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Sample records for 15n labelled litter

  1. Tracking the incorporation of 15N from labeled beech litter into mineral-organic associations

    NASA Astrophysics Data System (ADS)

    Kleber, M.; Hatton, P.; Derrien, D.; Lajtha, K.; Zeller, B.

    2008-12-01

    Nitrogen containing organic compounds are thought to have a role in the complex web of processes that control the turnover time of soil organic matter. The sequential density fractionation technique is increasingly used for the purpose of investigating the association of organic materials with the mineral matrix. Organic materials in the denser fractions (>2.0 kg L-1) typically show 13C NMR signals indicative of carbohydrate and aliphatic structures, an absence of lignin and tannin structures and a narrow C:N ratio, suggesting a microbial origin of organic matter in these fractions. Here we take advantage of a labeling experiment conducted at two different sites in Germany and in France to investigate the incorporation of organic nitrogen into physical fractions of increasing density, representing a proximity gradient to mineral surfaces. 15N labeled beech litter was applied to two acidic forest topsoils 8 and 12 years ago. Although there are differences in the distribution patterns between the two soils, and the majority of the organic nitrogen was recovered in fractions representing organic matter of plant origin and not bound to the mineral matrix, our data clearly show that after a decade, significant amounts of the nitrogen had been incorporated in mineral-organic fractions of supposedly slow turnover. It remains to be shown to which extent the N in the densest fractions was incorporated by soil microbiota and associated with mineral surfaces in organic form or adsorbed to mineral surfaces in inorganic form (NH4+).

  2. Decomposition and nitrogen dynamics of 15N-labeled leaf, root, and twig litter in temperate coniferous forests

    USGS Publications Warehouse

    van Huysen, Tiff L.; Harmon, Mark E.; Perakis, Steven S.; Chen, Hua

    2013-01-01

    Litter nutrient dynamics contribute significantly to biogeochemical cycling in forest ecosystems. We examined how site environment and initial substrate quality influence decomposition and nitrogen (N) dynamics of multiple litter types. A 2.5-year decomposition study was installed in the Oregon Coast Range and West Cascades using 15N-labeled litter from Acer macrophyllum, Picea sitchensis, and Pseudotsuga menziesii. Mass loss for leaf litter was similar between the two sites, while root and twig litter exhibited greater mass loss in the Coast Range. Mass loss was greatest from leaves and roots, and species differences in mass loss were more prominent in the Coast Range. All litter types and species mineralized N early in the decomposition process; only A. macrophyllum leaves exhibited a net N immobilization phase. There were no site differences with respect to litter N dynamics despite differences in site N availability, and litter N mineralization patterns were species-specific. For multiple litter × species combinations, the difference between gross and net N mineralization was significant, and gross mineralization was 7–20 % greater than net mineralization. The mineralization results suggest that initial litter chemistry may be an important driver of litter N dynamics. Our study demonstrates that greater amounts of N are cycling through these systems than may be quantified by only measuring net mineralization and challenges current leaf-based biogeochemical theory regarding patterns of N immobilization and mineralization.

  3. Millipedes and earthworms increase the decomposition rate of 15N-labelled winter rape litter in an arable field.

    PubMed

    Martens, H; Alphei, J; Schaefer, M; Scheu, S

    2001-01-01

    Effects of millipedes and earthworms on the decomposition of 15N-labelled litter of winter oilseed rape were investigated in a microcosm field experiment over a period of 264 days on an oat field near Göttingen managed by integrated farming. A total of 32 microcosms were filled with defaunated soil. 15N-labelled rape litter was placed either on top of the soil or buried into the soil simulating mulching and ploughing, respectively. To the microcosms nine adult individuals of Blaniulus guttulatus (Diplopoda) and two of Aporrectodea caliginosa (Lumbricidae) were added separately or in combination. In general, the presence of the animals accelerated the decomposition rate of the litter material. The effects were most pronounced in the presence of Aporrectodea caliginosa. The total amount of nitrate, ammonium and the amount of 35N leached from the microcosms was increased in the presence of earthworms or of both earthworms and millipedes. Both species proved to be important members of the detritus food web of the agricultural system studied.

  4. Fungal Functioning In A Pine Forest: Evidence From A 15N-Labeled Global Change Experiment

    NASA Astrophysics Data System (ADS)

    Hobbie, E. A.; Hofmockel, K.; van Diepen, L.

    2012-12-01

    In this study, we used tracer 15N labeling and a concurrent six-year nitrogen fertilization experiment in a Pinus taeda Free Air CO2 Enrichment (FACE) experiment to investigate the functioning of saprotrophic and ectomycorrhizal fungi in nitrogen cycling. Ectomycorrhizal fungi with hydrophobic ectomycorrhizae acquired nitrogen from deeper in the soil profile than taxa with hydrophilic ectomycorrhizae, whereas saprotrophic fungi acquired nitrogen primarily from relatively recent surface litter. By combining natural abundance and tracer measurements, we estimated the 15N enrichment of fungi relative to source nitrogen at between 4‰ and 9‰, depending on genus, with some genera sampling pools more 15N-enriched in the labeling experiment than could be measured by bulk analyses. Thus, biologically relevant nitrogen fractions may correspond poorly to what can be extracted chemically. The multiple 15N labels in this FACE experiment proved useful for tracking nitrogen into different fungal taxa from potential nitrogen sources.

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

    NASA Astrophysics Data System (ADS)

    Fustec, Joëlle; Mahieu, Stéphanie

    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

  6. 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

  7. Fate of nitrogen deposition and decomposed nitrogen from litter in a 15N-tracer mesocosm experiment

    NASA Astrophysics Data System (ADS)

    Nair, R.; Perks, M.; Mencuccini, M.

    2013-12-01

    Atmospheric deposition of anthropogenic-derived nitrogen may be a major driver of the 0.6-0.7 Pg y-1 increase in the carbon sink in historically N-limited northern and boreal forests, but the magnitude of its effect is still uncertain. A strong effect depends on the allocation of N to trees, because of their high C:N ratio in woody tissues, and isotope tracer experiments have shown that the majority of 15N tracers applied directly to the soil are lost via leeching or retained in soil pools rather than being acquired by tree root systems. However, ambient anthropogenic inputs of N to these systems are transported in the atmosphere and intercepted by foliage before they reach the soil system, while labelled fertilization experiments also can only explicitly trace the fate of the 15N-tracer from deposition, as opposed to changes in the fate of N from litter, where decomposition rates may be enhanced at low ambient levels of deposition, affecting the availability of N from this pool for tree nutrition. We present initial results from a potted Sitka Spruce mesocosm 15N-tracer experiment where ambient nitrogen deposition was supplemented with a minor (0.4 kg ha-1 y-1) input of additional N, applied to either the soil or the foliage. Either this deposition, or litter in the pots, was enriched in 15N, allowing the fate of the isotope from two different methods of deposition to be compared with that of nitrogen released from the litter under the deposition treatment.

  8. Differential growth of the fungus Absidia cylindrospora on 13C/15N-labelled media.

    PubMed

    Crotty, F V; Blackshaw, R P; Murray, P J

    2011-06-15

    Many studies utilise enrichment of stable isotopes as tracers to follow the interactions occurring within soil food webs and methods have been developed to enrich bacteria, soil fauna and plant litter, Here for the first time we attempt to enrich a soil fungus to 99 atom% with (13)C and (15)N stable isotopes. In this study our objectives were to (a) assess whether the saprotrophic zygomycete fungus Absidia cylindrospora could grow on a medium enriched to 99 atom% with (13)C-glucose and (15)N-ammonium chloride, (b) to determine the level of enrichment obtained, and (c) to examine the change in growth rate of this fungus while it was growing on the dually enriched medium. To achieve this, the fungus was grown on agar enriched with (13)C and (15)N to 99 atom% and its growth rate monitored. The results showed that A. cylindrospora would grow on the highly labelled growth medium, but that its rate of growth was affected compared with the rate on either natural abundance media or media highly enriched with a single isotope ((13)C or (15)N). The implications of these results is that although the fungus is able to utilise these heavier isotopes, the biochemical processes involved in growth are affected, and consideration should be given to these differences when using stable isotope tracers in, for example, soil food web studies.

  9. Early-stage changes in natural (13)C and (15)N abundance and nutrient dynamics during different litter decomposition.

    PubMed

    Gautam, Mukesh Kumar; Lee, Kwang-Sik; Song, Byeong-Yeol; Lee, Dongho; Bong, Yeon-Sik

    2016-05-01

    Decomposition, nutrient, and isotopic (δ(13)C and δ(15)N) dynamics during 1 year were studied for leaf and twig litters of Pinus densiflora, Castanea crenata, Erigeron annuus, and Miscanthus sinensis growing on a highly weathered soil with constrained nutrient supply using litterbags in a cool temperate region of South Korea. Decay constant (k/year) ranged from 0.58 to 1.29/year, and mass loss ranged from 22.36 to 58.43 % among litter types. The results demonstrate that mass loss and nutrient dynamics of decomposing litter were influenced by the seasonality of mineralization and immobilization processes. In general, most nutrients exhibited alternate phases of rapid mineralization followed by gradual immobilization, except K, which was released throughout the field incubation. At the end of study, among all the nutrients only N and P showed net immobilization. Mobility of different nutrients from decomposing litter as the percentage of initial litter nutrient concentration was in the order of K > Mg > Ca > N ≈ P. The δ(13)C (0.32-6.70 ‰) and δ(15)N (0.74-3.90 ‰) values of residual litters showed nonlinear increase and decrease, respectively compared to initial isotopic values during decomposition. Litter of different functional types and chemical quality converged toward a conservative nutrient use strategy through mechanisms of slow decomposition and slow nutrient mobilization. Our results indicate that litter quality and season, are the most important regulators of litter decomposition in these forests. The results revealed significant relationships between litter decomposition rates and N, C:N ratio and P, and seasonality (temperature). These results and the convergence of different litters towards conservative nutrient use in these nutrient constrained ecosystems imply optimization of litter management because litter removal can have cascading effects on litter decomposition and nutrient availability in these systems. PMID:26915037

  10. Early-stage changes in natural (13)C and (15)N abundance and nutrient dynamics during different litter decomposition.

    PubMed

    Gautam, Mukesh Kumar; Lee, Kwang-Sik; Song, Byeong-Yeol; Lee, Dongho; Bong, Yeon-Sik

    2016-05-01

    Decomposition, nutrient, and isotopic (δ(13)C and δ(15)N) dynamics during 1 year were studied for leaf and twig litters of Pinus densiflora, Castanea crenata, Erigeron annuus, and Miscanthus sinensis growing on a highly weathered soil with constrained nutrient supply using litterbags in a cool temperate region of South Korea. Decay constant (k/year) ranged from 0.58 to 1.29/year, and mass loss ranged from 22.36 to 58.43 % among litter types. The results demonstrate that mass loss and nutrient dynamics of decomposing litter were influenced by the seasonality of mineralization and immobilization processes. In general, most nutrients exhibited alternate phases of rapid mineralization followed by gradual immobilization, except K, which was released throughout the field incubation. At the end of study, among all the nutrients only N and P showed net immobilization. Mobility of different nutrients from decomposing litter as the percentage of initial litter nutrient concentration was in the order of K > Mg > Ca > N ≈ P. The δ(13)C (0.32-6.70 ‰) and δ(15)N (0.74-3.90 ‰) values of residual litters showed nonlinear increase and decrease, respectively compared to initial isotopic values during decomposition. Litter of different functional types and chemical quality converged toward a conservative nutrient use strategy through mechanisms of slow decomposition and slow nutrient mobilization. Our results indicate that litter quality and season, are the most important regulators of litter decomposition in these forests. The results revealed significant relationships between litter decomposition rates and N, C:N ratio and P, and seasonality (temperature). These results and the convergence of different litters towards conservative nutrient use in these nutrient constrained ecosystems imply optimization of litter management because litter removal can have cascading effects on litter decomposition and nutrient availability in these systems.

  11. 15N chemical shift tensors and conformation of solid polypeptides containing 15N-labeled glycine residue by 15N NMR

    NASA Astrophysics Data System (ADS)

    Shoji, Akira; Ozaki, Takuo; Fujito, Teruaki; Deguchi, Kenzo; Ando, Isao; Magoshi, Jun

    1998-01-01

    The correlation between the isotropic 15N chemical shift ( δiso) and 15N chemical shift tensor components ( δ11, δ22 and δ33) and the main-chain conformation such as the polyglycine I (PGI: β-sheet), II (PGII: 3 1-helix), α-helix and β-sheet forms of solid polypeptides [Gly∗,X] n consisting of 15N-labeled glycine (Gly∗) and other amino acids (X: natural abundance of 15N) has been studied by solid-state 15N NMR method. A series of polypeptides [Gly∗,X] n (X = glycine, L-alanine, L-leucine, L-valine, L-isoleucine, β-benzyl L-aspartate, γ-benzyl L-glutamate, ɛ-carbobenzoxy L-lysine, and sarcosine) were synthesized by the α-amino acid N-carboxy anhydride (NCA) method. Conformations of these polypeptides in the solid state were characterized on the basis of conformation-dependent 13C chemical shifts in the 13C cross-polarization-magic angle spinning (CP-MAS) NMR spectra and by the characteristic bands in the IR and far-IR spectra. The δiso, δ11, δ22 and δ33 of the polypetides were determined from the 15N CP-MAS and 15N CP-static (powder pattern) spectra. It was found that the δiso, δ11, δ22 and δ33 in the PGI form (δ 83.5, 185, 40.7 and 25 ppm, resp.) are upfield from those in the PGII form (88.5, 194, 42.1 and 29 ppm, resp.), which were reproduced by the calculated 15N shielding constants using the finite perturbation theory (FPT)-INDO method. It was also found that the δ22 of the Gly∗ of [Gly∗,X] n is closely related to the main-chain conformation and the neighboring amino acid sequence, although the δiso is almost independent of the glycine content and conformation. Consequently, the δ22 value of Gly∗ containing copolypeptides is useful for the structural (main-chain conformation and neighboring amino acid sequence) analysis in the solid state by 15N NMR, if the 15N-labeled copolypeptide or natural protein can be provided. In addition, it is shown that the δiso of the glycine residue is useful for the conformational study of some

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

    PubMed

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

    2003-01-01

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

  13. The “Speedy” Synthesis of Atom-Specific 15N Imino/Amido-Labeled RNA

    PubMed Central

    Kreutz, Christoph; Micura, Ronald

    2016-01-01

    Although numerous reports on the synthesis of atom-specific 15N-labeled nucleosides exist, fast and facile access to the corresponding phosphoramidites for RNA solid-phase synthesis is still lacking. This situation represents a severe bottleneck for NMR spectroscopic investigations on functional RNAs. Here, we present optimized procedures to speed up the synthesis of 15N(1) adenosine and 15N(1) guanosine amidites, which are the much needed counterparts of the more straightforward-to-achieve 15N(3) uridine and 15N(3) cytidine amidites in order to tap full potential of 1H/15N/15N-COSY experiments for directly monitoring individual Watson–Crick base pairs in RNA. Demonstrated for two preQ1 riboswitch systems, we exemplify a versatile concept for individual base-pair labeling in the analysis of conformationally flexible RNAs when competing structures and conformational dynamics are encountered. PMID:26237536

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

    DOEpatents

    Chen, Xian; Gupta, Goutam; Bradbury, E. Morton

    2001-01-01

    Preparation of .sup.13 C/.sup.15 N-labeled DNA oligomers using the polymerase chain reaction (PCR). A PCR based method for uniform (.sup.13 C/.sup.15 N)-labeling of DNA duplexes is described. Multiple copies of a blunt-ended duplex are cloned into a plasmid, each copy containing the sequence of interest and restriction Hinc II sequences at both the 5' and 3' ends. PCR using bi-directional primers and uniformly .sup.13 C/.sup.15 N-labeled dNTP precursors generates labeled DNA duplexes containing multiple copies of the sequence of interest. Twenty-four cycles of PCR, followed by restriction and purification, gave the uniformly .sup.13 C/.sup.15 N-labeled duplex sequence with a 30% yield. Such labeled duplexes find significant applications in multinuclear magnetic resonance spectroscopy.

  15. Synthesis and NMR of {sup 15}N-labeled DNA fragments

    SciTech Connect

    Jones, R.A.

    1994-12-01

    DNA fragments labeled with {sup 15}N at the ring nitrogens and at the exocyclic amino groups can be used to obtain novel insight into interactions such as base pairing, hydration, drug binding, and protein binding. A number of synthetic routes to {sup 15}N-labeled pyrimidine nucleosides, purines, and purine nucleosides have been reported. Moreover, many of these labeled bases or monomers have been incorporated into nucleic acids, either by chemical synthesis or by biosynthetic procedures. The focus of this chapter will be on the preparation of {sup 15}N-labeled purine 2{prime}-deoxynucleosides, their incorporation into DNA fragments by chemical synthesis, and the results of NMR studies using these labeled DNA fragments.

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

    PubMed

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

    2014-01-16

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

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

    PubMed Central

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

    2014-01-01

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

  18. Numerical evaluation of subsoil diffusion of (15) N labelled denitrification products during employment of the (15) N gas flux method in the field

    NASA Astrophysics Data System (ADS)

    Well, Reinhard; Buchen, Caroline; Lewicka-Szczebak, Dominika; Ruoss, Nicolas

    2016-04-01

    Common methods for measuring soil denitrification in situ include monitoring the accumulation of 15N labelled N2 and N2O evolved from 15N labelled soil nitrate pool in soil surface chambers. Gas diffusion is considered to be the main accumulation process. Because accumulation of the gases decreases concentration gradients between soil and chamber over time, gas production rates are underestimated if calculated from chamber concentrations. Moreover, concentration gradients to the non-labelled subsoil exist, inevitably causing downward diffusion of 15N labelled denitrification products. A numerical model for simulating gas diffusion in soil was used in order to determine the significance of this source of error. Results show that subsoil diffusion of 15N labelled N2 and N2O - and thus potential underestimation of denitrification derived from chamber fluxes - increases with cover closure time as well as with increasing diffusivity. Simulations based on the range of typical gas diffusivities of unsaturated soils show that the fraction of subsoil diffusion after chamber closure for 1 hour is always significant with values up to >30 % of total production of 15N labelled N2 and N2O. Field experiments for measuring denitrification with the 15N gas flux method were conducted. The ability of the model to predict the time pattern of gas accumulation was evaluated by comparing measured 15N2 concentrations and simulated values.

  19. In vivo uniform (15)N-isotope labelling of plants: using the greenhouse for structural proteomics.

    PubMed

    Ippel, Johannes H; Pouvreau, Laurice; Kroef, Toos; Gruppen, Harry; Versteeg, Geurt; van den Putten, Peter; Struik, Paul C; van Mierlo, Carlo P M

    2004-01-01

    Isotope labelling of proteins is important for progress in the field of structural proteomics. It enables the utilisation of the power of nuclear magnetic resonance spectroscopy (NMR) for the characterisation of the three-dimensional structures and corresponding dynamical features of proteins. The usual approach to obtain isotopically labelled protein molecules is by expressing the corresponding gene in bacterial or yeast host organisms, which grow on isotope-enriched media. This method has several drawbacks. Here, we demonstrate that it is possible to fully label a plant with (15)N-isotopes. The advantage of in vivo labelling of higher organisms is that all constituting proteins are labelled and become available as functional, post-translationally modified, correctly folded proteins. A hydroponics set-up was used to create the first example of a uniformly (15)N-labelled (> 98%) plant species, the potato plant (Solanum tuberosum L., cv. Elkana). Two plants were grown at low costs using potassium-[(15)N]-nitrate as the sole nitrogen source. At harvest time, a total of 3.6 kg of potato tubers and 1.6 kg of foliage, stolons and roots were collected, all of which were fully (15)N-labelled. Gram quantities of soluble (15)N-labelled proteins (composed mainly of the glycoprotein patatin and Kunitz-type protease inhibitors) were isolated from the tubers. NMR results on the complete proteome of potato sap and on an isolated protease inhibitor illustrate the success of the labelling procedure. The presented method of isotope labelling is easily modified to label other plants. Its envisioned impact in the field of structural proteomics of plants is discussed.

  20. An economical method for (15)N/(13)C isotopic labeling of proteins expressed in Pichia pastoris.

    PubMed

    Rodriguez, E; Krishna, N R

    2001-07-01

    We report a new and cost-effective approach to prepare (15)N/(13)C labeled proteins for NMR using the Pichia pastoris expression system. Four protocols (P1 to P4) were defined and compared using recombinant Ovine interferon-tau (rOvIFN-tau). Our results demonstrate that in order to get full incorporation of (15)N and (13)C, the isotopes are not totally required during the initial growth phase of P. pastoris culture. The addition of small amounts of (15)N and (13)C compounds 6 h prior to the methanol induction phase is sufficient to obtain 99% incorporation of heavy isotopes into the protein. Our optimized protocol P4 is two-thirds less costly than the classical method using (15)N and (13)C isotopes during the entire growth phase.

  1. Affordable uniform isotope labeling with (2)H, (13)C and (15)N in insect cells.

    PubMed

    Sitarska, Agnieszka; Skora, Lukasz; Klopp, Julia; Roest, Susan; Fernández, César; Shrestha, Binesh; Gossert, Alvar D

    2015-06-01

    For a wide range of proteins of high interest, the major obstacle for NMR studies is the lack of an affordable eukaryotic expression system for isotope labeling. Here, a simple and affordable protocol is presented to produce uniform labeled proteins in the most prevalent eukaryotic expression system for structural biology, namely Spodoptera frugiperda insect cells. Incorporation levels of 80% can be achieved for (15)N and (13)C with yields comparable to expression in full media. For (2)H,(15)N and (2)H,(13)C,(15)N labeling, incorporation is only slightly lower with 75 and 73%, respectively, and yields are typically twofold reduced. The media were optimized for isotope incorporation, reproducibility, simplicity and cost. High isotope incorporation levels for all labeling patterns are achieved by using labeled algal amino acid extracts and exploiting well-known biochemical pathways. The final formulation consists of just five commercially available components, at costs 12-fold lower than labeling media from vendors. The approach was applied to several cytosolic and secreted target proteins. PMID:25929326

  2. Soil and foliar nutrient and nitrogen isotope composition (δ(15)N) at 5 years after poultry litter and green waste biochar amendment in a macadamia orchard.

    PubMed

    Bai, Shahla Hosseini; Xu, Cheng-Yuan; Xu, Zhihong; Blumfield, Timothy J; Zhao, Haitao; Wallace, Helen; Reverchon, Frédérique; Van Zwieten, Lukas

    2015-03-01

    This study aimed to evaluate the improvement in soil fertility and plant nutrient use in a macadamia orchard following biochar application. The main objectives of this study were to assess the effects of poultry litter and green waste biochar applications on nitrogen (N) cycling using N isotope composition (δ(15)N) and nutrient availability in a soil-plant system at a macadamia orchard, 5 years following application. Biochar was applied at 10 t ha(-1) dry weight but concentrated within a 3-m diameter zone when trees were planted in 2007. Soil and leaf samples were collected in 2012, and both soil and foliar N isotope composition (δ(15)N) and nutrient concentrations were assessed. Both soil and foliar δ(15)N increased significantly in the poultry litter biochar plots compared to the green waste biochar and control plots. A significant relationship was observed between soil and plant δ(15)N. There was no influence of either biochars on foliar total N concentrations or soil NH4 (+)-N and NO3 (-)-N, which suggested that biochar application did not pose any restriction for plant N uptake. Plant bioavailable phosphorus (P) was significantly higher in the poultry litter biochar treatment compared to the green waste biochar treatment and control. We hypothesised that the bioavailability of N and P content of poultry litter biochar may play an important role in increasing soil and plant δ(15)N and P concentrations. Biochar application affected soil-plant N cycling and there is potential to use soil and plant δ(15)N to investigate N cycling in a soil-biochar-tree crop system. The poultry litter biochar significantly increased soil fertility compared to the green waste biochar at 5 years following biochar application which makes the poultry litter a better feedstock to produce biochar compared to green waste for the tree crops.

  3. Measurement of multiple psi torsion angles in uniformly 13C,15N-labeled alpha-spectrin SH3 domain using 3D 15N-13C-13C-15N MAS dipolar-chemical shift correlation spectroscopy.

    PubMed

    Ladizhansky, Vladimir; Jaroniec, Christopher P; Diehl, Annette; Oschkinat, Hartmut; Griffin, Robert G

    2003-06-01

    We demonstrate the simultaneous measurement of several backbone torsion angles psi in the uniformly (13)C,(15)N-labeled alpha-Spectrin SH3 domain using two different 3D 15N-13C-13C-15N dipolar-chemical shift magic-angle spinning (MAS) NMR experiments. The first NCCN experiment utilizes double quantum (DQ) spectroscopy combined with the INADEQUATE type 13C-13C chemical shift correlation. The decay of the DQ coherences formed between 13C'(i) and 13C(alphai) spin pairs is determined by the "correlated" dipolar field due to 15N(i)-13C(alphai) and 13C'(i)-15N(i+1) dipolar couplings and is particularly sensitive to variations of the torsion angle in the regime |psi| > 140 degrees. However, the ability of this experiment to constrain multiple psi-torsion angles is limited by the resolution of the 13C(alpha)-(13)CO correlation spectrum. This problem is partially addressed in the second approach described here, which is an NCOCA NCCN experiment. In this case the resolution is enhanced by the superior spectral dispersion of the 15N resonances present in the 15N(i+1)-13C(alphai) part of the NCOCA chemical shift correlation spectrum. For the case of the 62-residue alpha-spectrin SH3 domain, we determined 13 psi angle constraints with the INADEQUATE NCCN experiment and 22 psi constraints were measured in the NCOCA NCCN experiment.

  4. Automated Protein Turnover Calculations from 15N Partial Metabolic Labeling LC/MS Shotgun Proteomics Data

    PubMed Central

    Lyon, David; Castillejo, Maria Angeles; Staudinger, Christiana; Weckwerth, Wolfram; Wienkoop, Stefanie; Egelhofer, Volker

    2014-01-01

    Protein turnover is a well-controlled process in which polypeptides are constantly being degraded and subsequently replaced with newly synthesized copies. Extraction of composite spectral envelopes from complex LC/MS shotgun proteomics data can be a challenging task, due to the inherent complexity of biological samples. With partial metabolic labeling experiments this complexity increases as a result of the emergence of additional isotopic peaks. Automated spectral extraction and subsequent protein turnover calculations enable the analysis of gigabytes of data within minutes, a prerequisite for systems biology high throughput studies. Here we present a fully automated method for protein turnover calculations from shotgun proteomics data. The approach enables the analysis of complex shotgun LC/MS 15N partial metabolic labeling experiments. Spectral envelopes of 1419 peptides can be extracted within an hour. The method quantifies turnover by calculating the Relative Isotope Abundance (RIA), which is defined as the ratio between the intensity sum of all heavy (15N) to the intensity sum of all light (14N) and heavy peaks. To facilitate this process, we have developed a computer program based on our method, which is freely available to download at http://promex.pph.univie.ac.at/protover. PMID:24736476

  5. Stereospecific assignments of glycine in proteins by stereospecific deuteration and {sup 15}N labeling

    SciTech Connect

    Hansen, A.P.; Curley, R.W. Jr.; Panigot, M.J.; Fesik, S.W.

    1994-12-01

    Stereospecific assignments are important for accurately determining the three-dimensional structures of proteins through the use of multidimensional NMR techniques. It is especially important to stereospecifically assign the glycine {alpha}-protons in proteins because of the potential for different backbone conformations of this residue. These stereospecific assignments are critical for interpreting the {sup 3}J{sub NH,{alpha}H} coupling constants and NOEs involving the glycine {alpha}-protons that determine the conformation of this part of the protein. However, it is often difficult to unambiguously obtain the stereospecific assignments for glycine residues by using only NOE data. In this poster, we present a method for unambiguous, stereospecific assignment of the {alpha}-protons of glycine residues. This method involves synthesis of stereo-specifically deuterated and {sup 15}N-labeled Gly using a slightly modified procedure originally described by Woodard and coworkers for the stereoselective deuteration of glycine. The stereospecifically deuterated and {sup 15}N-labeled Gy has been incorporated into recombinant proteins expressed in both bacterial systems (FKBP) and mammalian cells (u-PA). Two- and three-dimensional isotope-filtered and isotope-edited NMR experiments were used to obtain the stereospecific assignments of the glycine {alpha}-protons for these proteins.

  6. A spectral correlation function for efficient sequential NMR assignments of uniformly (15)N-labeled proteins.

    PubMed

    Bartels, C; Wüthrich, K

    1994-11-01

    A new computer-based approach is described for efficient sequence-specific assignment of uniformly (15)N-labeled proteins. For this purpose three-dimensional (15)N-correlated [(1)H, (1)H]-NOESY spectra are divided up into two-dimensional (1)H-(1)H strips which extend over the entire spectral width along one dimension and have a width of ca. 100 Hz, centered about the amide proton chemical shifts along the other dimension. A spectral correlation function enables sorting of these strips according to proximity of the corresponding residues in the amino acid sequence. Thereby, starting from a given strip in the spectrum, the probability of its corresponding to the C-terminal neighboring residue is calculated for all other strips from the similarity of their peak patterns with a pattern predicted for the sequentially adjoining residue, as manifested in the scalar product of the vectors representing the predicted and measured peak patterns. Tests with five different proteins containing both α-helices and β-sheets, and ranging in size from 58 to 165 amino acid residues show that the discrimination achieved between the sequentially neighboring residue and all other residues compares well with that obtained with an unguided interactive search of pairs of sequentially neighboring strips, with important savings in the time needed for complete analysis of 3D (15)N-correlated [(1)H, (1)H]-NOESY spectra. The integration of this routine into the program package XEASY ensures that remaining ambiguities can be resolved by visual inspection of the strips, combined with reference to the amino acid sequence and information on spin-system types obtained from additional NMR spectra.

  7. Cosine Modulated HSQC: A Rapid Determination of 3JHNHα Scalar Couplings in 15N-labeled Proteins

    NASA Astrophysics Data System (ADS)

    Petit, Audrey; Vincent, Sébastien J. F.; Zwahlen, Catherine

    2002-06-01

    A two-dimensional HSQC-based NMR method, 15N-COSMO-HSQC, is presented for the rapid determination of homonuclear 3JHNHα couplings in 15N-labeled proteins in solution. Scalar couplings are extracted by comparing the intensity of two separate datasets recorded with and without decoupling of the 3JHNHα during a preparation period. The scalar couplings are introduced through a cosine modulation of the peak intensities. The experiment relies on a BIRD sandwich to selectively invert all amide protons H N and is very simple to implement. 3JHNHα couplings were determined using both the 15N-COSMO-HSQC and quantitative- J on 15N-labeled chemokine RANTES. The two experiments show well-correlated values.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Römer, Winfried; Wu, Ting-Di; Duchambon, Patricia; Amessou, Mohamed; Carrez, Danièle; 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.

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

    PubMed Central

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

    2013-01-01

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

  11. 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 (δ15N 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

  12. Production of 15N-Labelled Liquid Organic Fertilisers Based on Manure and Crop Residue for Use in Fertigation Studies.

    PubMed

    Martínez-Alcántara, Belén; Martínez-Cuenca, Mary-Rus; Fernández, Carlos; Legaz, Francisco; Quiñones, Ana

    2016-01-01

    Large quantities of crop residue and animal manure from agricultural and livestock activities are annually produced worldwide. With proper management, these residues are potentially valuable sources of plant nutrients, mainly N. Recycling such subproducts in sustainably-based agricultural systems can minimise the use of mineral fertilisers, and hence reduce the potential risk of surface and groundwater pollution. Therefore, the purpose of this study was to obtain (small scale) two liquid labelled-organic fertilisers, an animal- and a vegetal-based organic (AO and VO, respectively) fertiliser, to be used as organic N sources in subsequent fertigation studies. Forage maize (Zea mays L.) grown under 15N-labelled fertiliser supply was used as raw material for VO fertiliser production, and also as 15N-labelled sheep feed to obtain 15N-labelled manure. The labelled faeces fraction was used as raw material for the AO fertiliser. The VO fertiliser was obtained after an acidic and an enzyme-driven hydrolysis. The AO fertiliser was obtained after acidic hydrolysis. The VO liquid fertiliser presented an N concentration of 330 mg·L-1, 85% of total N was organic, while ammonium and nitrate N accounted for 55% and 45% of the mineral nitrogen fraction, respectively. This fertiliser also exhibited high K, Ca and S concentrations and notable values for the remaining macro- and micronutrients. The AO liquid fertiliser had a similar total N concentration (496 mg·L-1, 82% of total N in an organic form) to that of VO, but its mineral N fraction significantly differed, which came in a predominantly (95%) ammonia form. It also had a high content of N, P, K and other macronutrients, and sufficient Fe, Zn, Mn, Cu and B levels, which suggests its suitability as a potential fertiliser. The percentage of 15N enrichment in both VO and AO liquid fertilisers exceeded 2% 15N atom excess, which enabled their use in subsequent assays run to assess nitrogen uptake efficiency.

  13. Nitrogen mineralization from selected /sup 15/N-labelled crop residues and humus as affected by inorganic nitrogen

    SciTech Connect

    Santos, J.A.

    1987-01-01

    The use of cover crops or crop residues as a source of N to succeeding crops has become a matter of increasing importance for economic and environmental reason. Greenhouse and field studies were conducted to determine the N contribution of four /sup 15/N labelled crop residues, rye (Secale cereale L.), wheat (Triticum aestivum L.), crimson clover (Trifolium encarnatum L.), and hairy vetch (Vicia sativa L.), to successive crops and to evaluate the effect of different organic (ON) and inorganic N (IN) combinations on mineralization of the above residues. Total /sup 15/N recovery from the residues ranged from 51% to 85% and 4% to 74% for the greenhouse and field studies, respectively.

  14. 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.

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

    SciTech Connect

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

    1994-12-01

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

  16. Exploring the nitrogen ingestion of aphids--a new method using electrical penetration graph and (15)N labelling.

    PubMed

    Kuhlmann, Franziska; Opitz, Sebastian E W; Inselsbacher, Erich; Ganeteg, Ulrika; Näsholm, Torgny; Ninkovic, Velemir

    2013-01-01

    Studying plant-aphid interactions is challenging as aphid feeding is a complex process hidden in the plant tissue. Here we propose a combination of two well established methods to study nutrient acquisition by aphids focusing on the uptake of isotopically labelled nitrogen ((15)N). We combined the Electrical Penetration Graph (EPG) technique that allows detailed recording of aphid feeding behaviour and stable isotope ratio mass spectrometry (IRMS) to precisely measure the uptake of nitrogen. Bird cherry-oat aphids Rhopalosiphum padi L. (Hemiptera, Aphididae) fed for 24 h on barley plants (Hordeum vulgare L., cultivar Lina, Poaceae) that were cultivated with a (15)N enriched nutrient solution. The time aphids fed in the phloem was strongly positive correlated with their (15)N uptake. All other single behavioural phases were not correlated with (15)N enrichment in the aphids, which corroborates their classification as non-feeding EPG phases. In addition, phloem-feeding and (15)N enrichment of aphids was divided into two groups. One group spent only short time in the phloem phase and was unsuccessful in nitrogen acquisition, while the other group displayed longer phloem-feeding phases and was successful in nitrogen acquisition. This suggests that several factors such as the right feeding site, time span of feeding and individual conditions play a role for the aphids to acquire nutrients successfully. The power of this combination of methods for studying plant-aphid interactions is discussed.

  17. High Resolution 13C MRI With Hyperpolarized Urea: In Vivo T2 Mapping and 15N Labeling Effects

    PubMed Central

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

    2014-01-01

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

  18. Quantitative analysis of 15N labeled positional isomers of glutamine and citrulline via electrospray ionization tandem mass spectrometry of their dansyl derivatives

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The enteral metabolism of glutamine and citrulline are intertwined because, while glutamine is one of the main fuel sources for the enterocyte, citrulline is one of its products. It has been shown that the administration of 15N labeled glutamine results in the incorporation of the 15N label into cit...

  19. Site-specific φ- and ψ-torsion angle determination in a uniformly/extensively 13C- and 15N-labeled peptide

    NASA Astrophysics Data System (ADS)

    Wi, Sungsool; Spano, Justin

    2011-10-01

    A solid-state rotational-echo double resonance (REDOR) NMR method was introduced to identify the ϕ- and ψ-torsion angle from a 1H- 15N or 1H- 13C' spin system of alanine-like residues in a selectively, uniformly, or extensively 15N-/ 13C-labeled peptide. When a C α( i) or a 15N peak is site-specifically obtainable in the NMR spectrum of a uniformly 15N/ 13C-labeled sample system, the ψ- or ϕ-torsion angle specified by the conformational structure of peptide geometry involving 15N( i)- 1H αi - 15N( i + 1) or 13C'( i - 1)- 1H Ni- 13C'( i) spin system can be identified based on 13C α- or 15N-detected 1H α- 15N or 1H N- 13C REDOR experiment. This method will conveniently be utilized to identify major secondary motifs, such as α-helix, β-sheet, and β-turn, from a uniformly 15N-/ 13C-labled peptide sample system. When tested on a 13C-/ 15N-labeled model system of a three amino acid peptide Gly-[U- 13C, 15N]Ala-[U- 13C, 15N]Leu, the ψ-angle of alanine obtained experimentally, ψ = -40 ± 30°, agreed reasonably well with the X-ray determined angle, ψ = -39°.

  20. Production of 15N-Labelled Liquid Organic Fertilisers Based on Manure and Crop Residue for Use in Fertigation Studies.

    PubMed

    Martínez-Alcántara, Belén; Martínez-Cuenca, Mary-Rus; Fernández, Carlos; Legaz, Francisco; Quiñones, Ana

    2016-01-01

    Large quantities of crop residue and animal manure from agricultural and livestock activities are annually produced worldwide. With proper management, these residues are potentially valuable sources of plant nutrients, mainly N. Recycling such subproducts in sustainably-based agricultural systems can minimise the use of mineral fertilisers, and hence reduce the potential risk of surface and groundwater pollution. Therefore, the purpose of this study was to obtain (small scale) two liquid labelled-organic fertilisers, an animal- and a vegetal-based organic (AO and VO, respectively) fertiliser, to be used as organic N sources in subsequent fertigation studies. Forage maize (Zea mays L.) grown under 15N-labelled fertiliser supply was used as raw material for VO fertiliser production, and also as 15N-labelled sheep feed to obtain 15N-labelled manure. The labelled faeces fraction was used as raw material for the AO fertiliser. The VO fertiliser was obtained after an acidic and an enzyme-driven hydrolysis. The AO fertiliser was obtained after acidic hydrolysis. The VO liquid fertiliser presented an N concentration of 330 mg·L-1, 85% of total N was organic, while ammonium and nitrate N accounted for 55% and 45% of the mineral nitrogen fraction, respectively. This fertiliser also exhibited high K, Ca and S concentrations and notable values for the remaining macro- and micronutrients. The AO liquid fertiliser had a similar total N concentration (496 mg·L-1, 82% of total N in an organic form) to that of VO, but its mineral N fraction significantly differed, which came in a predominantly (95%) ammonia form. It also had a high content of N, P, K and other macronutrients, and sufficient Fe, Zn, Mn, Cu and B levels, which suggests its suitability as a potential fertiliser. The percentage of 15N enrichment in both VO and AO liquid fertilisers exceeded 2% 15N atom excess, which enabled their use in subsequent assays run to assess nitrogen uptake efficiency. PMID:26982183

  1. Production of 15N-Labelled Liquid Organic Fertilisers Based on Manure and Crop Residue for Use in Fertigation Studies

    PubMed Central

    Martínez-Alcántara, Belén; Martínez-Cuenca, Mary-Rus; Fernández, Carlos; Legaz, Francisco; Quiñones, Ana

    2016-01-01

    Large quantities of crop residue and animal manure from agricultural and livestock activities are annually produced worldwide. With proper management, these residues are potentially valuable sources of plant nutrients, mainly N. Recycling such subproducts in sustainably-based agricultural systems can minimise the use of mineral fertilisers, and hence reduce the potential risk of surface and groundwater pollution. Therefore, the purpose of this study was to obtain (small scale) two liquid labelled-organic fertilisers, an animal- and a vegetal-based organic (AO and VO, respectively) fertiliser, to be used as organic N sources in subsequent fertigation studies. Forage maize (Zea mays L.) grown under 15N-labelled fertiliser supply was used as raw material for VO fertiliser production, and also as 15N-labelled sheep feed to obtain 15N-labelled manure. The labelled faeces fraction was used as raw material for the AO fertiliser. The VO fertiliser was obtained after an acidic and an enzyme-driven hydrolysis. The AO fertiliser was obtained after acidic hydrolysis. The VO liquid fertiliser presented an N concentration of 330 mg·L-1, 85% of total N was organic, while ammonium and nitrate N accounted for 55% and 45% of the mineral nitrogen fraction, respectively. This fertiliser also exhibited high K, Ca and S concentrations and notable values for the remaining macro- and micronutrients. The AO liquid fertiliser had a similar total N concentration (496 mg·L-1, 82% of total N in an organic form) to that of VO, but its mineral N fraction significantly differed, which came in a predominantly (95%) ammonia form. It also had a high content of N, P, K and other macronutrients, and sufficient Fe, Zn, Mn, Cu and B levels, which suggests its suitability as a potential fertiliser. The percentage of 15N enrichment in both VO and AO liquid fertilisers exceeded 2% 15N atom excess, which enabled their use in subsequent assays run to assess nitrogen uptake efficiency. PMID:26982183

  2. Non-homogeneity of isotopic labelling in 15N gas flux studies: theory, some observations and possible lessons

    NASA Astrophysics Data System (ADS)

    Well, Reinhard; Buchen, Caroline; Deppe, Marianna; Eschenbach, Wolfram; Gattinger, Andreas; Giesemann, Anette; Krause, Hans-Martin; Lewicka-Szczebak, Dominika

    2015-04-01

    Quantifying dinitrogen (N2) and nitrous oxide (N2O) fluxes from different soil N pools and processes can be accomplished using the 15N tracer technique but this is subject to four different sources of bias (i. - iv.). This approach includes 15N labelling of selected N pools in soil and subsequent isotope analysis of all relevant N pools as well as of gas samples from enclosures, i.e. mixtures of soil-derived and atmospheric N2 and N2O. Depending on the processes of interest, there may be 15N labelling of one or several N pools, were several labelling treatment are needed in the latter case (e.g. Müller et al., 2004). Measuring pool-derived N2 or N2O has been shown to include two calculation problems, (i.) arising from multiple pools (e.g. Arah, 1992) and (ii.) dealing with the non-random distribution of N2 and N2O mole masses (Hauck et al., 1958). Non-randomness can be solved if m/z 28, 29 and 30 are correctly analysed and the 15N enrichment of one (to distinguish two pools, i.e. soil and atmosphere) or two pools (in case of three pools) is known (Spott & Stange, 2008). Moreover (iii.), NO3- pools generating N2 and N2O via denitrification can be identical or different, e.g. if N2O evolved from higher enriched NO3- in deeper soil was more reduced to N2 compared to N2O evolved from N2O from shallow soil with lower enrichment, or vice versa. Apportioning N2O fluxes to NH4+ (nitrification and/or nitrifier denitrification) and NO3- (denitrification) is often conducted by NO3-labeling, measuring δ15N of emitted N2O and applying mixing equations were the measured 15N enrichment of NH4+and NO3-pool is used. However, this assumes that the average 15N enrichment of NH4+and NO3-in the soil is identical to the enrichment in the active soil domain producing N2 and/or N2O. Violation of this precondition must lead to bias in source apportionment (iv.), but to our knowledge this has not been investigated until now. Here we present conceptual models and model calculations

  3. Nitrogen and Carbon Flows Estimated by 15N and 13C Pulse-Chase Labeling during Regrowth of Alfalfa.

    PubMed Central

    Avice, J. C.; Ourry, A.; Lemaire, G.; Boucaud, J.

    1996-01-01

    The flow of 15N and 13C from storage compounds in organs remaining after defoliation (sources) to regrowing tissue (sinks), and 13C losses through root or shoot respiration were assessed by pulse-chase labeling during regrowth of alfalfa (Medicago sativa L.) following shoot removal. A total of 73% of labeled C and 34% of labeled N were mobilized in source organs within 30 d. Although all of the 15N from source organs was recovered in the regrowing tissue, much of the 13C was lost, mainly as CO2 respired from the root (61%) or shoot (8%), and was found to a lesser extent in sink tissue (5%). After 3, 10, or 30 d of regrowth, 87, 66, and 52% of shoot N, respectively, was derived from source tissue storage compounds; the rest resulted from translocation of fixed N2. Overall results suggest that most shoot C was linked to photosynthetic activity rather than being derived from mobilization of stored C in source organs. Furthermore, isotopic analysis of different chemical fractions of plant tissue suggests that between 14 and 58% of the shoot C derived from source tissues was linked to the mobilization of N compounds, not carbohydrates. PMID:12226391

  4. Mapping membrane protein backbone dynamics: a comparison of site-directed spin labeling with NMR 15N-relaxation measurements.

    PubMed

    Lo, Ryan H; Kroncke, Brett M; Solomon, Tsega L; Columbus, Linda

    2014-10-01

    The ability to detect nanosecond backbone dynamics with site-directed spin labeling (SDSL) in soluble proteins has been well established. However, for membrane proteins, the nitroxide appears to have more interactions with the protein surface, potentially hindering the sensitivity to backbone motions. To determine whether membrane protein backbone dynamics could be mapped with SDSL, a nitroxide was introduced at 55 independent sites in a model polytopic membrane protein, TM0026. Electron paramagnetic resonance spectral parameters were compared with NMR (15)N-relaxation data. Sequential scans revealed backbone dynamics with the same trends observed for the R1 relaxation rate, suggesting that nitroxide dynamics remain coupled to the backbone on membrane proteins.

  5. Production, Purification, and Characterization of 15N-Labeled DNA Repair Proteins as Internal Standards for Mass Spectrometric Measurements

    PubMed Central

    Jaruga, Pawel; Nelson, Bryant C.; Lowenthal, Mark S.; Jemth, Ann-Sofie; Loseva, Olga; Coskun, Erdem; Helleday, Thomas

    2016-01-01

    Oxidatively induced DNA damage is caused in living organisms by a variety of damaging agents, resulting in the formation of a multiplicity of lesions, which are mutagenic and cytotoxic. Unless repaired by DNA repair mechanisms before DNA replication, DNA lesions can lead to genomic instability, which is one of the hallmarks of cancer. Oxidatively induced DNA damage is mainly repaired by base excision repair pathway with the involvement of a plethora of proteins. Cancer tissues develop greater DNA repair capacity than normal tissues by overexpressing DNA repair proteins. Increased DNA repair in tumors that removes DNA lesions generated by therapeutic agents before they became toxic is a major mechanism in the development of therapy resistance. Evidence suggests that DNA repair capacity may be a predictive biomarker of patient response. Thus, knowledge of DNA–protein expressions in disease-free and cancerous tissues may help predict and guide development of treatments and yield the best therapeutic response. Our laboratory has developed methodologies that use mass spectrometry with isotope dilution for the measurement of expression of DNA repair proteins in human tissues and cultured cells. For this purpose, full-length 15N-labeled analogs of a number of human DNA repair proteins have been produced and purified to be used as internal standards for positive identification and accurate quantification. This chapter describes in detail the protocols of this work. The use of 15N-labeled proteins as internal standards for the measurement of several DNA repair proteins in vivo is also presented. PMID:26791985

  6. Ner protein of phage Mu: Assignments using {sup 13}C/{sup 15}N-labeled protein

    SciTech Connect

    Strzelecka, T.; Gronenborn, A.M.; Clore, G.M.

    1994-12-01

    The Ner protein is a small (74-amino acid) DNA-binding protein that regulates a switch between the lysogenic and lytic stages of phage Mu. It inhibits expression of the C repressor gene and down-regulates its own expression. Two-dimensional NMR experiments on uniformly {sup 15}N-labeled protein provided most of the backbone and some of the sidechain proton assignments. The secondary structure determination using two-dimensional NOESY experiments showed that Ner consists of five {alpha}-helices. However, because most of the sidechain protons could not be assigned, the full structure was not determined. Using uniformly {sup 13}C/{sup 15}N-labeled Ner and a set of three-dimensional experiments, we were able to assign all of the backbone and 98% of the sidechain protons. In particular, the CBCANH and CBCA(CO)NH experiments were used to sequentially assign the C{alpha} and C{beta} resonances; the HCCH-CTOCSY and HCCH-COSY were used to assign sidechain carbon and proton resonances.

  7. Identification of the magnesium-histidine stretching vibration of the bacteriochlorophyll cofactors in photosynthetic reaction centers via {sup 15}N-labeling of the histidines

    SciTech Connect

    Czarnecki, K.; Bocian, D.F.; Chynwat, V.; Erickson, J.P.; Frank, H.A.

    1997-03-12

    In this communication, we report low-frequency, near-infrared-exciation RR spectra of bacterial RCs in which the histidine residues of the protein are selectively labeled with {sup 15}N. For practical reasons, the studies were conducted by comparing the vibrational signatures of RCs in which {sup 15}N was universally incorporated (all cofactors and all protein residues) (designated all-{sup 15}N RCs) with those in which [{sup 14}N]histidine was introduced as a reverse label (disignated {sup 14}N-His RCs) into the all {sup 15}N-labeled RCs. The studies of the histidine-labeled RCs reveal that the vibrational characteristics of the BChl core are far more complicated than originally anticipated. These results have clear implications for the photoexcitation dynamics of the BChls in RCs and may also have significant consequences for the dynamics of exogenous ligand binding to heme-based oxygen carriers. 12 refs., 2 figs.

  8. Determination of Multimodal Isotopic Distributions: The Case of a (15)N Labeled Protein Produced into Hairy Roots.

    PubMed

    Trouillard, Romain; Hubert-Roux, Marie; Tognetti, Vincent; Guilhaudis, Laure; Plasson, Carole; Menu-Bouaouiche, Laurence; Coquet, Laurent; Guerineau, François; Hardouin, Julie; Ele Ekouna, Jean-Pierre; Cosette, Pascal; Lerouge, Patrice; Boitel-Conti, Michèle; Afonso, Carlos; Ségalas-Milazzo, Isabelle

    2015-06-16

    Isotopic labeling is widely used in various fields like proteomics, metabolomics, fluxomics, as well as in NMR structural studies, but it requires an efficient determination of the isotopic enrichment. Mass spectrometry is the method of choice for such analysis. However, when complex expression systems like hairy roots are used for production, multiple populations of labeled proteins may be obtained. If the isotopic incorporation determination is actually well-known for unimodal distributions, the multimodal distributions have scarcely been investigated. Actually, only a few approaches allow the determination of the different labeled population proportions from multimodal distributions. Furthermore, they cannot be used when the number of the populations and their respective isotope ratios are unknown. The present study implements a new strategy to measure the (15)N labeled populations inside a multimodal distribution knowing only the peptide sequence and peak intensities from mass spectrometry analyses. Noteworthy, it could be applied to other elements, like carbon and hydrogen, and extended to a larger range of biomolecules.

  9. Partitioning Residue-derived and Residue-induced Emissions of N2O Using 15N-labelled Crop Residues

    NASA Astrophysics Data System (ADS)

    Farrell, R. E.; Carverhill, J.; Lemke, R.; Knight, J. D.

    2014-12-01

    Estimates of N2O emissions in Canada indicate that 17% of all agriculture-based emissions are associated with the decomposition of crop residues. However, research specific to the western Canadian prairies (including Saskatchewan) has shown that the N2O emission factor for N sources in this region typically ranges between 0.2 and 0.6%, which is well below the current IPCC default emission factor of 1.0%. Thus, it stands to reason that emissions from crop residues should also be lower than those calculated using the current IPCC emission factor. Current data indicates that residue decomposition, N mineralization and N2O production are affected by a number of factors such as C:N ratio and chemical composition of the residue, soil type, and soil water content; thus, a bench-scale incubation study was conducted to examine the effects of soil type and water content on N2O emissions associated with the decomposition of different crop residues. The study was carried out using soils from the Black, Dark Brown, Brown, and Gray soil zones and was conducted at both 50% and 70% water-filled pore space (WFPS); the soils were amended with 15N-labeled residues of wheat, pea, canola, and flax, or with an equivalent amount of 15N-labeled urea; 15N2O production was monitored using a Picarro G5101-i isotopic N2O analyzer. Crop residue additions to the soils resulted in both direct and indirect emissions of N2O, with residue derived emissions (RDE; measured as 15N2O) generally exceeding residue-induced emissions (RIE) at 50% WFPS—with RDEs ranging from 42% to 88% (mean = 58%) of the total N2O. Conversely, at 70% WFPS, RDEs were generally lower than RIEs—ranging from 21% to 83% (mean = 48%). Whereas both water content and soil type had an impact on N2O production, there was a clear and consistent trend in the emission factors for the residues; i.e., emissions were always greatest for the canola residue and lowest for the wheat residue and urea fertilizer; and intermediate for pea

  10. A facile method for expression and purification of (15)N isotope-labeled human Alzheimer's β-amyloid peptides from E. coli for NMR-based structural analysis.

    PubMed

    Sharma, Sudhir C; Armand, Tara; Ball, K Aurelia; Chen, Anna; Pelton, Jeffrey G; Wemmer, David E; Head-Gordon, Teresa

    2015-12-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disease affecting millions of people worldwide. AD is characterized by the presence of extracellular plaques composed of aggregated/oligomerized β-amyloid peptides with Aβ42 peptide representing a major isoform in the senile plaques. Given the pathological significance of Aβ42 in the progression of AD, there is considerable interest in understanding the structural ensembles for soluble monomer and oligomeric forms of Aβ42. This report describes an efficient method to express and purify high quality (15)N isotope-labeled Aβ42 for structural studies by NMR. The protocol involves utilization of an auto induction system with (15)N isotope labeled medium, for high-level expression of Aβ42 as a fusion with IFABP. After the over-expression of the (15)N isotope-labeled IFABP-Aβ42 fusion protein in the inclusion bodies, pure (15)N isotope-labeled Aβ42 peptide is obtained following a purification method that is streamlined and improved from the method originally developed for the isolation of unlabeled Aβ42 peptide (Garai et al., 2009). We obtain a final yield of ∼ 6 mg/L culture for (15)N isotope-labeled Aβ42 peptide. Mass spectrometry and (1)H-(15)N HSQC spectra of monomeric Aβ42 peptide validate the uniform incorporation of the isotopic label. The method described here is equally applicable for the uniform isotope labeling with (15)N and (13)C in Aβ42 peptide as well as its other variants including any Aβ42 peptide mutants.

  11. Expression, purification, and mass spectrometric analysis of 15N, 13C-labeled RGD-hirudin, expressed in Pichia pastoris, for NMR studies.

    PubMed

    Huang, Yinong; Zhang, Yanling; Wu, Yi; Wang, Jue; Liu, Xingang; Dai, Linsen; Wang, Longsheng; Yu, Min; Mo, Wei

    2012-01-01

    A novel recombinant hirudin, RGD-hirudin, inhibits the activity of thrombin and the aggregation of platelets. Here, we successfully expressed (15)N, (13)C-labeled RGD-hirudin in Pichia pastoris in a fermenter. The protein was subsequently purified to yield sufficient quantities for structural and functional studies. The purified protein was characterized by HPLC and MALDI-TOF mass spectroscopy. Analysis revealed that the protein was pure and uniformly labeled with (15)N and (13)C. A bioassay showed that the anti-thrombin activity and the anti-platelet aggregation ability of the labeled protein were the same as those of unlabeled RGD-hirudin. Multidimensional heteronuclear NMR spectroscopy has been used to determine almost complete backbone (15)N, (13)C and (1)H resonance assignments of the r-RGD-Hirudin. The (15)N-(1)H HSQC spectrum of uniformly (15)N, (13)C-labeled RGD-hirudin allowed successful assignment of the signals. Examples of the quality of the data are provided for the (15)N-(l)H correlation spectrum, and by selected planes of the CBCA(CO)NH, CBCANH, and HNCO experiments. These results provide a basis for further studies on the structure-function relationship of RGD-hirudin with thrombin and platelets. PMID:22879918

  12. hNCOcanH pulse sequence and a robust protocol for rapid and unambiguous assignment of backbone ((1)H(N), (15)N and (13)C') resonances in (15)N/(13)C-labeled proteins.

    PubMed

    Kumar, Dinesh; Hosur, Ramakrishna V

    2011-09-01

    A three-dimensional nuclear magnetic resonance (NMR) pulse sequence named as hNCOcanH has been described to aid rapid sequential assignment of backbone resonances in (15)N/(13)C-labeled proteins. The experiment has been derived by a simple modification of the previously described HN(C)N pulse sequence [Panchal et al., J. Biomol. NMR 20 (2001) 135-147]; t2 evolution is used to frequency label (13)C' rather than (15)N (similar trick has also been used in the design of hNCAnH pulse sequence from hNcaNH [Frueh et al., JACS, 131 (2009) 12880-12881]). The modification results in a spectrum equivalent to HNCO, but in addition to inter-residue correlation peaks (i.e. Hi , Ci-1), the spectrum also contains additional intra-residue correlation peaks (i.e. Hi-1 , Ci-1) in the direct proton dimension which has maximum resolution. This is the main strength of the experiment and thus, even a small difference in amide (1) H chemical shifts (5-6 Hz) can be used for establishing a sequential connectivity. This experiment in combination with the HNN experiment described previously [Panchal et al., J. Biomol. NMR 20 (2001) 135-147] leads to a more robust assignment protocol for backbone resonances ((1) H(N) , (15)N) than could be derived from the combination of HNN and HN(C)N experiments [Bhavesh et al., Biochemistry, 40 (2001) 14727-14735]. Further, this new protocol enables assignment of (13)C' resonances as well. We believe that the experiment and the protocol presented here will be of immense value for structural-and functional-proteomics research by NMR. Performance of this experiment has been demonstrated using (13)C/(15)N labeled ubiquitin.

  13. Simultaneous CT-13C and VT-15N chemical shift labelling: application to 3D NOESY-CH3NH and 3D 13C,15N HSQC-NOESY-CH3NH.

    PubMed

    Uhrín, D; Bramham, J; Winder, S J; Barlow, P N

    2000-11-01

    Based on the HSQC scheme, we have designed a 2D heterocorrelated experiment which combines constant time (CT) 13C and variable time (VT) 15N chemical shift labelling. Although applicable to all carbons, this mode is particularly suitable for simultaneous recording of methyl-carbon and nitrogen chemical shifts at high digital resolution. The methyl carbon magnetisation is in the transverse plane during the whole CT period (1/J(CC) = 28.6 ms). The magnetisation originating from NH protons is initially stored in the 2HzNz state, then prior to the VT chemical shift labelling period is converted into 2HzNy coherence. The VT -15N mode eliminates the effect of 1J(N,CO) and 1,2J(N,CA) coupling constants without the need for band-selective carbon pulses. An optional editing procedure is incorporated which eliminates signals from CH2 groups, thus removing any potential overlap with the CH3 signals. The CT-13CH3,VT-15N HSQC building block is used to construct two 3D experiments: 3D NOESY-CH3NH and 3D 13C,15N HSQC-NOESY-CH3NH. Combined use of these experiments yields proton and heteronuclear chemical shifts for moieties experiencing NOEs with CH3 and NH protons. These NOE interactions are resolved as a consequence of the high digital resolution in the carbon and nitrogen chemical shifts of CH3 and NH groups, respectively. The techniques are illustrated using a double labelled sample of the CH domain from calponin.

  14. hNCOcanH pulse sequence and a robust protocol for rapid and unambiguous assignment of backbone ((1)H(N), (15)N and (13)C') resonances in (15)N/(13)C-labeled proteins.

    PubMed

    Kumar, Dinesh; Hosur, Ramakrishna V

    2011-09-01

    A three-dimensional nuclear magnetic resonance (NMR) pulse sequence named as hNCOcanH has been described to aid rapid sequential assignment of backbone resonances in (15)N/(13)C-labeled proteins. The experiment has been derived by a simple modification of the previously described HN(C)N pulse sequence [Panchal et al., J. Biomol. NMR 20 (2001) 135-147]; t2 evolution is used to frequency label (13)C' rather than (15)N (similar trick has also been used in the design of hNCAnH pulse sequence from hNcaNH [Frueh et al., JACS, 131 (2009) 12880-12881]). The modification results in a spectrum equivalent to HNCO, but in addition to inter-residue correlation peaks (i.e. Hi , Ci-1), the spectrum also contains additional intra-residue correlation peaks (i.e. Hi-1 , Ci-1) in the direct proton dimension which has maximum resolution. This is the main strength of the experiment and thus, even a small difference in amide (1) H chemical shifts (5-6 Hz) can be used for establishing a sequential connectivity. This experiment in combination with the HNN experiment described previously [Panchal et al., J. Biomol. NMR 20 (2001) 135-147] leads to a more robust assignment protocol for backbone resonances ((1) H(N) , (15)N) than could be derived from the combination of HNN and HN(C)N experiments [Bhavesh et al., Biochemistry, 40 (2001) 14727-14735]. Further, this new protocol enables assignment of (13)C' resonances as well. We believe that the experiment and the protocol presented here will be of immense value for structural-and functional-proteomics research by NMR. Performance of this experiment has been demonstrated using (13)C/(15)N labeled ubiquitin. PMID:21818779

  15. An economic approach to efficient isotope labeling in insect cells using homemade 15N-, 13C- and 2H-labeled yeast extracts.

    PubMed

    Opitz, Christian; Isogai, Shin; Grzesiek, Stephan

    2015-07-01

    Heterologous expression of proteins in insect cells is frequently used for crystallographic structural studies due to the high yields even for challenging proteins requiring the eukaryotic protein processing capabilities of the host. However for NMR studies, the need for isotope labeling poses extreme challenges in eukaryotic hosts. Here, we describe a robust method to achieve uniform protein (15)N and (13)C labeling of up to 90 % in baculovirus-infected insect cells. The approach is based on the production of labeled yeast extract, which is subsequently supplemented to insect cell growth media. The method also allows deuteration at levels of >60 % without decrease in expression yield. The economic implementation of the labeling procedures into a standard structural biology laboratory environment is described in a step-by-step protocol. Applications are demonstrated for a variety of NMR experiments using the Abelson kinase domain, GFP, and the beta-1 adrenergic receptor as examples. Deuterated expression of the latter provides spectra of very high quality of a eukaryotic G-protein coupled receptor.

  16. Worms from venus and mars: proteomics profiling of sexual differences in Caenorhabditis elegans using in vivo 15N isotope labeling.

    PubMed

    Tops, Bastiaan B J; Gauci, Sharon; Heck, Albert J R; Krijgsveld, Jeroen

    2010-01-01

    Hermaphrodites of the nematode Caenorhabditis elegans produce both sperm and oocytes in the same germline. To investigate the process underlying spermatogenesis and oogenesis separately, we used a quantitative proteomics approach applied to two mutant worm lines (fem-3(q20) and fem-1(hc17)) developing only male and female germlines, respectively. We used stable isotopic labeling of whole animals by feeding them either (14)N or (15)N labeled Escherichia coli. This way, we could confidently identify and quantify 1040 proteins in two independent experiments. Of these, approximately 400 proteins showed significant differential expression between female-like and male-like animals. As expected, proteins linked to oogenesis were found to be highly upregulated in the feminized worms, whereas proteins involved in spermatogenesis were found to be highly upregulated in the masculinized worms. This was complemented by many proteins strongly enriched in either mutant. Although the function of the majority of these proteins is unknown, their expression profile indicates that they have an as yet unrecognized role in the development and/or function of the female- and male germline in C. elegans. We show that members of several protein complexes as well as functionally similar proteins show comparable abundance ratios, indicating coregulation of protein expression. Additional analysis comparing our protein data to a previously published microarray data set shows that mRNA and protein expression are poorly correlating. We provide one of the first examples of a large-scale quantitative proteomics experiment in C. elegans and show the potential and feasibility of an approach enabling system-wide accurate quantitative proteomics experiments in this model organism. PMID:19916504

  17. Interresidue carbonyl-carbonyl polarization transfer experiments in uniformly 13C, 15N-labeled peptides and proteins

    NASA Astrophysics Data System (ADS)

    Janik, Rafal; Ritz, Emily; Gravelle, Andrew; Shi, Lichi; Peng, Xiaohu; Ladizhansky, Vladimir

    2010-03-01

    In this work, we demonstrate that Homonuclear Rotary Resonance Recoupling (HORROR) can be used to reintroduce carbonyl-carbonyl interresidue dipolar interactions and to achieve efficient polarization transfer between carbonyl atoms in uniformly 13C, 15N-labeled peptides and proteins. We show that the HORROR condition is anisotropically broadened and overall shifted to higher radio frequency intensities because of the CSA effects. These effects are analyzed theoretically using Average Hamiltonian Theory. At spinning frequencies used in this study, 22 kHz, this broadening is experimentally found to be on the order of a kilohertz at a proton field of 600 MHz. To match HORROR condition over all powder orientations, variable amplitude radio frequency (RF) fields are required, and efficient direct transfers on the order of 20-30% can be straightforwardly established. Two- and three-dimensional chemical shift correlation experiments establishing long-range interresidue connectivities (e.g., (N[i]-CO[i - 2])) are demonstrated on the model peptide N-acetyl-valine-leucine, and on the third immunoglobulin binding domain of protein G. Possible future developments are discussed.

  18. Insights into nitrogen allocation and recycling from nitrogen elemental analysis and 15N isotope labelling in 14 genotypes of willow.

    PubMed

    Brereton, Nicholas J B; Pitre, Frederic E; Shield, Ian; Hanley, Steven J; Ray, Michael J; Murphy, Richard J; Karp, Angela

    2014-11-01

    Minimizing nitrogen (N) fertilization inputs during cultivation is essential for sustainable production of bioenergy and biofuels. The biomass crop willow (Salix spp.) is considered to have low N fertilizer requirements due to efficient recycling of nutrients during the perennial cycle. To investigate how successfully different willow genotypes assimilate and allocate N during growth, and remobilize and consequently recycle N before the onset of winter dormancy, N allocation and N remobilization (to and between different organs) were examined in 14 genotypes of a genetic family using elemental analysis and (15)N as a label. Cuttings were established in pots in April and sampled in June, August and at onset of senescence in October. Biomass yield of the trees correlated well with yields recorded in the field. Genotype-specific variation was observed for all traits measured and general trends spanning these sampling points were identified when trees were grouped by biomass yield. Nitrogen reserves in the cutting fuelled the entirety of the canopy establishment, yet earlier cessation of this dependency was linked to higher biomass yields. The stem was found to be the major N reserve by autumn, which constitutes a major source of N loss at harvest, typically every 2-3 years. These data contribute to understanding N remobilization in short rotation coppice willow and to the identification of traits that could potentially be selected for in breeding programmes to further improve the sustainability of biomass production.

  19. A new approach for the comparative analysis of multiprotein complexes based on 15N metabolic labeling and quantitative mass spectrometry.

    PubMed

    Trompelt, Kerstin; Steinbeck, Janina; Terashima, Mia; Hippler, Michael

    2014-01-01

    The introduced protocol provides a tool for the analysis of multiprotein complexes in the thylakoid membrane, by revealing insights into complex composition under different conditions. In this protocol the approach is demonstrated by comparing the composition of the protein complex responsible for cyclic electron flow (CEF) in Chlamydomonas reinhardtii, isolated from genetically different strains. The procedure comprises the isolation of thylakoid membranes, followed by their separation into multiprotein complexes by sucrose density gradient centrifugation, SDS-PAGE, immunodetection and comparative, quantitative mass spectrometry (MS) based on differential metabolic labeling ((14)N/(15)N) of the analyzed strains. Detergent solubilized thylakoid membranes are loaded on sucrose density gradients at equal chlorophyll concentration. After ultracentrifugation, the gradients are separated into fractions, which are analyzed by mass-spectrometry based on equal volume. This approach allows the investigation of the composition within the gradient fractions and moreover to analyze the migration behavior of different proteins, especially focusing on ANR1, CAS, and PGRL1. Furthermore, this method is demonstrated by confirming the results with immunoblotting and additionally by supporting the findings from previous studies (the identification and PSI-dependent migration of proteins that were previously described to be part of the CEF-supercomplex such as PGRL1, FNR, and cyt f). Notably, this approach is applicable to address a broad range of questions for which this protocol can be adopted and e.g. used for comparative analyses of multiprotein complex composition isolated from distinct environmental conditions. PMID:24686495

  20. Heavy water and 15N labeling with NanoSIMS analysis reveals growth-rate dependent metabolic heterogeneity in chemostats

    PubMed Central

    McGlynn, Shawn E.; Green-Saxena, Abigail

    2015-01-01

    To measure single cell microbial activity and substrate utilization patterns in environmental systems, we employ a new technique using stable isotope labeling of microbial populations with heavy water (a passive tracer) and 15N ammonium in combination with multi-isotope imaging mass spectrometry. We demonstrate simultaneous NanoSIMS analysis of hydrogen, carbon and nitrogen at high spatial and mass resolution, and report calibration data linking single cell isotopic compositions to the corresponding bulk isotopic equivalents for Pseudomonas aeruginosa and Staphylococcus aureus. Our results show that heavy water is capable of quantifying in situ single cell microbial activities ranging from generational time scales of minutes to years, with only light isotopic incorporation (∼0.1 atom % 2H). Applying this approach to study the rates of fatty acid biosynthesis by single cells of S. aureus growing at different rates in chemostat culture (∼6 hours, 1 day and 2 week generation times), we observe the greatest anabolic activity diversity in the slowest growing populations. By using heavy water to constrain cellular growth activity, we can further infer the relative contributions of ammonium vs. amino acid assimilation to the cellular nitrogen pool. The approach described here can be applied to disentangle individual cell activities even in nutritionally complex environments. PMID:25655651

  1. A solution NMR study of the selectively 13C, 15N-labeled peptaibol chrysospermin C in methanol.

    PubMed

    Anders, R; Wenschuh, H; Soskic, V; Fischer-Frühholz, S; Ohlenschläger, O; Dornberger, K; Brown, L R

    1998-07-01

    The conformation of the 19-residue peptaibol chrysospermin C in methanol has been investigated by NMR spectroscopy using selective 15N and 13C labeling of the alpha-aminoisobutyric acid (Aib) residues. Complete 1H and 13C sequential assignments, including stereospecific assignments for the heavily overlapped resonances from the two Cbeta methyl groups of the eight Aib residues, are reported for a peptaibol for the first time. An Aib residue followed by a Pro is an exception to previous suggestions regarding stereospecific assignment of the two Cbeta methyl groups of Aib residues. Local nuclear Overhauser effects and 3J(HNC') and 3J(HNCbeta) scalar couplings indicate that the phi angles of the Aib residues are restricted sterically to local conformations consistent with right-handed helices. Despite these constraints on the eight Aib residues, the NMR data for chrysospermin C in methanol are generally most consistent with an ensemble of transient conformations, including backbone conformations inconsistent with helical structures. Initial NMR measurements for chrysospermin C bound to micelles suggest structural and dynamic differences relative to alamethicin bound to micelles which may be related to differences in gating voltages for formation of ion channels.

  2. Interresidue carbonyl-carbonyl polarization transfer experiments in uniformly 13C,15N-labeled peptides and proteins.

    PubMed

    Janik, Rafal; Ritz, Emily; Gravelle, Andrew; Shi, Lichi; Peng, Xiaohu; Ladizhansky, Vladimir

    2010-03-01

    In this work, we demonstrate that Homonuclear Rotary Resonance Recoupling (HORROR) can be used to reintroduce carbonyl-carbonyl interresidue dipolar interactions and to achieve efficient polarization transfer between carbonyl atoms in uniformly (13)C,(15)N-labeled peptides and proteins. We show that the HORROR condition is anisotropically broadened and overall shifted to higher radio frequency intensities because of the CSA effects. These effects are analyzed theoretically using Average Hamiltonian Theory. At spinning frequencies used in this study, 22kHz, this broadening is experimentally found to be on the order of a kilohertz at a proton field of 600MHz. To match HORROR condition over all powder orientations, variable amplitude radio frequency (RF) fields are required, and efficient direct transfers on the order of 20-30% can be straightforwardly established. Two- and three-dimensional chemical shift correlation experiments establishing long-range interresidue connectivities (e.g., (N[i]-CO[i-2])) are demonstrated on the model peptide N-acetyl-valine-leucine, and on the third immunoglobulin binding domain of protein G. Possible future developments are discussed. PMID:20060344

  3. Metabolic labeling with stable isotope nitrogen (15N) to follow amino acid and protein turnover of three plastid proteins in Chlamydomonas reinhardtii

    PubMed Central

    2014-01-01

    Background The length of time that a protein remains available to perform its function is significantly influenced by its turnover rate. Knowing the turnover rate of proteins involved in different processes is important to determining how long a function might progress even when the stimulus has been removed and no further synthesis of the particular proteins occurs. In this article, we describe the use of 15N-metabolic labeling coupled to GC-MS to follow the turnover of free amino acids and LC-MS/MS to identify and LC-MS to follow the turnover of specific proteins in Chlamydomonas reinhardtii. Results To achieve the metabolic labeling, the growth medium was formulated with standard Tris acetate phosphate medium (TAP) in which14NH4Cl was replaced with 15NH415NO3 and (14NH4)6Mo7O24.4H2O was replaced with Na2MoO4.2H2O. This medium designated 15N-TAP allowed CC-125 algal cells to grow normally. Mass isotopic distribution revealed successful 15N incorporation into 13 amino acids with approximately 98% labeling efficiency. Tryptic digestion of the 55 kDa SDS-PAGE bands from 14N- and 15N-labeled crude algal protein extracts followed by LC-MS/MS resulted in the identification of 27 proteins. Of these, five displayed peptide sequence confidence levels greater than 95% and protein sequence coverage greater than 25%. These proteins were the RuBisCo large subunit, ATP synthase CF1 alpha and beta subunits, the mitochondrial protein (F1F0 ATP synthase) and the cytosolic protein (S-adenosyl homocysteine hydroxylase). These proteins were present in both labeled and unlabeled samples. Once the newly synthesized 15N-labeled free amino acids and proteins obtained maximum incorporation of the 15N-label, turnover rates were determined after transfer of cells into 14N-TAP medium. The t½ values were determined for the three plastid proteins (RuBisCo, ATP synthase CF1 alpha and beta) by following the reduction of the 15N-fractional abundance over time. Conclusion We describe a more

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-06-01

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

  6. Differential 14N/15N-Labeling of Peptides Using N-Terminal Charge Derivatization with a High-Proton Affinity for Straightforward de novo Peptide Sequencing

    PubMed Central

    Nihashi, Yoichiro; Miyashita, Masahiro; Awane, Hiroyuki; Miyagawa, Hisashi

    2013-01-01

    While de novo peptide sequencing is essential in many situations, it remains a difficult task. This is because peptide fragmentation results in complicated and often incomplete product ion spectra. In a previous study, we demonstrated that N-terminal charge derivatization with 4-amidinobenzoic acid (Aba) resulted in improved peptide fragmentation under low-energy CID conditions. However, even with this derivatization, some ambiguity exists, due to difficulties in discriminating between N- and C-terminal fragments. In this study, to specifically identify b-ions from complex product ion spectra, the differential 14N/15N-labeling of peptides was performed using Aba derivatization. 15N-Labeled Aba was synthesized in the form of a succinimide ester. Peptides were derivatized individually with 14N-Aba or 15N-Aba and analyzed by ESI-MS/MS using a linear ion trap-Orbitrap hybrid FTMS system. The N-terminal fragments (i.e., b-ions) were then identified based on m/z differences arising from isotope labeling. By comparing the spectra between 14N- and 15N-Aba derivatized peptides, b-ions could be successfully identified based on the m/z shifts, which provided reliable sequencing results for all of the peptides examined in this study. The method developed in this study allows the easy and reliable de novo sequencing of peptides, which is useful in peptidomics and proteomics studies. PMID:24860714

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    In Europe, the gastropod Crepidula fornicata is an invasive species characterized by a long reproductive period (from February to November). Thus, its larvae are exposed to variations in available food sources (in terms of quantity and quality). We aimed to investigate if bacteria could contribute to larval food both in presence or absence of phytoplankton, and to compare these results to seasonal variations of bacteria and phytoplankton abundances at a coastal site in the English Channel. First, ingestion of fluorescent beads of 0.5 to 2 μm 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‰ (∆δ13C) when supplied with diatoms, + 1364‰ (∆δ15N) when supplied with bacteria, and + 24‰ (∆δ13C) and + 135‰ (∆δ15N) 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

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

    SciTech Connect

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

    1994-12-01

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

  9. Artifact suppression in electron paramagnetic resonance imaging of 14N- and 15N-labeled nitroxyl radicals with asymmetric absorption spectra

    NASA Astrophysics Data System (ADS)

    Takahashi, Wataru; Miyake, Yusuke; Hirata, Hiroshi

    2014-10-01

    This article describes an improved method for suppressing image artifacts in the visualization of 14N- and 15N-labeled nitroxyl radicals in a single image scan using electron paramagnetic resonance (EPR). The purpose of this work was to solve the problem of asymmetric EPR absorption spectra in spectral processing. A hybrid function of Gaussian and Lorentzian lineshapes was used to perform spectral line-fitting to successfully separate the two kinds of nitroxyl radicals. This approach can process the asymmetric EPR absorption spectra of the nitroxyl radicals being measured, and can suppress image artifacts due to spectral asymmetry. With this improved visualization method and a 750-MHz continuous-wave EPR imager, a temporal change in the distributions of a two-phase paraffin oil and water/glycerin solution system was visualized using lipophilic and hydrophilic nitroxyl radicals, i.e., 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy (16-DOXYL stearic acid) and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-d17-1-15N-1-oxyl (TEMPOL-d17-15N). The results of the two-phase separation experiment verified that reasonable artifact suppression could be achieved by the present method that deals with asymmetric absorption spectra in the EPR imaging of 14N- and 15N-labeled nitroxyl radicals.

  10. Sensitivity-Enhanced MQ-HCN-CCH-TOCSY and MQ-HCN-CCH-COSY Pulse Schemes for 13C/ 15N Labeled RNA Oligonucleotides

    NASA Astrophysics Data System (ADS)

    Hu, Weidong; Jiang, Licong; Gosser, Yuying Q.

    2000-07-01

    Sensitivity enhanced multiple-quantum 3D HCN-CCH-TOCSY and HCN-CCH-COSY experiments are presented for the ribose resonance assignment of 13C/15N-labeled RNA sample. The experiments make use of the chemical shift dispersion of N1/N9 of pyrimidine/purine to distinguish the ribose spin systems. They provide a complementary approach for the assignment of ribose resonance to the currently used HCCH-COSY and HCCH-TOCSY type experiments in which either 13C or 1H is utilized to separate the different ribose spin systems. The pulse schemes have been demonstrated on a 23-mer 13C/15N-labeled RNA aptamer complexed with neomycin and tested on a 32-mer RNA complexed with a 23-residue peptide.

  11. HCN, A Triple-Resonance NMR Technique for Selective Observation of Histidine and Tryptophan Side Chains in 13C/ 15N-Labeled Proteins

    NASA Astrophysics Data System (ADS)

    Sudmeier, James L.; Ash, Elissa L.; Günther, Ulrich L.; Luo, Xuelian; Bullock, Peter A.; Bachovchin, William W.

    1996-12-01

    HCN, a new 3D NMR technique for stepwise coherence transfer from1H to13C to15N and reverse through direct spin couplings1JCHand1JCN, is presented as a method for detection and assignment of histidine and tryptophan side-chain1H,13C, and15N resonances in uniformly13C/15N-labeled proteins. Product-operator calculations of cross-peak volumes vs adjustable delay τ3were employed for determination of optimal τ3. For the phosphatidylinositol 3-kinase (PI3K SH3 domain, MW = 9.6 kD) at pH 6, H(C)N, the1H/15N projection, produced observable cross peaks within 20 min. and was completely selective for the single tryptophan and single histidine. The 3D HCN experiment yielded well-defined cross peaks in 20 h for the13C/15N-labeled origin-specific DNA binding domain from simian virus 40 T-antigen (T-ag-OBD131-259, MW = 15.4 kD) at pH 5.5. Resonances from all six histidines in T-ag-OBD were observed, and 11 of the 121H and13C chemical shifts and 10 of the 1215N chemical shifts were determined. The13C dimension proved essential in assignment of the multiply overlapping1H and15N resonances. From the spectra recorded at a single pH, three of the imidazoles were essentially neutral and the other three were partially protonated (22-37%). HCN yielded strong cross peaks after 18 h on a 2.0 mMsample of phenylmethanesulfonyl fluoride (PMSF)-inhibited α-lytic protease (MW = 19.8 kD) at pH 4.4. No spectra have been obtained, however, of native or boronic acid-inhibited α-lytic protease after 18 h at various temperatures ranging from 5 to 55°C, probably due to efficient relaxation of active-site imidazole1H and/or15N nuclei.

  12. An intraresidual i(HCA)CO(CA)NH experiment for the assignment of main-chain resonances in 15N, 13C labeled proteins.

    PubMed

    Mäntylahti, Sampo; Tossavainen, Helena; Hellman, Maarit; Permi, Perttu

    2009-11-01

    An improved pulse sequence, intraresidual i(HCA)CO(CA)NH, is described for establishing solely (13)C'(i), (15)N(i), (1)HN(i) connectivities in uniformly 15N/13C-labeled proteins. In comparison to the "out-and-back" style intra-HN(CA)CO experiment, the new pulse sequence offers at least two-fold higher experimental resolution in the (13)C' dimension and on average 1.6 times higher sensitivity especially for residues in alpha-helices. Performance of the new experiment was tested on a small globular protein ubiquitin and an intrinsically unfolded 110-residue cancer/testis antigen CT16/PAGE5. Use of intraresidual i(HCA)CO(CA)NH experiment in combination with the established HNCO experiment was crucial for the assignment of highly disordered CT16. PMID:19768387

  13. A new strategy for sequential assignment of intrinsically unstructured proteins based on 15N single isotope labelling

    NASA Astrophysics Data System (ADS)

    Lopez, Juan; Ahuja, Puneet; Gerard, Melanie; Wieruszeski, Jean-Michel; Lippens, Guy

    2013-11-01

    We describe a new efficient strategy for the sequential assignment of amide resonances of a conventional 15N-1H HSQC spectrum of intrinsically unfolded proteins, based on composite NOESY-TOCSY and TOCSY-NOESY mixing times. These composite mixing times lead to a Hα-proton mediated unidirectional transfer of amide to amide proton. We have implemented the composite mixing times in an HSQC-NOESY-HSQC manner to obtain directional connectivity between amides of neighbouring residues. We experimentally determine the optimal mixing times for both transfer schemes, and demonstrate its use in the assignment for both a fragment of the neuronal tau protein and for α-synuclein.

  14. Interactions of /sup 14/N:/sup 15/N stearic acid spin-label pairs: effects of host lipid alkyl chain length and unsaturation

    SciTech Connect

    Feix, J.B.; Yin, J.J.; Hyde, J.S.

    1987-06-30

    Electron-electron double resonance (ELDOR) and saturation recovery electron paramagnetic resonance (EPR) spectroscopy have been employed to examine the interactions of /sup 14/N:/sup 15/N stearic acid spin-label pairs in fluid-phase model membrane bilayers composed of a variety of phospholipids. The (/sup 14/N)-16-doxylstearate:(/sup 15/N)-16-doxylstearate (16:16) pair was utilized to measure lateral diffusion of the spin-labels, while the (/sup 14/N)-16-doxylstearate:(/sup 15/N)-5-doxylstearate (16:5) pair provided information on vertical fluctuations of the 16-doxylstearate nitroxide moiety toward the membrane surface. Three saturated host lipids of varying alkyl chain length (dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), and distearoylphosphatidylcholine (DSPC)), an ..cap alpha..-saturated, ..beta..-unsaturated lipid (1-palmitoyl-2-oleoylphosphatidylcholine (POPC)), and phosphatidylcholine from a natural source (egg yolk phosphatidylcholine (egg PC)) were utilized as host lipids. Lateral diffusion of the stearic acid spin-labels was only slightly affected by alkyl chain length at a given reduced temperature (T/sub r/) in the saturated host lipids but was significantly decreased in POPC at the same T/sub r/. Lateral diffusion in DMPC, POPC, and egg PC was quite similar at 37/sup 0/C. A strong correlation was noted between lateral diffusion constants and rotational mobility of (/sup 14/N)-16-doxylstearate. Vertical fluctuations were likewise only slightly influenced by alklyl chain length but were strongly diminished in POPC and egg PC relative to the saturated systems. This diminution of the 16:5 interaction was observed even under conditions where no differences were discernible by conventional EPR.

  15. Combining combing and secondary ion mass spectrometry to study DNA on chips using (13)C and (15)N labeling.

    PubMed

    Cabin-Flaman, Armelle; Monnier, Anne-Francoise; Coffinier, Yannick; Audinot, Jean-Nicolas; Gibouin, David; Wirtz, Tom; Boukherroub, Rabah; Migeon, Henri-Noël; Bensimon, Aaron; Jannière, Laurent; Ripoll, Camille; Norris, Victor

    2016-01-01

    Dynamic secondary ion mass spectrometry ( D-SIMS) imaging of combed DNA - the combing, imaging by SIMS or CIS method - has been developed previously using a standard NanoSIMS 50 to reveal, on the 50 nm scale, individual DNA fibers labeled with different, non-radioactive isotopes in vivo and to quantify these isotopes. This makes CIS especially suitable for determining the times, places and rates of DNA synthesis as well as the detection of the fine-scale re-arrangements of DNA and of molecules associated with combed DNA fibers. Here, we show how CIS may be extended to (13)C-labeling via the detection and quantification of the (13)C (14)N (-) recombinant ion and the use of the (13)C: (12)C ratio, we discuss how CIS might permit three successive labels, and we suggest ideas that might be explored using CIS. PMID:27429742

  16. Combining combing and secondary ion mass spectrometry to study DNA on chips using 13C and 15N labeling

    PubMed Central

    Cabin-Flaman, Armelle; Monnier, Anne-Francoise; Coffinier, Yannick; Audinot, Jean-Nicolas; Gibouin, David; Wirtz, Tom; Boukherroub, Rabah; Migeon, Henri-Noël; Bensimon, Aaron; Jannière, Laurent; Ripoll, Camille; Norris, Victor

    2016-01-01

    Dynamic secondary ion mass spectrometry ( D-SIMS) imaging of combed DNA – the combing, imaging by SIMS or CIS method – has been developed previously using a standard NanoSIMS 50 to reveal, on the 50 nm scale, individual DNA fibers labeled with different, non-radioactive isotopes in vivo and to quantify these isotopes. This makes CIS especially suitable for determining the times, places and rates of DNA synthesis as well as the detection of the fine-scale re-arrangements of DNA and of molecules associated with combed DNA fibers. Here, we show how CIS may be extended to 13C-labeling via the detection and quantification of the 13C 14N - recombinant ion and the use of the 13C: 12C ratio, we discuss how CIS might permit three successive labels, and we suggest ideas that might be explored using CIS. PMID:27429742

  17. Paramagnetic Inversion of the Sign of the Interference Contribution to the Transverse Relaxation of the Imido Protons of the Coordinated Imidazoles in the Uniformly 15N-Labeled Cytochrome c3

    NASA Astrophysics Data System (ADS)

    Ohmura, Tomoaki; Harada, Erisa; Fujiwara, Toshimichi; Kawai, Gota; Watanabe, Kimitsuna; Akutsu, Hideo

    1998-04-01

    In the spectrum of uniformly15N-labeled cytochromec3, the relative linewidths of the doublet peaks of the15N-coupled imido proton of the coordinated imidazole group were reversed on oxidation. This inversion was explained by the interference relaxation process between the electron-proton dipolar and15N-1H dipolar interactions. The inversion can be used to assign the imido protons of the coordinated imidazole groups in heme proteins.

  18. Selecting matched root architecture in tree pairs to be used for assessing N 2 fixation based on soil- 15N-labelling

    NASA Astrophysics Data System (ADS)

    Nasr, Hafedh; Ghorbel, Mohamed Habib; Wallander, Håkan; Dommergues, Yvon René

    2005-03-01

    It is commonly assumed that soil- 15N-labelling provides reliable estimates of N 2 fixation in trees by matching N 2-fixing and non-N 2-fixing tree pairs. As root system is a key parameter in determining suitability of the tree pairs, we compared root architecture of Acacia cyanophylla Lindl. and Casuarina glauca Sieber ex. Spreng. (two N 2-fixing trees) with Eucalyptus camaldulensis Dehn. and Ceratonia siliqua L. (two non-N 2-fixing trees) at 4-year-old in Mediterranean-semiarid zone. The rhizobium strain used appeared more motile than Frankia strain. A. cyanophylla and E. camaldulensis had extensive rooting area and volume of fine roots, and both species tended to develop marked horizontal rooting, compared to C. glauca and C. siliqua. Characteristics of fine- and horizontal-root components can be used in selecting matched root systems of N 2-fixing and reference-paired trees. Root architecture of C. glauca was more similar to C. siliqua, than to E. camaldulensis, and that of A. cyanophylla was more similar to E. camaldulensis than to C. siliqua. Accordingly, E. camaldulensis is an appropriate reference to estimate actual N 2 fixation by A. cyanophylla, and C. siliqua is an appropriate reference for C. glauca, when using soil- 15N-labelling method in the prevailing site environment.

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

    PubMed Central

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

    2012-01-01

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

  20. In vivo, large-scale preparation of uniformly (15)N- and site-specifically (13)C-labeled homogeneous, recombinant RNA for NMR studies.

    PubMed

    Le, My T; Brown, Rachel E; Simon, Anne E; Dayie, T Kwaku

    2015-01-01

    Knowledge of how ribonucleic acid (RNA) structures fold to form intricate, three-dimensional structures has provided fundamental insights into understanding the biological functions of RNA. Nuclear magnetic resonance (NMR) spectroscopy is a particularly useful high-resolution technique to investigate the dynamic structure of RNA. Effective study of RNA by NMR requires enrichment with isotopes of (13)C or (15)N or both. Here, we present a method to produce milligram quantities of uniformly (15)N- and site-specifically (13)C-labeled RNAs using wild-type K12 and mutant tktA Escherichia coli in combination with a tRNA-scaffold approach. The method includes a double selection protocol to obtain an E. coli clone with consistently high expression of the recombinant tRNA-scaffold. We also present protocols for the purification of the tRNA-scaffold from a total cellular RNA extract and the excision of the RNA of interest from the tRNA-scaffold using DNAzymes. Finally, we showcase NMR applications to demonstrate the benefit of using in vivo site-specifically (13)C-labeled RNA. PMID:26577743

  1. 13C- and 15N-Labeling Strategies Combined with Mass Spectrometry Comprehensively Quantify Phospholipid Dynamics in C. elegans

    PubMed Central

    Drechsler, Robin; Gafken, Philip R.; Olsen, Carissa Perez

    2015-01-01

    Membranes define cellular and organelle boundaries, a function that is critical to all living systems. Like other biomolecules, membrane lipids are dynamically maintained, but current methods are extremely limited for monitoring lipid dynamics in living animals. We developed novel strategies in C. elegans combining 13C and 15N stable isotopes with mass spectrometry to directly quantify the replenishment rates of the individual fatty acids and intact phospholipids of the membrane. Using multiple measurements of phospholipid dynamics, we found that the phospholipid pools are replaced rapidly and at rates nearly double the turnover measured for neutral lipid populations. In fact, our analysis shows that the majority of membrane lipids are replaced each day. Furthermore, we found that stearoyl-CoA desaturases (SCDs), critical enzymes in polyunsaturated fatty acid production, play an unexpected role in influencing the overall rates of membrane maintenance as SCD depletion affected the turnover of nearly all membrane lipids. Additionally, the compromised membrane maintenance as defined by LC-MS/MS with SCD RNAi resulted in active phospholipid remodeling that we predict is critical to alleviate the impact of reduced membrane maintenance in these animals. Not only have these combined methodologies identified new facets of the impact of SCDs on the membrane, but they also have great potential to reveal many undiscovered regulators of phospholipid metabolism. PMID:26528916

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  3. Multi-Isotope Secondary Ion Mass Spectrometry Combining Heavy Water 2H with 15N Labeling As Complementary Tracers for Metabolic Heterogeneity at the Single-Cell Level

    NASA Astrophysics Data System (ADS)

    Kopf, S.; McGlynn, S.; Cowley, E.; Green, A.; Newman, D. K.; Orphan, V. J.

    2014-12-01

    Metabolic rates of microbial communities constitute a key physiological parameter for understanding the in situ growth constraints for life in any environment. Isotope labeling techniques provide a powerful approach for measuring such biological activity, due to the use of isotopically enriched substrate tracers whose incorporation into biological materials can be detected with high sensitivity by isotope-ratio mass spectrometry. Nano-meter scale secondary ion mass spectrometry (NanoSIMS) combined with stable isotope labeling provides a unique tool for studying the spatiometabolic activity of microbial populations at the single cell level in order to assess both community structure and population diversity. However, assessing the distribution and range of microbial activity in complex environmental systems with slow-growing organisms, diverse carbon and nitrogen sources, or heterotrophic subpopulations poses a tremendous technical challenge because the introduction of isotopically labeled substrates frequently changes the nutrient availability and can inflate or bias measures of activity. Here, we present the use of hydrogen isotope labeling with deuterated water as an important new addition to the isotopic toolkit and apply it for the determination of single cell microbial activities by NanoSIMS imaging. This tool provides a labeling technique that minimally alters any aquatic chemical environment, can be administered with strong labels even in minimal addition (natural background is very low), is an equally universal substrate for all forms of life even in complex, carbon and nitrogen saturated systems, and can be combined with other isotopic tracers. The combination of heavy water labeling with the most commonly used NanoSIMS tracer, 15N, is technically challenging but opens up a powerful new set of multi-tracer experiments for the study of microbial activity in complex communities. We present the first truly simultaneous single cell triple isotope system

  4. NMR studies on /sup 15/N-labeled creatine (CR), creatinine (CRN), phosphocreatine (PCR), and phosphocreatinine (PCRN), and on barriers to rotation in creatine kinase-bound creatine in the enzymatic reaction

    SciTech Connect

    Kenyon, G.L.; Reddick, R.E.

    1986-05-01

    Recently, the authors have synthesized /sup 15/N-2-Cr, /sup 15/N-3-Crn, /sup 15/N-2-Crn, /sup 15/N-3-PCrn, /sup 15/N-3-PCr, and /sup 15/N-2-PCr. /sup 1/H, /sup 15/N, /sup 31/P NMR data show that Crn protonates exclusively at the non-methylated ring nitrogen, confirm that PCrn is phosphorylated at the exocyclic nitrogen, and demonstrate that the /sup 31/P-/sup 15/N one-bond coupling constant in /sup 15/N-3-PCr is 18 Hz, not 3 Hz as previously reported by Brindle, K.M., Porteous, R. and Radda, G.K.. The authors have found that creatine kinase is capable of catalyzing the /sup 14/N//sup 15/N positional isotope exchange of 3-/sup 15/N-PCr in the presence of MgADP, but not in its absence. Further, the exchange does not take place when labeled PCr is resynthesized exclusively from the ternary complex E X Cr X MgATP as opposed to either E X Cr or free Cr. This suggests that the enzyme both imparts an additional rotational barrier to creatine in the complex and catalyzes the transfer of phosphoryl group with essentially complete regiospecificity.

  5. Balancing the (carbon) budget: Using linear inverse models to estimate carbon flows and mass-balance 13C:15N labelling experiments in low oxygen sediments.

    NASA Astrophysics Data System (ADS)

    Hunter, William Ross; Van Oevelen, Dick; Witte, Ursula

    2013-04-01

    Over 1 million km2 of seafloor experience permanent low-oxygen conditions within oxygen minimum zones (OMZs). OMZs are predicted to grow as a consequence of climate change, potentially affecting oceanic biogeochemical cycles. The Arabian Sea OMZ impinges upon the western Indian continental margin at bathyal depths (150 - 1500m) producing a strong depth dependent oxygen gradient at the sea floor. The influence of the OMZ upon the short term processing of organic matter by sediment ecosystems was investigated using in situ stable isotope pulse chase experiments. These deployed doses of 13C:15N labeled organic matter onto the sediment surface at four stations from across the OMZ (water depth 540 - 1100 m; [O2] = 0.35 - 15 μM). In order to prevent experimentally anoxia, the mesocosms were not sealed. 13C and 15N labels were traced into sediment, bacteria, fauna and 13C into sediment porewater DIC and DOC. However, the DIC and DOC flux to the water column could not be measured, limiting our capacity to obtain mass-balance for C in each experimental mesocosm. Linear Inverse Modeling (LIM) provides a method to obtain a mass-balanced model of carbon flow that integrates stable-isotope tracer data with community biomass and biogeochemical flux data from a range of sources. Here we present an adaptation of the LIM methodology used to investigate how ecosystem structure influenced carbon flow across the Indian margin OMZ. We demonstrate how oxygen conditions affect food-web complexity, affecting the linkages between the bacteria, foraminifera and metazoan fauna, and their contributions to benthic respiration. The food-web models demonstrate how changes in ecosystem complexity are associated with oxygen availability across the OMZ and allow us to obtain a complete carbon budget for the stationa where stable-isotope labelling experiments were conducted.

  6. Estimation of internal and external nitrogen for corals with a long-term 15N-labelling experiment and subsequent model calculations

    NASA Astrophysics Data System (ADS)

    Tanaka, Yasuaki; Grottoli, Andréa; Matsui, Yohei; Suzuki, Atsushi; Sakai, Kazuhiko

    2014-05-01

    Coral reef ecosystems maintain high primary productivity though the seawater is extremely oligotrophic. One of the hypotheses to explain this paradox is the recycling of nutrients in animal-algal symbiotic organisms such as corals. It is relatively easy to measure nutrient uptake rates by corals from seawater, but the proportion of internally circulating nutrients between the coral host and the endosymbiotic algae (zooxanthellae) is more challenging. Here, we performed a long-term and continuous 15N-labelling experiment to quantify the proportionate contribution of seawater (external N source) and the animal host (internal N source) to the total N influx in the endosymbiotic algae. Branches from the scleractinian corals Porites cylindrica and Montipora digitata from Okinawa, Japan, were cultured for 2 months in indoor, flow-through, filtered seawater tanks with the continuous supply of 15N-labelled nitrate. At the initial and after 2, 4, and 9 weeks of the study, coral branches were collected and the algal and animal fractions were separated for isotopic analyses. In both corals, the N isotope ratio of symbiotic algae exponentially increased and the values were much higher than those of the host tissue, suggesting that the algae had a faster turnover N time than the animal host. Algal and host N biomass normalized to the coral surface area slowly decreased in both coral species over the study period. To calculate the contribution of internal and external N, a simple mixing model of algal N metabolism was designed. Using differential equations of 15N balance and N biomass balance, F1 and F2 (external and internal N fluxes to symbiotic algae, respectively) were expressed as the functions of time. The model calculations showed that F2 was much higher than F1 in P. cylindrica and the percentage of internal N to the total influx N (PIN) was >70%. On the other hand, the contribution of F1 and F2 was comparable in M. digitata and the PIN was 40-70%. These results

  7. H/D exchange of a 15N labelled Tau fragment as measured by a simple Relax-EXSY experiment

    NASA Astrophysics Data System (ADS)

    Lopez, Juan; Ahuja, Puneet; Landrieu, Isabelle; Cantrelle, François-Xavier; Huvent, Isabelle; Lippens, Guy

    2014-12-01

    We present an equilibrium H/D exchange experiment to measure the exchange rates of labile amide protons in intrinsically unfolded proteins. By measuring the contribution of the H/D exchange to the apparent T1 relaxation rates in solvents of different D2O content, we can easily derive the rates of exchange for rapidly exchanging amide protons. The method does not require double isotope labelling, is sensitive, and requires limited fitting of the data. We demonstrate it on a functional fragment of Tau, and provide evidence for the hydrogen bond formation of the phosphate moiety of Ser214 with its own amide proton in the same fragment phosphorylated by the PKA kinase.

  8. Restraints on backbone conformations in solid state NMR studies of uniformly labeled proteins from quantitative amide 15N–15N and carbonyl 13C–13C dipolar recoupling data

    PubMed Central

    Hu, Kan-Nian; Qiang, Wei; Bermejo, Guillermo A.; Schwieters, Charles D.; Tycko, Robert

    2013-01-01

    Recent structural studies of uniformly 15N, 13C-labeled proteins by solid state nuclear magnetic resonance (NMR) rely principally on two sources of structural restraints: (i) restraints on backbone conformation from isotropic 15N and 13C chemical shifts, based on empirical correlations between chemical shifts and backbone torsion angles; (ii) restraints on inter-residue proximities from qualitative measurements of internuclear dipole–dipole couplings, detected as the presence or absence of inter-residue crosspeaks in multidimensional spectra. We show that site-specific dipole–dipole couplings among 15N-labeled backbone amide sites and among 13C-labeled backbone carbonyl sites can be measured quantitatively in uniformly-labeled proteins, using dipolar recoupling techniques that we call 15N-BARE and 13C-BARE (BAckbone REcoupling), and that the resulting data represent a new source of restraints on backbone conformation. 15N-BARE and 13C-BARE data can be incorporated into structural modeling calculations as potential energy surfaces, which are derived from comparisons between experimental 15N and 13C signal decay curves, extracted from crosspeak intensities in series of two-dimensional spectra, with numerical simulations of the 15N-BARE and 13C-BARE measurements. We demonstrate this approach through experiments on microcrystalline, uniformly 15N, 13C-labeled protein GB1. Results for GB1 show that 15N-BARE and 13C-BARE restraints are complementary to restraints from chemical shifts and inter-residue crosspeaks, improving both the precision and the accuracy of calculated structures. PMID:22449573

  9. hnCOcaNH and hncoCANH pulse sequences for rapid and unambiguous backbone assignment in (13C, 15N) labeled proteins.

    PubMed

    Kumar, Dinesh; Reddy, Jithender G; Hosur, Ramakrishna V

    2010-09-01

    Time-saving in data acquisition is a major thrust of NMR pulse sequence development in the context of structural proteomics research. The conventional HNCA and HN(CA)CO pulse sequences, routinely used for sequential backbone assignment, have the limitation that they cannot distinguish inter- and intra-residue correlations. In order to remove this ambiguity, one has to record HNCO and HN(CO)CA or sequential HNCA experiments which provide unambiguous information of sequential correlations. However, this almost doubles the experimental time. Besides, they require repeated scanning through the (15)N planes to search for the matching peaks along the carbon dimension. In this background, we present here two pulse sequences, termed as hncoCANH and hnCOcaNH that lead to spectra equivalent to HNCA and HN(CA)CO spectra, respectively, but with direct distinction of inter- and intra-residue peaks; these occur with opposite signs in the new experiments. The two pulse sequences have been derived by simple modification of the previously described HN(C)N pulse sequence [Panchal et al., J. Biomol. NMR 20 (2001) 135-147] to frequency-label (13)C(alpha) or (13)C' instead of (15)N during the t(1) period. Like HN(C)N, these spectra also exhibit special patterns of self and sequential peaks around glycines and prolines, which enable direct identification of certain triplets of residues and thus provide internal checks during the sequential assignment walk. The spectra enable rapid and unambiguous assignment of H(N), (15)N and (13)C(alpha) (or (13)C') in a single experiment, and thus would be of great value in high-throughput structural proteomics. PMID:20643567

  10. Synthesis of 14N and 15N-labeled trityl-nitroxide biradicals with strong spin-spin interaction and improved sensitivity to redox status and oxygen

    PubMed Central

    Liu, Yangping; Villamena, Frederick A.; Song, Yuguang; Sun, Jian; Rockenbauer, Antal

    2014-01-01

    Simultaneous evaluation redox status and oxygenation in biological systems is of great importance for the understanding of biological functions. Electron paramagnetic resonance spectroscopy coupled with the use of the nitroxide radicals have been an indispensable technique for this application but are still limited by its low oxygen sensitivity, and low EPR resolution in part due to the moderately broad EPR triplet and spin quenching through bioreduction. In this study, we showed that these drawbacks can be overcome through the use of trityl-nitroxide biradicals allowing for the simultaneous measurement of redox status and oxygenation. A new trityl-nitroxide biradical TNN14 composed of a pyrrolidinyl-nitroxide and a trityl, and its isotopically labeled 15N analogue TNN15 were synthesized and characterized. Both biradicals exhibited much stronger spin-spin interaction with J > 400 G than the previous synthesized trityl-nitroxide biradicals TN1 (~160 G) and TN2 (~52 G) with longer linker chain length. The enhanced stability of TNN14 was evaluated using ascorbate as reductant and the effect of different types of cyclodextrins on its stability in the presence of ascorbate was also investigated. Both biradicals are sensitive to redox status, and their corresponding trityl-hydroxylamines resulting from the reduction of the biradicals by ascorbate share the same oxygen sensitivity. Of note is that the 15N-labeled TNN15-H with an EPR doublet exhibits improved EPR signal amplitude as compared to TNN14-H with an EPR triplet. In addition, cyclic voltammetric studies verify the characteristic electrochemical behaviors of the trityl-nitroxide biradicals. PMID:21028905

  11. Three-Dimensional Solid-State NMR Spectroscopy Is Essential for Resolution of Resonances from In-Plane Residues in Uniformly 15N-Labeled Helical Membrane Proteins in Oriented Lipid Bilayers

    NASA Astrophysics Data System (ADS)

    Marassi, Francesca M.; Ma, Che; Gesell, Jennifer J.; Opella, Stanley J.

    2000-05-01

    Uniformly 15N-labeled samples of membrane proteins with helices aligned parallel to the membrane surface give two-dimensional PISEMA spectra that are highly overlapped due to limited dispersions of 1H-15N dipolar coupling and 15N chemical shift frequencies. However, resolution is greatly improved in three-dimensional 1H chemical shift/1H-15N dipolar coupling/15N chemical shift correlation spectra. The 23-residue antibiotic peptide magainin and a 54-residue polypeptide corresponding to the cytoplasmic domain of the HIV-1 accessory protein Vpu are used as examples. Both polypeptides consist almost entirely of α-helices, with their axes aligned parallel to the membrane surface. The measurement of three orientationally dependent frequencies for Val17 of magainin enabled the three-dimensional orientation of this helical peptide to be determined in the lipid bilayer.

  12. Use of a novel nitrification inhibitor to reduce nitrous oxide emission from (15)N-labelled dairy slurry injected into soil.

    PubMed

    Dittert, K; Bol, R; King, R; Chadwick, D; Hatch, D

    2001-01-01

    Recent recommendations for environmentally sound use of liquid animal manure often include injection of slurry into soil. Two of the most important undesired side effects, ammonia (NH(3)) volatilisation and odour emissions, are usually significantly reduced by slurry injection. On the other hand, because of the higher amount of nitrogen (N) remaining in soil, the risk of nitrate (NO(3)(-)) leaching and nitrous oxide (N(2)O) emissions is increased. Thus, the reduction of local effects caused by NH(3) deposition, e.g. N enrichment and soil acidification, may be at the cost of large-scale effects such as ozone depletion and global warming as a result of emitted N(2)O. In this context, nitrification inhibitors can contribute significantly to a reduction in NO(3)(-) leaching and N(2)O production. A field experiment was carried out at IGER, North Wyke, which aimed to evaluate the effect of the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP/ENTEC). For this experiment, (15)N enriched dairy slurry was used and the isotopic label in soil N as well as in N(2)O were studied. After slurry injection into the grassland soil in August 2000, the major emissions of N(2)O occurred during the first ten days. As expected, high N(2)O emission rates and (15)N content of the emissions were concentrated on the slurry injection slots, showing a steep decrease towards the untreated centre-point between slurry injection slots. The nitrification inhibitor DMPP proved to be very efficient in reducing N(2)O emissions. At a rate of 2 kg DMPP ha(-1), the total amount of N(2)O emitted was reduced by 32%, when compared with slurry injection without DMPP. The isotopic label of the emitted N(2)O showed that during the 22-day experimental period, emissions from the slurry N pool were strongly reduced by DMPP from 0.93 kg N(2)O-N ha(-1) (-DMPP) to 0.50 kg N(2)O-N ha(-1) (+DMPP), while only a minor effect on emissions from the soil N pool was observed (0.69 to 0.60 kg N(2)O-N ha(-1

  13. Dynamics of exogenous nitrogen partitioning and nitrogen remobilization from vegetative organs in pea revealed by 15N in vivo labeling throughout seed filling.

    PubMed

    Schiltz, Séverine; Munier-Jolain, Nathalie; Jeudy, Christian; Burstin, Judith; Salon, Christophe

    2005-04-01

    The fluxes of (1) exogenous nitrogen (N) assimilation and (2) remobilization of endogenous N from vegetative plant compartments were measured by 15N labeling during the seed-filling period in pea (Pisum sativum L. cv Cameor), to better understand the mechanism of N remobilization. While the majority (86%) of exogenous N was allocated to the vegetative organs before the beginning of seed filling, this fraction decreased to 45% at the onset of seed filling, the remainder being directed to seeds. Nitrogen remobilization from vegetative parts contributed to 71% of the total N in mature seeds borne on the first two nodes (first stratum). The contribution of remobilized N to total seed N varied, with the highest proportion at the beginning of filling; it was independent of the developmental stage of each stratum of seeds, suggesting that remobilized N forms a unique pool, managed at the whole-plant level and supplied to all filling seeds whatever their position on the plant. Once seed filling starts, N is remobilized from all vegetative organs: 30% of the total N accumulated in seeds was remobilized from leaves, 20% from pod walls, 11% from roots, and 10% from stems. The rate of N remobilization was maximal when seeds of all the different strata were filling, consistent with regulation according to the N demand of seeds. At later stages of seed filling, the rate of remobilization decreases and may become controlled by the amount of residual N in vegetative tissues.

  14. Site-specific protein backbone and side-chain NMR chemical shift and relaxation analysis of human vinexin SH3 domain using a genetically encoded {sup 15}N/{sup 19}F-labeled unnatural amino acid

    SciTech Connect

    Shi, Pan; Xi, Zhaoyong; Wang, Hu; Shi, Chaowei; Xiong, Ying; Tian, Changlin

    2010-11-19

    Research highlights: {yields} Chemical synthesis of {sup 15}N/{sup 19}F-trifluomethyl phenylalanine. {yields} Site-specific incorporation of {sup 15}N/{sup 19}F-trifluomethyl phenylalanine to SH3. {yields} Site-specific backbone and side chain chemical shift and relaxation analysis. {yields} Different internal motions at different sites of SH3 domain upon ligand binding. -- Abstract: SH3 is a ubiquitous domain mediating protein-protein interactions. Recent solution NMR structural studies have shown that a proline-rich peptide is capable of binding to the human vinexin SH3 domain. Here, an orthogonal amber tRNA/tRNA synthetase pair for {sup 15}N/{sup 19}F-trifluoromethyl-phenylalanine ({sup 15}N/{sup 19}F-tfmF) has been applied to achieve site-specific labeling of SH3 at three different sites. One-dimensional solution NMR spectra of backbone amide ({sup 15}N){sup 1}H and side-chain {sup 19}F were obtained for SH3 with three different site-specific labels. Site-specific backbone amide ({sup 15}N){sup 1}H and side-chain {sup 19}F chemical shift and relaxation analysis of SH3 in the absence or presence of a peptide ligand demonstrated different internal motions upon ligand binding at the three different sites. This site-specific NMR analysis might be very useful for studying large-sized proteins or protein complexes.

  15. Selective observation of biologically important 15N-labeled metabolites in isolated rat brain and liver by 1H-detected multiple-quantum-coherence spectroscopy

    NASA Astrophysics Data System (ADS)

    Kanamori, Keiko; Ross, Brian D.; Parivar, Farhad

    Four cerebral metabolites of importance in neurotransmission, serotonin, L-tryptophan, L-glutamine, and N-acetyl- L-aspartate, and two hepatic urea-cycle intermediates, citrulline and urea, were found to be observable by 1H- 15N heteronuclear multiple-quantum-coherence (HMQC) spectroscopy in aqueous solution at physiological pH and temperature, through the protons spin-coupled to their indole, amide, or ureido nitrogen. Their 1H chemical shifts were well dispersed over a 5-10 ppm region while the 1J 15N- 1H values were 87-99 Hz. For [γ- 15N]glutamine, a 50- to 100-fold increase in sensitivity over direct 15N detection was achieved, in contrast to a 2-fold increase by the polarization-transfer method. In the isolated brain of portacaval-shunted rats, the amide protons of biologically 15N-enriched [γ- 15N]glutamine were observed in 2 min of acquisition, with suppression of proton signals from all other cerebral metabolites. In isolated liver of 15N-enriched control rats, [ 15NIurea protons were observed in 16 min. The HMQC method is likely to be effective for the in vivo study of cerebral and hepatic nitrogen metabolism.

  16. Microarthropods accelerate litter decomposition and alter the fate of litter carbon and nitrogen in the soil

    NASA Astrophysics Data System (ADS)

    Soong, Jennifer; Horton, Andrew; Wall, Diana; Cotrufo, Francesca

    2015-04-01

    Soil fauna have been found to accelerate litter decomposition in some ecosystems, with calls for the need to include them in global models of C and N cycling. However, their influence on the fate of decomposing litter C and N is not clear. Does the acceleration of mass loss affect how much litter C and N end up stored as soil organic matter (SOM), or how much C and N are lost to the atmosphere during decomposition? We will present the results from our three-year, 100% mass loss, tracking of 13C and 15N labeled Andropogon gerardii leaf litter decomposing at a tallgrass prairie site, where we used a naphthalene treatment to suppress microarthropods and examine their effects on the fate of decomposing litter C and N. Initially, leaching was the main pathway of litter inputs to the mineral associated SOM. We found that microarthropods accelerated the first 18 months of litter mass loss, but after 24 months mass loss rates converged. This early acceleration of mass loss was associated with an increase of litter fragment inputs to the soil. This increase in litter inputs to the soil caused by microarthropods resulted in an increase in microbial uptake of litter C (measured by tracing 13C into phospholipid fatty acids), and a shift in the microbial community. The C:N ratio of litter inputs to the soil was significantly increased by the presence of microarthropods. Together these results demonstrate how microarthropods accelerate shredding, mass loss, and litter fragment inputs to the soil during the early stages of decomposition but they do not affect the total amount of litter contribution to SOM over the entire course of decomposition. However, microarthropods do alter the C:N composition of litter inputs to the soil through their top-down influence on the microbial community responsible for decomposing and transforming litter inputs to the soil. Our results reveal the complex interactions between microarthropods, litter mass loss, soil microbes and C:N dynamics, and

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  18. 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.

  19. Nitrous oxide emissions from in situ deposition of N-labeled ryegrass litter in a pasture soil.

    PubMed

    Pal, Pranoy; Clough, Tim J; Kelliher, Francis M; Sherlock, Robert R

    2013-01-01

    During pasture grazing, freshly harvested herbage (litterfall) is dropped onto soils from the mouths of dairy cattle, potentially inducing nitrous oxide (NO) emissions. Although the Intergovernmental Panel on Climate Change (IPCC) recommends accounting for NO emissions from arable crop residues in national inventories, emissions from the litterfall of grazed pasture systems are not recognized. The objective of this study was to investigate the potential of litterfall to contribute to NO emissions in a field study located on a pasture site in Canterbury, New Zealand (43°38.50' S, 172°27.17' E). We applied N-labeled perennial ryegrass ( L.) to the surface of a pastoral soil (Temuka clay loam) and, for up to 139 d thereafter, quantified the contribution of herbage decomposition to NO production and soil N dynamics. Litterfall contributed to the N enrichment of soil NO-N and NO-N pools. After 49 d, N recovery as NO equated to 0.93% of the surface-applied litter N, with 38 to 75% of the cumulative NO flux occurring within 4 to 10 d of treatment application. Emissions of NO likely resulted from ammonification followed by a coupling of nitrification and denitrification during litter decomposition on the soil surface. The emission factor of the litter deposited in situ was 1.2 ± 0.2%, which is not substantially greater than the IPCC default emission factor value of 1% for crop residues. Further in situ studies using different pasture species and litterfall rates are required to understand the microbial processes responsible for litter-induced NO emissions.

  20. Effect of 15 N Labeled Riparian Fertilization And Salmon Carcass Analog Addition On Food Web Dynamics And Productivity In Four Idaho Streams

    NASA Astrophysics Data System (ADS)

    Rugenski, A. T.; Kohler, A.; Minshall, G. W.; Danehy, R. J.; Taki, D.

    2005-05-01

    Nutrient budgets of stream/riparian ecosystems in the Intermountain West have been depleted through declining salmon populations and certain anthropogenic disturbances (e.g. forestry practices). We measured stream food web responses to a riparian fertilization and an in-stream carcass analog addition in 4 Idaho streams with a 15 N tracer. Aerial application of fertilizer pellets to light (224 kg/ha) and heavy (448 kg/ha) treatment sections of 2 streams and carcass analog additions to 2 others were completed in autumn. Periphyton response was measured through chlorophyll a, nutrient diffusing substrata, and stable isotope analyses. Macroinvertebrates were analyzed for abundance, biomass, community structure, and stable isotope composition. Also, willow (Salix) breakdown rates were determined. Pre-treatment chlorophyll a values showed no significant difference between treatment and reference reaches. Post-treatment results showed significantly higher chlorophyll a and δ 15 N values in treatment reaches compared to reference reaches. Macroinvertebrate abundance, richness, biomass, and δ 15 N values also increased in treated reaches. No significant differences were detected in leaf breakdown rates between reaches. Riparian fertilization effects were longer lasting than the in-stream treatment. These results suggest that nutrient addition to streams and riparian areas can be used as a management tool to increase stream productivity where nutrients are limiting.

  1. Measurement of 13C and 15N isotope labeling by gas chromatography/combustion/isotope ratio mass spectrometry to study amino acid fluxes in a plant-microbe symbiotic association.

    PubMed

    Molero, Gemma; Aranjuelo, Iker; Teixidor, Pilar; Araus, José Luis; Nogués, Salvador

    2011-03-15

    We have developed a method based on a double labeling with stable isotopes and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analyses to study amino acid exchange in a symbiotic plant-microbe association. Isotopic precision was studied for 21 standards including 15 amino acid derivatives, three N-protected amino acid methyl esters, three amines and one international standard. High correlations were observed between the δ(13)C and δ(15)N values obtained by GC/C/IRMS and those obtained by an elemental analyzer (EA) coupled to an isotope ratio mass spectrometer (R(2) = 0.9868 and 0.9992, respectively). The mean precision measured was 0.04‰ for δ(13)C and 0.28‰ for δ(15)N (n = 15). This method was applied in vivo to the symbiotic relationship between alfalfa (Medicago sativa L.) and N(2)-fixing bacteria. Plants were simultaneously labeled over 10 days with (13)C-depleted CO(2) ((12)CO(2)), which was assimilated through photosynthesis by leaves, and (15)N(2) fixed via nodules. Subsequently, the C and N isotope compositions (i.e. δ(13)C and δ(15)N) of free amino acids were analyzed in leaves and nodules by GC/C/IRMS. The method revealed the pattern of C and N exchange between leaves and nodules, highlighting that γ-aminobutanoic acid and glycine may represent an important form of C transport from leaves to the nodules. The results confirmed the validity, reliability and accuracy of the method for assessing C and N fluxes between plants and symbiotic bacteria and support the use of this technique in a broad range of metabolic and fluxomic studies.

  2. The fates of 15N-labeled fertilizer in a wheat–soil system as influenced by fertilization practice in a loamy soil

    NASA Astrophysics Data System (ADS)

    Chen, Zhaoming; Wang, Huoyan; Liu, Xiaowei; Lu, Dianjun; Zhou, Jianmin

    2016-10-01

    Appropriate fertilization practice is crucial to achieve maximum wheat grain yield with minimum nitrogen (N) loss. A field 15N micro-plot experiment was conducted to determine the effects of application methods [split application (SA) and band application (BA)] and N rates (60, 150 and 240 kg ha‑1) on the wheat grain yield, urea-15N fate and N efficiency in Jiangyan County, China. At high N rates, wheat grain yield was significantly higher for SA than BA treatment, but there was no difference at the lower N rates. Plant N derived from fertilizer was higher in SA than in BA treatment. The high N fertilizer application increased total N uptake by wheat derived from fertilizer, but wheat plant N derived from soil was not affected by the N rate. Fertilizer-N recovery in SA treatment was higher than in BA treatment. Residual N recovery in the 0–80 cm soil layer was 31–51%, which decreased with increasing N rate. The highest N loss was found for BA treatment at the N application of 240 kg ha‑1. The one-time BA of N fertilizer, especially for higher N rates, led to reduced wheat grain yield and N efficiency, and increased the N loss.

  3. The fates of 15N-labeled fertilizer in a wheat–soil system as influenced by fertilization practice in a loamy soil

    PubMed Central

    Chen, Zhaoming; Wang, Huoyan; Liu, Xiaowei; Lu, Dianjun; Zhou, Jianmin

    2016-01-01

    Appropriate fertilization practice is crucial to achieve maximum wheat grain yield with minimum nitrogen (N) loss. A field 15N micro-plot experiment was conducted to determine the effects of application methods [split application (SA) and band application (BA)] and N rates (60, 150 and 240 kg ha−1) on the wheat grain yield, urea-15N fate and N efficiency in Jiangyan County, China. At high N rates, wheat grain yield was significantly higher for SA than BA treatment, but there was no difference at the lower N rates. Plant N derived from fertilizer was higher in SA than in BA treatment. The high N fertilizer application increased total N uptake by wheat derived from fertilizer, but wheat plant N derived from soil was not affected by the N rate. Fertilizer-N recovery in SA treatment was higher than in BA treatment. Residual N recovery in the 0–80 cm soil layer was 31–51%, which decreased with increasing N rate. The highest N loss was found for BA treatment at the N application of 240 kg ha−1. The one-time BA of N fertilizer, especially for higher N rates, led to reduced wheat grain yield and N efficiency, and increased the N loss. PMID:27713476

  4. 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; Brümmer, 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 µg 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 µg 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

  5. Plasma free amino acid kinetics in rainbow trout (Oncorhynchus mykiss) using a bolus injection of 15N-labeled amino acids.

    PubMed

    Robinson, Jacob William; Yanke, Dan; Mirza, Jeff; Ballantyne, James Stuart

    2011-02-01

    To gain insight into the metabolic design of the amino acid carrier systems in fish, we injected a bolus of (15)N amino acids into the dorsal aorta in mature rainbow trout (Oncorhynchus mykiss). The plasma kinetic parameters including concentration, pool size, rate of disappearance (R(d)), half-life and turnover rate were determined for 15 amino acids. When corrected for metabolic rate, the R(d) values obtained for trout for most amino acids were largely comparable to human values, with the exception of glutamine (which was lower) and threonine (which was higher). R(d) values ranged from 0.9 μmol 100 g(-1) h(-1) (lysine) to 22.1 μmol 100 g(-1) h(-1) (threonine) with most values falling between 2 and 6 μmol 100 g(-1) h(-1). There was a significant correlation between R(d) and the molar proportion of amino acids in rainbow trout whole body protein hydrolysate. Other kinetic parameters did not correlate significantly with whole body amino acid composition. This indicates that an important design feature of the plasma-free amino acids system involves proportional delivery of amino acids to tissues for protein synthesis.

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

    PubMed

    Bayer, A; Freund, S; Jung, G

    1995-12-01

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

  7. Measurement of 1J(Ni,Calpha(i)), 1J(Ni,C'i-1), 2J(Ni,Calpha(i-1)), 2J(H(N)i,C'i-1) and 2J(H(N)i,Calpha(i)) values in 13C/15N-labeled proteins.

    PubMed

    Mukherjee, Sulakshana; Mustafi, Sourajit M; Atreya, H S; Chary, K V R

    2005-04-01

    Use of partial or selective (13)C/(15)N labeling of specific amino acid residues in a given protein to measure the values of (1)J((15)N(i),(13)C(alpha) (i)), (2)J((1)H(N),(13)C(alpha) (i)), (2)J((15)N(i),(13)C(alpha) (i-1)), (1)J((15)N(i),(13)C'(i-1)) and (2)J((1)H(N),(13)C'(i-1)) is described. This was achieved by recording a sensitivity-enhanced 2D [(15)N-(1)H] HSQC experiment, without mixing the spin states of C(alpha) and C' during the course of entire experiment.

  8. NMR studies of active-site properties of human carbonic anhydrase II by using (15) N-labeled 4-methylimidazole as a local probe and histidine hydrogen-bond correlations.

    PubMed

    Shenderovich, Ilya G; Lesnichin, Stepan B; Tu, Chingkuang; Silverman, David N; Tolstoy, Peter M; Denisov, Gleb S; Limbach, Hans-Heinrich

    2015-02-01

    By using a combination of liquid and solid-state NMR spectroscopy, (15) N-labeled 4-methylimidazole (4-MI) as a local probe of the environment has been studied: 1) in the polar, wet Freon CDF3 /CDF2 Cl down to 130 K, 2) in water at pH 12, and 3) in solid samples of the mutant H64A of human carbonic anhydrase II (HCA II). In the latter, the active-site His64 residue is replaced by alanine; the catalytic activity is, however, rescued by the presence of 4-MI. For the Freon solution, it is demonstrated that addition of water molecules not only catalyzes proton tautomerism but also lifts its quasidegeneracy. The possible hydrogen-bond clusters formed and the mechanism of the tautomerism are discussed. Information about the imidazole hydrogen-bond geometries is obtained by establishing a correlation between published (1) H and (15) N chemical shifts of the imidazole rings of histidines in proteins. This correlation is useful to distinguish histidines embedded in the interior of proteins and those at the surface, embedded in water. Moreover, evidence is obtained that the hydrogen-bond geometries of His64 in the active site of HCA II and of 4-MI in H64A HCA II are similar. Finally, the degeneracy of the rapid tautomerism of the neutral imidazole ring His64 reported by Shimahara et al. (J. Biol. Chem.- 2007, 282, 9646) can be explained with a wet, polar, nonaqueous active-site conformation in the inward conformation, similar to the properties of 4-MI in the Freon solution. The biological implications for the enzyme mechanism are discussed. PMID:25521423

  9. NMR studies of active-site properties of human carbonic anhydrase II by using (15) N-labeled 4-methylimidazole as a local probe and histidine hydrogen-bond correlations.

    PubMed

    Shenderovich, Ilya G; Lesnichin, Stepan B; Tu, Chingkuang; Silverman, David N; Tolstoy, Peter M; Denisov, Gleb S; Limbach, Hans-Heinrich

    2015-02-01

    By using a combination of liquid and solid-state NMR spectroscopy, (15) N-labeled 4-methylimidazole (4-MI) as a local probe of the environment has been studied: 1) in the polar, wet Freon CDF3 /CDF2 Cl down to 130 K, 2) in water at pH 12, and 3) in solid samples of the mutant H64A of human carbonic anhydrase II (HCA II). In the latter, the active-site His64 residue is replaced by alanine; the catalytic activity is, however, rescued by the presence of 4-MI. For the Freon solution, it is demonstrated that addition of water molecules not only catalyzes proton tautomerism but also lifts its quasidegeneracy. The possible hydrogen-bond clusters formed and the mechanism of the tautomerism are discussed. Information about the imidazole hydrogen-bond geometries is obtained by establishing a correlation between published (1) H and (15) N chemical shifts of the imidazole rings of histidines in proteins. This correlation is useful to distinguish histidines embedded in the interior of proteins and those at the surface, embedded in water. Moreover, evidence is obtained that the hydrogen-bond geometries of His64 in the active site of HCA II and of 4-MI in H64A HCA II are similar. Finally, the degeneracy of the rapid tautomerism of the neutral imidazole ring His64 reported by Shimahara et al. (J. Biol. Chem.- 2007, 282, 9646) can be explained with a wet, polar, nonaqueous active-site conformation in the inward conformation, similar to the properties of 4-MI in the Freon solution. The biological implications for the enzyme mechanism are discussed.

  10. Quantitative Shotgun Proteomics Using a Uniform 15N-Labeled Standard to Monitor Proteome Dynamics in Time Course Experiments Reveals New Insights into the Heat Stress Response of Chlamydomonas reinhardtii*

    PubMed Central

    Mühlhaus, Timo; Weiss, Julia; Hemme, Dorothea; Sommer, Frederik; Schroda, Michael

    2011-01-01

    Crop-plant-yield safety is jeopardized by temperature stress caused by the global climate change. To take countermeasures by breeding and/or transgenic approaches it is essential to understand the mechanisms underlying plant acclimation to heat stress. To this end proteomics approaches are most promising, as acclimation is largely mediated by proteins. Accordingly, several proteomics studies, mainly based on two-dimensional gel-tandem MS approaches, were conducted in the past. However, results often were inconsistent, presumably attributable to artifacts inherent to the display of complex proteomes via two-dimensional-gels. We describe here a new approach to monitor proteome dynamics in time course experiments. This approach involves full 15N metabolic labeling and mass spectrometry based quantitative shotgun proteomics using a uniform 15N standard over all time points. It comprises a software framework, IOMIQS, that features batch job mediated automated peptide identification by four parallelized search engines, peptide quantification and data assembly for the processing of large numbers of samples. We have applied this approach to monitor proteome dynamics in a heat stress time course using the unicellular green alga Chlamydomonas reinhardtii as model system. We were able to identify 3433 Chlamydomonas proteins, of which 1116 were quantified in at least three of five time points of the time course. Statistical analyses revealed that levels of 38 proteins significantly increased, whereas levels of 206 proteins significantly decreased during heat stress. The increasing proteins comprise 25 (co-)chaperones and 13 proteins involved in chromatin remodeling, signal transduction, apoptosis, photosynthetic light reactions, and yet unknown functions. Proteins decreasing during heat stress were significantly enriched in functional categories that mediate carbon flux from CO2 and external acetate into protein biosynthesis, which also correlated with a rapid, but fully

  11. SIMS ion microscopy imaging of boronophenylalanine (BPA) and 13C15N-labeled phenylalanine in human glioblastoma cells: Relevance of subcellular scale observations to BPA-mediated boron neutron capture therapy of cancer

    NASA Astrophysics Data System (ADS)

    Chandra, Subhash; Lorey, Daniel R., II

    2007-02-01

    p-Boronophenylalanine (BPA) is a clinically approved boron neutron capture therapy (BNCT) agent currently being used in clinical trials of glioblastoma multiforme, melanoma and liver metastases. Secondary ion mass spectrometry (SIMS) observations from the Cornell SIMS Laboratory provided support for using a 6 h infusion of BPA, instead of a 2 h infusion, for achieving higher levels of boron in brain tumor cells. These observations were clinically implemented in Phase II experimental trials of glioblastoma multiforme in Sweden. However, the mechanisms for higher BPA accumulation with longer infusions have remained unknown. In this work, by using 13C15N-labeled phenylalanine and T98G human glioblastoma cells, comparisons between the 10B-delivery of BPA and the accumulation of labeled phenylalanine after 2 and 6 h treatments were made with a Cameca IMS-3f SIMS ion microscope at 500 nm spatial resolution in fast frozen, freeze-fractured, freeze-dried cells. Due to the presence of the Na-K-ATPase in the plasma membrane of most mammalian cells, the cells maintain an approximately 10/1 ratio of K/Na in the intracellular milieu. Therefore, the quantitative imaging of these highly diffusible species in the identical cell in which the boron or labeled amino acid was imaged provides a rule-of-thumb criterion for validation of SIMS observations and the reliability of the cryogenic sampling. The labeled phenylalanine was detected at mass 28, as the 28(13C15N)- molecular ion. Correlative analysis with optical and confocal laser scanning microscopy revealed that fractured freeze-dried glioblastoma cells contained well-preserved ultrastructural details with three discernible subcellular regions: a nucleus or multiple nuclei, a mitochondria-rich perinuclear cytoplasmic region and the remaining cytoplasm. SIMS analysis revealed that the overall cellular signals of both 10B from BPA and 28CN- from labeled phenylalanine increased approximately 1.6-fold between the 2 and 6 h exposures

  12. Release of PCDD/PCDF to air and land during open burning of sugarcane and forest litter over soil fortified with mass labelled PCDD/PCDF

    NASA Astrophysics Data System (ADS)

    Black, Robert R.; (Mick) Meyer, Carl P.; Yates, Alan; Van Zwieten, Lukas; Chittim, Brock G.; Mueller, Jochen F.

    2012-11-01

    The contribution of PCDD/PCDF emissions from soil during open burning of biomass was examined. Mass labelled PCDD/PCDF was added to soil containing native PCDD/PCDF and biomass was laid out on this soil and burnt, simulating sugarcane trash and forest fires. Smoke samples were collected using a high volume portable field sampler. After each fire the concentration of all mass labelled PCDD/PCDF congeners in the surface soil decreased, however, the concentration of some native 2,3,7,8 substituted congeners increased, indicating that formation was occurring. Mass labelled PCDD/PCDF congeners were detected in all ash samples, mean 2.8 pg g-1 (range 0.5-8 pg g-1), demonstrating release from the soil. Additionally, mass labelled PCDD/PCDF congeners were detected in all air samples mean 1.2 μg (t fuel)-1 (range 0.2-2.0 μg (t fuel)-1), again demonstrating release from the soil. Native 2,3,7,8 substituted congeners detected in the air samples were dominated (in terms of contribution to total congener mass) by Cl8DD (90% for forest litter and 77% for sugarcane). The major contributor to TEQ of emissions from both forest litter and sugarcane was 1, 2, 3, 7, 8-Cl5DD (40-64% and 57-75%, respectively). These results demonstrate that release of PCDD/PCDF from soil to air and land occurs during open burning of biomass when soil temperatures are sufficiently elevated.

  13. Robust method for investigating nitrogen metabolism of 15N labeled amino acids using AccQ•Tag ultra performance liquid chromatography-photodiode array-electrospray ionization-mass spectrometry: application to a parasitic plant-plant interaction.

    PubMed

    Gaudin, Zachary; Cerveau, Delphine; Marnet, Nathalie; Bouchereau, Alain; Delavault, Philippe; Simier, Philippe; Pouvreau, Jean-Bernard

    2014-01-21

    An AccQ•Tag ultra performance liquid chromatography-photodiode array-electrospray ionization-mass spectrometry (AccQ•Tag-UPLC-PDA-ESI-MS) method is presented here for the fast, robust, and sensitive quantification of (15)N isotopologue enrichment of amino acids in biological samples, as for example in the special biotic interaction between the cultivated specie Brassica napus (rapeseed) and the parasitic weed Phelipanche ramosa (broomrape). This method was developed and validated using amino acid standard solutions containing (15)N amino acid isotopologues and/or biological unlabeled extracts. Apparatus optimization, limits of detection and quantification, quantification reproducibility, and calculation method of (15)N isotopologue enrichment are presented. Using this method, we could demonstrate that young parasite tubercles assimilate inorganic nitrogen as (15)N-ammonium when supplied directly through batch incubation but not when supplied by translocation from host root phloem, contrary to (15)N2-glutamine. (15)N2-glutamine mobility from host roots to parasite tubercles followed by its low metabolism in tubercles suggests that the host-derived glutamine acts as an important nitrogen containing storage compound in the young tubercle of Phelipanche ramosa. PMID:24359440

  14. 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.

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

    PubMed Central

    Shchepin, Roman V.; Chekmenev, Eduard Y.

    2015-01-01

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

  16. Through-space (19) F-(15) N couplings for the assignment of stereochemistry in flubenzimine.

    PubMed

    Ghiviriga, Ion; Rubinski, Miles A; Dolbier, William R

    2016-07-01

    Through-space (19) F-(15) N couplings revealed the configuration of flubenzimine, with the CF3 group on N4 pointing towards the lone pair of N5. The (19) F-(15) N coupling constants were measured at natural abundance using a spin-state selective indirect-detection pulse sequence. As (15) N-labelled proteins are routinely synthesized for NMR studies, through-space (19) F-(15) N couplings have the potential to probe the stereochemistry of these proteins by (19) F labelling of some amino acids or can reveal the site of docking of fluorine-containing drugs. Copyright © 2016 John Wiley & Sons, Ltd.

  17. High-throughput backbone resonance assignment of small 13C, 15N-labeled proteins by a triple-resonance experiment with four sequential connectivity pathways using chemical shift-dependent, apparent 1J ( 1H, 13C): HNCACB codedHAHB

    NASA Astrophysics Data System (ADS)

    Pegan, Scott; Kwiatkowski, Witek; Choe, Senyon; Riek, Roland

    2003-12-01

    The proposed three-dimensional triple-resonance experiment HNCACB codedHAHB correlates sequential 15N, 1H moieties via the chemical shifts of 13C α, 13C β, 1H α, and 1H β. The four sequential correlation pathways are achieved by the incorporation of the concept of chemical shift-coding [J. Biomol. NMR 25 (2003) 281] to the TROSY-HNCACB experiment. The monitored 1H α and 1H β chemical shifts are then coded in the line shape of the cross-peaks of 13C α, 13C β along the 13C dimension through an apparent residual scalar coupling, the size of which depends on the attached hydrogen chemical shift. The information of four sequential correlation pathways enables a rapid backbone assignment. The HNCACB codedHAHB experiment was applied to ˜85% labeled 13C, 15N-labeled amino-terminal fragment of Vaccinia virus DNA topoisomerase I comprising residues 1-77. After one day of measurement on a Bruker Avance 700 MHz spectrometer and 8 h of manual analysis of the spectrum 93% of the backbone assignment was achieved.

  18. 13C-13C and 15N-13C correlation spectroscopy of membrane-associated and uniformly labeled human immunodeficiency virus and influenza fusion peptides: Amino acid-type assignments and evidence for multiple conformations

    NASA Astrophysics Data System (ADS)

    Bodner, Michele L.; Gabrys, Charles M.; Struppe, Jochem O.; Weliky, David P.

    2008-02-01

    Many viruses which cause disease including human immunodeficiency virus (HIV) and influenza are "enveloped" by a membrane and infection of a host cell begins with joining or "fusion" of the viral and target cell membranes. Fusion is catalyzed by viral proteins in the viral membrane. For HIV and for the influenza virus, these fusion proteins contain an ˜20-residue apolar "fusion peptide" that binds to target cell membranes and plays a critical role in fusion. For this study, the HIV fusion peptide (HFP) and influenza virus fusion peptide (IFP) were chemically synthesized with uniform C13, N15 labeling over large contiguous regions of amino acids. Two-dimensional C13-C13 and N15-C13 spectra were obtained for the membrane-bound fusion peptides and an amino acid-type C13 assignment was obtained for the labeled residues in HFP and IFP. The membrane used for the HFP sample had a lipid headgroup and cholesterol composition comparable to that of host cells of the virus, and the C13 chemical shifts were more consistent with β strand conformation than with helical conformation. The membrane used for the IFP sample did not contain cholesterol, and the chemical shifts of the dominant peaks were more consistent with helical conformation than with β strand conformation. There were additional peaks in the IFP spectrum whose shifts were not consistent with helical conformation. An unambiguous C13 and N15 assignment was obtained in an HFP sample with more selective labeling, and two shifts were identified for the Leu-9 CO, Gly-10 N, and Gly-10 Cα nuclei. These sets of two shifts may indicate two β strand registries such as parallel and antiparallel. Although most spectra were obtained on a 9.4T instrument, one C13-C13 correlation spectrum was obtained on a 16.4T instrument and was better resolved than the comparable 9.4T spectrum. More selective labeling and higher field may, therefore, be approaches to obtaining unambiguous assignments for membrane-associated fusion peptides.

  19. Litter type control on soil C and N stabilization dynamics in a temperate forest.

    PubMed

    Hatton, Pierre-Joseph; Castanha, Cristina; Torn, Margaret S; Bird, Jeffrey A

    2015-03-01

    While plant litters are the main source of soil organic matter (SOM) in forests, the controllers and pathways to stable SOM formation remain unclear. Here, we address how litter type ((13) C/(15) N-labeled needles vs. fine roots) and placement-depth (O vs. A horizon) affect in situ C and N dynamics in a temperate forest soil after 5 years. Litter type rather than placement-depth controlled soil C and N retention after 5 years in situ, with belowground fine root inputs greatly enhancing soil C (x1.4) and N (x1.2) retention compared with aboveground needles. While the proportions of added needle and fine root-derived C and N recovered into stable SOM fractions were similar, they followed different transformation pathways into stable SOM fractions: fine root transfer was slower than for needles, but proportionally more of the remaining needle-derived C and N was transferred into stable SOM fractions. The stoichiometry of litter-derived C vs. N within individual SOM fractions revealed the presence at least two pools of different turnover times (per SOM fraction) and emphasized the role of N-rich compounds for long-term persistence. Finally, a regression approach suggested that models may underestimate soil C retention from litter with fast decomposition rates.

  20. Mapping Soil Carbon from Cradle to Grave: C Transformations of Root Exudates and Plant Litter

    NASA Astrophysics Data System (ADS)

    Pett-Ridge, J.; Keiluweit, M.; Nuccio, E.; Bougoure, J.; Weber, P. K.; Brodie, E.; Mayali, X.; Shi, S.; Hwang, M.; Thelen, M.; Firestone, M.; Kleber, M.; Nico, P. S.

    2013-12-01

    Carbon cycling in the rhizosphere is a nexus of biophysical interactions between plant roots, microorganisms, and the soil organo-mineral matrix. Plant roots provide 30-40% of soil organic C inputs, accelerate the rate of organic matter mineralization by ~10X, and support an active microhabitat for microbial transformation of soil C. Our research on how roots influence decomposition of soil organic matter in both simplified and complex microcosms uses geochemical characterization, molecular microbiology, isotope tracing, metabolomics and novel imaging approaches (';ChipSIP' and ';STXM-SIMS') to trace the fate of isotopically labelled root exudates and plant tissues. Our previous work suggests root exudates drive O2 limitation, alter metal chemistry and mineralogy, and influence the availability of SOM. Our most recent experiments using synthetic rhizospheres were designed to identify the role of root exudates on ligno-cellulose decomposition in soils. Cultures of 13C/15N-labeled single plant cells (lignin-rich tracheary elements) were added to rhizosphere microcosm soils, and their decomposition followed under the influence of different root exudates using the dual imaging approach ';STXM-SIMS'. Using this combination of X-ray spectromicroscopy and NanoSIMS, we imaged the deconstruction of 13C/15N-labeled ligno-cellulose in situ, and mapped associations of plant cell-derived decomposition products with specific soil minerals. We've also looked at microbial community function in the more complex rhizospheres surrounding roots of the annual grass Avena fatua. Using an isotope array that allows us to follow root C into bacterial, fungal, and microfaunal communities, we tracked the movement of 13C from labeled exudates and 15N from labeled root litter into the soil microbial community. Our results indicate that the microbial communities involved in litter decomposition differ in rhizosphere versus bulk soils, which may have implications for carbon stabilization in soil.

  1. Earthworm effects on the incorporation of litter C and N into soil organic matter in a sugar maple forest.

    PubMed

    Fahey, Timothy J; Yavitt, Joseph B; Sherman, Ruth E; Maerz, John C; Groffman, Peter M; Fisk, Melany C; Bohlen, Patrick J

    2013-07-01

    To examine the mechanisms of earthworm effects on forest soil C and N, we double-labeled leaf litter with 13C and 15N, applied it to sugar maple forest plots with and without earthworms, and traced isotopes into soil pools. The experimental design included forest plots with different earthworm community composition (dominated by Lumbricus terrestris or L. rubellus). Soil carbon pools were 37% lower in earthworm-invaded plots largely because of the elimination of the forest floor horizons, and mineral soil C:N was lower in earthworm plots despite the mixing of high C:N organic matter into soil by earthworms. Litter disappearance over the first winter-spring was highest in the L. terrestris (T) plots, but during the warm season, rapid loss of litter was observed in both L. rubellus (R) and T plots. After two years, 22.0% +/- 5.4% of 13C released from litter was recovered in soil with no significant differences among plots. Total recovery of added 13C (decaying litter plus soil) was much higher in no-worm (NW) plots (61-68%) than in R and T plots (20-29%) as much of the litter remained in the former whereas it had disappeared in the latter. Much higher percentage recovery of 15N than 13C was observed, with significantly lower values for T than R and NW plots. Higher overwinter earthworm activity in T plots contributed to lower soil N recovery. In earthworm-invaded plots isotope enrichment was highest in macroaggregates and microaggregates whereas in NW plots silt plus clay fractions were most enriched. The net effect of litter mixing and priming of recalcitrant soil organic matter (SOM), stabilization of SOM in soil aggregates, and alteration of the soil microbial community by earthworm activity results in loss of SOM and lowering of the C:N ratio. We suggest that earthworm stoichiometry plays a fundamental role in regulating C and N dynamics of forest SOM.

  2. Fate and metabolism of [15N]2,4,6-trinitrotoluene in soil.

    PubMed

    Weiss, Martin; Geyer, Roland; Russow, Rolf; Richnow, Hans H; Kästner, Matthias

    2004-08-01

    The fates of the labels from [14C] and [15N] trinitrotoluene were analyzed in bioreactors under aerobic conditions in soil treated by a fungal bioremediation process with Stropharia rugosoannulata and in control soil. Up to 17.5% of the 15N label had a different fate than the 14C label. Three N-mineralization processes were identified in detailed experiments with [15N]TNT. About 2% of the 15N label was found as NO3- and NH4+, showing simultaneous processes of direct TNT denitration (I) and reduction with cleavage of the amino groups (II). The enrichment of NO2-/NO3- (up to 7.5 atom% 15N abundance) indicates the formation of Meisenheimer complexes with a denitration of [15N]TNT. A 1.4% of the label was found distributed between N2O and N2. However, the 15N enrichment of the N2O (up to 38 atom%) demonstrated that both N atoms were generated from the labeled TNT and clearly indicates a novel formation process (III). We propose, as an explanation, the generation of N2O by cleavage from condensed azoxy metabolites. In addition, 1.7% of the 15N label was detected as biogenic amino acids in the wheat straw containing the fungus. Overall, 60 to 85% of the applied [15N]TNT was degraded and 52 to 64% was found as nonextractable residues in the soil matrix. Three percent was detected as 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene.

  3. Earthworms and litter management contributions to ecosystem services in a tropical agroforestry system.

    PubMed

    Fonte, Steven J; Six, Johan

    2010-06-01

    The development of sustainable agricultural systems depends in part upon improved management of non-crop species to enhance the overall functioning and provision of services by agroecosystems. To address this need, our research examined the role of earthworms and litter management on nutrient dynamics, soil organic matter (SOM) stabilization, and crop growth in the Quesungual agroforestry system of western Honduras. Field mesocosms were established with two earthworm treatments (0 vs. 8 Pontoscolex corethrurus individuals per mesocosm) and four litter quality treatments: (1) low-quality Zea mays, (2) high-quality Diphysa robinioides, (3) a mixture of low- and high-quality litters, and (4) a control with no organic residues applied. Mesocosms included a single Z. mays plant and additions of 15N-labeled inorganic nitrogen. At maize harvest, surface soils (0-15 cm) in the mesocosms were sampled to determine total and available P as well as the distribution of C, N, and 15N among different aggregate-associated SOM pools. Maize plants were divided into grain and non-grain components and analyzed for total P, N, and 15N. Earthworm additions improved soil structure as demonstrated by a 10% increase in mean weight diameter and higher C and N storage within large macro-aggregates (>2000 microm). A corresponding 17% increase in C contained in micro-aggregates within the macro-aggregates indicates that earthworms enhance the stabilization of SOM in these soils; however, this effect only occurred when organic residues were applied. Earthworms also decreased available P and total soil P, indicating that earthworms may facilitate the loss of labile P added to this system. Earthworms decreased the recovery of fertilizer-derived N in the soil but increased the uptake of 15N by maize by 7%. Litter treatments yielded minimal effects on soil properties and plant growth. Our results indicate that the application of litter inputs and proper management of earthworm populations can have

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

    PubMed Central

    Lewandowski, Józef R.; De Paëpe, Gaël; Eddy, Matthew T.; Griffin, Robert G.

    2009-01-01

    We describe a new magic angle spinning (MAS) NMR experiment for obtaining 15N-15N correlation spectra. The approach yields direct information about the secondary and tertiary structure of proteins, including identification of α-helical stretches and inter-strand connectivity in antiparallel β-sheets, which are of major interest for structural studies of membrane proteins and amyloid fibrils. The method, 15N-15N proton assisted recoupling (PAR), relies on a second order mechanism, third spin assisted recoupling (TSAR), used previously in the context of 15N-13C and 13C-13C polarization transfer schemes. In comparison to 15N-15N proton driven spin diffusion experiments, the PAR technique accelerates polarization transfer between 15N’s by a factor of ~102−103, and is furthermore applicable over the entire range of currently available MAS frequencies (10–70 kHz). PMID:19334788

  5. Rates and quantities of carbon flux to ectomycorrhizal mycelium following 14C pulse labeling of Pinus sylvestris seedlings: effects of litter patches and interaction with a wood-decomposer fungus.

    PubMed

    Leake, J R; Donnelly, D P; Saunders, E M; Boddy, L; Read, D J

    2001-02-01

    We used a novel digital autoradiographic technique that enabled, for the first time, simultaneous visualization and quantification of spatial and temporal changes in carbon allocation patterns in ectomycorrhizal mycelia. Mycorrhizal plants of Pinus sylvestris L. were grown in microcosms containing non-sterile peat. The time course and spatial distribution of carbon allocation by P. sylvestris to mycelia of its mycorrhizal partners, Paxillus involutus (Batsch) Fr. and Suillus bovinus (L.): Kuntze, were quantified following 14C pulse labeling of the plants. Litter patches were used to investigate the effects of nutrient resource quality on carbon allocation. The wood-decomposer fungus Phanerochaete velutina (D.C.: Pers.) Parmasto was introduced to evaluate competitive and territorial interactions between its mycelial cords and the mycelial system of S. bovinus. Growth of ectomycorrhizal mycelium was stimulated in the litter patches. Nearly 60% of the C transferred from host plant to external mycorrhizal mycelium (> 2 mm from root surfaces) was allocated to mycelium in the patches, which comprised only 12% of the soil area available for mycelial colonization. Mycelia in the litter patch most recently colonized by mycorrhizal mycelium received the largest investment of carbon, amounting to 27 to 50% of the total 14C in external mycorrhizal mycelium. The amount of C transfer to external mycelium of S. bovinus following pulse labeling was reduced from a maximum of 167 nmol in systems with no saprotroph to a maximum of 61 nmol in systems interacting with P. velutina. The 14C content of S. bovinus mycelium reached a maximum 24-36 h after labeling in control microcosms, but allocation did not reach a peak until 56 h after labeling, when S. bovinus interacted with mycelium of P. velutina. The mycelium of S. bovinus contained 9% of the total 14C in the plants (including mycorrhizae) at the end of the experiment, but this was reduced to 4% in the presence of P. velutina. The

  6. Rates and quantities of carbon flux to ectomycorrhizal mycelium following 14C pulse labeling of Pinus sylvestris seedlings: effects of litter patches and interaction with a wood-decomposer fungus.

    PubMed

    Leake, J R; Donnelly, D P; Saunders, E M; Boddy, L; Read, D J

    2001-02-01

    We used a novel digital autoradiographic technique that enabled, for the first time, simultaneous visualization and quantification of spatial and temporal changes in carbon allocation patterns in ectomycorrhizal mycelia. Mycorrhizal plants of Pinus sylvestris L. were grown in microcosms containing non-sterile peat. The time course and spatial distribution of carbon allocation by P. sylvestris to mycelia of its mycorrhizal partners, Paxillus involutus (Batsch) Fr. and Suillus bovinus (L.): Kuntze, were quantified following 14C pulse labeling of the plants. Litter patches were used to investigate the effects of nutrient resource quality on carbon allocation. The wood-decomposer fungus Phanerochaete velutina (D.C.: Pers.) Parmasto was introduced to evaluate competitive and territorial interactions between its mycelial cords and the mycelial system of S. bovinus. Growth of ectomycorrhizal mycelium was stimulated in the litter patches. Nearly 60% of the C transferred from host plant to external mycorrhizal mycelium (> 2 mm from root surfaces) was allocated to mycelium in the patches, which comprised only 12% of the soil area available for mycelial colonization. Mycelia in the litter patch most recently colonized by mycorrhizal mycelium received the largest investment of carbon, amounting to 27 to 50% of the total 14C in external mycorrhizal mycelium. The amount of C transfer to external mycelium of S. bovinus following pulse labeling was reduced from a maximum of 167 nmol in systems with no saprotroph to a maximum of 61 nmol in systems interacting with P. velutina. The 14C content of S. bovinus mycelium reached a maximum 24-36 h after labeling in control microcosms, but allocation did not reach a peak until 56 h after labeling, when S. bovinus interacted with mycelium of P. velutina. The mycelium of S. bovinus contained 9% of the total 14C in the plants (including mycorrhizae) at the end of the experiment, but this was reduced to 4% in the presence of P. velutina. The

  7. Preparation and characterization of 15N-enriched, size-defined heparan sulfate precursor oligosaccharides

    PubMed Central

    Sigulinsky, Crystal; Babu, Ponnusamy; Victor, Xylophone V.; Kuberan, Balagurunathan

    2009-01-01

    We report the preparation of size-defined [15N]N-acetylheparosan oligosaccharides from Escherichia coli-derived 15N-enriched N-acetylheparosan. Optimized growth conditions of E. coli in minimal media containing 15NH4Cl yielded [15N]N-acetylheparosan on a preparative scale. Depolymerization of [15N]N-acetylheparosan by heparitinase I yielded resolvable, even-numbered oligosaccharides ranging from disaccharide to icosaccharide. Anion-exchange chromatography-assisted fractionation afforded size-defined [15N]N-acetylheparosan oligosaccharides identifiable by ESI-TOFMS. These isotopically labeled oligosaccharides will prove to be valuable research tools for the chemoenzymatic synthesis of heparin and heparan sulfate oligosaccharides and for the study of their structural biology. PMID:19945695

  8. 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.

  9. 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

  10. 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.

  11. Ecosystem N distribution and δ15N during a century of forest regrowth after agricultural abandonment

    USGS Publications Warehouse

    Compton, J.E.; Hooker, T.D.; Perakis, S.S.

    2007-01-01

    Stable isotope ratios of terrestrial ecosystem nitrogen (N) pools reflect internal processes and input–output balances. Disturbance generally increases N cycling and loss, yet few studies have examined ecosystem δ15N over a disturbance-recovery sequence. We used a chronosequence approach to examine N distribution and δ15N during forest regrowth after agricultural abandonment. Site ages ranged from 10 to 115 years, with similar soils, climate, land-use history, and overstory vegetation (white pine Pinus strobus). Foliar N and δ15N decreased as stands aged, consistent with a progressive tightening of the N cycle during forest regrowth on agricultural lands. Over time, foliar δ15N became more negative, indicating increased fractionation along the mineralization–mycorrhizal–plant uptake pathway. Total ecosystem N was constant across the chronosequence, but substantial internal N redistribution occurred from the mineral soil to plants and litter over 115 years (>25% of ecosystem N or 1,610 kg ha−1). Temporal trends in soil δ15N generally reflected a redistribution of depleted N from the mineral soil to the developing O horizon. Although plants and soil δ15N are coupled over millennial time scales of ecosystem development, our observed divergence between plants and soil suggests that they can be uncoupled during the disturbance-regrowth sequence. The approximate 2‰ decrease in ecosystem δ15N over the century scale suggests significant incorporation of atmospheric N, which was not detected by traditional ecosystem N accounting. Consideration of temporal trends and disturbance legacies can improve our understanding of the influence of broader factors such as climate or N deposition on ecosystem N balances and δ15N.

  12. 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

  13. Dual, differential isotope labeling shows the preferential movement of labile plant constituents into mineral-bonded soil organic matter.

    PubMed

    Haddix, Michelle L; Paul, Eldor A; Cotrufo, M Francesca

    2016-06-01

    The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral-bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual (13) C and (15) N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched (13) C and (15) N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance (13) C-CO2 and (15) N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in (13) C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO2 measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral-associated organic matter. PMID:27142168

  14. The 15N isotope to evaluate fertilizer nitrogen absorption efficiency by the coffee plant.

    PubMed

    Fenilli, Tatiele A B; Reichart, Klaus; Bacchi, Osny O S; Trivelin, Paulo C O; Dourado-Neto, Durval

    2007-12-01

    The use of the 15N label for agronomic research involving nitrogen (N) cycling and the fate of fertilizer-N is well established, however, in the case of long term experimentation with perennial crops like citrus, coffee and rubber tree, there are still shortcomings mainly due to large plant size, sampling procedures, detection levels and interferences on the system. This report tries to contribute methodologically to the design and development of 15N labeled fertilizer experiments, using as an example a coffee crop fertilized with 15N labeled ammonium sulfate, which was followed for two years. The N of the plant derived from the fertilizer was studied in the different parts of the coffee plant in order to evaluate its distribution within the plant and the agronomic efficiency of the fertilizer application practice. An enrichment of the fertilizer-N of the order of 2% 15N abundance was sufficient to study N absorption rates and to establish fertilizer-N balances after one and two years of coffee cropping. The main source of errors in the estimated values lies in the inherent variability among field replicates and not in the measurements of N contents and 15N enrichments of plant material by mass-spectrometry. PMID:18066442

  15. The 15N isotope to evaluate fertilizer nitrogen absorption efficiency by the coffee plant.

    PubMed

    Fenilli, Tatiele A B; Reichart, Klaus; Bacchi, Osny O S; Trivelin, Paulo C O; Dourado-Neto, Durval

    2007-12-01

    The use of the 15N label for agronomic research involving nitrogen (N) cycling and the fate of fertilizer-N is well established, however, in the case of long term experimentation with perennial crops like citrus, coffee and rubber tree, there are still shortcomings mainly due to large plant size, sampling procedures, detection levels and interferences on the system. This report tries to contribute methodologically to the design and development of 15N labeled fertilizer experiments, using as an example a coffee crop fertilized with 15N labeled ammonium sulfate, which was followed for two years. The N of the plant derived from the fertilizer was studied in the different parts of the coffee plant in order to evaluate its distribution within the plant and the agronomic efficiency of the fertilizer application practice. An enrichment of the fertilizer-N of the order of 2% 15N abundance was sufficient to study N absorption rates and to establish fertilizer-N balances after one and two years of coffee cropping. The main source of errors in the estimated values lies in the inherent variability among field replicates and not in the measurements of N contents and 15N enrichments of plant material by mass-spectrometry.

  16. Earthworm effects on the incorporation of litter C and N into soil organic matter in a sugar maple forest.

    PubMed

    Fahey, Timothy J; Yavitt, Joseph B; Sherman, Ruth E; Maerz, John C; Groffman, Peter M; Fisk, Melany C; Bohlen, Patrick J

    2013-07-01

    To examine the mechanisms of earthworm effects on forest soil C and N, we double-labeled leaf litter with 13C and 15N, applied it to sugar maple forest plots with and without earthworms, and traced isotopes into soil pools. The experimental design included forest plots with different earthworm community composition (dominated by Lumbricus terrestris or L. rubellus). Soil carbon pools were 37% lower in earthworm-invaded plots largely because of the elimination of the forest floor horizons, and mineral soil C:N was lower in earthworm plots despite the mixing of high C:N organic matter into soil by earthworms. Litter disappearance over the first winter-spring was highest in the L. terrestris (T) plots, but during the warm season, rapid loss of litter was observed in both L. rubellus (R) and T plots. After two years, 22.0% +/- 5.4% of 13C released from litter was recovered in soil with no significant differences among plots. Total recovery of added 13C (decaying litter plus soil) was much higher in no-worm (NW) plots (61-68%) than in R and T plots (20-29%) as much of the litter remained in the former whereas it had disappeared in the latter. Much higher percentage recovery of 15N than 13C was observed, with significantly lower values for T than R and NW plots. Higher overwinter earthworm activity in T plots contributed to lower soil N recovery. In earthworm-invaded plots isotope enrichment was highest in macroaggregates and microaggregates whereas in NW plots silt plus clay fractions were most enriched. The net effect of litter mixing and priming of recalcitrant soil organic matter (SOM), stabilization of SOM in soil aggregates, and alteration of the soil microbial community by earthworm activity results in loss of SOM and lowering of the C:N ratio. We suggest that earthworm stoichiometry plays a fundamental role in regulating C and N dynamics of forest SOM. PMID:23967585

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

    NASA Astrophysics Data System (ADS)

    Charteris, Alice; Michaelides, Katerina; Evershed, Richard

    2015-04-01

    Organic N concentrations far exceed those of inorganic N in most soils and despite much investigation, the composition and cycling of this complex pool of SOM remains poorly understood. A particular problem has been separating more recalcitrant soil organic N from that actively cycling through the soil system; an important consideration in N cycling studies and for the soil's nutrient supplying capacity. The use of 15N-labelled substrates as stable isotope tracers has contributed much to our understanding of the soil system, but the complexity and heterogeneity of soil organic N prevents thorough compound-specific 15N analyses of organic N compounds and makes it difficult to examine any 15N-labelled organic products in any detail. As a result, a significant proportion of previous work has either simply assumed that since the majority of soil N is organic, all of the 15N retained in the soil is organic N (e.g. Sebilo et al., 2013) or subtracted 15N-labelled inorganic compounds from bulk values (e.g. Pilbeam et al., 1997). While the latter approach is more accurate, these methods only provide an estimate of the bulk 15N value of an extremely complex and non-uniformly labelled organic pool. A more detailed approach has been to use microbial biomass extraction (Brookes et al., 1985) and subsequent N isotopic analysis to determine the 15N value of biomass-N, representing the fraction of 15N assimilated by microbes or the 15N cycling through the 'living' or 'active' portion of soil organic N. However, this extraction method can only generate estimates and some lack of confidence in its validity and reliability remains. Here, we present an alternative technique to obtain a measure of the assimilation of an applied 15N substrate by the soil microbial biomass and an estimate of the newly synthesized soil protein, which is representative of the magnitude of the active soil microbial biomass. The technique uses a stable isotope tracer and compound-specific 15N analysis, but

  18. Hydrogen doppler spectroscopy using 15N ions

    NASA Astrophysics Data System (ADS)

    Borucki, L.; Becker, H. W.; Gorris, F.; Kubsky, S.; Schulte, W. H.; Rolfs, C.

    The energy spread of atomic and molecular ion beams from the 4 MV Dynamitron tandem accelerator at the Ruhr-Universität Bochum has been studied and in part minimized. Using the ER= 6.40 MeV narrow resonance in 1H(15N,αγ)12C with an 15N energy spread of 4.55 keV, the Doppler broadening for several hydrogen-bearing gases was found to be in good agreement with expectation: e.g. for NH3 gas a rotational-vibrational Doppler width of 10.41 +/- 0.25 keV was observed (theory = 10.4 keV). Studies of the vibrational Doppler widths of H-bonds on a Si <100> surface were performed using a 4πγ-ray detection system together with UHV-chambers for sample preparation, transport, and analysis. The results showed that further improvements in the experimental set-ups are needed for such investigations.

  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

  20. Plant and soil natural abundance delta (15)N: indicators of relative rates of nitrogen cycling in temperate forest ecosystems.

    PubMed

    Templer, Pamela H; Arthur, Mary A; Lovett, Gary M; Weathers, Kathleen C

    2007-08-01

    Watersheds within the Catskill Mountains, New York, receive among the highest rates of nitrogen (N) deposition in the northeastern United States and are beginning to show signs of N saturation. Despite similar amounts of N deposition across watersheds within the Catskill Mountains, rates of soil N cycling and N retention vary significantly among stands of different tree species. We examined the potential use of delta (15)N of plants and soils as an indicator of relative forest soil N cycling rates. We analyzed the delta (15)N of foliage, litterfall, bole wood, surface litter layer, fine roots and organic soil from single-species stands of American beech (Fagus grandifolia), eastern hemlock (Tsuga canadensis), red oak (Quercus rubra), and sugar maple (Acer saccharum). Fine root and organic soil delta (15)N values were highest within sugar maple stands, which correlated significantly with higher rates of net mineralization and nitrification. Results from this study suggest that fine root and organic soil delta (15)N can be used as an indicator of relative rates of soil N cycling. Although not statistically significant, delta (15)N was highest within foliage, wood and litterfall of beech stands, a tree species associated with intermediate levels of soil N cycling rates and forest N retention. Our results show that belowground delta (15)N values are a better indicator of relative rates of soil N cycling than are aboveground delta (15)N values.

  1. 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

  2. 13N,15N isotope and kinetic evidence against hyponitrite as an intermediate in dentrification.

    PubMed

    Hollocher, T C; Garber, E; Cooper, A J; Reiman, R E

    1980-06-10

    13N- and 15N-labeling experiments were carried out with Paracoccus denitrificans, grown anaerobically on nitrate, to determine whether hyponitrite might be an obligatory intermediate in denitrification and a precursor of nitrous oxide. From experiments designed to trap [13N]- or [15N,15N]hyponitrite by dilution into authentic hyponitrite it was calculated that the intracellular concentration of a presumptive hyponitrite pool must be less than 0.4 mM. In order for a pool of this size to turn over rapidly enough to handle the flux of nitrogen during dentrifucation, the spontaneous rate of hyponitrite dehydration must be enhanced by a factor of several thousand through enzyme catalysis. Cell extracts failed to catalyze this reaction under a variety of conditions. It is concluded that hyponitrite cannot be an intermediate in dentrification. In addition, the assimilation of inorganic nitrogen was studied in P. denitrificans using 13N as tracer. At low concentrations (less than 10(-8) M) of labeled nitrate and nitrite 5 to 10% of the label was assimilated into non-volatile metabolites and 90 to 95% was reduced to N2. Similarly, with 15 mM [13N]nitrate, 5% of the label went into metabolites and 95% to N2. High pressure liquid chromatography analysis of the labeled metabolites indicated that the major pathway for assimilation of inorganic nitrogen in P. denitrificans under these conditions is through ammonia incorporation via the aspartase reaction. PMID:7372623

  3. 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.

  4. Diffusion technique for 15N and inorganic N analysis of low-N aqueous solutions and Kjeldahl digests.

    PubMed

    Chen, Rui Rui; Dittert, Klaus

    2008-06-01

    Diffusion of ammonia is a common sample preparation method for the stable isotope analysis of inorganic nitrogen in aqueous solution. Classical diffusion methods usually require 6-12 days of diffusion and often focus on (15)N/(14)N analysis only. More recent studies have discussed whether complete N recovery was necessary for the precise analysis of stable N isotope ratios. In this paper we present a newly revised diffusion technique that allows correct and simultaneous determination of total N and (15)N at% from aqueous solutions and Kjeldahl digests, with N concentrations down to sub-0.5-mg N L(-1) levels, and it is tested under different conditions of (15)N isotope labelling. With the modification described, the diffusion time was reduced to 72 h, while the ratios of measured and expected (15)N at% were greater than 99% and the simultaneous recovery of total N was >95%. Analysis of soil microbial biomass N and its (15)N/(14)N ratio is one of the most important applications of this diffusion technique. An experiment with soil extracts spiked with (15)N-labelled yeast showed that predigestion was necessary to prevent serious N loss during Kjeldahl digestion of aqueous samples (i.e. soil extracts). The whole method of soil microbial biomass N preparation for (15)N/(14)N analysis included chloroform fumigation, predigestion, Kjeldahl digestion and diffusion. An experiment with soil spiked with (15)N-labelled yeast was carried out to evaluate the method. Results showed a highly significant correlation of recovered and added N, with the same recovery rate (0.21) of both total N and (15)N. A k(N) value of 0.25 was obtained based on the data. In conclusion, the diffusion method works for soil extracts and microbial biomass N determination and hence could be useful in many types of soil/water studies.

  5. Covalent binding of reduced metabolites of [{sup 15}N{sub 3}]TNT to soil organic matter during a bioremediation process analyzed by {sup 15}N NMR spectroscopy

    SciTech Connect

    Achtnich, C.; Fernandes, E.; Bollag, J.M.; Knackmuss, H.J.; Lenke, H.

    1999-12-15

    Evidence is presented for the covalent binding of biologically reduced metabolites of 2,4,6-{sup 15}N{sub 3}-trinitrotoluene (TNT) to different soil fractions, using liquid {sup 15}N NMR spectroscopy. A silylation procedure was used to release soil organic matter from humin and whole soil for spectroscopic measurements. TNT-contaminated soil was spiked with 2,4,6-{sup 15}N{sub 3}-trinitrotoluene and {sup 14}C-ring labeled TNT, before treatment in a soil slurry reactor. During the anaerobic/aerobic incubation the amount of radioactivity detected in the fulvic and humic acid fractions did not change significantly whereas the radioactivity bound to humin increased to 71%. The {sup 15}N NMR spectra of the fulvic acid samples were dominated by a large peak that corresponded to aliphatic amines or ammonia. In the early stages of incubation, {sup 15}N NMR analysis of the humic acids indicated bound azoxy compounds. The signals arising from nitro and azoxy groups disappeared with further anaerobic treatment. At the end of incubation, the NMR shifts showed that nitrogen was covalently bound to humic acid as substituted amines and amides. The NMR spectra of the silylated humin suggest formation of azoxy compounds and imine linkages. Bound metabolites possessing nitro groups were also detected. Primary amines formed during the anaerobic incubation disappeared during the aerobic treatment. Simultaneously, the amount of amides and tertiary amines increased. Nitro and azoxy groups of bound molecules were still present in humin at the end of the incubation period. Formation of azoxy compounds from partially reduced TNT followed by binding and further reduction appears to be an important mechanism for the immobilization of metabolites of TNT to soil.

  6. Solid-state /sup 15/N NMR of oriented lipid bilayer bound gramicidin A'

    SciTech Connect

    Nicholson, L.K.; Moll, F.; Mixon, T.E.; LoGrasso, P.V.; Lay, J.C.; Cross, T.A.

    1987-10-20

    Highly oriented samples of lipid and gramicidin A' (8:1 molar ratio) have been prepared with the samples extensively hydrated (approximately 70% water v/w). These preparations have been shown to be completely in a bilayer phase with a transition temperature of 28/sup 0/C, and evidence is presented indicating that the gramicidin is in the channel conformation. An estimate of the disorder in the alignment of the bilayers parallel with the glass plates used to align the bilayers can be made from the asymmetry of the nuclear magnetic resonances (NMR). Such an analysis indicates a maximal range of disorder of +-3/sup 0/. Uniformly /sup 15/N-labeled gramicidin has been biosynthesized by Bacillus brevis grown in a media containing /sup 15/N-labeled Escherichia coli cells as the only nitrogen source. When prepared with labeled gramicidin, the oriented samples result in high-resolution /sup 15/N NMR spectra showing 12 resonances for the 20 nitrogen sites of the polypeptide. The frequency of the three major multiple resonance peaks has been interpreted to yield the approximate orientation of the N-H bonds in the peptide linkages with respect to the magnetic field. The bond orientations are only partially consistent with the extant structural models of gramicidin.

  7. Development and application of 15N-tracer substances for measuring the whole-body protein turnover rates in the human, especially in neonates: a review.

    PubMed

    Wutzke, Klaus D

    2012-06-01

    Our research group of the Children's Hospital of the University of Rostock (Rostock group) has long-time experience in (15)N-labelling and in using yeast protein and its hydrolysates for tracer kinetic studies to evaluate parameters of the whole-body protein metabolism in premature infants. The particular advantage of applying an economically convenient, highly (15)N-enriched, and completely labelled yeast protein for evaluating protein turnover rates is the fact that the (15)N dose is spread among all proteinogenic amino acids. The absorption has been improved by hydrolysing [(15)N]yeast protein with thermitase into a mixture of amino acids, dipeptides and tripeptides so that faecal analysis becomes unnecessary when determining turnover rates. The review shows that, in contrast to the application of single (15)N-labelled amino acids with resulting overestimation of protein turnover rates, the (15)N-labelled yeast protein thermitase hydrolysate represents the amino acid metabolism more closely without causing amino acid imbalances. The (15)N-labelled yeast protein thermitase hydrolysate leads to the estimation of reliable protein turnover rates, particularly in premature infants.

  8. Stable isotope probing with 15N achieved by disentangling the effects of genome G+C content and isotope enrichment on DNA density.

    PubMed

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

    2007-05-01

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

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

    PubMed Central

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

    2007-01-01

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

  10. Environmentally friendly animal litter

    SciTech Connect

    Chett, Boxley; McKelvie, Jessica

    2013-08-20

    A method of making an animal litter that includes geopolymerized ash, wherein, the animal litter is made from a quantity of a pozzolanic ash mixed with a sufficient quantity of water and an alkaline activator to initiate a geopolymerization reaction that forms geopolymerized ash. After the geopolymerized ash is formed, it is dried, broken into particulates, and sieved to a desired size. These geopolymerized ash particulates are used to make a non-clumping or clumping animal litter. Odor control may be accomplished with the addition of a urease inhibitor, pH buffer, an odor eliminating agent, and/or fragrance.

  11. Retrieving nitrogen isotopic signatures from fresh leaf reflectance spectra: disentangling δ(15)N from biochemical and structural leaf properties.

    PubMed

    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 δ(15)N 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 δ(15)N directly influences leaf reflectance spectra or if the relationship is based on covariation between δ(15)N and foliar nitrogen content or other leaf properties. Using a (15)N-labeling approach, we experimentally varied δ(15)N independently of any other leaf properties in three plant species across different leaf developmental and physiological states. δ(15)N 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 δ(15)N within species. Several wavelength regions important for predicting δ(15)N 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 δ(15)N, our results demonstrate that (15)N 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.

  12. 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

  13. Nitrate removal in two relict oxbow urban wetlands: a 15N mass-balance approach

    NASA Astrophysics Data System (ADS)

    Harrison, M. D.; Groffman, P. M.; Mayer, P. M.; Kaushal, S.

    2012-12-01

    A mass-balance approach was used to directly determine the flow of 15NO3- to plants, algae, and sediments,with unaccounted for 15N assumed to be denitrified. During the summer, plant and algal uptake accounted for 42%, of the added 15NO3 - in oxbow 1, less than 1% remained in the water column and 57% was unaccounted for. In oxbow 2 during the summer, plant and algal uptake accounted for 63% of the added 15NO3 -, with 1% remaining in the water column and 38% unaccounted for. During the early spring, plant and algal uptake were much lower in both oxbows, ranging from 0.05 to 13.3% of the 15N added, with 97 and 87% was unaccounted for in oxbow 1 and 2, respectively. The amount of unaccounted for 15N was equivalent to estimated areal denitrification rates of 12 and 6 mg N m-2 d-1 in the summer and 78 and 15 mg N m-2 d-1 in the spring, in oxbow 1 and oxbow 2, respectively. However, the uncertainty of these estimates is high as it was difficult to detect accumulation of 15N in the sediments which could have accounted for a very large percentage of the added 15N. Our results suggest that the two relict oxbow wetlands are sinks for NO3 - during both summer and spring. Plane view of Ox1 (A) and Ox2 (B) wetlands with closed contour intervals (color scale) and surrounding stream and upland elevations (labeled in black) located at Minebank Run, near Glen Arms, MD. 15N enrichment (atom %) of measured N pools prior to (Day 0) and after (Day 5) the end of the experiment in July 2009 and April 2010 for Ox1 and Ox2. Values are mean atom % (n = 2 algae, macrophytes and sediment; n = 6 for water samples).

  14. Littering Behavior in Public Places

    ERIC Educational Resources Information Center

    Robinson, Stuart N.

    1976-01-01

    This review summarizes the present state of knowledge concerning littering behavior. Available studies are categorized according to the variables that influence littering--individual and environmental. Theoretical issues of attitude-behavior consistency and incentive effectiveness are analyzed with respect to littering and litter control. Results…

  15. Field Experiments in Litter Control

    ERIC Educational Resources Information Center

    Finnie, William C.

    1973-01-01

    A series of urban and highway litter experiments in Richmond (Virginia), St. Louis, and Philadelphia indicated well-designed litter cans reduced littering about 15 percent along city streets and nearly 30 percent along highways. Also, the propensity to litter is critically affected by the characteristics of the individual and environmental…

  16. Compound-specific 15N stable isotope probing of N assimilation by the soil microbial biomass: a new methodological paradigm in soil N cycling

    NASA Astrophysics Data System (ADS)

    Charteris, A. F.; Knowles, T. D. J.; Michaelides, K.; Evershed, R. P.

    2015-10-01

    A compound-specific nitrogen-15 stable isotope probing (15N-SIP) technique is described which allows investigation of the fate of inorganic- or organic-N amendments to soils. The technique uses gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) to determine the δ15N values of individual amino acids (AAs; determined as N-acetyl, O-isopropyl derivatives) as proxies of biomass protein production. The δ15N values are used together with AA concentrations to quantify N assimilation of 15N-labelled substrates by the soil microbial biomass. The utility of the approach is demonstrated through incubation experiments using inorganic 15N-labelled substrates ammonium (15NH4+) and nitrate (15NO3-) and an organic 15N-labelled substrate, glutamic acid (15N-Glu). Assimilation of all the applied substrates was undetectable based on bulk soil properties, i.e. % total N (% TN), bulk soil N isotope composition and AA concentrations, all of which remained relatively constant throughout the incubation experiments. In contrast, compound-specific AA δ15N values were highly sensitive to N assimilation, providing qualitative and quantitative insights into the cycling and fate of the applied 15N-labelled substrates. The utility of this 15N-AA-SIP technique is considered in relation to other currently available methods for investigating the microbially-mediated assimilation of nitrogenous substrates into the soil organic N pool. This approach will be generally applicable to the study of N cycling in any soil, or indeed, in any complex ecosystem.

  17. Backbone and sidechain 1H, 15N and 13C assignments of the KSR1 CA1 domain

    PubMed Central

    Koveal, Dorothy; Pinheiro, Anderson S.; Peti, Wolfgang; Page, Rebecca

    2014-01-01

    The backbone and side chain resonance assignments of the murine KSR1 CA1 domain have been determined based on triple-resonance experiments using uniformly [13C, 15N]-labeled protein. This assignment is the first step towards the determination of the three-dimensional structure of the unique KSR1 CA1 domain. PMID:20737253

  18. (15)N Heteronuclear Chemical Exchange Saturation Transfer MRI.

    PubMed

    Zeng, Haifeng; Xu, Jiadi; Yadav, Nirbhay N; McMahon, Michael T; Harden, Bradley; Frueh, Dominique; van Zijl, Peter C M

    2016-09-01

    A two-step heteronuclear enhancement approach was combined with chemical exchange saturation transfer (CEST) to magnify (15)N MRI signal of molecules through indirect detection via water protons. Previous CEST studies have been limited to radiofrequency (rf) saturation transfer or excitation transfer employing protons. Here, the signal of (15)N is detected indirectly through the water signal by first inverting selectively protons that are scalar-coupled to (15)N in the urea molecule, followed by chemical exchange of the amide proton to bulk water. In addition to providing a small sensitivity enhancement, this approach can be used to monitor the exchange rates and thus the pH sensitivity of the participating (15)N-bound protons. PMID:27548755

  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

  20. Phenylalanine δ15N in Paleo Archives as a New Proxy for δ15N 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 δ15N values of past nitrate and primary production. Within the commonly measured amino acids, the δ15N value of phenylalanine (Phe) appears uniquely promising as a new proxy that reflects the nitrogen isotopic value of the original source. Phe δ15N 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 δ15N value does in fact record the average inorganic nitrogen δ15N 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 δ15N 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 δ15N 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 δ15N value of exported primary production.

  1. Measurement of (15)N enrichment of glutamine and urea cycle amino acids derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate using liquid chromatography-tandem quadrupole mass spectrometry.

    PubMed

    Nakamura, Hidehiro; Karakawa, Sachise; Watanabe, Akiko; Kawamata, Yasuko; Kuwahara, Tomomi; Shimbo, Kazutaka; Sakai, Ryosei

    2015-05-01

    6-Aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) is an amino acid-specific derivatizing reagent that has been used for sensitive amino acid quantification by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). In this study, we aimed to evaluate the ability of this method to measure the isotopic enrichment of amino acids and to determine the positional (15)N enrichment of urea cycle amino acids (i.e., arginine, ornithine, and citrulline) and glutamine. The distribution of the M and M+1 isotopomers of each natural AQC-amino acid was nearly identical to the theoretical distribution. The standard deviation of the (M+1)/M ratio for each amino acid in repeated measurements was approximately 0.1%, and the ratios were stable regardless of the injected amounts. Linearity in the measurements of (15)N enrichment was confirmed by measuring a series of (15)N-labeled arginine standards. The positional (15)N enrichment of urea cycle amino acids and glutamine was estimated from the isotopic distribution of unique fragment ions generated at different collision energies. This method was able to identify their positional (15)N enrichment in the plasma of rats fed (15)N-labeled glutamine. These results suggest the utility of LC-MS/MS detection of AQC-amino acids for the measurement of isotopic enrichment in (15)N-labeled amino acids and indicate that this method is useful for the study of nitrogen metabolism in living organisms.

  2. The Experimental Control of Littering

    ERIC Educational Resources Information Center

    Clark, Roger N.; And Others

    1972-01-01

    Behavior, incentives, and education programs were researched as factors relating to littering. Experiments in theaters, forest campgrounds, and hiking and dispersed car camping areas indicate incentive systems are necessary and feasible for curbing litter problems. (BL)

  3. 15N Hyperpolarization by Reversible Exchange Using SABRE-SHEATH

    PubMed Central

    2016-01-01

    NMR signal amplification by reversible exchange (SABRE) is a NMR hyperpolarization technique that enables nuclear spin polarization enhancement of molecules via concurrent chemical exchange of a target substrate and parahydrogen (the source of spin order) on an iridium catalyst. Recently, we demonstrated that conducting SABRE in microtesla fields provided by a magnetic shield enables up to 10% 15N-polarization (Theis, T.; et al. J. Am. Chem. Soc.2015, 137, 1404). Hyperpolarization on 15N (and heteronuclei in general) may be advantageous because of the long-lived nature of the hyperpolarization on 15N relative to the short-lived hyperpolarization of protons conventionally hyperpolarized by SABRE, in addition to wider chemical shift dispersion and absence of background signal. Here we show that these unprecedented polarization levels enable 15N magnetic resonance imaging. We also present a theoretical model for the hyperpolarization transfer to heteronuclei, and detail key parameters that should be optimized for efficient 15N-hyperpolarization. The effects of parahydrogen pressure, flow rate, sample temperature, catalyst-to-substrate ratio, relaxation time (T1), and reversible oxygen quenching are studied on a test system of 15N-pyridine in methanol-d4. Moreover, we demonstrate the first proof-of-principle 13C-hyperpolarization using this method. This simple hyperpolarization scheme only requires access to parahydrogen and a magnetic shield, and it provides large enough signal gains to enable one of the first 15N images (2 × 2 mm2 resolution). Importantly, this method enables hyperpolarization of molecular sites with NMR T1 relaxation times suitable for biomedical imaging and spectroscopy. PMID:25960823

  4. Influence of Litter Diversity on Dissolved Organic Matter Release and Soil Carbon Formation in a Mixed Beech Forest

    PubMed Central

    Scheibe, Andrea; Gleixner, Gerd

    2014-01-01

    We investigated the effect of leaf litter on below ground carbon export and soil carbon formation in order to understand how litter diversity affects carbon cycling in forest ecosystems. 13C labeled and unlabeled leaf litter of beech (Fagus sylvatica) and ash (Fraxinus excelsior), characterized by low and high decomposability, were used in a litter exchange experiment in the Hainich National Park (Thuringia, Germany). Litter was added in pure and mixed treatments with either beech or ash labeled with 13C. We collected soil water in 5 cm mineral soil depth below each treatment biweekly and determined dissolved organic carbon (DOC), δ13C values and anion contents. In addition, we measured carbon concentrations and δ13C values in the organic and mineral soil (collected in 1 cm increments) up to 5 cm soil depth at the end of the experiment. Litter-derived C contributes less than 1% to dissolved organic matter (DOM) collected in 5 cm mineral soil depth. Better decomposable ash litter released significantly more (0.50±0.17%) litter carbon than beech litter (0.17±0.07%). All soil layers held in total around 30% of litter-derived carbon, indicating the large retention potential of litter-derived C in the top soil. Interestingly, in mixed (ash and beech litter) treatments we did not find a higher contribution of better decomposable ash-derived carbon in DOM, O horizon or mineral soil. This suggest that the known selective decomposition of better decomposable litter by soil fauna has no or only minor effects on the release and formation of litter-derived DOM and soil organic matter. Overall our experiment showed that 1) litter-derived carbon is of low importance for dissolved organic carbon release and 2) litter of higher decomposability is faster decomposed, but litter diversity does not influence the carbon flow. PMID:25486628

  5. Influence of litter diversity on dissolved organic matter release and soil carbon formation in a mixed beech forest.

    PubMed

    Scheibe, Andrea; Gleixner, Gerd

    2014-01-01

    We investigated the effect of leaf litter on below ground carbon export and soil carbon formation in order to understand how litter diversity affects carbon cycling in forest ecosystems. 13C labeled and unlabeled leaf litter of beech (Fagus sylvatica) and ash (Fraxinus excelsior), characterized by low and high decomposability, were used in a litter exchange experiment in the Hainich National Park (Thuringia, Germany). Litter was added in pure and mixed treatments with either beech or ash labeled with 13C. We collected soil water in 5 cm mineral soil depth below each treatment biweekly and determined dissolved organic carbon (DOC), δ13C values and anion contents. In addition, we measured carbon concentrations and δ13C values in the organic and mineral soil (collected in 1 cm increments) up to 5 cm soil depth at the end of the experiment. Litter-derived C contributes less than 1% to dissolved organic matter (DOM) collected in 5 cm mineral soil depth. Better decomposable ash litter released significantly more (0.50±0.17%) litter carbon than beech litter (0.17±0.07%). All soil layers held in total around 30% of litter-derived carbon, indicating the large retention potential of litter-derived C in the top soil. Interestingly, in mixed (ash and beech litter) treatments we did not find a higher contribution of better decomposable ash-derived carbon in DOM, O horizon or mineral soil. This suggest that the known selective decomposition of better decomposable litter by soil fauna has no or only minor effects on the release and formation of litter-derived DOM and soil organic matter. Overall our experiment showed that 1) litter-derived carbon is of low importance for dissolved organic carbon release and 2) litter of higher decomposability is faster decomposed, but litter diversity does not influence the carbon flow.

  6. 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

  7. 15N2 Fixation by Bacteria Associated with Maize Roots at a Low Partial O2 Pressure

    PubMed Central

    Alexander, David B.; Zuberer, David A.

    1989-01-01

    Nitrogen fixation by bacteria associated with roots of intact maize plants was measured by exposing the roots to 15N2 at a partial O2 pressure (pO2) of 2 or 10 kPa. The plants were grown in a mixture of Weswood soil and sand and then transferred to plastic cylinders containing an N-free plant nutrient solution. The solution was sparged continuously with a mixture of air and N2 at a pO2 of 2 or 10 kPa. Acetylene reduction was measured after the roots were exposed to the low pO2 overnight. The air-N2 atmosphere in the cylinders was then replaced with an O2-He atmosphere at the same pO2, and the roots were exposed to 20 kPa of 15N2 for 20 to 22 h. Incorporation of 15N into the roots was 200 times greater at 2 kPa of O2 than at 10 kPa of O2. Adding l-malate (1 g of C liter−1) to the nutrient solution increased root-associated nitrogenase activity, producing a strong 15N label which could be traced into the shoots. Fixed 15N was detected in the shoots within 5 days after the plants were returned to unfertilized soil. In a similar experiment with undisturbed plants grown in fritted clay, movement of fixed 15N into the shoots was evident within 4 days after the roots were exposed to 15N2 at 2 kPa of O2. Inoculation with Azospirillum lipoferum yielded no significant differences in shoot dry weight, total nitrogen content, percent nitrogen, or 15N enrichment of plant tissues. Inoculated plants did exhibit greater root dry weight than uninoculated plants, however. PMID:16347968

  8. A novel method for trapping and analyzing 15N in NO for tracing NO sources

    NASA Astrophysics Data System (ADS)

    Kang, Ronghua; Mulder, Jan; Dörsch, Peter

    2016-04-01

    15N isotope tracing is an effective and direct approach to investigate the biological and chemical sources of nitric oxide (NO) in soil. However, NO is highly reactive and rapidly converted to nitrogen dioxide (NO2) in the presence of ozone. Various chemical conversions of NO to the more stable solutes nitrite (NO2-) and nitrate (NO3-) have been proposed, which allow analysing the 15N abundance without major fractionation. However, NO emissions from soils are usually small, posing major challenges to conversion efficiency and background contamination. Here we present a novel method in which NO is oxidized to NO2- by chromium trioxide (CrO3) prior to conversion to NO2- and NO3- in an alkaline hydrogen peroxide (H2O2) solution. Immediately following trapping, manganese dioxide (MnO2) and 5M HCl are added to remove excess H2O2, and to adjust the pH to around 6.0-7.0, respectively. The resulting solution can be stored until analysis and is none-toxic, allowing to use a modified denitrifier method (Zhu et al., submitted), where NO2- and NO3- are reduced quantitatively to nitrous oxide (N2O). Optimum NO conversion rates of > 90% even at extremely low initial NO concentration were obtained with 4% H2O2, 0.5 M NaOH, and 0.5 L min-1 gas flow rate. In a laboratory test, using NO gas with different 15N signals produced from unlabelled and labelled NO2-, we found an overall precision of 0.4‰ for unlabelled and 49.7‰ for NO enriched with 1.0 atom% 15N, respectively. This indicates that this method can be used for both natural abundance studies of NO, as well as in labelling studies tracing NO sources. Zhu J, Yu L, Bakken LR, Mørkved PT, Mulder J, Dörsch P. Controlled induction of denitrification in Pseudomonas aureofaciens: a modified denitrifier method for 15N and 18O analysis in NO3- from natural water samples by IRMS. Submitted.

  9. Comparison of three 15N methods to correct for microbial contamination when assessing in situ protein degradability of fresh forages.

    PubMed

    Kamoun, M; Ammar, H; Théwis, A; Beckers, Y; France, J; López, S

    2014-11-01

    The use of stable (15)N as a marker to determine microbial contamination in nylon bag incubation residues to estimate protein degradability was investigated. Three methods using (15)N were compared: (15)N-labeled forage (dilution method, LF), (15)N enrichment of rumen solids-associated bacteria (SAB), and (15)N enrichment of rumen liquid-associated bacteria (LAB). Herbage from forages differing in protein and fiber contents (early-cut Italian ryegrass, late-cut Italian ryegrass, and red clover) were freeze-dried and ground and then incubated in situ in the rumen of 3 steers for 3, 6, 12, 24, and 48 h using the nylon bag technique. The (15)N-labeled forages were obtained by fertilizing the plots where herbage was grown with (15)NH4 (15)NO3. Unlabeled forages (obtained from plots fertilized with NH4NO3) were incubated at the same time that ((15)NH4)2SO4 was continuously infused into the rumen of the steers, and then pellets of labeled SAB and LAB were isolated by differential centrifugation of samples of ruminal contents. The proportion of bacterial N in the incubation residues increased from 0.09 and 0.45 g bacterial N/g total N at 3 h of incubation to 0.37 and 0.85 g bacterial N/g total N at 48 h of incubation for early-cut and late-cut ryegrass, respectively. There were differences (P < 0.001) between uncorrected N degradability values and those corrected for microbial contamination with all of the methods. Apparent N degradability of the low-N, high-fiber forage (late-cut ryegrass) was 0.51, whereas the corrected values were 0.85, 0.84, and 0.77 for the LF, SAB, and LAB methods, respectively. With early-cut ryegrass and red clover, the differences between uncorrected and corrected values ranged between 6% and 13%, with small differences among the labeling methods. Generally, methods using labeled forage or labeled SAB and LAB provided similar corrected degradability values. The accuracy in estimating the extent of degradation of protein in the rumen from in situ

  10. Potential probe for examining opiate-receptor interactions: model compound study of dynamic effects on /sup 15/N INEPT enhancements

    SciTech Connect

    Schilling, K.H.; Mikita, M.A.

    1987-10-01

    Model systems were chosen in an attempt to mimic the proton exchange environment of an agonist nitrogen in an opiate-receptor interaction. The two model systems studied were an ammonium: 18-crown-6 ether complex and a quinuclidine-trifluoroacetic acid ion pair. Each system was examined for their effects on /sup 15/N NMR INEPT enhancements. Both models were found to retard proton exchange dynamics, as observed by increased enhancements relative to free ions in neutral aqueous solutions. These results suggest that the confinement of a protonated nitrogen, such as that expected in receptor binding, may alter exchange dynamics to favor INEPT enhancements, while unbound agonists would remain unenhanced. As a result, /sup 15/N NMR INEPT enhancements from a solution of receptor subtypes with an appropriate /sup 15/N-labeled agonist may present a means of exploring the dynamics of direct opiate-receptor interactions.

  11. Detection of organic sulfur by {sup 15}N and {sup 19}F NMR via formation of iminosulfuranes

    SciTech Connect

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

    1992-08-01

    We have synthesized new iminosulfuranes from a variety of diaryl-and dialkyl sulfides and dibenzothiophene. The pattern of {sup 15}N chemical shifts indicates that functional groups attached to sulfur are not simply resolved into aryl and alkyl groups. Thus, resolution of sulfur functional groups using {sup 15}N NMR via iminosulfurane does not appear practicable. However, iminosulfurane formation, together with the N-haloamide reaction and the Pummerer rearrangement, provides pathways for chemical discrimination of different sulfur substituents using unique {sup 15}N- or, {sup 19}F-labelled fragments for different categories of sulfur functional groups. In efforts currently underway, we are applying these reactions to methylated extracts and conversion products of the high-organic-sulfur containing Yugoslavian Rasa and Spanish Mequinenza lignites. 1 tab, 14 refs.

  12. Detection of organic sulfur by [sup 15]N and [sup 19]F NMR via formation of iminosulfuranes

    SciTech Connect

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

    1992-08-01

    We have synthesized new iminosulfuranes from a variety of diaryl-and dialkyl sulfides and dibenzothiophene. The pattern of [sup 15]N chemical shifts indicates that functional groups attached to sulfur are not simply resolved into aryl and alkyl groups. Thus, resolution of sulfur functional groups using [sup 15]N NMR via iminosulfurane does not appear practicable. However, iminosulfurane formation, together with the N-haloamide reaction and the Pummerer rearrangement, provides pathways for chemical discrimination of different sulfur substituents using unique [sup 15]N- or, [sup 19]F-labelled fragments for different categories of sulfur functional groups. In efforts currently underway, we are applying these reactions to methylated extracts and conversion products of the high-organic-sulfur containing Yugoslavian Rasa and Spanish Mequinenza lignites. 1 tab, 14 refs.

  13. Combining long term field experiments and nanoscale analysis to enhance process understanding of root litter stabilization by mineral interactions

    NASA Astrophysics Data System (ADS)

    Chabbi, Abad; Baumann, Karen; Remusat, Laurent; Barre, Pierre; Dignac, Marie-France; Rumpel, Cornelia

    2015-04-01

    Mineral interaction may affect the stabilisation of root litter directly or indirectly after microbial decomposition and transformation. The importance of both processes may vary within the soil profile. In this study we studied C stabilisation of isotopically labelled root litter (13C and 15N), which was incubated during 3 year in the field at different soil depth. Samples from this field experiment were recovered and subjected to nanoscale analyses in order to elucidate mineral interactions occurring in different parts of the soil profile. Our results showed enrichment of mineral associated organic matter in subsoil horizons. However, material derived from new plant litter may be stabilised at similar rates in top- and subsoil horizons. N-containing compounds are enriched in the mineral associated fraction of subsoil horizons, indicating enrichment of microbial derived material with depth. Nano scale analyses showed that indeed plant-derived material may be associated with metal oxides in topsoil horizons, whereas the mineral associated organic matter in subsoil horizons may consist of microbial cells. Interestingly, in contrast to short term laboratory analysis, decoupling of C and N through stabilisation with soil minerals was observed during this long term field experiment. Our results indicate that the nature of OM stabilised by mineral interactions is depth specific. Therefore, we suggest, that plant derived lignocellulosic material may be preserved by mineral interactions in topsoil given its incomplete degradation, thereby leading to the formation of functional groups and favouring adsorption to soil minerals. This is consistent with the higher state of lignin-degradation observed in topsoil horizons as compared to subsoil. At depth, where microorganisms are most likely energy limited, degradation of fresh plant litter may be complete, thereby diminishing the formation of lignocellulosic compounds capable of sorption onto metal oxides. As a result

  14. Aliphatic (1)H, (13)C and (15)N chemical shift assignments of dihydrofolate reductase from the psychropiezophile Moritella profunda in complex with NADP(+) and folate.

    PubMed

    Loveridge, E Joel; Matthews, Stella M; Williams, Christopher; Whittaker, Sara B-M; Günther, Ulrich L; Evans, Rhiannon M; Dawson, William M; Crump, Matthew P; Allemann, Rudolf K

    2013-04-01

    Dihydrofolate reductase from the deep-sea bacterium Moritella profunda (MpDHFR) has been (13)C/(15)N isotopically labelled and purified. Here, we report the aliphatic (1)H, (13)C and (15)N resonance assignments of MpDHFR in complex with NADP(+) and folate. The spectra of MpDHFR suggest considerably greater conformational heterogeneity than is seen in the closely related DHFR from Escherichia coli.

  15. Cerebral glutamine metabolism under hyperammonemia determined in vivo by localized 1H and 15N NMR spectroscopy

    PubMed Central

    Cudalbu, Cristina; Lanz, Bernard; Duarte, João MN; Morgenthaler, Florence D; Pilloud, Yves; Mlynárik, Vladimir; Gruetter, Rolf

    2012-01-01

    Brain glutamine synthetase (GS) is an integral part of the glutamate–glutamine cycle and occurs in the glial compartment. In vivo Magnetic Resonance Spectroscopy (MRS) allows noninvasive measurements of the concentrations and synthesis rates of metabolites. 15N MRS is an alternative approach to 13C MRS. Incorporation of labeled 15N from ammonia in cerebral glutamine allows to measure several metabolic reactions related to nitrogen metabolism, including the glutamate–glutamine cycle. To measure 15N incorporation into the position 5N of glutamine and position 2N of glutamate and glutamine, we developed a novel 15N pulse sequence to simultaneously detect, for the first time, [5-15N]Gln and [2-15N]Gln+Glu in vivo in the rat brain. In addition, we also measured for the first time in the same experiment localized 1H spectra for a direct measurement of the net glutamine accumulation. Mathematical modeling of 1H and 15N MRS data allowed to reduce the number of assumptions and provided reliable determination of GS (0.30±0.050 μmol/g per minute), apparent neurotransmission (0.26±0.030 μmol/g per minute), glutamate dehydrogenase (0.029±0.002 μmol/g per minute), and net glutamine accumulation (0.033±0.001 μmol/g per minute). These results showed an increase of GS and net glutamine accumulation under hyperammonemia, supporting the concept of their implication in cerebral ammonia detoxification. PMID:22167234

  16. 1H and 15N nuclear magnetic resonance assignment and secondary structure of the cytotoxic ribonuclease alpha-Sarcin.

    PubMed Central

    Campos-Olivas, R.; Bruix, M.; Santoro, J.; Martínez del Pozo, A.; Lacadena, J.; Gavilanes, J. G.; Rico, M.

    1996-01-01

    The ribosome-inactivating protein alpha-Sarcin (alpha S) is a 150-residue fungal ribonuclease that, after entering sensitive cells, selectively cleaves a single phosphodiester bond in an universally conserved sequence of the major rRNA to inactivate the ribosome and thus exert its cytotoxic action. As a first step toward establishing the structure-dynamics-function relationships in this system, we have carried out the assignment of the 1H and 15N NMR spectrum of alpha S on the basis of homonuclear (1H-1H) and heteronuclear (1H-15N) two-dimensional correlation spectra of a uniformly 15N-labeled sample, and two selectively 15N-labeled (Tyr and Phe) samples, as well as a single three-dimensional experiment. The secondary structure of alpha S, as derived from the characteristic patterns of dipolar connectivities between backbone protons, conformational chemical shifts, and the protection of backbone amide protons against exchange, consists of a long N-terminal beta-hairpin, a short alpha-helical segment, and a C-terminal beta-sheet of five short strands arranged in a + 1, + 1, + 1, + 1 topology, connected by long loops in which the 13 Pro residues are located. PMID:8732769

  17. Stepwise enrichment of 15N along food chains: Further evidence and the relation between δ 15N and animal age

    NASA Astrophysics Data System (ADS)

    Minagawa, Masao; Wada, Eitaro

    1984-05-01

    The isotopic composition of nitrogen was measured in marine and fresh-water animals from the East China Sea, The Bering Sea, Lake Ashinoko and Usujiri intertidal zone. Primary producers, showed average δ15Nversus atmospheric nitrogen of +5.0%. (+3.4 to +7.5) in the Bering Sea and Lake Ashinoko, and +6.8%. (+6.0 to +7.6) in Usujiri intertidal zone. Blue green algae from the East China Sea show an average -0.55%. (-0.8 to +1.2). All consumers, Zooplankton, fish and bird exhibited Stepwise enrichment of 15N with increasing trophic level. The 15N enrichment at a single feeding process ranged from +1.3 to +5.3 averaging +3.4 ± 1.1%.. This isotopic fractionation seems to be independent of habitat. The effect of age in animals was obtained by analyzing two marine mussels. The soft tissue nitrogen showed +2.0%. enrichment relative to that of primary producers, and the magnitude was almost constant with shell ages ranging from 0 to 8 years. A similar 15N enrichment occurs in all Molluscs, Crustaceans, Insecta, Amphibia, Fish, Ave and Mammal species regardless of the difference in the form of excreted nitrogen and in laboratory cultured fish, brine shrimp and mice (+2.9 to +4.9%.). The excreted ammonia from guppy was sufficiently light to balance the concentration of 15N to animal body.

  18. Quantification of (15)N-nitrate in urine with gas chromatography combustion isotope ratio mass spectrometry to estimate endogenous NO production.

    PubMed

    Houben, Els; Hamer, Henrike M; Luypaerts, Anja; De Preter, Vicky; Evenepoel, Pieter; Rutgeerts, Paul; Verbeke, Kristin

    2010-01-15

    The use of stable isotope labeled substrates and subsequent analysis of urinary nitrate, forms a noninvasive test for evaluation of the in vivo NO metabolism. The present paper describes a new method for simultaneous quantification of (15)N-nitrate and total nitrate with gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS). Nitrate, isolated from urine with a nitrate selective resin, was reduced to nitrite using copperized cadmium. Subsequently, Sudan I was formed by diazotation. Sudan II was added as internal standard, and both molecules were analyzed with GC-C-IRMS as tert-butyldimethylsilyl derivatives. The accuracy was determined during a recovery study of two different known nitrate concentrations and two (15)N-enrichments. A recovery of 101.6% and 103.9% for total nitrate and 107.6% and 91.2% for (15)N-nitrate was obtained, respectively. The validated method was applied on complete 72 h urine collections after intravenous administration of (15)N-nitrate and (15)N-arginine in humans. On average, 51.8% (47.0-71.0%) of administered (15)N-nitrate was excreted, while 0.68% (0.44-1.17%) of (15)N-arginine was metabolized to nitrate. In conclusion, this method can be used for accurate simultaneous determination of (15)N-nitrate and total nitrate concentrations in urine and can be applied in clinical studies for noninvasive evaluation of NO metabolism in vivo.

  19. The Five-Year Fate of a 15N Tracer in a Mixed Deciduous Forest: Retention, Redistribution, and Differences by Mycorrhizal Association

    NASA Astrophysics Data System (ADS)

    Goodale, C. L.

    2015-12-01

    The impact of nitrogen deposition on forest ecosystems depends in large part on its fate: uptake by trees can stimulate growth, while gaseous or leaching losses contribute to air and water pollution and represent the loss of a limiting nutrient. Past tracer studies have shown that soils dominate the short-term fate of added 15N, but its longer-term term fate remains uncertain. This study examined how much 15N tracer moved plant or soil pools or was lost over 5-6 years. In 2007, a 15N tracer (0.21 kg/ha as 99% enriched 15N-KNO3) was added to 0.25 ha mixed hardwood forest in central NY. All of the tracer was recovered in the days after its addition, but recovery fell to 78% by the end of this year (25% surface litter, 48% 0-10 cm soil, 5% roots). One year later, recovery in these pools fell (to 51%), with losses from surface litter (-11%) and the 0-10 cm soils (-15%), including losses from the "heavy" soil fraction. Additional tracer moved to other plant pools (+5%) and to deeper soil (+13%; up to 30 cm), for a total recovery of 69% of the added tracer. Between years 1 and 5-6, only total tracer recovery decreased by only 1.4%. Recovery decreased in foliage (-0.2%), all roots (-3.5%), and surface litter (-9.8%), while increasing in woody biomass (+0.9%), 0-10 cm soil (+8.9%), and deep soil (+2.3%; up to 50 cm). Tracer recovery in live and dead plant N pools (11%) did not change, as 3% moved from roots into aboveground plant tissues and 3% moved from live plant pools into leaf litter; these results imply no net transfer of 15N from soil to plants during this period. Over all 5-6 years, only 1.6% of the tracer moved into bark or wood, a small but important sink because of its high C:N ratio; however, roughly one-third of this total was in wood formed prior to the start of the tracer addition. Tree species differed in their recovery of 15N: the six species with ectomycorrhizal associations showed more enrichment than the four species with arbuscular mycorrhizae. It is

  20. Reducing Children's Littering on a Nature Trail

    ERIC Educational Resources Information Center

    LaHart, David E.; Bailey, Jon S.

    1975-01-01

    This study compared incentives and educational methods to motivate children to pick up litter and to prevent littering. Incentives did aid in getting litter picked up. One-sentence anti-litter statements, educational materials, and lectures reduced littering, but incentives did not. (MR)

  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. 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

  3. 15N chemical shift referencing in solid state NMR.

    PubMed

    Bertani, Philippe; Raya, Jésus; Bechinger, Burkhard

    2014-01-01

    Solid-state NMR spectroscopy has much advanced during the last decade and provides a multitude of data that can be used for high-resolution structure determination of biomolecules, polymers, inorganic compounds or macromolecules. In some cases the chemical shift referencing has become a limiting factor to the precision of the structure calculations and we have therefore evaluated a number of methods used in proton-decoupled (15)N solid-state NMR spectroscopy. For (13)C solid-state NMR spectroscopy adamantane is generally accepted as an external standard, but to calibrate the (15)N chemical shift scale several standards are in use. As a consequence the published chemical shift values exhibit considerable differences (up to 22 ppm). In this paper we report the (15)N chemical shift of several commonly used references compounds in order to allow for comparison and recalibration of published data and future work. We show that (15)NH4Cl in its powdered form (at 39.3 ppm with respect to liquid NH3) is a suitable external reference as it produces narrow lines when compared to other reference compounds and at the same time allows for the set-up of cross-polarization NMR experiments. The compound is suitable to calibrate magic angle spinning and static NMR experiments. Finally the temperature variation of (15)NH4Cl chemical shift is reported.

  4. Nitrogen input 15N-signatures are reflected in plant 15N natural abundances of N-rich tropical forest in China

    NASA Astrophysics Data System (ADS)

    Abdisa Gurmesa, Geshere; Lu, Xiankai; Gundersen, Per; Yunting, Fang; Mo, Jiangming

    2016-04-01

    In this study, we tested the measurement of natural abundance of 15N15N) for its ability to assess changes in N cycling due to increased N deposition in two forest types; namely, an old-growth broadleaved forest and a pine forest, in southern China. We measured δ15N values of inorganic N in input and output fluxes under ambient N deposition, and N concentration and δ15N of major ecosystem compartments under ambient and increased N deposition. Our results showed that N deposition to the forests was 15N-depleted, and was dominated by NH4-N. Plants were 15N-depleted due to imprint from the 15N-depleted atmospheric N deposition. The old-growth forest had larger N concentration and was more 15N-enriched than the pine forest. Nitrogen addition did not significantly affect N concentration, but it significantly increased δ15N values of plants, and slightly more so in the pine forest, toward the 15N signature of the added N in both forests. The result indicates that the pine forest may rely more on the 15N-depleted deposition N. Soil δ15N values were slightly decreased by the N addition. Our result suggests that ecosystem δ15N is more sensitive to the changes in ecosystem N status and N cycling than N concentration in N-saturated sub-tropical forests.

  5. Application of (13)C and (15)N stable isotope probing to characterize RDX degrading microbial communities under different electron-accepting conditions.

    PubMed

    Cho, Kun-Ching; Lee, Do Gyun; Fuller, Mark E; Hatzinger, Paul B; Condee, Charles W; Chu, Kung-Hui

    2015-10-30

    This study identified microorganisms capable of using the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) or its metabolites as carbon and/or nitrogen sources under different electron-accepting conditions using (13)C and (15)N stable isotope probing (SIP). Mesocosms were constructed using groundwater and aquifer solids from an RDX-contaminated aquifer. The mesocosms received succinate as a carbon source and one of four electron acceptors (nitrate, manganese(IV), iron(III), or sulfate) or no additional electron acceptor (to stimulate methanogenesis). When RDX degradation was observed, subsamples from each mesocosm were removed and amended with (13)C3- or ring-(15)N3-, nitro-(15)N3-, or fully-labeled (15)N6-RDX, followed by additional incubation and isolation of labeled nucleic acids. A total of fifteen 16S rRNA sequences, clustering in α- and γ-Proteobacteria, Clostridia, and Actinobacteria, were detected in the (13)C-DNA fractions. A total of twenty seven sequences were derived from different (15)N-DNA fractions, with the sequences clustered in α- and γ-Proteobacteria, and Clostridia. Interestingly, sequences identified as Desulfosporosinus sp. (in the Clostridia) were not only observed to incorporate the labeled (13)C or (15)N from labeled RDX, but also were detected under each of the different electron-accepting conditions. The data suggest that (13)C- and (15)N-SIP can be used to characterize microbial communities involved in RDX biodegradation, and that the dominant pathway of RDX biodegradation may differ under different electron-accepting conditions. PMID:25935409

  6. The Effects of Litter on Littering Behavior in a Forest Environment

    ERIC Educational Resources Information Center

    Crump, S. Larry; And Others

    1977-01-01

    The effects of littered and nonlittered areas on littering behavior were determined in picnic areas in the Uinta National Forest, Utah. Littered and nonlittered conditions were controlled by spreading or removing litter from specified areas. Observations revealed that in the nonlittered areas there was more litter than in the littered areas. (CS)

  7. Mower/Litter Removal

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Burg Corporation needed to get more power out of the suction system in their Vac 'N Bag grass mower/litter remover. The president submitted a problem statement to the Marshall Space Flight Center Technology Transfer Office, which devised a way to guide heavier items of trash to a point where suction was greatest, and made changes to the impeller and the exhaust port, based on rocket propulsion technology. The improved system is used by highway departments, city governments and park authorities, reducing work time by combining the tasks of grass cutting and vacuuming trash and grass clippings.

  8. Use of a 15N tracer to determine linkages between a mangrove and an upland freshwater swamp

    NASA Astrophysics Data System (ADS)

    MacKenzie, R. A.; Cormier, N.

    2005-05-01

    Mangrove forests and adjacent upland freshwater swamps are important components of subsistence-based economies of Pacific islands. Mangroves provide valuable firewood (Rhizophora apiculata) and mangrove crabs (Scylla serrata); intact freshwater swamps are often used for agroforestry (e.g., taro cultivation). While these two systems are connected hydrologically via groundwater and surface flows, little information is available on how they may be biogeochemically or ecologically linked. For example, mangrove leaf litter was once thought to be an important food source for resident and transient nekton and invertebrates, but this value may have been overestimated. Instead, nutrients or allochthonous material (e.g., phytoplankton, detritus) delivered via groundwater or surface water from upland freshwater swamps may play a larger role in mangrove food webs. Understanding the linkages between these two ecologically and culturally important ecosystems will help us to understand the potential impacts of hydrological alterations that occur when roads or bridges are constructed through them. We conducted a 15N tracer study in the Yela watershed on the island of Kosrae, Federated States of Micronesia. K15NO3 was continually added at trace levels for 4 weeks to the Yela River in an upland freshwater swamp adjacent to a mangrove forest. Nitrate and ammonium pools, major primary producers, macroinvertebrates, and fish were sampled from stations 5 m upstream (freshwater swamp) and 138, 188, 213, and 313 m downstream (mangrove) from the tracer addition. Samples were collected once a week prior to, during, and after the 15N addition for a total of 6 weeks. Preliminary results revealed no significant enrichment (< 1 ‰) in the 15N isotope composition of either resident shrimp (Macrobrachium sp.) or mudskipper fish (Periophthalmus sp.). However, the 15N signature of ammonium pools was enriched 10-60 ‰ by the end of the third week. These results suggest that the tracer was present

  9. Conformation of alamethicin in oriented phospholipid bilayers determined by (15)N solid-state nuclear magnetic resonance.

    PubMed Central

    Bak, M; Bywater, R P; Hohwy, M; Thomsen, J K; Adelhorst, K; Jakobsen, H J; Sørensen, O W; Nielsen, N C

    2001-01-01

    The conformation of the 20-residue antibiotic ionophore alamethicin in macroscopically oriented phospholipid bilayers has been studied using (15)N solid-state nuclear magnetic resonance (NMR) spectroscopy in combination with molecular modeling and molecular dynamics simulations. Differently (15)N-labeled variants of alamethicin and an analog with three of the alpha-amino-isobutyric acid residues replaced by alanines have been investigated to establish experimental structural constraints and determine the orientation of alamethicin in hydrated phospholipid (dimyristoylphosphatidylcholine) bilayers and to investigate the potential for a major kink in the region of the central Pro(14) residue. From the anisotropic (15)N chemical shifts and (1)H-(15)N dipolar couplings determined for alamethicin with (15)N-labeling on the Ala(6), Val(9), and Val(15) residues and incorporated into phospholipid bilayer with a peptide:lipid molar ratio of 1:8, we deduce that alamethicin has a largely linear alpha-helical structure spanning the membrane with the molecular axis tilted by 10-20 degrees relative to the bilayer normal. In particular, we find compatibility with a straight alpha-helix tilted by 17 degrees and a slightly kinked molecular dynamics structure tilted by 11 degrees relative to the bilayer normal. In contrast, the structural constraints derived by solid-state NMR appear not to be compatible with any of several model structures crossing the membrane with vanishing tilt angle or the earlier reported x-ray diffraction structure (Fox and Richards, Nature. 300:325-330, 1982). The solid-state NMR-compatible structures may support the formation of a left-handed and parallel multimeric ion channel. PMID:11509381

  10. 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

  11. Quantifying N uptake from the subsoil: A biopore labelling field approach

    NASA Astrophysics Data System (ADS)

    Athmann, Miriam; Beuters, Patrick; Küppers, Paul Martin; Kautz, Timo; Köpke, Ulrich

    2016-04-01

    Enhancing the nutrient acquisition from the subsoil, i.e. the soil below the plough layer, is a resource efficient means to increase crop productivity. Therefore, the subsoil is currently receiving increasing research attention. To assess any individual subsoil's contribution to plant nutrition, it is essential to quantify the share of nutrients derived thereof. This, however, remains challenging, especially under in situ conditions. Compared with topsoils, subsoil bulk is characterized by high penetration resistance and low concentrations of plant available nutrients, thus, rather adverse conditions for root growth. Nevertheless, since subsoils are not disturbed by tillage operations, they are structurally heterogeneous. Large sized biopores generated by plant roots and earthworms provide favorable physical conditions for enhanced rooting. As a result of low penetration resistance, high nutrient concentrations and high microbial activity in the drilosphere, biopores are considered hot spots for subsoil nutrient acquisition. In a field approach on a conventionally managed Haplic Luvisol near Bonn, Germany, we labelled biopore walls in the subsoil with 15N by providing labelled lucerne (Medicago sativa L.) litter to anecic earthworms, and retrieved some of this labelled N in succeeding spring wheat (Triticum aestivum L.) and mallow (Malva sylvestris L.). Even though 15N in pore walls was heterogeneously distributed and 15N contents were elevated not only in biopore walls, but also in the bulk subsoil, our data suggest that the quantity of N derived from the subsoil drilosphere amounted to at least about 40% for mallow and 32% for wheat. These rather high values underline the importance of the subsoil drilosphere for crops' nutrient acquisition at the site under study. The experimental setup is promising, but needs to be further refined to allow precise quantification of N uptake from the different subsoil zones.

  12. Leaf litter and roots as sources of mineral soil organic matter in temperate deciduous forest with and without earthworms

    NASA Astrophysics Data System (ADS)

    Fahey, T.; Yavitt, J. B.

    2012-12-01

    We labeled sugar maple trees with 13C to quantify the separate contributions of decaying leaf litter and root turnover/rhizosphere C flux to mineral soil organic matter (SOM). Labeled leaf litter was applied to forest plots with and without earthworms and recovery of the label in SOM was quantified over three years. In parallel, label recovery was quantified in soils from the labeling chambers where all label was supplied by belowground C flux. In the absence of earthworms about half of the label added as leaf litter remained in the surface organic horizons after three years, with about 3% recovered in mineral SOM. The label was most enriched on silt + clay surfaces, representing precipitation of DOC derived from litter. Earthworms mixed nearly all the leaf litter into mineral soil within one year, and after two years the label was most enriched in particulate organic matter held within soil aggregates produced by worms. After three years 15-20% of the added label was recovered in mineral SOM. In the labeling chambers over 75% of belowground C allocation (BCA) was used in root and rhizosphere respiration in the first year after labeling. We recovered only 3.8% of estimated BCA in SOM after 3 years; however, expressed as a proportion of fine root production plus rhizosphere C flux, this value is 15.4%, comparable to that for leaf litter in the presence of earthworms. In conclusion, both roots and leaf litter contribute significantly to the formation of stabilized mineral SOM in temperate deciduous forests, and this process is profoundly altered by the invasion of lumbricid earthworms.

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

    PubMed Central

    Bengtsson, Göran; Annadotter, Heléne

    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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Denitrification, the reduction of oxidized forms of inorganic N to N2O and N2 is an important pathway of gaseous nitrogen losses. Measuring denitrification, especially the reduction of N2O to N2, expressed in the product ratio (N2O/(N2O + N2)), is rather difficult and hence rarely performed under field conditions. But using the 15N gas-flux method allows determining N transformation processes in their natural environment. In order to develop effective climate mitigation strategies understanding the N2O source is essential. We used the 15N gas-flux method to determine N2O and N2 emissions following grassland renewal and conversion techniques. Therefore we selected three different treatments: control (C), mechanical grassland renovation (GR) (autumn 2013) and grassland conversion to maize (GM) (spring 2014) from field plot trials on two different sites (Histic Gleysoil and Plaggic Anthrosol) near Oldenburg, Lower Saxony, Germany. We applied 15N labeled KNO3- (60 atom. % 15N) at a rate equivalent to common farming practices (150 kg N*ha-1) using needle injection of fertilizer solution in three different depths (10 cm, 15 cm, 20 cm) for homogeneous soil labeling up to 30 cm in microplots. During the first 10 days after application (May 2014) gas flux measurements from closed chambers were performed every second day and then weekly following a period of 8 weeks. Gas samples were analyzed for 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

  16. Leaf δ15N as an indicator of arbuscular mycorrhizal nitrogen uptake in a coastal-plain forest (restinga forest) at Southeastern Brazil

    NASA Astrophysics Data System (ADS)

    Mardegan, S. F.; Valadares, R.; Martinelli, L.

    2013-12-01

    Restinga diversity contrasts with a series of adverse environmental conditions that constrain their development, including nutrient limitation. In this sense, the mutualistic symbiosis between plants and arbuscular mycorrhizal fungi (AMF) may contribute in nutrient acquisition, including nitrogen. However, this association deeply affects plant nitrogen isotopic composition (δ15N), since assimilation processes and biochemical reactions within the fungi may reflect in a delivered product with an isotopic composition about 8 to 10 ‰ lower than that observed at the fungal symbiont per se. Here we assessed if the association with AMF affects δ15N values of plant species from a coastal-plain forest (restinga forest) at Southeastern Brazil. Accordingly, we analyzed the nutritional and isotopic compositions from ecosystem key-compartments (soil, litter and leaves), relating plant δ15N with the colonization rates. The study was carried out in a permanent plot (1 ha) at a coastal-plain forest (restinga forest) at the Serra do Mar State Park, SP, Brazil. Sampled vegetation is characterized by the lack of a well-defined stratification and a rather open canopy. It also comprises trees ranging from 10 to 15-m high. Soils are deep and sandy, being characterized by high acidity, nutrient deficiency and a dense litter cover. We randomly collected five samples (250 mg) from topsoil (0-10 cm) and five to ten leaves from individuals belonging to 16 plant species of high relevance within the site (IVI index). We also collected superficial (0-10 cm depth) fine roots (5 g) and 13 samples (100 g) of fine litter next to the individuals sampled. Soil samples were air-dried, sieved, homogenized and used in the physical-chemical characterization. The remainder was ground to a fine powder to determine nitrogen concentrations and δ15N values. Leaves were dried at 50 °C, finely milled and used for the determination of nitrogen concentrations, C/N ratios and δ15N values. Root samples were

  17. 1H, 13C, and 15N resonance assignments of murine amelogenin, an enamel biomineralization protein.

    SciTech Connect

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

    2008-06-01

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

  18. 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.

  19. Solid-phase peptide synthesis and solid-state NMR spectroscopy of (Ala/sup 3/-/sup 15/N)(Val/sup 1/)gramicidin A

    SciTech Connect

    Fields, G.B.; Fields, C.G.; Petefish, J.; Van Wart, H.E.; Cross, T.A.

    1988-03-01

    (Ala/sup 3-15/N)(Val/sup 1/)Gramicidin A has been prepared by solid-phase peptide synthesis and studied by solid-state /sup 15/N nuclear magnetic resonance spectroscopy. The synthesis of desformyl(Ala/sup 3-15/N)(Val/sup 1/)gramicidin A employed N-hydroxysuccinimide esters of 9-fluorenylmethoxycarbonyl-N/sup ..cap alpha../-amino acids and completely avoided the use of acid. Since deblocking was done with piperidine and the peptide was removed from the resin by treatment with ethanolamine, this synthetic protocol prevented oxidation of the indole rings of this tryptophan-rich peptide and reduced truncations produced by acid hydrolysis. After formylation and purification by anion-exchange and high-pressure liquid chromatography, the peptide was obtained in an overall yield of 30%. Solid-state /sup 15/N nuclear magnetic resonance spectra of this peptide and uniformly labeled (/sup 15/N)gramicidin A' oriented in hydrated lipid bilayers have been obtained, allowing unambiguous assignment of the (/sup 15/N)Ala/sup 3/ resonance in the latter. The solid-state /sup 15/N nuclear magnetic resonance experiments provide evidence that (Val/sup 1/)gramicidin A is rotating about an axis that is perpendicular to the plane of the lipid bilayer and that the N-H axis is nearly parallel with the rotational axis. This study demonstrates that site-specifically labeled (/sup 15/N)gramicidin A analogs prepared by solid-phase peptide synthesis are valuable tools in the study of the solid-state nuclear magnetic resonance spectra of samples in oriented lipid bilayers.

  20. Influence of litter chemistry and stoichiometry on glucan depolymerization during decomposition of beech (Fagus sylvatica L.) litter.

    PubMed

    Leitner, Sonja; Wanek, Wolfgang; Wild, Birgit; Haemmerle, Ieda; Kohl, Lukas; Keiblinger, Katharina M; Zechmeister-Boltenstern, Sophie; Richter, Andreas

    2012-07-01

    Glucans like cellulose and starch are a major source of carbon for decomposer food webs, especially during early- and intermediate-stages of decomposition. Litter quality has previously been suggested to notably influence decomposition processes as it determines the decomposability of organic material and the nutrient availability to the decomposer community. To study the impact of chemical and elemental composition of resources on glucan decomposition, a laboratory experiment was carried out using beech (Fagus sylvatica, L.) litter from four different locations in Austria, differing in composition (concentration of starch, cellulose and acid unhydrolyzable residue or AUR fraction) and elemental stoichiometry (C:N:P ratio). Leaf litter was incubated in mesocosms for six months in the laboratory under controlled conditions. To investigate the process of glucan decomposition and its controls, we developed an isotope pool dilution (IPD) assay using (13)C-glucose to label the pool of free glucose in the litter, and subsequently measured the dilution of label over time. This enabled us to calculate gross rates of glucose production through glucan depolymerization, and glucose consumption by the microbial community. In addition, potential activities of extracellular cellulases and ligninases (peroxidases and phenoloxidases) were measured to identify effects of resource chemistry and stoichiometry on microbial enzyme production. Gross rates of glucan depolymerization and glucose consumption were highly correlated, indicating that both processes are co-regulated and intrinsically linked by the microbial demand for C and energy and thereby to resource allocation to enzymes that depolymerize glucans. At early stages of decomposition, glucan depolymerization rates were correlated with starch content, indicating that starch was the primary source for glucose. With progressing litter decomposition, the correlation with starch diminished and glucan depolymerization rates were

  1. Influence of litter chemistry and stoichiometry on glucan depolymerization during decomposition of beech (Fagus sylvatica L.) litter

    PubMed Central

    Leitner, Sonja; Wanek, Wolfgang; Wild, Birgit; Haemmerle, Ieda; Kohl, Lukas; Keiblinger, Katharina M.; Zechmeister-Boltenstern, Sophie; Richter, Andreas

    2012-01-01

    Glucans like cellulose and starch are a major source of carbon for decomposer food webs, especially during early- and intermediate-stages of decomposition. Litter quality has previously been suggested to notably influence decomposition processes as it determines the decomposability of organic material and the nutrient availability to the decomposer community. To study the impact of chemical and elemental composition of resources on glucan decomposition, a laboratory experiment was carried out using beech (Fagus sylvatica, L.) litter from four different locations in Austria, differing in composition (concentration of starch, cellulose and acid unhydrolyzable residue or AUR fraction) and elemental stoichiometry (C:N:P ratio). Leaf litter was incubated in mesocosms for six months in the laboratory under controlled conditions. To investigate the process of glucan decomposition and its controls, we developed an isotope pool dilution (IPD) assay using 13C-glucose to label the pool of free glucose in the litter, and subsequently measured the dilution of label over time. This enabled us to calculate gross rates of glucose production through glucan depolymerization, and glucose consumption by the microbial community. In addition, potential activities of extracellular cellulases and ligninases (peroxidases and phenoloxidases) were measured to identify effects of resource chemistry and stoichiometry on microbial enzyme production. Gross rates of glucan depolymerization and glucose consumption were highly correlated, indicating that both processes are co-regulated and intrinsically linked by the microbial demand for C and energy and thereby to resource allocation to enzymes that depolymerize glucans. At early stages of decomposition, glucan depolymerization rates were correlated with starch content, indicating that starch was the primary source for glucose. With progressing litter decomposition, the correlation with starch diminished and glucan depolymerization rates were

  2. Environmentally-friendly animal litter

    DOEpatents

    Boxley, Chett; McKelvie, Jessica

    2013-09-03

    An animal litter composition that includes geopolymerized ash particulates having a network of repeating aluminum-silicon units is described herein. Generally, the animal litter is made from a quantity of a pozzolanic ash mixed with an alkaline activator to initiate a geopolymerization reaction that forms geopolymerized ash. This geopolymerization reaction may occur within a pelletizer. After the geopolymerized ash is formed, it may be dried and sieved to a desired size. These geopolymerized ash particulates may be used to make a non-clumping or clumping animal litter or other absorbing material. Aluminum sulfate, clinoptilolite, silica gel, sodium alginate and mineral oil may be added as additional ingredients.

  3. Environmentally-friendly animal litter

    DOEpatents

    Boxley, Chett; McKelvie, Jessica

    2012-08-28

    An animal litter composition including geopolymerized ash particulates having a network of repeating aluminum-silicon units is described herein. Generally, the animal litter is made from a quantity of a pozzolanic ash mixed with a sufficient quantity of water and an alkaline activator to initiate a geopolymerization reaction that forms geopolymerized ash. After the geopolymerized ash is formed, it is dried, broken into particulates, and sieved to a desired size. These geopolymerized ash particulates are used to make a non-clumping or clumping animal litter. Odor control is accomplished with the addition of a urease inhibitor, pH buffer, an odor eliminating agent, and/or fragrance.

  4. Spatial variation in the strength of mutualism between a jumping spider and a terrestrial bromeliad: Evidence from the stable isotope 15N

    NASA Astrophysics Data System (ADS)

    Romero, Gustavo Q.; Vasconcellos-Neto, João; Trivelin, Paulo C. O.

    2008-05-01

    Psecas chapoda, a neotropical jumping spider strictly associated with the terrestrial bromeliad Bromelia balansae in cerrados and semi-deciduous forests in South America, effectively contributes to plant nutrition and growth. In this study, our goal was to investigate if spider density caused spatial variations in the strength of this spider-plant mutualism. We found a positive significant relationship between spider density and δ15N values for bromeliad leaves in different forest fragments. Open grassland Bromeliads were associated with spiders and had higher δ15N values compared to forest bromeliads. Although forest bromeliads had no association with spiders their total N concentrations were higher. These results suggest that bromeliad nutrition is likely more litter-based in forests and more spider-based in open grasslands. This study is one of the few to show nutrient provisioning and conditionality in a spider-plant system.

  5. Subsurface band application of poultry litter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Broiler litter is commonly used as a fertilizer on pastures and cropland. Poultry litter is typically land-applied by broadcasting the litter on the soil surface. Rain falling on soil to which poultry litter has been applied, may carry phosphorus (P) and nitrogen (N) nutrients from the soil into s...

  6. Biochemical Control of Fungal Biomass and Enzyme Production During Native Hawaiian Litter Degradation

    NASA Astrophysics Data System (ADS)

    Amatangelo, K. L.; Cordova, T. P.; Vitousek, P. M.

    2007-12-01

    Microbial growth and enzyme production during decomposition is controlled by the availability of carbon substrates, essential elements, and the ratios of these (such as lignin:N). We manipulated carbon:nutrient stoichiometry during decomposition using a natural fertility gradient in Hawaii and litter of varying initial biochemistry. We collected freshly senesced litter of seven biochemically distinct species from three sites offering differing levels of N, P, cations, and 15N , but similar yearly rainfall and temperature patterns. Litter types were decomposed at both the sites they were collected, and at the other site(s) that species was found. Litter was collected at multiple time points, and after one year of decomposition, calculated K constants varied an order of magnitude, from 0.276 to 2.76. Decomposition rates varied significantly with both litter site of origin and deployment, except at the oldest, P-limited site, where litter site of origin was not significantly correlated with decomposition within species. As microbial exocellular enzymes provide the catalyst for the breakdown of organic molecules including phenols, cellulose, and cutin, we assayed polyphenol oxidase, cellobiohydrolase, cutinase, chitinase, and lignin peroxidase to evaluate the breakdown sequence of different litter types. To measure the fungal biomass accumulating during decomposition, we extracted (22E)-Ergosta-5,7,22-trien-3beta- ol (ergosterol) on a subset of samples. The production of particular exocellular enzymes on litter species responded distinctly to origin and decomposition sites: after six months, chitinase and cellobiohydrolase were significantly affected by origin site, whereas polyphenol oxidase activity was controlled by deployment site. We conclude that site characteristics can alter the interaction between litter carbon:nutrient ratios and decomposition rate, mediated through microbial biomass and enzyme production.

  7. Nitrogen Dynamics in Stream Wood Samples Incubated with [14C]Lignocellulose and Potassium [15N]Nitrate †

    PubMed Central

    Aumen, Nicholas G.; Bottomley, Peter J.; Gregory, Stan V.

    1985-01-01

    Surface wood samples obtained from a Douglas fir log (Pseudotsuga menziesii) in a Pacific Northwest stream were incubated in vitro with [14C]lignocellulose in a defined mineral salts medium supplemented with 10 mg of N liter−1 of 15N-labeled NO3− (50 atom% 15N). Evolution of 14CO2, distribution and isotopic dilution of 15N, filtrate N concentrations, and the rates of denitrification, N2 fixation, and respiration were measured at 6, 12, and 18 days of incubation. The organic N content of the lignocellulose-wood sample mixture had increased from 132 μg of N to a maximum of 231 μg of N per treatment after 6 days of incubation. Rates of [14C]lignocellulose decomposition were greatest during the first 6 days and then began to decline over the remaining 12 days. Total CO2 evolution was also highest at day 6 and declined steadily over the remaining duration of the incubation. Filtrate NH4+-N increased from background levels to a final value of 57 μg of N per treatment. Filtrate NO3− N completely disappeared by day 6, and organic N showed a slight decline between days 12 and 18. The majority of the 15N that could be recovered appeared in the particulate organic fraction by day 6 (41 μg of N), and the filtrate NH4+ N fraction contained 11 μg of 15N by day 18. The 15N enrichment values of the filtrate NH4+ and the inorganic N associated with the particulate fraction had increased to approximately 20 atom% 15N by 18 days of incubation, whereas the particulate organic fraction reached its highest enrichment by day 6. Measurements of N2 fixation and denitrification indicated an insignificant gain or loss of N from the experimental system by these processes. The data show that woody debris in stream ecosystems might function as a rapid and efficient sink for exogenous N, resulting in stimulation of wood decomposition and subsequent activation of other N cycling processes. PMID:16346785

  8. High litter moisture content suppresses litter ammonia volatilization.

    PubMed

    Miles, D M; Rowe, D E; Cathcart, T C

    2011-07-01

    With global food demand expected to increase by 100% in the next 50 yr, urgency to combine comprehensive strategies for sustainable, efficacious, and environmentally sensible agronomic practices has never been greater. One effort for US meat bird management is to reduce NH(3) volatilization from litter to create a better growing environment for the birds, improve production efficiency, retain N in litter for fertilizer value, and negate the detrimental environmental impacts of NH(3) loss to the air. To derive the fundamental effects of temperature and moisture on litter NH(3) volatilization over the range of conditions found in commercial houses, experiments were conducted using commercial broiler litter that had moisture contents of approximately 20 to 55% while controlling temperatures ranging from 18.3 to 40.6°C. Litter samples (100 g) were placed in 1-L containers that received humidified air at approximately 113 mL/min. Volatilized NH(3) in exhaust air was captured in H(3)BO(3) traps. Ammonia loss (log(10) transformation) was modeled via an equation using linear coefficients for temperature and moisture, an interaction term for temperature × moisture, and a quadratic term for moisture. The surface responses resembled parabolic cylinders, indicating a critical moisture level at which NH(3) no longer increases but is diminished as moisture continues to increase. The critical moisture level lies between 37.4 and 51.1% litter moisture, depending on the temperature. An increase in temperature consistently increased NH(3) generation. When the temperature extremes were compared, the maximum NH(3) was up to 7 times greater at 40.6 vs. 18.3°C. The upper moisture limit at which NH(3) release is maximized and subsequently arrested as moisture continues to increase had not been defined previously for commercial broiler litter. The poultry industry and researchers can use these results as a decision tool to enable management strategies that limit NH(3) production. PMID

  9. The effect of noncollinearity of 15N-1H dipolar and 15N CSA tensors and rotational anisotropy on 15N relaxation, CSA/dipolar cross correlation, and TROSY.

    PubMed

    Fushman, D; Cowburn, D

    1999-02-01

    Current approaches to 15N relaxation in proteins assume that the 15N-1H dipolar and 15N CSA tensors are collinear. We show theoretically that, when there is significant anisotropy of molecular rotation, different orientations of the two tensors, experimentally observed in proteins, nucleic acids, and small peptides, will result in differences in site-specific correlation functions and spectral densities. The standard treatments of the rates of longitudinal and transverse relaxation of amide 15N nuclei, of the 15N CSA/15N-1H dipolar cross correlation, and of the TROSY experiment are extended to account for the effect of noncollinearity of the 15N-1H dipolar and 15N CSA (chemical shift anisotropy) tensors. This effect, proportional to the degree of anisotropy of the overall motion, (D parallel/D perpendicular - 1), is sensitive to the relative orientation of the two tensors and to the orientation of the peptide plane with respect to the diffusion coordinate frame. The effect is negligible at small degrees of anisotropy, but is predicted to become significant for D parallel/D perpendicular > or = 1.5, and at high magnetic fields. The effect of noncollinearity of 15N CSA and 15N-1H dipolar interaction is sensitive to both gross (hydrodynamic) properties and atomic-level details of protein structure. Incorporation of this effect into relaxation data analysis is likely to improve both precision and accuracy of the derived characteristics of protein dynamics, especially at high magnetic fields and for molecules with a high degree of anisotropy of the overall motion. The effect will also make TROSY efficiency dependent on local orientation in moderately anisotropic systems.

  10. The economical synthesis of [2'-(13)C, 1,3-(15)N2]uridine; preliminary conformational studies by solid state NMR.

    PubMed

    Patching, Simon G; Middleton, David A; Henderson, Peter J F; Herbert, Richard B

    2003-06-21

    The synthesis of [2'-(13)C, 1,3-(15)N2]uridine 11 was achieved as follows. An epimeric mixture of D-[1-(13)C]ribose 3 and D-[1-(13)C]arabinose 4 was obtained in excellent yield by condensation of K13CN with D-erythrose 2 using a modification of the Kiliani-Fischer synthesis. Efficient separation of the two aldose epimers was pivotally achieved by a novel ion-exchange (Sm3+) chromatography method. D-[2-(13)C]Ribose 5 was obtained from D-[1-(13)C]arabinose 4 using a Ni(II) diamine complex (nickel chloride plus TEMED). Combination of these procedures in a general cycling manner can lead to the very efficient preparation of specifically labelled 13C-monosaccharides of particular chirality. 15N-labelling was introduced in the preparation of [2'-(13)C, 1,3-(15)N2]uridine 11 via [15N2]urea. Cross polarisation magic angle spinning (CP-MAS) solid-state NMR experiments using rotational echo double resonance (REDOR) were carried out on crystals of the labelled uridine to show that the inter-atomic distance between C-2' and N-1 is closely similar to that calculated from X-ray crystallographic data. The REDOR method will be used now to determine the conformation of bound substrates in the bacterial nucleoside transporters NupC and NupG.

  11. 15N Tracing Studies on In Vitro Reactions of Ferredoxin-Dependent Nitrite Reductase and Glutamate Synthase Using Reconstituted Electron Donation Systems.

    PubMed

    Yoneyama, Tadakatsu; Fujimori, Tamaki; Yanagisawa, Shuichi; Hase, Toshiharu; Suzuki, Akira

    2015-06-01

    It is known that plants contain ferredoxin (Fd)-dependent nitrite reductase (NiR) and glutamate synthase (GOGAT). The Fd-NiR reaction produces ammonia from nitrite, and the activity is usually measured by nitrite disappearance. The Fd-GOGAT reaction forms two glutamates of different origin, from glutamine and 2-oxoglutarate, and the activity is measured by the oxidation of reductant (NADPH) or by formation of total glutamate. Here, a quantitative probe of the products and efficiency of the process was conducted using (15)N tracing techniques on these reactions in vitro. We quantified the reduction of (15)N-labeled [Formula: see text] to [Formula: see text] and the formation of [(15)N]glutamate and [(14)N]glutamate from [5-(15)N-amide]glutamine plus 2-oxoglutarate by NiR and GOGAT, respectively, with the reductant-Fd-NADP(+) oxidoreductase (FNR)-Fd system as the sequential electron donors. The supply of dithionite or NADPH to recombinant cyanobacterial NiR led to electron donation system-dependent formation of [(15)N]ammonium from [(15)N]nitrite. Addition of 20 mM NaCl and 20 mM Na-ascorbate accelerated nitrite reduction under high concentrations of NADPH. A sufficient supply of NADPH to recombinant Zea mays Fd-GOGAT generated complete GOGAT activity (transferring the [5-(15)N]amide of glutamine to 2-oxoglutarate to form [(15)N]glutamate), whereas a shortage of NADPH resulted in glutaminase activity only, which removed the amide from glutamine and released ammonia and [(14)N]glutamate. We conclude that although the recombinant Fd-GOGAT enzyme has two forms of glutamate synthesis, the first by glutaminase (ammonia release by glutamine amidotransferase) and the second by glutamate synthase (coupling of the ammonia and exogenously applied 2-oxoglutarate), the first works without NADPH, while the second is strictly dependent on NADPH availability.

  12. Litter chemistry prevails over litter consumers in mediating effects of past steel industry activities on leaf litter decomposition.

    PubMed

    Lucisine, Pierre; Lecerf, Antoine; Danger, Michaël; Felten, Vincent; Aran, Delphine; Auclerc, Apolline; Gross, Elisabeth M; Huot, Hermine; Morel, Jean-Louis; Muller, Serge; Nahmani, Johanne; Maunoury-Danger, Florence

    2015-12-15

    Soil pollution has adverse effects on the performance and life history traits of microorganisms, plants, and animals, yet evidence indicates that even the most polluted sites can support structurally-complex and dynamic ecosystems. The present study aims at determining whether and how litter decomposition, one of the most important soil ecological processes leaf, is affected in a highly trace-metal polluted site. We postulated that past steel mill activities resulting in soil pollution and associated changes in soil characteristics would influence the rate of litter decomposition through two non-exclusive pathways: altered litter chemistry and responses of decomposers to lethal and sub-lethal toxic stress. We carried out a litter-bag experiment using Populus tremula L. leaf litter collected at, and allowed to decompose in, a trace metal polluted site and in three unpolluted sites used as controls. We designed a fully-factorial transplant experimental design to assess effects of litter origin and exposure site on the rate of litter decomposition. We further determined initial litter chemistry, fungal biomass, mesofauna abundance in litter bags, and the soil macrofauna community. Irrespective of the site of litter exposure, litter originating from the polluted site had a two-fold faster decomposition than litter from the unpolluted sites. Litter chemistry, notably the lignin content, seemed most important in explaining the degradation rate of the leaf litter. Abundance of meso and macro-detritivores was higher at the polluted site than at the unpolluted sites. However, litter decomposition proceeded at similar rates in polluted and unpolluted sites. Our results show that trace metal pollution and associated soil and litter changes do not necessarily weaken consumer control on litter decomposition through lethal and sub-lethal toxic stress.

  13. 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.

  14. 15N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose

    USGS Publications Warehouse

    Thorn, K.A.; Kennedy, K.R.

    2002-01-01

    The five major reductive degradation products of TNT-4ADNT (4-amino-2,6-dinitrotoluene), 2ADNT (2-amino-4,6-dinitrotoluene), 2,4DANT (2,4-diamino-6-nitrotoluene), 2,6DANT (2,6-diamino-4-nitrotoluene), and TAT (2,4,6-triaminotoluene)-labeled with 15N in the amine positions, were reacted with the IHSS soil humic acid and analyzed by 15N NMR spectrometry. In the absence of catalysts, all five amines underwent nucleophilic addition reactions with quinone and other carbonyl groups in the soil humic acid to form both heterocyclic and nonheterocyclic condensation products. Imine formation via 1,2-addition of the amines to quinone groups in the soil humic acid was significant with the diamines and TAT but not the monoamines. Horseradish peroxidase (HRP) catalyzed an increase in the incorporation of all five amines into the humic acid. In the case of the diamines and TAT, HRP also shifted the binding away from heterocyclic condensation product toward imine formation. A comparison of quantitative liquid phase with solid-state CP/MAS 15N NMR indicated that the CP experiment underestimated imine and heterocyclic nitrogens in humic acid, even with contact times optimal for observation of these nitrogens. Covalent binding of the mono- and diamines to 4-methylcatechol, the HRP catalyzed condensation of 4ADNT and 2,4DANT to coniferyl alcohol, and the binding of 2,4DANT to lignocellulose with and without birnessite were also examined.

  15. Differentiation of histidine tautomeric states using 15N selectively filtered 13C solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Miao, Yimin; Cross, Timothy A.; Fu, Riqiang

    2014-08-01

    The histidine imidazole ring in proteins usually contains a mixture of three possible tautomeric states (two neutral - τ and π states and a charged state) at physiological pHs. Differentiating the tautomeric states is critical for understanding how the histidine residue participates in many structurally and functionally important proteins. In this work, one dimensional 15N selectively filtered 13C solid-state NMR spectroscopy is proposed to differentiate histidine tautomeric states and to identify all 13C resonances of the individual imidazole rings in a mixture of tautomeric states. When 15N selective 180° pulses are applied to the protonated or non-protonated nitrogen region, the 13C sites that are bonded to the non-protonated or protonated nitrogen sites can be identified, respectively. A sample of 13C, 15N labeled histidine powder lyophilized from a solution at pH 6.3 has been used to illustrate the usefulness of this scheme by uniquely assigning resonances of the neutral τ and charged states from the mixture.

  16. Backbone dynamics of free barnase and its complex with barstar determined by 15N NMR relaxation study.

    PubMed

    Sahu, S C; Bhuyan, A K; Udgaonkar, J B; Hosur, R V

    2000-10-01

    Backbone dynamics of uniformly 15N-labeled free barnase and its complex with unlabelled barstar have been studied at 40 degrees C, pH 6.6, using 15N relaxation data obtained from proton-detected 2D [1H]-15N NMR spectroscopy. 15N spin-lattice relaxation rate constants (R1), spin-spin relaxation rate constants (R2), and steady-state heteronuclear [1H]-15N NOEs have been measured at a magnetic field strength of 14.1 Tesla for 91 residues of free barnase and for 90 residues out of a total of 106 in the complex (excluding three prolines and the N-terminal residue) backbone amide 15N sites of barnase. The primary relaxation data for both the cases have been analyzed in the framework of the model-free formalism using both isotropic and axially symmetric models of the rotational diffusion tensor. As per the latter, the overall rotational correlation times (tau(m)) are 5.0 and 9.5 ns for the free and complexed barnase, respectively. The average order parameter is found to be 0.80 for free barnase and 0.86 for the complex. However, the changes are not uniform along the backbone and for about 5 residues near the binding interface there is actually a significant decrease in the order parameters on complex formation. These residues are not involved in the actual binding. For the residues where the order parameter increases, the magnitudes vary significantly. It is observed that the complex has much less internal mobility, compared to free barnase. From the changes in the order parameters, the entropic contribution of NH bond vector motion to the free energy of complex formation has been calculated. It is apparent that these motion's cause significant unfavorable contributions and therefore must be compensated by many other favorable contributions to effect tight complex formation. The observed variations in the motion and their different locations with regard to the binding interface may have important implications for remote effects and regulation of the enzyme action. PMID

  17. Exogenous proline relieves growth inhibition caused by NaCl in petunia cells: Metabolism of L-( sup 15 M)-proline followed by sup 15 N NMR

    SciTech Connect

    Heyser, J.W.; Chacon, M.J. )

    1989-04-01

    Exogenous proline stimulated the growth of Petunia hybrida cells on 195 mM NaCl 10-fold as compared with cells grown on 195 mM CaCl medium minus proline. L-({sup 15}N)-proline was fed to cells growing on 0 and 195 mM CaCl, and its metabolism was followed by {sup 15}N NMR analysis of cell extracts. Total proline and amino acids were determined by ninhydrin assay. Proline and primary amino acids were easily resolved in NMR spectra and the amount of {sup 15}N-label which remained in proline was determined. Reduced catabolism of proline in cells grown on NaCl was evident. The role of exogenous proline in conferring increased NaCl tolerance in this nonhalophyte will be discussed.

  18. In Vivo Fluxes in the Ammonium-Assimilatory Pathways in Corynebacterium glutamicum Studied by 15N Nuclear Magnetic Resonance

    PubMed Central

    Tesch, M.; de Graaf, A. A.; Sahm, H.

    1999-01-01

    Glutamate dehydrogenase (GDH) and glutamine synthetase (GS)–glutamine 2-oxoglutarate-aminotransferase (GOGAT) represent the two main pathways of ammonium assimilation in Corynebacterium glutamicum. In this study, the ammonium assimilating fluxes in vivo in the wild-type ATCC 13032 strain and its GDH mutant were quantitated in continuous cultures. To do this, the incorporation of 15N label from [15N]ammonium in glutamate and glutamine was monitored with a time resolution of about 10 min with in vivo 15N nuclear magnetic resonance (NMR) used in combination with a recently developed high-cell-density membrane-cyclone NMR bioreactor system. The data were used to tune a standard differential equation model of ammonium assimilation that comprised ammonia transmembrane diffusion, GDH, GS, GOGAT, and glutamine amidotransferases, as well as the anabolic incorporation of glutamate and glutamine into biomass. The results provided a detailed picture of the fluxes involved in ammonium assimilation in the two different C. glutamicum strains in vivo. In both strains, transmembrane equilibration of 100 mM [15N]ammonium took less than 2 min. In the wild type, an unexpectedly high fraction of 28% of the NH4+ was assimilated via the GS reaction in glutamine, while 72% were assimilated by the reversible GDH reaction via glutamate. GOGAT was inactive. The analysis identified glutamine as an important nitrogen donor in amidotransferase reactions. The experimentally determined amount of 28% of nitrogen assimilated via glutamine is close to a theoretical 21% calculated from the high peptidoglycan content of C. glutamicum. In the GDH mutant, glutamate was exclusively synthesized over the GS/GOGAT pathway. Its level was threefold reduced compared to the wild type. PMID:10049869

  19. Ntrace a 15N tracing model to analyse gross N transformations and sources of gaseous N emissions

    NASA Astrophysics Data System (ADS)

    Muller, Christoph

    2013-04-01

    Anthropogenically generated reactive nitrogen (N) cascades throughout the global environment ...(Galloway and Cowling, 2002). This reactive N may be lost from ecosystems via leaching, as nitrate (NO3-), or in gaseous forms such as ammonia and nitrous oxide (N2O) and the loss is governed by the N dynamics of the system. Thus, to be rendered environmentally benign NO3- must be reduced to a non-reactive form, dinitrogen (N2) which requires the evaluation of three major biological pathways of NO3- reduction: i) assimilatory NO3- reduction into biomass, ii) dissimilatory NO3- reduction to NH4+ (DNRA) and iii) dissimilatory NO3- reduction to N2 (denitrification) ...(Burger and Jackson, 2004). Advanced techniques based on 15N tracing in combination with suitable model analyses are the method of choice to analyse complex N interactions and simultaneous N transformation process. Techniques are based on dilution - enrichment principles and usually rely on the simultaneous labelling of various N pools. The data sets are then analysed by suitable 15N tracing models which allow the individual N transformation rates to be calculated based on realistic kinetic settings. The 15N tracing model Ntrace has been developed to analyse the simultaneously occurring N transformation rates in soil-plant systems and includes submodels for the evaluation of the processes associated with gaseous N emissions. The 15N tracing model and some typical model results will be presented. Literature cited .Burger, M., and Jackson, L. E. (2004). Plant and microbial use and turnover: rapid conversion of nitrate to ammonium in soil with roots. Plant and Soil 266, 289-301. Galloway, J. N., and Cowling, E. B. (2002). Reactive nitrogen and the world: 200 years of change. Ambio 31, 64-71. .

  20. Regulation of [15N]urea synthesis from [5-15N]glutamine. Role of pH, hormones, and pyruvate.

    PubMed

    Nissim, I; Yudkoff, M; Brosnan, J T

    1996-12-01

    We have utilized both [5-15N]glutamine and [3-13C] pyruvate as metabolic tracers in order to: (i) examine the effect of pH, glucagon (GLU), or insulin on the precursor-product relationship between 15NH3, [15N]citrulline, and, thereby, [15N]urea synthesis and (ii) elucidate the mechanism(s) by which pyruvate stimulates [15N] urea synthesis. Hepatocytes isolated from rat were incubated at pH 6.8, 7.4, or 7.6 with 1 mM [5-15N]glutamine and 0.1 mM 14NH4Cl in the presence or the absence of [3-13C] pyruvate (2 mM). A separate series of experiments was performed at pH 7.4 in the presence of insulin or GLU. 15NH3 enrichment exceeded or was equal to that of [15N]citrulline under all conditions except for pH 7.6, when the 15N enrichment in citrulline exceeded that in ammonia. The formation of [15N]citrulline (atom % excess) was increased with higher pH. Flux through phosphate-dependent glutaminase (PDG) and [15N]urea synthesis were stimulated (p < 0.05) at pH 7.6 or with GLU and decreased (p < 0.05) at pH 6.8. Insulin had no significant effect on flux through PDG or on [15N]urea synthesis. Decreased [15N]urea production at pH 6.8 was associated with depleted aspartate and glutamate levels. Pyruvate attenuated this decrease in the aspartate and glutamate pools and stimulated [15N]urea synthesis. Production of Asp from pyruvate was increased with increasing medium pH. Approximately 80% of Asp was derived from [3-13C]pyruvate regardless of incubation pH or addition of hormone. Furthermore, approximately 20, 40, and 50% of the mitochondrial N-acetylglutamate (NAG) pool was derived from [3-13C]pyruvate at pH 6.8, 7.4, and 7.6, respectively. Both the concentration and formation of [13C]NAG from [3-13C]pyruvate were increased (p < 0.05) with glucagon and decreased (p < 0.05) with insulin or at pH 6.8. The data suggest a correlation between changes in [15N]urea synthesis and alterations in the level and synthesis of [13C]NAG from pyruvate. The current observations suggest that the

  1. Quantification of the contribution of biological nitrogen fixation to tropical green manure crops and the residual benefit to a subsequent maize crop using 15N-isotope techniques.

    PubMed

    Ramos, M G; Villatoro, M A; Urquiaga, S; Alves, B J; Boddey, R M

    2001-10-01

    In this study the contribution of biological N2 fixation (BNF) to leguminous green manures was quantified in the field at different sites with different 15N methodologies. In the first experiment, conducted on a Terra Roxa soil in Cuba, the BNF contribution to three legumes (Crotalaria juncea, Mucuna aterrima and Canavalia ensiformis) was quantified by applying 15N-labelled ammonium sulphate to the soil. The second experiment was planted in a very low fertility sandy soil near Rio de Janeiro, and the 15N natural abundance technique was applied to quantify BNF in C. juncea, M. niveum and soybean. In both studies the advantages of using several non-N2-fixing reference plants was apparent and despite the much greater accumulation of the C. juncea in the experiment performed on the fertile soil of Cuba, the above ground contributions of BNF at both sites were similar (40-80 kg N x ha(-1)) and greater than for the other legumes. In a further experiment the possible contribution of root-derived N to the soil/plant system of two of the legumes was quantified using a 15N-leaf-labelling technique performed in pots. The results of this study suggested that total below-ground N could constitute as much as 39 to 49% of the total N accumulated by the legume crops. PMID:11566383

  2. Preferential flow, nitrogen transformations and 15N balance under urine-affected areas of irrigated and non-irrigated clover-based pastures

    NASA Astrophysics Data System (ADS)

    Pakro, Naser; Dillon, Peter

    1995-12-01

    Urine-affected areas can lead to considerable losses of N by leaching, ammonia volatilisation and denitrification from dairy pastures in the southeast of South Australia. Potable groundwater supplies are considered to have become contaminated by nitrate as a result of leaching from these leguminous pastures. Dairy cow urine, labelled with 15N urea, was applied to micro-plots and mini-lysimeters installed in two adjacent irrigated (white clover-rye grass) and non-irrigated (subterranean clover-annual grasses) paddocks of a dairy farm on four occasions representing different seasonal conditions. These experiments allowed measurement of nitrogen transformations, recovery of 15N in the pasture and soil, and leaching below various depths. Gaseous losses were calculated from the nitrogen balance. The results of the four experiments showed that within a day of urine application up to 40% of the applied urinary-N was leached below a depth of 150 mm as a result of macropore flow in the irrigated paddock, and up to 24% in the non-irrigated one. After application to the irrigated paddock 17% of the urinary-N moved immediately below 300 mm but only 2% below the 450-mm depth. The urinary-N remaining in the soil was converted from urea to ammonium within a day regardless of season. Within the first 7 days of application six times more nitrate was produced in summer than in winter. This has obvious implications for leaching potential. Leaching of 15N from the top 150 mm of soil, following urine applications in all seasons, was between 41% and 62% of the applied 15N in the irrigated paddock and 25-51% in the non-irrigated paddock. However, leaching losses measured at depths of 300 or 450 mm were smaller by a factor of 2-4. The leaching loss of 15N applied in spring in both paddocks was 41% below 150 mm and 12% below 450 mm. Recovery of 15N from the soil-plant system in the 450-nm deep lysimeters was ˜60% of that applied. Estimated ammonia was ˜9% of applied 15N with no paddock

  3. Decomposition of diverse litter mixtures in streams.

    PubMed

    Lecerf, Antoine; Risnoveanu, Geta; Popescu, Cristina; Gessner, Mark O; Chauvet, Eric

    2007-01-01

    In view of growing interest in understanding how biodiversity affects ecosystem functioning, we investigated effects of riparian plant diversity on litter decomposition in forest streams. Leaf litter from 10 deciduous tree species was collected during natural leaf fall at two locations (Massif Central in France and Carpathians in Romania) and exposed in the field in litter bags. There were 35 species combinations, with species richness ranging 1-10. Nonadditive effects on the decomposition of mixed-species litter were minor, although a small synergistic effect was observed in the Massif Central stream where observed litter mass remaining was significantly lower overall than expected from data on single-species litter. In addition, variability in litter mass remaining decreased with litter diversity at both locations. Mean nitrogen concentration of single- and mixed-species litters (0.68-4.47% of litter ash-free dry mass) accounted for a large part of the variation in litter mass loss across species combinations. For a given species or mixture, litter mass loss was also consistently faster in the Massif Central than in the Carpathians, and the similarity in general stream characteristics, other than temperature, suggests that this effect was largely due to differences in thermal regimes. These results support the notion that decomposition of litter mixtures is primarily driven by litter quality and environmental factors, rather than by species richness per se. However, the observed consistent decrease in variability of decomposition rate with increasing plant species richness indicates that conservation of riparian tree diversity is important even when decomposition rates are not greatly influenced by litter mixing.

  4. Variability of the 15N Chemical Shielding Tensors in the B3 Domain of Protein G from 15N Relaxation Measurements at Several Fields

    PubMed Central

    Hall, Jennifer B.; Fushman, David

    2008-01-01

    We applied a combination of 15N relaxation and CSA/dipolar cross-correlation measurements at five magnetic fields (9.4, 11.7, 14.1, 16.4, and 18.8 Tesla) to determine the 15N chemical shielding tensors for backbone amides in protein G in solution. The data were analyzed using various model-independent approaches and those based on Lipari-Szabo approximation, all of them yielding similar results. The results indicate a range of site-specific values of the anisotropy (CSA) and orientation of the 15N chemical shielding tensor, similar to those in ubiquitin. Assuming a Gaussian distribution of the 15N CSA values, the mean anisotropy is -173.9 to -177.2 ppm (for 1.02-Å NH-bond length) and the site-so-site CSA variability is ±17.6 to ±21.4 ppm, depending on the method used. This CSA variability is significantly larger than derived previously for ribonuclease H or recently, using “meta-analysis” for ubiquitin. Standard interpretation of 15N relaxation studies of backbone dynamics in proteins involves an a priori assumption of a uniform 15N CSA. We show that this assumption leads to a significant discrepancy between the order parameters obtained at different fields. Using the site-specific CSAs obtained from our study removes this discrepancy and allows simultaneous fit of relaxation data at all five fields to Lipari-Szabo spectral densities. These findings emphasize the necessity of taking into account the variability of 15N CSA for accurate analysis of protein dynamics from 15N relaxation measurements. PMID:16771499

  5. /sup 15/N-Ammonia assimilation, 2-oxoglutarate transport, and glutamate export in spinach chloroplasts in the presence of dicarboxylates in the light

    SciTech Connect

    Woo, K.C.; Boyle, F.A.; Flugge, I.U.; Heldt, H.W.

    1987-11-01

    The direct incorporation of /sup 15/NH/sub 4/Cl into amino acids in illuminated spinach (Spinacia oleracea L.) chloroplasts in the presence of 2-oxoglutarate plus malate was determined. The amido-N of glutamine was the most highly labeled N-atom during /sup 15/NH/sub 4/ assimilation in the presence of malate. In 4 minutes the /sup 15/N-label of the amido-N of glutamine was 37% enriched. In contrast, values obtained for both the N-atom of glutamate and the amino-N of glutamine were only about 20% while that of the N-atom of aspartate was only 3%. The addition of malate during the assimilation of /sup 15/NH/sub 4/Cl and Na/sup 15/NO/sub 2/ greatly increased the /sup 15/N-label into glutamine but did not qualitatively change the order of the incorporation of /sup 15/N-label into all the amino acids examined. This evidence indicates the direct involvement of the glutamine synthetase/glutamate synthase pathway for ammonia and nitrite assimilation in isolated chloroplasts. The addition of malate or succinate during ammonia assimilation also led to more than 3-fold increase in (/sup 14/C)2-oxoglutarate transport into the chloroplast as well as an increase in the export of (/sup 14/C)glutamate out of the chloroplast. Little (/sup 14/C)glutamine was detected in the medium of the chloroplast preparations. The stimulation of /sup 15/N-incorporation and (/sup 14/C)glutamate export by malate could be directly attributed to the increase in 2-oxoglutarate transport activity (via the 2-oxoglutarate translocator) observed in the presence of exogenous malate.

  6. The abiotic litter decomposition in the drylands

    NASA Astrophysics Data System (ADS)

    Lee, H.; Throop, H.; Rahn, T. A.

    2009-12-01

    The decomposition of litter is an important ecosystem function that controls carbon and nutrient cycling, which is well understood from the relationship between temperature and moisture. However, the decomposition in the arid and semiarid environments (hereafter drylands) is relatively poorly predicted due to several abiotic factors such as the effect of ultraviolet radiation and physical mixing of fallen litter with soil. The relative magnitude of these abiotic factors to ecosystem scale litter decomposition is still in debate. Here, we examine the effect of two major abiotic factors in the drylands litter decomposition by conducting a controlled laboratory study using plant litter and soil collected from Sonoran and Chihuahuan desert areas. The first part of the experiment focused on the effect of soil-litter mixing. We established a complete block design of three levels of soil and litter mixing (no mixing, light soil-litter mixing, and complete soil-litter mixing) in combination with three levels of soil moisture (1%, 2%, and 6% volumetric water content) using 2g of two most dominant species litter, grass and mesquite, and 50g of air-dried soils in 500ml mason jar and incubated them under 25C. We measured CO2 fluxes from these soil-litter incubations and harvested the soil and litter at 0, 1, 2, 4, 8, and 16 weeks and analyzed them of carbon and nitrogen content as well as the actual mass loss in the litter. The second part of the experiment focused on the effect of ultraviolet radiation. We established short-term litter incubation on a quartz chamber and used different temperature, moisture, and minerals to find the mechanism of photodegradation of litter. We measured CO2 fluxes from the litter incubation under ultraviolet radiation and also measured 13CO2 from these emissions. We were able to detect changes in the rate of carbon mineralization as a result of our treatments in the first week of soil-litter mixing experiment. The carbon mineralization rate was

  7. Climate and litter quality differently modulate the effects of soil fauna on litter decomposition across biomes.

    PubMed

    García-Palacios, Pablo; Maestre, Fernando T; Kattge, Jens; Wall, Diana H

    2013-08-01

    Climate and litter quality have been identified as major drivers of litter decomposition at large spatial scales. However, the role played by soil fauna remains largely unknown, despite its importance for litter fragmentation and microbial activity. We synthesised litterbag studies to quantify the effect sizes of soil fauna on litter decomposition rates at the global and biome scales, and to assess how climate, litter quality and soil fauna interact to determine such rates. Soil fauna consistently enhanced litter decomposition at both global and biome scales (average increment ~ 37%). [corrected]. However, climate and litter quality differently modulated the effects of soil fauna on decomposition rates between biomes, from climate-driven biomes to those where climate effects were mediated by changes in litter quality. Our results advocate for the inclusion of biome-specific soil fauna effects on litter decomposition as a mean to reduce the unexplained variation in large-scale decomposition models.

  8. Climate and litter quality differently modulate the effects of soil fauna on litter decomposition across biomes

    PubMed Central

    García-Palacios, Pablo; Maestre, Fernando T.; Kattge, Jens; Wall, Diana H.

    2015-01-01

    Climate and litter quality have been identified as major drivers of litter decomposition at large spatial scales. However, the role played by soil fauna remains largely unknown, despite its importance for litter fragmentation and microbial activity. We synthesized litterbag studies to quantify the effect sizes of soil fauna on litter decomposition rates at the global and biome scales, and to assess how climate, litter quality and soil fauna interact to determine such rates. Soil fauna consistently enhanced litter decomposition at both global and biome scales (average increment ~27%). However, climate and litter quality differently modulated the effects of soil fauna on decomposition rates between biomes, from climate-driven biomes to those where climate effects were mediated by changes in litter quality. Our results advocate for the inclusion of biome-specific soil fauna effects on litter decomposition as a mean to reduce the unexplained variation in large-scale decomposition models. PMID:23763716

  9. 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

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

    PubMed

    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.

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

    PubMed

    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

  12. Measurement of broiler litter production rates and nutrient content using recycled litter.

    PubMed

    Coufal, C D; Chavez, C; Niemeyer, P R; Carey, J B

    2006-03-01

    It is important for broiler producers to know litter production rates and litter nutrient content when developing nutrient management plans. Estimation of broiler litter production varies widely in the literature due to factors such as geographical region, type of housing, size of broiler produced, and number of flocks reared on the same litter. Published data for N, P, and K content are also highly variable. In addition, few data are available regarding the rate of production, characteristics, and nutrient content of caked litter (cake). In this study, 18 consecutive flocks of broilers were reared on the same litter in experimental pens under simulated commercial conditions. The mass of litter and cake produced was measured after each flock. Samples of all litter materials were analyzed for pH, moisture, N, P, and K. Average litter and cake moisture content were 26.4 and 46.9%, respectively. Significant variation in litter and cake nutrient content was observed and can largely be attributed to ambient temperature differences. Average litter, cake, and total litter (litter plus cake) production rates were 153.3, 74.8, and 228.2 g of dry litter material per kg of live broiler weight (g/kg) per flock, respectively. Significant variation in litter production rates among flocks was also observed. Cumulative litter, cake, and total litter production rates after 18 flocks were 170.3, 78.7, and 249.0 g/kg, respectively. The data produced from this research can be used by broiler producers to estimate broiler litter and cake production and the nutrient content of these materials.

  13. Patterns of 15N assimilation and growth of methanotrophic ANME-2 archaea and sulfate-reducing bacteria within structured syntrophic consortia revealed by FISH-SIMS.

    PubMed

    Orphan, Victoria J; Turk, Kendra A; Green, Abigail M; House, Christopher H

    2009-07-01

    Methane release from the oceans is controlled in large part by syntrophic interactions between anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (DSS), frequently found as organized consortia. An understanding of the specifics of this symbiotic relationship and the metabolic heterogeneity existing between and within individual methane-oxidizing aggregates is currently lacking. Here, we use the microanalytical method FISH-SIMS (fluorescence in situ hybridization-secondary ion mass spectrometry) to describe the physiological traits and anabolic activity of individual methanotrophic consortia, specifically tracking (15)N-labelled protein synthesis to examine the effects of organization and size on the metabolic activity of the syntrophic partners. Patterns of (15)N distribution within individual aggregates showed enhanced (15)N assimilation in ANME-2 cells relative to the co-associated DSS revealing a decoupling in anabolic activity between the partners. Protein synthesis in ANME-2 cells was sustained throughout the core of individual ANME-2/DSS consortia ranging in size range from 4 to 20 μm. This indicates that metabolic activity of the methane-oxidizing archaea is not limited to, or noticeably enhanced at the ANME-2/DSS boundary. Overall, the metabolic activity of both syntrophic partners within consortia was greater than activity measured in representatives of the ANME-2 and DSS observed alone, with smaller ANME-2/DSS aggregates displaying a tendency for greater (15)N uptake and doubling times ranging from 3 to 5 months. The combination of (15)N-labelling and FISH-SIMS provides an important perspective on the extent of heterogeneity within methanotrophic aggregates and may aid in constraining predictive models of activity and growth by these syntrophic consortia.

  14. 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 ...

  15. 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...

  16. Human dietary δ(15)N intake: representative data for principle food items.

    PubMed

    Huelsemann, F; Koehler, K; Braun, H; Schaenzer, W; Flenker, U

    2013-09-01

    Dietary analysis using δ(15)N values of human remains such as bone and hair is usually based on general principles and limited data sets. Even for modern humans, the direct ascertainment of dietary δ(15)N is difficult and laborious, due to the complexity of metabolism and nitrogen fractionation, differing dietary habits and variation of δ(15)N values of food items. The objective of this study was to summarize contemporary regional experimental and global literature data to ascertain mean representative δ(15)N values for distinct food categories. A comprehensive data set of more than 12,000 analyzed food samples was summarized from the literature. Data originated from studies dealing with (1) authenticity tracing or origin control of food items, and (2) effects of fertilization or nutrition on δ(15)N values of plants or animals. Regional German food δ(15)N values revealed no major differences compared with the mean global values derived from the literature. We found that, in contrast to other food categories, historical faunal remains of pig and poultry are significantly enriched in (15)N compared to modern samples. This difference may be due to modern industrialized breeding practices. In some food categories variations in agricultural and feeding regimens cause significant differences in δ(15)N values that may lead to misinterpretations when only limited information is available.

  17. 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…

  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. δ(15) N from soil to wine in bulk samples and proline.

    PubMed

    Paolini, Mauro; Ziller, Luca; Bertoldi, Daniela; Bontempo, Luana; Larcher, Roberto; Nicolini, Giorgio; Camin, Federica

    2016-09-01

    The feasibility of using δ(15) N as an additional isotopic marker able to link wine to its area of origin was investigated. The whole production chain (soil-leaves-grape-wine) was considered. Moreover, the research included evaluation of the effect of the fermentation process, the use of different types of yeast and white and red vinification, the addition of nitrogen adjuvants and ultrasound lysis simulating wine ageing. The δ(15) N of grapes and wine was measured in bulk samples and compounds, specifically in proline, for the first time. Despite isotopic fractionation from soil to wine, the δ(15) N values of leaves, grapes, wine and particularly must and wine proline conserved the variability of δ(15) N in the growing soil. Fermentation and ultrasound treatment did not affect the δ(15) N values of grape must, which was therefore conserved in wine. The addition of inorganic or organic adjuvants was able to influence the δ(15) N of bulk wine, depending on the amount and the difference between the δ(15) N of must and that of the adjuvant. The δ(15) N of wine proline was not influenced by adjuvant addition and is therefore the best marker for tracing the geographical origin of wine. Copyright © 2016 John Wiley & Sons, Ltd.

  20. δ(15) N from soil to wine in bulk samples and proline.

    PubMed

    Paolini, Mauro; Ziller, Luca; Bertoldi, Daniela; Bontempo, Luana; Larcher, Roberto; Nicolini, Giorgio; Camin, Federica

    2016-09-01

    The feasibility of using δ(15) N as an additional isotopic marker able to link wine to its area of origin was investigated. The whole production chain (soil-leaves-grape-wine) was considered. Moreover, the research included evaluation of the effect of the fermentation process, the use of different types of yeast and white and red vinification, the addition of nitrogen adjuvants and ultrasound lysis simulating wine ageing. The δ(15) N of grapes and wine was measured in bulk samples and compounds, specifically in proline, for the first time. Despite isotopic fractionation from soil to wine, the δ(15) N values of leaves, grapes, wine and particularly must and wine proline conserved the variability of δ(15) N in the growing soil. Fermentation and ultrasound treatment did not affect the δ(15) N values of grape must, which was therefore conserved in wine. The addition of inorganic or organic adjuvants was able to influence the δ(15) N of bulk wine, depending on the amount and the difference between the δ(15) N of must and that of the adjuvant. The δ(15) N of wine proline was not influenced by adjuvant addition and is therefore the best marker for tracing the geographical origin of wine. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27479606

  1. Alkaline Hydrolysis/Polymerization of 2,4,6-Trinitrotoluene: Characterization of Products by 13C and 15N NMR

    USGS Publications Warehouse

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

    2004-01-01

    Alkaline hydrolysis has been investigated as a nonbiological procedure for the destruction of 2,4,6-trinitrotoluene (TNT) in explosives contaminated soils and munitions scrap. Nucleophilic substitutions of the nitro and methyl groups of TNT by hydroxide ion are the initial steps in the alkaline degradation of TNT. Potential applications of the technique include both in situ surface liming and ex situ alkaline treatment of contaminated soils. A number of laboratory studies have reported the formation of an uncharacterized polymeric material upon prolonged treatment of TNT in base. As part of an overall assessment of alkaline hydrolysis as a remediation technique, and to gain a better understanding of the chemical reactions underlying the hydrolysis/polymerization process, the soluble and precipitate fractions of polymeric material produced from the calcium hydroxide hydrolysis of unlabeled and 15N-labeled TNT were analyzed by elemental analysis and 13C and 15N nuclear magnetic resonance spectroscopy. Spectra indicated that reactions leading to polymerization included nucleophilic displacement of nitro groups by hydroxide ion, formation of ketone, carboxyl, alcohol, ether, and other aliphatic carbons, conversion of methyl groups to diphenyl methylene carbons, and recondensation of aromatic amines and reduced forms of nitrite, including ammonia and possibly hydroxylamine, into the polymer. Compared to the distribution of carbons in TNT as 14% sp 3- and 86% sp2-hybridized, the precipitate fraction from hydrolysis of unlabeled TNT contained 33% sp3- and 67% sp 2-hybridized carbons. The concentration of nitrogen in the precipitate was 64% of that in TNT. The 15N NMR spectra showed that, in addition to residual nitro groups, forms of nitrogen present in the filtrate and precipitate fractions include aminohydroquinone, primary amide, indole, imine, and azoxy, among others. Unreacted nitrite was recovered in the filtrate fraction. The toxicities and susceptibilities to

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

    PubMed

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

    2014-06-01

    Amino acid δ(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 Lauchstädt, Germany, were determined by GC-C-IRMS. Manuring was found to result in a consistent (15)N-enrichment of cereal grain amino acid δ(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 δ(15)N values with manuring is therefore due to a (15)N-enrichment in the δ(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 δ(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 δ(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.

  4. 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.

  5. A Novel [15N] Glutamine Flux using LC-MS/MS-SRM for Determination of Nucleosides and Nucleobases

    PubMed Central

    Jin, Feng; Bhowmik, Salil Kumar; Putluri, Vasanta; Gu, Franklin; Gohlke, Jie; Von Rundstedt, Friedrich Carl; Dasgupta, Subhamoy; Krishnapuram, Rashmi; O’Malley, Bert W.; Sreekumar, Arun; Putluri, Nagireddy

    2016-01-01

    The growth of cancer cells relies more on increased proliferation and autonomy compared to non-malignant cells. The rate of de novo nucleotide biosynthesis correlates with cell proliferation rates. In part, glutamine is needed to sustain high rates of cellular proliferation as a key nitrogen donor in purine and pyrimidine nucleotide biosynthesis. In addition, glutamine serves as an essential substrate for key enzymes involved in the de novo synthesis of purine and pyrimidine nucleotides. Here, we developed a novel liquid chromatography (LC-MS) to quantify glutamine-derived [15N] nitrogen flux into nucleosides and nucleobases (purines and pyrimidines). For this, DNA from 5637 bladder cancer cell line cultured in 15N labelled glutamine and then enzymatically hydrolyzed by sequential digestion. Subsequently, DNA hydrolysates were separated by LC-MS and Selected Reaction Monitoring (SRM) was employed to identify the nucleobases and nucleosides. Thus, high sensitivity and reproducibility of the method make it a valuable tool to identify the nitrogen flux primarily derived from glutamine and can be further adaptable for high throughput analysis of large set of DNA in a clinical setting. PMID:27158554

  6. Effects of trichloroacetic acid on the nitrogen metabolism of Pinus sylvestris--a 13C/15N tracer study.

    PubMed

    Hafner, Christoph; Jung, Klaus; Schüürmann, Gerrit

    2002-01-01

    Trichloroacetic acid (TCA) can be found in various environmental compartments like air, rain and plants all over the world. It is assumed that TCA is an atmospheric degradation product of volatile chloroorganic hydrocarbons. The herbicide effect of TCA in higher concentrations is well known, but not much is known about the phytotoxic effects in environmentally relevant concentrations. It can be shown in this study by using the 13C/15N stable isotope tracer technique that [13C]TCA is taken up by roots of two-year-old seedlings of Pinus sylvestris L. and transported into the needles. At the same time the effect of the substance on nitrogen metabolism can be analyzed by measuring the incorporation of 15NO3- into different nitrogen fractions of the plant. The more [13C]TCA incorporation, the higher the synthesis of 15N labelled amino acids and proteins is. These effects on the nitrogen metabolism are probably based on the activation of stress- and detoxification metabolism. It has to be assumed that there is an influence on N metabolism of Pinus sylvestris caused by the deposition of environmentally relevant TCA concentrations.

  7. Sequential monitoring of beach litter using webcams.

    PubMed

    Kako, Shin'ichiro; Isobe, Atsuhiko; Magome, Shinya

    2010-05-01

    This study attempts to establish a system for the sequential monitoring of beach litter using webcams placed at the Ookushi beach, Goto Islands, Japan, to establish the temporal variability in the quantities of beach litter every 90 min over a one and a half year period. The time series of the quantities of beach litter, computed by counting pixels with a greater lightness than a threshold value in photographs, shows that litter does not increase monotonically on the beach, but fluctuates mainly on a monthly time scale or less. To investigate what factors influence this variability, the time derivative of the quantity of beach litter is compared with satellite-derived wind speeds. It is found that the beach litter quantities vary largely with winds, but there may be other influencing factors. PMID:20392465

  8. Enhancement of broiler litter to improve the fertilizer quality of litter

    SciTech Connect

    Ransom, J.M.; Strickland, R.C.

    1992-12-01

    This document presents efforts to utilize poultry litter for feed, fertilizer, and soil amendments. Historical and programmatic efforts by TVA are discussed. Current methods of drying and pelleting the litter, along with more direct methods of composting are reported.

  9. Enhancement of broiler litter to improve the fertilizer quality of litter

    SciTech Connect

    Ransom, J.M.; Strickland, R.C.

    1992-01-01

    This document presents efforts to utilize poultry litter for feed, fertilizer, and soil amendments. Historical and programmatic efforts by TVA are discussed. Current methods of drying and pelleting the litter, along with more direct methods of composting are reported.

  10. The Effect of N Fertilizer Placement on the Fate of Urea-15N and Yield of Winter Wheat in Southeast China

    PubMed Central

    Chen, Zhaoming; Wang, Huoyan; Liu, Xiaowei; Liu, Yongzhe; Gao, Shuaishuai; Zhou, Jianmin

    2016-01-01

    A field micro-plot experiment using nitrogen isotope (15N) labeling was conducted to determine the effects of placement methods (broadcast and band) and N rates (60, 150 and 240 kg ha–1) on the fate of urea-15N in the wheat–soil system in Guangde County of Anhui Province, China. N fertilizer applied in bands increased grain yield by 15% compared with broadcast application. The N fertilizer application rate had a significant effect on grain yield, straw yield and aboveground biomass, as well as on N uptake and N concentration of wheat. The recovery of urea-15N was a little higher for broadcast (34.0–39.0%) than for band treatment (31.2–38.2%). Most of the soil residual N was retained in the 0–20 cm soil layer. At the N rates of 60 and 240 kg ha–1, the residual 15N was higher for band (34.4 and 108.7 kg ha–1, respectively) than for broadcast application (29.6 and 88.4 kg ha–1, respectively). Compared with broadcast treatment, banded placement of N fertilizer decreased the N loss in the wheat–soil system. Band application one time is an alternative N management practice for winter wheat in this region. PMID:27082246

  11. Pathways of nitrogen assimilation in cowpea nodules studied using /sup 15/N/sub 2/ and allopurinol. [Vigna unguiculata L. Walp. cv Vita

    SciTech Connect

    Atkins, C.A.; Storer, P.J.; Pate, J.S.

    1988-01-01

    In the presence of 0.5 millimolar allopurinol (4-hydroxypyrazolo (3,4-d)pyrimidine), an inhibitor of NAD:xanthine oxidoreductase (EC 1.2.3.2), intact attached nodules of cowpea (vigna unguiculata L. Walp. cv Vita 3) formed (/sup 15/N)xanthine from /sup 15/N/sub 2/ at rates equivalent to those of ureide synthesis, confirming the direct assimilation of fixed nitrogen into purines. Xanthine accumulated in nodules and was exported in increasing amounts in xylem of allopurinol-treated plants. Other intermediates of purine oxidation, de novo purine synthesis, and ammonia assimilation did not increase and, over the time course of experiments (4 hours), allopurinol had no effect on nitrogenase (EC 1.87.99.2) activity. Negligible /sup 15/N -labeling of asparagine from /sup 15/N/sub 2/ was observed, suggesting that the significant pool (up to 14 micromoles per gram of nodule fresh weight) of this amide in cowpea nodules was not formed directly from fixation but may have accumulated as a consequence of phloem delivery.

  12. Tracing the Cycling and Fate of the Explosive 2,4,6-Trinitrotoluene in Coastal Marine Systems with a Stable Isotopic Tracer, (15)N-[TNT].

    PubMed

    Smith, Richard W; Vlahos, Penny; Böhlke, J K; Ariyarathna, Thivanka; Ballentine, Mark; Cooper, Christopher; Fallis, Stephen; Groshens, Thomas J; Tobias, Craig

    2015-10-20

    2,4,6-Trinitrotoluene (TNT) has been used as a military explosive for over a hundred years. Contamination concerns have arisen as a result of manufacturing and use on a large scale; however, despite decades of work addressing TNT contamination in the environment, its fate in marine ecosystems is not fully resolved. Here we examine the cycling and fate of TNT in the coastal marine systems by spiking a marine mesocosm containing seawater, sediments, and macrobiota with isotopically labeled TNT ((15)N-[TNT]), simultaneously monitoring removal, transformation, mineralization, sorption, and biological uptake over a period of 16 days. TNT degradation was rapid, and we observed accumulation of reduced transformation products dissolved in the water column and in pore waters, sorbed to sediments and suspended particulate matter (SPM), and in the tissues of macrobiota. Bulk δ(15)N analysis of sediments, SPM, and tissues revealed large quantities of (15)N beyond that accounted for in identifiable derivatives. TNT-derived N was also found in the dissolved inorganic N (DIN) pool. Using multivariate statistical analysis and a (15)N mass balance approach, we identify the major transformation pathways of TNT, including the deamination of reduced TNT derivatives, potentially promoted by sorption to SPM and oxic surface sediments.

  13. The Effect of N Fertilizer Placement on the Fate of Urea-15N and Yield of Winter Wheat in Southeast China.

    PubMed

    Chen, Zhaoming; Wang, Huoyan; Liu, Xiaowei; Liu, Yongzhe; Gao, Shuaishuai; Zhou, Jianmin

    2016-01-01

    A field micro-plot experiment using nitrogen isotope (15N) labeling was conducted to determine the effects of placement methods (broadcast and band) and N rates (60, 150 and 240 kg ha-1) on the fate of urea-15N in the wheat-soil system in Guangde County of Anhui Province, China. N fertilizer applied in bands increased grain yield by 15% compared with broadcast application. The N fertilizer application rate had a significant effect on grain yield, straw yield and aboveground biomass, as well as on N uptake and N concentration of wheat. The recovery of urea-15N was a little higher for broadcast (34.0-39.0%) than for band treatment (31.2-38.2%). Most of the soil residual N was retained in the 0-20 cm soil layer. At the N rates of 60 and 240 kg ha-1, the residual 15N was higher for band (34.4 and 108.7 kg ha-1, respectively) than for broadcast application (29.6 and 88.4 kg ha-1, respectively). Compared with broadcast treatment, banded placement of N fertilizer decreased the N loss in the wheat-soil system. Band application one time is an alternative N management practice for winter wheat in this region. PMID:27082246

  14. Tracing the Cycling and Fate of the Explosive 2,4,6-Trinitrotoluene in Coastal Marine Systems with a Stable Isotopic Tracer, (15)N-[TNT].

    PubMed

    Smith, Richard W; Vlahos, Penny; Böhlke, J K; Ariyarathna, Thivanka; Ballentine, Mark; Cooper, Christopher; Fallis, Stephen; Groshens, Thomas J; Tobias, Craig

    2015-10-20

    2,4,6-Trinitrotoluene (TNT) has been used as a military explosive for over a hundred years. Contamination concerns have arisen as a result of manufacturing and use on a large scale; however, despite decades of work addressing TNT contamination in the environment, its fate in marine ecosystems is not fully resolved. Here we examine the cycling and fate of TNT in the coastal marine systems by spiking a marine mesocosm containing seawater, sediments, and macrobiota with isotopically labeled TNT ((15)N-[TNT]), simultaneously monitoring removal, transformation, mineralization, sorption, and biological uptake over a period of 16 days. TNT degradation was rapid, and we observed accumulation of reduced transformation products dissolved in the water column and in pore waters, sorbed to sediments and suspended particulate matter (SPM), and in the tissues of macrobiota. Bulk δ(15)N analysis of sediments, SPM, and tissues revealed large quantities of (15)N beyond that accounted for in identifiable derivatives. TNT-derived N was also found in the dissolved inorganic N (DIN) pool. Using multivariate statistical analysis and a (15)N mass balance approach, we identify the major transformation pathways of TNT, including the deamination of reduced TNT derivatives, potentially promoted by sorption to SPM and oxic surface sediments. PMID:26375037

  15. The Effect of N Fertilizer Placement on the Fate of Urea-15N and Yield of Winter Wheat in Southeast China.

    PubMed

    Chen, Zhaoming; Wang, Huoyan; Liu, Xiaowei; Liu, Yongzhe; Gao, Shuaishuai; Zhou, Jianmin

    2016-01-01

    A field micro-plot experiment using nitrogen isotope (15N) labeling was conducted to determine the effects of placement methods (broadcast and band) and N rates (60, 150 and 240 kg ha-1) on the fate of urea-15N in the wheat-soil system in Guangde County of Anhui Province, China. N fertilizer applied in bands increased grain yield by 15% compared with broadcast application. The N fertilizer application rate had a significant effect on grain yield, straw yield and aboveground biomass, as well as on N uptake and N concentration of wheat. The recovery of urea-15N was a little higher for broadcast (34.0-39.0%) than for band treatment (31.2-38.2%). Most of the soil residual N was retained in the 0-20 cm soil layer. At the N rates of 60 and 240 kg ha-1, the residual 15N was higher for band (34.4 and 108.7 kg ha-1, respectively) than for broadcast application (29.6 and 88.4 kg ha-1, respectively). Compared with broadcast treatment, banded placement of N fertilizer decreased the N loss in the wheat-soil system. Band application one time is an alternative N management practice for winter wheat in this region.

  16. Cigarette litter: smokers' attitudes and behaviors.

    PubMed

    Rath, Jessica M; Rubenstein, Rebecca A; Curry, Laurel E; Shank, Sarah E; Cartwright, Julia C

    2012-06-01

    Cigarette butts are consistently the most collected items in litter clean-up efforts, which are a costly burden to local economies. In addition, tobacco waste may be detrimental to our natural environment. The tobacco industry has conducted or funded numerous studies on smokers' littering knowledge and behavior, however, non-industry sponsored research is rare. We sought to examine whether demographics and smokers' knowledge and beliefs toward cigarette waste as litter predicts littering behavior. Smokers aged 18 and older (n = 1,000) were interviewed about their knowledge and beliefs towards cigarette waste as litter. Respondents were members of the Research Now panel, an online panel of over three million respondents in the United States. Multivariate logistic regressions were conducted to determine factors significantly predictive of ever having littered cigarette butts or having littered cigarette butts within the past month (p-value < 0.05). The majority (74.1%) of smokers reported having littered cigarette butts at least once in their life, by disposing of them on the ground or throwing them out of a car window. Over half (55.7%) reported disposing of cigarette butts on the ground, in a sewer/gutter, or down a drain in the past month. Those who did not consider cigarette butts to be litter were over three and half times as likely to report having ever littered cigarette butts (OR = 3.68, 95%CI = 2.04, 6.66) and four times as likely to have littered cigarette butts in the past month (OR = 4.00, 95%CI = 2.53, 6.32). Males were significantly more likely to have littered cigarette butts in the past month compared to females (OR = 1.49, 95%CI = 1.14, 1.94). Holding the belief that cigarette butts are not litter was the only belief in this study that predicted ever or past-month littering of cigarette waste. Messages in anti-cigarette-litter campaigns should emphasize that cigarette butts are not just litter but are toxic waste and are harmful when disposed of

  17. Cigarette Litter: Smokers’ Attitudes and Behaviors

    PubMed Central

    Rath, Jessica M.; Rubenstein, Rebecca A.; Curry, Laurel E.; Shank, Sarah E.; Cartwright, Julia C.

    2012-01-01

    Cigarette butts are consistently the most collected items in litter clean-up efforts, which are a costly burden to local economies. In addition, tobacco waste may be detrimental to our natural environment. The tobacco industry has conducted or funded numerous studies on smokers’ littering knowledge and behavior, however, non-industry sponsored research is rare. We sought to examine whether demographics and smokers’ knowledge and beliefs toward cigarette waste as litter predicts littering behavior. Smokers aged 18 and older (n = 1,000) were interviewed about their knowledge and beliefs towards cigarette waste as litter. Respondents were members of the Research Now panel, an online panel of over three million respondents in the United States. Multivariate logistic regressions were conducted to determine factors significantly predictive of ever having littered cigarette butts or having littered cigarette butts within the past month (p-value < 0.05). The majority (74.1%) of smokers reported having littered cigarette butts at least once in their life, by disposing of them on the ground or throwing them out of a car window. Over half (55.7%) reported disposing of cigarette butts on the ground, in a sewer/gutter, or down a drain in the past month. Those who did not consider cigarette butts to be litter were over three and half times as likely to report having ever littered cigarette butts (OR = 3.68, 95%CI = 2.04, 6.66) and four times as likely to have littered cigarette butts in the past month (OR = 4.00, 95%CI = 2.53, 6.32). Males were significantly more likely to have littered cigarette butts in the past month compared to females (OR = 1.49, 95%CI = 1.14, 1.94). Holding the belief that cigarette butts are not litter was the only belief in this study that predicted ever or past-month littering of cigarette waste. Messages in anti-cigarette-litter campaigns should emphasize that cigarette butts are not just litter but are toxic waste and are harmful when disposed of

  18. Cigarette litter: smokers' attitudes and behaviors.

    PubMed

    Rath, Jessica M; Rubenstein, Rebecca A; Curry, Laurel E; Shank, Sarah E; Cartwright, Julia C

    2012-06-01

    Cigarette butts are consistently the most collected items in litter clean-up efforts, which are a costly burden to local economies. In addition, tobacco waste may be detrimental to our natural environment. The tobacco industry has conducted or funded numerous studies on smokers' littering knowledge and behavior, however, non-industry sponsored research is rare. We sought to examine whether demographics and smokers' knowledge and beliefs toward cigarette waste as litter predicts littering behavior. Smokers aged 18 and older (n = 1,000) were interviewed about their knowledge and beliefs towards cigarette waste as litter. Respondents were members of the Research Now panel, an online panel of over three million respondents in the United States. Multivariate logistic regressions were conducted to determine factors significantly predictive of ever having littered cigarette butts or having littered cigarette butts within the past month (p-value < 0.05). The majority (74.1%) of smokers reported having littered cigarette butts at least once in their life, by disposing of them on the ground or throwing them out of a car window. Over half (55.7%) reported disposing of cigarette butts on the ground, in a sewer/gutter, or down a drain in the past month. Those who did not consider cigarette butts to be litter were over three and half times as likely to report having ever littered cigarette butts (OR = 3.68, 95%CI = 2.04, 6.66) and four times as likely to have littered cigarette butts in the past month (OR = 4.00, 95%CI = 2.53, 6.32). Males were significantly more likely to have littered cigarette butts in the past month compared to females (OR = 1.49, 95%CI = 1.14, 1.94). Holding the belief that cigarette butts are not litter was the only belief in this study that predicted ever or past-month littering of cigarette waste. Messages in anti-cigarette-litter campaigns should emphasize that cigarette butts are not just litter but are toxic waste and are harmful when disposed of

  19. 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

  20. 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 δ15N 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 δ15N than when grown in Fe-limited media ([Fe] < 50 nM). A compilation of our data with previous measurements of δ15N 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 δ15N values preserved in Archean and some Phanerozoic sediments, generally attributed to the production of marine organic matter with low δ15N 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.

  1. 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.

  2. Litter composition effects on decomposition across the litter-soil interface

    EPA Science Inventory

    Background/Question/Methods Many studies have investigated the influence of plant litter species composition on decomposition dynamics, but given the variety of communities and environments around the world, a variety of consequences of litter-mixing have been reported. Litter ...

  3. McDonald's Litter Hunt: A Community Litter Control System for Youth.

    ERIC Educational Resources Information Center

    McNees, M. Patrick; And Others

    1979-01-01

    Describes a community litter control program. Special adhesive stickers were randomly placed on existing litter throughout a community and youth were rewarded with special prizes for participating in the program. Litter was reduced 32 percent across the city. (Author/MA)

  4. Multiple Applications of Sodium Bisulfate to Broiler Litter Affect Ammonia Release and Litter Properties.

    PubMed

    Hunolt, Alicia E; Maguire, Rory O; Ogejo, Jactone A; Badgley, Brian D; Frame, W Hunter; Reiter, Mark S

    2015-11-01

    Ammonia (NH) emissions from animal manures can cause air and water quality problems. Poultry litter treatment (PLT, sodium bisulfate; Jones-Hamilton Co.) is an acidic amendment that is applied to litter in poultry houses to decrease NH emissions, but currently it can only be applied once before birds are placed in the houses. This project analyzed the effect of multiple PLT applications on litter properties and NH release. Volatility chambers were used to compare multiple, single, and no application of PLT to poultry litter, all with and without fresh manure applications. A field component consisted of two commercial broiler houses: one had a single, preflock PLT application, while the other received PLT reapplications during the flock using an overhead application system. In the volatility chambers, single and reapplied PLT caused greater litter moisture and lower litter pH and , relative to no PLT. After 14 d, NH released from litter treated with reapplied PLT was significantly less than litter with both single and no applications. Furthermore, total N in litter was greatest in litter treated with reapplied PLT, increasing its fertilizer value. In the commercial poultry houses, PLT reapplication led to a temporary decrease in litter pH and , but these effects did not last because of continued bird excretion. Although one preflock PLT application is currently used as a successful strategy to control NH during early flock growth, repeat PLT application using the overhead reapplication system was not successful because of problems with the reapplication system and litter moisture concerns. PMID:26641342

  5. Light-mediated 15N fractionation in Caribbean gorgonian octocorals: implications for pollution monitoring

    NASA Astrophysics Data System (ADS)

    Baker, D. M.; Kim, K.; Andras, J. P.; Sparks, J. P.

    2011-09-01

    The stable nitrogen isotope ratio ( δ 15N) of coral tissue is a useful recorder of anthropogenic pollution in tropical marine ecosystems. However, little is known of the natural environmentally induced fractionations that affect our interpretation of coral δ 15N values. In symbiotic scleractinians, light affects metabolic fractionation of N during photosynthesis, which may confound the identification of N pollution between sites of varied depth or turbidity. Given the superiority of octocorals for δ 15N studies, our goal was to quantify the effect of light on gorgonian δ 15N in the context of monitoring N pollution sources. Using field collections, we show that δ 15N declined by 1.4‰ over 20 m depth in two species of gorgonians, the common sea fan, Gorgonia ventalina, and the slimy sea plume, Pseudopterogorgia americana. An 8-week laboratory experiment with P. americana showed that light, not temperature causes this variation, whereby the lowest fractionation of the N source was observed in the highest light treatment. Finally, we used a yearlong reciprocal depth transplant experiment to quantify the time frame over which δ 15N changes in G. ventalina as a function of light regime . Over the year, δ 15N was unchanged and increased slightly in the deep control colonies and shallow colonies transplanted to the deep site, respectively. Within 6 months, colonies transplanted from deep to shallow became enriched by 0.8‰, mirroring the enrichment observed in the shallow controls, which was likely due to the combined effect of an increase in the source δ 15N and reduced fractionation. We conclude that light affects gorgonian δ 15N fractionation and should be considered in sampling designs for N pollution monitoring. However, these fractionations are small relative to differences observed between natural and anthropogenic N sources.

  6. Analysis of proteome dynamics in mice by isotopic labeling.

    PubMed

    Price, John C; Ghaemmaghami, Sina

    2014-01-01

    Recent advances in mass spectrometry and in vivo isotopic labeling have enabled proteome-wide analyses of protein turnover in complex organisms. Here, we describe a protocol for analyzing protein turnover rates in mouse tissues by comprehensive (15)N labeling. The procedure involves the complete isotopic labeling of blue green algae (Spirulina platensis) with (15)N and utilizing it as a source of dietary nitrogen for mice. We outline a detailed protocol for in-house production of (15)N-labeled algae, labeling of mice, and analysis of isotope incorporation kinetics by mass spectrometry. The methodology can be adapted to analyze proteome dynamics in most murine tissues and may be particularly useful in the analysis of proteostatic disruptions in mouse models of disease. PMID:24791984

  7. Radiative p 15N Capture in the Region of Astrophysical Energies

    NASA Astrophysics Data System (ADS)

    Dubovichenko, S. B.; Burtebaev, N.; Dzhazairov-Kakhramanov, A. V.; Alimov, D. K.

    2016-06-01

    Within the framework of the modified potential cluster model with classification of orbital states according to the Young schemes, the possibility of describing experimental data for the astrophysical S-factor of p 15N radiative capture at energies from 50 to 1500 keV is considered. It is shown that on the basis of M1 and E1 transitions from various p 15N scattering states to the ground state of the 16O nucleus in the p 15N channel it is entirely possible to successfully explain the overall behavior of the S-factor in the considered energy region in the presence of two resonances.

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

    DOE PAGES

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

    2015-07-30

    We compared carbon-rich grains with isotopic anomalies 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. Furthermore, 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. All of the explosion energies and H concentrations aremore » 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.« less

  9. 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.

  10. [Isotopic signature (15N/14N and 13C/12C) confirms similarity of trophic niches of millipedes (Myriapoda, Diplopoda) in a temperate deciduous forest].

    PubMed

    Semeniuk, I I; Tiunov, A V

    2011-01-01

    The species composition, abundance, and isotopic signature of millipedes (Myriapoda, Diplopoda) were investigated in seven biotopes of Kaluzhskie Zaseki State Nature Reserve. Nine Diplopoda species were found in total, and the local species diversity (within a sampling plot) reached seven species. The Diplopoda tissues were similar to the plant litter in the isotopic composition of nitrogen (delta15N was by 0.4% per hundred higher, on average), but were more strongly enriched in heavy carbon (delta13C was by 4% per hundred higher, on average). Removal of mineral carbon from the cuticle reduced delta13C of Diplopoda by about 1.4% per hundred on average. Differences in the delta15N and delta13C values between the species did not exceed 2.5 per hundred. Differences in the isotopic compositions of the considered species are insignificant, and thus, it is impossible to distinguish particular trophic guilds in the Diplopoda community. Analysis of the published data confirmed that isotopic differentiation of millipedes was much less pronounced than in other investigated groups of soil animals. Hence, millipedes of the deciduous forest form a uniform trophic group.

  11. Increase of Natural 15N Enrichment of Soybean Nodules with Mean Nodule Mass 1

    PubMed Central

    Shearer, Georgia; Bryan, Barbara A.; Kohl, Daniel H.

    1984-01-01

    The 15N abundance of soybean (Glycine max L. Merrill var Harosoy) nodules is usually greater than it is for other tissues or for atmospheric N2. Results of experiments in which nodules were separated by size show that the magnitude of the 15N enrichment is correlated with nodule mass. The results support the hypothesis that 15N enrichment of nodules results from differential N isotopic fractionation for synthesis of nodule tissue versus synthesis of compounds for export from the nodule. The physiological significance of this hypothesis is that it requires that a substantial fraction of the N for nodule tissue synthesis in 15N-enriched nodules be N recently fixed within the same nodule. PMID:16663917

  12. 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

  13. Distribution of 15N-chlorocholine chloride in eggs of laying hens.

    PubMed

    Songsang, A; Chakeredza, S; Thinggaard, G; Vearasilp, T; ter Meulen, U

    2002-06-01

    The distribution of Chlorocholine chloride (CCC) in the eggs of laying hens was studied using 15N-CCC. Twelve layers (37 weeks old) were divided into four groups and used in this study consisting of three feeding phases. In phase one (7 days), all the hens received a CCC-free diet [165 g CP/kg dry matter (DM); 11.58 MJ ME/kg DM]. In phase two (11 days), four levels of 15N-CCC: 0, 5, 50 and 250 ppm were added to the respective diets, while in phase three (7 days), CCC-free feed was again offered. Egg samples were taken and the 15N content of egg yolk and albumin were determined. At the end of phase two, there was a significant (p < 0.05) increase in 15N content in egg yolk from hens fed the 50 and 250 ppm CCC diets and in albumin from hens fed the 250 ppm CCC diet. The estimated 15N-CCC residue was 1.71, 6.64, 28.80 ppm in egg yolk and 1.58, 1.08 and 4.50 ppm in albumin from hens fed 5, 50 and 250 ppm CCC, respectively. The CCC residue, from quantitative analysis ranged from 0.21 to 0.93 and 0.93 to 2.43 ppm in yolk of hens fed 50 and 250 ppm CCC, respectively, whereas a range of 0.40-1.46 ppm, was found in the albumin of hens fed 250 ppm. The difference in measured CCC in yolk and albumin and that estimated from 15N-CCC could have been due to breakdown products of 15N-CCC. Seven days after withdrawal of 15N-CCC, the estimated 15N-CCC residue in egg yolk decreased to 0.43, 2.45 and 15.59 ppm, on 5, 50 and 250 ppm CCC dietary treatments, respectively, and to 2.46 ppm in albumin from hens fed 250 ppm CCC. The higher increase in 15N content could have been due to a higher incorporation of 15N-CCC into yolk than albumin during the process of rapid yolk deposition. This experiment showed that consumed CCC is distributed both into yolk and albumin in a dose dependent manner and that CCC is metabolized in laying hens. However, the level of CCC in the diet which could lead to accumulation of detectable CCC levels in eggs as observed in this study, is much higher than the

  14. 33 CFR 144.01-35 - Litter.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Litter. 144.01-35 Section 144.01-35 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES LIFESAVING APPLIANCES Manned Platforms § 144.01-35 Litter. On each...

  15. Enzymatic activities in coniferous leaf litter

    SciTech Connect

    Spalding, B.P.

    1980-07-01

    Assays for measuring the activities of cellulase, xylanase, mannase, amylase, ..beta..-glucosidase, invertase, and protease employing buffered suspensions of ground coniferous and deciduous leaf litter exhibited zero-order kinetics. Only a small percentage of the whole-litter activities of invertase, ..beta..-glucosidase, and protease were extractable into 0.05M potassium acetate, pH 5.0; however, extractable activities of cellulase and xylanase represented from 39 to 174% of the whole-litter activities indicating their soluble exocellar nature. Extractable protease and amylase activities were best correlated with the average daily rates of CO/sub 2/ evolution in a group of 90 leaf litter samples equally representing 18 coniferous species. Enzymatic activities were readily detectable in extracts of all samples but classification of the samples by species provided little differentiation in the distribution of either enzymatic activities or rates of CO/sub 2/ evolution. Mannase, cellulase, and xylanase activities were well-correlated with each other in all samples. Assays attempting to measure a pool of readily-metabolizable substances in litter by extractable reducing substances, ninhydrin-positive substances, glucose, and phenolics failed to show correlation coefficients >0.41 with rates of CO/sub 2/ evolution. Addition of D-(+)-catechin to litter extracts, up to levels equivalent to those observed in the group of samples, did not inhibit any carbohydrase thus suggesting the lack of inhibition of litter-decomposing enzymes by the concentrations of phenolics present in these coniferous leaf litters.

  16. Water proton spin saturation affects measured protein backbone 15 N spin relaxation rates

    NASA Astrophysics Data System (ADS)

    Chen, Kang; Tjandra, Nico

    2011-12-01

    Protein backbone 15N NMR spin relaxation rates are useful in characterizing the protein dynamics and structures. To observe the protein nuclear-spin resonances a pulse sequence has to include a water suppression scheme. There are two commonly employed methods, saturating or dephasing the water spins with pulse field gradients and keeping them unperturbed with flip-back pulses. Here different water suppression methods were incorporated into pulse sequences to measure 15N longitudinal T1 and transversal rotating-frame T1ρ spin relaxation. Unexpectedly the 15N T1 relaxation time constants varied significantly with the choice of water suppression method. For a 25-kDa Escherichiacoli. glutamine binding protein (GlnBP) the T1 values acquired with the pulse sequence containing a water dephasing gradient are on average 20% longer than the ones obtained using a pulse sequence containing the water flip-back pulse. In contrast the two T1ρ data sets are correlated without an apparent offset. The average T1 difference was reduced to 12% when the experimental recycle delay was doubled, while the average T1 values from the flip-back measurements were nearly unchanged. Analysis of spectral signal to noise ratios ( s/ n) showed the apparent slower 15N relaxation obtained with the water dephasing experiment originated from the differences in 1H N recovery for each relaxation time point. This in turn offset signal reduction from 15N relaxation decay. The artifact becomes noticeable when the measured 15N relaxation time constant is comparable to recycle delay, e.g., the 15N T1 of medium to large proteins. The 15N relaxation rates measured with either water suppression schemes yield reasonable fits to the structure. However, data from the saturated scheme results in significantly lower Model-Free order parameters (< S2> = 0.81) than the non-saturated ones (< S2> = 0.88), indicating such order parameters may be previously underestimated.

  17. Leaf Litter Mixtures Alter Microbial Community Development: Mechanisms for Non-Additive Effects in Litter Decomposition

    PubMed Central

    Chapman, Samantha K.; Newman, Gregory S.; Hart, Stephen C.; Schweitzer, Jennifer A.; Koch, George W.

    2013-01-01

    To what extent microbial community composition can explain variability in ecosystem processes remains an open question in ecology. Microbial decomposer communities can change during litter decomposition due to biotic interactions and shifting substrate availability. Though relative abundance of decomposers may change due to mixing leaf litter, linking these shifts to the non-additive patterns often recorded in mixed species litter decomposition rates has been elusive, and links community composition to ecosystem function. We extracted phospholipid fatty acids (PLFAs) from single species and mixed species leaf litterbags after 10 and 27 months of decomposition in a mixed conifer forest. Total PLFA concentrations were 70% higher on litter mixtures than single litter types after 10 months, but were only 20% higher after 27 months. Similarly, fungal-to-bacterial ratios differed between mixed and single litter types after 10 months of decomposition, but equalized over time. Microbial community composition, as indicated by principal components analyses, differed due to both litter mixing and stage of litter decomposition. PLFA biomarkers a15∶0 and cy17∶0, which indicate gram-positive and gram-negative bacteria respectively, in particular drove these shifts. Total PLFA correlated significantly with single litter mass loss early in decomposition but not at later stages. We conclude that litter mixing alters microbial community development, which can contribute to synergisms in litter decomposition. These findings advance our understanding of how changing forest biodiversity can alter microbial communities and the ecosystem processes they mediate. PMID:23658639

  18. Effects of litter manipulation on litter decomposition in a successional gradients of tropical forests in southern China.

    PubMed

    Chen, Hao; Gurmesa, Geshere A; Liu, Lei; Zhang, Tao; Fu, Shenglei; Liu, Zhanfeng; Dong, Shaofeng; Ma, Chuan; Mo, Jiangming

    2014-01-01

    Global changes such as increasing CO2, rising temperature, and land-use change are likely to drive shifts in litter inputs to forest floors, but the effects of such changes on litter decomposition remain largely unknown. We initiated a litter manipulation experiment to test the response of litter decomposition to litter removal/addition in three successional forests in southern China, namely masson pine forest (MPF), mixed coniferous and broadleaved forest (MF) and monsoon evergreen broadleaved forest (MEBF). Results showed that litter removal decreased litter decomposition rates by 27%, 10% and 8% and litter addition increased litter decomposition rates by 55%, 36% and 14% in MEBF, MF and MPF, respectively. The magnitudes of changes in litter decomposition were more significant in MEBF forest and less significant in MF, but not significant in MPF. Our results suggest that change in litter quantity can affect litter decomposition, and this impact may become stronger with forest succession in tropical forest ecosystem.

  19. A Greener Arctic: Vascular Plant Litter Input in Subarctic Peat Bogs Changes Soil Invertebrate Diets and Decomposition Patterns

    NASA Astrophysics Data System (ADS)

    Krab, E. J.; Berg, M. P.; Aerts, R.; van Logtestijn, R. S. P.; Cornelissen, H. H. C.

    2014-12-01

    Climate-change-induced trends towards shrub dominance in subarctic, moss-dominated peatlands will most likely have large effects on soil carbon (C) dynamics through an input of more easily decomposable litter. The mechanisms by which this increase in vascular litter input interacts with the abundance and diet-choice of the decomposer community to alter C-processing have, however, not yet been unraveled. We used a novel 13C tracer approach to link invertebrate species composition (Collembola), abundance and species-specific feeding behavior to C-processing of vascular and peat moss litters. We incubated different litter mixtures, 100% Sphagnum moss litter, 100% Betula leaf litter, and a 50/50 mixture of both, in mesocosms for 406 days. We revealed the transfer of C from the litters to the soil invertebrate species by 13C labeling of each of the litter types and assessed 13C signatures of the invertebrates Collembola species composition differed significantly between Sphagnum and Betula litter. Within the 'single type litter' mesocosms, Collembola species showed different 13C signatures, implying species-specific differences in diet choice. Surprisingly, the species composition and Collembola abundance changed relatively little as a consequence of Betula input to a Sphagnum based system. Their diet choice, however, changed drastically; species-specific differences in diet choice disappeared and approximately 67% of the food ingested by all Collembola originated from Betula litter. Furthermore, litter decomposition patterns corresponded to these findings; mass loss of Betula increased from 16.1% to 26.2% when decomposing in combination with Sphagnum, while Sphagnum decomposed even slower in combination with Betula litter (1.9%) than alone (4.7%). This study is the first to empirically show that collective diet shifts of the peatland decomposer community from mosses towards vascular plant litter may drive altered decomposition patterns. In addition, we showed that

  20. 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.

  1. Fate of tannins in Corsican pine litter.

    PubMed

    Nierop, Klaas G J; Verstraten, Jacobus M

    2006-12-01

    Tannins are ubiquitous in higher plants and also in litter and soils where they affect many biogeochemical processes. Despite this well-recognized role, their fate in litter and mineral soils is hardly known, as often only trace amounts, if any, are measured. In this study, we conducted an incubation experiment with Corsican pine litter to which known amounts of tannic acid (TA) or condensed tannins (CTs) from Corsican pine were added. Using Folin-Ciocalteu as a measure for total phenolics and HCl-butanol as an assay specific for CTs, acetone/water extractable phenolics and tannins decreased with time towards very low levels. Application of thermally assisted hydrolysis and methylation to litter before and after acetone/water extraction revealed that TA concentration decreased. By contrast, CTs remained to a great extent in the litter and could not be extracted suggesting that they were tightly bound.

  2. Poultry litter toxicity comparison from various bioassays

    SciTech Connect

    Gupta, G.; Kelly, P. )

    1992-01-01

    Poultry litter contains many toxic chemicals including Cu, As, Pb, Cd, Hg, Se and PCBs. Poultry litter leachate has been shown to be more toxic to marine luminescent organisms (Photobacterium phosphoreum) than other farm animal manures. A comparison of toxicity of the poultry litter leachate was undertaken using various bioassays. The EC{sub 50} (or LC{sub 50}) value for the leachate with the Microtox and Daphnia bioassays was 2.9 g/L/ Nitrobacter and Pseudomonas bioassays were not useful in determining the leachate toxicity because of the nutritional properties of the litter. Poultry litter leachate was found to be mutagenic to strains TA 97, TA 98, TA 100 and TA 102 using the Ames Test.

  3. 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

  4. Litter input decreased the response of soil organic matter decomposition to warming in two subtropical forest soils.

    PubMed

    Wang, Qingkui; He, Tongxin; Liu, Jing

    2016-01-01

    Interaction effect of temperature and litter input on SOM decomposition is poor understood, restricting accurate prediction of the dynamics and stocks of soil organic carbon under global warming. To address this knowledge gap, we conducted an incubation experiment by adding (13)C labeled leaf-litter into a coniferous forest (CF) soil and a broadleaved forest (BF) soil. In this experiment, response of the temperature sensitivity (Q10) of SOM decomposition to the increase in litter input was investigated. The temperature dependences of priming effect (PE) and soil microbial community were analyzed. The Q10 for CF soil significantly decreased from 2.41 in no-litter treatment to 2.05 in litter-added treatment and for BF soil from 2.14 to 1.82, suggesting that litter addition decreases the Q10. PE in the CF soil was 24.9% at 20 °C and 6.2% at 30 °C, and in the BF soil the PE was 8.8% at 20 °C and -7.0% at 30 °C, suggesting that PE decreases with increasing temperature. Relative PE was positively related to the concentrations of Gram-negative bacterial and fungal PLFAs. This study moves a step forward in understanding warming effect on forest carbon cycling by highlighting interaction effect of litter input and warming on soil carbon cycling. PMID:27644258

  5. Litter input decreased the response of soil organic matter decomposition to warming in two subtropical forest soils

    PubMed Central

    Wang, Qingkui; He, Tongxin; Liu, Jing

    2016-01-01

    Interaction effect of temperature and litter input on SOM decomposition is poor understood, restricting accurate prediction of the dynamics and stocks of soil organic carbon under global warming. To address this knowledge gap, we conducted an incubation experiment by adding 13C labeled leaf-litter into a coniferous forest (CF) soil and a broadleaved forest (BF) soil. In this experiment, response of the temperature sensitivity (Q10) of SOM decomposition to the increase in litter input was investigated. The temperature dependences of priming effect (PE) and soil microbial community were analyzed. The Q10 for CF soil significantly decreased from 2.41 in no-litter treatment to 2.05 in litter-added treatment and for BF soil from 2.14 to 1.82, suggesting that litter addition decreases the Q10. PE in the CF soil was 24.9% at 20 °C and 6.2% at 30 °C, and in the BF soil the PE was 8.8% at 20 °C and −7.0% at 30 °C, suggesting that PE decreases with increasing temperature. Relative PE was positively related to the concentrations of Gram-negative bacterial and fungal PLFAs. This study moves a step forward in understanding warming effect on forest carbon cycling by highlighting interaction effect of litter input and warming on soil carbon cycling. PMID:27644258

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

    PubMed

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

    2008-12-11

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

  7. 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.

  8. Importance of Nitrate Attenuation In A Small Wetland Following Forest Harvest: 18O/16O, 15N/14N in nitrate and 15N/14N) in vegetation

    NASA Astrophysics Data System (ADS)

    Spoelstra, J.; Schiff, S. L.; Semkin, R. G.; Jeffries, D. S.; Elgood, R. J.

    2004-05-01

    Forest harvest can result in elevated nitrate concentrations in streams and groundwater affecting forest regeneration and downstream aquatic ecosystems. Turkey Lakes Watershed, located near Sault Ste Marie, Ontario (TLW), exhibits relatively high nitrate export due to naturally high rates of nitrification. During a forest harvest experiment at the TLW, stable isotope techniques were used to investigate nitrate attenuation in an intermediate position natural wetland receiving high concentrations of nitrate following forest clear-cutting. Isotopic analysis of nitrate (18O/16O, 15N/14N) and vegetation (15N/14N) demonstrated that denitrification and plant uptake of nitrate resulted in significantly lower nitrate concentrations in wetland outflow compared to incoming stream water and groundwater. The 0.2-hectare forested swamp, too small to show up on standard topographic maps, retained 65 to 100 percent of upgradient nitrate inputs, elevated due to increased nitrification in soils. The 15N/14N enrichment factor associated with nitrate attenuation in wetland surface water was lower than observed during denitrification in groundwaters, suggesting that denitrification proceeded to completion in some areas of the wetland. Even small, shallow, carbon rich pockets of organic matter in topographic depressions can significantly affect biogeochemical fluxes of C, N, S and Ca. Future forest management practices designed to recognize and preserve small wetlands could significantly reduce the potentially detrimental effects of forest harvest on aquatic systems.

  9. Plastic litter in the sea.

    PubMed

    Depledge, M H; Galgani, F; Panti, C; Caliani, I; Casini, S; Fossi, M C

    2013-12-01

    On June 2013 a workshop at the University of Siena (Italy) was organized to review current knowledge and to clarify what is known, and what remains to be investigated, concerning plastic litter in the sea. The content of the workshop was designed to contribute further to the European Marine Strategy Framework Directive (MSFD) following an inaugural workshop in 2012. Here we report a number of statements relevant to policymakers and scientists that was overwhelming agreement from the participants. Many might view this as already providing sufficient grounds for policy action. At the very least, this early warning of the problems that lie ahead should be taken seriously, and serve as a stimulus for further research.

  10. 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.

  11. Soil N and 15N variation with time in a California annual grassland ecosystem

    USGS Publications Warehouse

    Brenner, D.L.; Amundson, Ronald; Baisden, W. Troy; Kendall, C.; Harden, J.

    2001-01-01

    The %N and ??15N values of soils and plants were measured along a chronosequence spanning 3 to 3000 Ky in a California annual grassland. Total soil N decreased with increasing soil age (1.1 to 0.4 kg N m-2) while the mean ?? 15N values of the soil N increased by several ??? from the youngest to oldest sites (+3.5 to +6.2 ???). The ?? 15N values of plants varied along the gradient, reflecting changing soil N pools and differences in the form of N uptake. The decline in total N storage with time is hypothesized to be due to a shift from N to P limitation with increasing soil age. The general increase in ?? 15N values with time is interpreted using a N mass balance model, and appears to reflect a shift toward an increasing proportional losses of inorganic mineral forms of N (vs. organic forms) with increasing soil age. We develop a quantitative index of this trend (mineral vs. organic forms of N loss) using mass balance considerations and parameters. The %N and ?? 15N values along the California age gradient were compared to the published data for a comparably aged chronosequence in Hawaii. Most striking in this comparison is the observation that the California soil and plant ?? 15N values are several ??? greater than those on comparably aged Hawaiian sites. Multiple explanations are plausible, but assuming the sites have a similar range in ?? 15N values of atmospheric inputs, the isotopic differences suggest that N may be, at least seasonally, in greater excess in the strongly seasonal, semi-arid, California grassland. Copyright ?? 2001 Elsevier Science Ltd.

  12. 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 δ15N than non-mineral-associated OM. This implies that the δ15N 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 δ15N 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 δ15N in

  13. Effects of Nitrogen Addition on Litter Decomposition and CO2 Release: Considering Changes in Litter Quantity

    PubMed Central

    Li, Hui-Chao; Hu, Ya-Lin; Mao, Rong; Zhao, Qiong; Zeng, De-Hui

    2015-01-01

    This study aims to evaluate the impacts of changes in litter quantity under simulated N deposition on litter decomposition, CO2 release, and soil C loss potential in a larch plantation in Northeast China. We conducted a laboratory incubation experiment using soil and litter collected from control and N addition (100 kg ha−1 year−1 for 10 years) plots. Different quantities of litter (0, 1, 2 and 4 g) were placed on 150 g soils collected from the same plots and incubated in microcosms for 270 days. We found that increased litter input strongly stimulated litter decomposition rate and CO2 release in both control and N fertilization microcosms, though reduced soil microbial biomass C (MBC) and dissolved inorganic N (DIN) concentration. Carbon input (C loss from litter decomposition) and carbon output (the cumulative C loss due to respiration) elevated with increasing litter input in both control and N fertilization microcosms. However, soil C loss potentials (C output–C input) reduced by 62% in control microcosms and 111% in N fertilization microcosms when litter addition increased from 1 g to 4 g, respectively. Our results indicated that increased litter input had a potential to suppress soil organic C loss especially for N addition plots. PMID:26657180

  14. PAHs in decaying Quercus ilex leaf litter: mutual effects on litter decomposition and PAH dynamics.

    PubMed

    De Nicola, F; Baldantoni, D; Alfani, A

    2014-11-01

    The investigation of the relationships between litter decomposition and polycyclic aromatic hydrocarbons (PAHs) is important to shed light not only on the effects of these pollutants on fundamental ecosystem processes, such as litter decomposition, but also on the degradation of these pollutants by soil microbial community. This allows to understand the effect of atmospheric PAH contamination on soil PAH content via litterfall. At this aim, we studied mass and PAH dynamics of Quercus ilex leaf litters collected from urban, industrial and remote sites, incubated in mesocosms under controlled conditions for 361d. The results highlighted a litter decomposition rate of leaves sampled in urban>industrial>remote sites; the faster decomposition of litter of the urban site is also related to the low C/N ratio of the leaves. The PAHs showed concentrations at the beginning of the incubation of 887, 650 and 143 ng g(-1)d.w., respectively in leaf litters from urban, industrial and remote sites. The PAHs in litter decreased along the time, with the same trend observed for mass litter, showing the highest decrease at 361 d for the urban leaf litter. Anyway, PAH dynamics in all the litters exhibited two phases of loss, separated by a PAH increase observed at 246 d and mainly linked to benzo[e]pyrene.

  15. Origin and abundance of marine litter along sandy beaches of the Turkish Western Black Sea Coast.

    PubMed

    Topçu, Eda N; Tonay, Arda M; Dede, Ayhan; Öztürk, Ayaka A; Öztürk, Bayram

    2013-04-01

    Beach debris abundance was estimated from surveys on 10 beaches of the Turkish Western Black Sea Coast. Debris was collected from 20 m long transects during four different seasons; sorted and categorized by type, usage and origin. Litter density varied from 0.085 to 5.058 items m(-2). Debris was mainly composed of unidentifiable small size (2-7 cm) plastic pieces and beverage-related litter such as bottles and bottle caps. About half of the labeled litter was of foreign origin, including 25 different countries, 23% of which are in the Black Sea region. The south-western Black Sea Coast seems to receive foreign litter from two main sources: land-based debris from the neighboring countries and seaborne debris due to international shipping. Standardized methodology and indicators need to be designated all over the Black Sea basin in order to quantify and qualify coastal litter pollution, monitor compliance with MARPOL and develop regionally effective mitigation measures.

  16. Study on Hydrological Functions of Litter Layers in North China

    PubMed Central

    Li, Xiang; Niu, Jianzhi; Xie, Baoyuan

    2013-01-01

    Canopy interception, throughfall, stemflow, and runoff have received considerable attention during the study of water balance and hydrological processes in forested ecosystems. Past research has either neglected or underestimated the role of hydrological functions of litter layers, although some studies have considered the impact of various characteristics of rainfall and litter on litter interception. Based on both simulated rainfall and litter conditions in North China, the effect of litter mass, rainfall intensity and litter type on the maximum water storage capacity of litter (S) and litter interception storage capacity (C) were investigated under five simulated rainfall intensities and four litter masses for two litter types. The results indicated: 1) the S values increased linearly with litter mass, and the S values of broadleaf litter were on average 2.65 times larger than the S values of needle leaf litter; 2) rainfall intensity rather than litter mass determined the maximum interception storage capacity (Cmax); Cmax increased linearly with increasing rainfall intensity; by contrast, the minimum interception storage capacity (Cmin) showed a linear relationship with litter mass, but a poor correlation with rainfall intensity; 3) litter type impacted Cmax and Cmin; the values of Cmax and Cmin for broadleaf litter were larger than those of needle leaf litter, which indicated that broadleaf litter could intercepte and store more water than needle leaf litter; 4) a gap existed between Cmax and Cmin, indicating that litter played a significant role by allowing rainwater to infiltrate or to produce runoff rather than intercepting it and allowing it to evaporate after the rainfall event; 5) Cmin was always less than S at the same litter mass, which should be considered in future interception predictions. Vegetation and precipitation characteristics played important roles in hydrological characteristics. PMID:23936188

  17. Antibiotic resistance of bacterial litter isolates.

    PubMed

    Kelley, T R; Pancorbo, O C; Merka, W C; Barnhart, H M

    1998-02-01

    Use of antibiotics in subtherapeutic doses as growth-promoting feed additives for animal production is widespread in the U.S. and throughout the world. Previous studies by our research group concluded that size fractionation of poultry (broiler) litter followed by storage facilitated reutilization of litter as a soil amendment or bedding supplement. However, litter microbial contamination, including antibiotic-resistant populations, and accumulation of metals and other elements may limit litter reutilization. Litter from four broiler houses was separated into a fine fraction for use as a soil amendment, and a coarse fraction for reutilization as a bedding supplement in growing subsequent flocks of broilers. Fractions and whole litter were stored in indoor piles simulating farm storage conditions for 4 mo with periodic analysis for metals, other elements, and culturable bacteria (including total and fecal coliform, Aeromonas hydrophila, Pseudomonas aeruginosa, Yersinia enterocolitica, and Campylobacter jejuni). Representative bacterial isolates were tested for their sensitivity to 12 common antibiotics (ampicillin, bacitracin, cephalothin, erythromycin, gentamicin, kanamycin, nalidixic acid, neomycin, penicillin, streptomycin, sulfisoxazole, and tetracycline) using the Kirby-Bauer technique. Pathogens and indicator bacteria tested were found to be resistant to multiple antibiotics. Data suggest that microbial contamination of litter should be reduced or eliminated prior to reutilization to minimize environmental health risks related to transfer of antibiotic-resistant bacteria to humans or other animals. PMID:9495488

  18. Treatment of broiler litter with organic acids.

    PubMed

    Ivanov, I E

    2001-04-01

    Experiments for treatment of contaminated broiler litter with citric, tartaric and salicylic acids were performed. At days 2 and 6 after the treatment, pH values (using a pH-meter), the ammonia concentrations (titration with 0.1 N HCl) and the microbial cells counts were determined in both experimental and control specimens of litter. The cost of acidification of litter was also determined. Our studies showed that the treatment of the contaminated litter with 5 per cent citric acid, 4 per cent tartaric acid and 1.5 per cent salicylic acid created an acid medium with pH under 5.0 and thus reduced the microbial counts to 2.2 x 10(3)colony forming units per gram manure litter. The treatment reduced the content of ammonia in the litter and in the air under the hygienic limits, i.e. 25-50 ppm. The cost of acidification of litter with these organic acids amounted to 0.1 $ per bird and 1.5 $ per 15 birds on one square metre in a growth period of 50 days. PMID:11356097

  19. Fungal functioning in a pine forest: evidence from a ¹⁵N-labeled global change experiment.

    PubMed

    Hobbie, Erik A; van Diepen, Linda T A; Lilleskov, Erik A; Ouimette, Andrew P; Finzi, Adrien C; Hofmockel, Kirsten S

    2014-03-01

    • We used natural and tracer nitrogen (N) isotopes in a Pinus taeda free air CO₂ enrichment (FACE) experiment to investigate functioning of ectomycorrhizal and saprotrophic fungi in N cycling. • Fungal sporocarps were sampled in 2004 (natural abundance and (15) N tracer) and 2010 (tracer) and δ(15)N patterns were compared against litter and soil pools. • Ectomycorrhizal fungi with hydrophobic ectomycorrhizas (e.g. Cortinarius and Tricholoma) acquired N from the Oea horizon or deeper. Taxa with hydrophilic ectomycorrhizas acquired N from the Oi horizon (Russula and Lactarius) or deeper (Laccaria, Inocybe, and Amanita). (15)N enrichment patterns for Cortinarius and Amanita in 2010 did not correspond to any measured bulk pool, suggesting that a persistent pool of active organic N supplied these two taxa. Saprotrophic fungi could be separated into those colonizing pine cones (Baeospora), wood, litter (Oi), and soil (Ramariopsis), with δ(15)N of taxa reflecting substrate differences. (15)N enrichment between sources and sporocarps varied across taxa and contributed to δ(15)N patterns. • Natural abundance and (15)N tracers proved useful for tracking N from different depths into fungal taxa, generally corresponded to literature estimates of fungal activity within soil profiles, and provided new insights into interpreting natural abundance δ(15)N patterns.

  20. 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

  1. δ15N 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 δ(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 δ(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 δ(15)N values and the ratio of black C to total N. These findings point towards fire having a marked impact on soil δ(15)N and, accordingly, on the N cycle of this cold and dry ecosystem. PMID:21290453

  2. Hydrogen Bonds in Crystalline Imidazoles Studied by 15N NMR and ab initio MO Calculations

    NASA Astrophysics Data System (ADS)

    Ueda, Takahiro; Nagatomo, Shigenori; Masui, Hirotsugu; Nakamura, Nobuo; Hayashi, Shigenobu

    1999-07-01

    Intermolecular hydrogen bonds of the type N-H...N in crystals of imidazole and its 4-substituted and 4,5-disubstituted derivatives were studied by 15N CP/MAS NMR and an ab initio molecular orbital (MO) calculation. In the 15N CP/MAS NMR spectrum of each of the imidazole derivatives, two peaks due to the two different functional groups, >NH and =N-, were observed. The value of the 15N isotropic chemical shift for each nitrogen atom depends on both the length of the intermolecular hydrogen bond and the kind of the substituent or substituents. It was found that the difference between the experimen-tal chemical shifts of >NH and =N-varies predominantly with the hydrogen bond length but does not show any systematic dependence on the kind of substituent. The ab initio MO calculations suggest that the hydrogen bond formation influences the 15N isotropic chemical shift predominantly, and that the difference between the 15N isotropic chemical shift of >NH and =N-varies linearly with the hydrogen bond length.

  3. 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

  4. 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.

  5. Mechanistic Determination of Nitrogen Removal By Advanced Soil-Based Wastewater Treatment Systems Using 15n Isotopes

    NASA Astrophysics Data System (ADS)

    Cooper, J.; Loomis, G.; Kalen, D.; Boving, T. B.; Morales, I.; Amador, J.

    2014-12-01

    Current levels of nitrogen removal by onsite wastewater treatment systems (OWTS) are inadequate, with release of N from OWTS contributing to environmental N pollution, especially in coastal zones where aquatic ecosystems are sensitive to eutrophication. Current mechanistic understand of N removal are limited and mainly attributed to denitrification in the drainfield. Loss of N from N2O production during nitrification, a sparsely researched topic, may be a significant mechanism in advanced OWTS systems that enhance O2 diffusion by sand filter pre-treatment, shallow placement of infiltrative areas and timed dosing controls to prevent drainfield saturation. Replicate (n=3) intact soil mesocosms were used with 15N isotope to evaluate the effectiveness and mechanisms of N removal in drainfields with a conventional wastewater delivery (pipe-and-stone, P&S) compared to two advanced types of drainfields, pressurized shallow narrow drainfield (SND) and Geomat (GEO), a variation of a SND drainfield. Over the 11 day experiment, dissolved O2 was 1.6 mg/L for P&S and 3.0 mg/L for SND and GEO. Removal of total N was 13.5% for P&S, 4.8% for SND and 5.4% for GEO. 15NH4 labeled nitrogen inputs to drainfields were transformed primarily to 15NO3 in all outputs. Consistent low 15N2O levels were present in P&S, with increasing levels of N2 peaking 48h after 15NH4 injection, suggesting denitrification dominated N removal. By contrast, SND and GEO 15N2O levels rose quickly, peaking 8h after 15NH4 injection, suggesting N loss by nitrification. When the whole system is considered, including sand filter removal, 26 - 27% of total N was removed by the SND and GEO systems, whereas 14% of total N was removed in the P&S system. Our results suggest the SND and GEO systems as a whole are capable of removing a greater mass of N than the P&S system.

  6. Post-grafting amination of alkyl halide-functionalized silica for applications in catalysis, adsorption, and 15N NMR spectroscopy.

    PubMed

    Moschetta, Eric G; Sakwa-Novak, Miles A; Greenfield, Jake L; Jones, Christopher W

    2015-02-24

    An anhydrous synthesis of aminosilica materials from alkyl halide-functionalized mesoporous SBA-15 silica by post-grafting amination is introduced for applications in CO2 adsorption, cooperative catalysis, and (15)N solid-state NMR spectroscopy. The synthesis is demonstrated to convert terminal alkyl halide-functionalized silica materials containing Cl, Br, and I to primary alkylamines using anhydrous ammonia in a high-pressure reactor. The benefits of the post-grafting amination procedure include (i) use of anhydrous isotopically labeled ammonia, (15)NH3, to create aminosilica materials that can be investigated using (15)N solid-state NMR to elucidate potential intermediates and surface species in CO2 adsorption processes and catalysis, (ii) similar CO2 uptake in experiments extracting CO2 from dry simulated air experiments, and (iii) improved activity in acid-base bifunctional catalysis compared to traditional amine-grafted materials. The effects of the type of halide, the initial halide loading, and the total reaction time on the conversion of the halides to primary amines are explored. Physical and chemical characterizations of the materials show that the textural properties of the silica are unaffected by the reaction conditions and that quantitative conversion to primary amines is achieved even at short reaction times and high initial alkyl halide loadings. Additionally, preliminary (15)N solid-state NMR experiments indicate formation of nitrogen-containing species and demonstrate that the synthesis can be used to create materials useful for investigating surface species by NMR spectroscopy. The differences between the materials prepared via post-grafting amination vs traditional aminosilane grafting are attributed to the slightly increased spacing of the amines synthesized by amination because the alkylhalosilanes are initially better spaced on the silica surface after grafting, whereas the aminosilanes likely cluster to a greater extent when grafted on the

  7. Short-term and seasonal soil nitrogen dynamics and recovery by bermudagrass irrigated with 15N labeled swine lagoon effluent

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The experiment was conducted at a commercial swine operation located in Lowndes County, Mississippi in an acid Vaiden silty clay (very fine, montmorillonitic, thermic Vertic Hapludalf) used in this study is representative of the Alabama and Mississippi Blackland Prairie major land resource area. A ...

  8. An implement for subsurface band application of poultry litter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Broiler litter is commonly used as a fertilizer on pastures and cropland. Poultry litter is typically land-applied by broadcasting the litter on the soil surface. Rain falling on soil to which poultry litter has been applied, may carry phosphorus (P) and nitrogen (N) nutrients from the soil into s...

  9. Food webs in Mongolian grasslands: the analysis of 13C and 15N natural abundances.

    PubMed

    Kohzu, Ayato; Iwata, T; Kato, M; Nishikawa, J; Wada, Eitaro; Amartuvshin, N; Namkhaidorj, B; Fujita, N

    2009-09-01

    Overgrazing often lowers species richness and productivity of grassland communities. For Mongolian grassland ecosystems, a lack of detailed information about food-web structures makes it difficult to predict the effects of overgrazing on species diversity and community composition. We analysed the delta13C and delta15N signatures of herbaceous plants, arthropods (grouped by feeding habit), wild and domestic mammals, and humans in central Mongolia to understand the predominant food-web pathways in this grassland ecosystem. The delta13C and delta15N values of mammals showed little variation within species, but varied considerably with slope position for arthropods. The apparent isotopic discrimination between body tissue and hair of mammals was estimated as 2.0 per thousand for delta13C and 2.1 per thousand for delta15N, which was large enough to cause overestimation of the trophic level of mammals if not taken into account when using hair samples to measure isotopic enrichment.

  10. 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 (Δδ >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

  11. 13C and 15N allocations of two alpine species from early and late snowmelt locations reflect their different growth strategies.

    PubMed

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

    2009-01-01

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

  12. Inoculation of Bacillus sphaericus UPMB-10 to Young Oil Palm and Measurement of Its Uptake of Fixed Nitrogen Using the 15N Isotope Dilution Technique

    PubMed Central

    Zakry, Fitri Abdul Aziz; Shamsuddin, Zulkifli H.; Rahim, Khairuddin Abdul; Zakaria, Zin Zawawi; Rahim, Anuar Abdul

    2012-01-01

    There are increasing applications of diazotrophic rhizobacteria in the sustainable agriculture system. A field experiment on young immature oil palm was conducted to quantify the uptake of N derived from N2 fixation by the diazotroph Bacillus sphaericus strain UPMB-10, using the 15N isotope dilution method. Eight months after 15N application, young immature oil palms that received 67% of standard N fertilizer application together with B. sphaericus inoculation had significantly lower 15N enrichment than uninoculated palms that received similar N fertilizers. The dilution of labeled N served as a marker for the occurrence of biological N2 fixation. The proportion of N uptake that was derived from the atmosphere was estimated as 63% on the whole plant basis. The inoculation process increased the N and dry matter yields of the palm leaflets and rachis significantly. Field planting of young, immature oil palm in soil inoculated with B. sphaericus UPMB-10 might mitigate inorganic fertilizer-N application through supplementation by biological nitrogen fixation. This could be a new and important source of nitrogen biofertilizer in the early phase of oil palm cultivation in the field. PMID:22446306

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    Background: The stable nucleus 15N is the mirror of 15O, the bottleneck in the hydrogen burning CNO cycle. Most of the 15N level widths below the proton emission threshold are known from just one nuclear resonance fluorescence (NRF) measurement, with limited precision in some cases. A recent experiment with the AGATA demonstrator array determined level lifetimes using the Doppler shift attenuation method in 15O. As a reference and for testing the method, level lifetimes in 15N have also been determined in the same experiment. Purpose: The latest compilation of 15N level properties dates back to 1991. The limited precision in some cases in the compilation calls for a new measurement to enable a comparison to the AGATA demonstrator data. The widths of several 15N levels have been studied with the NRF method. Method: The solid nitrogen compounds enriched in 15N have been irradiated with bremsstrahlung. The γ 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 γ -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. Volatile organic compounds from leaves litter.

    PubMed

    Isidorov, Valery; Jdanova, Maria

    2002-09-01

    Qualitative composition of volatile emissions of litter of five species of deciduous trees was investigated by GC-MS. The list of identified substances contains more than 70 organic compounds of various classes. It was established that the composition of components emitted by the litter into the gas phase greatly differs from that of essential oils extracted by hydrodistillation from turned leaves collected from trees during fall. It is suggested that most compounds found in litter emissions are products of vital activity of microorganisms decomposing it. The reported data indicate that after the vegetative period is over the decomposition processes of litter are important seasonal sources of reactive organic compounds under the forest canopy.

  15. 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.

  16. Organically treated biochar increases plant production and reduces N2O emissions: mechanistic insights by 15N tracing

    NASA Astrophysics Data System (ADS)

    Kammann, Claudia; Messerschmidt, Nicole; Clough, Tim; Schmidt, Hans-Peter; Marhan, Sven; Koyro, Hans-Werner; Steffens, Diedrich; Müller, Christoph

    2014-05-01

    Pyrogenic carbon (biochar) offers considerable potential for carbon capture and soil storage (CCSS) compared to other, less recalcitrant soil-C additives. Recent meta-analysis demonstrated that it can significantly reduce agricultural N2O emissions. Freshly produced biochars, however, do not always have yield-improving effects, i.e. there is no immediate economic incentive for using it. Hence, combining biochar with organic nutrient-rich amendments may be a promising agricultural strategy to accelerate CCSS, but it is unclear if biochar still reduces N2O emissions, in particular when it may act as nutrient carrier. We explored the potential of biochar to improve the GHG-cost/yield ratio and thereby its socio-economic value as soil amendment in two subsequent studies under controlled conditions: (1) A proof-of-concept study where the effects of untreated biochar were compared to those of co-composted biochar combined with stepwise improved nutritional regimes (+/- compost; +/- mineral-N application), and (2) a 15N-labeling-tracing study to unravel N exchange on biochar particles and N2O production and reduction mechanisms. Both studies were carried out in nutrient-poor sandy soils, the most likely initial target soils for biochar-CCSS strategies. While the untreated biochar reduced plant growth under N-limiting conditions, or at best did not reduce it, the co-composted biochar always significantly stimulated plant growth. The relative stimulation was largest with the lowest nutrient additions (305% versus 61% of control with untreated biochar). Electro-ultra-filtration analyses revealed that the co-composted but not the untreated biochar carried considerable amounts of easily extractable as well as more strongly sorbed plant nutrients, in particular nitrate and phosphorus. The subsequent 15N labelling-tracing study revealed that the co-composted biochar still (i) acted as a mineral-N exchange site for nitrate and ammonium despite its N-preloading, (ii) reduced N2O

  17. Can't See the Wood for the Litter: Evaluation of Litter Behavior Modification in a Forest

    ERIC Educational Resources Information Center

    Lindemann-Matthies, Petra; Bonigk, Isabel; Benkowitz, Dorothee

    2012-01-01

    This study investigated elementary school children's (n = 171) litter behavior during guided forest tours following two different treatments. Four classes received a verbal appeal not to litter in the forest, while another four classes received both a verbal appeal and a demonstration of the desired litter behavior (picking up litter, putting it…

  18. Interactive effects of litter quality and soil mineralogy on temperate forest soil carbon response to temperature

    NASA Astrophysics Data System (ADS)

    Rasmussen, C.; Horwath, W.; Southard, R.

    2007-12-01

    Temperate forest soil organic carbon (C) represents a significant pool of terrestrial C that may be released to the atmosphere as CO2 with predicted climate change. To address feedbacks between climate change and terrestrial C turnover, we quantified forest soil C response to litter quality and temperature change as a function of soil parent material. We collected soils from three conifer forest-types dominated by ponderosa pine (PP), white fir (WF), and red fir (RF) from each of three parent materials, granite (GR), basalt (BS), and andesite (AN) in the Sierra Nevada of California. AN soils were dominated by short-range-order (SRO) minerals, GR soils by crystalline minerals, and BS soils by a mix of crystalline and SRO minerals. Field soils were incubated in the laboratory at their mean annual soil temperature (MAST), with addition of native 13C-labeled litter. Further, we incubated WF and RF soils at PP MAST with 13C-labeled PP litter; and RF soils at WF MAST with 13C-labeled WF litter to simulate a migration of MAST and vegetation type up-elevation in response to predicted climate warming. Results indicated that total CO2 and percent of CO2 derived from soil C varied significantly across forest-types, following the pattern of GR>BS>AN. Regression analyses indicated significant control of C mineralization and soil C priming by litter quality and SRO minerals. Addition of litter derived water-soluble compounds enabled priming of recalcitrant soil C in soils with high SRO mineral content, whereas water-soluble litter components did little to promote priming of extant soil C in soils of low SRO mineral content. Results further indicated a 10-300% increase in WF and RF forest-type soil C mineralization under climate change conditions that varied substantially between parent materials. Soils derived from andesite exhibited minimal change; whereas granite and basalt derived soils lost large amounts of soil C under climate change conditions. This study corroborates the

  19. Water addition, evaporation and water holding capacity of poultry litter.

    PubMed

    Dunlop, Mark W; Blackall, Patrick J; Stuetz, Richard M

    2015-12-15

    Litter moisture content has been related to ammonia, dust and odour emissions as well as bird health and welfare. Improved understanding of the water holding properties of poultry litter as well as water additions to litter and evaporation from litter will contribute to improved litter moisture management during the meat chicken grow-out. The purpose of this paper is to demonstrate how management and environmental conditions over the course of a grow-out affect the volume of water A) applied to litter, B) able to be stored in litter, and C) evaporated from litter on a daily basis. The same unit of measurement has been used to enable direct comparison-litres of water per square metre of poultry shed floor area, L/m(2), assuming a litter depth of 5cm. An equation was developed to estimate the amount of water added to litter from bird excretion and drinking spillage, which are sources of regular water application to the litter. Using this equation showed that water applied to litter from these sources changes over the course of a grow-out, and can be as much as 3.2L/m(2)/day. Over a 56day grow-out, the total quantity of water added to the litter was estimated to be 104L/m(2). Litter porosity, water holding capacity and water evaporation rates from litter were measured experimentally. Litter porosity decreased and water holding capacity increased over the course of a grow-out due to manure addition. Water evaporation rates at 25°C and 50% relative humidity ranged from 0.5 to 10L/m(2)/day. Evaporation rates increased with litter moisture content and air speed. Maintaining dry litter at the peak of a grow-out is likely to be challenging because evaporation rates from dry litter may be insufficient to remove the quantity of water added to the litter on a daily basis.

  20. The degree of urbanization across the globe is not reflected in the δ(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 δ(15)N ratios increase with the amount of urbanization in coastal watersheds. However, there is little information on the relationship between urbanization and seagrass δ(15)N ratios on a global scale. We performed a meta-analysis on seagrass samples from 79 independent locations to test if seagrass δ(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 δ(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 δ(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 δ(15)N and latitude remain unknown.

  1. Direct measurements of protein backbone 15N spin relaxation rates from peak line-width using a fully-relaxed Accordion 3D HNCO experiment.

    PubMed

    Chen, Kang; Tjandra, Nico

    2009-03-01

    Protein backbone (15)N spin relaxation rates measured by solution NMR provide useful dynamic information with a site-specific resolution. The conventional method is to record a series of 2D (1)H-(15)N HSQC spectra with varied relaxation delays, and derive relaxation rate from the following curve fitting on the resonance intensities. Proteins with poorly resolved spectra often require several 3D HNCO spectra to be collected on a (15)N/(13)C double labeled protein sample. In order to reduce the relaxation dimension Carr et al. (P.A. Carr, D.A. Fearing, A.G. Palmer, 3D accordion spectroscopy for measuring N-15 and (CO)-Carbon-13 relaxation rates in poorly resolved NMR spectra, J. Magn. Reson. 132 (1998) 25-33) employed an Accordion type HNCO pulse sequence to obtain (15)N or (13)C T(1) relaxation rates by numerical fitting of the relaxation interfered free induction decay (FID) data. To avoid intensive analysis of the time domain data, we propose a modified protocol to measure (15)N T(1) and T(2) relaxation rates from easily obtained line-widths in an Accordion HNCO spectrum. Both T(1) and T(2) relaxation could be simultaneously convoluted into the constant-time evolution periods of (13)C' and (15)N, respectively. The relaxation delay was allowed to reach at least 3 x T(1) or 3 x T(2) so that the signal was substantially decayed by the end of the FID, and the resulting peak full-width at half height (FWHH) could be directly used to calculate relaxation rate. When applied to the 76-residue Ubiquitin and the 226-residue glutamine-binding protein (GlnBP), this method yielded T(1) and T(2) values deviating on average by 4-6% and 5-7%, respectively, from the measurements based on the conventional 2D method. In comparison, the conventional methods possessed intrinsic error ranges of 2-4% for T(1) and 3-6% for T(2). In addition to comparable accuracy, the fully-relaxed Accordion HNCO method presented here allowed measurements of relaxation rates for resonances unresolved in

  2. Compound-Specific δ15N Amino Acid Measurements in Littoral Mussels in the California Upwelling Ecosystem: A New Approach to Generating Baseline δ15N Isoscapes for Coastal Ecosystems

    PubMed Central

    Vokhshoori, Natasha L.; McCarthy, Matthew D.

    2014-01-01

    We explored δ15N 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 δ15N gradients in the California Upwelling Ecosystem (CUE), determining bulk δ15N 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 δ15N 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 δ15N trend is therefore most consistent with a baseline δ15N gradient, likely due to the mixing of two source waters: low δ15N 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 δ15N values of phenylalanine (δ15NPhe), the best AA proxy for baseline δ15N values. We hypothesize δ15NPhe values in intertidal mussels can approximate annual integrated δ15N values of coastal phytoplankton primary production. We therefore used δ15NPhe values to generate the first compound-specific nitrogen isoscape for the coastal Northeast Pacific, which indicates a remarkably linear gradient in coastal primary production δ15N values. We propose that δ15NPhe isoscapes derived from filter feeders can directly characterize baseline δ15N 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

  3. 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...

  4. 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...

  5. δ15N as a proxy for historic anthropogenic nitrogen loading in Charleston Harbor, SC, USA

    NASA Astrophysics Data System (ADS)

    Payne, T. N.; Andrus, C. F. T.

    2015-12-01

    Bivalve shell geochemistry can serve as a useful indicator of changes in coastal environments. There is increasing interest in developing paleoenvironmental proxies from mollusk shell organic components. Numerous studies have focused on how the δ15N obtained from bivalve tissues can be used to trace present-day wastewater input into estuaries. However, comparatively little attention has been paid to tracing the impact of anthropogenic nitrogen loading into estuaries over time. By measuring historic levels of δ15N in the organic fraction of oyster shells (Crassostrea virginica) from archaeological sites around Charleston Harbor and comparing those levels to the δ15N content of modern shells, it is possible to assess how nitrogen has fluctuated historically in the area. Whole-shell samples from the Late Archaic Period (~3000-4000 BP, Late Woodland Period (~1400-800 BP), 18th and 19th centuries, and modern controls were measured for %N and d15N. Evidence of increased anthropogenic input of N is expected to begin in the early historic period based on similar analysis in Chesapeake Bay. More ancient samples may give insight into baseline conditions prior to recent population growth and industrialization. This information could help understand how large-scale anthropogenic nitrogen loading has affected coastal ecosystems over time and guide future remediation. Furthermore, this project will help refine and improve this novel proxy of past environmental conditions.

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

    PubMed

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

    2015-11-21

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

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

    PubMed

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

    2009-06-01

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

  8. 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 ...

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

    PubMed

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

    2015-11-21

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

  10. Backbone 1H, 13C, and 15N NMR assignments for the Cyanothece 51142 protein cce_0567: a protein associated with nitrogen fixation in the DUF683 family

    SciTech Connect

    Buchko, Garry W.; Sofia, Heidi J.

    2008-06-01

    The recently sequenced genome of the diurnal cyanobacterium Cyanothece sp. PCC 51142 (contig 83.1_1_243_746) contains the sequence for an hypothetical protein that falls into the DUF683 family. As observed for the other 54 DUF683 proteins currently listed in the GenBank database, this 78-residue (9.0 kDa) protein in Cyanothece is also found in a nitrogen fixation gene cluster suggesting that it is involved in the process. To date no structural information exists for any of the proteins in the DUF683 family. In an effort to elucidate the biochemical role DUF683 may play in nitrogen fixation and to obtain structural information for a member of the DUF683 protein family, a construct containing DUF683 from Cyanothece 51142 was generated, expressed, purified, and the solution properties characterized. A total rotational correlation time (tc) of 17.1 ns was estimated by nuclear magnetic resonance (NMR) spectroscopy suggesting a molecular weight of ~ 40 kDa, an observation dictating that DUF683 is a tetramer in solution. Using triple-labeled (2H, 13C, 15N) and residue-specific 15N-labeled amino acids (L, K, V, and E/Q) samples, most of the backbone and side chain resonances for DUF683 were assigned. The 13C alpha chemical shifts and NOESY NMR data indicate that the protein is helical from K18-E75.

  11. Evaluating δ(15)N-body size relationships across taxonomic levels using hierarchical models.

    PubMed

    Reum, Jonathan C P; Marshall, Kristin N

    2013-12-01

    Ecologists routinely set out to estimate the trophic position of individuals, populations, and species composing food webs, and nitrogen stable isotopes (δ(15)N) are a widely used proxy for trophic position. Although δ(15)N values are often sampled at the level of individuals, estimates and confidence intervals are frequently sought for aggregations of individuals. If individual δ(15)N values are correlated as an artifact of sampling design (e.g., clustering of samples in space or time) or due to intrinsic groupings (e.g., life history stages, social groups, taxonomy), such estimates may be biased and exhibit overly optimistic confidence intervals. However, these issues can be accommodated using hierarchical modeling methods. Here, we demonstrate how hierarchical models offer an additional quantitative tool for investigating δ(15)N variability and we explicitly evaluate how δ(15)N varies with body size at successively higher levels of taxonomic aggregation in a diverse fish assemblage. The models take advantage of all available data, better account for uncertainty in parameters estimates, may improve inferences on coefficients corresponding to groups with small to moderate sample sizes, and partition variation across model levels, which provides convenient summaries of the 'importance' of each level in terms of unexplained heterogeneity in the data. These methods can easily be applied to diet-based studies of trophic position. Although hierarchical models are well-understood and established tools, their benefits have yet to be fully reaped by stable isotope and food web ecologists. We suggest that hierarchical models can provide a robust framework for conceptualizing and statistically modeling trophic position at multiple levels of aggregation. PMID:23812110

  12. Stable isotopes (δ13C and δ15N) 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 (δ13C and δ18O) 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 (δ13C and δ15N) of an organic skeletal compartment, the coral skeletal organic matrix (OM). Mean OM δ13C in symbiotic and nonsymbiotic corals was similar (-26.08‰ vs. -24.31‰), but mean OM δ15N 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 δ15N 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 δ15N 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

  13. A simple method for N-15 labelling of exocyclic amino groups in synthetic oligodeoxynucleotides

    PubMed Central

    Acedo, Montse; Fàbrega, Carme; Aviño, Anna; Goodman, Myron; Fagan, Patricia; Wemmer, David; Eritja, Ramon

    1994-01-01

    The use of the ammonia deprotection step to introduce 15N labels at specific exocyclic amino positions of adenine, cytosine, guanine or 2-aminopurine of oligodeoxynucleotides is described. PMID:8065910

  14. Watching eyes on potential litter can reduce littering: evidence from two field experiments.

    PubMed

    Bateson, Melissa; Robinson, Rebecca; Abayomi-Cole, Tim; Greenlees, Josh; O'Connor, Abby; Nettle, Daniel

    2015-01-01

    Littering constitutes a major societal problem, and any simple intervention that reduces its prevalence would be widely beneficial. In previous research, we have found that displaying images of watching eyes in the environment makes people less likely to litter. Here, we investigate whether the watching eyes images can be transferred onto the potential items of litter themselves. In two field experiments on a university campus, we created an opportunity to litter by attaching leaflets that either did or did not feature an image of watching eyes to parked bicycles. In both experiments, the watching eyes leaflets were substantially less likely to be littered than control leaflets (odds ratios 0.22-0.32). We also found that people were less likely to litter when there other people in the immediate vicinity than when there were not (odds ratios 0.04-0.25) and, in one experiment but not the other, that eye leaflets only reduced littering when there no other people in the immediate vicinity. We suggest that designing cues of observation into packaging could be a simple but fruitful strategy for reducing littering. PMID:26644979

  15. Watching eyes on potential litter can reduce littering: evidence from two field experiments.

    PubMed

    Bateson, Melissa; Robinson, Rebecca; Abayomi-Cole, Tim; Greenlees, Josh; O'Connor, Abby; Nettle, Daniel

    2015-01-01

    Littering constitutes a major societal problem, and any simple intervention that reduces its prevalence would be widely beneficial. In previous research, we have found that displaying images of watching eyes in the environment makes people less likely to litter. Here, we investigate whether the watching eyes images can be transferred onto the potential items of litter themselves. In two field experiments on a university campus, we created an opportunity to litter by attaching leaflets that either did or did not feature an image of watching eyes to parked bicycles. In both experiments, the watching eyes leaflets were substantially less likely to be littered than control leaflets (odds ratios 0.22-0.32). We also found that people were less likely to litter when there other people in the immediate vicinity than when there were not (odds ratios 0.04-0.25) and, in one experiment but not the other, that eye leaflets only reduced littering when there no other people in the immediate vicinity. We suggest that designing cues of observation into packaging could be a simple but fruitful strategy for reducing littering.

  16. Broiler litter management effects on the nutrient composition of the litter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Application of poultry litter as a fertilizer source is a common practice in agriculture production. However, potential water quality concerns as a result of over application of poultry litter has risen as a major environmental issue in states with substantial poultry production. Fundamental to the ...

  17. Watching eyes on potential litter can reduce littering: evidence from two field experiments

    PubMed Central

    Bateson, Melissa; Robinson, Rebecca; Abayomi-Cole, Tim; Greenlees, Josh; O’Connor, Abby

    2015-01-01

    Littering constitutes a major societal problem, and any simple intervention that reduces its prevalence would be widely beneficial. In previous research, we have found that displaying images of watching eyes in the environment makes people less likely to litter. Here, we investigate whether the watching eyes images can be transferred onto the potential items of litter themselves. In two field experiments on a university campus, we created an opportunity to litter by attaching leaflets that either did or did not feature an image of watching eyes to parked bicycles. In both experiments, the watching eyes leaflets were substantially less likely to be littered than control leaflets (odds ratios 0.22–0.32). We also found that people were less likely to litter when there other people in the immediate vicinity than when there were not (odds ratios 0.04–0.25) and, in one experiment but not the other, that eye leaflets only reduced littering when there no other people in the immediate vicinity. We suggest that designing cues of observation into packaging could be a simple but fruitful strategy for reducing littering. PMID:26644979

  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

  19. Lignin degradation during plant litter photodegradation

    NASA Astrophysics Data System (ADS)

    Lin, Y.; King, J. Y.

    2014-12-01

    Lignin is the second most abundant compound, after cellulose, synthesized by plants. Numerous studies have demonstrated that initial lignin concentration is negatively correlated with litter decomposition rate under both laboratory and field conditions. Thus lignin is commonly considered to be a "recalcitrant" compound during litter decomposition. However, lignin can also serve as a radiation-absorbing compound during photodegradation, the process through which solar radiation breaks down organic matter. Here, we synthesize recent studies concerning lignin degradation during litter photodegradation and report results from our study on how photodegradation changes lignin chemistry at a molecular scale. Recent field studies have found that litter with high initial lignin concentration does not necessarily exhibit high mass loss during photodegradation. A meta-analysis (King et al. 2012) even found a weak negative correlation between initial lignin concentration and photodegradation rate. Contradicting results have been reported with regard to the change in lignin concentration during photodegradation. Some studies have found significant loss of lignin during photodegradation, while others have not. In most studies, loss of lignin only accounts for a small proportion of the overall mass loss. Using NMR spectroscopy, we found significant loss of lignin structural units containing beta-aryl ether linkages during photodegradation of a common grass litter, Bromus diandrus, even though conventional forage fiber analysis did not reveal changes in lignin concentration. Both our NMR and fiber analyses supported the idea that photodegradation induced loss of hemicellulose, which was mainly responsible for the litter mass loss during photodegradation. Our results suggest that photodegradation induces degradation, but not necessarily complete breakdown, of lignin structures and consequently exposes hemicellulose and cellulose to microbial decomposition. We conclude that lignin

  20. Influence of open ocean nitrogen supply on the skeletal δ15N of modern shallow-water scleractinian corals

    NASA Astrophysics Data System (ADS)

    Wang, Xingchen T.; Sigman, Daniel M.; Cohen, Anne L.; Sinclair, Daniel J.; Sherrell, Robert M.; Cobb, Kim M.; Erler, Dirk V.; Stolarski, Jarosław; Kitahara, Marcelo V.; Ren, Haojia

    2016-05-01

    The isotopic composition of skeleton-bound organic nitrogen in shallow-water scleractinian corals (hereafter, CS-δ15N) is an emerging tool for studying the marine nitrogen cycle in the past. The CS-δ15N has been shown to reflect the δ15N of nitrogen (N) sources to corals, with most applications to date focusing on the anthropogenic/terrestrial N inputs to reef environments. However, many coral reefs receive their primary N sources from the open ocean, and the CS-δ15N of these corals may provide information on past changes in the open ocean regional and global N cycle. Using a recently developed persulfate/denitrifier-based method, we measured CS-δ15N in modern shallow-water scleractinian corals from 8 sites proximal to the open ocean. At sites with low open ocean surface nitrate concentrations typical of the subtropics and tropics, measured CS-δ15N variation on seasonal and annual timescales is most often less than 2‰. In contrast, a broad range in CS-δ15N (of ∼10‰) is measured across these sites, with a strong correlation between CS-δ15N and the δ15N of the deep nitrate supply to the surface waters near the reefs. While CS-δ15N can be affected by other N sources as well and can vary in response to local reef conditions as well as coral/symbiont physiological changes, this survey indicates that, when considering corals proximal to the open ocean, the δ15N of the subsurface nitrate supply to surface waters drives most of the CS-δ15N variation across the global ocean. Thus, CS-δ15N is a promising proxy for reconstructing the open ocean N cycle in the past.

  1. Gas chromatography-mass spectrometry of N-heptafluorobutyryl isobutyl esters of amino acids in the analysis of the kinetics of (/sup 15/N)H/sub 4//sup +/ assimilation in Lemna minor L

    SciTech Connect

    Rhodes, D.; Myers, A.C.; Jamieson, G.

    1981-11-01

    Rapid, sensitive, and selective methods for the determination of the /sup 15/N abundance of amino acids in isotopic tracer experiments with plant tissues are described and discussed. Methodology has been directly tested in an analysis of the kinetics of (/sup 15/N)H/sub 4//sup +/ assimilation in Lemna minor L. The techniques utilize gas chromatography-mass spectrometry selected ion monitoring of major fragments containing the N moiety of N-heptafluorobutyryl isobutyl esters of amino acids. The ratio of selected ion pairs at the characteristic retention time of each amino acid derivative can be used to calcuulate /sup 15/N abundance with an accuracy of +/- 1 atom % excess /sup 15/N using samples containing as little as 30 picomoles of individual amino acids. Up to 11 individual amino acid derivatives can be selectively monitored in a single chromatogram of 30 minutes. It is suggested that these techniques will be useful in situations where the small quantities of N available for analysis have hitherto hindered the use of /sup 15/N-labeled precursors.

  2. Understanding litter decomposition in drylands: Is litter abrasion an important abiotic factor?

    NASA Astrophysics Data System (ADS)

    Peterson, M.; Bravo-Garza, M. R.; Throop, H. L.; Duarte, L. C.

    2012-12-01

    Drylands comprise approximately 40% of global land cover and about 20% of global soil organic carbon (C) pool. Changes in dryland ecosystem processes, such as litter decomposition, could greatly influence global C cycling and climate change. Current models underestimate rates of litter decomposition in drylands, and little is known about the role and interactions of abiotic drivers in these systems. Research suggests leaf abrasion may play an important role on litter decomposition in drylands by increasing microbial activity or leaching. The Scrape Site at Jornada LTER was stripped of vegetation in 1991, leaving exposed soil that could serve as a source of sand particles to promote leaf abrasion on mesquite shrubs located downwind. This project examines the role that leaf abrasion, promoted in the field by wind erosion, and induced through laboratory simulations, will play in litter decomposition. We hypothesize that leaf abrasion will increase rates of litter decomposition due to facilitation of microbial colonization. Mesquite leaves were collected from two locations: down-wind from the Scrape Site and 80 meters away representing "field abraded" and "unabraded" treatments, respectively. For a "lab abraded" treatment, abrasion was performed by shaking leaves for 30 seconds with sand particles to simulate microscopic characteristics seen in "field abraded" treatment; this treatment resulted in an average leaf area loss of 3.267 %. Differences in decomposition rates among litter treatments were evaluated in a 16 week laboratory incubation. Litter was incubated at 22°C in airtight glass jars containing 50 g of soil (0.053 g water g-1 soil). Rapid colonization by fungi was apparent across treatments, but lab abraded litter showed the most abundant growth. Consequently, lab abraded litter treatment showed 20% and 30% times more accumulation of CO2 -C than field (P= 0.0008) and unabraded (P< 0.0001) litter treatments during the first 6 days of incubation. These results

  3. Broiler diet modification and litter storage: impacts on phosphorus in litters, soils, and runoff.

    PubMed

    McGrath, Joshua M; Sims, J Thomas; Maguire, Rory O; Saylor, William W; Angel, C Roselina; Turner, Benjamin L

    2005-01-01

    Modifying broiler diets to mitigate water quality concerns linked to excess phosphorus (P) in regions of intensive broiler production has recently increased. Our goals were to evaluate the effects of dietary modification, using phytase and reduced non-phytate phosphorus (NPP) supplementation, on P speciation in broiler litters, changes in litter P forms during long-term storage, and subsequent impacts of diets on P in runoff from litter-amended soils. Four diets containing two levels of NPP with and without phytase were fed to broilers in a three-flock floor pen study. After removal of the third flock, litters were stored for 440 d at their initial moisture content (MC; 24%) and at a MC of 40%. Litter P fractions and orthophosphate and phytate P concentrations were determined before and after storage. After storage, litters were incorporated with a sandy and silt loam and simulated rainfall was applied. Phytase and reduced dietary NPP significantly reduced litter total P. Reducing dietary NPP decreased water-extractable inorganic phosphorus (IP) and the addition of dietary phytase reduced NaOH- and HCl-extractable organic P in litter, which correlated well with orthophosphate and phytic acid measured by 31P nuclear magnetic resonance (NMR), respectively. Although dry storage caused little change in P speciation, wet storage increased concentrations of water-soluble IP, which increased reactive P in runoff from litter-amended soils. Therefore, diet modification with phytase and reduced NPP could be effective in reducing P additions on a watershed scale. Moreover, efforts to minimize litter MC during storage may reduce the potential for dissolved P losses in runoff.

  4. Broiler diet modification and litter storage: impacts on phosphorus in litters, soils, and runoff.

    PubMed

    McGrath, Joshua M; Sims, J Thomas; Maguire, Rory O; Saylor, William W; Angel, C Roselina; Turner, Benjamin L

    2005-01-01

    Modifying broiler diets to mitigate water quality concerns linked to excess phosphorus (P) in regions of intensive broiler production has recently increased. Our goals were to evaluate the effects of dietary modification, using phytase and reduced non-phytate phosphorus (NPP) supplementation, on P speciation in broiler litters, changes in litter P forms during long-term storage, and subsequent impacts of diets on P in runoff from litter-amended soils. Four diets containing two levels of NPP with and without phytase were fed to broilers in a three-flock floor pen study. After removal of the third flock, litters were stored for 440 d at their initial moisture content (MC; 24%) and at a MC of 40%. Litter P fractions and orthophosphate and phytate P concentrations were determined before and after storage. After storage, litters were incorporated with a sandy and silt loam and simulated rainfall was applied. Phytase and reduced dietary NPP significantly reduced litter total P. Reducing dietary NPP decreased water-extractable inorganic phosphorus (IP) and the addition of dietary phytase reduced NaOH- and HCl-extractable organic P in litter, which correlated well with orthophosphate and phytic acid measured by 31P nuclear magnetic resonance (NMR), respectively. Although dry storage caused little change in P speciation, wet storage increased concentrations of water-soluble IP, which increased reactive P in runoff from litter-amended soils. Therefore, diet modification with phytase and reduced NPP could be effective in reducing P additions on a watershed scale. Moreover, efforts to minimize litter MC during storage may reduce the potential for dissolved P losses in runoff. PMID:16151241

  5. Effects of a trait-based parameterisation of litter decomposition

    NASA Astrophysics Data System (ADS)

    Kleinen, Thomas; Brovkin, Victor; van Bodegom, Peter; Kattge, Jens; Wirth, Christian

    2013-04-01

    Stocks of plant litter play an important role in the terrestrial carbon cycle. On a regional scale, litter stocks influence fire regimes, soil fertility, and soil organic matter formation. On the global scale, these factors influence global CO2 and climate. In many dynamic global vegetation models, the decomposition of plant litter is treated rather simplistically by aggregating leaf and woody litter into a single litter pool and using a common decomposition rate for all litter pools without taking different plant species or litter types into account. Measurements, on the other hand, clearly show that a) leaf litter decomposes much faster than woody litter, b) litter from different plant species decomposes at different rates, and c) the temperature sensitivity of woody litter decomposition also is species-dependent. The common modelling approach therefore clearly is incompatible with measurements. As a consequence, we modified the dynamic global vegetation model LPJ by a) introducing different litter pools for leaf and woody litter and by b) linking plant functional types to decomposition rates, as well as temperature sensitivities, of wood and leaf litter determined from two databases of plant traits. These changes give a more realistic distribution of litter stocks in most biomes, with the exception of boreal forests. In a projection for future climate, using the SRES A2 scenario, the modified parameterisation leads to an increase in litter stocks by 35 PgC, as well as a decrease in atmospheric CO2 by 3 ppm by 2100. Despite the increase in litter stocks, the fire emissions increase less than when using the original parameterization, since the litter is redistributed to more humid regions.

  6. Photodegradation of roxarsone in poultry litter leachates

    USGS Publications Warehouse

    Bednar, A.J.; Garbarino, J.R.; Ferrer, I.; Rutherford, D.W.; Wershaw, R. L.; Ranville, J.F.; Wildeman, T.R.

    2003-01-01

    Arsenic compounds have been used extensively in agriculture in the US for applications ranging from cotton herbicides to animal feed supplements. Roxarsone (3-nitro-4-hydroxyphenylarsonic acid), in particular, is used widely in poultry production to control coccidial intestinal parasites. It is excreted unchanged in the manure and introduced into the environment when litter is applied to farmland as fertilizer. Although the toxicity of roxarsone is less than that of inorganic arsenic, roxarsone can degrade, biotically and abiotically, to produce more toxic inorganic forms of arsenic, such as arsenite and arsenate. Experiments were conducted on aqueous litter leachates to test the stability of roxarsone under different conditions. Laboratory experiments have shown that arsenite can be cleaved photolytically from the roxarsone moiety at pH 4-8 and that the degradation rate increases with increasing pH. Furthermore, the rate of photodegradation increases with nitrate and natural organic matter concentration, reactants that are commonly found in poultry-litter-water leachates. Additional photochemical reactions rapidly oxidize the cleaved arsenite to arsenate. The formation of arsenate is not entirely undesirable, because it is less mobile in soil systems and less toxic than arsenite. A possible mechanism for the degradation of roxarsone in poultry litter leachates is proposed. The results suggest that poultry litter storage and field application practices could affect the degradation of roxarsone and subsequent mobilization of inorganic arsenic species. ?? 2002 Elsevier Science B.V. All rights reserved.

  7. 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

  8. Evaluation of broiler litter transportation in northern Alabama, USA.

    PubMed

    Paudel, Krishna P; Adhikari, Murali; Martin, Neil R

    2004-10-01

    The profitability of using broiler litter as a source of crop nutrients was calculated using a phosphorus-consistent litter application rule. A ton of litter can cost effectively be transported up to 164 miles from the production facility. A cost-minimizing phosphorus-consistent transportation model developed to meet the nutrient needs of 29 counties in northern Alabama revealed that not all of the litter can be utilized in the region. The total cost increased when transportation of the litter out of the heavily surplus counties was prioritized. Total litter use was minimally affected by changes in chemical fertilizer prices. Shadow prices indicated the robustness of the model.

  9. Biological and climatic controls on leaf litter decomposition across European forests and grasslands revealed by reciprocal litter transplantation experiments

    NASA Astrophysics Data System (ADS)

    Portillo-Estrada, M.; Pihlatie, M.; Korhonen, J. F. J.; Levula, J.; Frumau, A. K. F.; Ibrom, A.; Lembrechts, J. J.; Morillas, L.; Horváth, L.; Jones, S. K.; Niinemets, Ü.

    2015-11-01

    Projection of carbon and nitrogen cycles to future climates is associated with large uncertainties, in particular due to uncertainties how changes in climate alter soil turnover, including litter decomposition. In addition, future conditions are expected to result in changes in vegetation composition, and accordingly in litter type and quality, but it is unclear how such changes could potentially alter litter decomposition. Litter transplantation experiments were carried out across 6 European sites (4 forest and 2 grasslands) spanning a large geographical and climatic gradient (5.6-11.4 °C in annual temperature 511-878 mm in precipitation) to gain insight into biological (litter origin and type, soil type) and climatic controls on litter decomposition. The decomposition k rates were overall higher in warmer and wetter sites than in colder and drier sites, and positively correlated to the litter total specific leaf area. Also, litter N content increased as less litter mass remained and decay went further. Surprisingly, this study demonstrates that climatic controls on litter decomposition are quantitatively more important than species, litter origin and soil type. Cumulative climatic variables, precipitation and air temperature (ignoring days with air temperatures below 0 °C), were appropriate to predict the litter remaining mass during decomposition (Mr). And Mr and cumulative air temperature were found to be the best predictors for litter carbon and nitrogen remaining during decomposition. We concluded with an equation for predicting the decomposition k rate by using mean annual air temperature and litter total specific leaf area.

  10. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  12. 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

  13. Uptake and distribution of nitrogen from acidic fog within a ponderosa pine (Pinus ponderosa Laws.)/litter/soil system

    SciTech Connect

    Fenn, M.E.; Leininger, T.D.

    1995-11-01

    The magnitude and importance of wet deposition of N in forests of the South Coast (Los Angeles) Air Basin have not been well characterized. We exposed 3-yr-old ponderosa pine (Pinus ponderosa Laws.) seedlings growing in native forest soil to acidic fog treatments (pH 3.1) simulating fog chemistry from a pine forest near Los Angeles, California. Fog solutions contained either {sup 15}NH{sub 4}{sup +}, {sup 15}NO{sub 3}{sup {minus}}, or unlabeled N. The fog treatments were applied in open-top chambers in six 5-hr exposures. Soil treatments within each of the fog exposures were bare soil, soil overlain with L- and F-litter, and soil covered with plastic during the fog events to prevent fogwater from contacting soil. Seedlings were harvested and samples were collected 15 wk after the fog treatments. Uptake of {sup 15}N by roots was by far the dominant pathway for plant assimilation of fog-deposited {sup 15}N. Deposition of N in fog supplied 9.4% and 8.7% of the total N in current-year crown biomass in the litter-overlay and bare-soil treatments, respectively. Total N concentrations in every plant fraction except current-year stems were significantly higher in the bare-soil treatment than in the plastic-covered soil treatment. Less than 5% of the {sup 15}N deposited directly to the seedling crowns was retained by the plants in the covered-soil treatment, whereas 57% of the {sup 15}N deposited to the seedling/litter/soil systems was incorporated into plant biomass. The litter layers retained {sup 15}NH{sub 4}{sup +} more effectively than {sup 15}NH{sub 4}{sup +} more effectively than {sup 15}NO{sub 3}. Data from this study suggest that N deposited from fog may be an important source of N for plant growth in forests of the SCAB where fog occurrence and pollution exposure coincide. 5 refs., 5 figs., 3 tabs.

  14. Catalytic Roles of βLys87 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 βLys87 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). ε-15N-lysine TS was prepared to access the protonation state of βLys87 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 ε-amino group switches between protonated and neutral states as the β-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

  15. Natural abundance 14N and 15N solid-state NMR of pharmaceuticals and their polymorphs

    DOE PAGES

    Veinberg, Stanislav L.; Johnston, Karen E.; Jaroszewicz, Michael J.; Kispal, Brianna M.; Mireault, Christopher R.; Kobayashi, Takeshi; Pruski, Marek; Schurko, Robert W.

    2016-06-08

    14N ultra-wideline (UW), 1H{15N} indirectly-detected HETCOR (idHETCOR) and 15N dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) experiments, in combination with plane-wave density functional theory (DFT) calculations of 14N EFG tensors, were utilized to characterize a series of nitrogen-containing active pharmaceutical ingredients (APIs), including HCl salts of scopolamine, alprenolol, isoprenaline, acebutolol, dibucaine, nicardipine, and ranitidine. Here, a case study applying these methods for the differentiation of polymorphs of bupivacaine HCl is also presented. All experiments were conducted upon samples with naturally-abundant nitrogen isotopes. For most of the APIs, it was possible to acquire frequency-stepped UW 14N SSNMR spectra of stationarymore » samples, which display powder patterns corresponding to pseudo-tetrahedral (i.e., RR'R"NH+ and RR'NH2+) or other (i.e., RNH2 and RNO2) nitrogen environments.« less

  16. 1H, 13C and 15N NMR assignments of phenazopyridine derivatives.

    PubMed

    Burgueño-Tapia, Eleuterio; Mora-Pérez, Yolanda; Morales-Ríos, 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.

  17. Using delta15N values to characterise the nitrogen nutrient pathways from intensive animal units.

    PubMed

    Skinner, R A; Ineson, P; Jones, H; Sleep, D; Rank, R

    2006-01-01

    Previous studies on foliar delta15N values, in certain bryophytes, have indicated signature similarities to source pollutants. The object of this study was to investigate the effect further, by examining the mechanisms whereby isotopic fractionation occurs in systems such as atmospheric ammonia (NH3), throughfall, vegetation and soil. Measurements taken in and around point emission sources will then be used to characterise the various fractionation effects associated with these N transformations, as well as to demonstrate some of the issues associated with using delta15N values as pollution indicators. The atmospheric dispersion model UK-ADMS has also been used to model atmospheric delta15NH3 emissions, with signatures exhibiting marked negative shifts immediately downwind of an agricultural NH3 source. Similar dispersion patterns were mapped for NH3 concentration data illustrating the link between these two forms of measurement.

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Isoscapes have greatly improved our ability to understand biogeochemical processes on continental to global scales. However, the isoscapes framework may also have significant potential to resolve the spatial component of within-community interactions. For example, exotic plant invaders often exert strong impacts on ecosystem functioning, particularly regarding water-, carbon- and nutrient-cycles, but the spatial extent of such alterations is largely unknown. Here we show that massive N input by the N2-fixing exotic invasive Acacia longifolia to a Portuguese dune system can be traced using spatially resolved information on native plants' leaf δ15N. We found isotopic signatures of N to differ strongly between the native system (δ15N c. -10 o) and the atmospherically derived N in A. longifolia phyllodes (δ15N c. 0 o). Thus, sources of N for native plants could be readily distinguished. Leaf δ15N 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.

  1. 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.

  2. Control of climate and litter quality on leaf litter decomposition in different climatic zones.

    PubMed

    Zhang, Xinyue; Wang, Wei

    2015-09-01

    Climate and initial litter quality are the major factors influencing decomposition rates on large scales. We established a comprehensive database of terrestrial leaf litter decomposition, including 785 datasets, to examine the relationship between climate and litter quality and evaluate the factors controlling decomposition on a global scale, the arid and semi-arid (AS) zone, the humid middle and humid low (HL) latitude zones. Initial litter nitrogen (N) and phosphorus (P) concentration only increased with mean annual temperature (MAT) in the AS zone and decreased with mean annual precipitation (MAP) in the HL zone. Compared with nutrient content, MAT imposed less effect on initial litter lignin content than MAP. MAT were the most important decomposition driving factors on a global scale as well as in different climatic zones. MAP only significantly affected decomposition constants in AS zone. Although litter quality parameters also showed significant influence on decomposition, their importance was less than the climatic factors. Besides, different litter quality parameters exerted significant influence on decomposition in different climatic zones. Our results emphasized that climate consistently exerted important effects on decomposition constants across different climatic zones.

  3. Food webs in Mongolian grasslands: the analysis of 13C and 15N natural abundances.

    PubMed

    Kohzu, Ayato; Iwata, T; Kato, M; Nishikawa, J; Wada, Eitaro; Amartuvshin, N; Namkhaidorj, B; Fujita, N

    2009-09-01

    Overgrazing often lowers species richness and productivity of grassland communities. For Mongolian grassland ecosystems, a lack of detailed information about food-web structures makes it difficult to predict the effects of overgrazing on species diversity and community composition. We analysed the delta13C and delta15N signatures of herbaceous plants, arthropods (grouped by feeding habit), wild and domestic mammals, and humans in central Mongolia to understand the predominant food-web pathways in this grassland ecosystem. The delta13C and delta15N values of mammals showed little variation within species, but varied considerably with slope position for arthropods. The apparent isotopic discrimination between body tissue and hair of mammals was estimated as 2.0 per thousand for delta13C and 2.1 per thousand for delta15N, which was large enough to cause overestimation of the trophic level of mammals if not taken into account when using hair samples to measure isotopic enrichment. PMID:19507080

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

    PubMed

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

    2015-08-15

    A fine-scale survey of δ(15)N, δ(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 δ(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. δ(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.

  5. (15)N- and (2)H proteomic stable isotope probing links nitrogen flow to archaeal heterotrophic activity.

    PubMed

    Justice, Nicholas B; Li, Zhou; Wang, Yingfeng; Spaudling, Susan E; Mosier, Annika C; Hettich, Robert L; Pan, Chongle; Banfield, Jillian F

    2014-10-01

    Understanding how individual species contribute to nutrient transformations in a microbial community is critical to prediction of overall ecosystem function. We conducted microcosm experiments in which floating acid mine drainage (AMD) microbial biofilms were submerged - recapitulating the final stage in a natural biofilm life cycle. Biofilms were amended with either (15)NH4(+) or deuterium oxide ((2)H2O) and proteomic stable isotope probing (SIP) was used to track the extent to which different members of the community used these molecules in protein synthesis across anaerobic iron-reducing, aerobic iron-reducing and aerobic iron-oxidizing environments. Sulfobacillus spp. synthesized (15)N-enriched protein almost exclusively under iron-reducing conditions whereas the Leptospirillum spp. synthesized (15)N-enriched protein in all conditions. There were relatively few (15)N-enriched archaeal proteins, and all showed low atom% enrichment, consistent with Archaea synthesizing protein using the predominantly (14)N biomass derived from recycled biomolecules. In parallel experiments using (2)H2O, extensive archaeal protein synthesis was detected in all conditions. In contrast, the bacterial species showed little protein synthesis using (2)H2O. The nearly exclusive ability of Archaea to synthesize proteins using (2)H2O may be due to archaeal heterotrophy, whereby Archaea offset deleterious effects of (2)H by accessing (1)H generated by respiration of organic compounds.

  6. Nutrition Labeling

    NASA Astrophysics Data System (ADS)

    Metzger, Lloyd E.

    Nutrition labeling regulations differ in countries around the world. The focus of this chapter is on nutrition labeling regulations in the USA, as specified by the Food and Drug Administration (FDA) and the Food Safety and Inspection Service (FSIS) of the United States Department of Agriculture (USDA). A major reason for analyzing the chemical components of foods in the USA is nutrition labeling regulations. Nutrition label information is not only legally required in many countries, but also is of increasing importance to consumers as they focus more on health and wellness.

  7. REDOR NMR of stable-isotope-labeled protein binding sites

    SciTech Connect

    Schaefer, J.

    1994-12-01

    Rotational-echo, double resonance (REDOR) NMR, a new analytical spectroscopic technique for solids spinning at the magic angle, has been developed over the last 5 years. REDOR provides a direct measure of heteronuclear dipolar coupling between isolated pairs of labeled nuclei. In a solid with a {sup 13}C-{sup 15}N labeled pair, for example, the {sup 13}C rotational echoes that form each rotor period following a{sup 1}H-{sup 13}C cross-polarization transfer can be prevented from reaching full intensity by insertion of a {sup 15}N {pi} pulse each half rotor period. The REDOR difference (the difference between a {sup 13}C NMR spectrum obtained under these conditions and one obtained with no {sup 15}N {pi} pulses) has a strong dependence on the {sup 13}C-{sup 15}N dipolar coupling, and hence, the {sup 13}C-{sup 15}N internuclear distance. REDOR is described as double-resonance even though three radio frequencies (typically {sup 1}H, {sup 13}C, and {sup 15}N) are used because the protons are removed from the important evolution part of the experiment by resonant decoupling. The dephasing of magnetization in REDOR arises from a local dipolar {sup 13}C-{sup 15}N field gradient and involves no polarization transfer. REDOR has no dependence on {sup 13}C or {sup 15}N chemical-shift tensors and does not require resolution of a {sup 13}C-{sup 15}N coupling in the chemical-shift dimension.

  8. INVASIVE GRASS ALTERS LITTER DECOMPOSITION BY INFLUENCING MACRO-DETRITIVORES

    EPA Science Inventory

    Nitrogen fertilization experiments have produced results with inconsistent rates of plant litter decomposition, a phenomenon that may be explained if the influence of animal detritivores (macro-detritivores) on litter mass loss is greater than that of microbial decomposers whose ...

  9. The origin of litter chemical complexity during decomposition.

    PubMed

    Wickings, Kyle; Grandy, A Stuart; Reed, Sasha C; Cleveland, Cory C

    2012-10-01

    The chemical complexity of decomposing plant litter is a central feature shaping the terrestrial carbon (C) cycle, but explanations of the origin of this complexity remain contentious. Here, we ask: How does litter chemistry change during decomposition, and what roles do decomposers play in these changes? During a long-term (730 days) litter decomposition experiment, we tracked concurrent changes in decomposer community structure and function and litter chemistry using high-resolution molecular techniques. Contrary to the current paradigm, we found that the chemistry of different litter types diverged, rather than converged, during decomposition due to the activities of decomposers. Furthermore, the same litter type exposed to different decomposer communities exhibited striking differences in chemistry, even after > 90% mass loss. Our results show that during decomposition, decomposer community characteristics regulate changes in litter chemistry, which could influence the functionality of litter-derived soil organic matter (SOM) and the turnover and stabilisation of soil C. PMID:22897741

  10. The origin of litter chemical complexity during decomposition.

    PubMed

    Wickings, Kyle; Grandy, A Stuart; Reed, Sasha C; Cleveland, Cory C

    2012-10-01

    The chemical complexity of decomposing plant litter is a central feature shaping the terrestrial carbon (C) cycle, but explanations of the origin of this complexity remain contentious. Here, we ask: How does litter chemistry change during decomposition, and what roles do decomposers play in these changes? During a long-term (730 days) litter decomposition experiment, we tracked concurrent changes in decomposer community structure and function and litter chemistry using high-resolution molecular techniques. Contrary to the current paradigm, we found that the chemistry of different litter types diverged, rather than converged, during decomposition due to the activities of decomposers. Furthermore, the same litter type exposed to different decomposer communities exhibited striking differences in chemistry, even after > 90% mass loss. Our results show that during decomposition, decomposer community characteristics regulate changes in litter chemistry, which could influence the functionality of litter-derived soil organic matter (SOM) and the turnover and stabilisation of soil C.

  11. 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

  12. Natural abundance (14)N and (15)N solid-state NMR of pharmaceuticals and their polymorphs.

    PubMed

    Veinberg, Stanislav L; Johnston, Karen E; Jaroszewicz, Michael J; Kispal, Brianna M; Mireault, Christopher R; Kobayashi, Takeshi; Pruski, Marek; Schurko, Robert W

    2016-06-29

    (14)N ultra-wideline (UW), (1)H{(15)N} indirectly-detected HETCOR (idHETCOR) and (15)N dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) experiments, in combination with plane-wave density functional theory (DFT) calculations of (14)N EFG tensors, were utilized to characterize a series of nitrogen-containing active pharmaceutical ingredients (APIs), including HCl salts of scopolamine, alprenolol, isoprenaline, acebutolol, dibucaine, nicardipine, and ranitidine. A case study applying these methods for the differentiation of polymorphs of bupivacaine HCl is also presented. All experiments were conducted upon samples with naturally-abundant nitrogen isotopes. For most of the APIs, it was possible to acquire frequency-stepped UW (14)N SSNMR spectra of stationary samples, which display powder patterns corresponding to pseudo-tetrahedral (i.e., RR'R''NH(+) and RR'NH2(+)) or other (i.e., RNH2 and RNO2) nitrogen environments. Directly-excited (14)N NMR spectra were acquired using the WURST-CPMG pulse sequence, which incorporates WURST (wideband, uniform rate, and smooth truncation) pulses and a CPMG (Carr-Purcell Meiboom-Gill) refocusing protocol. In certain cases, spectra were acquired using (1)H → (14)N broadband cross-polarization, via the BRAIN-CP (broadband adiabatic inversion - cross polarization) pulse sequence. These spectra provide (14)N electric field gradient (EFG) tensor parameters and orientations that are particularly sensitive to variations in local structure and intermolecular hydrogen-bonding interactions. The (1)H{(15)N} idHETCOR spectra, acquired under conditions of fast magic-angle spinning (MAS), used CP transfers to provide (1)H-(15)N chemical shift correlations for all nitrogen environments, except for two sites in acebutolol and nicardipine. One of these two sites (RR'NH2(+) in acebutolol) was successfully detected using the DNP-enhanced (15)N{(1)H} CP/MAS measurement, and one (RNO2 in nicardipine) remained elusive due to the absence of

  13. A holistic approach to understanding the N isotopic composition (d15N) of deep-sea sediments: diatom-bound, foraminifera-bound, whole sediment and modern nitrate d15N from the equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Rafter, P. A.; Charles, C. D.; Sigman, D. M.; Haug, G. H.

    2010-12-01

    The nitrogen (N) isotopic composition (d15N) of sediment is well established as a proxy of nitrate consumption and the d15N of nitrate in the surface ocean, but it is commonly assumed that post-depositional fractionation during organic matter degradation provides an additional unconstrained variable in sediments from the deep-sea. This mistrust of deep-sea sediments essentially renders most of the global ocean off-limits to the application of this powerful proxy of nutrient dynamics. Here we address this issue with new measurements of diatom-bound, foraminifera-bound, and whole sediment d15N from deep-sea sediments of the equatorial Pacific—a region where we have also investigated the processes influencing modern nitrate characteristics. With the results of these new records and previously published measurements relevant to the composition of sedimentary nitrogen, we are confident that whole sediment d15N from the deep-sea is not altered after deposition on the sea floor and that it accurately records surface ocean conditions. With these new constraints on whole sediment d15N, we discuss the exciting implications for alternative sediment d15N measurements (such as diatom- and foraminifera-bound d15N) and present evidence for a long-term increase in equatorial Pacific d15N of nitrate.

  14. 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.

  15. 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.

  16. Heavy labeling of recombinant proteins.

    PubMed

    Rodriguez, Eric

    2007-01-01

    Because of the cost of isotopic chemicals and heterologous proteins to produce, an economical 15N/13C isotopic labeling method is critically needed. Four protocols have been tested for the expression of Ovine interferon-tau in Pichia pastoris. 13C-glucose in place of 13C-glycerol as well as the need for 15N/13C-sources were evaluated during the growth phase. Sequential addition of 15NH4Cl and 13C-methanol were also evaluated at different ratio. Our results demonstrate that 15N/13C isotopes are not required throughout the initial growth period but are necessary at low concentration a few hours prior to the methanol induction period. We have evaluated the cost of the use of isotopes 15NH4Cl, 13C-glucose and 13C-methanol in our optimised P4 protocol conditions. The cost was one-third that of the standard method using 15NH4Cl and 13C-glucose throughout the entire growth period and was even lower using 13C-glycerol.

  17. Intestinal renal metabolism of L-citrulline and L-arginine following enteral or parenteral infusion of L-alanyl-L-[2,15N]glutamine or L-[2,15N]glutamine in mice.

    PubMed

    Boelens, Petra G; van Leeuwen, Paul A M; Dejong, Cornelis H C; Deutz, Nicolaas E P

    2005-10-01

    Previously, we observed increased plasma arginine (ARG) concentrations after glutamine (GLN)-enriched diets, in combination with clinical benefits. GLN delivers nitrogen for ARG synthesis, and the present study was designed to quantify the interorgan relationship of exogenous L-GLN or GLN dipeptide, by enteral or parenteral route, contributing to intestinal citrulline (CIT) and renal de novo ARG synthesis in mice. To study this, we used a multicatheterized mouse model with Swiss mice (n = 43) in the postabsorptive state. Stable isotopes were infused into the jugular vein or into the duodenum {per group either free L-[2,(15)N]GLN or dipeptide L-ALA-L-[2,(15)N]GLN, all with L-[ureido-(13)C-(2)H(2)]CIT and L-[guanidino-(15)N(2)-(2)H(2)]ARG} to establish renal and intestinal ARG and CIT metabolism. Blood flow was measured using (14)C-para-aminohippuric acid. Net intestinal CIT release, renal uptake of CIT, and net renal ARG efflux was found, as assessed by arteriovenous flux measurements. Quantitatively, more de novo L-[2,(15)N]CIT was produced when free L-[2,(15)N]GLN was given than when L-ALA-L-[2,(15)N]GLN was given, whereas renal de novo L-[2,(15)N]ARG was similar in all groups. In conclusion, the intestinal-renal axis is hereby proven in mice in that L-[2,(15)N]GLN or dipeptide were both converted into de novo renal L-[2,(15)N]ARG; however, not all was derived from intestinal L-[2,(15)N]CIT production. In this model, the feeding route and form of GLN did not influence de novo renal ARG production derived from GLN.

  18. A novel 15N tracer approach for the quantification of N2 and N2O emissions from soil incubations in a completely automated laboratory set up

    NASA Astrophysics Data System (ADS)

    Scheer, Clemens; Dannenmann, Michael; Meier, Rudolf

    2015-04-01

    The microbial mediated production of nitrous oxide (N2O) and its reduction to dinitrogen (N2) via denitrification represents a loss of nitrogen (N) from fertilised agro-ecosystems to the atmosphere. Although denitrification has received great interest by biogeochemists in the last decades, the magnitude of N2lossesand related N2:N2O ratios from soils still are largely unknown due to methodical constraints. We present a novel 15N tracer approach, based on a previous developed tracer method to study denitrification in pure bacterial cultures which was modified for the use on soil incubations in a completely automated laboratory set up. The method uses a background air in the incubation vessels that is replaced with a helium-oxygen gas mixture with a 50-fold reduced N2 background (2 % v/v). This method allows for a direct and sensitive quantification of the N2 and N2O emissions from the soil with isotope-ratio mass spectrometry after 15N labelling of denitrification N substrates and minimises the sensitivity to the intrusion of atmospheric N2 at the same time. The incubation set up was used to determine the influence of different soil moisture levels on N2 and N2O emissions from a sub-tropical pasture soil in Queensland/Australia. The soil was labelled with an equivalent of 50 μg-N per gram dry soil by broadcast application of KNO3solution (4 at.% 15N) and incubated for 3 days at 80% and 100% water filled pore space (WFPS), respectively. The headspace of the incubation vessel was sampled automatically over 12hrs each day and 3 samples (0, 6, and 12 hrs after incubation start) of headspace gas analysed for N2 and N2O with an isotope-ratio mass spectrometer (DELTA V Plus, Thermo Fisher Scientific, Bremen, Germany(. In addition, the soil was analysed for 15N NO3- and NH4+ using the 15N diffusion method, which enabled us to obtain a complete N balance. The method proved to be highly sensitive for N2 and N2O emissions detecting N2O emissions ranging from 20 to 627 μN kg

  19. Distribution of Bacteria at Different Poultry Litter Depths

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A common practice in the commercial broiler industry is to reuse litter over multiple broiler flocks. Morbidity, mortality, and condemnation have been attributed to pathogenic bacteria which reside in used litter. Information that describes how bacteria are distributed throughout the litter bed is...

  20. Long-term litter decomposition controlled by manganese redox cycling.

    PubMed

    Keiluweit, Marco; Nico, Peter; Harmon, Mark E; Mao, Jingdong; Pett-Ridge, Jennifer; Kleber, Markus

    2015-09-22

    Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of litter was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn(2+) provided by fresh plant litter to produce oxidative Mn(3+) species at sites of active decay, with Mn eventually accumulating as insoluble Mn(3+/4+) oxides. Formation of reactive Mn(3+) species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn(3+)-based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn(3+) species in the litter layer. This observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant-soil system may have a profound impact on litter decomposition rates.

  1. The Evaluation of Litter Behavior Modification in a River Environment.

    ERIC Educational Resources Information Center

    Wagstaff, Mark C.; Wilson, Beth E.

    1988-01-01

    Behavior modification techniques were evaluated by observing litter collection behavior of commercial rafting groups. The number of litter pieces retrieved by treatment and control groups was significantly different. Results support the idea that verbal appeal and role modeling can be effective litter control techniques. (Author/CW)

  2. Subsurface Banded Broiler Litter Improves Cotton Yield and Quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Broiler litter is typically land-applied as a fertilizer by surface broadcasting, a practice that results in volatilization loss of N as NH3. This loss may be drastically reduced or eliminated by the use of a newly developed precision litter implement designed to apply the litter in bands just belo...

  3. Long-term litter decomposition controlled by manganese redox cycling

    PubMed Central

    Keiluweit, Marco; Nico, Peter; Harmon, Mark E.; Mao, Jingdong; Pett-Ridge, Jennifer; Kleber, Markus

    2015-01-01

    Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of litter was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn2+ provided by fresh plant litter to produce oxidative Mn3+ species at sites of active decay, with Mn eventually accumulating as insoluble Mn3+/4+ oxides. Formation of reactive Mn3+ species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn3+-based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn3+ species in the litter layer. This observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant–soil system may have a profound impact on litter decomposition rates. PMID:26372954

  4. δ15N patterns of Douglas-fir and red alder riparian forests in the Oregon Coast Range

    USGS Publications Warehouse

    Scott, E.E.; Perakis, S.S.; Hibbs, D.E.

    2008-01-01

    We used naturally occurring stable isotopes of N to compare N dynamics in near-stream and upslope environments along riparian catenas in N-fixing red alder (Alnus rubra) and Douglas-fir (Pseudotsuga menziesii) forests in the Coast Range of western Oregon. Based on the existing literature, we expected soil δ15N to be enriched closer to streams owing to inputs of isotopically heavy, marine-derived N by spawning salmon, higher rates of denitrification near the stream, or both. However, it has been unclear what effect red alder might have on soil δ15N patterns near streams. We found a consistent −1‰ δ15N signature in red alder foliage, and δ15N of total N in soils under red alder averaged 2.2‰ along sampling transects extending 20 m upslope from the stream. Surprisingly, δ15N of total N in soil under Douglas-fir was progressively depleted nearer to streams, opposite from the pattern expected from N losses by denitrification or N inputs from anadromous salmon. Instead, δ15N of total N in soil under Douglas-fir converged toward soil δ15N values typical of red alder sites. We consider that the historic presence of red alder may have contributed a legacy of lower soil δ15N nearer to streams on sites that are currently dominated by young Douglas-fir forest.

  5. 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.

  6. The Effect of Litter Position on Ultraviolet Photodegradation of Standing Dead Litter

    NASA Astrophysics Data System (ADS)

    Lin, Y.; King, J. Y.

    2012-12-01

    In dryland ecosystems, models incorporating only biotic mechanisms usually underestimate the decay rate of plant litter. Photodegradation, an abiotic process through which solar radiation breaks down organic matter, has recently been proposed as an important pathway of litter decomposition in dryland ecosystems, accounting for as much as 25 to 60% of mass loss. However, it remains unclear what factors control the relative importance of photodegradation and biotic decomposition. It is hypothesized that this balance is affected by the location of litter within the litter layer (or thatch): in upper layers of thatch, photodegradation is significant because litter is exposed to sunlight; in lower layers where litter is strongly shaded, photodegradation is negligible compared to biotic decomposition. In August 2011, a field experiment was initiated at the University of California's Sedgwick Reserve, Santa Ynez, CA, in order to understand how ultraviolet (UV) radiation and litter position within the thatch affect litter decomposition. Two levels of UV radiation (280-400 nm) are achieved by screens: "UV-Pass" (transmitting > 81% of UV radiation) and "UV-Block" (transmitting < 8% of UV radiation). Litterbags were placed either at the top or at the bottom of the thatch. Results after 9 months of field exposure show that at the top of the thatch, litter mass loss was 13% higher in UV-Pass than in UV-Block, suggesting the occurrence of UV photodegradation. Surprisingly, litter mass loss was 52% higher in UV-Pass at the bottom of the thatch, even though very limited UV radiation penetrated through the thatch (at least 10 cm thick). The relative humidity in the thatch was higher in UV-Pass than in UV-Block treatments, especially at night; thus it is speculated that the UV manipulation not only alters the incoming radiation spectrum but also affects microclimate, consequently changing biotic decomposition. At the bottom of the thatch, lignin concentration of plant litter was 19

  7. Ecological restoration of litter in mined areas

    NASA Astrophysics Data System (ADS)

    Teresinha Gonçalves Bizuti, Denise; Nino Diniz, Najara; Schweizer, Daniella; de Marchi Soares, Thaís; Casagrande, José Carlos; Henrique Santin Brancalion, Pedro

    2016-04-01

    The success of ecological restoration projects depends on going monitoring of key ecological variables to determine if a desired trajectory has been established and, in the case of mining sites, nutrient cycling recovery plays an utmost importance. This study aimed to quantify and compare the annual litter production in native forests, and in restoration sites established in bauxite mines. We collected samples in 6 native forest remnants and 6 year-old restoration sites every month for a period of one year, in the city of Poços de Caldas/MG, SE Brazil. 120 wire collectors were used (0,6x0,6) and suspended 30cm above the soil surface. The material was dried until constant weight, weighed and fractionated in leaves, branches and reproductive material. The average annual litter production was 2,6 Mg ha-1 in native forests and 2,1 in forest in restoration sites, differing statistically. Litter production was higher in the rainy season, especially in September. Among the litter components, the largest contributor to total production was the fraction leaves, with 55,4% of the total dry weight of material collected, followed by reproductive material which contributed 24,5% and branches, with 20%. We conclude that the young areas in restoration process already restored important part, but still below the production observed in native areas.

  8. Utilization of poultry litter for pesticide bioremediation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural chemical products such as pesticides have been used to increase crop production, especially in undeveloped countries. Poultry litter, the combination of feces and bedding materials, has also been used as an alternative to improve soil quality for crop production. However, information re...

  9. Binding of oxytocin and 8-arginine-vasopressin to neurophysin studied by /sup 15/N NMR using magnetization transfer and indirect detection via protons

    SciTech Connect

    Live, D.H.; Cowburn, D.

    1987-10-06

    NMR was used to monitor the binding to neurophysin of oxytocin and 8-arginine-vasopressin, /sup 15/N labeling being used to identify specific backbone /sup 15/N and /sup 1/H signals. The most significant effects of binding were large downfield shifts in the amino nitrogen resonance of Phe-3 of vasopressin and in its associated proton, providing evidence that the peptide bond between residues 2 and 3 of the hormones is hydrogen-bonded to the protein within hormone-neurophysin complexes. Suggestive evidence for hydrogen bonding of the amino nitrogen of Tyr-2 was also obtained in the form of decreased proton exchange rates on binding; however, the chemical shift changes of this nitrogen and its associated proton indicated that such hydrogen bonding, if present, is probably weak. Shifts in the amino nitrogen of Asn-5 and in the -NH protons of both Asn-5 and Cys-6 demonstrated that these residues are significantly perturbed by binding, suggesting conformational changes of the ring on binding and/or the presence of binding sites on the hormone outside the 1-3 region. No support was obtained for the thesis that there is a significant second binding site for vasopressin on each neutrophysin chain. The behavior of both oxytocin and vasopressin on binding was consistent with formation of 1:1 complexes in slow exchange with the free state under most pH conditions. At low pH there was evidence of an increased exchange rate. Additionally, broadening of /sup 15/N resonances in the bound state at low pH occurred without a corresponding change in the resonances of equilibrating free hormone. The results suggest significant conformational alteration in neurophysin-hormone complexes at low pH possibly associated with protonation of the carboxyl group of the hormone-protein salt bridge.

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

    2012-01-01

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

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

    PubMed

    Templer, P H; Mack, M C; Chapin, F S; 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

    2012-08-01

    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 (< 1 week after 15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3-18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C:N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N x ha(-1) x yr(-1) above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer

  12. Macroalgae δ15N values in well-mixed estuaries: Indicator of anthropogenic nitrogen input or macroalgae metabolism?

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    Although nitrogen stable isotope ratio (δ15N) 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 δ15N variability. Simultaneous determinations of δ15N of dissolved inorganic nitrogen (DIN) along the land-sea continuum, inter-species variability of δ15N and its sensitivity to environmental factors are necessary to confirm the efficiency of macroalgae δ15N in monitoring nitrogen origin in mixed-use watersheds. In this study, δ15N of annual and perennial macroalgae (Ulva sp., Enteromorpha sp., Fucus vesiculosus and Fucus serratus) are compared to δ15N-DIN along the Charente Estuary, after characterizing δ15N 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 δ15N 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 δN- in this multiple source catchment, the overall mixture of NO sources - generally >95% DIN - leads to low variations of δN-NO at the mouth of the estuary (+7.7 to +8.4‰). Even if estuarine δN-NO values are not significantly different from pristine continental and oceanic site (+7.3‰ and +7.4‰), macroalgae δ15N 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 δN-NO are low, the same temporal trends in macroalgae δ15N values at estuarine and oceanic sites, and inter-species differences in δ15N values, suggest that macroalgae δ15N values might be modified by the metabolic response of macroalgae to environmental parameters (e

  13. Leaf litter dynamics and litter consumption in two temperate South Australian mangrove forests

    NASA Astrophysics Data System (ADS)

    Imgraben, Sarah; Dittmann, Sabine

    2008-02-01

    The dynamics and consumption of mangrove litter were investigated in two temperate Avicennia marina dominated forests in South Australia in order to compare production and fate of leaf litter with records from tropical and temperate mangroves. Litterfall was measured using traps over four months in the summer of 2004/2005. Average amount of litter was 2.1 and 3.2 g dwt m - 2 d - 1 , respectively, at the two study sites. Leaves accounted for most of the litterfall, followed by propagules and wood. Litterfall varied over time, and depending on the site and inundation time. The standing stock of leaf litter on the forest floor amounted to 15.5 g m - 2 dwt in March 2005. Decomposition determined by litter bags suggested that leaves lost ˜ 50% of their weight in the first two weeks of exposure, with little further weight loss over longer exposure times. Leaf consumption was investigated with a series of laboratory experiments, using the grapsid crab Helograpsus haswellianus, two snail species ( Salinator fragilis and Austrocochlea concamerata) and the polychaete Neanthes vaalii as potential consumers. There was no consumption of new leaves, and the only significant consumption of aged leaves was found for female H. haswellianus. H. haswellianus consumed 0.1 g dwt d - 1 of senescent leaves in the experiment, equivalent to 0.18 g m - 2 d - 1 in the field (average crab density 1.8 ind m - 2 ), or 9.4% of the average daily leaf litterfall. Experiments with propagules revealed no significant consumption by the crabs. High decomposition and low consumption rates of crabs account for the high accumulation and possible export of leaf litter from these mangroves. Leaf litter availability is not a limiting factor for invertebrate consumers in these temperate mangrove forests, and the low consumption rates imply a major difference in the fate of leaf litter between tropical and temperate mangrove systems.

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

    PubMed

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

    2011-06-24

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

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

    PubMed

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

    2011-06-24

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

  16. Hydroponic isotope labeling of entire plants and high-performance mass spectrometry for quantitative plant proteomics.

    PubMed

    Bindschedler, Laurence V; Mills, Davinia J S; Cramer, Rainer

    2012-01-01

    Hydroponic isotope labeling of entire plants (HILEP) combines hydroponic plant cultivation and metabolic labeling with stable isotopes using (15)N-containing inorganic salts to label whole and mature plants. Employing (15)N salts as the sole nitrogen source for HILEP leads to the production of healthy-looking plants which contain (15)N proteins labeled to nearly 100%. Therefore, HILEP is suitable for quantitative plant proteomic analysis, where plants are grown in either (14)N- or (15)N-hydroponic media and pooled when the biological samples are collected for relative proteome quantitation. The pooled (14)N-/(15)N-protein extracts can be fractionated in any suitable way and digested with a protease for shotgun proteomics, using typically reverse phase liquid chromatography nanoelectrospray ionization tandem mass spectrometry (RPLC-nESI-MS/MS). Best results were obtained with a hybrid ion trap/FT-MS mass spectrometer, combining high mass accuracy and sensitivity for the MS data acquisition with speed and high-throughput MS/MS data acquisition, increasing the number of proteins identified and quantified and improving protein quantitation. Peak processing and picking from raw MS data files, protein identification, and quantitation were performed in a highly automated way using integrated MS data analysis software with minimum manual intervention, thus easing the analytical workflow. In this methodology paper, we describe how to grow Arabidopsis plants hydroponically for isotope labeling using (15)N salts and how to quantitate the resulting proteomes using a convenient workflow that does not require extensive bioinformatics skills.

  17. Effects of four different restoration treatments on the natural abundance of (15)n stable isotopes in plants.

    PubMed

    Temperton, Vicky M; Märtin, Lea L A; Röder, Daniela; Lücke, Andreas; Kiehl, Kathrin

    2012-01-01

    δ(15)N signals in plant and soil material integrate over a number of biogeochemical processes related to nitrogen (N) and therefore provide information on net effects of multiple processes on N dynamics. In general little is known in many grassland restoration projects on soil-plant N dynamics in relation to the restoration treatments. In particular, δ(15)N signals may be a useful tool to assess whether abiotic restoration treatments have produced the desired result. In this study we used the range of abiotic and biotic conditions provided by a restoration experiment to assess to whether the restoration treatments and/or plant functional identity and legume neighborhood affected plant δ(15)N signals. The restoration treatments consisted of hay transfer and topsoil removal, thus representing increasing restoration effort, from no restoration measures, through biotic manipulation to major abiotic manipulation. We measured δ(15)N and %N in six different plant species (two non-legumes and four legumes) across the restoration treatments. We found that restoration treatments were clearly reflected in δ(15)N of the non-legume species, with very depleted δ(15)N associated with low soil N, and our results suggest this may be linked to uptake of ammonium (rather than nitrate). The two non-legume species differed considerably in their δ(15)N signals, which may be related to the two species forming different kinds of mycorrhizal symbioses. Plant δ(15)N signals could clearly separate legumes from non-legumes, but our results did not allow for an assessment of legume neighborhood effects on non-legume δ(15)N signals. We discuss our results in the light of what the δ(15)N signals may be telling us about plant-soil N dynamics and their potential value as an indicator for N dynamics in restoration.

  18. Effects of Four Different Restoration Treatments on the Natural Abundance of 15N Stable Isotopes in Plants

    PubMed Central

    Temperton, Vicky M.; Märtin, Lea L. A.; Röder, Daniela; Lücke, Andreas; Kiehl, Kathrin

    2012-01-01

    δ15N signals in plant and soil material integrate over a number of biogeochemical processes related to nitrogen (N) and therefore provide information on net effects of multiple processes on N dynamics. In general little is known in many grassland restoration projects on soil–plant N dynamics in relation to the restoration treatments. In particular, δ15N signals may be a useful tool to assess whether abiotic restoration treatments have produced the desired result. In this study we used the range of abiotic and biotic conditions provided by a restoration experiment to assess to whether the restoration treatments and/or plant functional identity and legume neighborhood affected plant δ15N signals. The restoration treatments consisted of hay transfer and topsoil removal, thus representing increasing restoration effort, from no restoration measures, through biotic manipulation to major abiotic manipulation. We measured δ15N and %N in six different plant species (two non-legumes and four legumes) across the restoration treatments. We found that restoration treatments were clearly reflected in δ15N of the non-legume species, with very depleted δ15N associated with low soil N, and our results suggest this may be linked to uptake of ammonium (rather than nitrate). The two non-legume species differed considerably in their δ15N signals, which may be related to the two species forming different kinds of mycorrhizal symbioses. Plant δ15N signals could clearly separate legumes from non-legumes, but our results did not allow for an assessment of legume neighborhood effects on non-legume δ15N signals. We discuss our results in the light of what the δ15N signals may be telling us about plant–soil N dynamics and their potential value as an indicator for N dynamics in restoration. PMID:22645597

  19. Effects of Acid on Plant Litter Decomposition in an Arctic Lake

    PubMed Central

    McKinley, Vicky L.; Vestal, J. Robie

    1982-01-01

    The effects of acid on the microbial decomposition of the dominant aquatic macrophyte (Carex sp.) in Toolik Lake, Alaska were studied in microcosms during the ice-free season of 1980. Toolik Lake is slightly buffered, deep, and very oligotrophic. Microbial activities, as determined by 14C-acetate incorporation into extractable lipids, associated with Carex litter were significantly (P < 0.01) reduced within 2 days at pHs of 3.0 and 4.0, but not 5.0, 5.5, or 6.0, as compared with ambient controls (pH 7.4). ATP levels were significantly reduced at pH 3.0, but not at the other pHs tested. After 18 days, microbial activity significantly correlated with weight loss (P < 0.05), nitrogen content (P < 0.01), and C/N ratios (P < 0.01) of the litter, but did not correlate with ATP levels. Scanning electron microscopy of the litter surface revealed that the fungi present at ambient pH did not become dominant at pHs below 5.5, diatoms were absent below pH 4.0, and bacterial numbers and extracellular slime were greatly reduced at pH 4.0 and below. Mineralization of Carex14C-lignin-labeled or 14C-cellulose-labeled lignocellulose was reduced at pH 2.0, but not at pH 4.0, 5.0, or 6.0, compared with controls (pH 7). We concluded that if the pH of the water from this slightly buffered lake was sufficiently reduced, rates of litter decomposition would be significantly reduced. Images PMID:16346015

  20. Utilizing the charge field effect on amide (15)N chemical shifts for protein structure validation.

    PubMed

    Bader, Reto

    2009-01-01

    Of all the nuclei in proteins, the nuclear magnetic resonance (NMR) chemical shifts of nitrogen are the theoretically least well understood. In this study, quantum chemical methods are used in combination with polarizable-continuum models in order to show that consideration of the effective electric field, including charge screening due to solvation, improves considerably the consistencies of statistical relationships between experimental and computed amide (15)N shifts between various sets of charged and uncharged oligopeptides and small organic molecules. A single conversion scheme between shielding parameters from first principles using density functional theory (DFT) and experimental shifts is derived that holds for all classes of compounds examined here. This relationship is then used to test the accuracy of such (15)N chemical shift predictions in the cyclic decapeptide antibiotic gramicidin S (GS). GS has previously been studied in great detail, both by NMR and X-ray crystallography. It adopts a well-defined backbone conformation, and hence, only a few discrete side chain conformational states need to be considered. Moreover, a charge-relay effect of the two cationic ornithine side chains to the protein backbone has been described earlier by NMR spectroscopy. Here, DFT-derived backbone amide nitrogen chemical shifts were calculated for multiple conformations of GS. Overall, the structural dynamics of GS is revisited in view of chemical shift behavior along with energetic considerations. Together, the study demonstrates proof of concept that (15)N chemical shift information is particularly useful in the analysis and validation of protein conformational states in a charged environment.

  1. Structure and Membrane Interactions of the Antibiotic Peptide Dermadistinctin K by Multidimensional Solution and Oriented 15N and 31P Solid-State NMR Spectroscopy

    PubMed Central

    Verly, Rodrigo M.; Moraes, Cléria Mendonça de; Resende, Jarbas M.; Aisenbrey, Christopher; Bemquerer, Marcelo Porto; Piló-Veloso, Dorila; Valente, Ana Paula; Almeida, Fábio C.L.; Bechinger, Burkhard

    2009-01-01

    DD K, a peptide first isolated from the skin secretion of the Phyllomedusa distincta frog, has been prepared by solid-phase chemical peptide synthesis and its conformation was studied in trifluoroethanol/water as well as in the presence of sodium dodecyl sulfate and dodecylphosphocholine micelles or small unilamellar vesicles. Multidimensional solution NMR spectroscopy indicates an α-helical conformation in membrane environments starting at residue 7 and extending to the C-terminal carboxyamide. Furthermore, DD K has been labeled with 15N at a single alanine position that is located within the helical core region of the sequence. When reconstituted into oriented phosphatidylcholine membranes the resulting 15N solid-state NMR spectrum shows a well-defined helix alignment parallel to the membrane surface in excellent agreement with the amphipathic character of DD K. Proton-decoupled 31P solid-state NMR spectroscopy indicates that the peptide creates a high level of disorder at the level of the phospholipid headgroup suggesting that DD K partitions into the bilayer where it severely disrupts membrane packing. PMID:19289046

  2. 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.

  3. 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.

  4. 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.

  5. NMR studies of isotopically labeled RNA

    SciTech Connect

    Pardi, A.

    1994-12-01

    In summary, the ability to generate NMR quantities of {sup 15}N and {sup 13}C-labeled RNAs has led to the development of heteronuclear multi-dimensional NMR techniques for simplifying the resonance assignment and structure determination of RNAs. These methods for synthesizing isotopically labeled RNAs are only several years old, and thus there are still relatively few applications of heteronuclear multi-dimensional NMR techniques to RNA. However, given the critical role that RNAs play in cellular function, one can expect to see an increasing number of NMR structural studies of biologically active RNAs.

  6. Changes in litter near an aluminum reduction plant

    USGS Publications Warehouse

    Beyer, W.N.; Fleming, W.J.; Swineford, D.

    1987-01-01

    Litter was collected from eight sites at distances as far as 33 km from an AI reduction plant in western Tennessee. As a result of an accumulation of fine litter (< 4.75 mm) the weight of the litter per unit area was abnormally high at the two sites within 2 km of the plant. Compared to litter collected far from the plant, it had a lower fiber content, was more sapric, and was less acid. Fluoride emissions from the plant were suggested as the probable cause of litter changes. Concentrations of water-extractable and acid-extractable F- in the litter, the 0- to 5-cm soil layer, and the 5- to 15-cm soil layer were strongly correlated with distance from the plant. Total acid-extractable F- in the litter and upper 15 cm of soil was about 41 times as much at the closest site (700 mg/kg) as at the most distant sites (12 and 16 mg/kg). In a bioassay of litter from our study sites, woodlice (Porcellio scaber Latr.) had an abnormally high mortality in litter that contained 440 mg/kg or more of acid-extractable F-. However, when F- was added as NaF to litter, a significant increase in mortality was observed only in treatments exceeding 800 mg/kg. The decrease in the rate of decomposition of the litter might eventually induce a deficiency of soil macronutrients, but none was detected.

  7. Degradation of leaf litter phenolics by aquatic and terrestrial isopods.

    PubMed

    Zimmer, Martin; Oliveira, Ricardo; Rodrigues, Elsa; Graça, Manuel A S

    2005-08-01

    To investigate species-specific decomposition rates of litter from native (Quercus faginea) and introduced (Eucalyptus globulus) tree species in Portugal, we monitored changes in the phenolic signature of leaf litter during decomposition as mediated by an aquatic, Proasellus coxalis (Isopoda: Asellota), and two terrestrial, Porcellio dispar and Eluma caelatum (Isopoda: Oniscidea), detritivores. Although the litter of Eucalyptus and Quercus did not differ in overall protein precipitation capacity, we detected differences in terms of contents of particular phenolic compounds and phenol oxidation products. Accordingly, we observed food-specific consumption rates in Proasellus, but not in the terrestrial isopods. Proasellus digested Eucalyptus at significantly higher rates than Quercus, whereas the opposite was the case for Eluma, and Porcellio digested both litter types equally well. Despite slight differences in detail, effects of Proasellus on changes in the signature of litter phenolics were similar for both litter types, whereas terrestrial isopods--Porcellio and Eluma, although they differed from each other--digestively degraded phenolic compounds in Eucalyptus and Quercus litter, respectively, in different ways. Overall, however, degradation of litter phenolics was similarly effective on both litter types. From these data, we conclude that decomposition of Eucalyptus litter does not proceed more slowly than of litter from native Portuguese trees.

  8. Future increase in temperature more than decrease in litter quality can affect microbial litter decomposition in streams.

    PubMed

    Ferreira, Verónica; Chauvet, Eric

    2011-09-01

    The predicted increase in atmospheric CO(2) concentration for this century is expected to lead to increases in temperature and changes in litter quality that can affect small woodland streams, where water temperature is usually low and allochthonous organic matter constitutes the basis of the food web. We have assessed the individual and interactive effect of water temperature (5 and 10°C) and alder litter quality produced under ambient CO(2) levels (ambient litter) or under CO(2) concentrations predicted for 2050 (elevated litter) on litter decomposition and on fungal activity and assemblage structure. Litter decomposition rates and fungal respiration rates were significantly faster at 10 than at 5°C, but they were not affected by litter quality. Litter quality affected mycelial biomass accrual at 5 but not at 10°C, while increases in temperature stimulated biomass accrual on ambient but not on elevated litter. A similar pattern was observed for conidial production. All variables were stimulated on elevated litter at 10°C (future scenario) compared with ambient litter at 5°C (present scenario), but interactions between temperature and litter quality were additive. Temperature was the factor that most strongly affected the structure of aquatic hyphomycete assemblages. Our results indicate that if future increases in atmospheric CO(2) lead to only slight modifications in litter quality, the litter decomposition and fungal activities and community structure will be strongly controlled by increased water temperature. This may have serious consequences for aquatic systems as faster litter decomposition may lead to food depletion for higher trophic levels. PMID:21461934

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

    SciTech Connect

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

    1988-08-03

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

  10. Positive reinforcement of litter removal in the natural environment12

    PubMed Central

    Powers, Richard B.; Osborne, J. Grayson; Anderson, Emmett G.

    1973-01-01

    Litter is an especially large and costly problem in unsupervised high-use recreational areas. This study investigated procedures to induce visitors to remove litter from an unsupervised U.S. Forest Service area in which signs attached to two litter stations instructed people to pick up and deposit litter. A small sum of money or chances on a larger sum given for participation usually resulted in more bags of litter being picked up per week. Although only a small proportion of the area's users participated in the project, ground surveys indicated the areas sampled were somewhat freer of litter during the payment condition. The results suggest that small monetary rewards may be a promising approach to litter control in unsupervised as well as supervised areas. ImagesFig. 2 PMID:16795442

  11. Positive reinforcement of litter removal in the natural environment.

    PubMed

    Powers, R B; Osborne, J G; Anderson, E G

    1973-01-01

    Litter is an especially large and costly problem in unsupervised high-use recreational areas. This study investigated procedures to induce visitors to remove litter from an unsupervised U.S. Forest Service area in which signs attached to two litter stations instructed people to pick up and deposit litter. A small sum of money or chances on a larger sum given for participation usually resulted in more bags of litter being picked up per week. Although only a small proportion of the area's users participated in the project, ground surveys indicated the areas sampled were somewhat freer of litter during the payment condition. The results suggest that small monetary rewards may be a promising approach to litter control in unsupervised as well as supervised areas.

  12. Temporal dynamics of biotic and abiotic drivers of litter decomposition.

    PubMed

    García-Palacios, Pablo; Shaw, E Ashley; Wall, Diana H; Hättenschwiler, Stephan

    2016-05-01

    Climate, litter quality and decomposers drive litter decomposition. However, little is known about whether their relative contribution changes at different decomposition stages. To fill this gap, we evaluated the relative importance of leaf litter polyphenols, decomposer communities and soil moisture for litter C and N loss at different stages throughout the decomposition process. Although both microbial and nematode communities regulated litter C and N loss in the early decomposition stages, soil moisture and legacy effects of initial differences in litter quality played a major role in the late stages of the process. Our results provide strong evidence for substantial shifts in how biotic and abiotic factors control litter C and N dynamics during decomposition. Taking into account such temporal dynamics will increase the predictive power of decomposition models that are currently limited by a single-pool approach applying control variables uniformly to the entire decay process.

  13. 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

  14. Oxygen determination in materials by 18O(p,αγ)15N nuclear reaction

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjiv; Sunitha, Y.; Reddy, G. L. N.; Sukumar, A. A.; Ramana, J. V.; Sarkar, A.; Verma, Rakesh

    2016-07-01

    The paper presents a proton induced γ-ray emission method based on 18O(p,αγ)15N nuclear reaction to determine bulk oxygen in materials. The determination involves the measurement of 5.27 MeV γ-rays emitted following the de-excitation of 15N nuclei. A description of the energetics of the reaction is given to provide an insight into the origin of 5.27 MeV γ-rays. In addition, thick target γ-ray yields and the limits of detection are measured to ascertain the analytical potential of the reaction. The thick-target γ-ray yields are measured with a high purity germanium detector and a bismuth germanate detector at 0° as well as 90° angles in 3.0-4.2 MeV proton energy region. The best limit of detection of about 1.3 at.% is achieved at 4.2 MeV proton energy for measurements at 0° as well 90° angles with the bismuth germanate detector while the uncertainty in quantitative analysis is <8%. The reaction has a probing depth of several tens of microns. Interferences can arise from fluorine due to the occurrence of 19F(p,αγ)16O reaction that emits 6-7 MeV γ-rays. The analytical potential of the methodology is demonstrated by determining oxygen in several oxide as well as non-oxide materials.

  15. The coral δ15N 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 (δ15Ncoral) from the mouth of the Todoroki River, Ishigaki Island, Japan, to examine whether the δ15Ncoral 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 δ15Ncoral for 14 years (CORE1; 1993-2007) and the annual variation of δ15Ncoral for 52 years (CORE2; 1958-2010). In CORE1, the 5-month running mean of δ15Ncoral was positively correlated with that of monthly precipitation, excluding all strong precipitation events (>150 mm d-1). In CORE2, the δ15Ncoral mean in the earlier period (1958-1980) was 1.0 ‰ greater than that in the later period (1981-2010). The annual averages of δ15Ncoral are positively correlated with the total precipitation in the rainy season (May-June) for both time periods. The difference in the δ15Ncoral 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 δ15N coral proxy records, this study emphasises the clear potential for their use in reconstructing terrestrial nitrate discharge records from corals.

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

    PubMed

    Farrugia, Kristina N; Makuc, Damjan; Podborska, Agnieszka; Szaciłowski, 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

  17. Attenuation of Nitrate-15N by Vegetated Buffers in an Irrigated Pasture System

    NASA Astrophysics Data System (ADS)

    Haughn, A. B.; Tate, K.; Kessel, C. V.

    2003-12-01

    Irrigated pastures are found within watersheds providing much of Western North America's surface drinking water supply. Vegetative buffers are often proposed to attenuate nutrient pollutants in runoff, but there is limited information on the mechanistic functioning of buffers adjacent to irrigated pastures. This study is intended to fill this gap in knowledge by examining specific vegetation, soil, and landscape characteristics controlling buffer efficiency and capacity. At the University of California Sierra Foothill Research and Extension Center, established flood-irrigated plots with three different buffer treatments are being used to characterize the attenuation of N, P, and sediment by buffers. Stable 15N isotope tracer was applied to quantify the fate of nitrate moving through the pasture and buffers. In the first 10 days following application of the 15N tracer, 2% of the tracer was lost as runoff, with more than half of the total loss occurring from plots with no buffers. Of the remaining tracer, 47% was taken up by grass in the zone of application, 3% was taken up by vegetation within the buffers (primarily in the first 4m of buffer), 20% was stored in the A horizon of the soil, and 28% was lost via leaching and/or gaseous losses. Results presented will include the effect of buffer length on nutrient attenuation and the relative importance of different N pools for nitrate retention. This research will allow land managers to maximize efficiency of riparian buffers adjacent to irrigated pasture, potentially increasing the adoption of vegetated buffers as a management tool.

  18. Contribution of 19F resonances on 18O( p, α)15N reaction rate

    NASA Astrophysics Data System (ADS)

    Benmeslem, Meriem; Chafa, Azzedine; Barhoumi, Slimane; Tribeche, Mouloud

    2014-08-01

    The 18O( p, α)15N reaction influences the isotopes production such as 19F, 18O, and 15N which can be used to test the models of stellar evolution. 19F is synthesized in both asymptotic giant branch (AGB) and metal-rich Wolf-Rayet (WR) stars. Using R-matrix theory we allow new values of resonances parameters in 19F. We show that the most important contribution to the differential and total cross section at low energies, comes from the levels in 19F situated at resonances energies E R =151, 680 and 840 keV with spin and parity 1/2+. The total width of the 680 keV resonance is badly known. So, we have focused on this broad resonance corresponding to the 8.65 MeV level in 19F. We delimit the temperature range in which each resonance contribution to the total reaction rate occurs by analyzing the ratio ( N A < σν> i / N A < σν>). This allowed us to show that the 680 and 840 keV broad resonances strongly dominate the reaction rate over the stellar temperature range T 9=0.02-0.06 and T 9=0.5-5. Finally, these results were compared to NACRE and Iliadis astrophysical compilations.

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

    PubMed

    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 (15)N dimension of the 3D experiment to obtain the NH RDCs. We have used this idea to carry out J-scaling in a 2D (15)N-(1)H-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. PMID:20018538

  20. 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.

  1. 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.

  2. Precursor discrimination of designer drug benzylpiperazine using δ13C and δ15N 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 (BZP·HCl). A preliminary analysis of δ13C and δ15N isotopic ratios in BZP·HCl products and corresponding synthetic intermediates (piperazine·HCl) synthesized in-house from three different precursor suppliers was conducted using IRMS. Analysis of the δ13C and δ15N isotopic data indicated that discrimination and correct grouping of all the intermediates and some of the product samples examined in this study were achievable.

  3. Isotopic analysis of bulk, LMW, and HMW DON d15N indicates recycled nitrogen release from marine DON

    NASA Astrophysics Data System (ADS)

    Knapp, A. N.; Sigman, D. M.; Lipschultz, F.; Kustka, A.; Capone, D. G.

    2010-12-01

    Nitrogen (N) concentration and stable isotope ratio (d15N) measurements were made on bulk and size fractionated surface ocean dissolved organic nitrogen (DON) samples collected in the oligotrophic North Atlantic and Pacific Oceans. The bulk DON concentration in the upper 100 m is similar between the North Atlantic and North Pacific, between 4.5 and 5.0 uM, but the average d15N of bulk DON is significantly different, 3.9 per mil vs. air in the North Atlantic and 4.7 per mil in the North Pacific. The d15N of both bulk and HMW DON from the western tropical North Atlantic are similar to previous measurements, ~4.0 to 4.5 per mil. We report the first measurements of LMW DON d15N, which is consistently lower than HMW DON d15N. Neither the concentration nor d15N of bulk or size-fractionated DON varied with in situ N2 fixation rate, although significant variation in bulk and LMW DON d15N was observed between January and July of the same year in the western tropical North Atlantic. We propose a conceptual model to explain 1) the elevated d15N of bulk DON relative to other surface ocean N pools and fluxes, 2) the elevation of HMW DON d15N relative to LMW DON d15N, and 3) the inter-basin difference in the d15N of bulk DON. In this model, DON is produced from suspended particulate organic nitrogen (PON) without isotope fractionation because the conversion from PON to DON largely does not involve N-bearing bonds. In contrast, deamination and amide hydrolysis, with N isotope effects of 3 to 10 per mil, are major mechanisms by which DON is converted to ammonia and/or to other simple N compounds (e.g., amino acids). Thus these N-specific DON loss reactions result in an elevated d15N of residual DON relative to the parent DON and therefore also to the PON source. Moreover, the ammonium and simple organic N compounds released by microbial DON degradation are efficiently reassimilated back into the PON pool, as an integral part of the regenerated N cycle that further lowers the d15N

  4. Cereal grain, rachis and pulse seed amino acid δ15N values as indicators of plant nitrogen metabolism.

    PubMed

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

    2014-01-01

    Natural abundance δ(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 δ(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 Lauchstädt, Germany, were determined by GC-C-IRMS. It was found that the δ(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 δ(15)N value which is an average of the other AAs due to its central role in AA-N cycling. The relative AA δ(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 δ(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.

  5. The effect of saprophagous macrofauna on litter decomposition

    NASA Astrophysics Data System (ADS)

    Frouz, Jan

    2016-04-01

    Previous experiments show that feeding of the larvae of Bibionidae on lef litter cause short term increase of respiration but in long term the decomposition of bibio feces is slower than decomposition of litter from which feces were produced. To understand why excrements of decompose more slowly than leaf litter, we fed Bibio marci larvae the litter of tree species differing in litter quality (Alnus glutinosa, Salix caprea, and Quercus robur) and then measured respiration induced by litter and excrements. We also measured respiration induced by the same litter artificially modified to mimic faunal effects; the litter was modified by grinding, grinding with alkalinization to pH 11, grinding with coating by kaolinite, and grinding with both alkalinization and coating. Decomposition of excrements tended to be slower for willow and was significantly slower for oak and alder than for the corresponding litter. With oak, decomposition was slower for all artificially modified litter than for non-modified litter. The reduction in the decomposition was similar for excrements and for alder and willow litter that was ground, coated, and alkalinized. In alder, a similar reduction was found in ground and alkalinized litter. 13C NMR indicated that gut passage increases aliphatic components and decreases polysaccharides. Pyrolysis indicated that gut passage increases the ratio of guaiacyl to hydroxymethyl derivatives in lignin. Our findings indicate that the decreased decomposition rate of excrements might result from the removal of easily available polysaccharides, the increase in aliphatic components, an increase in the resistant components of lignin, the accumulation of microbial cell walls, and the binding of nitrogen into complexes with aromatic components. Several of these mechanisms are supported or determined by litter alkalinization during gut passage.

  6. Plant community change mediates the response of foliar δ(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 δ(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 δ(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 δ(15)N only for prairie plants on a silty clay. δ(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 δ(15)N on the silty clay by reducing fractionation during N uptake and assimilation. However, we interpret the soil-specific, δ(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 δ(15)N than the dominant grass (Bothriochloa ischaemum) in pasture. CO2 enrichment changed grassland δ(15)N by shifting species relative abundances. PMID:25604918

  7. Plant community change mediates the response of foliar δ(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 δ(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 δ(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 δ(15)N only for prairie plants on a silty clay. δ(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 δ(15)N on the silty clay by reducing fractionation during N uptake and assimilation. However, we interpret the soil-specific, δ(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 δ(15)N than the dominant grass (Bothriochloa ischaemum) in pasture. CO2 enrichment changed grassland δ(15)N by shifting species relative abundances.

  8. Glacial-interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-?15N measurements

    NASA Astrophysics Data System (ADS)

    Capron, E.; Landais, A.; Buiron, D.; Cauquoin, A.; Chappellaz, J. A.; Debret, M.; Jouzel, J.; Leuenberger, M.; Martinerie, P.; Masson-Delmotte, V.; Mulvaney, R.; Parrenin, F.; Prié, F.

    2013-12-01

    Correct estimation of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice core studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: outputs of a firn densification model, and measurements of δ15N of N2 in air trapped in ice core, assuming that δ15N is only affected by gravitational fractionation in the firn column. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available ice core air- δ15N measurements from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rates and temperature conditions. Our δ15N profiles reveal a heterogeneous response of the firn structure to glacial-interglacial climatic changes. While firn densification simulations correctly predict TALDICE δ15N variations, they systematically fail to capture the large millennial-scale δ15N variations measured at BI and the δ15N glacial levels measured at JRI and EDML - a mismatch previously reported for central East Antarctic ice cores. New constraints of the EDML gas-ice depth offset during the Laschamp event (41 ka) and the last deglaciation do not favour the hypothesis of a large convective zone within the firn as the explanation of the glacial firn model- δ15N data mismatch for this site. While we could not conduct an in-depth study of the influence of impurities in snow for firnification from the existing datasets, our detailed comparison between the δ15N profiles and firn model simulations under different temperature and accumulation rate scenarios suggests that the role of accumulation rate may have been underestimated in the current description of firnification models.

  9. Glacial-interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-δ15N measurements

    NASA Astrophysics Data System (ADS)

    Capron, E.; Landais, A.; Buiron, D.; Cauquoin, A.; Chappellaz, J.; Debret, M.; Jouzel, J.; Leuenberger, M.; Martinerie, P.; Masson-Delmotte, V.; Mulvaney, R.; Parrenin, F.; Prié, F.

    2013-05-01

    Correct estimation of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice core studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: outputs of a firn densification model, and measurements of δ15N of N2 in air trapped in ice core, assuming that δ15N is only affected by gravitational fractionation in the firn column. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available ice core air-δ15N measurements from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rates and temperature conditions. Our δ15N profiles reveal a heterogeneous response of the firn structure to glacial-interglacial climatic changes. While firn densification simulations correctly predict TALDICE δ15N variations, they systematically fail to capture the large millennial-scale δ15N variations measured at BI and the δ15N glacial levels measured at JRI and EDML - a mismatch previously reported for central East Antarctic ice cores. New constraints of the EDML gas-ice depth offset during the Laschamp event (~41 ka) and the last deglaciation do not favour the hypothesis of a large convective zone within the firn as the explanation of the glacial firn model-δ15N data mismatch for this site. While we could not conduct an in-depth study of the influence of impurities in snow for firnification from the existing datasets, our detailed comparison between the δ15N profiles and firn model simulations under different temperature and accumulation rate scenarios suggests that the role of accumulation rate may have been underestimated in the current description of firnification models.

  10. Environmental fate of roxarsone in poultry litter. Part II. Mobility of arsenic in soils amended with poultry litter

    USGS Publications Warehouse

    Rutherford, D.W.; Bednar, A.J.; Garbarino, J.R.; Needham, R.; Staver, K.W.; Wershaw, R. L.

    2003-01-01

    Poultry litter often contains arsenic as a result of organo-arsenical feed additives. When the poultry litter is applied to agricultural fields, the arsenic is released to the environment and may result in increased arsenic in surface and groundwater and increased uptake by plants. The release of arsenic from poultry litter, litter-amended soils, and soils without litter amendment was examined by extraction with water and strong acids (HCI and HN03). The extracts were analyzed for As, C, P, Cu, Zn, and Fe. Copper, zinc, and iron are also poultry feed additives. Soils with a known history of litter application and controlled application rate of arsenic-containing poultry litter were obtained from the University of Maryland Agricultural Experiment Station. Soils from fields with long-term application of poultry litter were obtained from a tilled field on the Delmarva Peninsula (MD) and an untilled Oklahoma pasture. Samples from an adjacent forest or nearby pasture that had no history of litter application were used as controls. Depth profiles were sampled for the Oklahoma pasture soils. Analysis of the poultry litter showed that 75% of the arsenic was readily soluble in water. Extraction of soils shows that weakly bound arsenic mobilized by water correlates positively with C, P, Cu, and Zn in amended fields and appears to come primarily from the litter. Strongly bound arsenic correlates positively with Fe in amended fields and suggests sorption or coprecipitation of As and Fe in the soil column.

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

    NASA Astrophysics Data System (ADS)

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

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

  12. Effects of petroleum hydrocarbons on plant litter microbiota in an artic lake

    SciTech Connect

    McKinley, V.L.; Federle, T.W.; Vestal, J.R.

    1982-01-01

    The effects of petroleum hydrocarbons on the microbial community associated with decomposing Carex leaf litter colonized in Toolik Lake, Alaska, were examined. Microbial metabolic activity, measured as the rate of acetate incorporation into lipid, did not vary significantly from controls over a 12-h period after exposure of colonized Carex litter to 3.0 ml of Prudhoe Bay crude oil, diesel fuel, or toluene per liter. ATP levels of the mirobiota became elevated within 2 h after the exposure of the litter to diesel fuel or toluene, but returned to control levels within 4 to 8 h. ATP levels of samples exposed to Prudhoe Baye crude oil did not vary from control levels. Mineralization of specificially labeled /sup 14/C-(lignin)-lignocellulose and /sup 14/C-(cellulose)-lignocellulose by Toolike Lake sediments, after the addition of 2% (vol/vol) Prudhoe Bay crude oil, motor oil, diesel fuel, gasoline, n-hexane, or toluene, was examined after 21 days of incubation at 10/sup 0/C. Diesel fuel, motor oil, gasoline and toluene inhibited /sup 14/C-(lignin)-lignocellulose mineralization by 58, 67, 67, and 86%, respectively. Hexane-treated samples displayed an increase in the rate of /sup 14/C-(lignin)-lignocellulose mineralization of 33%. /sup 14/C-(cellulose)-lignocellulose mineralization was inhibited by the addition of motor oil or toluene by 27 and 64%, respectively, whereas diesel fuel-treaated samples showed a 17% increase in mineralization rate. Mineralization of the labeled lignin component of lignocellulose appeared to be more sensitive to hydrocarbon perturbations than was the labeled cellulose component.

  13. How does litter cover, litter diversity and fauna affect sediment discharge and runoff?

    NASA Astrophysics Data System (ADS)

    Goebes, Philipp; Seitz, Steffen; Kühn, Peter; Scholten, Thomas

    2013-04-01

    Litter cover plays a major role in soil erosion processes. It is known that litter cover reduces erosivity of raindrops, decreases sediment discharge and lowers runoff volume compared to bare ground. However, in the context of biodiversity, the composition of litter cover, its effect on sediment discharge and runoff volume and their influence on soil erosion have not yet been analyzed in detail. Focusing on initial soil erosion (splash), our experimental design is designated to get a better understanding of these mechanisms. The experiments were carried out within the DFG research unit "Biodiversity and Ecosystem Functioning (BEF)-China" in subtropical China. The "New Integrated Litter Experiment (NILEx)" used as platform combining different subprojects of BEF-China dealing with "decomposition and nutrient cycling", "mechanisms of soil erosion" and "functional effects of herbivores, predators and saproxylics" in one experiment. In NILEx, 96 40cm x 40cm runoff plots on two hill slopes inside a castanea molissima forest plantation have been installed and filled with seven different types of litter cover. 16 one-species plots, 24 two-species plots, 4 four-species plots and 4 bare ground plots have been set up, each replicated once. We prepared 48 Plots with traps (Renner solution) for soil macrofauna (diplopods and collembola), so half of the plots were kept free from fauna while the other half was accessible for fauna. Rainfall was generated artificially by using a rainfall simulator with a continuous and stable intensity of 60 mm/h. Our experiments included two runs of 20 minutes duration each, both conducted at two different time steps (summer 2012 and autumn 2012). Runoff volume and sediment discharge were measured every 5 minutes during one rainfall run. Litter coverage and litter mass were recorded at the beginning (summer 2012) and at the end of the experiment (autumn 2012). Our results show that sediment discharge as well as runoff volume decreases

  14. Arsenic speciation and reactivity in poultry litter

    USGS Publications Warehouse

    Arai, Y.; Lanzirotti, A.; Sutton, S.; Davis, J.A.; Sparks, D.L.

    2003-01-01

    Recent U.S. government action to lower the maximum concentration levels (MCL) of total arsenic (As) (10 ppb) in drinking water has raised serious concerns about the agricultural use of As-containing biosolids such as poultry litter (PL). In this study, solid-state chemical speciation, desorbability, and total levels of As in PL and long-term amended soils were investigated using novel synchrotronbased probing techniques (microfocused (??) synchrotron X-ray fluorescence (SXRF) and ??-X-ray absorption near-edge structure (XANES) spectroscopies) coupled with chemical digestion and batch experiments. The total As levels in the PL were as high as ???50 mg kg-1, and As(II/III and V) was always concentrated in abundant needle-shaped microscopic particles (???20/ ??m x 850 ??m) associated with Ca, Cu, and Fe and to a lesser extent with S, CI, and Zn. Postedge XANES features of litter particles are dissimilar to those of the organo-As(V) compound in poultry feed (i.e., roxarsone), suggesting possible degradation/transformation of roxarsone in the litter and/or in poultry digestive tracts. The extent of As desorption from the litter increased with increasing time and pH from 4.5 to 7, but at most 15% of the total As was released after 5 d at pH 7, indicating the presence of insoluble phases and/or strongly retained soluble compounds. No significant As accumulation (< 15 mg kg-1) was found in long-term PL-a mended agricultural surface soils. This suggests that As in the PL may have undergone surface and subsurface transport processes. Our research results raise concerns about long-term PL amendment effects on As contamination in surrounding soilwater environments.

  15. Paleoenvironmental implications of taxonomic variation among δ15N values of chloropigments

    USGS Publications Warehouse

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

    2011-01-01

    Natural variations in the ratios of nitrogen isotopes in biomass reflect variations in nutrient sources utilized for growth. In order to use δ15N values of chloropigments of photosynthetic organisms to determine the corresponding δ15N values of biomass – and by extension, surface waters – the isotopic offset between chlorophyll and biomass must be constrained. Here we examine this offset in various geologically-relevant taxa, grown using nutrient sources that may approximate ocean conditions at different times in Earth’s history. Phytoplankton in this study include cyanobacteria (diazotrophic and non-diazotrophic), eukaryotic algae (red and green), and anoxygenic photosynthetic bacteria (Proteobacteria), as well as environmental samples from sulfidic lake water. Cultures were grown using N2, NO3−, and NH4+ as nitrogen sources, and were examined under different light regimes and growth conditions. We find surprisingly high variability in the isotopic difference (δ15Nbiomass − δ15Nchloropigment) for prokaryotes, with average values for species ranging from −12.2‰ to +11.7‰. We define this difference as εpor, a term that encompasses diagenetic porphyrins and chlorins, as well as chlorophyll. Negative values of εpor reflect chloropigments that are 15N-enriched relative to biomass. Notably, this enrichment appears to occur only in cyanobacteria. The average value of εpor 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., εpor values for freshwater Chroococcales resemble those of freshwater Nostocales but differ from those of marine Chroococcales. Our measured values of εpor for eukaryotic algae (range = 4.7–8.7‰) are similar to previous reports for pure cultures. For all taxa studied, values of εpor do not depend on the type of nitrogen substrate used for growth. The observed

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

    NASA Astrophysics Data System (ADS)

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

    1996-11-01

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

  17. Statistical analysis of litter experiments in teratology

    SciTech Connect

    Williams, R.; Buschbom, R.L.

    1982-11-01

    Teratological data is binary response data (each fetus is either affected or not) in which the responses within a litter are usually not independent. As a result, the litter should be taken as the experimental unit. For each litter, its size, n, and the number of fetuses, x, possessing the effect of interest are recorded. The ratio p = x/n is then the basic data generated by the experiment. There are currently three general approaches to the analysis of teratological data: nonparametric, transformation followed by t-test or ANOVA, and parametric. The first two are currently in wide use by practitioners while the third is relatively new to the field. These first two also appear to possess comparable power levels while maintaining the nominal level of significance. When transformations are employed, care must be exercised to check that the transformed data has the required properties. Since the data is often highly asymmetric, there may be no transformation which renders the data nearly normal. The parametric procedures, including the beta-binomial model, offer the possibility of increased power.

  18. Abundance of litter on Condor seamount (Azores, Portugal, Northeast Atlantic)

    NASA Astrophysics Data System (ADS)

    Pham, C. K.; Gomes-Pereira, J. N.; Isidro, E. J.; Santos, R. S.; Morato, T.

    2013-12-01

    Marine litter is an emerging problem for the world's ocean health but little is known on its distribution and abundance on seamounts and how it affects deep-sea ecosystems. The scientific underwater laboratory set up on Condor seamount offered an ideal case study for the first documentation of litter distribution on a shallow seamount with historical fishing. A total of 48 video transects deployed on the summit (n=45) and the northern flank (n=3) covered an area of 0.031 and 0.025km2, respectively, revealing 55 litter items. Litter density on the summit was 1439 litter items km-2, whilst on the deeper northern flank, estimates indicate densities of 397 litter items km-2. Lost fishing line was the dominant litter item encountered on both areas (73% of total litter on the summit and 50% on northern flank), all being entirely or partly entangled in the locally abundant gorgonians Dentomuricea cf. meteor and Viminella flagellum. Other items included lost weights, anchors and glass bottles. The predominance of lost fishing gear identifies the source of litter on Condor seamount as exclusively ocean-based and related to fishing activities. Abundance of litter on the Condor seamount was much lower than that reported from other locations closer to populated areas.

  19. Trees as templates for tropical litter arthropod diversity.

    PubMed

    Donoso, David A; Johnston, Mary K; Kaspari, Michael

    2010-09-0