and 14N15N absorption bandhead cross-sections are similar, but the locations of the bandhead peaks are offset in wavelength by ?0.05-0.1 nm. These offsets make the segregation of the 14N2 and 14N15N absorption signatures possible. We use the most recent N2 isotopologue absorption cross-section calculations and the atmospheric density profiles resulting from photochemical models developed by Krasnopolsky and Cruickshank (Krasnopolsky, V.A., Cruickshank, D.P. [1999]. J. Geophys. Res. 104, 21979-21996) to predict the level of solar light that will be transmitted through Plutos atmosphere as a function of altitude during a Pluto solar occultation. We characterize the detectability of the isotopic absorption signature per altitude assuming 14N15N concentrations ranging from 0.1% to 2% of the 14N2 density and instrumental spectral resolutions ranging from 0.01 to 0.3 nm. Our simulations indicate that optical depth of unity is attained in the key 14N15N absorption bands located between 85 and 90 nm at altitudes ?1100-1600 km above Plutos surface. Additionally, an 14N15N isotope absorption depth ?4-15% is predicted for observations obtained at these altitudes at a spectral resolution of ?0.2-0.3 nm, if the N2 isotopologue 15N/14N percent ratio is comparable to the 0.37-0.6% ratio observed at Earth, Titan and Mars. If we presume that the predicted absorption depth must be at least 25% greater than the expected observational uncertainty, then it follows that a statistically significant detection of these signatures and constraint of the N2 isotopologue 14N/15N ratio within Plutos atmosphere will be possible if the attainable observational signal-to noise (S/N) ratio is ?9. The New Horizons (NH) Mission will be able to obtain high S/N, 0.27-0.35 nm full-width half-max 80-100 nm spectral observations of Pluto using the Alice spectrograph. Based on the NH/Alice specifications we have simulated 0.3 nm spectral resolution solar occultation spectra for the 1100-1600 km altitude range, assuming 30 s integration times. These simulations indicate that NH/Alice will obtain spectral observations within this altitude range with a S/N ratio ?25-50, and should be able to reliably detect the 14N15N gas absorption signature between 85 and 90 nm if the 14N15N concentration is ?0.3% or greater. This, additionally, implies that the non-detection of the 14N15N species in the 1100-1600 km range by NH/Alice may be used to reliably establish an upper limit to the N2 isotopologue 15N/14N ratio within Plutos atmosphere. Similar results may be derived from 0.2 to 0.3 nm spectral resolution observations of any other N2-rich Solar System or exoplanet atmosphere, provided the observations are attained with similar S/N levels.

  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. Population abundance of Frankliniella occidentalis (Thysanoptera: Thripidae) and natural enemies on plant hosts in central Chile.

    PubMed

    Ripa, Renato; Funderburk, Joe; Rodriguez, Fernando; Espinoza, Fernanda; Mound, Laurence

    2009-04-01

    Populations of the invasive Frankliniella occidentalis (Pergande) are serious pests of agricultural crops in the Aconcagua Valley of central Chile. An extensive survey was conducted of 55 plant species in 24 families to identify plant hosts of F. occidentalis and to determine its relative abundance on each host during each season. A more intensive study was conducted on selected plant species serving as reproductive hosts to determine the population dynamics of F. occidentalis and to evaluate the potential importance of Orius species and other natural enemies for controlling F. occidentalis. Adults of F. occidentalis were active during each season of the year inhabiting the flowers of 91% of the sampled plant species in 22 families, and 86% of these plant species in 19 families served as reproductive hosts. The number of host plant species used was greatest in the spring and least in the winter. All of the hosts except Medicago sativa L. were used only when flowering. Populations of F. occidentalis were significantly aggregated in M. sativa in the terminal buds over the leaves when the host was not flowering, and in the flowers, followed by the terminal buds, followed by the leaves when the host was flowering. Larvae were 1.3-2.3 times more abundant on dates when M. sativa was flowering. There were no identifiable patterns in plant hosts based on endemicity or plant family. Most of the plant species used by F. occidentalis were inferior quality hosts where populations either declined or were stable. Populations of F. occidentalis on low-quality hosts generally escaped predation by Orius species and competition by other species of thrips. Only 25% of the food hosts and 28% of the reproductive hosts for F. occidentalis in the extensive survey, respectively, were host plants for Orius. Parasitoids and other predators were not found to be important in suppressing thrips on any of the plant hosts. Populations of F. occidentalis increased on only a few hosts, including M. sativa and Sisymbrium officinale L. Scop. These apparently are major sources of F. occidentalis adults invading crops. We conclude that F. occidentalis is established in central Chile and that it has replaced and possibly displaced the native Frankliniella australis (Morgan) as the most common thrips species. PMID:19389281

  18. 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

  19. 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

  20. 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)

  1. 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

  2. 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.

  3. Mapping monoclonal antibody structure by 2D 13C NMR at natural abundance.

    PubMed

    Arbogast, Luke W; Brinson, Robert G; Marino, John P

    2015-04-01

    Monoclonal antibodies (mAbs) represent an important and rapidly growing class of biotherapeutics. Correct folding of a mAb is critical for drug efficacy, while misfolding can impact safety by eliciting unwanted immune or other off-target responses. Robust methods are therefore needed for the precise measurement of mAb structure for drug quality assessment and comparability. To date, the perception in the field has been that NMR could not be applied practically to mAbs due to the size (?150 kDa) and complexity of these molecules, as well as the insensitivity of the method. The feasibility of applying NMR methods to stable isotope-labeled, protease-cleaved, mAb domains (Fab and Fc) has been demonstrated from both E. coli and Chinese hamster ovaries (CHO) cell expression platforms; however, isotopic labeling is not typically available when analyzing drug products. Here, we address the issue of feasibility of NMR-based mapping of mAb structure by demonstrating for the first time the application of a 2D (13)C NMR methyl fingerprint method for structural mapping of an intact mAb at natural isotopic abundance. Further, we show that 2D (13)C NMR spectra of protease-cleaved Fc and Fab fragments can provide accurate reporters on the domain structures that can be mapped directly to the intact mAb. Through combined use of rapid acquisition and nonuniform sampling techniques, we show that these Fab and Fc fingerprint spectra can be rapidly acquired in as short as approximately 30 min. PMID:25728213

  4. Estimation of natural mortality coefficient from fish abundance and catch data using Virtual Population Analysis (VPA)

    NASA Astrophysics Data System (ADS)

    Wang, Yingbin; Liu, Qun; Wang, Yanjun

    2007-01-01

    Natural mortality coefficient ( M) was estimated from fish abundance ( N) and catch ( C) data using a Virtual Population Analysis (VPA) model. Monte Carlo simulations were used to evaluate the impact of different error distributions for the simulated data on the estimates of M. Among the four error structures (normal, lognormal, Poisson and gamma), simulations of normally distributed errors produced the most viable estimates for M, with the lowest relative estimation errors (REEs) and median mean absolute deviations (MADs) for the ratio of the true to the estimated Ms. In contrast, the lognormal distribution had the largest REE value. Errors with different coefficients of variation (CV) were added to N and C. In general, when CVs in the data were less than 10%, reliable estimates of M were obtained. For normal and lognormal distributions, the estimates of M were more sensitive to the CVs in N than in C; when only C had error the estimates were close to the true. For Poisson and gamma distributions, opposite results were obtained. For instance, the estimates were more sensitive to the CVs in C than in N, with the largest REE from the scenario of error only in C. Two scenarios of high and low fishing mortality coefficient ( F) were generated, and the simulation results showed that the method performed better for the scenario with low F. This method was also applied to the published data for the anchovy ( Engraulis japonicus) of the Yellow Sea. Viable estimates of M were obtained for young groups, which may be explained by the fact that the great uncertainties in N and C observed for older Yellow Sea anchovy introduced large variation in the corresponding estimates of M.

  5. 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

  6. Critical evaluation of 13C natural abundance techniques to partition soil-surface CO2 efflux

    NASA Astrophysics Data System (ADS)

    Snell, H.; Midwood, A. J.; Robinson, D.

    2013-12-01

    Soil is the largest terrestrial store of carbon and the flux of CO2 from soils to the atmosphere is estimated at around 98 Pg (98 billion tonnes) of carbon per year. The CO2 efflux from the soil surface is derived from plant root and rhizosphere respiration (autotrophically fuelled) and microbial degradation of soil organic matter (heterotrophic respiration). Heterotrophic respiration is a key determinant of an ecosystem's long-term C balance, but one that is difficult to measure in the field. One approach involves partitioning the total soil-surface CO2 efflux between heterotrophic and autotrophic components; this can be done using differences in the natural abundance stable isotope ratios (?13C) of autotrophic and heterotrophic CO2 as the end-members of a simple mixing model. In most natural, temperate ecosystems, current and historical vegetation cover (and therefore also plant-derived soil organic matter) is produced from C3 photosynthesis so the difference in ?13C between the autotrophic and heterotrophic CO2 sources is small. Successful partitioning therefore requires accurate and precise measurements of the ?13CO2 of the autotrophic and heterotrophic end-members (obtained by measuring the ?13CO2 of soil-free roots and root-free soil) and of total soil CO2 efflux. There is currently little consensus on the optimum measurement protocols. Here we systematically tested some of the most commonly used techniques to identify and minimise methodological errors. Using soil-surface chambers to sample total CO2 efflux and a cavity ring-down spectrometer to measure ?13CO2 in a partitioning study on a Scottish moorland, we found that: using soil-penetrating collars leads to a more depleted chamber measurement of total soil ?13CO2 as a result of severing roots and fungal hyphae or equilibrating with ?13CO2 at depth or both; root incubations provide an accurate estimate of in-situ root respired ?13CO2 provided they are sampled within one hour; the ?13CO2 from root-free soil changes rapidly during incubation and even CO2 sampled very soon after excavation is unlikely to give an accurate estimate of the heterotrophic isotope end-member, to solve this we applied non-linear regressions to the change in ?13CO2 with time to derive the heterotrophic end-member in undisturbed soil.

  7. Natural abundance (??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

  8. Interactions between natural-occurring landscape conditions and land use influencing the abundance of riverine smallmouth bass, micropterus dolomieu

    USGS Publications Warehouse

    Brewer, S.K.; Rabeni, C.F.

    2011-01-01

    This study examined how interactions between natural landscape features and land use influenced the abundance of smallmouth bass, Micropterus dolomieu, in Missouri, USA, streams. Stream segments were placed into one of four groups based on natural-occurring watershed characteristics (soil texture and soil permeability) predicted to relate to smallmouth bass abundance. Within each group, stream segments were assigned forest (n = 3), pasture (n = 3), or urban (n = 3) designations based on the percentages of land use within each watershed. Analyses of variance indicated smallmouth bass densities differed between land use and natural conditions. Decision tree models indicated abundance was highest in forested stream segments and lowest in urban stream segments, regardless of group designation. Land use explained the most variation in decision tree models, but in-channel features of temperature, flow, and sediment also contributed significantly. These results are unique and indicate the importance of natural-occurring watershed conditions in defining the potential of populations and how finer-scale filters interact with land use to further alter population potential. Smallmouth bass has differing vulnerabilities to land-use attributes, and the better the natural watershed conditions are for population success, the more resilient these populations will be when land conversion occurs.

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

    SciTech Connect

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

    1982-05-05

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

  10. The natural 13C abundance of plasma glucose is a useful biomarker of recent dietary caloric sweetener intake.

    PubMed

    Cook, Chad M; Alvig, Amy L; Liu, Yu Qiu David; Schoeller, Dale A

    2010-02-01

    There is a need for objective biomarkers of dietary intake, because self-reporting is often subject to bias. We tested the validity of a biomarker for the fraction of dietary carbohydrate (CHO) from cane sugar and high fructose corn syrup (C(4) sugars) using natural (13)C abundance of plasma glucose. In a randomized, single-blinded, crossover design, 5 participants consumed 3 weight-maintaining diets for 7 d, with a 2-wk washout between diet periods. Diets differed in the fraction of total CHO energy from C(4) sugars (5, 16, or 32%). During each diet period, blood samples were drawn at hours 0800 and 1600 on d 1, 3, and 5 and at 0800, 1000, 1200, 1400, and 1600 on d 7. The delta(13)C abundance of plasma glucose was analyzed via GC- isotope ratio MS. Within each diet period, delta(13)C abundance of the 0800 fasting glucose did not change from baseline with increasing time during a diet period; however, there was a strong positive correlation (R(2) = 0.89) between delta(13)C abundance of the glucose concentration at 1000 on d 7 and the percent of breakfast CHO from C(4) sugars. Also, delta(13)C abundance of the combined plasma glucose samples on d 7 demonstrated a strong positive correlation (R(2) = 0.90) with the percent of total daily CHO from C(4) sugars. The natural delta(13)C abundance of postprandial plasma glucose relative to dietary C(4) CHO content was a valid biomarker for contributions of C(4) caloric sweeteners from the previous meal. PMID:20018804

  11. 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.

  12. Is the multicolored Asian ladybeetle, Harmonia axyridis, the most abundant natural enemy to aphids in agroecosystems?

    PubMed

    Vandereycken, Axel; Durieux, Delphine; Joie, Emilie; Sloggett, John J; Haubruge, Eric; Verheggen, François J

    2013-01-01

    The multicolored Asian ladybeetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was introduced into Western Europe in the late 1990s. Since the late 2000s, this species has been commonly considered one of the most abundant aphid predators in most Western European countries. In spite of the large amount of research on H. axyridis, information concerning its relative abundance in agroecosystems is lacking. This study aims to evaluate the abundance of H. axyridis within the aphidophage community in four crops situated in southern Belgium: wheat, Triticum aestivum L. (Poales: Poaceae), corn, Zea mays, potato, Solanum tuberosum (Solanales: Solanaceae), and broad bean Vicia faba (Fabales: Fabaceae). In order to assess the species diversity, the collected data were analyzed by considering (1) the species richness and (2) the evenness according to the Shannon diversity index. Eleven aphidophages were observed in every inventoried agroecosystem, including five abundant species: three coccinellids, the seven-spotted ladybug, Coccinella septempunctata L. (Coleoptera: Coccinellidae), the 14-spotted Ladybird, Propylea quatuordecimpunctata, and H. axyridis; one hoverfly, the marmalade hoverfly, Episyrphus balteatus De Geer (Diptera: Syrphidae); and one lacewing, the common green lacewing, Chrysoperla carnea Stephens sensu lato (= s.l.) (Neuroptera: Chrysopidae). Harmonia axyridis has been observed to thrive, breed, and reproduce on the four studied crops. Harmonia axyridis is the most abundant predator of aphids in corn followed by C. septempunctata, which is the main aphid predator observed in the three other inventoried crops. In wheat and potato fields, H. axyridis occurs in low numbers compared to other aphidophage. These observations suggest that H. axyridis could be considered an invasive species of agrosystems, and that potato and wheat may intermittently act as refuges for other aphidophages vulnerable to intraguild predation by this invader. Harmonia axyridis is not the most abundant aphid predator in the main Belgian crops. PMID:24785375

  13. Is the Multicolored Asian Ladybeetle, Harmonia axyridis, the Most Abundant Natural Enemy to Aphids in Agroecosystems?

    PubMed Central

    Vandereycken, Axel; Durieux, Delphine; Joie, Emilie; Sloggett, John J.; Haubruge, Eric; Verheggen, Franois J.

    2013-01-01

    The multicolored Asian ladybeetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was introduced into Western Europe in the late 1990s. Since the late 2000s, this species has been commonly considered one of the most abundant aphid predators in most Western European countries. In spite of the large amount of research on H. axyridis, information concerning its relative abundance in agroecosystems is lacking. This study aims to evaluate the abundance of H. axyridis within the aphidophage community in four crops situated in southern Belgium: wheat, Triticum aestivum L. (Poales: Poaceae), corn, Zea mays, potato, Solanum tuberosum (Solanales: Solanaceae), and broad bean Vicia faba (Fabales: Fabaceae). In order to assess the species diversity, the collected data were analyzed by considering (1) the species richness and (2) the evenness according to the Shannon diversity index. Eleven aphidophages were observed in every inventoried agroecosystem, including five abundant species: three coccinellids, the seven-spotted ladybug, Coccinella septempunctata L. (Coleoptera: Coccinellidae), the 14-spotted Ladybird, Propylea quatuordecimpunctata, and H. axyridis; one hoverfly, the marmalade hoverfly, Episyrphus balteatus De Geer (Diptera: Syrphidae); and one lacewing, the common green lacewing, Chrysoperla carnea Stephens sensu lato (= s.l.) (Neuroptera: Chrysopidae). Harmonia axyridis has been observed to thrive, breed, and reproduce on the four studied crops. Harmonia axyridis is the most abundant predator of aphids in corn followed by C. septempunctata, which is the main aphid predator observed in the three other inventoried crops. In wheat and potato fields, H. axyridis occurs in low numbers compared to other aphidophage. These observations suggest that H. axyridis could be considered an invasive species of agrosystems, and that potato and wheat may intermittently act as refuges for other aphidophages vulnerable to intraguild predation by this invader. Harmonia axyridis is not the most abundant aphid predator in the main Belgian crops. PMID:24785375

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

    PubMed

    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

  15. 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

  16. Depth profiling of nitrogen using 429 keV and 897 keV resonances in the 15N(p, ??) 12C reaction

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjiv; Vikram Kumar, S.; Reddy, G. L. N.; Kain, Vivekanand; Ramana, J. V.; Raju, V. S.

    2005-11-01

    Resonances at 429 keV and 897 keV in the 15N(p, ??)12C reaction were investigated for depth profiling nitrogen in materials containing nitrogen isotopes in natural abundances. Both resonances exhibit identical sensitivity, however the resonance at 897 keV is prone to interferences from light elements, F and Al in particular. These resonances were employed to depth profile nitrogen in binary and ternary nitride films and in stainless steel wires that had fractured while in use in an ammonia converter vessel of a heavy water plant. The studies indicated the ingress of nitrogen into the interiors of the wires under operating conditions of the plant that lead to nitriding causing embrittlement of the components.

  17. 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.

  18. 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...

  19. 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.

  20. Flow and habitat effects on juvenile fish abundance in natural and altered flow regimes

    USGS Publications Warehouse

    Freeman, Mary C.; Bowen, Z.H.; Bovee, K.D.; Irwin, E.R.

    2001-01-01

    Conserving biological resources native to large river systems increasingly depends on how flow-regulated segments of these rivers are managed. Improving management will require a better understanding of linkages between river biota and temporal variability of flow and instream habitat. However, few studies have quantified responses of native fish populations to multiyear (>2 yr) patterns of hydrologic or habitat variability in flow-regulated systems. To provide these data, we quantified young-of-year (YOY) fish abundance during four years in relation to hydrologic and habitat variability in two segments of the Tallapoosa River in the southeastern United States. One segment had an unregulated flow regime, whereas the other was flow-regulated by a peak-load generating hydropower dam. We sampled fishes annually and explored how continuously recorded flow data and physical habitat simulation models (PHABSIM) for spring (April-June) and summer (July-August) preceding each sample explained fish abundances. Patterns of YOY abundance in relation to habitat availability (median area) and habitat persistence (longest period with habitat area continuously above the long-term median area) differed between unregulated and flow-regulated sites. At the unregulated site, YOY abundances were most frequently correlated with availability of shallow-slow habitat in summer (10 species) and persistence of shallow-slow and shallow-fast habitat in spring (nine species). Additionally, abundances were negatively correlated with 1-h maximum flow in summer (five species). At the flow-regulated site, YOY abundances were more frequently correlated with persistence of shallow-water habitats (four species in spring; six species in summer) than with habitat availability or magnitude of flow extremes. The associations of YOY with habitat persistence at the flow-regulated site corresponded to the effects of flow regulation on habitat patterns. Flow regulation reduced median flows during spring and summer, which resulted in median availability of shallow-water habitats comparable to the unregulated site. However, habitat persistence was severely reduced by flow fluctuations resulting from pulsed water releases for peak-load power generation. Habitat persistence, comparable to levels in the unregulated site, only occurred during summer when low rainfall or other factors occasionally curtailed power generation. As a consequence, summer-spawning species numerically dominated the fish assemblage at the flow-regulated site; five of six spring-spawning species occurring at both study sites were significantly less abundant at the flow-regulated site. Persistence of native fishes in flow-regulated systems depends, in part, on the seasonal occurrence of stable habitat conditions that facilitate reproduction and YOY survival.

  1. A natural abundance 33S solid-state NMR study of layered transition metal disulfides at ultrahigh magnetic field.

    PubMed

    Sutrisno, Andre; Terskikh, Victor V; Huang, Yining

    2009-01-01

    Using a series of layered transition metal disulfides we demonstrate that the wide-line natural abundance solid-state NMR spectra of 33S in a less symmetric environment can readily be obtained at ultrahigh magnetic field of 21.1 T and that surprisingly these closely related materials display a wide range of 33S quadrupole coupling constant and chemical shift anisotropy values. PMID:19099063

  2. Ureide assay for measuring nitrogen fixation by nodulated soybean calibrated by sup 15 N methods. [Glycine max

    SciTech Connect

    Herridge, D.F. ); Peoples, M.B. )

    1990-06-01

    We report experiments to quantify the relationships between the relative abundance of ureide-N in root-bleeding sap, vacuum-extracted sap, and hot water extracts of stems and petioles of nodulated soybean (Glycine max (L.) Merrill cv Bragg) and the proportion of plant N derived from nitrogen fixation. Additional experiments examined the effects of plant genotype and strain of rhizobia on these relationships. In each of the five experiments reported, plants of cv Bragg (experiment 1), cv Lincoln (experiments 3, 4, 5), or six cultivars/genotypes (experiment 2) were grown in a sand:vermiculite mixture in large pots in a naturally lit, temperature-controlled glasshouse during summer. Pots were inoculated at sowing with effective Bradyrhizobium japonicum CB 1809 (USDA 136) or with one of 21 different strains of rhizobia. The proportions of plant N derived from nitrogen fixation were determined using {sup 15}N dilution. Results show that assessment of nitrogen fixation by soybean using the ureide technique should now be possible with the standard curves presented, irrespective of genotype or strain of rhizobia occupying the nodules.

  3. Partitioning Respiration Between Plant and Microbial Sources Using Natural Abundance Stable Carbon Isotopes

    NASA Astrophysics Data System (ADS)

    Dawson, T. E.; Tu, K. P.

    2009-12-01

    Partitioning plant and microbial respiration is important for understanding the mechanistic basis of ecosystem respiration, as each can respond to changes in environmental conditions in different ways and at different timescales. In theory, natural abundance stable C isotopes can allow source partitioning when the isotopic difference between the sources can be resolved. The longstanding notion is that such differences do not exist, yet field measurements to support this conclusion are rare. The question remains as to how much isotopic difference exists between the plant and microbial respiration and whether or not this difference is sufficient for partitioning. We addressed this question by measuring the C isotope ratios (13C/12C) of plant, microbial, and whole ecosystem respiration from three contrasting ecosystems in California. We found significant variation in the 13C/12C ratios between plant and microbial sources. However, isotopic mass balance was not observed in more than half the cases. When isotopic mass balance was observed, the largest isotopic differences were always between CO2 evolved during leaf respiration and SOC decomposition, with leaf respiration more depleted by 1-8 per mil. Within plants, the leaf respiration was more depleted than rhizosphere respiration by 2-6 per mil. Among microbial sources, litter decomposition was more depleted than SOC decomposition by 1-5 per mil. The 13C/12C ratio of bulk C and respired CO2 exhibited similar trends, but bulk C values were clearly not a good surrogate for the 13C/12C ratios of respired CO2. Based on the 13C/12C ratios of respired CO2, belowground respiration accounted for 25% in the redwood forest, 37% in the grassland and 84% in the pine forest. Belowground respiration was further partitioned between rhizosphere, litter and SOC decomposition. Each contributed nearly equal amounts in the redwood forest (30/40/30) whereas litter respiration dominated in the grassland (20/70/10) and pine forest (15/65/20). Given that there were three sources and only one isotope, these estimates for belowground partitioning were only potential ranges. We also found large temporal variation in the 13C/12C ratios of plant respiration. At the pine forest, differences between night and day were as large as 4 per mil for leaf respiration and 2.5 per mil for rhizosphere respiration. Belowground respiration changed by less than 1 per mil, and this variation appeared to be driven entirely by rhizosphere respiration (r2= 94%). The fact that isotopic mass balance was not observed on many days may have been due to this temporal variability. For example, isotopic mass balance was observed in the redwood forest when all respiration samples were collected at the same time of day (pre-dawn), whereas isotopic mass balance was not observed when respiration samples were collected from different times of the day. Partitioning is therefore possible because of relatively large isotopic differences between leaf and SOC decomposition, but care must be taken to determine all source signatures at the same time due to large temporal variability.

  4. Nitrate turnover in a peat soil under drained and rewetted conditions: results from a [(15)N]nitrate-bromide double-tracer study.

    PubMed

    Russow, Rolf; Tauchnitz, Nadine; Spott, Oliver; Mothes, Sibylle; Bernsdorf, Sabine; Meissner, Ralph

    2013-01-01

    Under natural conditions, peatlands are generally nitrate-limited. However, recent concerns about an additional N input into peatlands by atmospheric N deposition have highlighted the risk of an increased denitrification activity and hence the likelihood of a rise of emissions of the greenhouse gas nitrous oxide. Therefore, the aim of the present study was to investigate the turnover of added nitrate in a drained and a rewetted peatland using a [(15)N]nitrate-bromide double-tracer method. The double-tracer method allows a separation between physical effects (dilution, dispersion and dislocation) and microbial and chemical nitrate transformation by comparing with the conservative Br(-) tracer. In the drained peat site, low NO3(-) consumption rates have been observed. In contrast, NO3(-) consumption at the rewetted peat site rises rapidly to about 100% within 4 days after tracer application. Concomitantly, the (15)N abundances of nitrite and ammonium in soil water increased and lead to the conclusion that, besides commonly known NO3(-) reduction to nitrite (i.e. denitrification), a dissimilatory nitrate reduction to ammonium has simultaneously taken place. The present study reveals that increasing NO3(-) inputs into rewetted peatlands via atmospheric deposition results in a rapid NO3(-) consumption, which could lead to an increase in N2O emissions into the atmosphere. PMID:24313368

  5. Using natural isotopic abundances to determine the source of nitrous oxide (N2O) emissions

    NASA Astrophysics Data System (ADS)

    Mothet, A.; Sebilo, M.; Laverman, A. M.; Vaury, V.; Mariotti, A.

    2012-04-01

    Numerous greenhouse gas studies have focused on carbon dioxide (CO2), whereas nitrous oxide (N2O) also plays a major role in global warming. Indeed, while nitrous oxide is 1000 times less concentrated than CO2 in the atmosphere, it is 300 times more efficient in terms of global warming potential. In addition, its atmospheric concentration increases with 0,3 % per year. According to the literature, nitrous oxide is produced, in soils and sediments, by two major processes: (1) Nitrification, mediated by autotrophic nitrifying bacteria under oxic conditions; (2) Denitrification, mediated by heterotrophic denitrifying bacteria under anoxic conditions. Denitrification induces intensive, localized and instantaneous fluxes. N2O emissions can be easily measured and modeled. In contrast, nitrification induces weak emissions, but spatially and temporally extended. Therefore, this process could represent a large potential of N2O emissions from soils and sediments. The study of isotopomer's isotopic composition of N2O, i.e. the intramolecular distribution or site preference (SP) determined by 15N measurement allows the determination of the origin of N2O emissions (nitrification vs. denitrification). Recent studies on pure cultures have showed that SP associated with nitrification is 35 ‰ while SP associated with denitrification is 0 ‰. The aim of this study was to determine SP associated with denitrification in soils and sediments, taking into account the environmental denitrifying bacterial communities, and under different environmental variables. To this end, flow-through reactors were used to determine denitrification rates at different temperatures and varying substrate (nitrate) concentrations. Site preference was measured for the different experiments. Different experiments of denitrification were realized in sediment flow through reactors under denitrifying conditions (anoxia, presence of organic matter and nitrate). We used acetylene (25°C) to block the enzyme nitrous oxide reductase, resulting in accumulation of N2O originating only from denitrification. Despite the fact that the isotopic composition of the produced N2O (15N and 18O) varies, the SP did not change significantly (SP = 6 ‰). These results compared to those of chemical denitrification show that despite very different isotopic compositions, the SP value is independent of the type of denitrification. Different nitrate concentrations (5 mM, 3 mM, 1,5 mM and 1 mM) at ambient temperature (25°C). The results of N2O production kinetics were not related to nitrate concentrations. SP of N2O are currently being analyzed. Different temperatures (35°C, 25°C and 12°C) and a nitrate concentration of 5 mM. The results of N2O production kinetics at different temperatures show an increase in N2O emissions with increasing temperature. SP of N2O are currently being analyzed. The goal for future work is to study the SP in these systems relative to salinity, pH and carbon organic concentration in denitrifying conditions but also in nitrifying conditions.

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Cobb, Alyssa K.; Pudritz, Ralph E.

    2014-03-01

    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. 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.

  9. Implications of scaled δ15N 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 (δ(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 δ(15) N (Δδ(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 Δδ(15) N scales negatively with the δ(15) N of prey. We collated existing fish community δ(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 Δδ(15) N assumptions, and to assess how the scaled Δδ(15) N assumption affects our understanding of the structure of these food webs. Adoption of the scaled Δδ(15) N approach markedly reduces the previously reported differences in TL at body mass among fish communities from different regions. With scaled Δδ(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

  10. Patterns of diversity and abundance of carrion insect assemblages in the Natural Park "Hoces del Ro Riaza" (central Spain).

    PubMed

    Baz, Arturo; Cifrin, Blanca; Martn-Vega, Daniel

    2014-01-01

    The patterns of diversity and abundance of the carrion insect species in the different habitats of the Natural Park "Hoces del Ro Riaza" (central Spain) were studied with the use of carrion-baited traps. Representativeness of the inventories was assessed with the calculation of randomized species richness curves and nonparametric estimators. Coleoptera families, Silphidae and Dermestidae, and Diptera families, Calliphoridae and Muscidae, were dominant in every sampling habitat, but differences in the patterns of diversity and abundance were found. Lusitanian oakwood and riparian forest were the most diverse habitats with high abundance of saprophagous species, whereas more open (i.e., exposed to continuous sunlight during the day) habitats showed lower diversity values and a different species composition and distribution of species abundance, favoring thermophilous species and necrophagous species with high tolerance to different environmental conditions. Differences in the bioclimatical features of the sampled habitats are suggested to explain the composition and diversity of the carrion insect assemblages in different environments. PMID:25368080

  11. Identifying diazotrophs by incorporation of nitrogen from (15)N(2) into RNA.

    PubMed

    Addison, Sarah L; McDonald, Ian R; Lloyd-Jones, Gareth

    2010-08-01

    The diversity and abundance of active diazotrophs was investigated in a New Zealand pulp and paper wastewater by enrichment with (15)N(2). Purified (15)N-RNA was analysed by reverse transcription, molecular cloning and sequence analysis of 16S rRNA to reveal a diverse community of bacteria as indicated by a Shannon Weaver Index value of > 2.8. The major class represented in the enriched culture were the gamma-Proteobacteria at 85% with a secondary group of the phylum Firmicutes present at 8.2%, the remaining sequences were affiliated with the alpha- and beta-Proteobacterial classes (1.4% and 4.3%, respectively). Three dominant genera, Aeromonas, Pseudomonas and Bacillus, were identified by comparison with published sequences and phylogenetic analysis. To confirm that representatives of the taxonomic groups identified from the active enriched nitrogen-fixing community were capable of fixing nitrogen Aeromonas and Pseudomonas species were cultivated and shown to possess nifH genes. In wastewater, fluorescence in situ hybridisation probing revealed that the dominant nitrogen-fixing population identified in this study were present in the population, but at lower levels. The population is, therefore, reliant on a small sub-population of diazotrophs to supply the community's nitrogen needs above that already present in the wastewater. PMID:20582411

  12. 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

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

    PubMed

    Shchepin, Roman V; Chekmenev, Eduard Y

    2014-08-01

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

  14. Paleoenvironmental implications of taxonomic variation among δ 15 N values of chloropigments

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    Natural variations in the ratios of nitrogen isotopes in biomass reflect variations in nutrient sources utilized for growth. In order to use δ 15N values of chloropigments of photosynthetic organisms to determine the corresponding δ 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 N 2, NO 3-, and NH 4+ as nitrogen sources, and were examined under different light regimes and growth conditions. We find surprisingly high variability in the isotopic difference (δ 15N biomass - δ 15N chloropigment) for prokaryotes, with average values for species ranging from -12.2‰ to +11.7‰. We define this difference as ɛpor, a term that encompasses diagenetic porphyrins and chlorins, as well as chlorophyll. Negative values of ɛpor reflect chloropigments that are 15N-enriched relative to biomass. Notably, this enrichment appears to occur only in cyanobacteria. The average value of ɛpor 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., ɛpor values for freshwater Chroococcales resemble those of freshwater Nostocales but differ from those of marine Chroococcales. Our measured values of ɛpor for eukaryotic algae (range = 4.7-8.7‰) are similar to previous reports for pure cultures. For all taxa studied, values of ɛpor do not depend on the type of nitrogen substrate used for growth. The observed environmental control of ɛpor suggests that values of ɛpor could be useful for determining the fractional burial of eukaryotic vs. cyanobacterial organic matter in the sedimentary record.

  15. 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

  16. 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.

  17. Identification of Biodegradation Pathways in a Multi-Process Phytoremediation System (MPPS) Using Natural Abundance 14C Analysis of PLFA

    NASA Astrophysics Data System (ADS)

    Cowie, B. R.; Greenberg, B. M.; Slater, G. F.

    2008-12-01

    Optimizing remediation of petroleum-contaminated soils requires thorough understanding of the mechanisms and pathways involved in a proposed remediation system. In many engineered and natural attenuation systems, multiple degradation pathways may contribute to observed contaminant mass losses. In this study, biodegradation in the soil microbial community was identified as a major pathway for petroleum hydrocarbon removal in a Multi-Process Phytoremediation System (MPPS) using natural abundance 14C analysis of Phospholipid Fatty Acids (PLFA). In contaminated soils, PLFA were depleted in ?14C to less than -800, directly demonstrating microbial uptake and utilization of petroleum derived carbon (?14C = -992) during bioremediation. Mass balance indicated that more than 80% of microbial carbon was derived from petroleum hydrocarbons and a maximum of 20% was produced from metabolism of modern carbon sources. In contrast, in a nearby uncontaminated control soil, the microbial community maintained a nearly modern 14C signature, suggesting preferential degradation of more labile, recent carbon. Mass balance using ?13C and ?14C of soil CO2 demonstrated that mineralization of petroleum carbon contributed 60-65% of soil CO2 at the contaminated site. The remainder was derived from atmospheric (27-30%) and decomposition of non- petroleum natural organic carbon (5-10%). The clean control exhibited substantially lower CO2 concentrations that were derived from atmospheric (55%) and natural organic carbon (45%) sources. This study highlights the value of using multiple carbon isotopes to identify degradation pathways in petroleum- contaminated soils undergoing phytoremediation and the power of natural abundance 14C to detect petroleum metabolism in natural microbial communities.

  18. Variations in the natural ?N abundance of Brassica chinensis grown in uncultivated soil affected by different nitrogen fertilizers.

    PubMed

    Yuan, Yuwei; Hu, Guixian; Zhao, Ming; Chen, Tianjin; Zhang, Yongzhi; Zhu, Jiahong; Wang, Qiang

    2014-11-26

    To further investigate the method of using ?(15)N as a marker for organic vegetable discrimination, the effects of different fertilizers on the ?(15)N in different growing stages of Brassica chinensis (B. chinensis) grown in uncultivated soil were investigated with a pot experiment. B. chinensis was planted with uncultivated soil and different fertilizer treatments and then harvested three times in three seasons consecutively. For the spring experiments in the years of 2011 and 2012, the ?(15)N value of B. chinensis, which increased due to organic manure application and decreased due to chemical fertilizer application, was significantly different (p < 0.05) with manure treatment and chemical treatment. The ?(15)N value of vegetables varied among three growing stages and ranged from +8.6 to +11.5 for the control, from +8.6 to +12.8 for the compost chicken manure treatment, from +2.8 to +7.7 for the chemical fertilizer urea treatment, and from +7.7 to +10.9 for the compost-chemical fertilizer treatment. However, the ?(15)N values observed in the autumn experiment of 2011 without any fertilizer application increased ranging from +13.4 to +15.4, + 11.2 to +17.7, +10.7 to +17.1, and +10.6 to +19.1, respectively, for the same treatments mentioned above. This result was not significantly different between manure treatment and chemical treatment. The ?(15)N values of soil obtained in the spring of 2011 during three growing stages were slightly affected by fertilizers and varied in the range of +1.6 to +2.5 for CK, +4.7 to +6.5 for compost treatment, +2.1 to +2.4 for chemical treatment, and +2.7 to +4.6 for chemical-compost treatment, respectively. High ?(15)N values of B. chinensis were observed in these experiments, which would be useful to supplement a ?(15)N database for discriminating organic vegetables. Although there was a significant difference between manure treatment and chemical treatment, it was still difficult to discriminate whether a labeled organic vegetable was really grown without chemical fertilizer just with a fixed high ?(15)N value, especially for the vegetables planted simultaneously with chemical and compost fertilizer. PMID:25369912

  19. 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 abundance15N) 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 δ15N 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, δ15N values were compared across a fixed diameter (the “fixed-diameter” method). We sampled 400 trees that differed widely in size, but measured δ15N 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 δ15N values over time with an explicit control for potential size-effects on δ15N values. We found a significant increase of tree-ring δ15N across the stem radius of large trees from Bolivia and Cameroon, but no change in tree-ring δ15N values over time was found in any of the study sites when controlling for tree size. This suggests that radial trends of δ15N 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 δ15N 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 δ15N values can be properly interpreted. PMID:25914707

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

    PubMed

    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 (15)N abundance (?(15)N) in the growth rings of some tropical trees has been hypothesized to reflect an increased leaching of (15)N-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 ?(15)N 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, ?(15)N values were compared across a fixed diameter (the "fixed-diameter" method). We sampled 400 trees that differed widely in size, but measured ?(15)N 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 ?(15)N values over time with an explicit control for potential size-effects on ?(15)N values. We found a significant increase of tree-ring ?(15)N across the stem radius of large trees from Bolivia and Cameroon, but no change in tree-ring ?(15)N values over time was found in any of the study sites when controlling for tree size. This suggests that radial trends of ?(15)N 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 ?(15)N 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 ?(15)N values can be properly interpreted. PMID:25914707

  1. 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).

  2. 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: δ18O and Δ17O); 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 δ18O-NO−3 variation, and summarize the uncertainties in using tissue NO−3 parameters to interpret plant NO−3 utilization. PMID:25101106

  3. New flaxseed orbitides: Detection, sequencing, and (15)N incorporation.

    PubMed

    Okinyo-Owiti, Denis P; Young, Lester; Burnett, Peta-Gaye G; Reaney, Martin J T

    2014-03-01

    Three new orbitides (cyclolinopeptides 17, 18, and 19) were identified in flaxseed (Linum usitatissimum L.) extracts without any form of purification. Their structures were elucidated by a combination of (15) N-labeling experiments and extensive tandem mass spectrometry (MS/MS) with electrospray ionization (ESI). Putative linear peptide sequences of the new orbitides were used as the query in the Basic Local Alignment Search Tool (BLAST) searches of flax genome database. These searches returned linear sequences for the putative precursors of cyclolinopeptides 17 and 19 among others. Cyclolinopeptide 18 contains MetO (O) and is not directly encoded, but is a product of post-translation modification of the Met present in 17. The identification of precursor proteins in flax mRNA transcripts and DNA sequences confirmed the occurrence and amino acid sequences of these orbitides as [1-9-N?C]-MLKPFFFWI, [1-9-N?C]-OLKPFFFWI, and [1-9-N?C]-GIPPFWLTL for cyclolinopeptides 17, 18, and 19, respectively. PMID:24408479

  4. 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.

  5. New Method for Estimating Bacterial Cell Abundances in Natural Samples by Use of Sublimation

    PubMed Central

    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 500C 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 ?105 to 109 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. PMID:15466534

  6. 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 radicals 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

  7. Natural abundance solid-state 67Zn NMR characterization of microporous zinc phosphites and zinc phosphates at ultrahigh magnetic field.

    PubMed

    Sutrisno, Andre; Liu, Li; Xu, Jun; Huang, Yining

    2011-10-01

    Zinc-phosphite and -phosphate based microporous materials are crystalline open framework materials with potential industrial applications. Although (31)P MAS NMR has been used for characterization of these materials, the local environments around zinc centres have never been directly probed by solid-state NMR due to the many unfavourable NMR characteristics of (67)Zn. In this work, we have characterized the local structure around the Zn centres in several representative microporous zinc phosphites and zinc phosphates by acquiring natural abundance (67)Zn solid-state NMR spectra at ultrahigh magnetic field of 21.1 T. The observed line-shapes are mainly determined by the second order quadrupolar interaction. The NMR tensor parameters were extracted from the spectra and are related to the local geometry around the Zn centre. Computational study of the electric field gradient (EFG) tensor at Zn was performed using hybrid density functional theory (DFT) calculations at B3LYP level of theory on model clusters. The calculations using Projector Augmented-Wave (PAW) method were also carried out with the CASTEP code wherever it was possible. The work has shown that it is possible to study Zn environments in porous materials which often have very low Zn concentration by natural abundance (67)Zn SSNMR at very high magnetic fields. PMID:21850324

  8. Measuring tree root respiration using (13)C natural abundance: rooting medium matters.

    PubMed

    Cheng, Weixin; Fu, Shenglei; Susfalk, Richard B; Mitchell, Robert J

    2005-07-01

    Tree root respiration utilizes a major portion of the primary production in forests and is an important process in the global carbon cycle. Because of the lack of ecologically relevant methods, tree root respiration in situ is much less studied compared with above-ground processes such as photosynthesis and leaf respiration. This study introduces a new (13)C natural tracer method for measuring tree root respiration in situ. The method partitions tree root respiration from soil respiration in buried root chambers. Rooting media substantially influenced root respiration rates. Measured in three media, the fine root respiration rates of longleaf pine were 0.78, 0.27 and 0.18 mg CO(2) carbon mg(-1) root nitrogen d(-1) at 25 degrees C in the native soil, tallgrass prairie soil, and sand-vermiculite mixture, respectively. Compared with the root excision method, the root respiration rate of longleaf pine measured by the field chamber method was 18% higher when using the native soil as rooting medium, was similar in the prairie soil, but was 42% lower if in the sand-vermiculite medium. This natural tracer method allows the use of an appropriate rooting medium and is capable of measuring root respiration nondestructively in natural forest conditions. PMID:15948851

  9. 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

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

    USGS Publications Warehouse

    Revesz, K.; Bhlke, 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.

  11. 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.

  12. 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.

  13. Compound specific amino acid δ15N 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 (δ15N) of bulk sedimentary N (δ15Nbulk) is a common tool for studying past biogeochemical cycling in the paleoceanographic record. Empirical evidence suggests that natural fluctuations in the δ15N of surface nutrient N are reflected in the δ15N of exported planktonic biomass and in sedimentary δ15Nbulk. However, δ15Nbulk 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 (δ15NAA) are novel measurements with the potential to decouple δ15N changes in nutrient N from trophic effects, two main processes that can influence δ15Nbulk records. As a proof of concept study to examine how δ15NAA can be applied in marine sedimentary systems, we compare the δ15NAA 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 δ15NAA signatures of both planktonic biomass and sinking POM are well preserved in such surface sediments. However, we also observed an unexpected inverse correlation between δ15N value of phenylalanine (δ15NPhe; 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, δ15NPhe values should in fact be directly dependent on shifts in ecosystem trophic position. While this result may appear incongruent with current applications of δ15NAA 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 δ15NAA parameters are ecosystem trophic position, which determines relative partitioning of 15N into source AA versus trophic AA pools, and the integrated δ15NAA of all common protein AA (δ15NTHAA), which serves as a proxy for the δ15N of nutrient N. Together, we suggest that these can provide a coupled picture of regime shifts in planktonic ecosystem structure, δ15N at the base of food webs, and possibly additional information about nutrient dynamics.

  14. Regional, seasonal and interspecific variation in 15N and 13C in sympatric mouse lemurs

    NASA Astrophysics Data System (ADS)

    Rakotondranary, S. Jacques; Struck, Ulrich; Knoblauch, Christian; Ganzhorn, Jörg U.

    2011-11-01

    Madagascar provides some of the rare examples where two or more primate species of the same genus and with seemingly identical niche requirements occur in sympatry. If congeneric primate species co-occur in other parts of the world, they differ in size in a way that is consistent with Hutchinson's rule for coexisting species, or they occupy different ecological niches. In some areas of Madagascar, mouse lemurs do not follow these "rules" and thus seem to violate one of the principles of community ecology. In order to understand the mechanisms that allow coexistence of sympatric congeneric species without obvious niche differentiation, we studied food composition of two identical sized omnivorous mouse lemur species, Microcebus griseorufus and M. murinus with the help of stable isotope analyses ( δ 15N and δ 13C). The two species are closely related sister species. During the rich season, when food seems abundant, the two species do not differ in their nitrogen isotope composition, indicating that the two species occupy the same trophic level. But they differ in their δ 13C values, indicating that M. griseorufus feeds more on C4 and CAM (Crassulacean-acid-metabolism) plants than M. murinus. During the lean season, M. murinus has lower δ 15N values, indicating that the two species feed at different trophic levels during times of food shortage. Hybrids between the two species showed intermediate food composition. The results reflect subtle differences in foraging or metabolic adaptations that are difficult to quantify by traditional observations but that represent possibilities to allow coexistence of species.

  15. The metabolic effect of resistant starch and yoghurt on the renal and faecal nitrogen and ammonia excretion in humans as measured by lactose-[(15)N2]ureide.

    PubMed

    Wutzke, Klaus D; Scholübbers, Debora

    2013-01-01

    Resistant starch (RS) and Lactobacillus acidophilus yoghurt (LC1) were supplemented simultaneously in healthy adults to evaluate the effect on the urinary and faecal nitrogen and ammonia excretion by means of lactose-[(15)N2]ureide ((15)N-LU) degradation. Nineteen subjects received a regular daily diet either without or with supplementation of an RS-LC1-mixture composed of fibre of potatoes (RS type 1), wrinkle pea starch (RS type 2), and LC1 over a 20-day period in randomised order. Thereafter, (15)N-LU was administered together with breakfast. Urine and faeces were collected over a period of 48 and 72 h, respectively. The (15)N abundances were measured by isotope ratio mass spectrometry. The intake of the pre- and probiotic mixture composed of RS of type 1, type 2 and of LC1 significantly lowered the colonic generation and the renal excretion of toxic (15)NH3 and functioned as an ammonia shift from urinary to faecal (15)N excretion when using (15)N-LU as a xenobiotic marker. PMID:23937067

  16. 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

  17. Estimation of Carbon and Nitrogen Allocation during Stalk Elongation by 13C and 15N Tracing in Zea mays L. 1

    PubMed Central

    Cliquet, Jean-Bernard; Delens, Eliane; Bousser, Agns; Martin, Michel; Lescure, Jean-Charles; Prioul, Jean-Louis; Mariotti, Andr; Morot-Gaudry, Jean-Franois

    1990-01-01

    Zea mays L. (cv Dea) plants grown to the stage of stalk elongation, were allowed to assimilate 13CO2 and 15N-nitrates from 45 to 53 days after sowing. Isotopic abundances in labeled nutrients were slightly enriched compared to natural abundances. The new C in plant was acropetally distributed and the new N was preferentially accumulated in the sheath and stalk in the medium region. C input was 25-fold higher than N input. The new C in total plant C was 20%, whereas it was 10% for N. The stalk acted as a major sink because it accumulated, respectively, 27.5 and 47.5% of the C and N inputs. The new C in soluble carbohydrates was 76% in growing organs (upper stalk) and only 39% in source leaves, whereas it was 43% and 13% in starch, respectively. New N in nitrates+amino-acids spanned in the range from 20% (leaf) to 50% (stalk). New C and N in soluble proteins were, respectively, 13.4 and 3.8% in leaves, 8.8 and 9.6% in stalk, and 8.7 and 14.3% in roots. In the middle stalk and leaves, the proteins and carbohydrates represent an equivalent C and N source for remobilization. Images Figure 2 Figure 3 Figure 4 PMID:16667269

  18. Natural landscape and stream segment attributes influencing the distribution and relative abundance of riverine smallmouth bass in Missouri

    USGS Publications Warehouse

    Brewer, S.K.; Rabeni, C.F.; Sowa, S.P.; Annis, G.

    2007-01-01

    Protecting and restoring fish populations on a regional basis are most effective if the multiscale factors responsible for the relative quality of a fishery are known. We spatially linked Missouri's statewide historical fish collections to environmental features in a geographic information system, which was used as a basis for modeling the importance of landscape and stream segment features in supporting a population of smallmouth bass Micropterus dolomieu. Decision tree analyses were used to develop probability-based models to predict statewide occurrence and within-range relative abundances. We were able to identify the range of smallmouth bass throughout Missouri and the probability of occurrence within that range by using a few broad landscape variables: the percentage of coarse-textured soils in the watershed, watershed relief, and the percentage of soils with low permeability in the watershed. The within-range relative abundance model included both landscape and stream segment variables. As with the statewide probability of occurrence model, soil permeability was particularly significant. The predicted relative abundance of smallmouth bass in stream segments containing low percentages of permeable soils was further influenced by channel gradient, stream size, spring-flow volume, and local slope. Assessment of model accuracy with an independent data set showed good concordance. A conceptual framework involving naturally occurring factors that affect smallmouth bass potential is presented as a comparative model for assessing transferability to other geographic areas and for studying potential land use and biotic effects. We also identify the benefits, caveats, and data requirements necessary to improve predictions and promote ecological understanding. ?? Copyright by the American Fisheries Society 2007.

  19. Using δ15N 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, δ15N 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 δ15N 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 δ15N would indicate N removal rather than possible enriched sources of N. Chironomid δ15N 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, δ15N 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 δ15N values, suggesting greater N removal. At low levels of synthetic N loading, the pattern reversed, and streams with enriched chironomid δ15N had higher N concentrations, suggesting enriched sources such as manure or sewage. Our results indicate that chironomid δ15N values can provide valuable information about watershed-level N inputs and processing for national water quality monitoring efforts.

  20. 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

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

    NASA Astrophysics Data System (ADS)

    Bocherens, Herv; Billiou, Daniel; Patou-Mathis, Marylne; Bonjean, Dominique; Otte, Marcel; Mariotti, Andr

    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.

  2. Influence of niche differentiation on the abundance of methanogenic archaea and methane production potential in natural wetland ecosystems across China

    NASA Astrophysics Data System (ADS)

    Liu, D.; Ding, W.; Jia, Z.; Cai, Z.

    2010-10-01

    Methane (CH4) emissions from natural wetland ecosystems exhibit large spatial variability. To understand the underlying factors that induce differences in CH4 emissions from natural wetlands around China, we measured the CH4 production potential and the abundance of methanogenic archaea in vertical profile soils sampled from the Poyang wetland in the subtropical zone, the Hongze wetland in the warm temperate zone, the Sanjiang marsh in the cold temperate zone, and the Ruoergai peatland in the Qinghai-Tibetan Plateau. The top soil layer had the highest population of methanogens (1.07-8.29109 cells g-1 soil) in all wetlands except the Ruoergai peatland and exhibited the maximum CH4 production potential measured at the mean in situ summer temperature. There is a significant logarithmic correlation between the abundance of methanogenic archaea and the soil organic carbon (R2=0.718, P<0.001, n=13) and between the abundance of methanogenic archaea and the total nitrogen concentrations (R2=0.758, P<0.001, n=13) in wetland soils. This indicates that the amount of soil organic carbon may affect the population of methanogens in wetland ecosystems. While the CH4 production potential is not significantly related to methanogen population (R2=0.011, P>0.05, n=13), it is related to the dissolved organic carbon concentration (R2=0.305, P=0.05, n=13). This suggests that the methanogen population is not an effective index for predicting the CH4 production in wetland ecosystems. The CH4 production rate of the top soil layer increases with increasing latitude, from 274 ?g CH4 kg-1 soil d-1 in the Poyang wetland to 665 ?g CH4 kg-1 soil d-1 in the Carex lasiocarpa marsh of the Sanjiang Plain. The CH4 production potential in the freshwater wetlands of Eastern China is affected by the supply of methanogenic substrates rather than by temperature, whereas the supply of substrates was mainly affected by the position and stability of the wetland water table. In contrast, low summer temperatures at high elevations in the Ruoergai peatland of the Qinghai-Tibetan Plateau result in the presence of dominant species of methanogens with low CH4 production potential rather than the reduction of the supply of methanogenic substrates, which in turn suppresses CH4 production.

  3. Spatio-temporal isotopic signatures (?13 C and ?15 N) reveal that two sympatric West African mullet species do not feed on the same basal production sources.

    PubMed

    Le Loc'h, F; Durand, J-D; Diop, K; Panfili, J

    2015-04-01

    Potential trophic competition between two sympatric mullet species, Mugil cephalus and Mugil curema, was explored in the hypersaline estuary of the Saloum Delta (Senegal) using ?(13) C and ?(15) N composition of muscle tissues. Between species, ?(15) N compositions were similar, suggesting a similar trophic level, while the difference in ?(13) C compositions indicated that these species did not feed from exactly the same basal production sources or at least not in the same proportions. This result provides the first evidence of isotopic niche segregation between two limno-benthophageous species belonging to the geographically widespread, and often locally abundant, Mugilidae family. PMID:25846862

  4. Nutrient regime shift in the western North Atlantic indicated by compound-specific δ15N of deep-sea gorgonian corals

    PubMed Central

    Sherwood, Owen A.; Lehmann, Moritz F.; Schubert, Carsten J.; Scott, David B.; McCarthy, Matthew D.

    2011-01-01

    Despite the importance of the nitrogen (N) cycle on marine productivity, little is known about variability in N sources and cycling in the ocean in relation to natural and anthropogenic climate change. Beyond the last few decades of scientific observation, knowledge depends largely on proxy records derived from nitrogen stable isotopes (δ15N) preserved in sediments and other bioarchives. Traditional bulk δ15N measurements, however, represent the combined influence of N source and subsequent trophic transfers, often confounding environmental interpretation. Recently, compound-specific analysis of individual amino acids (δ15N-AA) has been shown as a means to deconvolve trophic level versus N source effects on the δ15N variability of bulk organic matter. Here, we demonstrate the first use of δ15N-AA in a paleoceanographic study, through analysis of annually secreted growth rings preserved in the organic endoskeletons of deep-sea gorgonian corals. In the Northwest Atlantic off Nova Scotia, coral δ15N is correlated with increasing presence of subtropical versus subpolar slope waters over the twentieth century. By using the new δ15N-AA approach to control for variable trophic processing, we are able to interpret coral bulk δ15N values as a proxy for nitrate source and, hence, slope water source partitioning. We conclude that the persistence of the warm, nutrient-rich regime since the early 1970s is largely unique in the context of the last approximately 1,800 yr. This evidence suggests that nutrient variability in this region is coordinated with recent changes in global climate and underscores the broad potential of δ15N-AA for paleoceanographic studies of the marine N cycle. PMID:21199952

  5. Nutrient regime shift in the western North Atlantic indicated by compound-specific ?15N of deep-sea gorgonian corals.

    PubMed

    Sherwood, Owen A; Lehmann, Moritz F; Schubert, Carsten J; Scott, David B; McCarthy, Matthew D

    2011-01-18

    Despite the importance of the nitrogen (N) cycle on marine productivity, little is known about variability in N sources and cycling in the ocean in relation to natural and anthropogenic climate change. Beyond the last few decades of scientific observation, knowledge depends largely on proxy records derived from nitrogen stable isotopes (?(15)N) preserved in sediments and other bioarchives. Traditional bulk ?(15)N measurements, however, represent the combined influence of N source and subsequent trophic transfers, often confounding environmental interpretation. Recently, compound-specific analysis of individual amino acids (?(15)N-AA) has been shown as a means to deconvolve trophic level versus N source effects on the ?(15)N variability of bulk organic matter. Here, we demonstrate the first use of ?(15)N-AA in a paleoceanographic study, through analysis of annually secreted growth rings preserved in the organic endoskeletons of deep-sea gorgonian corals. In the Northwest Atlantic off Nova Scotia, coral ?(15)N is correlated with increasing presence of subtropical versus subpolar slope waters over the twentieth century. By using the new ?(15)N-AA approach to control for variable trophic processing, we are able to interpret coral bulk ?(15)N values as a proxy for nitrate source and, hence, slope water source partitioning. We conclude that the persistence of the warm, nutrient-rich regime since the early 1970s is largely unique in the context of the last approximately 1,800 yr. This evidence suggests that nutrient variability in this region is coordinated with recent changes in global climate and underscores the broad potential of ?(15)N-AA for paleoceanographic studies of the marine N cycle. PMID:21199952

  6. Stabilization dynamics of root versus needle-derived 13C and 15N during 10 years in a temperate forest soil.

    NASA Astrophysics Data System (ADS)

    Bird, J. A.; Hatton, P. J.; Castanha, C.; Torn, M. S.

    2012-12-01

    Belowground plant carbon (C) allocation as fine roots can result in greater retention of C in soils compared with aboveground litter in temperate forest ecosystems. However, much of our understanding of the fate of fine root C and nitrogen (N) in soils comes from short-term studies, often lasting only a few months to a few years. In 2011, we concluded a 10-year field study that compared the fate of dual-labeled (13C/15N) Ponderosa pine fine roots (<2 mm diameter) with needles in a temperate forest soil of the Sierra Nevada, CA, USA. The 13C- and 15N-labeled fine roots or needles were added to mesocosms at two soil depths (top of O or A horizon) to compare C and N stabilization in mineral versus organic soil horizons. We will present data on retention of litter C and N in soil after 0.5, 1.5, 5 and 10 years in situ. For soil samples recovered after 5 years, litter-derived C and N recovered in the mineral soil was partitioned into several operationally-defined physical and chemical soil organic matter (SOM) fractions, which were also characterized by natural abundance 14C. In addition, we compared two fractionation methods (i.e., with and without occluded light fraction isolation) on the partitioning of litter-derived C and N in mineral soil. After 5 years in situ the retention of fine root C in soil (59.93.8%) was significantly greater than that of added needle C (38.42.0%); however the depth of litter placement in the soil did not affect total litter C or N recovery. Our results provide a direct, decade-scale measure of stabilization of above- and belowground plant inputs to soil, including a portrait of the dominant stabilization mechanisms.

  7. 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).

  8. 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

  9. Poly-ethers from Winogradskyella poriferorum: Antifouling potential, time-course study of production and natural abundance.

    PubMed

    Dash, Swagatika; Nogata, Yasuyuki; Zhou, Xiaojian; Zhang, Yifan; Xu, Ying; Guo, Xianrong; Zhang, Xixiang; Qian, Pei-Yuan

    2011-08-01

    A sponge-associated bacterium, Winogradskyella poriferorum strain UST030701-295T was cultured up to 100l for extraction of antifouling bioactive compounds. Five poly-ethers were isolated and partially characterized based on nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS); two of them showed inhibitory effects on biofilm formation of marine bacteria and larval settlement of macro-foulers but did not produce any adverse effects on the phenotypes of zebra fish embryos at a concentration of 5?g ml(-1). The effect of culture duration on the production of the poly-ethers and the bioactivity of the relevant extracts was monitored over a period of 12 days. The total crude poly-ether production increased from day 2 to day 5 and the highest bioactivity was observed on day 3. The poly-ethers were found to be localized in the cellular fraction of the extracts, implying their natural occurrence. The potent bioactivity of these poly-ethers together with their high natural abundance in bacteria makes them promising candidates as ingredients in antifouling applications. PMID:21664125

  10. Soil organic matter stability in agricultural land: New insights using δ15N, δ13C 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 (> 63μm) 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 δ15N 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 δ15N 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 δ13C data lead to a more comprehensive understanding of the processes underlying SOM dynamics. Tillage practices increased the bulk δ13C 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 δ15N signature of the POM and mOM fraction follow the expected model pattern. The isotopic δ13C signature can further enhance the understanding of the processes driving SOM stability.

  11. 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

  12. 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, Ramn

    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.

  13. 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

  14. Screening enoxaparin tetrasaccharide SEC fractions for 3-O-sulfo-N-sulfoglucosamine residues using [(1)H,(15)N] HSQC NMR.

    PubMed

    Beecher, Consuelo N; Manighalam, Matthew S; Nwachuku, Adanma F; Larive, Cynthia K

    2016-02-01

    Heparin and heparan sulfate (HS) are important in mediating a variety of biological processes through binding to myriad different proteins. Specific structural elements along the polysaccharide chains are essential for high affinity protein binding, such as the 3-O-sulfated N-sulfoglucosamine (GlcNS3S) residue, a relatively rare modification essential for heparin's anticoagulant activity. The isolation of 3-O-sulfated oligosaccharides from complex mixtures is challenging because of their low abundance. Although methods such as affinity chromatography are useful in isolating oligosaccharides that bind specific proteins with high affinity, other important 3-O-sulfated oligosaccharides may easily be overlooked. Screening preparative-scale size-exclusion chromatography (SEC) fractions of heparin or HS digests using [(1)H,(15)N] HSQC NMR allows the identification of fractions containing 3-O-sulfated oligosaccharides through the unique (1)H and (15)N chemical shifts of the GlcNS3S residue. Those SEC fractions containing 3-O-sulfated oligosaccharides can then be isolated using strong anion-exchange (SAX)-HPLC. Compared with the results obtained by pooling the fractions comprising a given SEC peak, SAX-HPLC analysis of individual SEC fractions produces a less complicated chromatogram in which the 3-O-sulfated oligosaccharides are enriched relative to more abundant components. The utility of this approach is demonstrated for tetrasaccharide SEC fractions of the low molecular weight heparin drug enoxaparin facilitating the isolation and characterization of an unsaturated 3-O-sulfated tetrasaccharide containing a portion of the antithrombin-III binding sequence. Graphical Abstract [(1)H, (15)N] HSQC NMR spectrum of a mixture of two tetrasaccharides, one of which contains the relatively rare 3-O-sulfated N-sulfoglucosamine residue. PMID:26758598

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

    PubMed

    Vugmeyster, Liliya; Ostrovsky, Dmitry; Fu, Riqiang

    2015-10-01

    In this work, we assess the usefulness of static (15)N NMR techniques for the determination of the (15)N chemical shift anisotropy (CSA) tensor parameters and (15)N-(1)H 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 (15)N 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 (15)N backbone sites. While a simple one-dimensional line shape experiment was used for the determination of the (15)N 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 (15)N-(1)H 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. PMID:26367322

  16. 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.

  17. δ15N 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 δ15N 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 δ15N 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 δ15NO3 − 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.

  18. Resolving the bulk δ 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 δ 15N values is necessary. Determinations of δ 15N values of the individual amino acids which constitute bone collagen are necessary to unravel these relationships, since different amino acids display different δ 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 δ 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 δ 15N values reveals a 2‰ offset from bulk collagen δ 15N values which is attributable to the δ 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 δ 15N values of individual amino acids provide insights into both the contributions of various amino acids to the bulk δ 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 δ 15N values of alanine, glutamate, proline and hydroxyproline reflects the common origin of their amino groups from glutamate. The depletion in the δ 15N value of threonine with increasing trophic level indicates a fundamental difference between the biosynthetic pathway of threonine and the other amino acids. The δ 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. Δ 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 Δ 15N Glu-Phe values. Differences in nitrogen metabolism are also shown to have an influence upon individual amino acid δ 15N values with Δ 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 Δ 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.

  19. Factors Controlling the Stable Nitrogen Isotopic Composition (δ15N) of Lipids in Marine Animals

    PubMed Central

    Svensson, Elisabeth; Schouten, Stefan; Hopmans, Ellen C.; Middelburg, Jack J.; Sinninghe Damsté, Jaap S.

    2016-01-01

    Lipid extraction of biomass prior to stable isotope analysis is known to cause variable changes in the stable nitrogen isotopic composition (δ15N) of residual biomass. However, the underlying factors causing these changes are not yet clear. Here we address this issue by comparing the δ15N of bulk and residual biomass of several marine animal tissues (fish, crab, cockle, oyster, and polychaete), as well as the δ15N of the extracted lipids. As observed previously, lipid extraction led to a variable offset in δ15N of biomass (differences ranging from -2.3 to +1.8 ‰). Importantly, the total lipid extract (TLE) was highly depleted in 15N compared to bulk biomass, and also highly variable (differences ranging from -14 to +0.7 ‰). The TLE consisted mainly of phosphatidylcholines, a group of lipids with one nitrogen atom in the headgroup. To elucidate the cause for the 15N-depletion in the TLE, the δ15N of amino acids was determined, including serine because it is one of the main sources of nitrogen to N-containing lipids. Serine δ15N values differed by -7 to +2 ‰ from bulk biomass δ15N, and correlated well with the 15N depletion in TLEs. On average, serine was less depleted (-3‰) than the TLE (-7 ‰), possibly due to fractionation during biosynthesis of N-containing headgroups, or that other nitrogen-containing compounds, such as urea and choline, or recycled nitrogen contribute to the nitrogen isotopic composition of the TLE. The depletion in 15N of the TLE relative to biomass increased with the trophic level of the organisms. PMID:26731720

  20. Factors Controlling the Stable Nitrogen Isotopic Composition (?15N) of Lipids in Marine Animals.

    PubMed

    Svensson, Elisabeth; Schouten, Stefan; Hopmans, Ellen C; Middelburg, Jack J; Sinninghe Damst, Jaap S

    2016-01-01

    Lipid extraction of biomass prior to stable isotope analysis is known to cause variable changes in the stable nitrogen isotopic composition (?15N) of residual biomass. However, the underlying factors causing these changes are not yet clear. Here we address this issue by comparing the ?15N of bulk and residual biomass of several marine animal tissues (fish, crab, cockle, oyster, and polychaete), as well as the ?15N of the extracted lipids. As observed previously, lipid extraction led to a variable offset in ?15N of biomass (differences ranging from -2.3 to +1.8 ). Importantly, the total lipid extract (TLE) was highly depleted in 15N compared to bulk biomass, and also highly variable (differences ranging from -14 to +0.7 ). The TLE consisted mainly of phosphatidylcholines, a group of lipids with one nitrogen atom in the headgroup. To elucidate the cause for the 15N-depletion in the TLE, the ?15N of amino acids was determined, including serine because it is one of the main sources of nitrogen to N-containing lipids. Serine ?15N values differed by -7 to +2 from bulk biomass ?15N, and correlated well with the 15N depletion in TLEs. On average, serine was less depleted (-3) than the TLE (-7 ), possibly due to fractionation during biosynthesis of N-containing headgroups, or that other nitrogen-containing compounds, such as urea and choline, or recycled nitrogen contribute to the nitrogen isotopic composition of the TLE. The depletion in 15N of the TLE relative to biomass increased with the trophic level of the organisms. PMID:26731720

  1. 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, nne

    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

  2. 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

  3. 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

  4. 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 4.66.0 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 3.04.9%. 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 431% 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

  5. 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.

  6. Molecular characterization of dissolved organic matter in glacial ice: coupling natural abundance 1H NMR and fluorescence spectroscopy.

    PubMed

    Pautler, Brent G; Woods, Gwen C; Dubnick, Ashley; Simpson, Andr J; Sharp, Martin J; Fitzsimons, Sean J; Simpson, Myrna J

    2012-04-01

    Glaciers and ice sheets are the second largest freshwater reservoir in the global hydrologic cycle, and the onset of global climate warming has necessitated an assessment of their contributions to sea-level rise and the potential release of nutrients to nearby aquatic environments. In particular, the release of dissolved organic matter (DOM) from glacier melt could stimulate microbial activity in both glacial ecosystems and adjacent watersheds, but this would largely depend on the composition of the material released. Using fluorescence and (1)H NMR spectroscopy, we characterize DOM at its natural abundance in unaltered samples from a number of glaciers that differ in geographic location, thermal regime, and sample depth. Parallel factor analysis (PARAFAC) modeling of DOM fluorophores identifies components in the ice that are predominantly proteinaceous in character, while (1)H NMR spectroscopy reveals a mixture of small molecules that likely originate from native microbes. Spectrofluorescence also reveals a terrestrial contribution that was below the detection limits of NMR; however, (1)H nuclei from levoglucosan was identified in Arctic glacier ice samples. This study suggests that the bulk of the DOM from these glaciers is a mixture of biologically labile molecules derived from microbes. PMID:22385100

  7. In vivo quantitation of cerebral metabolite concentrations using natural abundance 13C MRS at 1.5 T.

    PubMed

    Blüml, S

    1999-02-01

    A method for the quantitation of cerebral metabolites on a clinical MR scanner by natural abundance 13C MRS in vivo is 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 in 13C 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 in 13C MRS, consistent with the 41% increase to 12.3 +/- 1.1 from control 8.7 +/- 1.1 mmol/kg assayed by 1H 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. PMID:9986765

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

    NASA Astrophysics Data System (ADS)

    Blml, 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.

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

    PubMed

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

    2015-01-01

    Two-dimensional (1)H{(13)C} 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 (1)H dimension without resorting to (1)H-(1)H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. 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. PMID:25773137

  10. 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

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

    SciTech Connect

    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 without 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.

  12. 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...

  13. 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

  14. 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…

  15. 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…

  16. 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.

  17. 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 ...

  18. 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

  19. Disturbance and topography shape nitrogen availability and δ15N 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 δ15N values. We examined soil and foliar patterns in N and δ15N, and soil N mineralization, across a topographically complex montane forest landscape influenced by human logging ...

  20. An optimized method for (15)N R(1) relaxation rate measurements in non-deuterated proteins.

    PubMed

    Gair, Margarida; Dyachenko, Andrey; Gonzlez, M Teresa; Feliz, Miguel; Pons, Miquel; Giralt, Ernest

    2015-06-01

    (15)N longitudinal relaxation rates are extensively used for the characterization of protein dynamics; however, their accurate measurement is hindered by systematic errors. (15)N CSA/(1)H-(15)N dipolar cross-correlated relaxation (CC) and amide proton exchange saturation transfer from water protons are the two main sources of systematic errors in the determination of (15)N R1 rates through (1)H-(15)N HSQC-based experiments. CC is usually suppressed through a train of 180 proton pulses applied during the variable (15)N relaxation period (T), which can perturb water magnetization. Thus CC cancellation is required in such a way as to minimize water saturation effects. Here we examined the level of water saturation during the T period caused by various types of inversion proton pulses to suppress CC: (I) amide-selective IBURP-2; (II) cosine-modulated IBURP-2; (III) Watergate-like blocks; and (IV) non-selective hard. We additionally demonstrate the effect of uncontrolled saturation of aliphatic protons on (15)N R1 rates. In this paper we present an optimized pulse sequence that takes into account the crucial effect of controlling also the saturation of the aliphatic protons during (15)N R1 measurements in non-deuterated proteins. We show that using cosine-modulated IBURP-2 pulses spaced 40ms to cancel CC in this optimized pulse program is the method of choice to minimize systematic errors coming from water and aliphatic protons saturation effects. PMID:25947359

  1. Spectroscopic factors for low-lying N16 levels and the astrophysical N15(n ,?)N16 reaction rate

    NASA Astrophysics Data System (ADS)

    Guo, B.; Li, Z. H.; Li, Y. J.; Su, J.; Pang, D. Y.; Yan, S. Q.; Wu, Z. D.; Li, E. T.; Bai, X. X.; Du, X. C.; Fan, Q. W.; Gan, L.; He, J. J.; Jin, S. J.; Jing, L.; Li, L.; Li, Z. C.; Lian, G.; Liu, J. C.; Shen, Y. P.; Wang, Y. B.; Yu, X. Q.; Zeng, S.; Zhang, L. Y.; Zhang, W. J.; Liu, W. P.

    2014-01-01

    Background: Fluorine is a key element for nucleosynthetic studies since it is extremely sensitive to the physical conditions within stars. The astrophysical site to produce fluorine is suggested to be asymptotic giant branch stars. In these stars the N15(n,?)N16 reaction could affect the abundance of fluorine by competing with N15(? ,?)F19. Purpose: The N15(n ,?)N16 reaction rate depends directly on the neutron spectroscopic factors of the low-lying states in N16. Shell model calculations and two previous measurements of the (d ,p) reaction yielded the spectroscopic factors with a discrepancy by a factor of 2. The present work aims to explore these neutron spectroscopic factors through an independent transfer reaction and to determine the stellar rate of the N15(n,?)N16 reaction. Methods: The angular distributions of the N15(Li7,Li6)N16 reaction populating the ground state and the first three excited states in N16 are measured using a Q3D magnetic spectrograph and are used to derive the spectroscopic factors of these states based on distorted wave Born approximation analysis. Results: The spectroscopic factors of these four states are extracted to be 0.96 0.09, 0.69 0.09, 0.84 0.08, and 0.65 0.08, respectively. Based on the new spectroscopic factors we derive the N15(n ,?)N16 reaction rate. Conclusions: The accuracy and precision of the spectroscopic factors are enhanced due to the first application of high-precision magnetic spectrograph for resolving the closely spaced N16 levels which cannot be achieved in most recent measurements. The present result demonstrates that two levels corresponding to neutron transfers to the 2s1/2 orbit in N16 are not good single-particle levels although N15 is a closed neutron-shell nucleus. This finding is contrary to the shell model expectation. The present work also provides an independent examination to shed some light on the existing discrepancies in the spectroscopic factors and the N15(n ,?)N16 rate.

  2. Using a macroalgal ?15N bioassay to detect cruise ship waste water effluent inputs.

    PubMed

    Kaldy, James

    2011-08-01

    Green macroalgae bioassays were used to determine if the ?15N signature of cruise ship waste water effluent (CSWWE) could be detected in a small harbor. Opportunistic green macroalgae (Ulva spp.) were collected, cultured under nutrient depleted conditions and characterized with regard to N content and ?15N. Samples of algae were used in controlled incubations to evaluate the direction of isotope shift from exposure to CSWWE. Algae samples exposed to CSWWE exhibited an increase of 1-2.5 in ?15N values indicating that the CSWWE had an enriched isotope signature. In contrast, algae samples exposed to field conditions exhibited a significant decrease in the observed ?15N indicating that a light N source was used. Isotopically light, riverine nitrogen derived from N2-fixing trees in the watershed may be a N source utilized by algae. These experiments indicate that the ?15N CSWWE signature was not detectable under the CSWWE loading conditions of this experiment. PMID:21683418

  3. 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.

  4. 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.

  5. The effect of manuring on cereal and pulse amino acid ?(15)N values.

    PubMed

    Styring, Amy K; Fraser, Rebecca A; Bogaard, Amy; Evershed, Richard P

    2014-06-01

    Amino acid ?(15)N values of barley (Hordeum vulgare) and bread wheat (Triticum aestivum) grains and rachis and broad bean (Vicia faba) and pea (Pisum sativum) seeds, grown in manured and unmanured soil at the experimental farm stations of Rothamsted, UK and Bad Lauchstdt, Germany, were determined by GC-C-IRMS. Manuring was found to result in a consistent (15)N-enrichment of cereal grain amino acid ?(15)N values, indicating that manuring did not affect the metabolic routing of nitrogen (N) into cereal grain amino acids. The increase in cereal grain ?(15)N values with manuring is therefore due to a (15)N-enrichment in the ?(15)N value of assimilated inorganic-N. Greater variation was observed in the (15)N-enrichment of rachis amino acids with manuring, possibly due to enhanced sensitivity to changes in growing conditions and higher turnover of N in rachis cells compared to cereal grains. Total amino acid ?(15)N values of manured and unmanured broad beans and peas were very similar, indicating that the legumes assimilated N2 from the atmosphere rather than N from the soil, since there was no evidence for routing of (15)N-enriched manure N into any of the pulse amino acids. Crop amino acid ?(15)N values thus provide insights into the sources of N assimilated by non N2-fixing and N2-fixing crops grown on manured and unmanured soils, and reveal an effect of manure on N metabolism in different crop species and plant parts. PMID:24631496

  6. Disturbance and topography shape nitrogen availability and δ15 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 δ15N values. We examined soil and foliar patterns in N and δ15N, 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 δ15N 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 δ15N values after disturbance. A more important role for symbiotic N fixation is suggested by lower soil δ15N values in slow-successional sites with slow canopy closure, which favors early-successional N fixers. Soil δ15N 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 δ15N values, steady-state mass balance calculations suggest that wildfire combustion of vegetation and detritus can dominate long-term N loss and increase whole-ecosystem δ15N. On steeper topography, declining soil δ15N values highlight erosion and accelerated soil turnover as an additional abiotic control on N balances. We conclude for N-limited montane forests that soil δ15N and N availability are less influenced by nitrate leaching and denitrification loss than by interactions between disturbance, N fixation, and erosion.

  7. 15N Content Reflects Development of Mycorrhizae and Nitrogen Dynamics During Primary Succession

    NASA Astrophysics Data System (ADS)

    Hobbie, E. A.; Jumpponen, A.

    2004-05-01

    Mycorrhizal fungi are ubiquitous symbionts on terrestrial plants that are particularly important for plant nitrogen nutrition. 15N content appears to be a useful marker of the mycorrhizal role in plant nitrogen supply because of an apparent fractionation against 15N during transfer of nitrogen from mycorrhizal fungi to host plants. Because plants developing during primary succession are gradually colonized by mycorrhizal fungi, such situations provide good opportunities to study interactions between mycorrhizal colonization and plant 15N content. Here, we present results of a study of nitrogen isotope patterns in ecosystem components during the first 100 years of ecosystem development after glacial retreat, and compare those patterns with those on adjacent mature terrain. Soils in primary succession were depleted in 15N relative to nitrogen-fixing plants. Nonmycorrhizal plants and plants generally colonized by ectomycorrhizal, ericoid, or arbuscular fungi showed similar 15N content very early in succession (-4 to -6 ), corresponding to low colonization levels of all plant species. Subsequent colonization of evergreen plants by ectomycorrhizal and ericoid fungi led to a 5-6 decline in 15N content, indicating transfer of 15N-depleted N from fungi to plants. The values recorded (-10 to -14 ) are among the lowest yet observed in vascular plants. Nonmycorrhizal plants and plants colonized by arbuscular mycorrhizal fungi did not decline in 15N content. Most ectomycorrhizal and saprotrophic fungi were similar in 15N content in early succession (-1 to -3 ), with the notable exception of ectomycorrhizal fungi suspected of proteolytic capabilities, which were 15N enriched relative to all other fungi. 15N contents in both plants and soil from the mature site were 5 greater than in recently exposed sites. We conclude that 1) the primary nitrogen source to this ecosystem must be atmospheric deposition, 2) low plant 15N content generally corresponds with greater influence of mycorrhizal fungi on plant N supply, and 3) 15N content of mycorrhizal fungi may be a marker of proteolytic capabilities, and may therefore indicate the importance of organic nitrogen cycling to plant nitrogen supply.

  8. Natural-abundance stable carbon isotopes of small-subunit ribosomal RNA (SSU rRNA) from Guaymas Basin (Mexico)

    NASA Astrophysics Data System (ADS)

    MacGregor, B. J.; Mendlovitz, H.; Albert, D.; Teske, A. P.

    2012-12-01

    Small-subunit ribosomal RNA (SSU rRNA) is a phylogenetically informative molecule found in all species. Because it is poorly preserved in most environments, it is a useful marker for active microbial populations. We are using the natural-abundance stable carbon isotopic composition of specific microbial groups to help identify the carbon substrates contributing to microbial biomass in a variety of marine environments. At Guaymas Basin, hydrothermal fluids interact with abundant sedimentary organic carbon to produce natural gas and petroleum. Where this reaches the sediment surface, it can support dense patches of seafloor life, including Beggiatoa mats. We report here on the stable carbon isotopic composition of SSU rRNA from a Beggiatoa mat transect, a cold background site, a warm site with high oil concentration, and a second Beggiatoa mat. The central part of the transect mat overlay the steepest temperature gradient, and was visually dominated by orange Beggiatoa. This was fringed by white Beggiatoa mat and bare, but still warm, sediment. Methane concentrations were saturating beneath the orange and white mats and at the oily site, lower beneath bare sediment, and below detection at the background site. Our initial hypotheses were that rRNA isotopic composition would be strongly influenced by methane supply, and that archaeal rRNA might be lighter than bacterial due to contributions from methanogens and anaerobic methane oxidizers. We used biotin-labeled oligonucleotides to capture Bacterial and Archaeal SSU rRNA for isotopic determination. Background-site rRNA was isotopically heaviest, and bacterial RNA from below 2 cm at the oily site was lightest, consistent with control by methane. Within the transect mat, however, the pattern was more complicated; at some sediment depths, rRNA from the mat periphery was isotopically lightest. Part of this may be due to the spatially and temporally variable paths followed by hydrothermal fluid, which can include horizontal flow. There was no consistent isotopic difference between rRNAs captured by the two probes, although RNA recoveries were too low for isotopic determinations at depths where methanogens and methane oxidizers are expected. Our prediction that rRNA stable carbon isotopic composition would correlate with methane supply was borne out by the comparison between background and mat sediments, but may be an oversimplification for sites within hydrothermal features. Future work will include the isotopic characterization of other potential carbon substrates, such as acetate. We are also investigating cold-seep sediments and brine pools in the Gulf of Mexico, where methane is significantly more 13C-depleted than at Guaymas Basin and may therefore leave a stronger imprint on microbial biomass.table carbon isotopes of rRNA captured with Bacterial and Archaeal probes at mat transect and background sites.

  9. 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.

  10. Production of 15N-depleted biomass during cyanobacterial N2-fixation at high Fe concentrations

    NASA Astrophysics Data System (ADS)

    Zerkle, Aubrey L.; Junium, Christopher K.; Canfield, Donald E.; House, Christopher H.

    2008-09-01

    In this study we examine the effects of varying Fe, Mo, and P concentrations on ?15N fractionation during N2 fixation in the cyanobacterium Anabaena variabilis. We show that when grown in Fe-enriched media ([Fe] ? 50 nM), this organism produces biomass up to 3 lower in ?15N than when grown in Fe-limited media ([Fe] < 50 nM). A compilation of our data with previous measurements of ?15N in N2-fixing cyanobacteria reveals a general trend toward the production of more 15N-depleted biomass at higher Fe concentrations. We discuss our results in the context of negative ?15N values preserved in Archean and some Phanerozoic sediments, generally attributed to the production of marine organic matter with low ?15N by N2 fixation (and potentially NH4+ regeneration) during periods of fluctuating nutrient dynamics. We suggest that enhanced Fe availability during periods of widespread ocean anoxia can further stimulate the production of 15N-depleted biomass by N2-fixing organisms, contributing to the isotopic record.

  11. Nitrogen stable isotope composition (δ15N) of vehicle-emitted NOx.

    PubMed

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

    2015-02-17

    The nitrogen stable isotope ratio of NOx (δ(15)N-NOx) has been proposed as a regional indicator for NOx source partitioning; however, knowledge of δ(15)N values from various NOx emission sources is limited. This study presents a detailed analysis of δ(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 δ(15)N-NOx was analyzed. The vehicles sampled in this study emitted δ(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 δ(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 δ(15)N-NOx values emitted from vehicles. PMID:25621737

  12. 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.

  13. sup 14,15 N, sup 13 C, sup 57 Fe, and sup 1,2 H Q-band ENDOR study of Fe-S proteins with clusters that have endogenous sulfur ligands

    SciTech Connect

    Houseman, A.L.P.; Chaoliang Fan; Werst, M.M.; Hoffman, B.M. ); Byungha Oh; Markley, J.L. ); Kennedy, M.C.; Beinert, H. )

    1992-02-25

    The benefits of performing ENDOR experiments at higher microwave frequency are demonstrated in a Q-band (35 GHz) ENDOR investigation of a number of proteins with (nFe-mS) clusters, n = 2,3,4. Each protein displays several resonances in the frequency range of 0-20 MHz. In all instances, features are seen near {nu} {approx} 13 and 8 MHz that can be assigned, respectively, to distant ENDOR from {sup 13}C in natural-abundance (1.1%) and from {sup 14}N. In addition, a number of proteins show local {sup 13}C ENDOR signals with resolved hyperfine interactions; these are assigned to the {beta} carbons of cysteines bound to the cluster. Quadrupole coupling constants are derived for both local and distant {sup 14}N signals. The interpretation of the data is supported by studies on {sup 15}N- and {sup 13}C-enriched ferredoxin (Fd) from Anabaena 7120, where the {sup 15}N signals can be clearly correlated with the corresponding {sup 14}N signals and where the {sup 13}C signals are strongly enhanced. Thus, the observation of {sup 14}N {Delta}m{sub I} = {plus minus} 2 signals at Q-band provides a new technique for examining weak interactions with a cluster. Six proteins show an additional pattern near {nu} {approx} 18 MHz that arises from {sup 57}Fe in natural abundance (2.2%) with A({sup 57}Fe) {approx} 36 MHz, which opens the possibility of studying proteins for which enrichment is impractical. Q-band ENDOR studies also have been carried out on four {sup 2}H-exchanged Fe-S proteins, and ENDOR detects exchangeable protons in each. The importance of these findings for the interpretation of X- and Q-band ENDOR at low radiofrequencies is discussed.

  14. Evaluating microbial carbon sources in Athabasca oil sands tailings ponds using natural abundance stable and radiocarbon isotopes

    NASA Astrophysics Data System (ADS)

    Ahad, J. M.; Pakdel, H.

    2013-12-01

    Natural abundance stable (?13C) and radiocarbon (?14C) isotopes of phospholipid fatty acids (PLFAs) were used to evaluate the carbon sources utilized by the active microbial populations in surface sediments from Athabasca oil sands tailings ponds. The absence of algal-specific PLFAs at three of the four sites investigated, in conjunction with ?13C signatures for PLFAs that were generally within ~3 of that reported for oil sands bitumen (~ -30), indicated that the microbial communities growing on petroleum constituents were dominated by aerobic heterotrophs. The ?14C values of PLFAs ranged from -906 to -586 and pointed to a significant uptake of fossil carbon (up to ~90% of microbial carbon derived from petroleum), particularly in PLFAs (e.g., cy17:0 and cy19:0) often associated with petroleum hydrocarbon degrading bacteria. The comparatively higher levels of 14C in other, less specific PLFAs (e.g., 16:0) indicated the preferential uptake of younger organic matter by the general microbial population (~50-80% of microbial carbon derived from petroleum). Since the main carbon pools in tailings sediment were essentially 'radiocarbon dead' (i.e., no detectable 14C), the principal source for this modern carbon is considered to be the Athabasca River, which provides the bulk of the water used in the bitumen extraction process. The preferential uptake of the minor amount of young and presumably more biodegradable material present in systems otherwise dominated by recalcitrant petroleum constituents has important implications for remediation strategies. On the one hand, it implies that mining-related organic contaminants could persist in the environment long after tailings pond reclamation has begun. Alternatively, it may be that the young, labile organic matter provided by the Athabasca River plays an important role in stimulating or supporting the microbial utilization of petroleum carbon in oil sands tailings ponds via co-metabolism or priming processes. Further research needs to examine the role which priming processes play in controlling the fate of organic contaminants in Athabasca oil sands tailings ponds, such as understanding to what extent the addition of labile material may hinder or enhance microbial uptake of fossil carbon. This knowledge can be subsequently used to optimize conditions which favour natural attenuation processes in reclamation sites following mine closure.

  15. Coronal Abundances

    NASA Astrophysics Data System (ADS)

    Fludra, A.; Saba, J. L. R.; Henoux, J.-C.; Murphy, R. J.; Reames, D. V.; Lemen, J. R.; Strong, K. T.; Sylwester, J.; Widing, K. G.

    Flare X-Ray Measurements from BCS Calcium Abundance Fe/H and Fe/Ca Abundance Relative Abundances of Ar. Ca. and Fe in Flares Factors Affecting Abundance Determinations from X-Ray Spectra FCS Abundances FCS Active-Region Abundances Abundance Variability in Active Regions Impact of Resonance Scattering Assessment of FCS Active-Region Abundance Results FCS Flare Abundance Studies Coronal CI/S and Ar/S Measurements Dem Studies of Flare Abuncances Determination of Solar Abundances by Solar Flare γ-Ray Spectrometry γ-Ray Spectral Analysis γ-Ray Results Solar Energetic Particles Major Proton Events CIR Events from Coronal Holes Impulsive Flare Events Theory of Abundance Fractionation Gravitational Settling Pressure Gradient and Stationary Diffusion Ion-Neutral Separation Due to Currents Ion-Neutral Separation Due to Electromagnetic Forces Discussion Summary

  16. Nitrogen dynamics in a Western Boundary Upwelling System (Cabo Frio, Brazil) based on ?15N-nitrate and ?15N of sinking particle signals

    NASA Astrophysics Data System (ADS)

    Fontana, L.; Belem, A. L.; Venancio, I.; Duarte, C.; Chiara, S. D.; Albuquerque, A. L.

    2014-12-01

    To improve the efficiency of upwelling to control nitrogen dynamic in the ocean, better understanding of the occurring processes is necessary. This research explores ?15N of nitrate and sinking particles on a western boundary upwelling System (Cabo Frio, Brazil). The Continental Shelf of southeastern Brazil is dominated by the oligotrophic Brazil Current, whose instabilities promote the coastal upwelling of South Atlantic Central Water (SACW), and consequently increases of primary productivity. The coastal upwelling system plays an important role in the nitrogen dynamics on the Cabo Frio Upwelling System (CFUS). However, the interactions between biological induced processes, including biological N-fixation and nitrate inputs from upwelled waters in CFUS still have not been well explored. Then, this study aims clarify N-dynamics on CFUS based on a cross-shelf approach. ?15N-nitrate was characterized for each water masses present on the shelf (South Atlantic Central Water, Tropical Water and Coastal Water) and associated with physicochemical parameters (T/S, nutrients), as well as the ?15N of sinking particles at different depths (from surface to the bottom water). Samples were collected in a time interval of 1 month during ~4 years (2011 to 2014). Cross-shelf gradients of nitrogen species concentration (ammonium + nitrite + nitrate) and stable isotopes were observed. The ?15N of nitrate and sinking particles were interpreted according to the prevailing processes of the N-transformations. Considering the region as N-limited (N:P < 16), processes as biological N-fixation seems to be dominant on oligotrophic Tropical Waters. Coastal upwelled SACW showed ?15N-nitrate signature within the global average of deep ocean (5-6) characterizing the inner and mid-shelf conditions, where the input of new nitrate from upwelling is rapidly used by organisms in the euphotic zone without any fractionation. On the other hands, the dominance of N-limited Tropical Waters on the outer shelf provide a ?15N-nitrate and ?15N-sinking particles signals (-2.0 to 3.0) lower than the global average of deep ocean range indicating the importance of N-biological fixation as a dominant source of nitrogen.

  17. 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.

  18. EFFECT OF HIGH-ENERGY RESONANCES ON THE {sup 18}O(p, {alpha}){sup 15}N REACTION RATE AT AGB AND POST-AGB RELEVANT TEMPERATURES

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Mukhamedzhanov, A. M.

    2010-11-10

    The {sup 18}O(p, {alpha}){sup 15}N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as {sup 19}F, {sup 18}O, and {sup 15}N. Fluorine is synthesized in the intershell region of asymptotic giant branch (AGB) stars, together with s-elements, by {alpha} radiative capture on {sup 15}N, which in turn is produced in the {sup 18}O proton-induced destruction. Peculiar {sup 18}O abundances are observed in R-Coronae Borealis stars, having {sup 16}O/{sup 18}O {approx}< 1, hundreds of times smaller than the galactic value. Finally, there is no definite explanation of the {sup 14}N/{sup 15}N ratio in pre-solar grains formed in the outer layers of AGB stars. Again, such an isotopic ratio is influenced by the {sup 18}O(p, {alpha}){sup 15}N reaction. In this work, a high accuracy {sup 18}O(p, {alpha}){sup 15}N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. Indeed, current determinations are uncertain because of the poor knowledge of the resonance parameters of key levels of {sup 19}F. In particular, we have focused on the study of the broad 660 keV 1/2{sup +} resonance corresponding to the 8.65 MeV level of {sup 19}F. Since {Gamma} {approx} 100-300 keV, it determines the low-energy tail of the resonant contribution to the cross section and dominates the cross section at higher energies. Here, we provide a reaction rate that is a factor of two larger above T {approx} 0.5 10{sup 9} K based on our new improved determination of its resonance parameters, which could strongly influence present-day astrophysical model predictions.

  19. 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.

  20. 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.

  1. δ13C and δ15N values in scales of Micropterus salmoides largemouth bass as a freshwater environmental indicator.

    PubMed

    Inamura, O; Zhang, J; Minagawa, M

    2012-01-15

    We have investigated the effectiveness of using the Micropterus salmoides largemouth bass, which is a top predator found throughout the world, as the index of a hydrosphere environment and its food chain. To this end, we used stable carbon and nitrogen isotope analysis (SIA). Largemouth bass were collected from eight dam reservoirs and two ponds in Toyama Prefecture, Japan. Toyama is located in central Japan and features a variety of distinct geographical environments, a result of the 3000-m elevation that changes over short distances, and abundant water systems. The mean δ(13)C and δ(15)N values for the lipid-extracted muscle of largemouth bass from all sampling locations showed large variability, but there were only small standard deviations at each sampling location. The isotope ratios for largemouth bass express the characteristics of each investigated hydrosphere environment and food chain. A very high correlation (δ(13)C: Y(scale) = 0.96 X(muscle) + 1.58, R(2) = 0.98, δ(15)N: Y(scale) = 0.92 X(muscle) - 1.15, R(2) = 0.95) of SIA values was found between largemouth bass scales and lipid-extracted muscles, which suggests that the more easily analyzed scales are useful as SIA samples for the monitoring and comparison of hydrosphere environments throughout the world. PMID:22215573

  2. On the measurement of 15N-{1H} nuclear Overhauser effects.

    PubMed

    Ferrage, Fabien; Piserchio, Andrea; Cowburn, David; Ghose, Ranajeet

    2008-06-01

    Accurate quantification of the 15N-{1H} steady-state NOE is central to current methods for the elucidation of protein backbone dynamics on the fast, sub-nanosecond time scale. This experiment is highly susceptible to systematic errors arising from multiple sources. The nature of these errors and their effects on the determined NOE ratio is evaluated by a detailed analysis of the spin dynamics during the pair of experiments used to measure this ratio and possible improvements suggested. The experiment that includes 1H irradiation, is analyzed in the framework of Average Liouvillian Theory and a modified saturation scheme that generates a stable steady-state and eliminates the need to completely saturate 1H nuclei is presented. The largest source of error, however, in 1H-dilute systems at ultra-high fields is found to be an overestimation of the steady-state NOE value as a consequence of the incomplete equilibration of the magnetization in the so-called "reference experiment". The use of very long relaxation delays is usually an effective, but time consuming, solution. Here, we introduce an alternative reference experiment, designed for larger, deuterated systems, that uses the fastest relaxing component of the longitudinal magnetization as a closer approximation to the equilibrium state for shorter relaxation delays. The utility of the modified approach is illustrated through simulations on realistic spin systems over a wide range of time scales and experimentally verified using a perdeuterated sample of human ubiquitin. PMID:18417394

  3. 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.

  4. Eastern oyster (Crassostrea virginica) δ15N 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 (δ15N) 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 δ15N, 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 δ15N 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 δ15N 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

  5. Secondary sup 15 N isotope effects on the reactions catalyzed by alcohol and formate dehydrogenases

    SciTech Connect

    Rotberg, N.S.; Cleland, W.W. )

    1991-04-23

    Secondary {sup 15}N isotope effects at the N-1 position of 3-acetylpyridine adenine dinucleotide have been determined, by using the internal competition technique, for horse liver alcohol dehydrogenase (LADH) with cyclohexanol as a substrate and yeast formate dehydrogenase (FDH) with formate as a substrate. On the basis of less precise previous measurements of these {sup 15}N isotope effects, the nicotinamide ring of NAD has been suggested to adopt a boat conformation with carbonium ion character at C-4 during hydride transfer. If this mechanism were valid, as N-1 becomes pyramidal an {sup 15}N isotope effect for the reaction catalyzed by LADH was measured. These values suggest that a significant {sup 15}N kinetic isotope effect is not associated with hydride transfer for LADH and FDH. Thus, in contrast with the deformation mechanism previously postulated, the pyridine ring of the nucleotide apparently remains planar during these dehydrogenase reactions.

  6. 15N fractionation in star-forming regions and Solar System objects

    NASA Astrophysics Data System (ADS)

    Wirström, Eva; Milam, Stefanie; Adande, Gilles; Charnley, Steven B.; Cordiner, Martin A.

    2015-08-01

    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 pristine molecular content of comets, interplanetary dust particles and carbonaceous chondrites show significant bulk nitrogen isotopic fractionation relative to the solar value, 14N/15N ~ 440. In addition, high spatial resolution measurements in primitive materials locally show even more extreme enhancements of 14N/15N < 100.The coherent 15N enrichment in comets from different formation zones suggests that these isotopic enhancements are remnants of the interstellar chemistry in the natal molecular cloud core and the outer protosolar nebula. Indeed, early chemical models of gas-phase ion-molecule nitrogen fractionation showed that HCN and HNC (nitriles) can hold significant 15N enrichments in cold dark clouds where CO is depleted onto dust grains. In addition, 15N fractionation in nitriles and amines (NH2, NH3) follow different chemical pathways. More recently we have shown that once the spin-state dependence in rates of reactions with H2 is included in the models, amines can either be enhanced or depleted in 15N, depending on the core’s evolutionary stage. Observed 15N fractionation in amines and nitriles therefore cannot be expected to be the same, instead their ratio is a potential chemical clock.Observations of molecular isotope ratios in dark cores are challenging. Limited published results in general show higher 15N/14N ratios in HCN and HNC than ammonia, but more measurements are necessary to confirm these trends. We will present recent results from our ongoing observing campaign of 14N/15N isotopic ratios in HCN, HNC and NH3 in dense cores and protostars which seem consistent with significant fractionation in nitriles as compared to other molecules in each object. The few 14N/15N ratios observed in N2H+ are similar to those in NH3, contrary to our model results which predict a significant 15N enhancement in N2 and N2H+. Model upgrades which may address this discrepancy will be presented and discussed.

  7. The First in Vivo Observation of 13C- 15N Coupling in Mammalian Brain

    NASA Astrophysics Data System (ADS)

    Kanamori, Keiko; Ross, Brian D.

    2001-12-01

    [5-13C,15N]Glutamine, with 1J(13C-15N) of 16 Hz, was observed in vivo in the brain of spontaneously breathing rats by 13C MRS at 4.7 T. The brain [5-13C]glutamine peak consisted of the doublet from [5-13C,15N]glutamine and the center [5-13C,14N]glutamine peak, resulting in an apparent triplet with a separation of 8 Hz. The time course of formation of brain [5-13C,15N]glutamine was monitored in vivo with a time resolution of 20-35 min. This [5-13C,15N]glutamine was formed by glial uptake of released neurotransmitter [5-13C]glutamate and its reaction with 15NH3 catalyzed by the glia-specific glutamine synthetase. The neurotransmitter glutamate C5 was selectively13C-enriched by intravenous [2,5-13C]glucose infusion to 13C-label whole-brain glutamate C5, followed by [12C]glucose infusion to chase 13C from the small and rapidly turning-over glial glutamate pool, leaving 13C mainly in the neurotransmitter [5-13C]glutamate pool, which is sequestered in vesicles until release. Hence, the observed [5-13C,15N]glutamine arises from a coupling between 13C of neuronal origin and 15N of glial origin. Measurement of the rate of brain [5-13C,15N]glutamine formation provides a novel noninvasive method of studying the kinetics of neurotransmitter uptake into glia in vivo, a process that is crucial for protecting the brain from glutamate excitotoxicity.

  8. 15N techniques and analytical procedures. Indo/U. S. science and technology initiative. Research report

    SciTech Connect

    Porter, L.K.; Mosier, A.R.

    1992-05-01

    (15)N technology is used to explore many agricultural research topics, including the movement of nitrates to groundwater, use of fertilizer nitrogen by plants, ways to increase nitrogen fixation, and effects of management practices on denitrification. The publication reviews (15)N procedures and methods for handling and collecting samples, introducing isotopes into plants and soils, and for performing Kjeldahl analyses, isotope dilutions, Rittenberg oxidation conversions for isotope-ration analyses, and automated Dumas isotope-ratio analyses.

  9. 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.

  10. Modeling the flow of 15N after a 15N pulse to study long-term N dynamics in a semiarid grassland.

    PubMed

    Dijkstra, Feike A

    2009-08-01

    Many aspects of nitrogen (N) cycling in terrestrial ecosystems remain poorly understood. Progress in studying N cycling has been hindered by a lack of effective measurements that integrate processes such as denitrification, competition for N between plants and microbes, and soil organic matter (SOM) decomposition over large time scales (years rather than hours or days). Here I show how long-term measurements of 15N in plants, microbes, and soil after a one-time addition of 15N ("labeled" N) can provide powerful information about long-term N dynamics in a semiarid grassland. I develop a simple dynamic model and show that labeled-N fractions in plant and microbial-N pools (expressed as a fraction of total N in each pool) can change long after 15N application (> or = 5 years). These 15N dynamics are closely tied to the turnover times of the different N pools. The model accurately simulated the labeled-N fractions in aboveground biomass measured annually during five years after addition of 15N to a semiarid grassland. I also tested the sensitivity of five different processes on labeled-N fractions in aboveground plant biomass. Changing plant/microbial competition for N had very little effect on the labeled-N fraction in aboveground biomass in the short and long-term. Changing microbial activity (N mineralization and immobilization), N loss, or N resorption/re-translocation by plants affected the labeled-N fraction in the short-term, but not in the long-term. Large long-term effects on the labeled-N fraction in aboveground biomass could only be established by changing the size of the active soil-N pool. Therefore, the significantly greater long-term decline in the labeled-N fraction in aboveground biomass observed under elevated CO2 in this grassland system could have resulted from an increased active soil-N pool under elevated CO2 (i.e., destabilization of soil organic matter that was relatively recalcitrant under ambient CO2 conditions). I conclude that short- and long-term labeled-N fractions in plant biomass after a 15N pulse are sensitive to processes such as N mineralization and immobilization, N loss, and soil organic matter (de-)stabilization. Modeling these fractions provides a useful tool to better understand N cycling in terrestrial ecosystems. PMID:19739379

  11. Elastic and inelastic scattering of 15N ions by 9Be at 84 MeV

    NASA Astrophysics Data System (ADS)

    Rudchik, A. T.; Chercas, K. A.; Kemper, K. W.; Rusek, K.; Rudchik, A. A.; Herashchenko, O. V.; Koshchy, E. I.; Pirnak, Val. M.; Piasecki, E.; Trzcińska, A.; Sakuta, S. B.; Siudak, R.; Strojek, I.; Stolarz, A.; Ilyin, A. P.; Ponkratenko, O. A.; Stepanenko, Yu. M.; Shyrma, Yu. O.; Szczurek, A.; Uleshchenko, V. V.

    2016-03-01

    Angular distributions of the 9Be + 15N elastic and inelastic scattering were measured at Elab(15N) = 84 MeV (Ec.m. = 31.5 MeV) for the 0-6.76 MeV states of 9Be and 0-6.32 MeV states of 15N. The data were analyzed within the optical model and coupled-reaction-channels method. The elastic and inelastic scattering, spin reorientations of 9Be in ground and excited states and 15N in excited states as well as the most important one- and two-step transfer reactions were included in the channels-coupling scheme. The parameters of the 9Be + 15N optical potential of Woods-Saxon form as well as deformation parameters of these nuclei were deduced. The analysis showed that the 9Be + 15N pure potential elastic scattering dominates at the forward angles whereas the ground state spin reorientation of 9Be gives a major contribution to the elastic scattering cross sections at the large angles. Contributions from particle transfers are found to be negligible for the present scattering system.

  12. Use of /sup 15/N to measure nitrogen uptake in eutrophic oceans; experimental considerations

    SciTech Connect

    Not Available

    1986-07-01

    The use of /sup 15/N to measure the flux of nitrogen compounds has become increasingly popular as the techniques and instrumentation for stable isotope analysis have become more widely available. Questions concerning equations for calculating uptake, effect of isotope dilution (in the case of ammonium), duration of incubation, and relationship between disappearance of a nitrogen compound and the /sup 15/N uptake measurement have arisen, especially for the research conducted in oligotrophic regions. Fewer problems seem to have occurred ineutrophic areas. However, sufficient literature now exists to allow some generally accepted experimental procedures for /sup 15/N studies in eutrophic regions to be laid down. Incubation periods of 2-6 h appear to avoid problems related to isotope dilution and to overcome the bias introduced in some cases by initial high rate or surge uptake. During such incubation periods, assimilation is measured rather than uptake or transport into the cell. Incorporation of /sup 15/N into the particulate fraction is usually linear with time over the periods currently used. The /sup 15/N method provides a better estimate of incorporation into phytoplankton than /sup 14/N disappearance, but a small fraction appears to be lost. Although most workers suggest the loss to be a result of dissolved organic nitrogen production, direct evidence is lacking. If the considerations discussed here are applied with the /sup 15/N techniques currently available, reliable estimates of phytoplankton nitrogen flux in eutrophic areas can be obtained.

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

    NASA Astrophysics Data System (ADS)

    Szcs, T.; Bemmerer, D.; Caciolli, A.; Flp, Zs.; Massarczyk, R.; Michelagnoli, C.; Reinhardt, T. P.; Schwengner, R.; Takcs, 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.

  14. 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

  15. 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 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.

  16. 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, Frdrique; Leroux, Cdric; 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Sunshine, J. M.; Pieters, C. M.

    1993-05-01

    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. Acetylene inhibition of N2O reduction in laboratory soil and groundwater denitrification assays: evaluation by 15N tracer and 15N site preference of N2O

    NASA Astrophysics Data System (ADS)

    Weymann, Daniel; Well, Reinhard; Lewicka-Szczebak, Dominika; Lena, Rohe

    2013-04-01

    The measurement of denitrification in soils and aquifers is still challenging and often enough associated with considerable experimental effort and high costs. Against this background, the acetylene inhibition technique (AIT) applied in laboratory soil and groundwater denitrification assays is by far the most effective approach. However, this method has been largely criticized, as it is susceptible to underestimate denitrification rates and adds an additional carbon source to the substrates to be investigated. Here we provide evidence that the AIT is not necessarily an inappropriate approach to measure denitrification, that its reliability depends on the drivers governing the process, and that the 15N site preference of N2O (SP) may serve as a tool to assess this reliability. Two laboratory batch experiments were conducted, where sandy aquifer material and a peat soil were incubated as slurries. We established (i) a standard anaerobic treatment by adding KNO3 (10 mg N L-1), (ii) an oxygen treatment by adding KNO3 and O2 (5 mg L-1), and (iii) a glucose treatment by adding KNO3 supplemented with glucose (200 mg C L-1). Both experiments were run under 10 % (v/v) acetylene atmosphere and as 15N tracer treatments using labeled K15NO3 (60 atom % 15N). In the case of the standard anaerobic treatments, we found a very good agreement of denitrification potential obtained by the AIT and 15N tracer methods. SP of N2O of the AIT samples from this treatment ranged between -4.8 and 2.6 which is indicative for N2O production during bacterial denitrification but not for N2O reduction to N2. In contrast, we observed substantial underestimation of denitrification by AIT for the glucose treatments compared to the 15N method, i.e. denitrification was underestimated by 36 % (sandy aquifer material) and 47 % (peat soil). SP of N2O of the AIT samples from this treatment ranged between 4.5 and 9.6 , which suggests occurrence of bacterial N2O reduction. In the case of the oxygen treatments, we observed a very good agreement of denitrification potential obtained by the AIT and 15N tracer methods for the aquifer material, but a significant underestimation of 20 % in the AIT samples of the peat soil. The 15N site preference of N2O again mirrored this and ranged between -1.2 and -3.5 (aquifer material) and 5.5 and 11.0 (peat soil), respectively. We conclude that the AIT can act as a reliable method in laboratory soil and groundwater bacterial denitrification assays, but our results suggest that this relies on substrate types and incubation conditions. Additional measurements of SP have potential to assess AIT efficacy and can help to reduce parallel time-consuming and expensive 15N tracer experiments.

  20. HN-NCA heteronuclear TOCSY-NH experiment for (1)H(N) and (15)N sequential correlations in ((13)C, (15)N) labelled intrinsically disordered proteins.

    PubMed

    Wiedemann, Christoph; Goradia, Nishit; Hfner, Sabine; Herbst, Christian; Grlach, Matthias; Ohlenschlger, Oliver; Ramachandran, Ramadurai

    2015-10-01

    A simple triple resonance NMR experiment that leads to the correlation of the backbone amide resonances of each amino acid residue 'i' with that of residues 'i-1' and 'i+1' in ((13)C, (15)N) labelled intrinsically disordered proteins (IDPs) is presented. The experimental scheme, {HN-NCA heteronuclear TOCSY-NH}, exploits the favourable relaxation properties of IDPs and the presence of (1) J C?N and (2) J C?N couplings to transfer the (15)N x magnetisation from amino acid residue 'i' to adjacent residues via the application of a band-selective (15)N-(13)C(?) heteronuclear cross-polarisation sequence of ~100ms duration. Employing non-uniform sampling in the indirect dimensions, the efficacy of the approach has been demonstrated by the acquisition of 3D HNN chemical shift correlation spectra of ?-synuclein. The experimental performance of the RF pulse sequence has been compared with that of the conventional INEPT-based HN(CA)NH pulse scheme. As the availability of data from both the HCCNH and HNN experiments will make it possible to use the information extracted from one experiment to simplify the analysis of the data of the other and lead to a robust approach for unambiguous backbone and side-chain resonance assignments, a time-saving strategy for the simultaneous collection of HCCNH and HNN data is also described. PMID:26282620

  1. Separation of Anisotropy and Exchange Broadening Using 15N CSA- 15N- 1H Dipole-Dipole Relaxation Cross-Correlation Experiments

    NASA Astrophysics Data System (ADS)

    Renner, Christian; Holak, Tad A.

    2000-08-01

    Based on the measurement of cross-correlation rates between 15N CSA and 15N-1H dipole-dipole relaxation we propose a procedure for separating exchange contributions to transverse relaxation rates (R2 = 1/T2) from effects caused by anisotropic rotational diffusion of the protein molecule. This approach determines the influence of anisotropy and chemical exchange processes independently and therefore circumvents difficulties associated with the currently standard use of T1/T2 ratios to determine the rotational diffusion tensor. We find from computer simulations that, in the presence of even small amounts of internal flexibility, fitting T1/T2 ratios tends to underestimate the anisotropy of overall tumbling. An additional problem exists when the N-H bond vector directions are not distributed homogeneously over the surface of a unit sphere, such as in helix bundles or ?-sheets. Such a case was found in segment 4 of the gelation factor (ABP 120), an F-actin cross-linking protein, in which the diffusion tensor cannot be calculated from T1/T2 ratios. The 15N CSA tensor of the residues for this ?-sheet protein was found to vary even within secondary structure elements. The use of a common value for the whole protein molecule therefore might be an oversimplification. Using our approach it is immediately apparent that no exchange broadening exists for segment 4 although strongly reduced T2 relaxation times for several residues could be mistaken as indications for exchange processes.

  2. Estimate of production of gaseous nitrogen in the human body based on (15)N analysis of breath N2 after administration of [(15)N2]urea.

    PubMed

    Junghans, Peter

    2013-01-01

    After oral administration of [(15)N2]urea (1.5 mmol, 95 atom% (15)N), we found that breath N2 was significantly (15)N-labelled. The result suggests that molecular nitrogen in breath must be partly produced endogenously. Based on a metabolic model, the endogenous N2 production was estimated to be 0.400.25 mmol kg(-1) d(-1) or 2.91.8 % of the total (urinary and faecal) N excretion in fasted healthy subjects (n=4). In patients infected with Helicobacter pylori (n=5), the endogenous N2 production was increased to 1.240.59 mmol kg(-1) d(-1) or 9.04.3 % of the total N excretion compared to the healthy controls (p<0.05). We conclude that N balance and gas exchange measurements may be affected by endogenously produced nitrogen, especially in metabolic situations with elevated nitrosation, for instance in oxidative and nitrosative stress-related diseases such as H. pylori infections. PMID:24219365

  3. Application of capillary gas chromatography-reaction interface/mass spectrometry to the selective detection of sup 13 C-, sup 15 N-, sup 2 H-, and sup 14 C-labeled drugs and their metabolites

    SciTech Connect

    Chace, D.H.

    1989-01-01

    A novel reaction interface/mass spectrometer (RIMS) technique has been applied to the selective detection of {sup 13}C-, {sup 15}N-, {sup 2}H-, and {sup 14}C-labeled phenytoin and its metabolites in urine following separation by capillary gas chromatography. The microwave-powered reaction interface converts materials from their original forms into small molecules whose mass spectra serve to identify and quantify the nuclides. The presence of each element is followed by monitoring the isotopic variants of CO{sub 2}, NO, H{sub 2}, or CH{sub 4} that are produced by the reaction interface. Chromatograms showing only enriched {sup 13}C and {sup 15}N were produced using the net {sup 13}CO{sub 2} or {sup 15}NO signal derived by subtracting the abundance of naturally occurring isotopes from the observed M + 1 signal. When hydrogen was used as a reactant gas, a selective chromatogram of {sup 2}H (D) was obtained by measuring HD at m/Z 3.0219, and a chromatogram showing {sup 14}C was obtained by measuring {sup 14}CH{sub 4} at m/Z 18.034 with a high resolution. For a stable isotope detection, metabolites representing less than 1.5% of the total labeled compounds could be detected in the chromatogram. Detection limits of 170 pCi/mL (34 pCi on column that is equivalent to 187 pg) of a {sup 14}C- labeled metabolite was detected. To identify many of these labeled peaks (metabolites), the chromatographic analysis was repeated with the reaction interface turned off and mass spectra obtained at the retention times found in the RIMS experiment. In addition to the ability of GC-RIMS to detect the presence of {sup 13}C-, {sup 15}N-, and {sup 2}H- (D), it can also quantify the level of enrichment. Enrichment of {sup 13}C and {sup 15}N is quantified by measuring the ratio of excess {sup 13}CO{sub 2} to total {sup 12}CO{sub 2} or excess {sup 15}NO to total {sup 14}NO.

  4. 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...

  5. 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.

  6. 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.

  7. Advancements in natural abundance solid-state 33S MAS NMR: characterization of transition-metal M=S bonds in ammonium tetrathiometallates.

    PubMed

    Jakobsen, Hans J; Hove, Anders R; Bildsøe, Henrik; Skibsted, Jørgen; Brorson, Michael

    2007-04-28

    We report the first (33)S chemical shift anisotropy (CSA) data as obtained from a combined determination of (33)S CSA and quadrupole coupling parameters utilizing the observation of both the (33)S (I = 3/2) central and satellite transitions in a natural abundance (33)S MAS NMR study aimed at characterizing the two important tetrathiometallates (NH4)(2)MoS(4) and (NH4)(2)WS(4). PMID:17530082

  8. 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).

  9. Natural Carbon Isotope Abundance of Plasma Metabolites and Liver Tissue Differs between Diabetic and Non-Diabetic Zucker Diabetic Fatty Rats

    PubMed Central

    Godin, Jean-Philippe; Ross, Alastair B.; Cléroux, Marilyn; Pouteau, Etienne; Montoliu, Ivan; Moser, Mireille; Kochhar, Sunil

    2013-01-01

    Background ‘You are what you eat’ is an accurate summary for humans and animals when it comes to carbon isotope abundance. In biological material, natural13C/12C ratio is subject to minute variations due to diet composition (mainly from ingestion of C3 and C4 metabolism plants) and to the discrimination between ‘light’ and ‘heavy’ isotopes during biochemical reactions (isotope effects and isotopic fractionation). Methodology/Principal Findings Carbon isotopic abundance was measured in ZDF (fa/+) and ZDF (fa/fa), (lean and obese-diabetic rats respectively) fed the same diet. By analysing plasma metabolites (glucose and non-esterified fatty acids), breath and liver tissue by high-precision isotope ratio mass spectrometry, we demonstrate for the first time statistically distinguishable metabolic carbon isotope abundance between ZDF (fa/+) and ZDF (fa/fa) rats based on plasma glucose, palmitic, oleic, linoleic, arachidonic acids and bulk analysis of liver tissue (P<0.005) resulting into clear isotopic fingerprints using principal component analysis. We studied the variation of isotopic abundance between both groups for each metabolite and through the metabolic pathways using the precursor/product approach. We confirmed that lipids were depleted in 13C compared to glucose in both genotypes. We found that isotopic abundance of linoleic acid (C18: 2n-6), even though both groups had the same feed, differed significantly between both groups. The likely reason for these changes between ZDF (fa/+) and ZDF (fa/fa) are metabolic dysregulation associated with various routing and fluxes of metabolites. Conclusion/Significance This work provides evidence that measurement of natural abundance isotope ratio of both bulk tissue and individual metabolites can provide meaningful information about metabolic changes either associated to phenotype or to genetic effects; irrespective of concentration. In the future measuring the natural abundance δ13C of key metabolites could be used as endpoints for studying in vivo metabolism, especially with regards to metabolic dysregulation, and development and progression of metabolic diseases. PMID:24086387

  10. Rivermouth Alteration of Agricultural Impacts on Consumer Tissue δ15N

    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 δ15N of riverine consumer tissues. However, processes within aquatic ecosystems also influence consumer tissue δ15N. As aquatic processes become more important terrestrial inputs may become a weaker predictor of consumer tissue δ15N. In a previous study, this terrestrial-consumer tissue δ15N 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 δ15N 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

  11. Rivermouth alteration of agricultural impacts on consumer tissue δ15N

    USGS Publications Warehouse

    Larson, James H.; Richardson, William B.; Vallazza, Jonathan M.; Nelson, J. C.

    2013-01-01

    Terrestrial agricultural activities strongly influence riverine nitrogen (N) dynamics, which is reflected in the δ15N of riverine consumer tissues. However, processes within aquatic ecosystems also influence consumer tissue δ15N. As aquatic processes become more important terrestrial inputs may become a weaker predictor of consumer tissue δ15N. In a previous study, this terrestrial-consumer tissue δ15N 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 δ15N 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.

  12. Determination of organic milk authenticity using carbon and nitrogen natural isotopes.

    PubMed

    Chung, Ill-Min; Park, Inmyoung; Yoon, Jae-Yeon; Yang, Ye-Seul; Kim, Seung-Hyun

    2014-10-01

    Natural stable isotopes of carbon and nitrogen ((12)C, (13)C, (14)N, (15)N) have abundances unique to each living creature. Therefore, measurement of the stable isotope ratio of carbon and nitrogen (δ(13)C=(13)C/(12)C, δ(15)N=(15)N/(14)N) in milk provides a reliable method to determine organic milk (OM) authenticity. In the present study, the mean δ(13)C value of OM was higher than that of conventional milk (CM), whereas the mean δ(15)N value of OM was lower than that of CM; nonetheless both δ(13)C and δ(15)N values were statistically different for the OM and CM (P<0.05). Furthermore, the values of δ(13)C and δ(15)N were found to differ statistically with the collection date and the milk brand (P<0.05). The combination of δ(13)C and δ(15)N values was more effective than either value alone in distinguishing between OM and CM. The results of the present study, which is based on preliminary data from a limited sample size and sampling period, could be highly valuable and helpful for consumers, the food industry, and/or government regulatory agencies as it can prevent fraudulent labelling of organic food. Further studies include additional analyses of other milk brands and analyses over longer time periods in order to accurately determine OM authenticity using stable isotopes of carbon and nitrogen. PMID:24799230

  13. 3D 15N/15N/1H chemical shift correlation experiment utilizing an RFDR-based 1H/1H mixing period at 100 kHz MAS

    NASA Astrophysics Data System (ADS)

    Nishiyama, Yusuke; Malon, Michal; Ishii, Yuji; Ramamoorthy, Ayyalusamy

    2014-07-01

    Homonuclear correlation NMR experiments are commonly used in the high-resolution structural studies of proteins. While 13C/13C chemical shift correlation experiments utilizing dipolar recoupling techniques are fully utilized under MAS, correlation of the chemical shifts of 15N nuclei in proteins has been a challenge. Previous studies have shown that the negligible 15N-15N dipolar coupling in peptides or proteins necessitates the use of a very long mixing time (typically several seconds) for effective spin diffusion to occur and considerably slows down a 15N/15N correlation experiment. In this study, we show that the use of mixing proton magnetization, instead of 15N, via the recoupled 1H-1H dipolar couplings enable faster 15N/15N correlation. In addition, the use of proton-detection under ultrafast MAS overcomes the sensitivity loss due to multiple magnetization transfer (between 1H and 15N nuclei) steps. In fact, less than 300 nL (?1.1 micromole quantity) sample is sufficient to acquire the 3D spectrum within 5 h. Our results also demonstrate that a 3D 15N/15N/1H experiment can render higher resolution spectra that will be useful in the structural studies of proteins at ultrafast MAS frequencies. 3D 15N/15N/1H and 2D radio frequency-driven dipolar recoupling (RFDR)-based 1H/1H experimental results obtained from a powder sample of N-acetyla-L-15N-valyl-L-15N-leucine at 70 and 100 kHz MAS frequencies are presented.

  14. 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.

  15. 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

  16. Neutron capture cross section of {sup 15}N at stellar energies

    SciTech Connect

    Meissner, J.; Schatz, H.; Herndl, H.; Wiescher, M.; Beer, H.; Kaeppeler, F.

    1996-02-01

    The neutron capture rate on {sup 15}N may be of considerable importance for {ital s}-process nucleosynthesis in red giants as well as for the nucleosynthesis in inhomogeneous big bang scenarios. We measured the reaction cross section of {sup 15}N({ital n},{gamma}){sup 16}N at the Forschungszentrum Karlsruhe with a fast cyclic neutron activation technique at laboratory neutron energies of 25, 152, and 370 keV. Direct capture and shell model calculations were performed to interpret the results. The presented reaction rate is 30{endash}50{percent} smaller than the previously used theoretical rates. {copyright} {ital 1996 The American Physical Society.}

  17. 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.

  18. Nitrogen Retention in Three Streams in the Piedmont Region of North Carolina Using a 15N Tracer Addition

    NASA Astrophysics Data System (ADS)

    Rushforth, H. M.; Hershey, A. E.

    2005-05-01

    Stream restoration is often done as a compensatory mitigation project, but it is unresolved as to what extent restoration helps restore natural nutrient cycling within streams. During the summer of 2004 we ran a stable isotope drip of 15 NH 4Cl for 4 weeks in a forested pristine stream, an unrestored urban stream (but with a restored riparian zone), and a restored urban stream (restored channel and riparian zone). All three streams were located in the piedmont region of North Carolina. By collecting and analyzing samples along a 500m reach in each stream we were able to trace 15N uptake into the food web components. Preliminary results indicate that the restored stream was less retentive of 15N in periphyton and other food web components than the unrestored stream. Differences between these two urban streams likely reflect continued nitrogen loading rather than the instream conditions. The unrestored urban stream had consistently higher mean algal biomass than the other two streams. Grazers were consistently more enriched than periphyton in all streams. Hydropsychid caddisflies were isotopically similar to grazers in the forested and unrestored stream, but tracked seston in the restored stream indicating considerable variability in their trophic status.

  19. 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 releaseleakage 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.

  20. Multiple regression models of δ13C and δ15N 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 δ13C and δ15N 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 (δ13Cvar and δ15Nvar) 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 δ13Cvar and δ15Nvar 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 δ15Nvar 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 δ13Cvar model had a lower predictive capability and mean absolute errors ranged from 0.42 to 0.48‰. δ15N trends are likely linked to gradients in nitrogen fixation and Mississippi River influence on the West Florida Shelf, while δ13C 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.

  1. Abundance and seasonal activity of questing Ixodes ricinus ticks in their natural habitats in southern Germany in 2011.

    PubMed

    Schulz, Michaela; Mahling, Monia; Pfister, Kurt

    2014-06-01

    Questing ticks were sampled monthly over a period of 11 months from February, 2011 to December, 2011 at 13 sites in southern Germany using the flagging method. The ticks were identified to species, gender, and stadium. Although both I. ricinus and D. reticulatus were sampled, this study concentrated on I. ricinus, since it was the most abundant tick to be found. Additional weather data (air and soil temperature, relative air humidity, precipitation, sunshine duration) were recorded on each sampling site and the local vegetation described. A total of 14, 394 ticks was collected (7,862 larvae, 5,568 nymphs, 964 adults) and their activity was recorded in order to determine the seasonal activity pattern over different periods of the year. In contrast to the widely accepted pattern of a bimodal seasonal activity in moderate areas with a dominant peak in spring and a minor peak in autumn, a unimodal activity pattern was found for all development stages on six of the 12 sampling sites. Tick abundance was compared to weather variables. Tick host-seeking activity was found to be significantly dependent on the temperature at ground level, precipitation, and sunshine duration as well as relative air humidity. Adult ticks showed a positive correlation with the duration of sunshine, whereas nymphs were mostly unaffected by this phenomenon. PMID:24820556

  2. 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

  3. The degree of urbanization across the globe is not reflected in the ?(15)N of seagrass leaves.

    PubMed

    Christiaen, Bart; Bernard, Rebecca J; Mortazavi, Behzad; Cebrian, Just; Ortmann, Alice C

    2014-06-30

    Many studies show that seagrass ?(15)N ratios increase with the amount of urbanization in coastal watersheds. However, there is little information on the relationship between urbanization and seagrass ?(15)N ratios on a global scale. We performed a meta-analysis on seagrass samples from 79 independent locations to test if seagrass ?(15)N ratios correlate with patterns of population density and fertilizer use within a radius of 10-200 km around the sample locations. Our results show that seagrass ?(15)N ratios are more influenced by intergeneric and latitudinal differences than the degree of urbanization or the amount of fertilizer used in nearby watersheds. The positive correlation between seagrass ?(15)N ratios and latitude hints at an underlying pattern in discrimination or a latitudinal gradient in the (15)N isotopic signature of nitrogen assimilated by the plants. The actual mechanisms responsible for the correlation between ?(15)N and latitude remain unknown. PMID:23866922

  4. Transfer of (15)N from oral lactose-ureide to lysine in normal adults.

    PubMed

    Jackson, Alan A; Gibson, Neil R; Bundy, Rafe; Hounslow, Angela; Millward, D Joe; Wootton, Stephen A

    2004-09-01

    The metabolic fate of salvaged urea-nitrogen was explored in normal adults who had consumed a diet that provided 36 g protein/day for 7 days. We hypothesised that the colonic microflora utilise nitrogen derived from urea salvage to synthesise lysine in functionally significant amounts for the host. Oral lactose-[(15)N(15)N]ureide is resistant to digestion but is fermented by the colonic microflora to release (15)NH3, which can be used for amino acid synthesis. Prime and intermittent oral doses of lactose-[(15)N(15)N]ureide were ingested for 18 h, urine was collected every 3 h and stools were collected for a further 2 days. Amino acids were isolated from urine and from faecal bacterial protein and the enrichment measured. Compared with baseline values, there was significant enrichment (atoms per cent excess) in faecal bacterial glycine (0.0526), alanine (0.117), lysine (0.0875) and histidine (0.0487), and in urinary glycine (0.016), alanine (0.0144) and lysine (0.0098), but not hisitidine. These data show that the gastrointestinal bacteria can utilise urea-nitrogen in the formation of essential and non-essential amino acids that are available to the host. We estimate that on this low protein diet the amount of lysine from bacterial synthesis and available to the host may be 30 mg/kg/day. These data have important implications for our current perceptions for the dietary requirements for essential amino acids. PMID:15762310

  5. 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...

  6. 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...

  7. Using a Macroalgal δ15N 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 δ15N signature of cruise ship waste water effluent (CSWWE) could be detected in Skagway Harbor, AK. Opportunistic green...

  8. [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

  9. Modelling postsilking nitrogen fluxes in maize (Zea mays) using 15N-labelling field experiments.

    PubMed

    Gallais, André; Coque, Marie; Quilléré, Isabelle; Prioul, Jean-Louis; Hirel, Bertrand

    2006-01-01

    In maize (Zea mays), nitrogen (N) remobilization and postflowering N uptake are two processes that provide amino acids for grain protein synthesis. To study the way in which N is allocated to the grain and to the stover, two different 15N-labelling techniques were developed. 15NO(3-) was provided to the soil either at the beginning of stem elongation or after silking. The distribution of 15N in the stover and in the grain was monitored by calculating relative 15N-specific allocation (RSA). A nearly linear relationship between the RSA of the kernels and the RSA of the stover was found as a result of two simultaneous N fluxes: N remobilization from the stover to the grain, and N allocation to the stover and to the grain originating from N uptake. By modelling the 15N fluxes, it was possible to demonstrate that, as a consequence of protein turnover, a large proportion of the amino acids synthesized from the N taken up after silking were integrated into the proteins of the stover, and these proteins were further hydrolysed to provide N to the grain. PMID:17096795

  10. {sup 15}N(p,{alpha}{sub 0}){sup 12}C S factor

    SciTech Connect

    Barker, F. C.

    2008-10-15

    Experimental values of the astrophysical S factor for the {sup 15}N(p,{alpha}{sub 0}){sup 12}C reaction are available both from direct measurements and from the Trojan horse method. We here use R-matrix formulas to fit these values and to extrapolate to zero energy to obtain values of S(0)

  11. 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...

  12. 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 ...

  13. Tracing the slow growth of anaerobic methane-oxidizing communities by (15)N-labelling techniques.

    PubMed

    Krger, Martin; Wolters, Heike; Gehre, Matthias; Joye, Samantha B; Richnow, Hans-Hermann

    2008-03-01

    The anaerobic oxidation of methane (AOM) is an important methane sink in marine ecosystems mediated by still uncultured Archaea. We established an experimental system to grow AOM communities in different sediment samples. Approaches to show growth of the slow-growing anaerobic methanotrophs have been either via nucleic acids (quantitative PCR) or required long-term incubations. Previous long-term experiments with (13)C-labelled methane led to an unspecific distribution of the (13)C-label. Although quantitative PCR is a sensitive technique to detect small changes in community composition, it does not determine growth yield. Therefore, we tested an alternative method to detect a biomass increase of AOM microorganisms with (15)N-labelled ammonium as N-source. After only 3 weeks, significant (15)N-labelling became apparent in amino acids as major structural units of microbial proteins. This was especially evident in methane-containing incubations, showing the methane-dependent uptake of the (15)N-labelled ammonium by microorganisms. Cell counts demonstrated a two- and fourfold increase at ambient or elevated methane concentrations. With denaturing gradient gel electrophoresis, over 6 months incubation no changes in community composition of sulphate-reducing bacteria and archaea were detected. These data indicate doubling times for AOM microorganisms between 2 and 3.4 months. In conclusion, the (15)N-labelling approach proved to be a sensitive and fast way to show growth of extremely slow-growing microorganisms. PMID:18269633

  14. 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...

  15. 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

  16. Benchmark Theoretical and Experimental Study on (15)N NMR Shifts of Oxidatively Damaged Guanine.

    PubMed

    Dra?nsk, Martin; la, Michal; Klepet?ov, Blanka; ebera, Jakub; Fukal, Ji?; Hole?kov, Veronika; Tanaka, Yoshiyuki; Nencka, Radim; Sychrovsk, Vladimr

    2016-02-11

    The (15)N NMR shifts of 9-ethyl-8-oxoguanine (OG) were calculated and measured in liquid DMSO and in crystal. The OG molecule is a model for oxidatively damaged 2'-deoxyguanosine that occurs owing to oxidative stress in cell. The DNA lesion is repaired with human 8-oxoguanine glycosylase 1 (hOGG1) base-excision repair enzyme, however, the exact mechanism of excision of damaged nucleobase with hOGG1 is currently unknown. This benchmark study on (15)N NMR shifts of OG aims their accurate structural interpretation and calibration of the calculation protocol utilizable in future studies on mechanism of hOGG1 enzyme. The effects of NMR reference, DFT functional, basis set, solvent, structure, and dynamics on calculated (15)N NMR shifts were first evaluated for OG in crystal to calibrate the best performing calculation method. The effect of large-amplitude motions on (15)N NMR shifts of OG in liquid was calculated employing molecular dynamics. The B3LYP method with Iglo-III basis used for B3LYP optimized geometry with 6-311++G(d,p) basis and including effects of solvent and molecular dynamic was the calculation protocol used for calculation of (15)N NMR shifts of OG. The NMR shift of N9 nitrogen of OG was particularly studied because the atom is involved in an N-glycosidic bond that is cleaved with hOGG1. The change of N9 NMR shift owing to oxidation of 9-ethylguanine (G) measured in liquid was -27.1 ppm. The calculated N9 NMR shift of OG deviated from experiment in crystal and in liquid by 0.45 and 0.65 ppm, respectively. The calculated change of N9 NMR shift owing to notable N9-pyramidalization of OG in one previously found polymorph was 20.53 ppm. We therefore assume that the pyramidal geometry of N9 nitrogen that could occur for damaged DNA within hOGG1 catalytic site might be detectable with (15)N NMR spectroscopy. The calculation protocol can be used for accurate structural interpretation of (15)N NMR shifts of oxidatively damaged guanine DNA residue. PMID:26727398

  17. 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, Agns.

    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 missionthe Rocknest sand, and the John Klein and Cumberland drill fines, both extracted from the Sheepbed mudstoneshow 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.

  18. Variable δ15N 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 δ15N 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 δ15N dietary values). Overall, the most suitable species-specific ∆15N values decreased with increasing dietary-δ15N 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 δ15N = 9‰) whereas a ∆15N value < 2.3‰ provided the highest percent overlap between prey and predator isotope ellipses for the white shark (mean diet δ15N = 15‰). These data corroborate the previously reported inverse ∆15N-dietary δ15N 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’ δ15N-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

  19. 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

    2016-03-01

    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.

  20. 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.

  1. Heavy ? 15N in Intertidal Benthic Algae and Invertebrates in the Scheldt Estuary (The Netherlands): Effect of River Nitrogen Inputs

    NASA Astrophysics Data System (ADS)

    Riera, P.; Stal, L. J.; Nieuwenhuize, J.

    2000-09-01

    The study investigated ? 15N in the intertidal benthic food webs from the middle Westerschelde Estuary and the middle Oosterschelde. Much heavier ? 15N values were observed for the main benthic primary producers and invertebrates in the Westerschelde Estuary. In the Oosterschelde, mean ? 15N values ranged from 14 to 73 for SOM and suspended POM, respectively, to 63 to 91 for Fucus vesiculosus and benthic diatoms, respectively. Mean ? 15N values in benthic invertebrates ranged from 97 for Gammarus locusta to 154 for Tubificoides sp. In the Westerschelde Estuary, mean ? 15N increased from 81 to 86 for suspended POM and SOM, respectively, to heavier ? 15N from 159 to 285 for F. vesiculosus and benthic diatoms, respectively. Mean ? 15N for intertidal invertebrates ranged from 181 for Lumbricillus sp. to 207 for Eulimnogammarus obtusatus. Higher enrichment in 15N in benthic primary producers and invertebrates from the Westerschelde Estuary are most likely due to the incorporation of 15N-enriched DIN carried by the Scheldt River by benthic algae and, then by benthic consumers. These results point to the fact that ? 15N in benthic estuarine food webs may respond directly to anthropogenic nitrogen inputs delivered into estuaries by rivers which drain highly urbanized areas.

  2. Rapid and automated processing of MALDI-FTICR/MS data for 15N-metabolic labeling in a shotgun proteomics analysis

    NASA Astrophysics Data System (ADS)

    Jing, Li; Amster, I. Jonathan

    2009-10-01

    Offline high performance liquid chromatography combined with matrix assisted laser desorption and Fourier transform ion cyclotron resonance mass spectrometry (HPLC-MALDI-FTICR/MS) provides the means to rapidly analyze complex mixtures of peptides, such as those produced by proteolytic digestion of a proteome. This method is particularly useful for making quantitative measurements of changes in protein expression by using 15N-metabolic labeling. Proteolytic digestion of combined labeled and unlabeled proteomes produces complex mixtures with many mass overlaps when analyzed by HPLC-MALDI-FTICR/MS. A significant challenge to data analysis is the matching of pairs of peaks which represent an unlabeled peptide and its labeled counterpart. We have developed an algorithm and incorporated it into a computer program which significantly accelerates the interpretation of 15N-metabolic labeling data by automating the process of identifying unlabeled/labeled peak pairs. The algorithm takes advantage of the high resolution and mass accuracy of FTICR mass spectrometry. The algorithm is shown to be able to successfully identify the 15N/14N peptide pairs and calculate peptide relative abundance ratios in highly complex mixtures from the proteolytic digest of a whole organism protein extract.

  3. NATURAL VARIATION IN ABUNDANCE OF SALMONID POPULATIONS IN STREAMS AND ITS IMPLICATIONS FOR DESIGN OF IMPACT STUDIES. A REVIEW

    EPA Science Inventory

    Literature on stock size and production of salmonid populations in streams has been reviewed. The objective is to bring together data on the magnitude of natural variation in population size and to relate this variability to environmental conditions where possible. Recommendation...

  4. **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.

  5. Isotopic variability of cave bears (δ15N, δ13C) 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 (δ13C) and nitrogen (δ15N). 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 δ13C and δ15N 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 δ13C and δ15N 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 δ13C and δ15N 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 δ13C, 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 δ13C; and two Romanian sites Peştera cu Oase and Urşilor - in case of δ15N. 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 δ15N 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. 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

  7. 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, Tom; Irigoyen, Juan J; Garcia-Olaverri, Carmen; Nogus, 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 +4C) 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

  8. 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 mol/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.

  9. Leaf δ15N 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 (δ15N) 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 δ15N 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 μmol 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 δ15N 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 μmol mol−1 [CO2] and WD conditions. In summary, leaf δ15N provides relevant information integrating parameters which condition plant responsiveness (e.g., photosynthesis, TSP, N demand, and water transpiration) to environmental conditions. PMID:26322051

  10. Sensitivity enhancement in natural-abundance solid-state 33S MAS NMR spectroscopy employing adiabatic inversion pulses to the satellite transitions.

    PubMed

    Hansen, Michael Ryan; Brorson, Michael; Bildsøe, Henrik; Skibsted, Jørgen; Jakobsen, Hans J

    2008-02-01

    The WURST (wideband uniform rate smooth truncation) and hyperbolic secant (HS) pulse elements have each been employed as pairs of inversion pulses to induce population transfer (PT) between the four energy levels in natural abundance solid-state (33)S (spin I=3/2) MAS NMR, thereby leading to a significant gain in intensity for the central transition (CT). The pair of inversion pulses are applied to the satellite transitions for a series of inorganic sulfates, the sulfate ions in the two cementitious materials ettringite and thaumasite, and the two tetrathiometallates (NH(4))(2)WS(4) and (NH(4))(2)MoS(4). These materials all exhibit (33)S quadrupole coupling constants (C(Q)) in the range 0.1-1.0 MHz, with precise C(Q) values being determined from analysis of the PT enhanced (33)S MAS NMR spectra. The enhancement factors for the WURST and HS elements are quite similar and are all in the range 1.74-2.25 for the studied samples, in excellent agreement with earlier reports on HS enhancement factors (1.6-2.4) observed for other spin I=3/2 nuclei with similar C(Q) values (0.3-1.2 MHz). Thus, a time saving in instrument time by a factor up to five has been achieved in natural abundance (33)S MAS NMR, a time saving which is extremely welcome for this important low-gamma nucleus. PMID:18082436

  11. The RGB and AGB Star Nucleosynthesis in Light of the Recent 17O(p, ?)14N and 18O(p, ?)15N Reaction-rate Determinations

    NASA Astrophysics Data System (ADS)

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Spitaleri, C.

    2013-02-01

    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 18O(p, ?)15N and 17O(p, ?)14N reactions, respectively, have been extracted, as well as the contribution of the tail of the broad 656 keV resonance in the 18O(p, ?)15N reaction inside the Gamow window. The strength of the 65 keV resonance in the 17O(p, ?)14N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the 17O + p radiative capture channel. As a result, more accurate reaction rates for the 18O(p, ?)15N, 17O(p, ?)14N, and 17O(p, ?)18F 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 14N/15N found in SiC grains cannot be explained by the revised nuclear reaction rates and remains a serious problem that has not been satisfactorily addressed.

  12. A Survey of \\delta18O and \\delta15N Ratios in Ground Water from an Agricultural Community in the San Joaquin Valley, California

    NASA Astrophysics Data System (ADS)

    Glowacki, S. D.; Suen, C. J.

    2004-12-01

    We studied ground water samples from domestic and monitoring wells in an agricultural community in the eastern side of the San Joaquin Valley, California. The study area is rich in alluvial soils creating an extremely fertile farmland. Livestock farms and agricultural fields are abundant in the area. Fifty-four ground water samples were analyzed for \\delta18O and \\delta15N in dissolved nitrate, in addition to nutrients and major minerals. Nitrate concentration levels in groundwater are elevated and affected by agricultural and other activities. Possible sources of nutrients include: a municipal waste-water treatment facility, a raisin processing plant, a meat processing plant, a turkey farm, diary operations, and agricultural fields. However, except for the turkey farm and a diary, we found no statistical significant contribution of nitrate from the other facilities as compared to the rest of the area. The \\delta18O versus \\delta15N ratios plot of dissolved ground water nitrate shows most samples clustered around an area consistent with soil organic nitrogen. In addition, the rest of the samples show a trend that is indicative of denitrification process. Generally, high \\delta15N values are associated with low nitrate concentrations. The isotopic signal of denitrification is particularly pronounced in samples in the vicinity of the waste water treatment facility, where the highest values of \\delta15N and the lowest nitrate concentrations are observed. However, these samples also have elevated chloride concentrations indicating a waste-water source. These data suggest that the denitrification in the subsurface may have been enhanced by bacteria species introduced by the effluence of the plant. [This study was performed with the collaboration of Steven R Silva of USGS, Menlo Park, and Iris Yamagata and Holly Jo Ferrin of California Department of Water Resources.

  13. Macrophytes as indicators of land-derived wastewater: Application of a ?15N method in aquatic systems

    NASA Astrophysics Data System (ADS)

    Cole, Marci L.; Kroeger, Kevin D.; McClelland, James W.; Valiela, Ivan

    2005-01-01

    We measured ?15N signatures of macrophytes and particulate organic matter (POM) in six estuaries and three freshwater ponds of Massachusetts to assess whether the signatures could be used as indicators of the magnitude of land-derived nitrogen loads, concentration of dissolved inorganic nitrogen in the water column, and percentage of N loads contributed by wastewater disposal. The study focused specifically on sites on Cape Cod and Nantucket Island, in the northeastern United States. There was no evidence of seasonal changes in ?15N values of macrophytes or POM. The ?15N values of macrophytes and POM increased as water column dissolved inorganic nitrogen concentrations increased. We found that ?15N of macrophytes, but not of POM, increased as N load increased. The ?15N values of macrophytes and groundwater NO3 tracked the percent of wastewater contribution linearly. This research confirms that ?15N values of macrophytes and NO3 can be excellent indicators of anthropogenic N in aquatic systems.

  14. Nitrogen cycling in an extreme hyperarid environment inferred from δ15N analyses of plants, soils and herbivore diet

    PubMed Central

    Díaz, Francisca P.; Frugone, Matías; Gutiérrez, Rodrigo A.; Latorre, Claudio

    2016-01-01

    Climate controls on the nitrogen cycle are suggested by the negative correlation between precipitation and δ15N values across different ecosystems. For arid ecosystems this is unclear, as water limitation among other factors can confound this relationship. We measured herbivore feces, foliar and soil δ15N and δ13C values and chemically characterized soils (pH and elemental composition) along an elevational/climatic gradient in the Atacama Desert, northern Chile. Although very positive δ15N values span the entire gradient, soil δ15N values show a positive correlation with aridity as expected. In contrast, foliar δ15N values and herbivore feces show a hump-shaped relationship with elevation, suggesting that plants are using a different N source, possibly of biotic origin. Thus at the extreme limits of plant life, biotic interactions may be just as important as abiotic processes, such as climate in explaining ecosystem δ15N values. PMID:26956399

  15. Nitrogen cycling in an extreme hyperarid environment inferred from δ(15)N analyses of plants, soils and herbivore diet.

    PubMed

    Díaz, Francisca P; Frugone, Matías; Gutiérrez, Rodrigo A; Latorre, Claudio

    2016-01-01

    Climate controls on the nitrogen cycle are suggested by the negative correlation between precipitation and δ(15)N values across different ecosystems. For arid ecosystems this is unclear, as water limitation among other factors can confound this relationship. We measured herbivore feces, foliar and soil δ(15)N and δ(13)C values and chemically characterized soils (pH and elemental composition) along an elevational/climatic gradient in the Atacama Desert, northern Chile. Although very positive δ(15)N values span the entire gradient, soil δ(15)N values show a positive correlation with aridity as expected. In contrast, foliar δ(15)N values and herbivore feces show a hump-shaped relationship with elevation, suggesting that plants are using a different N source, possibly of biotic origin. Thus at the extreme limits of plant life, biotic interactions may be just as important as abiotic processes, such as climate in explaining ecosystem δ(15)N values. PMID:26956399

  16. Determining the content and 13C abundance of total dissolved carbon in water samples by TOC analyser-mass spectrometer coupling.

    PubMed

    Russow, R; Apelt, B

    2003-12-01

    A combined system consisting of a TOC analyser connected to a quadrupole MS was recently described as a way of measuring the N content and the 15N abundance of total dissolved nitrogen in aqueous samples. This work examines whether this combination of instruments can also be used for the 13C determination of the total dissolved carbon in aqueous samples. A level of precision good for 13C-enriched samples was achieved with a relative standard deviation of <3%. By using an isotope ratio MS instead of the quadrupole MS employed here, TOC-MS coupling also ought to be suitable for determining natural 13C abundances. PMID:14711176

  17. Catalytic Roles of ?Lys87 in Tryptophan Synthase: 15N Solid State NMR Studies

    PubMed Central

    Caulkins, Bethany G.; Yang, Chen; Hilario, Eduardo; Fan, Li; Dunn, Michael F.; Mueller, Leonard J.

    2015-01-01

    The proposed mechanism for tryptophan synthase shows ?Lys87 playing multiple catalytic roles: it bonds to the PLP cofactor, activates C4? for nucleophilic attack via a protonated Schiff base nitrogen, and abstracts and returns protons to PLP-bound substrates (i.e. acid-base catalysis). ?-15N-lysine TS was prepared to access the protonation state of ?Lys87 using 15N solid-state nuclear magnetic resonance (SSNMR) spectroscopy for three quasi-stable intermediates along the reaction pathway. These experiments establish that the protonation state of the ?-amino group switches between protonated and neutral states as the ?-site undergoes conversion from one intermediate to the next during catalysis, corresponding to mechanistic steps where this lysine residue has been anticipated to play alternating acid and base catalytic roles that help steer reaction specificity in tryptophan synthase catalysis. PMID:25688830

  18. 1H, 13C and 15N NMR assignments of phenazopyridine derivatives.

    PubMed

    Burgueo-Tapia, Eleuterio; Mora-Prez, Yolanda; Morales-Ros, Martha S; Joseph-Nathan, Pedro

    2005-03-01

    Phenazopyridine hydrochloride (1), a drug in clinical use for many decades, and some derivatives were studied by one- and two-dimensional (1)H, (13)C and (15)N NMR methodology. The assignments, combined with DFT calculations, reveal that the preferred protonation site of the drug is the pyridine ring nitrogen atom. The chemoselective acetylation of phenazopyridine (2) and its influence on the polarization of the azo nitrogen atoms were evidenced by the (15)N NMR spectra. Molecular calculations of the phenazopyridines 2-4 show that the pyridine and phenyl groups are oriented in an antiperiplanar conformation with intramolecular hydrogen bonding between the N-b atom and the C-2 amino group preserving the E-azo stereochemistry. PMID:15625718

  19. Measurement of the neutron capture cross sections of {sup 15}N and {sup 18}O

    SciTech Connect

    Meissner, J.; Schatz, H.; Herndl, H.; Wiescher, M.; Beer, H.; Kaeppeler, F.

    1995-02-05

    Preliminary experimental results are presented for neutron capture cross sections of {sup 15}N and {sup 18}O for neutron energies of 25, 152, 250, and 371 keV. The cross sections were used to calculate the capture reaction rates at stellar temperatures, around 0.1--1.0 GK. (AIP) {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  20. SEARCH FOR AN 80-ms SPONTANEOUS FISSION ACTIVITY IN BOMBARDMENTS OF 249Bk WITH 15N

    SciTech Connect

    Nitschke, J.M.; Fowler, M.; Ghiorso, A.; Leber, R.E.; Nurmia, M.J.; Somerville, L.P.; Williams, K.E.; Hulet, E.K.; Landrum, J.H.; Lougheed, R.W.; Wild, J.F.; Bemis, Jr., C.E.; Silva, R.J.; Eskola, P.

    1980-01-01

    A rotating drum system was used to search for an 80-ms spontaneous fission (sf) activity in the reaction of {sup 15}N with {sup 249}Bk. No such activity was found beyond a cross section limit of 0.3 {+-} 0.3 nb. A sf activity with a half-life of about 20 ms and a formation cross section of 12 nb at 82 MeV was observed. The identity of this activity has not been determined.

  1. The CN/C15N isotopic ratio towards dark clouds

    NASA Astrophysics Data System (ADS)

    Hily-Blant, P.; Pineau des Forts, G.; Faure, A.; Le Gal, R.; Padovani, M.

    2013-09-01

    Understanding the origin of the composition of solar system cosmomaterials is a central question, not only in the cosmochemistry and astrochemistry fields, and requires various approaches to be combined. Measurements of isotopic ratios in cometary materials provide strong constraints on the content of the protosolar nebula. Their relation with the composition of the parental dark clouds is, however, still very elusive. In this paper, we bring new constraints based on the isotopic composition of nitrogen in dark clouds, with the aim of understanding the chemical processes that are responsible for the observed isotopic ratios. We have observed and detected the fundamental rotational transition of C15N towards two starless dark clouds, L1544 and L1498. We were able to derive the column density ratio of C15N over 13CN towards the same clouds and obtain the CN/C15N isotopic ratios, which were found to be 500 75 for both L1544 and L1498. These values are therefore marginally consistent with the protosolar value of 441. Moreover, this ratio is larger than the isotopic ratio of nitrogen measured in HCN. In addition, we present model calculations of the chemical fractionation of nitrogen in dark clouds, which make it possible to understand how CN can be deprived of 15N and HCN can simultaneously be enriched in heavy nitrogen. The non-fractionation of N2H+, however, remains an open issue, and we propose some chemical way of alleviating the discrepancy between model predictions and the observed ratios. Appendices are available in electronic form at http://www.aanda.orgThe reduced spectra (in FITS format) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/557/A65

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

    NASA Astrophysics Data System (ADS)

    Hellmann, Christine; Rascher, Katherine G.; Mguas, 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.

  3. 15N and 13C NMR Determination of Allantoin Metabolism in Developing Soybean Cotyledons 1

    PubMed Central

    Coker, George T.; Schaefer, Jacob

    1985-01-01

    The metabolism of allantoin by immature cotyledons of soybean (Glycine max L. cv Elf) grown in culture was investigated using solid state 13C and 15N nuclear magnetic resonance. All of the nitrogens of allantoin were incorporated into protein in a manner similar to that of each other and to the amide nitrogen of glutamine. The C-2 of allantoin was not incorporated into cellular material; presumably it was lost as CO2. About 50% of the C-5 of allantoin was incorporated into cellular material as a methylene carbon; the other 50% was presumably also lost as CO2. The 13C-15N bonds of [5-13C;1-15N] and [2-13C;1,3-15N]allantoin were broken prior to the incorporation of the nitrogens into protein. These data are consistent with allantoin's degradation to two molecules of urea and one two-carbon fragment. Cotyledons grown on allantoin as a source of nitrogen accumulated 21% of the nitrogen of cotyledons grown on glutamine. Only 50% of the nitrogen of the degraded allantoin was incorporated into the cotyledon as organic nitrogen; the other 50% was recovered as NH4+ in the media in which the cotyledons had been grown. The latter results suggests that the lower accumulation of nitrogen by cotyledons grown on allantoin was in part due to failure to assimilate NH4+ produced from allantoin. The seed coats had a higher activity of glutamine synthetase and a higher rate of allantoin degradation than cotyledons indicating that seed coats play an important role in the assimilation and degradation of allantoin. PMID:16663995

  4. 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 δ15N signatures relative to their conspecifics from Belongil Creek, indicating that sewage nitrogen had been assimilated and transferred throughout the Tallows Creek food web. These δ15N 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.

  5. δ15N in the turtle grass from the Mexican Caribbean

    NASA Astrophysics Data System (ADS)

    Talavera-Saenz, A.; Sanchez, A.; Ortiz-Hernandez, M.

    2013-05-01

    Nutrient inputs associated with population growth threaten the integrity of coastal ecosystems. To assess the rapid increase in tourism, we compared the δ15N from Thalassia testudinum collected at sites with different levels of tourism development and population to detect the N inputs of wastewater discharge (WD) along the coast of Quintana Roo. The contributions of nitrogen enriched in 15N are directly related to the increase of WD inputs in areas of high tourism development (Nichupte Lagoon in Cancun, >3 million tourists per year from 2007 to 2011 and 0.7 million of resident population) and decreased towards Bahia Akumal and Tulum (>3 million tourists per year from 2007 to 2011 and 0.15 million of resident population). The δ15N from T. testudinum was significantly lower at Mahahual and Puerto Morelos (about 0.4 million tourists per year in 2007 to 2011 and 0.25 million of resident population) than other the sites. In areas of the lowest development and with tourist activity restricted and small population, such as the Yum Balam Reserve and Sian Ka'an Biosphere Reserve, the δ15N values were in much higher enrichment that Mahahual and Puerto Morelos. Therefore is suggested that Mahahual and Puerto Morelos may be used for baseline isotopic monitoring, over environmental pressure on the reef lagoon ecosystem, where tourist activities and population are growing very slow rate. The anthropogenic N input has the potential to impact, both environmentally and economically, the seagrass meadows and the coral reefs along the coast of Quintana Roo and the Caribbean.

  6. Determination of the δ15N 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 δ(15N/14N), abbreviated as δ15N , 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.

  7. 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 994% (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 6.70.7 ?gC, and a blank isotopic value of 0.540.05 fMC. The size of the blank agreed well with that determined directly by processing variable volumes of UV-irradiated deionized water (5.60.7 ?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.

  8. 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

  9. 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 Δ14C value for PLFAs ranged from +54 to -697% which indicates that microbial carbon sources across soils differ. The Δ14CPLFA for some soils is consistent with modern carbon sources while Δ14CPLFA 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.

  10. Directly observed /sup 15/N NMR spectra of uniformly enriched proteins

    SciTech Connect

    Smith, G.M.; Yu, L.P.; Domingues, D.J.

    1987-04-21

    The proteins cytochrome c/sub 2/, cytochrome c', and ribulosebisphosphate carboxylase/oxygenase from Rhodospirillum rubrum were enriched in /sup 15/N by growth of the organism on /sup 15/NH/sub 4/Cl. The proteins were purified to homogeneity and studied by /sup 15/N NMR. Longitudinal and transverse relaxation times as well as the nuclear Overhauser effects were determined for various groups of the proteins which vary in molecular weight from 13,000 to 114,000. The values of these parameters for the amide resonances or for groups thought to be rigid were consistent with the molecular weights of the proteins. Relaxation times of the amino-terminal ..cap alpha..-amino groups and the side chain nitrogen atoms of arginine and lysine were consistent with much more rapid motion. Nitrogen atoms having bound protons were generally found to be decoupled from the protons by chemical exchange. Demonstrable /sup 1/H-/sup 15/N coupling was taken as an indication that exchange was hindered, either by hydrogen bonding interactions or by inaccessibility of the group to solvent. Histidine side chain nitrogen atoms, which experience a large chemical shift upon protonation/deprotonation, were often found to be broadened beyond detectability by chemical shift upon protonation/deprotonation, were often found to be broadened beyond detectability by chemical exchange and tautomerization. Strategies for improving sensitivity and for obtaining specific peak assignments are also discussed.

  11. Method for the Determination of (15)N Incorporation Percentage in Labeled Peptides and Proteins.

    PubMed

    Kilpatrick, Eric L

    2016-01-01

    Use of labeled (15)N proteins and peptides as internal standards in isotope-dilution mass spectrometry for the quantification of proteins has been increasing and is now accepted as a gold standard for this analysis. As a necessary reagent in this process, stable heavy isotope-labeled internal standards must be rigorously characterized in a number of ways including identity, concentration, purity, and structure. Additionally, the degree of the incorporation of the heavy isotope is a critical feature to consider. For proteins that are (15)N labeled, the percentage of incorporation is a valid measurement used to assess the fitness-to-purpose of the material. This measurement should be objective, repeatable, and based on empirical analysis. One means of assigning this value is to compare a mass spectrum of the isotopic profile of a peptide against a series of theoretical profiles containing different enrichment rates. This comparison can be made using the Pearson product-moment correlation coefficient (r) to find the best match between the empirical and theoretical profiles. Theoretical profiles can be generated using probability multinomial analysis but are computationally intensive and require the use of computers for practical use. The method described in this chapter describes the development and use of a computer program to calculate the percentage of (15)N enrichment of a labeled internal standard. Additionally, methods will be described for the empirical determination of an isotopic profile using a variety of mass spectrometry techniques. PMID:26791983

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

    PubMed

    Lemesle, Stphanie; Mussio, Isabelle; Rusig, Anne-Marie; Menet-Ndlec, 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

  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, Hansjrg; 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. Foliar ?15N is affected by foliar nitrogen uptake, soil nitrogen, and mycorrhizae along a nitrogen deposition gradient.

    PubMed

    Vallano, Dena M; Sparks, Jed P

    2013-05-01

    Foliar nitrogen isotope (?(15)N) composition patterns have been linked to soil N, mycorrhizal fractionation, and within-plant fractionations. However, few studies have examined the potential importance of the direct foliar uptake of gaseous reactive N on foliar ?(15)N. Using an experimental set-up in which the rate of mycorrhizal infection was reduced using a fungicide, we examined the influence of mycorrhizae on foliar ?(15)N in potted red maple (Acer rubrum) seedlings along a regional N deposition gradient in New York State. Mycorrhizal associations altered foliar ?(15)N values in red maple seedlings from 0.06 to 0.74 across sites. At the same sites, we explored the predictive roles of direct foliar N uptake, soil ?(15)N, and mycorrhizae on foliar ?(15)N in adult stands of A. rubrum, American beech (Fagus grandifolia), black birch (Betula lenta), and red oak (Quercus rubra). Multiple regression analysis indicated that ambient atmospheric nitrogen dioxide (NO2) concentration explained 0, 69, 23, and 45 % of the variation in foliar ?(15)N in American beech, red maple, red oak, and black birch, respectively, after accounting for the influence of soil ?(15)N. There was no correlation between foliar ?(13)C and foliar %N with increasing atmospheric NO2 concentration in most species. Our findings suggest that total canopy uptake, and likely direct foliar N uptake, of pollution-derived atmospheric N deposition may significantly impact foliar ?(15)N in several dominant species occurring in temperate forest ecosystems. PMID:23070141

  15. Foliar retention of 15N-nitrate and 15N-ammonium by red maple (Acer rubrum) and white oak (Quercus alba) leaves from simulated rain

    SciTech Connect

    Garten Jr, Charles T; Hanson, Paul J

    1990-07-01

    Studies of nitrogen cycling in forests indicate that trees assimilate atmospheric nitrate and ammonium and that differences between atmospheric deposition to the forest canopy and deposition measured in forest throughfall can be attributed to the removal of these ions from rain by tree leaves. Red maple and white oak leaves were exposed to artificial rain solutions (pH 4.1) containing {sup 15}N-labeled nitrate (3.5 {micro}g N/ml) or ammonium (2.2 {micro}g N/ml). At two time intervals after exposure (2 hr and 2 days) an exposed leaf and a control (non-exposed) leaf were removed from replicate seedlings. Based on results from {sup 15}N analysis, most of the nitrate applied to tree leaves was removed by washing with water; the mean per cent removal ({+-} standard error, N = 4) was 87 {+-} 1 and 73 {+-} 4% of the {sup 15}NO-N Applied to red maple and white oak leaves, respectively. Relative retention of {sup 15}NH{sub 4}-N by the leaves was greater than that observed for {sup 15}NO{sub 3}-N. In red maple and white oak leaves, 58 {+-} 9 and 84 {+-} 7% (mean {+-} standard error, N = 4), respectively, of the applied ammonium was not removed by washing treatments. Our results show that the foliar uptake of {sup 15}NH{sub 4}{sup +} from simulated rain by deciduous tree leaves is greater than that for {sup 15}NO{sub 3}{sup -}. Greater retention of NH{sub 4}{sup +} than NO{sub 3}{sup -} ions by red maple and white oak leaves from simulated rainfall is consistent with field observations showing a preferential retention of ammonium from rainfall by forest canopies. As nitrogen chemistry and the relative importance of nitrogen compounds in the atmosphere change in response to proposed emission reductions (and possibly climate change), an improved understanding of the fate of airborne nitrogen compounds in forest biogeochemical cycles will be necessary.

  16. 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

  17. Unusually negative nitrogen isotopic compositions (δ15N) of mangroves and lichens in an oligotrophic, microbially-influenced ecosystem

    NASA Astrophysics Data System (ADS)

    Fogel, M. L.; Wooller, M. J.; Cheeseman, J.; Smallwood, B. J.; Roberts, Q.; Romero, I.; Meyers, M. J.

    2008-12-01

    Extremes in δ15N values in mangrove tissues and lichens (range =+4 to -22‰) were measured from a mangrove forest ecosystem located on Twin Cays, offshore islands in Belize, Central America. The N isotopic compositions and concentrations of NH4+/NH3 in porewater, rainwater, and atmospheric ammonia, and the δ15N of lichens, mangrove leaves, roots, stems, and wood were examined to study the biogeochemical processes important for establishing these unusual N isotopic ratios. Dwarfed Rhizophora mangle trees had the most negative δ15N, whereas fringing Rhizophora trees, the most positive δ15N values. Porewater ammonium concentrations had little relationship to N isotopic fractionation in mangrove tissues. In dwarfed mangroves, the δ15N of fine and coarse roots were 6-9‰ more positive than leaf tissue from the same tree, indicating different sources of N for root and leaf tissues. When P was added to dwarfed mangrove trees without added N, δ15N increased within one year from -12‰ to -2‰, approaching the δ15N of porewater ammonium (δ15N=+4‰). Isotopically depleted ammonia in the atmosphere (δ15N=-19‰) and in rainwater (δ15N=-10‰) were found on Twin Cays. We propose that foliar uptake of these atmospheric sources by P-stressed, dwarfed mangrove trees and lichens can explain their very negative δ15N values. In environments where P is limiting for growth, uptake of atmospheric N by Rhizophora mangle may be an important adaptive strategy.

  18. 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

  19. Variable Seawater-Peridotite Interactions - First Insights From ODP Leg 209, MAR 15 N

    NASA Astrophysics Data System (ADS)

    Bach, W.; Garrido, C. J.; Harvey, J.; Paulick, H.; Rosner, M.; Odp Leg 193 Shipboard Science Party

    2003-12-01

    Serpentinization of peridotites at slow-spreading mid-ocean ridges has important consequences for the rheology of the oceanic lithosphere, geochemical budgets of the oceans, and microbial processes within, at, and above the seafloor. ODP Leg 209 recovered peridotites that show a remarkable variability of hydrothermal alteration reactions and intensities, including talc-tremolite alteration of pyroxenes associated with incipient serpentinization of olivine, complete alteration of peridotites to serpentine and magnetite followed by the destruction of magnetite and replacement of serpentine by talc, variable degrees of serpentine-brucite alteration, and replacement of brucite by iowaite. These rocks provide a unique opportunity to calibrate our observations against recent results from experimental/theoretical geochemical studies and further our understanding of serpentinization and its role in tectonic accretion and microbial colonization of oceanic lithosphere at slow and ultraslow spreading ridges. We propose that at temperatures above 250 C, pyroxenes react to form serpentine, talc, and tremolite, releasing Ca, Si, H2, and acidity to the reacting fluids that may cause rodingitization in adjacent gabbro bodies. Overall however, rodingites are rare, which may reflect the depleted nature of the mantle protoliths. In the absence of pyroxenes (in dunites) - or at temperatures below 250 C, where pyroxenes react very slowly - the fluids do not become enriched in Ca and Si and serpentine, magnetite, and brucite will form. Many serpentinites lack brucite, tremolite, and talc, because changes in fluid pH and silica activity of the interacting fluids, following the exhaustion of either olivine or pyroxene, caused reaction of these phases to serpentine. Extensive talc alteration of serpentinites and gabbros is usually observed at the intrusive contacts, but large-scale silica metasomatism (or Mg-loss) must be invoked to explain the overall abundance of talc at Site 1268. Significant pyrite/marcasite/hematite veining at Site 1268 indicates fairly oxidizing conditions consistent with the presence of sulfate in the interacting fluids. The first discovery of iowaite in mid-ocean ridge serpentinites (at Site 1272) and the abundant carbonate/Fe-oxyhydroxide alteration, locally extending down to 90 meters below seafloor, indicate that water-rock reactions continue at low temperatures and under strongly oxidizing conditions. Pore fluids from nontronite-bearing serpentine muds in fault gouges may provide information about the nature of these late-stage circulating fluids and potential microbial activity.

  20. 13C Natural Abundance in Serum Retinol Acts as a Biomarker for Increases in Dietary Provitamin A

    PubMed Central

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

    2009-01-01

    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 2150 y of age with a BMI between 3040 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 0.240.35 liter fruits. The caloric reduction group (n = 17) was encouraged to lower caloric intake by 500 kcal and consume ?25% kcal from fat daily. Provided meals supplied 75100% vegetable and fruit goals and 5067% kcal and fat g per day. Carotenoid supplementation was discontinued by subjects during the study. Serum retinol and provitamin A carotenoid concentrations; intake of preformed vitamin A, provitamin A, and fat; and body weight, fat mass, and lean mass were analyzed for correlations to 13C:12C-retinol. 13C:12C-Retinol decreased in the vegetable group after intervention (P = 0.050) and the correlation with provitamin A intake was approaching significance (P = 0.079). 13C:12C-Retinol did not change in the caloric reduction group (P = 0.43). 13C:12C-Retinol changes with the vitamin A source in the diet and can be used as a biomarker for increases in dietary provitamin A vegetable intake. PMID:19116317

  1. 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.

  2. Unusually negative nitrogen isotopic compositions (δ15N) of mangroves and lichens in an oligotrophic, microbially-influenced ecosystem

    NASA Astrophysics Data System (ADS)

    Fogel, M. L.; Wooller, M. J.; Cheeseman, J.; Smallwood, B. J.; Roberts, Q.; Romero, I.; Jacobsen Meyers, M.

    2008-02-01

    Extremes in (δ15N values in mangrove tissues and lichens (range = +4 to -22‰) were measured from a mangrove forest ecosystem located on Twin Cays, offshore islands in Belize, Central America. The N isotopic compositions and concentrations of NH4+/NH3 in porewater, rainwater, atmospheric ammonia, mangrove leaves, roots, stems, and wood, and lichens, were examined to study the biogeochemical processes important for establishing these unusual N isotopic ratios. Porewater ammonium concentrations had little to no relationship to N isotopic fractionation in mangrove tissues. The δ15N of fine and coarse roots was 9‰ more positive than leaf tissue from the same tree. When P was added to dwarfed mangrove trees without added N, δ15N increased within one year to a &delta:15N closer to the &delta:15N of porewater ammonium (δ15N=+4‰). Isotopically negative ammonia in the atmosphere (δ15N=-18‰) and in rainwater (δ15N=-9‰) were found on Twin Cays and may be sources of available N for isotopically depleted mangrove trees and lichens. In highly stressed, severely P limited trees, uptake of atmospheric N by Rhizophora mangle may be an important adaptive strategy.

  3. Growth and foliar d15N of a Mojave desert shrub in relation to soil hydrological dynamics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Foliar 15N ratios (del15N), % N, and canopy volumes were measured in the two Mojave Desert dominant shrubs, the evergreen Larrea tridentata and drought deciduous Ambrosia dumosa growing across a geomorphically determined soil mosaic. Across three soils with increasingly strong age-dependent surface...

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Raimonet, Mlanie; Guillou, Gal; Mornet, Franoise; 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.

  6. 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.

  7. Site-specific 15N isotopic signatures of abiotically produced N2O

    NASA Astrophysics Data System (ADS)

    Heil, Jannis; Wolf, Benjamin; Brüggemann, Nicolas; Emmenegger, Lukas; Tuzson, Béla; Vereecken, Harry; Mohn, Joachim

    2014-08-01

    Efficient nitrous oxide (N2O) mitigation strategies require the identification of the main source and sink processes and their contribution to total soil N2O production. Several abiotic reactions of nitrification intermediates leading to N2O production are known, but their contribution to total N2O production in soils is uncertain. As the site preference (SP) of 15N in N2O is a promising tool to give more insight into N2O production processes, we investigated the SP of N2O produced by different abiotic reactions in a laboratory study. All reactions involved the nitrification intermediate hydroxylamine (NH2OH) in combination with nitrite (NO2-), Fe3+, Fe2+ and Cu2+, reactants commonly or potentially found in soils, at different concentrations and pH values. N2O production and its four main isotopic species (14N14N16O, 15N14N16O, 14N15N16O, and 14N14N18O) were quantified simultaneously and online at high temporal resolution using quantum cascade laser absorption spectroscopy. Thereby, our study presents the first continuous analysis of δ18O in N2O. The experiments revealed the possibility of purely abiotic reactions over a wide range of acidity (pH 3-8) by different mechanisms. All studied abiotic pathways produced N2O with a characteristic SP in the range of 34-35‰, unaffected by process conditions and remaining constant over the course of the experiments. These findings reflect the benefit of continuous N2O isotopic analysis by laser spectroscopy, contribute new information to the challenging source partitioning of N2O emissions from soils, and emphasize the potentially significant role of coupled biotic-abiotic reactions in soils.

  8. Nitrate Reduction in a Groundwater Microcosm Determined by 15N Gas Chromatography-Mass Spectrometry

    PubMed Central

    Bengtsson, Gran; Annadotter, Helne

    1989-01-01

    Aerobic and anaerobic groundwater continuous-flow microcosms were designed to study nitrate reduction by the indigenous bacteria in intact saturated soil cores from a sandy aquifer with a concentration of 3.8 mg of NO3?-N liter?1. Traces of 15NO3? were added to filter-sterilized groundwater by using a Darcy flux of 4 cm day?1. Both assimilatory and dissimilatory reduction rates were estimated from analyses of 15N2, 15N2O, 15NH4+, and 15N-labeled protein amino acids by capillary gas chromatography-mass spectrometry. N2 and N2O were separated on a megabore fused-silica column and quantified by electron impact-selected ion monitoring. NO3? and NH4+ were analyzed as pentafluorobenzoyl amides by multiple-ion monitoring and protein amino acids as their N-heptafluorobutyryl isobutyl ester derivatives by negative ion-chemical ionization. The numbers of bacteria and their [methyl-3H]thymidine incorporation rates were simultaneously measured. Nitrate was completely reduced in the microcosms at a rate of about 250 ng g?1 day?1. Of this nitrate, 80 to 90% was converted by aerobic denitrification to N2, whereas only 35% was denitrified in the anaerobic microcosm, where more than 50% of NO3? was reduced to NH4+. Assimilatory reduction was recorded only in the aerobic microcosm, where N appeared in alanine in the cells. The nitrate reduction rates estimated for the aquifer material were low in comparison with rates in eutrophic lakes and coastal sediments but sufficiently high to remove nitrate from an uncontaminated aquifer of the kind examined in less than 1 month. PMID:16348048

  9. Foliar uptake of wet-deposited nitrogen by norway spruce. an experiment using 15N

    NASA Astrophysics Data System (ADS)

    Wilson, E. J.; Tiley, C.

    High rates of atmospheric nitrogen deposition have been shown to cause forest decline in some areas. A number of soil-mediated damage mechanisms are well-characterised but much less is known about the role of direct uptake of N by the canopy. The stable 15N isotope has been used in this experiment to quantify the assimilation of wet-deposited N by foliage and branches of 5 yr old Norway spruce trees. The effect of nutrient status (P and K) on N uptake was also investigated. Simulated rain solutions containing 99 atom% 15NH +4-N or 99 atom% 15NO -3-N at 15 mg N ℓ -1 were applied as a fine mist for 0.5 h. Woody twigs, current needles and current +1 year needles were sampled before and after misting and analysed for 15N enrichment and total N by automated mass spectrometry. All three tissue types showed some capacity for uptake of both 15NO -3-N and 15NH +4-N, although in nitrate treatments, N absorption was only statistically significant in woody twigs. Uptake rates were significantly higher in twigs compared with needles and in ammonium treatments compared with nitrate treatments, but only in PK fertilised trees. The concentrations of P and K in spruce foliage did not significantly affect the amount of N taken up by the canopy. Extrapolation of these data to mature forests suggests that foliar uptake is unlikely to exceed about 5% of annual N requirements, and will only make a small contribution to "N-saturation" of vegetation. The results of this experiment indicate that absorption of N by branches and twigs could potentially make an important contribution to total N requirements, although uptake may have been overestimated as it was not possible to differentiate between biological uptake of 15N and retention in the bark.

  10. 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 δ13C 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 (δ13C = -10.59‰); 2. maltodextrin (δ13C = -23.95‰); 3. a 50-50 mixture of the two (δ13C = -15.94‰). After 24 days of feeding, subjects showed enrichment in blood serum that was significantly correlated (p = 0.0038) with the δ13C 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 δ13C 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 (δ13C = - 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 δ13C 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.

  11. 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 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.

  12. 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.

  13. (13)C and (15)N solid-state NMR studies on albendazole and cyclodextrin albendazole complexes.

    PubMed

    Ferreira, M Joo G; Garca, A; Leonardi, D; Salomon, Claudio J; Lamas, M Celina; Nunes, Teresa G

    2015-06-01

    (13)C and (15)N solid-state nuclear magnetic resonance (NMR) spectra were recorded from albendazole (ABZ) and from ABZ:?-cyclodextrin, ABZ:methyl-?-cyclodextrin, ABZ:hydroxypropyl-?-cyclodextrin and ABZ:citrate-?-cyclodextrin, which were prepared by the spray-drying technique. ABZ signals were typical of a crystalline solid for the pure drug and of an amorphous compound obtained from ABZ:cyclodextrin samples. Relevant spectral differences were correlated with chemical interaction between ABZ and cyclodextrins. The number and type of complexes revealed a strong dependence on the cyclodextrin group substituent. Solid-state NMR data were consistent with the presence of stable inclusion complexes. PMID:25843843

  14. Determination of the δ15N 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 δ15N 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 δ15N 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 δ15N values are reported.

  15. Determination of the δ15N 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 δ15N of nitrate (NO3-) in water. The δ15N 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 δ15N values are reported.

  16. 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.

  17. 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 δ15N 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 δ15N 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 δ15N with little variance at ~400 ka through the mid-Turonian. The highest δ15N 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 δ15N cycle and δ15N maxima suggests a strong link between oceanic ventilation/circulation, climate, and the oscillations in δ15N 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 δ15N values, but the exact mechanism of the 15N-depletion remains elusive.

  18. Retrieving nitrogen isotopic signatures from fresh leaf reflectance spectra: disentangling δ15N 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 δ15N 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 δ15N directly influences leaf reflectance spectra or if the relationship is based on covariation between δ15N and foliar nitrogen content or other leaf properties. Using a 15N-labeling approach, we experimentally varied δ15N independently of any other leaf properties in three plant species across different leaf developmental and physiological states. δ15N 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 δ15N within species. Several wavelength regions important for predicting δ15N 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 δ15N, 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

  19. Use of protein trans-splicing to produce active and segmentally 2H, 15N labeled mannuronan C5-epimerase AlgE4

    PubMed Central

    Buchinger, Edith; Aachmann, Finn L; Aranko, A Sesilja; Valla, Svein; Skjk-BrK, Gudmund; Iwa, Hideo; Wimmer, Reinhard

    2010-01-01

    Alginate epimerases are large multidomain proteins capable of epimerising C5 on ?-d-mannuronic acid (M) turning it into ?-l-guluronic acid (G) in a polymeric alginate. Azotobacter vinelandii secretes a family of seven epimerases, each of which is capable of producing alginates with characteristic G distribution patterns. All seven epimerases consist of two types of modules, denoted A and R, in varying numbers. Attempts to study these enzymes with solution-state NMR are hampered by their sizethe smallest epimerase, AlgE4, consisting of one A- and one R-module, is 58 kDa, resulting in heavy signal overlap impairing the interpretation of NMR spectra. Thus we obtained segmentally 2H, 15N labeled AlgE4 isotopomeres (A-[2H, 15N]-R and [2H, 15N]-A-R) by protein trans-splicing using the naturally split intein of Nostoc punctiforme. The NMR spectra of native AlgE4 and the ligated versions coincide well proving the conservation of protein structure. The activity of the ligated AlgE4 was verified by two different enzyme activity assays, demonstrating that ligated AlgE4 displays the same catalytic activity as wild-type AlgE4. PMID:20552686

  20. 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.

  1. 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

  2. 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.

  3. MUSIC in Triple-Resonance Experiments: Amino Acid Type-Selective 1H- 15N Correlations

    NASA Astrophysics Data System (ADS)

    Schubert, Mario; Smalla, Maika; Schmieder, Peter; Oschkinat, Hartmut

    1999-11-01

    Amino acid type-selective triple-resonance experiments can be of great help for the assignment of protein spectra, since they help to remove ambiguities in either manual or automated assignment procedures. Here, modified triple-resonance experiments that yield amino acid type-selective 1H-15N correlations are presented. They are based on novel coherence transfer schemes, the MUSIC pulse sequence elements, that replace the initial INEPT transfer and are selective for XH2 or XH3 (X can be 15N or 13C). The desired amino acid type is thereby selected based on the topology of the side chain. Experiments for Gly (G-HSQC); Ala (A-HSQC); Thr, Val, Ile, and Ala (TAVI-HSQC); Thr and Ala (TA-HSQC), as well as Asn and Gln (N-HSQC and QN-HSQC), are described. The new experiments are recorded as two-dimensional experiments and therefore need only small amounts of spectrometer time. The performance of the experiments is demonstrated with the application to two protein domains.

  4. MUSIC in triple-resonance experiments: amino acid type-selective (1)H-(15)N correlations

    PubMed

    Schubert; Smalla; Schmieder; Oschkinat

    1999-11-01

    Amino acid type-selective triple-resonance experiments can be of great help for the assignment of protein spectra, since they help to remove ambiguities in either manual or automated assignment procedures. Here, modified triple-resonance experiments that yield amino acid type-selective (1)H-(15)N correlations are presented. They are based on novel coherence transfer schemes, the MUSIC pulse sequence elements, that replace the initial INEPT transfer and are selective for XH(2) or XH(3) (X can be (15)N or (13)C). The desired amino acid type is thereby selected based on the topology of the side chain. Experiments for Gly (G-HSQC); Ala (A-HSQC); Thr, Val, Ile, and Ala (TAVI-HSQC); Thr and Ala (TA-HSQC), as well as Asn and Gln (N-HSQC and QN-HSQC), are described. The new experiments are recorded as two-dimensional experiments and therefore need only small amounts of spectrometer time. The performance of the experiments is demonstrated with the application to two protein domains. Copyright 1999 Academic Press. PMID:10527741

  5. Measurement and interpretation of 15N- 1H residual dipolar couplings in larger proteins

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Akash; Revington, Matthew; Zuiderweg, Erik R. P.

    2010-03-01

    A decade ago, Dr. L.E. Kay and co-workers described an ingenious HNCO-based triple-resonance experiment from which several protein backbone RDCs can be measured simultaneously (Yang et al. (1999) [1]). They implemented a J-scaling technique in the 15N dimension of the 3D experiment to obtain the NH RDCs. We have used this idea to carry out J-scaling in a 2D 15N- 1H-TROSY experiment and have found it to be an excellent method to obtain NH RDCs for larger proteins upto 70 kDa, far superior to commonly used HSQC in-phase/anti-phase and HSQC/TROSY comparisons. Here, this method, dubbed "RDC-TROSY" is discussed in detail and the limits of its utility are assessed by simulations. Prominent in the latter analysis is the evaluation of the effect of amide proton flips on the "RDC-TROSY" linewidths. The details of the technical and computational implementations of these methods for the determination of domain orientations in 45-60 kDa Hsp70 chaperone protein constructs are described.

  6. UV-visible and (1)H-(15)N NMR spectroscopic studies of colorimetric thiosemicarbazide anion sensors.

    PubMed

    Farrugia, Kristina N; Makuc, Damjan; Podborska, Agnieszka; Szaci?owski, Konrad; Plavec, Janez; Magri, David C

    2015-02-14

    Four model thiosemicarbazide anion chemosensors containing three N-H bonds, substituted with phenyl and/or 4-nitrophenyl units, were synthesised and studied for their anion binding abilities with hydroxide, fluoride, acetate, dihydrogen phosphate and chloride. The anion binding properties were studied in DMSO and 9?:?1 DMSO-H2O by UV-visible absorption and (1)H/(13)C/(15)N NMR spectroscopic techniques and corroborated with DFT studies. Significant changes were observed in the UV-visible absorption spectra with all anions, except for chloride, accompanied by dramatic colour changes visible to the naked eye. These changes were determined to be due to the deprotonation of the central N-H proton and not due to hydrogen bonding based on (1)H/(15)N NMR titration studies with acetate in DMSO-d6-0.5% water. Direct evidence for deprotonation was confirmed by the disappearance of the central thiourea proton and the formation of acetic acid. DFT and charge distribution calculations suggest that for all four compounds the central N-H proton is the most acidic. Hence, the anion chemosensors operate by a deprotonation mechanism of the central N-H proton rather than by hydrogen bonding as is often reported. PMID:25451865

  7. Precursor discrimination of designer drug benzylpiperazine using ?13C and ?15N stable isotopes.

    PubMed

    Beckett, Nicola M; Grice, Darren I; Carter, James F; Cresswell, Sarah L

    2015-01-01

    Advances in analytical technology and emerging techniques have resulted in the increased exploitation of chemical and isotopic profiling for source linkage/discrimination of illicit drugs for forensic purposes. Although not routinely used for illicit drug investigations, such information has been obtained and its application demonstrated through the use of isotope ratio mass spectrometry (IRMS). There is a solid platform of research available relating to the isotopic analysis of methylenedioxymethamphetamine (MDMA) and methamphetamine (MA), however with the recently flourishing designer drug market it was of interest to examine the isotopic profiles of the popular 'party drug' benzylpiperazine hydrochloride (BZPHCl). A preliminary analysis of ?13C and ?15N isotopic ratios in BZPHCl products and corresponding synthetic intermediates (piperazineHCl) synthesized in-house from three different precursor suppliers was conducted using IRMS. Analysis of the ?13C and ?15N isotopic data indicated that discrimination and correct grouping of all the intermediates and some of the product samples examined in this study were achievable. PMID:25577008

  8. Position-Specific Isotope Analysis of Xanthines: A (13)C Nuclear Magnetic Resonance Method to Determine the (13)C Intramolecular Composition at Natural Abundance.

    PubMed

    Diomande, Didier G; Martineau, Estelle; Gilbert, Alexis; Nun, Pierrick; Murata, Ariaki; Yamada, Keita; Watanabe, Naoharu; Tea, Illa; Robins, Richard J; Yoshida, Naohiro; Remaud, Grald 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

  9. Resonance strengths in the {sup 14}N(p,gamma){sup 15}O and {sup 15}N(p,alphagamma){sup 12}C reactions

    SciTech Connect

    Marta, Michele; Trompler, Erik; Bemmerer, Daniel; Beyer, Roland; Grosse, Eckart; Hannaske, Roland; Junghans, Arnd R.; Nair, Chithra; Schwengner, Ronald; Wagner, Andreas; Yakorev, Dmitry; Broggini, Carlo; Caciolli, Antonio; Erhard, Martin; Menegazzo, Roberto; Fueloep, Zsolt; Gyuerky, Gyoergy; Szuecs, Tamas; Vezzu, Simone

    2010-05-15

    The {sup 14}N(p,gamma){sup 15}O 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 {sup 15}N(p,alphagamma){sup 12}C reaction is frequently used in inverse kinematics for hydrogen depth profiling in materials. The {sup 14}N(p,gamma){sup 15}O and {sup 15}N(p,alphagamma){sup 12}C reactions have been studied simultaneously, using titanium nitride targets of natural isotopic composition and a proton beam. The strengths of the resonances at E{sub p} = 1058 keV in {sup 14}N(p,gamma){sup 15}O and at E{sub p} = 897 and 430 keV in {sup 15}N(p,alphagamma){sup 12}C have been determined with improved precision, relative to the well-known resonance at E{sub p} = 278 keV in {sup 14}N(p,gamma){sup 15}O. The new recommended values are omegagamma=0.353+-0.018, 362+-20, and 21.9+-1.0 eV for their respective strengths. In addition, the branching ratios for the decay of the E{sub p} = 1058 keV resonance in {sup 14}N(p,gamma){sup 15}O have been redetermined. The data reported here should facilitate future studies of off-resonant capture in the {sup 14}N(p,gamma){sup 15}O reaction that are needed for an improved R-matrix extrapolation of the cross section. In addition, the data on the 430 keV resonance in {sup 15}N(p,alphagamma){sup 12}C may be useful for hydrogen depth profiling.

  10. The effect of FISH and CARD-FISH on the isotopic composition of (13)C- and (15)N-labeled Pseudomonas putida cells measured by nanoSIMS.

    PubMed

    Musat, Niculina; Stryhanyuk, Hryhoriy; Bombach, Petra; Adrian, Lorenz; Audinot, Jean-Nicolas; Richnow, Hans H

    2014-06-01

    The use of nanoSIMS for the exploration of microbial activities in natural habitats often implies that stable isotope tracer experiments are combined with in situ hybridization techniques (i.e. fluorescence in situ hybridization (FISH) or catalyzed reporter deposition (CARD)-FISH). In this study, Pseudomonas putida grown on (13)C- and (15)N-labeled carbon and nitrogen, collected in exponential growth and stationary phases, was hybridized and analyzed by nanoSIMS. It was shown that (13)C and (15)N fractions decreased after FISH and CARD-FISH in comparison to chemically untreated cells. However, the fractions were influenced differently by various treatments. After paraformaldehyde fixation of exponentially growing cells, a reduction of the (13)C and (15)N fractions was measured from 941.2% and 89.53.8% to 90.20.8% and 644.6%, respectively, indicating that nitrogen isotopic composition was most influenced. A further decrease of the (13)C and (15)N fractions to 80.76.5 and 59.54.1%, respectively, was measured after FISH, while CARD-FISH decreased the fractions to 57.43.0% and 47.14.1%, respectively. The analysis of cells collected in different growth phases revealed that the effect of various treatments seemed to be dependent on the cell's physiological state. In addition, a mathematical model that can be used in further studies was developed in order to calculate the amount of carbon introduced into the cells by chemical treatments. These results can be valuable for environmental FISH-nanoSIMS studies where the isotopic composition of single cells will be used to quantitatively assess the importance of specific populations to certain biochemical processes and determine budget estimations. PMID:24702905

  11. Heterotrophic 15N2 Fixation and Distribution of Newly Fixed Nitrogen in a Rice-Flooded Soil System 1

    PubMed Central

    Eskew, David L.; Eaglesham, Allan R. J.; App, A. A.

    1981-01-01

    Rice (Oryza sativa L.) plants growing in pots of flooded soil were exposed to a 15N2-enriched atmosphere for 3 to 13 days in a gas-tight chamber. The floodwater and soil surface were shaded with a black cloth to reduce the activity of phototrophic N2-fixing micro-organisms. The highest 15N enrichments were consistently observed in the roots, although the total quantity of 15N incorporated into the soil was much greater. The rate of 15N incorporation into roots was much higher at the heading than at the tillering stage of growth. Definite enrichments were also found in the basal node and in the lower outer leaf sheath fractions after 3 days of exposure at the heading stage. Thirteen days was the shortest time period in which definite 15N enrichment was observed in the leaves and panicle. When plants were exposed to 15N2 for 13 days just before heading and then allowed to mature in a normal atmosphere, 11.3% of the total 15N in the system was found in the panicles, 2.3% in the roots, and 80.7% in the subsurface soil. These results provide direct evidence of heterotrophic N2 fixation associated with rice roots and the flooded soil and demonstrate that part of the newly fixed N is available to the plant. PMID:16661887

  12. Discrimination against 15N among recombinant inbred lines of Phaseolus vulgaris L. contrasting in phosphorus use efficiency for nitrogen fixation.

    PubMed

    Lazali, Mohamed; Bargaz, Adnane; Carlsson, Georg; Ounane, Sidi Mohamed; Drevon, Jean Jacques

    2014-02-15

    Although isotopic discrimination processes during nitrogen (N) transformations influence the outcome of (15)N based quantification of N2 fixation in legumes, little attention has been given to the effects of genotypic variability and environmental constraints such as phosphorus (P) deficiency, on discrimination against (15)N during N2 fixation. In this study, six Phaseolus vulgaris recombinant inbred lines (RILs), i.e. RILs 115, 104, 34 (P deficiency tolerant) and 147, 83, 70 (P deficiency sensitive), were inoculated with Rhizobium tropici CIAT899, and hydroaeroponically grown with P-sufficient (250 ?mol P plant(-1) week(-1)) versus P-deficient (75 ?mol P plant(-1) week(-1)) supply. Two harvests were done at 15 (before nodule functioning) and 42 (flowering stage) days after transplanting. Nodulation, plant biomass, P and N contents, and the ratios of (15)N over total N content ((15)N/Nt) for shoots, roots and nodules were determined. The results showed lower (15)N/Nt in shoots than in roots, both being much lower than in nodules. P deficiency caused a larger decrease in (15)N/Nt in shoots (-0.18%) than in nodules (-0.11%) for all of the genotypes, and the decrease in shoots was greatest for RILs 34 (-0.33%) and 104 (-0.25%). Nodule (15)N/Nt was significantly related to both the quantity of N2 fixed (R(2)=0.96***) and the P content of nodules (R(2)=0.66*). We conclude that the discrimination against (15)N in the legume N2-fixing symbiosis of common bean with R. tropici CIAT899 is affected by P nutrition and plant genotype, and that the (15)N/Nt in nodules may be used to screen for genotypic variation in P use efficiency for N2 fixation. PMID:24035519

  13. Fast and high-resolution stereochemical analysis by nonuniform sampling and covariance processing of anisotropic natural abundance 2D 2H?NMR datasets.

    PubMed

    Lafon, Olivier; Hu, Bingwen; Amoureux, Jean-Paul; Lesot, Philippe

    2011-06-01

    Natural abundance deuterium (NAD) 2D NMR spectroscopy using chiral or achiral liquid crystals is an efficient analytical tool for the stereochemical analysis of enantio- or diastereomers by the virtue of proton-to-deuterium substitution. In particular, it allows the measurement of enantiopurity of organic synthetic molecules or the determination of the natural isotopic (1)H/(2)H fractionation in biological molecules, such as fatty acid methyl esters (FAME). So far, the NAD 2D spectra of solutes were acquired by using uniform sampling (US) and processed by conventional 2D Fourier transform (FT), which could result in long measurement times for medium-sized analytes or low solute concentrations. Herein, we demonstrate that this conventional approach can be advantageously replaced by nonuniform sampling (NUS) processed by covariance (Cov) transform. This original spectral reconstruction provides a significant enhancement of spectral resolution, as well as a reduction of measurement times. The application of Cov to NUS data has required the introduction of a regularization procedure in the time domain for the indirect dimension. The analytical potential of combining Cov and NUS is demonstrated by measuring the enantiomeric excess of a scalemic mixture of 2-ethyloxirane and by determining the diastereomeric excess of methyl vernoleate, a natural FAME. These two organic compounds were aligned in a polypeptide (poly(?-benzyl-L-glutamate)) mesophase. In the case of NAD 2D NMR spectroscopy, we show that Cov and NUS methods allow a decrease in measurement time by a factor of two compared with Cov applied to US data and a factor of four compared with FT applied to US data. PMID:21563219

  14. ?13C and ?15N in the ornithogenic sediments from the Antarctic maritime as palaeoecological proxies during the past 2000 yr

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Dong; Li, Hong-Chun; Sun, Li-Guang; Yin, Xue-Bin; Zhao, San-Ping; Wang, Yu-Hong

    2006-03-01

    In this paper, we have examined carbon and nitrogen isotopic compositions in two ornithogenic sediment profiles from the Ardley Island and Barton Peninsula of Antarctica for palaeoecological changes during the past 2000 yr. The ?13C values of the two sediment profiles range from - 22.26 to - 19.15 (PDB) in Core G and from - 24.01 to - 19.87 in profile A, showing that the predominant carbon source in the sediments plausibly comes from terrestrial and aquatic plants in Antarctic such as mosses, lichens, and algae in lakes. As these ?13C values are also close to those in the fresh lake sediments that are not influenced by penguin guano, one may not use the ?13C values as evidence for the influence of guano on the sediments. The ?15N values of the two profiles range from 4.75 to 18.34 (air) and from 5.17 to 10.38 for Core G and Core A, respectively. The ?15N variations have positive correlations with the trends of the bio-element contents in the sediments. As the levels of these bio-elements in ornithogenic sediments had been used to reconstruct the changes of historical penguin population and tundra vegetation abundance and diversity, we then suggest that the ?15N records can be utilized to study palaeoecological processes of penguin. Our results show that penguin population and activity has generally decreased over the past 2000 yr. From 1300 to 900 yr BP and from 1790 to 1860 AD, penguin population and activity experienced two strong decreases. It will be interesting to understand the cause of these decreases.

  15. Simulating the density of HC15N in the Titan atmosphere with a coupled ion-neutral photochemical model

    NASA Astrophysics Data System (ADS)

    Vuitton, V.; Yelle, R. V.; Klippenstein, S. J.; Lavvas, P.; Hrst, S. M.

    2015-10-01

    The 14 N/ 15 N ratio for HCN in the atmosphere of Titan has been measured to be 2 to 3 times as less as the corresponding ratio for N2. Using a coupled ionneutral photochemical model incorporating state-of-the-art chemistry and cross-sections for N2, we show that the difference in the ratio of 14 N/15 N between HCN and N2 can be explained exclusively by the photo-induced isotopic fractionation of 14 N14 N and 14 N 15 N,without any further putative nitrogen input.

  16. 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 (δ 13C \\-12.6 ‰ ) from maize fed cows was applied to a temperate grassland surface (δ 13C \\-29.95 ‰ ) at IGER-North Wyke (Devon, UK), and dung remains and soil cores beneath the treatments collected at ŧ = 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 Δ 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 δ 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 δ 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 δ 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

  17. Spatial variations in ?13C and ?15N values of primary consumers in a coastal lagoon

    NASA Astrophysics Data System (ADS)

    Como, S.; Magni, P.; Van Der Velde, G.; Blok, F. S.; Van De Steeg, M. F. M.

    2012-12-01

    The analysis of the contribution of a food source to a consumer's diet or the trophic position of a consumer is highly sensitive to the variability of the isotopic values used as input data. However, little is known in coastal lagoons about the spatial variations in the isotopic values of primary consumers considered 'end members' in the isotope mixing models for quantifying the diet of secondary consumers or as a baseline for estimating the trophic position of consumers higher up in the food web. We studied the spatial variations in the ?13C and ?15N values of primary consumers and sedimentary organic matter (SOM) within a selected area of the Cabras lagoon (Sardinia, Italy). Our aim was to assess how much of the spatial variation in isotopic values of primary consumers was due to the spatial variability between sites and how much was due to differences in short distances from the shore. Samples were collected at four stations (50-100 m apart) selected randomly at two sites (1.5-2 km apart) chosen randomly at two distances from the shore (i.e. in proximity of the shore -Nearshore - and about 200 m away from the shore -Offshore). The sampling was repeated in March, May and August 2006 using new sites at the two chosen distances from the shore on each date. The isotopic values of size-fractionated seston and macrophytes were also analyzed as a complementary characterization of the study area. While ?15N did not show any spatial variations, the ?13C values of deposit feeders, Alitta (=Neanthes) succinea, Lekanesphaera hookeri, Hydrobia acuta and Gammarus aequicauda, were more depleted Offshore than Nearshore. For these species, there were significant effects of distance or distance dates in the mean ?13C values, irrespective of the intrinsic variation between sites. SOM showed similar spatial variations in ?13C values, with Nearshore-Offshore differences up to 6. This indicates that the spatial isotopic changes are transferred from the food sources to the deposit feeders studied. In contrast, ?13C and ?15N values of suspension feeders, Ficopomatus enigmaticus and Amphibalanus amphitrite, did not show major variations, either between sites, or between Nearshore and Offshore. These different patterns between deposit feeders and suspension feeders are probably due to a weaker trophic link of the latter with SOM. We suggest that the Nearshore-Offshore gradient might be an important source of isotopic variation that needs to be considered in future web studies in coastal lagoons.

  18. Nitrous oxide nitrification and denitrification 15N enrichment factors from Amazon forest soils.

    PubMed

    Prez, Tibisay; Garcia-Montiel, Diana; Trumbore, Susan; Tyler, Stanley; de Camargo, Plnio; Moreira, Marcelo; Piccolo, Marisa; Cerri, Carlos

    2006-12-01

    The isotopic signatures of 15N and 18O in N2O emitted from tropical soils vary both spatially and temporally, leading to large uncertainty in the overall tropical source signature and thereby limiting the utility of isotopes in constraining the global N2O budget. Determining the reasons for spatial and temporal variations in isotope signatures requires that we know the isotope enrichment factors for nitrification and denitrification, the two processes that produce N2O in soils. We have devised a method for measuring these enrichment factors using soil incubation experiments and report results from this method for three rain forest soils collected in the Brazilian Amazon: soil with differing sand and clay content from the Tapajos National Forest (TNF) near Santarm, Par, and Nova Vida Farm, Rondnia. The 15N enrichment factors for nitrification and denitrification differ with soil texture and site: -111 per thousand +/- 12 per thousand and -31 per thousand +/- 11 per thousand for a clay-rich Oxisol (TNF), -102 per thousand +/- 5 per thousand and -45 per thousand +/- 5 per thousand for a sandier Ultisol (TNF), and -10.4 per thousand +/- 3.5 per thousand (enrichment factor for denitrification) for another Ultisol (Nova Vida) soil, respectively. We also show that the isotopomer site preference (delta15Nalpha - delta15Nbeta, where alpha indicates the central nitrogen atom and beta the terminal nitrogen atom in N2O) may allow differentiation between processes of production and consumption of N2O and can potentially be used to determine the contributions of nitrification and denitrification. The site preferences for nitrification and denitrification from the TNF-Ultisol incubated soils are: 4.2 per thousand +/- 8.4 per thousand and 31.6 per thousand +/- 8.1 per thousand, respectively. Thus, nitrifying and denitrifying bacteria populations under the conditions of our study exhibit significantly different 15N site preference fingerprints. Our data set strongly suggests that N2O isotopomers can be used in concert with traditional N2O stable isotope measurements as constraints to differentiate microbial N2O processes in soil and will contribute to interpretations of the isotopic site preference N2O values found in the free troposphere. PMID:17205894

  19. The Contamination of Commercial 15N2 Gas Stocks with 15N–Labeled Nitrate and Ammonium and Consequences for Nitrogen Fixation Measurements

    PubMed Central

    Dabundo, Richard; Lehmann, Moritz F.; Treibergs, Lija; Tobias, Craig R.; Altabet, Mark A.; Moisander, Pia H.; Granger, Julie

    2014-01-01

    We report on the contamination of commercial 15-nitrogen (15N) N2 gas stocks with 15N-enriched ammonium, nitrate and/or nitrite, and nitrous oxide. 15N2 gas is used to estimate N2 fixation rates from incubations of environmental samples by monitoring the incorporation of isotopically labeled 15N2 into organic matter. However, the microbial assimilation of bioavailable 15N-labeled N2 gas contaminants, nitrate, nitrite, and ammonium, is liable to lead to the inflation or false detection of N2 fixation rates. 15N2 gas procured from three major suppliers was analyzed for the presence of these 15N-contaminants. Substantial concentrations of 15N-contaminants were detected in four Sigma-Aldrich 15N2 lecture bottles from two discrete batch syntheses. Per mole of 15N2 gas, 34 to 1900 µmoles of 15N-ammonium, 1.8 to 420 µmoles of 15N-nitrate/nitrite, and ≥21 µmoles of 15N-nitrous oxide were detected. One 15N2 lecture bottle from Campro Scientific contained ≥11 µmoles of 15N-nitrous oxide per mole of 15N2 gas, and no detected 15N-nitrate/nitrite at the given experimental 15N2 tracer dilutions. Two Cambridge Isotopes lecture bottles from discrete batch syntheses contained ≥0.81 µmoles 15N-nitrous oxide per mole 15N2, and trace concentrations of 15N-ammonium and 15N-nitrate/nitrite. 15N2 gas equilibrated cultures of the green algae Dunaliella tertiolecta confirmed that the 15N-contaminants are assimilable. A finite-differencing model parameterized using oceanic field conditions typical of N2 fixation assays suggests that the degree of detected 15N-ammonium contamination could yield inferred N2 fixation rates ranging from undetectable, <0.01 nmoles N L−1 d−1, to 530 nmoles N L−1 d−1, contingent on experimental conditions. These rates are comparable to, or greater than, N2 fixation rates commonly detected in field assays. These results indicate that past reports of N2 fixation should be interpreted with caution, and demonstrate that the purity of commercial 15N2 gas must be ensured prior to use in future N2 fixation rate determinations. PMID:25329300

  20. Nuclear magnetic resonance studies on huwentoxin-XI from the Chinese bird spider Ornithoctonus huwena: 15N labeling and sequence-specific 1H, 15N nuclear magnetic resonance assignments.

    PubMed

    Peng, Kuan; Lin, Ying; Liang, Song-Ping

    2006-07-01

    Huwentoxin-XI purified from the Chinese bird spider Ornithoctonus huwena is a toxin with both antiprotease activity and potassium channel blocking activity. To determine its solution structure, huwentoxin-XI was expressed in a yeast eukaryotic expression system and studied by NMR. The 15N labeling strategy was used to facilitate the process of resonance assignments. The nearly complete sequence-specific assignments of proton and nitrogen resonances were obtained by analyzing a series of two-dimensional (2D) and three-dimensional (3D) spectra, including DQF-COSY, TOCSY, NOESY, 15N-1H HSQC, 15N-1H HNHA, 15N-1H HNHB, 15N-1H TOCSY-HSQC and 15N-1H NOESY-HSQC spectra. Secondary structure analysis of huwentoxin-XI showed that it mainly contains an N-terminal 310-helix from Thr3 to Arg5 and a C-terminal alpha-helix from Gln45 to Cys52, plus a triple-stranded antiparallel beta-sheet of Glu18-Asn23, Thr26-Ile31 and Asn40-Lys41. These studies provide a solid basis for the final structure determination of huwentoxin-XI. PMID:16820861

  1. Experimental and calculated 1H, 13C, 15N NMR spectra of famotidine

    NASA Astrophysics Data System (ADS)

    Barańska, M.; Czarniecki, K.; Proniewicz, L. M.

    2001-05-01

    Famotidine, 3-[[[2-[(aminoiminomethyl)amino]-4-thiazolyl]methyl]thio]- N-(aminosulfonyl), is a histamine H 2-receptor blocker that has been used mainly for the treatment of peptic ulcers and the Zollinger-Ellison syndrome. Its NMR spectra in different solvents were reported earlier; however, detailed interpretation has not been done thus far. In this work, experimental 1H, 13C and 15N NMR spectra of famotidine dissolved in DMSO-d 6 are shown. The assignment of observed chemical shifts is based on quantum chemical calculation at the Hartree-Fock/6-31G ∗ level. The geometry optimization of the famotidine molecule with two internal hydrogen bonds, i.e. [N(3)-H(23)⋯N(9) and N(3)⋯H(34)-N(20)], is done by using the B3LYP method with the 6-31G ∗ basis set.

  2. /sup 15/N and /sup 13/C NMR determination of methionine metabolism in developing soybean cotyledons

    SciTech Connect

    Coker, G.T. III; Garbow, J.R.; Schaefer, J.

    1987-03-01

    The metabolism of D- and L-methionine by immature cotyledons of soybean (Glycine max, L. cv Elf) grown in culture has been investigated using solid-state /sup 13/C and /sup 15/N nuclear magnetic resonance. D-Methionine is taken up by the cotyledons and converted to an amide, most likely by N-malonylation. About 16% of the L-methionine taken up is incorporated intact into protein, and 25% remains as soluble methionine. Almost two-thirds of the L-methionine that enters the cotyledons is degraded. The largest percentage of this is used in transmethylation of the carboxyl groups of pectin. Methionine is not extensively converted to polyamines. The authors attribute the stimulation of growth of the cotyledons by exogenous methionine to the bypassing of a rate-limiting methyl-transfer step in the synthesis of methionine itself, and subsequently of pectins and proteins.

  3. 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 δ15N values varying from 271.6‰ to 1354.2‰ at the end of the experiment. Enrichment of roots was significantly higher than leaves (δ13C range: 111.5-219.2‰; δ15N 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.

  4. 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 & Bzard 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.

  5. sup 15 N and sup 1 H NMR studies of Rhodospirillum rubrum cytochrome c sub 2

    SciTech Connect

    Yu, Liping.

    1989-01-01

    Rhodospirillum rubrum cytochrome c{sub 2} in both oxidation states has been studied by {sup 15}N and {sup 1}H NMR spectroscopy. Significant {sup 15}N and {sup 1}H NMR resonances of the cytochrome c{sub 2} have been assigned. The exchange rates of the nitrogen-bonded protons are found to vary greatly. The ligand His {pi}NH in the reduced state has an exchange rate {approximately}350 times slower than that in the oxidized state, indicating significant changes in the interior hydrophobicity between the two oxidation states. The ligand His is found not to ionize in the neutral pH range. The ionizations of the nonliganded His 42 with an assigned pKa of {approximately}7.0 in the reduced state and an assigned pKa of 6.2 in the oxidized state cause the resonances of a wide range of groups to shift with pH, perhaps by altering the packing of the {Omega} loops which cover that region of the protein. The oxidized protein has been found to have conformational heterogeneity and experiences gross structural changes with a pKa of 9.2, which is due to the displacement of the ligand methionine at high pH. The N-terminus of the protein has a similar pKa of {approximately}8.5 in both oxidation states. However, the mobility of the N-terminus is different, being restricted in the reduced state and very mobile in the oxidized state. The reduced protein is found to be very stable in the pH range between 4.9 and 10.0, but unfolds abruptly at pH above 11.0. The imidazole of His 42 undergoes fast proton exchange in the denatured form in contrast to the tautomerization at an intermediate rate in the native form. The mechanisms underlying the protein denaturation and renaturation are discussed.

  6. 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.

  7. Electron spin resonance spectroscopy studies on 15N-labeled and their deuterated nitroxyl spin probes used in molecular imaging

    NASA Astrophysics Data System (ADS)

    Jebaraj, D. David; Benial, A. Milton Franklin; Ichikawa, Kazuhiro; Yamada, Kenichi; Utsumi, Hideo

    2013-06-01

    Electron Spin Resonance (ESR) studies were carried out for 2 mM concentration of 15N labeled carbamoyl-PROXYL, carboxy-PROXYL, MC-PROXYL and their deuterated derivatives using X-band ESR spectrometer. The ESR parameters such as linewidth, hyperfine coupling constant, g-factor, spin-spin relaxation time were determined. The lineshape analysis was also carried out. The observed linewidth values are 50% higher for undeuterated nitroxyl radicals compared with their deuterated derivatives. The lineshape analysis reveals that the observed ESR lineshape is a voigt lineshape, which is the convolution of a lorentzian and guassian profile. ESR lineshape analysis results that the lorentzian contribution is 20% higher for deuterated nitroxyl radicals compared with undeuterated nitroxyl radicals. The observed spin-spin relaxartion time for deuterated nitroxyl radicals is 50% longer compared with undeuterated nitroxyl radicals. The g value indicates the isotropic nature of nitroxyl radicals in pure water. From these results, the deuterated nitroxyl radicals are suitable spin probes for ESR/Overhauser-enhanced magnetic resonance (OMR) studies.

  8. A suite of Mathematica notebooks for the analysis of protein main chain 15N NMR relaxation data.

    PubMed

    Spyracopoulos, Leo

    2006-12-01

    A suite of Mathematica notebooks has been designed to ease the analysis of protein main chain 15N NMR relaxation data collected at a single magnetic field strength. Individual notebooks were developed to perform the following tasks: nonlinear fitting of 15N-T1 and -T2 relaxation decays to a two parameter exponential decay, calculation of the principal components of the inertia tensor from protein structural coordinates, nonlinear optimization of the principal components and orientation of the axially symmetric rotational diffusion tensor, model-free analysis of 15N-T1, -T2, and {1H}-15N NOE data, and reduced spectral density analysis of the relaxation data. The principle features of the notebooks include use of a minimal number of input files, integrated notebook data management, ease of use, cross-platform compatibility, automatic visualization of results and generation of high-quality graphics, and output of analyses in text format. PMID:17061025

  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. Comparison of five soil organic matter decomposition models using data from a 14C and 15N labeling field experiment

    NASA Astrophysics Data System (ADS)

    Pansu, Marc; Bottner, Pierre; Sarmiento, Lina; Metselaar, Klaas

    2004-12-01

    Five alternatives of the previously published MOMOS model (MOMOS-2 to -6) are tested to predict the dynamics of carbon (C) and nitrogen (N) in soil during the decomposition of plant necromass. 14C and 15N labeled wheat straw was incubated over 2 years in fallow soils of the high Andean Paramo of Venezuela. The following data were collected: soil moisture, total 14C and 15N and microbial biomass (MB)-14C and -15N, daily rainfall, air temperature and total radiation. Daily soil moisture was predicted using the SAHEL model. MOMOS-2 to -4 (type 1 models) use kinetic constants and flow partitioning parameters. MOMOS-2 can be simplified to MOMOS-3 and further to MOMOS-4, with no significant changes in the prediction accuracy and robustness for total-14C and -15N as well as for MB-14C and -15N. MOMOS-5 (type 2 models) uses only kinetic constants: three MB-inputs (from labile and stable plant material and from humified compounds) and two MB-outputs (mortality and respiration constants). MOMOS-5 did not significantly change the total-14C and -15N predictions but markedly improved the predictive quality and robustness of MB-14C and -15N predictions (with a dynamic different from the predictions by other models). Thus MOMOS-5 is proposed as an accurate and ecologically consistent description of decomposition processes. MOMOS-6 extends MOMOS-5 by including a stable humus compartment for long-term simulations of soil native C and N. The improvement of the predictions is not significant for this 2-year experiment, but MOMOS-6 enables prediction of a sequestration in the stable humus compartment of 2% of the initially added 14C and 5.4% of the added 15N.

  11. Species specific and environment induced variation of δ13C and δ15N 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 δ13C and δ15N 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 δ13C and δ15N varied among species by about 3–4‰ and 7–8‰ respectively. However, there was no overall difference in means of δ13C and δ15N for species sampled in different plant communities or when bulk plant dry matter harvests of different plant communities were compared. δ13C was found to be highly species specific, so that the ranking among species was mostly maintained across 11 habitats. However, δ15N 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 δ15N of non-legumes, which were either collected next to or away from the most common legume, T. alpinum. δ15N data place Cyperaceae and Juncaceae, just like Fabaceae, in a low discrimination category, well separated from other families. Soil δ15N 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 δ13C and δ15N signals in the studied high elevation plants is largely species specific (genetic) and insensitive to obvious environmental cues. PMID:26097487

  12. Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes

    NASA Astrophysics Data System (ADS)

    Wan, Chuan; Hu, Mary Y.; Borodin, Oleg; Qian, Jiangfeng; Qin, Zhaohai; Zhang, Ji-Guang; Hu, Jian Zhi

    2016-03-01

    Natural abundance 17O and 6Li NMR experiments, quantum chemistry and molecular dynamics studies were employed to investigate the solvation structures of Li+ at various concentrations of LiFSI in DME electrolytes. It was found that the chemical shifts of both 17O and 6Li changed with the concentration of LiFSI, indicating the changes of solvation structures with concentration. For the quantum chemistry calculations, the coordinated cluster LiFSI(DME)2 forms at first, and its relative ratio increases with increasing LiFSI concentration to 1 M. Then the solvation structure LiFSI(DME) become the dominant component. As a result, the coordination of forming contact ion pairs between Li+ and FSI- ion increases, but the association between Li+ and DME molecule decreases. Furthermore, at LiFSI concentration of 4 M the solvation structures associated with Li+(FSI-)2(DME), Li+2(FSI-)(DME)4 and (LiFSI)2(DME)3 become the dominant components. For the molecular dynamics simulation, with increasing concentration, the association between DME and Li+ decreases, and the coordinated number of FSI- increases, which is in perfect accord with the DFT results.

  13. Expression and purification of 15N- and 13C-isotope labeled 40-residue human Alzheimers ?-amyloid peptide for NMR-based structural analysis

    PubMed Central

    Long, Fei; Cho, Wonhwa; Ishii, Yoshitaka

    2011-01-01

    Amyloid fibrils of Alzheimers ?-amyloid peptide (A?) are a primary component of amyloid plaques, a hallmark of Alzheimers disease (AD). Enormous attention has been given to the structural features and functions of A? in amyloid fibrils and other type of aggregates in associated with development of AD. This report describes an efficient protocol to express and purify high-quality 40-residue A?(140), the most abundant A? in brains, for structural studies by NMR spectroscopy. Over-expression of A?(140) with glutathione S-transferase (GST) tag connected by a Factor Xa recognition site (IEGR?) in E. Coli resulted in the formation of insoluble inclusion bodies even with the soluble GST tag. This problem was resolved by efficient recovery of the GST-A? fusion protein from the inclusion bodies using 0.5% (w/v) sodium lauroyl sarcosinate as solubilizing agent and subsequent purification by affinity chromatography using a glutathione agarose column. The removal of the GST tag by Factor Xa enzymatic cleavage and purification by HPLC yielded as much as ~7 mg and ~1.5 mg of unlabeled A?(140) and uniformly 15N- and/or 13C-protein A?(140) from 1 L of the cell culture, respectively. Mass spectroscopy of unlabeled and labeled A? and 1H/15N HSQC solution NMR spectrum of the obtained 15N-labeled A? in the monomeric form confirmed the expression of native A?(140). It was also confirmed by electron micrography and solid-state NMR analysis that the purified A?(140) self-assembles into ?-sheet rich amyloid fibrils. To the best of our knowledge, our protocol offers the highest yields among published protocols for production of recombinant A?(140) samples that are amendable for an NMR-based structural analysis. The protocol may be applied to efficient preparation of other amyloid-forming proteins and peptides that are 13C- and 15N-labeled for NMR experiments. PMID:21640828

  14. Expression and purification of 15N- and 13C-isotope labeled 40-residue human Alzheimer's ?-amyloid peptide for NMR-based structural analysis.

    PubMed

    Long, Fei; Cho, Wonhwa; Ishii, Yoshitaka

    2011-09-01

    Amyloid fibrils of Alzheimer's ?-amyloid peptide (A?) are a primary component of amyloid plaques, a hallmark of Alzheimer's disease (AD). Enormous attention has been given to the structural features and functions of A? in amyloid fibrils and other type of aggregates in associated with development of AD. This report describes an efficient protocol to express and purify high-quality 40-residue A?(1-40), the most abundant A? in brains, for structural studies by NMR spectroscopy. Over-expression of A?(1-40) with glutathione S-transferase (GST) tag connected by a Factor Xa recognition site (IEGR(?)) in Escherichia coli resulted in the formation of insoluble inclusion bodies even with the soluble GST tag. This problem was resolved by efficient recovery of the GST-A? fusion protein from the inclusion bodies using 0.5% (w/v) sodium lauroyl sarcosinate as solubilizing agent and subsequent purification by affinity chromatography using a glutathione agarose column. The removal of the GST tag by Factor Xa enzymatic cleavage and purification by HPLC yielded as much as ?7 mg and ?1.5mg of unlabeled A?(1-40) and uniformly (15)N- and/or (13)C-protein A?(1-40) from 1L of the cell culture, respectively. Mass spectroscopy of unlabeled and labeled A? and (1)H/(15)N HSQC solution NMR spectrum of the obtained (15)N-labeled A? in the monomeric form confirmed the expression of native A?(1-40). It was also confirmed by electron micrography and solid-state NMR analysis that the purified A?(1-40) self-assembles into ?-sheet rich amyloid fibrils. To the best of our knowledge, our protocol offers the highest yields among published protocols for production of recombinant A?(1-40) samples that are amendable for an NMR-based structural analysis. The protocol may be applied to efficient preparation of other amyloid-forming proteins and peptides that are (13)C- and (15)N-labeled for NMR experiments. PMID:21640828

  15. Sub-cellular localisation of a 15N-labelled peptide vector using NanoSIMS imaging

    NASA Astrophysics Data System (ADS)

    Rmer, Winfried; Wu, Ting-Di; Duchambon, Patricia; Amessou, Mohamed; Carrez, Danile; Johannes, Ludger; Guerquin-Kern, Jean-Luc

    2006-07-01

    Dynamic SIMS imaging is proposed to map sub-cellular distributions of isotopically labelled, exogenous compounds. NanoSIMS imaging allows the characterisation of the intracellular transport pathways of exogenous molecules, including peptide vectors employed in innovative therapies, using stable isotopes as molecular markers to detect the compound of interest. Shiga toxin B-subunit (STxB) was chosen as a representative peptide vector. The recombinant protein ( 15N-STxB) was synthesised in Escherichia coli using 15NH 4Cl as sole nitrogen source resulting in 15N enrichment in the molecule. Using the NanoSIMS 50 ion microprobe (Cameca), different ion species ( 12C 14N -, 12C 15N -, 31P -) originating from the same sputtered micro volume were simultaneously detected. High mass resolving power enabled the discrimination of 12C 15N - from its polyatomic isobars of mass 27. We imaged the membrane binding and internalisation of 15N-STxB in HeLa cells at spatial resolutions of less than 100 nm. Thus, the use of rare stable isotopes like 15N with dynamic SIMS imaging permits sub-cellular detection of isotopically labelled, exogenous molecules and imaging of their transport pathways at high mass and spatial resolution. Application of stable isotopes as markers can replace the large and chemically complex tags used for fluorescence microscopy, without altering the chemical and physical properties of the molecule.

  16. Investigating patterns of symbiotic nitrogen fixation during vegetation change from grassland to woodland using fine scale ?(15) N measurements.

    PubMed

    Soper, Fiona M; Boutton, Thomas W; Sparks, Jed P

    2015-01-01

    Biological nitrogen fixation (BNF) in woody plants is often investigated using foliar measurements of ?(15) N and is of particular interest in ecosystems experiencing increases in BNF due to woody plant encroachment. We sampled ?(15) N along the entire N uptake pathway including soil solution, xylem sap and foliage to (1) test assumptions inherent to the use of foliar ?(15) N as a proxy for BNF; (2) determine whether seasonal divergences occur between ?(15) Nxylem sap and ?(15) Nsoil inorganic N that could be used to infer variation in BNF; and (3) assess patterns of ?(15) N with tree age as indicators of shifting BNF or N cycling. Measurements of woody N-fixing Prosopis glandulosa and paired reference non-fixing Zanthoxylum fagara at three seasonal time points showed that ?(15) Nsoil inorganic N varied temporally and spatially between species. Fractionation between xylem and foliar ?(15) N was consistently opposite in direction between species and varied on average by 2.4. Accounting for these sources of variation caused percent nitrogen derived from fixation values for Prosopis to vary by up to ?70%. Soil-xylem ?(15) N separation varied temporally and increased with Prosopis age, suggesting seasonal variation in N cycling and BNF and potential long-term increases in BNF not apparent through foliar sampling alone. PMID:24890575

  17. Using dual-bacterial denitrification to improve δ15N 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.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  20. 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

  1. 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).

  2. Spatial and Temporal Variations in Stable Carbon (?13C) and Nitrogen (?15N) Isotopic Composition of Symbiotic Scleractinian Corals

    PubMed Central

    Nahon, Sarah; Richoux, Nicole B.; Kolasinski, Joanna; Desmalades, Martin; Ferrier Pages, Christine; Lecellier, Gael; Planes, Serge; Berteaux Lecellier, Vronique

    2013-01-01

    Tropical scleractinian corals are considered autotrophic as they rely mainly on photosynthesis-derived nutrients transferred from their photosymbionts. Corals are also able to capture and ingest suspended particulate organic matter, so heterotrophy can be an important supplementary trophic pathway to optimize coral fitness. The aim of this in situ study was to elucidate the trophic status of 10 coral species under contrasted environmental conditions in a French Polynesian lagoon. Carbon (?13C) and nitrogen (?15N) isotopic compositions of coral host tissues and photosymbionts were determined at 3 different fringing reefs during wet and dry seasons. Our results highlighted spatial variability in stable isotopic compositions of both coral host tissues and photosymbionts. Samples from the site with higher level of suspended particulate matter were 13C-depleted and 15N-enriched relative to corals and photosymbionts from less turbid sites. However, differences in both ?13C and ?15N between coral host tissues and their photosymbionts (?host-photosymbionts 13C and ?host-photosymbionts 15N) were small (0.27 0.76 and 1.40 0.90, respectively) and similar at all sites, thus indicating no general increases in the heterotrophic pathway. Depleted ?13C and enriched ?15N values of coral host tissues measured at the most turbid site were explained by changes in isotopic composition of the inorganic nutrients taken up by photosymbionts and also by changes in rate of isotopic fractionation with environmental conditions. Our results also highlighted a lack of significant temporal variations in ?13C and ?15N values of coral host and photosymbiont tissues and in ?host-photosymbionts 13C and ?host-photosymbionts 15N values. This temporal stability indicated that corals remained principally autotrophic even during the wet season when photosymbiont densities were lower and the concentrations of phytoplankton were higher. Increased coral heterotrophy with higher food availability thus appears to be species-specific. PMID:24312542

  3. 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.; Lscher, 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