Large old trees influence patterns of delta13C and delta15N in forests.

PubMed

Weber, Pascale; Bol, Roland; Dixon, Liz; Bardgett, Richard D

2008-06-01

Large old trees are the dominant primary producers of native pine forest, but their influence on spatial patterns of soil properties and potential feedback to tree regeneration in their neighbourhood is poorly understood. We measured stable isotopes of carbon (delta(13)C) and nitrogen (delta(15)N) in soil and litter taken from three zones of influence (inner, middle and outer zone) around the trunk of freestanding old Scots pine (Pinus sylvestris L.) trees, to determine the trees' influence on below-ground properties. We also measured delta(15)N and delta(13)C in wood cores extracted from the old trees and from regenerating trees growing within their three zones of influence. We found a significant and positive gradient in soil delta(15)N from the inner zone, nearest to the tree centre, to the outer zone beyond the tree crown. This was probably caused by the higher input of (15)N-depleted litter below the tree crown. In contrast, the soil delta(13)C did not change along the gradient of tree influence. Distance-related trends, although weak, were visible in the wood delta(15)N and delta(13)C of regenerating trees. Moreover, the wood delta(15)N of small trees showed a weak negative relationship with soil N content in the relevant zone of influence. Our results indicate that large old trees control below-ground conditions in their immediate surroundings, and that stable isotopes might act as markers for the spatial and temporal extent of these below-ground effects. John Wiley & Sons, Ltd

STELLAR ORIGINS OF EXTREMELY {sup 13}C- AND {sup 15}N-ENRICHED PRESOLAR SIC GRAINS: NOVAE OR SUPERNOVAE?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Nan; Nittler, Larry R.; Alexander, Conel M. O’D.

Extreme excesses of {sup 13}C ({sup 12}C/{sup 13}C < 10) and {sup 15}N ({sup 14}N/{sup 15}N < 20) in rare presolar SiC grains have been considered diagnostic of an origin in classical novae, though an origin in core collapse supernovae (CCSNe) has also been proposed. We report C, N, and Si isotope data for 14 submicron- to micron-sized {sup 13}C- and {sup 15}N-enriched presolar SiC grains ({sup 12}C/{sup 13}C < 16 and {sup 14}N/{sup 15}N < ∼100) from Murchison, and their correlated Mg–Al, S, and Ca–Ti isotope data when available. These grains are enriched in {sup 13}C and {sup 15}N,more » but with quite diverse Si isotopic signatures. Four grains with {sup 29,30}Si excesses similar to those of type C SiC grains likely came from CCSNe, which experienced explosive H burning occurred during explosions. The independent coexistence of proton- and neutron-capture isotopic signatures in these grains strongly supports heterogeneous H ingestion into the He shell in pre-supernovae. Two of the seven putative nova grains with {sup 30}Si excesses and {sup 29}Si depletions show lower-than-solar {sup 34}S/{sup 32}S ratios that cannot be explained by classical nova nucleosynthetic models. We discuss these signatures within the CCSN scenario. For the remaining five putative nova grains, both nova and supernova origins are viable because explosive H burning in the two stellar sites could result in quite similar proton-capture isotopic signatures. Three of the grains are sub-type AB grains that are also {sup 13}C enriched, but have a range of higher {sup 14}N/{sup 15}N. We found that {sup 15}N-enriched AB grains (∼50 < {sup 14}N/{sup 15}N < ∼100) have distinctive isotopic signatures compared to putative nova grains, such as higher {sup 14}N/{sup 15}N, lower {sup 26}Al/{sup 27}Al, and lack of {sup 30}Si excess, indicating weaker proton-capture nucleosynthetic environments.« less

Stellar Origin of 15N-rich Presolar SiC Grains of Type AB: Supernovae with Explosive Hydrogen Burning

NASA Astrophysics Data System (ADS)

Liu, Nan; Nittler, Larry R.; Pignatari, Marco; O'D. Alexander, Conel M.; Wang, Jianhua

2017-06-01

We report C, N, and Si isotopic data for 59 highly 13C-enriched presolar submicron- to micron-sized SiC grains from the Murchison meteorite, including eight putative nova grains (PNGs) and 29 15N-rich (14N/15N ≤ solar) AB grains, and their Mg-Al, S, and Ca-Ti isotope data when available. These 37 grains are enriched in 13C, 15N, and 26Al with the PNGs showing more extreme enhancements. The 15N-rich AB grains show systematically higher 26Al and 30Si excesses than the 14N-rich AB grains. Thus, we propose to divide the AB grains into groups 1 (14N/15N < solar) and 2 (14N/15N ≥ solar). For the first time, we have obtained both S and Ti isotopic data for five AB1 grains and one PNG and found 32S and/or 50Ti enhancements. Interestingly, one AB1 grain had the largest 32S and 50Ti excesses, strongly suggesting a neutron-capture nucleosynthetic origin of the 32S excess and thus the initial presence of radiogenic 32Si (t 1/2 = 153 years). More importantly, we found that the 15N and 26Al excesses of AB1 grains form a trend that extends to the region in the N-Al isotope plot occupied by C2 grains, strongly indicating a common stellar origin for both AB1 and C2 grains. Comparison of supernova models with the AB1 and C2 grain data indicates that these grains came from supernovae that experienced H ingestion into the He/C zones of their progenitors.

15N fractionation in infrared-dark cloud cores

NASA Astrophysics Data System (ADS)

Zeng, S.; Jiménez-Serra, I.; Cosentino, G.; Viti, S.; Barnes, A. T.; Henshaw, J. D.; Caselli, P.; Fontani, F.; Hily-Blant, P.

2017-07-01

Context. Nitrogen is one of the most abundant elements in the Universe and its 14N/15N isotopic ratio has the potential to provide information about the initial environment in which our Sun formed. Recent findings suggest that the solar system may have formed in a massive cluster since the presence of short-lived radioisotopes in meteorites can only be explained by the influence of a supernova. Aims: We seek to determine the 14N/15N ratio towards a sample of cold and dense cores at the initial stages in their evolution. Methods: We observed the J = 1 → 0 transitions of HCN, H13CN, HC15N, HN13C, and H15NC towards a sample of 22 cores in four infrared-dark clouds (IRDCs) which are believed to be the precursors of high-mass stars and star clusters. Assuming LTE and a temperature of 15 K, the column densities of HCN, H13CN, HC15N, HN13C, and H15NC are calculated and their 14N/15N ratio is determined for each core. Results: The 14N/15N ratios measured in our sample of IRDC cores range between 70 and ≥763 in HCN and between 161 and 541 in HNC. These ratios are consistent with the terrestrial atmosphere (TA) and protosolar nebula (PSN) values, and with the ratios measured in low-mass prestellar cores. However, the 14N/15N ratios measured in cores C1, C3, F1, F2, and G2 do not agree with the results from similar studies towards the same cores using nitrogen bearing molecules with nitrile functional group (-CN) and nitrogen hydrides (-NH) although the ratio spread covers a similar range. Conclusions: Relatively low 14N/15N ratios amongst the four-IRDCs were measured in IRDC G which are comparable to those measured in small cosmomaterials and protoplanetary disks. The low average gas density of this cloud suggests that the gas density, rather than the gas temperature, may be the dominant parameter influencing the initial nitrogen isotopic composition in young PSN. The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http

High-Precision Measurements of 15N15N, 14N15N, and 14N2 in N2 and Potential Applications to Oceanic Nitrogen Cycle Research

NASA Astrophysics Data System (ADS)

Li, S.; Yeung, L.; Young, E. D.; Ostrom, N. E.; Haslun, J. A.

2016-02-01

The balance of nitrogen fixation and nitrogen loss in the oceans is uncertain. For example, anaerobic ammonia oxidation could account for 50% or more of marine N2 production, although its global importance is still poorly known. Isotopic ratios in fixed nitrogen species (e.g., δ15N and δ18O values of NO2- and NO3-) are widely used to trace preservation and removal of N-bearing compounds and/or isotopic variations of their different sources. However, these approaches in general probe only one side of the nitrogen mass balance—the "fixed" nitrogen reservoir—so they offer few constraints on the ultimate loss of nitrogen from that pool as N2. The rare isotopologue ratio 15N15N/14N2 in N2may provide information about those nitrogen-loss processes directly. We will report the first measurements of Δ30 (the abundance of 15N15N relative to that predicted by chance alone), made on a unique high-resolution mass spectrometer (the Nu Instruments Panorama), and we will discuss the potential utility of Δ30 as an independent tracer of the nitrogen cycle. The parameter Δ30 is insensitive to the bulk 15N/14N isotopic ratio of the reservoir; instead, it reflects isotopic ordering in N2, which is altered when N-N bonds are made or broken. Our preliminary measurements of N2 from denitrifying soils and pure cultures of denitrifiers indicate large kinetic isotopic effects during N-N bond formation that favor 15N15N production during denitrification. We also observed a nonstochastic excess of 15N15N in tropospheric N2 [Δ30 = +19.05 ± 0.12‰ (1σ)]. This excess likely comes from fixed-nitrogen loss processes in the biosphere. Variations in Δ30 of N2 from pure culture experiments (+16.96 to +18.95‰) probably reflect the different isotopic signatures of the enzymes that catalyze denitrification. So, enzyme-specific Δ30 values of dissolved N2 should provide information about the importance of different biochemical pathways of fixed-nitrogen loss (e.g., denitrification vs

Soil organic matter stability in agricultural land: New insights using δ15N, δ13C and C:N ratio

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

13C and (15)N chemical shift tensors in adenosine, guanosine dihydrate, 2'-deoxythymidine, and cytidine.

PubMed

Stueber, Dirk; Grant, David M

2002-09-04

The (13)C and (15)N chemical shift tensor principal values for adenosine, guanosine dihydrate, 2'-deoxythymidine, and cytidine are measured on natural abundance samples. Additionally, the (13)C and (15)N chemical shielding tensor principal values in these four nucleosides are calculated utilizing various theoretical approaches. Embedded ion method (EIM) calculations improve significantly the precision with which the experimental principal values are reproduced over calculations on the corresponding isolated molecules with proton-optimized geometries. The (13)C and (15)N chemical shift tensor orientations are reliably assigned in the molecular frames of the nucleosides based upon chemical shielding tensor calculations employing the EIM. The differences between principal values obtained in EIM calculations and in calculations on isolated molecules with proton positions optimized inside a point charge array are used to estimate the contributions to chemical shielding arising from intermolecular interactions. Moreover, the (13)C and (15)N chemical shift tensor orientations and principal values correlate with the molecular structure and the crystallographic environment for the nucleosides and agree with data obtained previously for related compounds. The effects of variations in certain EIM parameters on the accuracy of the shielding tensor calculations are investigated.

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

Stellar Origin of {sup 15}N-rich Presolar SiC Grains of Type AB: Supernovae with Explosive Hydrogen Burning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Nan; Nittler, Larry R.; Alexander, Conel M. O’D.

We report C, N, and Si isotopic data for 59 highly {sup 13}C-enriched presolar submicron- to micron-sized SiC grains from the Murchison meteorite, including eight putative nova grains (PNGs) and 29 {sup 15}N-rich ({sup 14}N/{sup 15}N ≤ solar) AB grains, and their Mg–Al, S, and Ca–Ti isotope data when available. These 37 grains are enriched in {sup 13}C, {sup 15}N, and {sup 26}Al with the PNGs showing more extreme enhancements. The {sup 15}N-rich AB grains show systematically higher {sup 26}Al and {sup 30}Si excesses than the {sup 14}N-rich AB grains. Thus, we propose to divide the AB grains into groupsmore » 1 ({sup 14}N/{sup 15}N < solar) and 2 ({sup 14}N/{sup 15}N ≥ solar). For the first time, we have obtained both S and Ti isotopic data for five AB1 grains and one PNG and found {sup 32}S and/or {sup 50}Ti enhancements. Interestingly, one AB1 grain had the largest {sup 32}S and {sup 50}Ti excesses, strongly suggesting a neutron-capture nucleosynthetic origin of the {sup 32}S excess and thus the initial presence of radiogenic {sup 32}Si ( t {sub 1/2} = 153 years). More importantly, we found that the {sup 15}N and {sup 26}Al excesses of AB1 grains form a trend that extends to the region in the N–Al isotope plot occupied by C2 grains, strongly indicating a common stellar origin for both AB1 and C2 grains. Comparison of supernova models with the AB1 and C2 grain data indicates that these grains came from supernovae that experienced H ingestion into the He/C zones of their progenitors.« less

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.

Urea and lipid extraction treatment effects on δ(15)N and δ(13)C values in pelagic sharks.

PubMed

Li, Yunkai; Zhang, Yuying; Hussey, Nigel E; Dai, Xiaojie

2016-01-15

Stable isotope analysis (SIA) provides a powerful tool to investigate diverse ecological questions for marine species, but standardized values are required for comparative assessments. For elasmobranchs, their unique osmoregulatory strategy involves retention of (15)N-depleted urea in body tissues and this may bias δ(15)N values. This may be a particular problem for large predatory species, where δ(15)N discrimination between predator and consumed prey can be small. We evaluated three treatments (deionized water rinsing [DW], chloroform/methanol [LE] and combined chloroform/methanol and deionized water rinsing [LE+DW]) applied to white muscle tissue of 125 individuals from seven pelagic shark species to (i) assess urea and lipid effects on stable isotope values determined by IRMS and (ii) investigate mathematical normalization of these values. For all species examined, the δ(15)N values and C:N ratios increased significantly following all three treatments, identifying that urea removal is required prior to SIA of pelagic sharks. The more marked change in δ(15)N values following DW (1.3 ± 0.4‰) and LE+DW (1.2 ± 0.6‰) than following LE alone (0.7 ± 0.4‰) indicated that water rinsing was more effective at removing urea. The DW and LE+DW treatments lowered the %N values, resulting in an increase in C:N ratios from the unexpected low values of <2.6 in bulk samples to ~3.1 ± 0.1, the expected value of protein. The δ(13)C values of all species also increased significantly following LE and LE+DW treatments. Given the mean change in δ(15)N(1.2 ± 0.6‰) and δ(13)C values (0.7 ± 0.4‰) across pelagic shark species, it is recommended that muscle tissue samples be treated with LE+DW to efficiently extract both urea and lipids to standardize isotopic values. Mathematical normalization of urea and lipid-extracted δ(15)N(LE+DW) and δ(13)C(LE+DW) values using the lipid-extracted δ(15)N(LE) and δ(13)C(LE) data were established for all pelagic shark species

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

NASA Astrophysics Data System (ADS)

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

2011-11-01

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

Afforestation impacts microbial biomass and its natural (13)C and (15)N abundance in soil aggregates in central China.

PubMed

Wu, Junjun; Zhang, Qian; Yang, Fan; Lei, Yao; Zhang, Quanfa; Cheng, Xiaoli

2016-10-15

We investigated soil microbial biomass and its natural abundance of δ(13)C and δ(15)N in aggregates (>2000μm, 250-2000μm, 53-250μm and <53μm) of afforested (implementing woodland and shrubland plantations) soils, adjacent croplands and open area (i.e., control) in the Danjiangkou Reservoir area of central China. The afforested soils averaged higher microbial biomass carbon (MBC) and nitrogen (MBN) levels in all aggregates than in open area and cropland, with higher microbial biomass in micro-aggregates (<250μm) than in macro-aggregates (>2000μm). The δ(13)C of soil microbial biomass was more enriched in woodland soils than in other land use types, while δ(15)N of soil microbial biomass was more enriched compared with that of organic soil in all land use types. The δ(13)C and δ(15)N of microbial biomass were positively correlated with the δ(13)C and δ(15)N of organic soil across aggregates and land use types, whereas the (13)C and (15)N enrichment of microbial biomass exhibited linear decreases with the corresponding C:N ratio of organic soil. Our results suggest that shifts in the natural (13)C and (15)N abundance of microbial biomass reflect changes in the stabilization and turnover of soil organic matter (SOM) and thereby imply that afforestation can greatly impact SOM accumulation over the long-term. Copyright © 2016 Elsevier B.V. All rights reserved.

N-Mesityl-C-acylketenimines: 1,5-Sigmatropic Shifts and Electrocyclization to Quinolines.

PubMed

Rao, V. V. Ramana; Fulloon, Belinda E.; Bernhardt, Paul V.; Koch, Rainer; Wentrup, Curt

1998-08-21

Flash vacuum thermolysis (FVT) of triazoles 6a-c generates alpha-oxoketenimines 10, the ester 10a being isolable. FVT of pyrroledione 8 generates the isomeric imidoylketene 9a. Ketenes 9 and ketenimines 10 undergo thermal interconversion by 1,3-shifts of methoxy and dimethylamino groups under mild FVT conditions (ca. 350-400 degrees C). Both 9 and 10 are directly observable by IR spectroscopy at either 77 K or on Ar matrix isolation at 12 K. On FVT at temperatures above ca. 400 degrees C, the ketenimines 10 undergo a 1,5-H shift to o-quinoid imines 12/13, followed by electrocyclization to dihydroquinolines 14 (unobserved) and 15 (observed by NMR). The latter are easily oxidized to alkylquinoline-3-carboxylates or quinoline-3-carboxamides 16 by atmospheric oxygen. Ab initio calculations on model compounds 18-23 predict an energy barrier of ca. 38 kcal mol(-)(1) (161 kJ mol(-)(1)) for the 1,5-H shift in N-(o-methylphenyl)ketenimines via the transition state TS19 followed by an electrocyclization barrier to dihydroquinoline 23a via TS22a of ca. 16 kcal mol(-)(1).

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

Determination of 15N/14N and 13C/12C in Solid and Aqueous Cyanides

USGS Publications Warehouse

Johnson, C.A.

1996-01-01

The stable isotopic compositions of nitrogen and carbon in cyanide compounds can be determined by combusting aliquots in sealed tubes to form N2 gas and CO2 gas and analyzing the gases by mass spectrometry. Free cyanide (CN-aq + HCNaq) in simple solutions can also be analyzed by first precipitating the cyanide as copper(II) ferrocyanide and then combusting the precipitate. Reproducibility is ??0.5??? or better for both ??15N and ??13C. If empirical corrections are made on the basis of carbon yields, the reproducibility of ??13C can be improved to ??0.2???. The analytical methods described herein are sufficiently accurate and precise to apply stable isotope techniques to problems of cyanide degradation in natural waters and industrial process solutions.

7Li(15N, 14C)8Be reaction at 81 MeV and 14C + 8Be interaction versus that of 13C + 8Be

NASA Astrophysics Data System (ADS)

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

2018-03-01

Angular distributions of the 7Li(15N, 14C)8Be reaction were measured at the energy Elab(15N) = 81 MeV. Data for transfer to the ground and first two excited states in 8Be were acquired as well as to the 14C ground and excited states. The reaction data were analyzed within the coupled-reaction-channels (CRC) method. The required 15N + 7Li entrance channel potential was taken from the 15N + 7Li elastic scattering. The 14C + 8Be potential was found by fitting Woods-Saxon form potentials to those generated by double folded real and imaginary potentials in the region of interaction. These generated potentials were then used in the CRC calculations. Proton transfer dominants this reaction, including to the excited states of 8Be. The reaction dependence on the exit channel potential was examined by using the 13C + 8Be potential previously deduced from the 9Be(12C, 13C)8Be reaction and 14C + 8Be from the 13C(9Be, 8Be)14C reaction.

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

NASA Astrophysics Data System (ADS)

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

1987-06-01

Distributions of δ 15N and δ 13C for biogenic substances in the Antarctic Ocean were investigated to construct a biogeochemical framework for assessing the Antarctic ecosystem. Phytoplankton exhibited particularly low δ 15N (0.5%) and 13C (-26.9%) values in pelagic plankton samples. High nitrate concentrations, and high PCO 2 in the surface waters on the southern side of the polar front and the resulting slow growth rate of phytoplankton under low light intensity are suggested as possible factors in causing the low isotopic compositions. Mean fractionation factors of 1.029 and 1.006 were estimated for photosynthetic carbon fixation and for the assimilation of inorganic nitrogeneous compounds (ammonium plus nitrate) during algal growth, respectively. Enrichment of 15N with increasing trophic level was confirmed for Antarctic ecosystems: δ15N animal% = 3.3 (trophic level -1) + δ5N algae, whereas 13C content did not increase in the same manner. Differences in lipid content among animals may be the main factor in causing this δ 13C anomaly. 15N and 13C abundance of sedimentary organic nitrogen differed from phytoplankton and settling particles. An exact mechanism for explaining the high δ 15N (around 5%) is not known. The very high δ 13C value of -20.5% at Sta. 3B may originate in ice algae that had grown under CO 2-limited conditions. Particles collected by sediment traps gave characteristically low δ 15N values (-3.0 to 0.9%), strongly suggesting a phytoplankton origin. The δ 15N and δ 13C values of settling material showed similar vertical profiles with depth which might arise from temporal variation of algal growth.

Bomb-pulse 14C analysis combined with 13C and 15N measurements in blood serum from residents of Malmö, Sweden.

PubMed

Georgiadou, Elisavet; Stenström, Kristina Eriksson; Uvo, Cintia Bertacchi; Nilsson, Peter; Skog, Göran; Mattsson, Sören

2013-05-01

The (14)C content of 60 human blood serum samples from residents of Malmö (Sweden) in 1978, obtained from a biobank, has been measured to estimate the accuracy of (14)C bomb-pulse dating. The difference between the date estimated using the Calibomb software and sampling date varied between -3 ± 0.4 and +0.2 ± 0.5 years. The average age deviation of all samples was -1.5 ± 0.7 years, with the delay between production and consumption of foodstuffs being probably the dominating cause. The potential influence of food habits on the (14)C date has been evaluated using stable isotope δ(13)C and δ(15)N analysis and information about the dietary habits of the investigated individuals. Although the group consisting of lacto-ovo vegetarians and vegans (pooled group) was not completely separated from the omnivores in a stable isotopic trophic level diagram, this analysis proved to add valuable information on probable dietary habits. The age deviation of the sampling date from the respective Calibomb date was found strongly correlated with the δ(13)C values, probably due to influence from marine diet components. For the omnivore individuals, there were indications of seasonal effects on δ(13)C and the age deviation. No significant correlation was found between the age deviation and the δ(15)N values of any dietary group. No influence of sex or year of birth was found on neither the (14)C nor the δ(13)C and δ(15)N values of the serum samples. The data were also divided into two groups (omnivores and pooled group), based on the level of δ(15)N in the samples. The consumption of high δ(15)N-valued fish and birds can be responsible for this clustering.

Variation in hair δ13C and δ15N values in long-tailed macaques (Macaca fascicularis) from Singapore

USGS Publications Warehouse

Schillaci, Michael A.; Castellini, J. Margaret; Stricker, Craig A.; Jones-Engel, Lisa; Lee, Benjamin P.Y.-H.

2014-01-01

Much of the primatology literature on stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) has focused on African and New World species, with comparatively little research published on Asian primates. Here we present hair δ13C and δ15N isotope values for a sample of 33 long-tailed macaques from Singapore. We evaluate the suggestion by a previous researcher that forest degradation and biodiversity loss in Singapore have led to a decline in macaque trophic level. The results of our analysis indicated significant spatial variability in δ13C but not δ15N. The range of variation in δ13C was consistent with a diet based on C3 resources, with one group exhibiting low values consistent with a closed canopy environment. Relative to other macaque species from Europe and Asia, the macaques from Singapore exhibited a low mean δ13C value but mid-range mean δ15N value. Previous research suggesting a decline in macaque trophic level is not supported by the results of our study.

Implications of new measurements of O-16 + p + C-12,13, N-14,15 for the abundances of C, N isotopes at the cosmic ray source

NASA Technical Reports Server (NTRS)

Guzik, T. G.; Wefel, J. P.; Crawford, H. J.; Greiner, D. E.; Lindstrom, P. J.; Schimmerling, W.; Symons, T. J. M.

1985-01-01

The fragmentation of a 225 MeV/n O-16 beam was investigated at the Bevalac. Preliminary cross sections for mass = 13, 14, 15 fragments are used to constrain the nuclear excitation functions employed in galactic propagation calculations. Comparison to cosmic ray isotonic data at low energies shows that in the cosmic ray source C-13/C approximately 2% and N-14/0=3-6%. No source abundance of N-15 is required with the current experimental results.

15N Hyperpolarization of Imidazole-15N2 for Magnetic Resonance pH Sensing via SABRE-SHEATH

PubMed Central

2016-01-01

15N nuclear spins of imidazole-15N2 were hyperpolarized using NMR signal amplification by reversible exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH). A 15N NMR signal enhancement of ∼2000-fold at 9.4 T is reported using parahydrogen gas (∼50% para-) and ∼0.1 M imidazole-15N2 in methanol:aqueous buffer (∼1:1). Proton binding to a 15N site of imidazole occurs at physiological pH (pKa ∼ 7.0), and the binding event changes the 15N isotropic chemical shift by ∼30 ppm. These properties are ideal for in vivo pH sensing. Additionally, imidazoles have low toxicity and are readily incorporated into a wide range of biomolecules. 15N-Imidazole SABRE-SHEATH hyperpolarization potentially enables pH sensing on scales ranging from peptide and protein molecules to living organisms. PMID:27379344

15N Hyperpolarization of Imidazole-15N2 for Magnetic Resonance pH Sensing via SABRE-SHEATH.

PubMed

Shchepin, Roman V; Barskiy, Danila A; Coffey, Aaron M; Theis, Thomas; Shi, Fan; Warren, Warren S; Goodson, Boyd M; Chekmenev, Eduard Y

2016-06-24

15 N nuclear spins of imidazole- 15 N 2 were hyperpolarized using NMR signal amplification by reversible exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH). A 15 N NMR signal enhancement of ∼2000-fold at 9.4 T is reported using parahydrogen gas (∼50% para-) and ∼0.1 M imidazole- 15 N 2 in methanol:aqueous buffer (∼1:1). Proton binding to a 15 N site of imidazole occurs at physiological pH (p K a ∼ 7.0), and the binding event changes the 15 N isotropic chemical shift by ∼30 ppm. These properties are ideal for in vivo pH sensing. Additionally, imidazoles have low toxicity and are readily incorporated into a wide range of biomolecules. 15 N-Imidazole SABRE-SHEATH hyperpolarization potentially enables pH sensing on scales ranging from peptide and protein molecules to living organisms.

Diet-tissue stable isotope (Δ(13)C and Δ(15)N) discrimination factors for multiple tissues from terrestrial reptiles.

PubMed

Steinitz, Ronnie; Lemm, Jeffrey M; Pasachnik, Stesha A; Kurle, Carolyn M

2016-01-15

Stable isotope analysis is a powerful tool for reconstructing trophic interactions to better understand drivers of community ecology. Taxon-specific stable isotope discrimination factors contribute to the best use of this tool. We determined the first Δ(13)C and Δ(15)N values for Rock Iguanas (Cyclura spp.) to better understand isotopic fractionation and estimate wild reptile foraging ecology. The Δ(13)C and Δ(15)N values between diet and skin, blood, and scat were determined from juvenile and adult iguanas held for 1 year on a known diet. We measured relationships between iguana discrimination factors and size/age and quantified effects of lipid extraction and acid treatment on stable isotope values from iguana tissues. Isotopic and elemental compositions were determined by Dumas combustion using an elemental analyzer coupled to an isotope ratio mass spectrometer using standards of known composition. The Δ(13)C and Δ(15)N values ranged from -2.5 to +6.5‰ and +2.2 to +7.5‰, respectively, with some differences among tissues and between juveniles and adults. The Δ(13)C values from blood and skin differed among species, but not the Δ(15)N values. The Δ(13)C values from blood and skin and Δ(15)N values from blood were positively correlated with size/age. The Δ(13)C values from scat were negatively correlated with size (not age). Treatment with HCl (scat) and lipid extraction (skin) did not affect the isotope values. These results should aid in the understanding of processes driving stable carbon and nitrogen isotope discrimination factors in reptiles. We provide estimates of Δ(13)C and Δ(15)N values and linear relationships between iguana size/age and discrimination factors for the best interpretation of wild reptile foraging ecology. Copyright © 2015 John Wiley & Sons, Ltd.

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

NASA Astrophysics Data System (ADS)

Vugmeyster, Liliya; Ostrovsky, Dmitry; Fu, Riqiang

2015-10-01

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

The effects of sex, tissue type, and dietary components on stable isotope discrimination factors (Δ13C and Δ15N) in mammalian omnivores.

PubMed

Kurle, Carolyn M; Koch, Paul L; Tershy, Bernie R; Croll, Donald A

2014-01-01

We tested the effects of sex, tissue, and diet on stable isotope discrimination factors (Δ(13)C and Δ(15)N) for six tissues from rats fed four diets with varied C and N sources, but comparable protein quality and quantity. The Δ(13)C and Δ(15)N values ranged from 1.7-4.1‰ and 0.4-4.3‰, respectively. Females had higher Δ(15)N values than males because males grew larger, whereas Δ(13)C values did not differ between sexes. Differences in Δ(13)C values among tissue types increased with increasing variability in dietary carbon sources. The Δ(15)N values increased with increasing dietary δ(15)N values for all tissues except liver and serum, which have fast stable isotope turnover times, and differences in Δ(15)N values among tissue types decreased with increasing dietary animal protein. Our results demonstrate that variability in dietary sources can affect Δ(13)C values, protein source affects Δ(15)N values even when protein quality and quantity are controlled, and the isotope turnover rate of a tissue can influence the degree to which diet affects Δ(15)N values.

Tracking the flow of bacterially derived 13C and 15N through soil faunal feeding channels.

PubMed

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

2011-06-15

The soil food web has been referred to as a 'black box', a 'poor man's tropical rainforest' and an 'enigma', due to its opacity, diversity and the limited insight into feeding specificity. Here we investigate the flow of C and N through the soil food web as a way to gain understanding of the feeding interactions occurring. A bacterium, Pseudomonas lurida, was introduced to soil cores from two different habitats, a grassland and a woodland with the same soil type, enriched to 99 atom% in (13)C and (15)N, to trace the flow of bacterial C and N through the soil food web. Throughout the experiment the soil remained enriched in (13)C and (15)N. Almost all the invertebrates tested gained C and N enrichment indicative of the labelled bacteria, implying that bacterial feeding is a common mechanism within the soil. Only three groups were significantly enriched in both (13)C and (15)N in both habitats. These were Collembola (Entomobryomorpha), Acari (Oribatida), and Nematoda, indicating that these organisms are consuming the most bacteria within both systems. When the invertebrates were grouped into hypothesised trophic levels, those considered secondary decomposers were gaining the most enrichment across all invertebrates tested. This enrichment was also high in the micro-predators within the soil, implying that their main food source was the secondary decomposers, particularly the Collembola. Using an enriched bacterium to track the trophic transfer between organisms within the soil food web is a novel way of empirically showing that interactions are occurring, which normally cannot be seen. Copyright © 2011 John Wiley & Sons, Ltd.

The evaluation of a new method to extract spectroscopic factors using asymptotic normalization coefficients and the astrophysical ^14C(n,γ)^15C reaction rate

NASA Astrophysics Data System (ADS)

McCleskey, M.; Mukhamedzhanov, A. M.; Trache, L.; Banu, A.; Goldberg, V.; Roeder, B. T.; Simmons, E. N.; Spiridon, A.; Tribble, R. E.

2011-10-01

A new method to determine spectroscopic factors (SFs) that utilizes asymptotic normalization coefficients (ANCs) has been tested at Texas A&M, using ^15C as a test case. The method would use the ANC to fix the external contribution to a non-peripheral reaction which would otherwise be free to vary to unphysical values in a traditional approach. The investigation consisted of two parts. First, the ANC for the ^14C+n configuration in ^15C was determined from the heavy ion neutron transfer reaction ^13C(^14C,^15C)^12C and the inverse kinematics reaction d(^14C,p)^15C. Both of these reactions were measured at sufficiently low energy to be peripheral. Next, a non-peripheral reaction ^14C(d,p)^15C was measured with an incident deuteron energy of 60 MeV, and this reaction was used along with the previously determined ANC to attempt to find the SF. The ANC was also used to calculate the astrophysical neutron direct capture rate for ^14C(n,γ)^15C, which was compared with recent direct experimental results.

Box-modeling of 15N/14N in mammals.

PubMed

Balter, Vincent; Simon, Laurent; Fouillet, Hélène; Lécuyer, Christophe

2006-03-01

The 15N/14N signature of animal proteins is now commonly used to understand their physiology and quantify the flows of nutrient in trophic webs. These studies assume that animals are predictably 15N-enriched relative to their food, but the isotopic mechanism which accounts for this enrichment remains unknown. We developed a box model of the nitrogen isotope cycle in mammals in order to predict the 15N/14N ratios of body reservoirs as a function of time, N intake and body mass. Results of modeling show that a combination of kinetic isotope fractionation during the N transfer between amines and equilibrium fractionation related to the reversible conversion of N-amine into ammonia is required to account for the well-established approximately 4 per thousand 15N-enrichment of body proteins relative to the diet. This isotopic enrichment observed in proteins is due to the partial recycling of 15N-enriched urea and the urinary excretion of a fraction of the strongly 15N-depleted ammonia reservoir. For a given body mass and diet delta15N, the isotopic compositions are mainly controlled by the N intake. Increase of the urea turnover combined with a decrease of the N intake lead to calculate a delta15N increase of the proteins, in agreement with the observed increase of collagen delta15N of herbivorous animals with aridity. We further show that the low delta15N collagen values of cave bears cannot be attributed to the dormancy periods as it is commonly thought, but inversely to the hyperphagia behavior. This model highlights the need for experimental investigations performed with large mammals in order to improve our understanding of natural variations of delta15N collagen.

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

EPA Science Inventory

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

Elucidating the trophodynamics of four coral reef fishes of the Solomon Islands using δ15N and δ13C

NASA Astrophysics Data System (ADS)

Greenwood, N. D. W.; Sweeting, C. J.; Polunin, N. V. C.

2010-09-01

Size-related diet shifts are important characteristics of fish trophodynamics. Here, body size-related changes in muscle δ15N and δ13C of four coral reef fishes, Acanthurus nigrofuscus (herbivore), Chaetodon lunulatus (corallivore) , Chromis xanthura (planktivore) and Plectropomus leopardus (piscivore) were investigated at two locations in the Solomon Islands. All four species occupied distinct isotopic niches and the concurrent δ13C' values of C. xanthura and P. leopardus suggested a common planktonic production source. Size-related shifts in δ15N, and thus trophic level, were observed in C. xanthura, C. lunulatus and P. leopardus, and these trends varied between location, indicating spatial differences in trophic ecology. A literature review of tropical fishes revealed that positive δ15N-size trends are common while negative δ15N-size trends are rare. Size-δ15N trends fall into approximately equal groups representing size-based feeding within a food chain, and that associated with a basal resource shift and occurs in conjunction with changes in production source, indicated by δ13C. The review also revealed large scale differences in isotope-size trends and this, combined with small scale location differences noted earlier, highlights a high degree of plasticity in the reef fishes studied. This suggests that trophic size analysis of reef fishes would provide a productive avenue to identify species potentially vulnerable to reef impacts as a result of constrained trophic behaviour.

Hyperpolarized 13 C,15 N2 -Urea MRI for assessment of the urea gradient in the porcine kidney.

PubMed

Hansen, Esben S S; Stewart, Neil J; Wild, Jim M; Stødkilde-Jørgensen, Hans; Laustsen, Christoffer

2016-12-01

A decline in cortico-medullary osmolality gradient of the kidney may serve as an early indicator of pathological disruption of the tubular reabsorption process. The purpose of this study was to investigate the feasibility of hyperpolarized 13 C, 15 N 2 -urea MRI as a biomarker of renal function in healthy porcine kidneys resembling the human physiology. Five healthy female Danish domestic pigs (weight 30 kg) were scanned at 3 Tesla (T) using a 13 C 3D balanced steady-state MR pulse sequence following injection of hyperpolarized 13 C, 15 N 2 -urea via a femoral vein catheter. Images were acquired at different time points after urea injection, and following treatment with furosemide. A gradient in cortico-medullary urea was observed with an intramedullary accumulation 75 s after injection of hyperpolarized 13 C, 15 N 2 -urea, whereas images acquired at earlier time points postinjection were dominated by cortical perfusion. Furosemide treatment resulted in an increased urea accumulation in the cortical space, leading to a reduction of the medullary-to-cortical signal ratio of 49%. This study demonstrates that hyperpolarized 13 C, 15 N 2 -urea MRI is capable of identifying the intrarenal accumulation of urea and can differentiate acute renal functional states in multipapillary kidneys, highlighting the potential for human translation. Magn Reson Med 76:1895-1899, 2016. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ashburn, D.A.; Garcia, K.; Hanners, J.L.

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{submore » 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.« less

Assignment of the sup 1 H and sup 15 N NMR spectra of Rhodobacter capsulatus ferrocytochrome c sub 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gooley, P.R.; Caffrey, M.S.; Cusanovich, M.A.

1990-03-06

The peptide resonances of the {sup 1}H and {sup 15}N nuclear magnetic resonance spectra of ferrocytochrome c{sub 2} from Rhodobacter capsulatus are sequentially assigned by a combination of 2D {sup 1}H-{sup 1}H and {sup 1}H-{sup 15}N spectroscopy, the latter performed on {sup 15}N-enriched protein. Short-range nuclear Overhauser effect (NOE) data show {alpha}-helices from residues 3-17, 55-65, 69-88, and 103-115. Within the latter two {alpha}-helices, there are three single 3{sub 10} turns, 70-72, 76-78, and 107-109. In addition {alpha}H-NH{sub i+1} and {alpha}H-NH{sub i+2} NOEs indicate that the N-terminal helix (3-17) is distorted. Compared to horse or tuna cytochrome c and cytochromemore » c{sub 2} of Rhodospirillium rubrum, there is a 6-residue insertion at residues 23-29 in R. capsulatus cytochrome c{sub 2}. The NOE data show that this insertion forms a loop, probably an {Omega} loop. {sup 1}H-{sup 15}N heteronuclear multiple quantum correlation experiments are used to follow NH exchange over a period of 40 h. As the 2D spectra are acquired in short time periods (30 min), rates for intermediate exchanging protons can be measured. Comparison of the NH exchange data for the N-terminal helix of cytochrome c{sub 2} of R. capsulatus with the highly homologous horse heart cytochrome c shows that this helix is less stable in cytochrome c{sub 2}.« less

Structure of indazole N1-oxide derivatives studied by X-ray, theoretical methods, 1H, 13C, 15N NMR and EI/MS

NASA Astrophysics Data System (ADS)

Gerpe, Alejandra; Piro, Oscar E.; Cerecetto, Hugo; González, Mercedes

2007-12-01

A series of indazole N1-oxide derivatives has been spectroscopically studied in solution using 1H, 13C, and 15N NMR based on pulsed field gradient selected PFG 1H sbnd X (X = 13C and 15N) gHMQC and gHMBC experiments. Some indazoles were prepared using a new methodology to compare its spectral and structural data with the indazole N1-oxide parent compounds. The 13C resonances of the indazole N1-oxide carbon 3 and 7a demonstrate the N-oxide push-electron capability. The 15N resonances of the indazole N-oxide, nitrogen 1, are near to 30 ppm more shielded than the corresponding values in the indazole heterocycle (deoxygenated form). Moreover, the structures of one indazole and one indazole N-oxide were unambiguously confirmed by X-ray crystallography. The solid state structures were contrasted with the theoretical ones obtained in vacuo at different calculus level. The aromaticity of the derivatives was studied analyzing the H sbnd H coupling constants of indazole's aromatic hydrogens and measuring C sbnd C distances in the solid state. The fragmentation that takes place in EI/MS was gathered for all the indazole N-oxide derivatives and the general fragmentation pattern analyzed.

The contamination of commercial 15N2 gas stocks with 15N-labeled nitrate and ammonium and consequences for nitrogen fixation measurements.

PubMed

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

2014-01-01

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

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

USGS Publications Warehouse

Qi, Haiping; Coplen, Tyler B.; Geilmann, Heike; Brand, Willi A.; Böhlke, J.K.

2003-01-01

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

Spatial and Temporal Variations in Stable Carbon (δ13C) and Nitrogen (δ15N) Isotopic Composition of Symbiotic Scleractinian Corals

PubMed Central

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

2013-01-01

Tropical scleractinian corals are considered autotrophic as they rely mainly on photosynthesis-derived nutrients transferred from their photosymbionts. Corals are also able to capture and ingest suspended particulate organic matter, so heterotrophy can be an important supplementary trophic pathway to optimize coral fitness. The aim of this in situ study was to elucidate the trophic status of 10 coral species under contrasted environmental conditions in a French Polynesian lagoon. Carbon (δ13C) and nitrogen (δ15N) isotopic compositions of coral host tissues and photosymbionts were determined at 3 different fringing reefs during wet and dry seasons. Our results highlighted spatial variability in stable isotopic compositions of both coral host tissues and photosymbionts. Samples from the site with higher level of suspended particulate matter were 13C-depleted and 15N-enriched relative to corals and photosymbionts from less turbid sites. However, differences in both δ13C and δ15N between coral host tissues and their photosymbionts (Δhost-photosymbionts 13C and Δhost-photosymbionts 15N) were small (0.27 ± 0.76‰ and 1.40 ± 0.90‰, respectively) and similar at all sites, thus indicating no general increases in the heterotrophic pathway. Depleted δ13C and enriched δ15N values of coral host tissues measured at the most turbid site were explained by changes in isotopic composition of the inorganic nutrients taken up by photosymbionts and also by changes in rate of isotopic fractionation with environmental conditions. Our results also highlighted a lack of significant temporal variations in δ13C and δ15N values of coral host and photosymbiont tissues and in Δhost-photosymbionts 13C and Δhost-photosymbionts 15N values. This temporal stability indicated that corals remained principally autotrophic even during the wet season when photosymbiont densities were lower and the concentrations of phytoplankton were higher. Increased coral heterotrophy with higher food

Nitrogen and 15N in the Mer Bleue peatland

NASA Astrophysics Data System (ADS)

Moore, Tim

2017-04-01

Although much of our attention in peatlands has focussed on carbon, as CO2, CH4 and DOC processing and fluxes, N plays an important role in the functioning of these ecosystems. Here, I present information on the distribution of N and 15N in plant and peat tissues and relate them to the cycling of N. N concentration in foliar tissues, ranged from 0.67 to 1.3% in evergreen shrubs and trees and mosses with little seasonal variation, and with a strong seasonal variation from 0.5 to 3.5% in the deciduous forbs, shrubs and trees, with a strong overall relationship to [chlorophyll]. Although the proportion of shrubs and mosses varied with microtopography the spatial foliar mass of N varied little with water table position, resulting in minor spatial variations in photosynthetic potential. Decomposition of plant tissues through litter to peat resulted in a decrease in the C:N ratio from about 50:1 to about 30:1 at the base of the profile, representing peat about 8000 yr old. This marginally larger loss of N through decomposition (mainly as TDN, 0.4 g N m-2 yr-1) compared to C produced a long-term N accumulation rate of 0.9 g N m-2 yr-1, being smaller in the bog phase, 0.6 N m-2 yr-1, and over past 150 yr, 0.8 g N m-2 yr-1. Although N is 'hard won' through N2 fixation, northern peatlands are significant global sinks of N and have limited N availability. del15N in foliar tissues ranged from -4 to -9 ‰ in evergreen and deciduous shrubs and trees, from -4 to -5 ‰ in mosses and from -1 to +1 ‰ in sedges and forbs. This appears to be a function of the mycorhizzal infection of the shrubs and trees, compared to sedges and forbs and the values for mosses may partially reflect the signature of atmospheric N deposition. There was no strong correlation between foliar [N] and del15N. In peat profiles from bog and fen sections of Mer Bleue, del15N values in peat fell from -5 to -2 ‰ in the top 10 cm to values of -1 to +1 ‰ at a depth of 40 cm and remained close to 0 ‰ below

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

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.

Dual element ((15)N/(14)N, (13)C/(12)C) isotope analysis of glyphosate and AMPA by derivatization-gas chromatography isotope ratio mass spectrometry (GC/IRMS) combined with LC/IRMS.

PubMed

Mogusu, Emmanuel O; Wolbert, J Benjamin; Kujawinski, Dorothea M; Jochmann, Maik A; Elsner, Martin

2015-07-01

To assess sources and degradation of the herbicide glyphosate [N-(phosphonomethyl) glycine] and its metabolite AMPA (aminomethylphosphonic acid), concentration measurements are often inconclusive and even (13)C/(12)C analysis alone may give limited information. To advance isotope ratio analysis of an additional element, we present compound-specific (15)N/(14)N analysis of glyphosate and AMPA by a two step derivatization in combination with gas chromatography/isotope ratio mass spectrometry (GC/IRMS). The N-H group was derivatized with isopropyl chloroformate (iso-PCF), and remaining acidic groups were subsequently methylated with trimethylsilyldiazomethane (TMSD). Iso-PCF treatment at pH <10 gave too low (15)N/(14)N ratios indicating an incomplete derivatization; in contrast, too high (15)N/(14)N ratios at pH >10 indicated decomposition of the derivative. At pH 10, and with an excess of iso-PCF by 10-24, greatest yields and accurate (15)N/(14)N ratios were obtained (deviation from elemental analyzer-IRMS: -0.2 ± 0.9% for glyphosate; -0.4 ± 0.7% for AMPA). Limits for accurate δ(15)N analysis of glyphosate and AMPA were 150 and 250 ng injected, respectively. A combination of δ(15)N and δ(13)C analysis by liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) (1) enabled an improved distinction of commercial glyphosate products and (2) showed that glyphosate isotope values during degradation by MnO2 clearly fell outside the commercial product range. This highlights the potential of combined carbon and nitrogen isotopes analysis to trace sources and degradation of glyphosate.

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

15N Hyperpolarization by Reversible Exchange Using SABRE-SHEATH.

PubMed

Truong, Milton L; Theis, Thomas; Coffey, Aaron M; Shchepin, Roman V; Waddell, Kevin W; Shi, Fan; Goodson, Boyd M; Warren, Warren S; Chekmenev, Eduard Y

2015-04-23

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% 15 N-polarization (Theis, T.; et al. J. Am. Chem. Soc. 2015 , 137 , 1404). Hyperpolarization on 15 N (and heteronuclei in general) may be advantageous because of the long-lived nature of the hyperpolarization on 15 N 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 15 N 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 15 N-hyperpolarization. The effects of parahydrogen pressure, flow rate, sample temperature, catalyst-to-substrate ratio, relaxation time ( T 1 ), and reversible oxygen quenching are studied on a test system of 15 N-pyridine in methanol- d 4 . Moreover, we demonstrate the first proof-of-principle 13 C-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 15 N images (2 × 2 mm 2 resolution). Importantly, this method enables hyperpolarization of molecular sites with NMR T 1 relaxation times suitable for biomedical imaging and spectroscopy.

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

PubMed

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

2013-01-01

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

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

PubMed Central

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

2013-01-01

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

Human baby hair amino acid natural abundance 15N-isotope values are not related to the 15N-isotope values of amino acids in mother's breast milk protein.

PubMed

Romek, Katarzyna M; Julien, Maxime; Frasquet-Darrieux, Marine; Tea, Illa; Antheaume, Ingrid; Hankard, Régis; Robins, Richard J

2013-12-01

Since exclusively breast-suckled infants obtain their nutrient only from their mother's milk, it might be anticipated that a correlation will exist between the (15)N/(14)N isotope ratios of amino acids of protein of young infants and those supplied by their mother. The work presented here aimed to determine whether amino nitrogen transfer from human milk to infant hair protein synthesized within the first month of life conserves the maternal isotopic signature or whether post-ingestion fractionation dominates the nitrogen isotope spectrum. The study was conducted at 1 month post-birth on 100 mother-infant pairs. Isotope ratios (15)N/(14)N and (13)C/(12)C were measured using isotope ratio measurement by Mass Spectrometry (irm-MS) for whole maternal milk, and infant hair and (15)N/(14)N ratios were also measured by GC-irm-MS for the N-pivaloyl-O-isopropyl esters of amino acids obtained from the hydrolysis of milk and hair proteins. The δ(15)N and δ(13)C (‰) were found to be significantly higher in infant hair than in breast milk (δ(15)N, P < 0.001; δ(13)C, P < 0.001). Furthermore, the δ(15)N (‰) of individual amino acids in infant hair was also significantly higher than that in maternal milk (P < 0.001). By calculation, the observed shift in isotope ratio was shown not to be accounted for by the amino acid composition of hair and milk proteins, indicating that it is not simply due to differences in the composition in the proteins present. Rather, it would appear that each pool-mother and infant-turns over independently, and that fractionation in infant N-metabolism even in the first month of life dominates over the nutrient N-content.

Investigations into the \\delta 15N and \\delta 13C of POM, Primary Producers, and Filter Feeders in the Florida Keys Coral Reef Tract

NASA Astrophysics Data System (ADS)

Lamb, K. A.; Swart, P. K.

2004-12-01

In order to examine the possible influences of anthropogenic wastes on the Florida Keys coral reef tract, water column particulate organic matter \\(POM\\), primary producers, and filter feeders were sampled from within the coastal waters of the reef tract, and analyzed for \\delta 15N and \\delta 13C isotopic composition. The POM was found to have a mean \\delta 15N value of +4.13\\permil (\\pm 1.03\\permil\\) and a mean \\delta 13C value of -19.93\\permil (\\pm 0.58\\permil). The \\delta 13C values for POM across the entire reef tract were heavier inshore \\(avg \\delta 13C = -18.29\\permil \\(\\pm 1.04\\permil\\)\\) and became lighter offshore \\(avg \\delta 13C = -21.41\\permil \\(\\pm 0.89\\permil\\)\\), which is consistent with influences from benthic algae/seagrass closer to shore in contrast to open-marine influences offshore. The \\delta 15N values for POM were neither temporally nor spatially interrelated, as the data showed no clear trend moving in either the inshore or offshore direction. Instead, our \\delta 15N values for POM reflect a combined influence from nitrogen fixation \\(\\approx0\\permil\\), zooplankton and other suspended particles, and not anthropogenic wastes \\(>+10\\permil\\), as other authors claim. The mean isotopic composition of various primary producers suggests a nitrogen fixation source of nutrients to the reef system (Halimeda sp. (\\delta 15N = 2.43\\permil; \\delta 13C = -18.04\\permill), Dictyota sp. (\\delta 15N = +2.86\\permil; \\delta 13C = -16.30\\permil), Thalassia sp. (\\delta 15N = 2.39\\permil; \\delta 13C = -10.32\\permil)), while filter feeders were found to have a mean isotopic composition more similar to POM values (sponge \\delta 15N = 4.95\\permil; \\delta 13C = -18.02\\permil). Our data simply do not appear to show evidence of anthropogenic influence on the Florida Keys reef tract. Further more, we suggest that \\delta 15N values of +4\\permil, which have recently been suggested to indicate anthropogenic

Retrospective characterization of ontogenetic shifts in killer whale diets via δ13C and δ15N analysis of teeth

USGS Publications Warehouse

Newsome, Seth D.; Etnier, Michael A.; Monson, Daniel H.; Fogel, Marilyn L.

2009-01-01

Metabolically inert, accretionary structures such as the dentin growth layers in teeth provide a life history record of individual diet with near-annual resolution. We constructed ontogenetic ??13C and ??15N profiles by analyzing tooth dentin growth layers from 13 individual killer whales Orcinus orca collected in the eastern northeast Pacific Ocean between 1961 and 2003. The individuals sampled were 6 to 52 yr old, representing 2 ecotypes-resident and transient - collected across ???25?? of latitude. The average isotopic values of transient individuals (n = 10) are consistent with a reliance on mammalian prey, while the average isotopic values of residents (n = 3) are consistent with piscivory. Regardless of ecotype, most individuals show a decrease in ??15N values of ???2.5% through the first 3 yr of life, roughly equivalent to a decrease of one trophic level. We interpret this as evidence of gradual weaning, after which, ontogenetic shifts in isotopic values are highly variable. A few individuals (n = 2) maintained relatively stable ??15N and ??13C values throughout the remainder of their lives, whereas ??15N values of most (n = 11) increased by ???1.5%, suggestive of an ontogenetic increase in trophic level. Significant differences in mean ??13C and ??15N values among transients collected off California suggest that individuality in prey preferences may be prevalent within this ecotype. Our approach provides retrospective individual life history and dietary information that cannot be obtained through traditional field observations of free-ranging and elusive species such as killer whales, including unique historic ecological information that pre-dates modern studies. By providing insights into individual diet composition, stable isotope analysis of teeth and/or bones may be the only means of evaluating a number of hypothesized historical dietary shifts in killer whales of the northeast Pacific Ocean. ?? Inter-Research 2009.

Retrospective characterization of ontogenetic shifts in killer whale diets via δ13C and δ15N analysis of teeth

USGS Publications Warehouse

Newsome, Seth D.; Etnier, Michael A.; Monson, Daniel H.; Fogel, Marilyn L.

2009-01-01

Metabolically inert, accretionary structures such as the dentin growth layers in teeth provide a life history record of individual diet with near-annual resolution. We constructed ontogenetic δ13C and δ15N profiles by analyzing tooth dentin growth layers from 13 individual killer whales Orcinus orca collected in the eastern northeast Pacific Ocean between 1961 and 2003. The individuals sampled were 6 to 52 yr old, representing 2 ecotypes—resident and transient—collected across ~25° of latitude. The average isotopic values of transient individuals (n = 10) are consistent with a reliance on mammalian prey, while the average isotopic values of residents (n = 3) are consistent with piscivory. Regardless of ecotype, most individuals show a decrease in δ15N values of ~2.5‰ through the first 3 yr of life, roughly equivalent to a decrease of one trophic level. We interpret this as evidence of gradual weaning, after which, ontogenetic shifts in isotopic values are highly variable. A few individuals (n = 2) maintained relatively stable δ15N and δ13C values throughout the remainder of their lives, whereas δ15N values of most (n = 11) increased by ~1.5‰, suggestive of an ontogenetic increase in trophic level. Significant differences in mean δ13C and δ15N values among transients collected off California suggest that individuality in prey preferences may be prevalent within this ecotype. Our approach provides retrospective individual life history and dietary information that cannot be obtained through traditional field observations of free-ranging and elusive species such as killer whales, including unique historic ecological information that pre-dates modern studies. By providing insights into individual diet composition, stable isotope analysis of teeth and/or bones may be the only means of evaluating a number of hypothesized historical dietary shifts in killer whales of the northeast Pacific Ocean

Ratios of N15/C12 and He4/C12 inclusive electroproduction cross sections in the nucleon resonance region

NASA Astrophysics Data System (ADS)

Bosted, P. E.; Fersch, R.; Adams, G.; Amarian, M.; Anefalos, S.; Anghinolfi, M.; Asryan, G.; Avakian, H.; Bagdasaryan, H.; Baillie, N.; Ball, J. P.; Baltzell, N. A.; Barrow, S.; Batourine, V.; Battaglieri, M.; Beard, K.; Bedlinskiy, I.; Bektasoglu, M.; Bellis, M.; Benmouna, N.; Biselli, A. S.; Bonner, B. E.; Bouchigny, S.; Boiarinov, S.; Bradford, R.; Branford, D.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Butuceanu, C.; Calarco, J. R.; Careccia, S. L.; Carman, D. S.; Carnahan, B.; Cazes, A.; Chen, S.; Cole, P. L.; Collins, P.; Coltharp, P.; Cords, D.; Corvisiero, P.; Crabb, D.; Crannell, H.; Crede, V.; Cummings, J. P.; de Masi, R.; de Vita, R.; de Sanctis, E.; Degtyarenko, P. V.; Denizli, H.; Dennis, L.; Deur, A.; Djalali, C.; Dodge, G. E.; Donnelly, J.; Doughty, D.; Dragovitsch, P.; Dugger, M.; Dharmawardane, K. V.; Dytman, S.; Dzyubak, O. P.; Egiyan, H.; Egiyan, K. S.; Elouadrhiri, L.; Eugenio, P.; Fatemi, R.; Fedotov, G.; Feuerbach, R. J.; Forest, T. A.; Fradi, A.; Funsten, H.; Garçon, M.; Gavalian, G.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guillo, M.; Guler, N.; Guo, L.; Gyurjyan, V.; Hadjidakis, C.; Hafidi, K.; Hakobyan, R. S.; Hardie, J.; Heddle, D.; Hersman, F. W.; Hicks, K.; Hleiqawi, I.; Holtrop, M.; Huertas, M.; Hyde-Wright, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Ito, M. M.; Jenkins, D.; Jo, H. S.; Joo, K.; Juengst, H. G.; Kalantarians, N.; Keith, C.; Kellie, J. D.; Khandaker, M.; Kim, K. Y.; Kim, K.; Kim, W.; Klein, A.; Klein, F. J.; Klusman, M.; Kossov, M.; Kramer, L. H.; Kubarovsky, V.; Kuhn, J.; Kuhn, S. E.; Kuleshov, S. V.; Lachniet, J.; Laget, J. M.; Langheinrich, J.; Lawrence, D.; Li, Ji; Lima, A. C. S.; Livingston, K.; Lu, H.; Lukashin, K.; MacCormick, M.; Markov, N.; McAleer, S.; McKinnon, B.; McNabb, J. W. C.; Mecking, B. A.; Mestayer, M. D.; Meyer, C. A.; Mibe, T.; Mikhailov, K.; Minehart, R.; Mirazita, M.; Miskimen, R.; Mokeev, V.; Morand, L.; Morrow, S. A.; Moteabbed, M.; Mueller, J.; Mutchler, G. S.; Nadel-Turonski, P.; Nasseripour, R.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Niczyporuk, B. B.; Niroula, M. R.; Niyazov, R. A.; Nozar, M.; O'Rielly, G. V.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Paterson, C.; Philips, S. A.; Pierce, J.; Pivnyuk, N.; Pocanic, D.; Pogorelko, O.; Polli, E.; Pozdniakov, S.; Preedom, B. M.; Price, J. W.; Prok, Y.; Protopopescu, D.; Qin, L. M.; Raue, B. A.; Riccardi, G.; Ricco, G.; Ripani, M.; Rosner, G.; Rossi, P.; Rowntree, D.; Rubin, P. D.; Sabatié, F.; Salgado, C.; Santoro, J. P.; Sapunenko, V.; Schumacher, R. A.; Serov, V. S.; Sharabian, Y. G.; Shaw, J.; Shvedunov, N. V.; Skabelin, A. V.; Smith, E. S.; Smith, L. C.; Sober, D. I.; Stavinsky, A.; Stepanyan, S. S.; Stepanyan, S.; Stokes, B. E.; Stoler, P.; Strauch, S.; Suleiman, R.; Taiuti, M.; Taylor, S.; Tedeschi, D. J.; Thoma, U.; Tkabladze, A.; Tkachenko, S.; Todor, L.; Ungaro, M.; Vineyard, M. F.; Vlassov, A. V.; Weinstein, L. B.; Weygand, D. P.; Williams, M.; Wolin, E.; Wood, M. H.; Yegneswaran, A.; Yun, J.; Zana, L.; Zhang, J.; Zhao, B.; Zhao, Z.

2008-07-01

The (W,Q2) dependence of the ratio of inclusive electron scattering cross sections for N15/C12 was determined in the kinematic ranges 0.8C12 using 1.6 to 2.5 GeV electrons were measured with very high statistical precision and were used to correct for He in the N and C targets. The (W,Q2) dependence of the He4/C12 ratios is in good agreement with that of the phenomenological model and exhibit significant resonance structure centered at W=0.94,1.23, and 1.5 GeV.

Three new HLA-C alleles (HLA-C*14:02:13, HLA-C*15:72 and HLA-C*15:74) in Saudi bone marrow donors.

PubMed

Fakhoury, H A; Jawdat, D; Alaskar, A S; Al Jumah, M; Cereb, N; Hajeer, A H

2015-10-01

Three new HLA-C alleles were identified by sequence-based typing method (SBT) in donors for the Saudi Bone Marrow Donor Registry (SBMDR). HLA-C*14:02:13 differs from HLA-C*14:02:01 by a silent G to A substitution at nucleotide position 400 in exon 2, where lysine at position 66 remains unchanged. HLA-C*15:72 differs from HLA-C*15:22 by a nonsynonymous C to A substitution at nucleotide position 796 in exon 3, resulting in an amino acid change from phenylalanine to leucine at position 116. HLA-C*15:74 differs from HLA-C*15:08 by a nonsynonymous C to T substitution at nucleotide position 914 in exon 3, resulting in an amino acid change from arginine to tryptophan at position 156. © 2015 John Wiley & Sons Ltd.

15N-labeled glycine synthesis.

PubMed

Tavares, Claudinéia R O; Bendassolli, José A; Coelho, Fernando; Sant'ana Filho, Carlos R; Prestes, Clelber V

2006-09-01

This work describes a method for 15N-isotope-labeled glycine synthesis, as well as details about a recovery line for nitrogen residues. To that effect, amination of alpha-haloacids was performed, using carboxylic chloroacetic acid and labeled aqueous ammonia (15NH3). Special care was taken to avoid possible 15NH3 losses, since its production cost is high. In that respect, although the purchase cost of the 13N-labeled compound (radioactive) is lower, the stable tracer produced constitutes an important tool for N cycling studies in living organisms, also minimizing labor and environmental hazards, as well as time limitation problems in field studies. The tests were carried out with three replications, and variable 15NH3aq volumes in the reaction were used (50, 100, and 150 mL), in order to calibrate the best operational condition; glycine masses obtained were 1.7, 2, and 3.2 g, respectively. With the development of a system for 15NH3 recovery, it was possible to recover 71, 83, and 87% of the ammonia initially used in the synthesis. With the required adaptations, the same system was used to recover methanol, and 75% of the methanol initially used in the amino acid purification process were recovered.

Recording 13C-15N HMQC 2D sparse spectra in solids in 30 s

NASA Astrophysics Data System (ADS)

Kupče, Ēriks; Trébosc, Julien; Perrone, Barbara; Lafon, Olivier; Amoureux, Jean-Paul

2018-03-01

We propose a dipolar HMQC Hadamard-encoded (D-HMQC-Hn) experiment for fast 2D correlations of abundant nuclei in solids. The main limitation of the Hadamard methods resides in the length of the encoding pulses, which results from a compromise between the selectivity and the sensitivity due to losses. For this reason, these methods should mainly be used with sparse spectra, and they profit from the increased separation of the resonances at high magnetic fields. In the case of the D-HMQC-Hn experiments, we give a simple rule that allows directly setting the optimum length of the selective pulses, versus the minimum separation of the resonances in the indirect dimension. The demonstration has been performed on a fully 13C,15N labelled f-MLF sample, and it allowed recording the build-up curves of the 13C-15N cross-peaks within 10 min. However, the method could also be used in the case of less sensitive samples, but with more accumulations.

Elucidating mineralisation-immobilisation dynamics in a grassland soil using triple 15N labelling in the field combined with a 15N tracing laboratory approach

NASA Astrophysics Data System (ADS)

Kleineidam, Kristina; Müller, Christoph

2017-04-01

labelling approach had been used. Here we present detailed gross N turnover dynamics and an improved conceptual model for the mineralisation-immobilisation dynamics in grassland soil. Literature cited Müller, C., Stevens, R.J., Laughlin, R.J., 2004. A 15N tracing model to analyse N transformations in old grassland soil. Soil Biology & Biochemistry 36, 619-632.

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...

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�

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

unlike previous works analyses for amino acids (representing organic products) rather than ammonium (NH4+) and nitrate (NO3-). Amino acids are commonly referred to as 'the building blocks of life' as they form the proteins which regulate life's essential biochemical reactions. Proteinaceous matter generally comprises 20-40% of total soil N and is ubiquitous in living organisms, so is a likely 'organic product' of microbial activity/assimilation. Hence, we consider it likely that amino acids represent the major organic nitrogenous products and a reasonable 'proxy' for/measure of the assimilation of an applied 15N substrate by the soil microbial biomass and an estimate of the newly synthesized soil protein. Brookes, P. C. et al. Soil Biol Biochem. 1985, 17, 837-842. Jenkinson, D. S. et al. Soil Biol Biochem. 2004, 36, 5-7. Nannipieri, P. et al. Plant Soil. 1999, 208, 43-56. Pilbeam, C. J. et al. J Agr Sci. 1997, 128, 415-424. Sebilo, M. et al. PNAS. 2013, 110, 18185-18189.

Determination of δ13C, δ15N, or δ34S by isotope-ratio-monitoring mass spectrometry using an elemental analyzer

USGS Publications Warehouse

Johnson, Craig A.; Stricker, Craig A.; Gulbransen, Cayce A.; Emmons, Matthew P.

2018-02-14

This report describes procedures used in the Geology, Geophysics, and Geochemistry Science Center of the U.S. Geological Survey in Denver, Colorado, to determine the stable-isotope ratios 13C/12C, 15N/14N, and 34S/32S in solid materials. The procedures use elemental analyzers connected directly to gas-source isotope-ratio mass spectrometers. A different elemental–analyzer–mass-spectrometer system is used for 13C/12C and 15N/14N than is used for 34S/32S to accommodate differences in reagents, catalysts, and instrument settings.

13C and 15N fractionation of CH4/N2 mixtures during photochemical aerosol formation: Relevance to Titan

NASA Astrophysics Data System (ADS)

Sebree, Joshua A.; Stern, Jennifer C.; Mandt, Kathleen E.; Domagal-Goldman, Shawn D.; Trainer, Melissa G.

2016-05-01

The ratios of the stable isotopes that comprise each chemical species in Titan's atmosphere provide critical information towards understanding the processes taking place within its modern and ancient atmosphere. Several stable isotope pairs, including 12C/13C and 14N/15N, have been measured in situ or probed spectroscopically by Cassini-borne instruments, space telescopes, or through ground-based observations. Current attempts to model the observed isotope ratios incorporate fractionation resulting from atmospheric diffusion, hydrodynamic escape, and primary photochemical processes. However, the effect of a potentially critical pathway for isotopic fractionation - organic aerosol formation and subsequent deposition onto the surface of Titan - has not been considered due to insufficient data regarding fractionation during aerosol formation. To better understand the nature of this process, we have conducted a laboratory study to measure the isotopic fractionation associated with the formation of Titan aerosol analogs, commonly referred to as 'tholins', via far-UV irradiation of several methane (CH4) and dinitrogen (N2) mixtures. Analysis of the δ13C and δ15N isotopic signatures of the photochemical aerosol products using an isotope ratio mass spectrometer (IRMS) show that fractionation direction and magnitude are dependent on the initial bulk composition of the gas mixture. In general, the aerosols showed enrichment in 13C and 14N, and the observed fractionation trends can provide insight into the chemical mechanisms controlling photochemical aerosol formation.

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

NASA Astrophysics Data System (ADS)

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

2001-05-01

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

Extending the cleavage rules for the hammerhead ribozyme: mutating adenosine15.1 to inosine15.1 changes the cleavage site specificity from N16.2U16.1H17 to N16.2C16.1H17.

PubMed Central

Ludwig, J; Blaschke, M; Sproat, B S

1998-01-01

In this paper, we show that an adenosine to inosine mutation at position 15.1 changes the substrate specificity of the hammerhead ribozyme from N16.2U16.1H17to N16.2C16.1H17(H represents A, C or U). This result extends the hammerhead cleavage triplet definition from N16.2U16.1H17to the more general N16.2Y16.1H17. Comparison of cleavage rates using I15.1ribozymes for NCH triplets and standard A15.1 ribozymes for NUH triplets under single turnover conditions shows similar or slightly enhanced levels of reactivity for the I15. 1-containing structures. The effect of I15.1 substitution was also tested in nuclease-resistant 2'- O -alkyl substituted derivatives (oligozymes), showing a similar level of activity for the NUH and NCH cleaving structures. The availability of NCH triplets that can be targeted without loss of efficiency increases the flexibility of ribozyme targeting strategies. This was demonstrated by an efficient cleavage of an HCV transcript at a previously inaccessible GCA site in codon 2. PMID:9580675

Variation in δ15N and δ13C values of forages for Arctic caribou: Effects of location, phenology and simulated digestion

USGS Publications Warehouse

Vansomeren, Lindsey L.; Barboza, Perry S.; Gustine, David D.; Bret-Harte, M. Syndonia

2017-01-01

RationaleThe use of stable isotopes for dietary estimates of wildlife assumes that there are consistent differences in isotopic ratios among diet items, and that the differences in these ratios between the diet item and the animal tissues (i.e., fractionation) are predictable. However, variation in isotopic ratios and fractionation of δ13C and δ15N values among locations, seasons, and forages are poorly described for arctic herbivores especially migratory species such as caribou (Rangifer tarandus).MethodsWe measured the δ13C and δ15N values of seven species of forage growing along a 200-km transect through the range of the Central Arctic caribou herd on the North Slope of Alaska over 2 years. We compared forages available at the beginning (May; n = 175) and the end (n = 157) of the growing season (September). Purified enzymes were used to measure N digestibility and to assess isotopic fractionation in response to nutrient digestibility during simulated digestion.ResultsValues for δ13C declined by 1.38 ‰ with increasing latitude across the transect, and increased by 0.44 ‰ from the beginning to the end of the season. The range of values for δ15N was greater than that for δ13C (13.29 vs 5.60 ‰). Differences in values for δ13C between graminoids (Eriophorum and Carex spp.) and shrubs (Betula and Salix spp.) were small but δ15N values distinguished graminoids (1.87 ± 1.02 ‰) from shrubs (−2.87 ± 2.93 ‰) consistently across season and latitude. However, undigested residues of forages were enriched in 15N when the digestibility of N was less than 0.67.ConclusionsAlthough δ15N values can distinguish plant groups in the diet of arctic herbivores, variation in the digestibility of dietary items may need to be considered in applying fractionation values for 15N to caribou and other herbivores that select highly digestible items (e.g. forbs) as well as heavily defended plants (e.g. woody browse).

Wild rabbit host and some parasites show trophic-level relationships for delta 13C and delta 15N: a first report.

PubMed

Boag, B; Neilson, R; Robinson, D; Scrimgeour, C M; Handley, L L

1998-01-01

We report the first isotopic study of an animal host-parasite system. Parasitic, intestinal nematodes, Graphidium strigosum and Passalurus ambiguus, were 15N-enriched relative to their host, the European rabbit Oryctolagus cuniculus, while parasitic cestodes, Cittataenia denticulata and Mosgovoyia pectinata, were 15N-depleted, suggesting different trophic relationships. Host embryos were more similar in their delta 13C and delta 15N values to maternal muscle than were any of the parasites. Coprophagy, the direct recycling of food by the rabbit eating its own faeces, did not lead to isotopic differences between stomach contents and faeces, suggesting that the major point for isotopic discrimination in lagomorph nitrogen metabolism is in the animal rather than in the gut. We conclude that bulk delta 13C and delta 15N can reveal valuable new information about host-parasite relationships, and these could be explored further at the biochemical level using compound-specific isotopic analyses.

δ15N value does not reflect fasting in mysticetes.

PubMed

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

2014-01-01

The finding that tissue δ(15)N values increase with protein catabolism has led researchers to apply this value to gauge nutritive condition in vertebrates. However, its application to marine mammals has in most occasions failed. We investigated the relationship between δ(15)N values and the fattening/fasting cycle in a model species, the fin whale, a migratory capital breeder that experiences severe seasonal variation in body condition. We analyzed two tissues providing complementary insights: one with isotopic turnover (muscle) and one that keeps a permanent record of variations in isotopic values (baleen plates). In both tissues δ(15)N values increased with intensive feeding but decreased with fasting, thus contradicting the pattern previously anticipated. The apparent inconsistency during fasting is explained by the fact that a) individuals migrate between different isotopic isoscapes, b) starvation may not trigger significant negative nitrogen balance, and c) excretion drops and elimination of 15N-depleted urine is minimized. Conversely, when intensive feeding is resumed in the northern grounds, protein anabolism and excretion start again, triggering 15N enrichment. It can be concluded that in whales and other mammals that accrue massive depots of lipids as energetic reserves and which have limited access to drinking water, the δ15N value is not affected by fasting and therefore cannot be used as an indication of nutritive condition.

Antihalo effects on reaction cross sections for C14,15,16 isotopes

NASA Astrophysics Data System (ADS)

Matsumoto, Takuma; Yahiro, Masanobu

2014-10-01

We study antihalo effects on reaction cross sections σR for C14,15,16 scattering from a C12 target at 83 MeV/nucleon, using the g-matrix double-folding model. C15 is described by the 14C+n two-body model that reproduces the measured large s-wave spectroscopic factor, i.e., the shell inversion that the 1s1/2 orbital is lower than the 0d5/2 orbital in energy. C16 is described by the 14C+n+n three-body model with the phenomenological three-body force (3BF) that explains the measured small s-wave spectroscopic factor. The 3BF allows the single-particle energies of the 14C+n subsystem to depend on the position r of the second neutron from the center of mass of the subsystem. The 1s1/2 orbital is lower than the 0d5/2 orbital for large r, but the shell inversion is restored for small r. Antihalo effects due to the "partial shell inversion" make σR for C16 smaller than that for C15. We also investigate projectile breakup effects on the mass-number dependence of σR with the continuum-discretized coupled-channel method.

Partial Molar Volumes of 15-Crown-5 Ether in Mixtures of N,N-Dimethylformamide with Water.

PubMed

Tyczyńska, Magdalena; Jóźwiak, Małgorzata

2014-01-01

The density of 15-crown-5 ether (15C5) solutions in the mixtures of N,N -dimethylformamide (DMF) and water (H 2 O) was measured within the temperature range 293.15-308.15 K using an Anton Paar oscillatory U-tube densimeter. The results were used to calculate the apparent molar volumes ( V Φ ) of 15C5 in the mixtures of DMF + H 2 O over the whole concentration range. Using the apparent molar volumes and Redlich and Mayer equation, the standard partial molar volumes of 15-crown-5 were calculated at infinite dilution ([Formula: see text]). The limiting apparent molar expansibilities ( α ) were also calculated. The data are discussed from the point of view of the effect of concentration changes on interactions in solution.

Mangrove isotopic (δ15N and δ13C) fractionation across a nitrogen vs. phosphorus limitation gradient

USGS Publications Warehouse

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

2002-01-01

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

1H, 13C, and 15N backbone assignment and secondary structure of the receptor-binding domain of vascular endothelial growth factor.

PubMed Central

Fairbrother, W. J.; Champe, M. A.; Christinger, H. W.; Keyt, B. A.; Starovasnik, M. A.

1997-01-01

Nearly complete sequence-specific 1H, 13C, and 15N resonance assignments are reported for the backbone atoms of the receptor-binding domain of vascular endothelial growth factor (VEGF), a 23-kDa homodimeric protein that is a major regulator of both normal and pathological angiogenesis. The assignment strategy relied on the use of seven 3D triple-resonance experiments [HN(CO)CA, HNCA, HNCO, (HCA)CONH, HN(COCA)HA, HN(CA)HA, and CBCA-(CO)NH] and a 3D 15N-TOCSY-HSQC experiment recorded on a 0.5 mM (12 mg/mL) sample at 500 MHz, pH 7.0, 45 degrees C. Under these conditions, 15N relaxation data show that the protein has a rotational correlation time of 15.0 ns. Despite this unusually long correlation time, assignments were obtained for 94 of the 99 residues; 8 residues lack amide 1H and 15N assignments, presumably due to rapid exchange of the amide 1H with solvent under the experimental conditions used. The secondary structure of the protein was deduced from the chemical shift indices of the 1H alpha, 13C alpha, 13C beta, and 13CO nuclei, and from analysis of backbone NOEs observed in a 3D 15N-NOESY-HSQC spectrum. Two helices and a significant amount of beta-sheet structure were identified, in general agreement with the secondary structure found in a recently determined crystal structure of a similar VEGF construct [Muller YA et al., 1997, Proc Natl Acad Sci USA 94:7192-7197]. PMID:9336848

Late Holocene monsoon climate of northeastern Taiwan inferred from elemental (C, N) and isotopic (δ13C, δ15N) data in lake sediments

NASA Astrophysics Data System (ADS)

Selvaraj, Kandasamy; Wei, Kuo-Yen; Liu, Kon-Kee; Kao, Shuh-Ji

2012-03-01

Little information exists about centennial-scale climate variability on oceanic islands in the western Pacific where the East Asian monsoon (EAM) strongly influences the climate, mountain ecosystem and the society. In this study, we investigate a 168 cm long sediment core recovered from Emerald Peak Lake in subalpine NE Taiwan for the contents of grain size, total organic carbon (TOC), C/N ratio, and stable isotopes (δ13C and δ15N) to reconstruct the monsoon climate and vegetation density during the late Holocene. Six radiocarbon (14C) ages obtained on plant remains used for the chronology indicate that the sediment core has been accumulated since ˜3770 cal BP with a mean sedimentation rate of 44.6 cm/ka. The sub-centennial resolution of our proxy records reveals strong fluctuations of the EAM and vegetation density for the past ˜3770 cal BP. The greater contents of coarse and medium sediments with overall decreasing trends from 3770 to 2000 cal BP suggest an increasing fine sediment influx from the catchment likely due to an increasing lake water level. Although low TOC content, C/N ratio, and enriched δ13C values in bulk and fine sediments during this interval suggest a sparsely vegetated catchment, increasing trends of TOC content and C/N ratio together with decreasing trends of δ13C and δ15N values indicate a strengthening pattern of summer monsoon. This is in contrast to a decreasing monsoon strength inferred from Dongge Cave δ18O record at that time, supporting the idea of anti-phasing of summer EAM and Indian summer monsoon. Since 2000 cal BP, higher content of fine sediments with high TOC content and C/N ratio but relatively depleted δ13C and low δ15N values suggest a high but stable lake water level and dense C3 plants, consistent with a stronger summer monsoon in a wet climate. Within this general trend, we interpret a prominent change of proxy parameters in sediments from ˜560 to 150 cal BP, as subtropical evidence for the Little Ice Age in NE

Benchmark fragment-based 1H, 13C, 15N and 17O chemical shift predictions in molecular crystals†

PubMed Central

Hartman, Joshua D.; Kudla, Ryan A.; Day, Graeme M.; Mueller, Leonard J.; Beran, Gregory J. O.

2016-01-01

The performance of fragment-based ab initio 1H, 13C, 15N and 17O chemical shift predictions is assessed against experimental NMR chemical shift data in four benchmark sets of molecular crystals. Employing a variety of commonly used density functionals (PBE0, B3LYP, TPSSh, OPBE, PBE, TPSS), we explore the relative performance of cluster, two-body fragment, and combined cluster/fragment models. The hybrid density functionals (PBE0, B3LYP and TPSSh) generally out-perform their generalized gradient approximation (GGA)-based counterparts. 1H, 13C, 15N, and 17O isotropic chemical shifts can be predicted with root-mean-square errors of 0.3, 1.5, 4.2, and 9.8 ppm, respectively, using a computationally inexpensive electrostatically embedded two-body PBE0 fragment model. Oxygen chemical shieldings prove particularly sensitive to local many-body effects, and using a combined cluster/fragment model instead of the simple two-body fragment model decreases the root-mean-square errors to 7.6 ppm. These fragment-based model errors compare favorably with GIPAW PBE ones of 0.4, 2.2, 5.4, and 7.2 ppm for the same 1H, 13C, 15N, and 17O test sets. Using these benchmark calculations, a set of recommended linear regression parameters for mapping between calculated chemical shieldings and observed chemical shifts are provided and their robustness assessed using statistical cross-validation. We demonstrate the utility of these approaches and the reported scaling parameters on applications to 9-tertbutyl anthracene, several histidine co-crystals, benzoic acid and the C-nitrosoarene SnCl2(CH3)2(NODMA)2. PMID:27431490

Benchmark fragment-based (1)H, (13)C, (15)N and (17)O chemical shift predictions in molecular crystals.

PubMed

Hartman, Joshua D; Kudla, Ryan A; Day, Graeme M; Mueller, Leonard J; Beran, Gregory J O

2016-08-21

The performance of fragment-based ab initio(1)H, (13)C, (15)N and (17)O chemical shift predictions is assessed against experimental NMR chemical shift data in four benchmark sets of molecular crystals. Employing a variety of commonly used density functionals (PBE0, B3LYP, TPSSh, OPBE, PBE, TPSS), we explore the relative performance of cluster, two-body fragment, and combined cluster/fragment models. The hybrid density functionals (PBE0, B3LYP and TPSSh) generally out-perform their generalized gradient approximation (GGA)-based counterparts. (1)H, (13)C, (15)N, and (17)O isotropic chemical shifts can be predicted with root-mean-square errors of 0.3, 1.5, 4.2, and 9.8 ppm, respectively, using a computationally inexpensive electrostatically embedded two-body PBE0 fragment model. Oxygen chemical shieldings prove particularly sensitive to local many-body effects, and using a combined cluster/fragment model instead of the simple two-body fragment model decreases the root-mean-square errors to 7.6 ppm. These fragment-based model errors compare favorably with GIPAW PBE ones of 0.4, 2.2, 5.4, and 7.2 ppm for the same (1)H, (13)C, (15)N, and (17)O test sets. Using these benchmark calculations, a set of recommended linear regression parameters for mapping between calculated chemical shieldings and observed chemical shifts are provided and their robustness assessed using statistical cross-validation. We demonstrate the utility of these approaches and the reported scaling parameters on applications to 9-tert-butyl anthracene, several histidine co-crystals, benzoic acid and the C-nitrosoarene SnCl2(CH3)2(NODMA)2.

Simple approach for the preparation of (15-15)N2-enriched water for nitrogen fixation assessments: evaluation, application and recommendations.

PubMed

Klawonn, Isabell; Lavik, Gaute; Böning, Philipp; Marchant, Hannah K; Dekaezemacker, Julien; Mohr, Wiebke; Ploug, Helle

2015-01-01

Recent findings revealed that the commonly used (15)N2 tracer assay for the determination of dinitrogen (N2) fixation can underestimate the activity of aquatic N2-fixing organisms. Therefore, a modification to the method using pre-prepared (15-15)N2-enriched water was proposed. Here, we present a rigorous assessment and outline a simple procedure for the preparation of (15-15)N2-enriched water. We recommend to fill sterile-filtered water into serum bottles and to add (15-15)N2 gas to the water in amounts exceeding the standard N2 solubility, followed by vigorous agitation (vortex mixing ≥ 5 min). Optionally, water can be degassed at low-pressure (≥950 mbar) for 10 min prior to the (15-15)N2 gas addition to indirectly enhance the (15-15)N2 concentration. This preparation of (15-15)N2-enriched water can be done within 1 h using standard laboratory equipment. The final (15)N-atom% excess was 5% after replacing 2-5% of the incubation volume with (15-15)N2-enriched water. Notably, the addition of (15-15)N2-enriched water can alter levels of trace elements in the incubation water due to the contact of (15-15)N2-enriched water with glass, plastic and rubber ware. In our tests, levels of trace elements (Fe, P, Mn, Mo, Cu, Zn) increased by up to 0.1 nmol L(-1) in the final incubation volume, which may bias rate measurements in regions where N2 fixation is limited by trace elements. For these regions, we tested an alternative way to enrich water with (15-15)N2. The (15-15)N2 was injected as a bubble directly to the incubation water, followed by gentle shaking. Immediately thereafter, the bubble was replaced with water to stop the (15-15)N2 equilibration. This approach achieved a (15)N-atom% excess of 6.6 ± 1.7% when adding 2 mL (15-15)N2 per liter of incubation water. The herein presented methodological tests offer guidelines for the (15)N2 tracer assay and thus, are crucial to circumvent methodological draw-backs for future N2 fixation assessments.

42 CFR 68c.15 - Additional conditions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 42 Public Health 1 2010-10-01 2010-10-01 false Additional conditions. 68c.15 Section 68c.15 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTE OF CHILD HEALTH AND HUMAN DEVELOPMENT CONTRACEPTION AND INFERTILITY RESEARCH LOAN...

42 CFR 68c.15 - Additional conditions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 42 Public Health 1 2012-10-01 2012-10-01 false Additional conditions. 68c.15 Section 68c.15 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTE OF CHILD HEALTH AND HUMAN DEVELOPMENT CONTRACEPTION AND INFERTILITY RESEARCH LOAN...

42 CFR 68c.15 - Additional conditions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 42 Public Health 1 2011-10-01 2011-10-01 false Additional conditions. 68c.15 Section 68c.15 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTE OF CHILD HEALTH AND HUMAN DEVELOPMENT CONTRACEPTION AND INFERTILITY RESEARCH LOAN...

Diet discrimination factors are inversely related to δ15 N and δ13C values of food for fish under controlled conditions.

PubMed

Dennis, Caroline A; Macneil, M Aaron; Rosati, Jennifer Y; Pitcher, Trevor E; Fisk, Aaron T

2010-12-30

A recent literature review reported negative relationships between diet discrimination factors (DDFs = X(fish) - X(food) ; X = δ(15) N or δ(13) C) and the values of δ(15) N and δ(13) C in the food of wild organisms but there has been no laboratory-based confirmation of these relationships to date. Laboratory reared guppies (Poecilia reticulata) fed a series of diets with a range of δ(13) C (-22.9 to -6.6‰) and δ(15) N (6.5 to 1586‰) values were used to magnify diet-tissue dynamics in order to calculate DDFs once the fish had achieved equilibrium with each of the diets. Values of DDFs range widely for δ(15) N (7.1 to -849‰) and δ(13) C (1.1 to -7.0‰) and showed a strong negative correlation with the stable isotope value in the food for δ(15) N (slope = -0.59 ± 0.02, r(2)  = 0.95) and δ(13) C (slope = -0.56 ± 0.02, r(2)  = 0.94). Based on these relationships, the magnitude of DDF change over environmentally relevant values of δ(15) N or δ(13) C would be significant and could confound the interpretation of stable isotopes in the environment. Using highly enriched experimental diets, our study adds to a growing number of studies that undermine the consistent trophic enrichment paradigm with results that demonstrate the currently poor mechanistic understanding of how DDFs arise. The results of our study highlight that the magnitude of the stable isotope values in prey must be considered when choosing DDF values. Future laboratory studies should therefore be directed at uncovering the mechanistic basis of DDFs and, like others before, we recommend the determination of diet-dependent DDFs under laboratory conditions before modeling dietary proportions or calculating trophic positions. Copyright © 2010 John Wiley & Sons, Ltd.

Nitrogen turnover of three different agricultural soils determined by 15N triple labelling

NASA Astrophysics Data System (ADS)

Fiedler, Sebastian R.; Kleineidam, Kristina; Strasilla, Nicol; Schlüter, Steffen; Reent Köster, Jan; Well, Reinhard; Müller, Christoph; Wrage-Mönnig, Nicole

2017-04-01

To meet the demand for data to improve existing N turnover models and to evaluate the effect of different soil physical properties on gross nitrogen (N) transformation rates, we investigated two arable soils and a grassland soil after addition of ammonium nitrate (NH4NO3), where either ammonium (NH4+), or nitrate (NO3-), or both pools have been labelled with 15N at 60 atom% excess (triple 15N tracing method). Besides NH4+, NO3- and nitrite (NO2-) contents with their respective 15N enrichment, nitrous oxide (N2O) and dinitrogen (N2) fluxes have been determined. Each soil was adjusted to 60 % of maximum water holding capacity and pre-incubated at 20˚ C for two weeks. After application of the differently labelled N fertilizer, the soils were further incubated at 20˚ C under aerobic conditions in a He-N2-O2 atmosphere (21 % O2, 76 He, 2% N2) to increase the sensitivity of N2 rates via the 15N gas flux method. Over a 2 week period soil N pools were quantified by 2 M KCl extraction (adjusted to pH 7 to prevent nitrite losses) (Stevens and Laughlin, 1995) and N gas fluxes were measured by gas chromatography in combination with IRMS. Here, we present the pool sizes and fluxes as well as the 15N enrichments during the study. Results are discussed in light of the soil differences that were responsible for the difference in gross N dynamics quantified by the 15N tracing model Ntrace (Müller et al., 2007). References Müller, C., T. Rütting, J. Kattge, R.J. Laughlin, and R.J. Stevens, (2007) Estimation of parameters in complex 15N tracing models by Monte Carlo sampling. Soil Biology & Biochemistry. 39(3): p. 715-726. Stevens, R.J. and R.J. Laughlin, (1995) Nitrite transformations during soil extraction with potassium chloride. Soil Science Society of America Journal. 59(3): p. 933-938.

40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this section...

40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this section...

40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this section...

40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this section...

40 CFR 721.6505 - Polymers of C13C15 oxoalcohol ethoxolates.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polymers of C13C15 oxoalcohol... Specific Chemical Substances § 721.6505 Polymers of C13C15 oxoalcohol ethoxolates. (a) Chemical substance... polymers of C13C15 oxoalcohol ethoxolates (PMNs P-96-950/951) are subject to reporting under this section...

Similarities and differences in 13C and 15N stable isotope ratios in two non-lethal tissue types from shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820)

USGS Publications Warehouse

DeVries, R. J.; Schramm, Harold L.

2015-01-01

We tested the hypothesis that δ13C and δ15N signatures of pectoral spines would provide measures of δ13C and δ15N similar to those obtained from fin clips for adult shovelnose sturgeon Scaphirhynchus platorynchus. Thirty-two shovelnose sturgeon (fork length [FL] = 500–724 mm) were sampled from the lower Mississippi River, USA on 23 February 2013. Isotopic relationships between the two tissue types were analyzed using mixed model analysis of covariance. Tissue types differed significantly for both δ13C (P < 0.01; spine: mean = −23.83, SD = 0.62; fin clip: mean = −25.74, SD = 0.97) and δ15N (P = 0.01; spine: mean = 17.01, SD = 0.51; fin clip: mean = 17.19, SD = 0.62). Neither FL nor the FL × tissue type interaction had significant (P > 0.05) effects on δ13C. Fin clip δ13C values were highly variable and weakly correlated (r = 0.16, P = 0.40) with those from pectoral spines. We found a significant FL-tissue type interaction for δ15N, reflecting increasing δ15N with FL for spines and decreasing δ15N with FL for fin clips. These results indicate that spines are not a substitute for fin clip tissue for measuring δ13C and δ15N for shovelnose sturgeon in the lower Mississippi River, but the two tissues have different turnover rates they may provide complementary information for assessing trophic position at different time scales.

Proton-Detected 15N NMR-Spectroscopy and Imaging

NASA Astrophysics Data System (ADS)

Freeman, D.; Sailasuta, N.; Sukumar, S.; Hurd, R. E.

1993-10-01

Proton detection of nitrogen-15, using gradients for coherence selection, was determined to be an effective method for obtaining spectra of 15N-labeled metabolites from extracts and biopsies of tissue infused with [15N] ammonium chloride. The advantage of gradient selection of coherence was best demonstrated by the almost complete single-shot elimination of solvent water in extracts and tissue water in biopsies. As a single-acquisition editing method in which only protons attached to 15N are detected, the potential limitations of dynamic range and motion are also reduced. Gradient-enhanced heteronuclear multiple-quantum coherence (1H[15N] HMQC) was compared with conventional HMQC, and despite selection of only one of the two heteronuclear pathways, GE-HMQC was found to be more effective for resolving the desired signal for dilute solutions; and with a single scan. In addition, effective water elimination made it possible to use the resolution advantage of a frequency-encoding dimension in proton-detected 15N imaging experiments. The limit of detection of the method at 500 MHz was 0.7 mM in 16 scans from a total volume of 400 μl. Signals from tissue extracts were observable in less than one minute for kidney, heart, brain, and muscle. Proton-detected 15N GE-HMQC images with a voxel size of 39 × 78 × 625 μm were obtained at 600 MHz from a 4 mM (1.6 μmol) 15N urea sample in less than four hours. Distribution of [15N] urea in the kidney was observed in a 600 MHz GE-HMQC image of the papilla and some cortical structures.

Mutual orientation of three magnetic tensors in a polycrystalline dipeptide by dipole-modulated 15N chemical shift spectroscopy

NASA Astrophysics Data System (ADS)

Hartzell, C. J.; Pratum, T. K.; Drobny, G.

1987-10-01

This study demonstrates the mutual orientation of three tensor interactions in a single NMR experiment. The orientation of the 15N chemical shift tensor relative to the molecular frame has thus been determined in polycrystalline L-[1-13C] alanyl-L-[15N] alanine. The 13C-15N and 15N-1H dipole interactions are determined using the 1H dipole-modulated, 13C dipole-coupled 15N spectrum obtained as a transform of the data in t2. From simulations of the experimental spectra, two sets of polar angles have been determined relating the 13C-15N and 15N-1H dipoles to the 15N chemical shift tensor. The values determined are βCN =106°, αCN =5° and βNH =-19°, αNH =12°. The experiment verifies, without reference to single crystal data, that σ33 lies in the peptide plane and σ22 is nearly perpendicular to the plane.

Speciation in the Fe(III)-Cl(I)-H2O System at 298.15 K, 313.15 K, and 333.15 K (25 °C, 40 °C, and 60 °C)

NASA Astrophysics Data System (ADS)

Jamett, Nathalie E.; Hernández, Pía C.; Casas, Jesús M.; Taboada, María E.

2018-02-01

This article presents the results on speciation of ferric iron generated by the dissolution of chemical reagent hydromolysite (ferric chloride hexahydrate, FeCl3:6H2O) in water at 298.15 K, 313.15 K, and 333.15 K (25 °C, 40 °C, and 60 °C). Experiments were performed with a thermoregulated system up to the equilibrium point, as manifested by solution pH. Solution samples were analyzed in terms of concentration, pH, and electrical conductivity. Measurements of density and refractive index were obtained at different temperatures and iron concentrations. A decrease of pH was observed with the increase in the amount of dissolved iron, indicating that ferric chloride is a strong electrolyte that reacts readily with water. Experimental results were modeled using the hydrogeochemical code PHREEQC in order to obtain solution speciation. Cations and neutral and anion complexes were simultaneously present in the system at the studied conditions according to model simulations, where dominant species included Cl-, FeCl2+, FeCl2 +, FeOHCl 2 0 , and H+. A decrease in the concentration of Cl- and Fe3+ ions took place with increasing temperature due to the association of Fe-Cl species. Standard equilibrium constants for the formation of FeOHCl 2 0 obtained in this study were log Kf0 = -0.8 ± 0.01 at 298.15 K (25 °C), -0.94 ± 0.02 at 313.15 K (40 °C), and -1.03 ± 0.01 at 333.15 K (60 °C).

Drying method has no substantial effect on δ(15)N or δ(13)C values of muscle tissue from teleost fishes.

PubMed

Bessey, Cindy; Vanderklift, Mathew A

2014-02-15

Stable isotope analysis (SIA) is a powerful tool in many fields of research that enables quantitative comparisons among studies, if similar methods have been used. The goal of this study was to determine if three different drying methods commonly used to prepare samples for SIA yielded different δ(15)N and δ(13)C values. Muscle subsamples from 10 individuals each of three teleost species were dried using three methods: (i) oven, (ii) food dehydrator, and (iii) freeze-dryer. All subsamples were analysed for δ(15)N and δ(13)C values, and nitrogen and carbon content, using a continuous flow system consisting of a Delta V Plus mass spectrometer and a Flush 1112 elemental analyser via a Conflo IV universal interface. The δ(13)C values were normalized to constant lipid content using the equations proposed by McConnaughey and McRoy. Although statistically significant, the differences in δ(15)N values between the drying methods were small (mean differences ≤0.21‰). The differences in δ(13)C values between the drying methods were not statistically significant, and normalising the δ(13)C values to constant lipid content reduced the mean differences for all treatments to ≤0.65‰. A statistically significant difference of ~2% in C content existed between tissues dried in a food dehydrator and those dried in a freeze-dryer for two fish species. There was no significant effect of fish size on the differences between methods. No substantial effect of drying method was found on the δ(15)N or δ(13)C values of teleost muscle tissue. Copyright © 2013 John Wiley & Sons, Ltd.

Simple approach for the preparation of 15−15N2-enriched water for nitrogen fixation assessments: evaluation, application and recommendations

PubMed Central

Klawonn, Isabell; Lavik, Gaute; Böning, Philipp; Marchant, Hannah K.; Dekaezemacker, Julien; Mohr, Wiebke; Ploug, Helle

2015-01-01

Recent findings revealed that the commonly used 15N2 tracer assay for the determination of dinitrogen (N2) fixation can underestimate the activity of aquatic N2-fixing organisms. Therefore, a modification to the method using pre-prepared 15−15N2-enriched water was proposed. Here, we present a rigorous assessment and outline a simple procedure for the preparation of 15−15N2-enriched water. We recommend to fill sterile-filtered water into serum bottles and to add 15−15N2 gas to the water in amounts exceeding the standard N2 solubility, followed by vigorous agitation (vortex mixing ≥ 5 min). Optionally, water can be degassed at low-pressure (≥950 mbar) for 10 min prior to the 15−15N2 gas addition to indirectly enhance the 15−15N2 concentration. This preparation of 15−15N2-enriched water can be done within 1 h using standard laboratory equipment. The final 15N-atom% excess was 5% after replacing 2–5% of the incubation volume with 15−15N2-enriched water. Notably, the addition of 15−15N2-enriched water can alter levels of trace elements in the incubation water due to the contact of 15−15N2-enriched water with glass, plastic and rubber ware. In our tests, levels of trace elements (Fe, P, Mn, Mo, Cu, Zn) increased by up to 0.1 nmol L−1 in the final incubation volume, which may bias rate measurements in regions where N2 fixation is limited by trace elements. For these regions, we tested an alternative way to enrich water with 15−15N2. The 15−15N2 was injected as a bubble directly to the incubation water, followed by gentle shaking. Immediately thereafter, the bubble was replaced with water to stop the 15−15N2 equilibration. This approach achieved a 15N-atom% excess of 6.6 ± 1.7% when adding 2 mL 15−15N2 per liter of incubation water. The herein presented methodological tests offer guidelines for the 15N2 tracer assay and thus, are crucial to circumvent methodological draw-backs for future N2 fixation assessments. PMID:26300853

The Role of Anthropogenic Activity and Climate on δ15N Values of Cave Bat Guano

NASA Astrophysics Data System (ADS)

Cleary, D. M.; Onac, B. P.; Forray, F. L.; Wynn, J. G.

2016-12-01

Interest in the use of bat guano, a paleoclimate and paleoenvironmental resource, has rapidly increased over the past decade. However, to this point the utility of the δ15N values of guano as a potential proxy remains poorly understood. In contrast to the preservation of the original carbon isotopic composition of guano, δ15N values have the potential to be altered as a result of processes of nitrogen (N) cycling such as denitrification. However, the probability of N loss is relatively diminished in younger guano. Here we present a 1.5 m guano core from Zidită Cave in western Romania that began accumulating at ca. 913 ± 30 yr BP. To determine the utility of N isotopes in guano studies, the δ15N time-series was compared to δ13C time series and pollen records of the same core to determine if the environmental impact (pollen) or water availability (δ13C values) has an effect on N cycling. Unlike to previous guano studies, the N content in the core is nearly constant (%N > 9 %) for over 1 m of the core, indicating limited diagenesis. Although major changes in anthropogenic activities may have influenced some δ15N variation, some inconsistencies suggest this is not the primary controller. However, the correlation between δ15N and δ13C values (p < 0.01) in this C3-plant dominated ecosystem has been interpreted to reflect variation driven largely by water availability. Wetter periods indicated by lower δ13C values correspond with higher δ15N values of guano. These results indicate that when the area surrounding the Zidită Cave receives an increase in rainfall the N-cycle becomes more open with a decreased rate of denitrification or other processes that accumulate 15N in the soil reservoir. A 10-year instrumental precipitation dataset agrees with the relationship found between δ13C and δ15N time series. These results suggest that guano δ15N values from Zidită Cave are a suitable proxy record of climate for this type of system, but we emphasize that this

Nitrogen Fractionation in Protoplanetary Disks from the H13CN/HC15N Ratio

NASA Astrophysics Data System (ADS)

Guzmán, V. V.; Öberg, K. I.; Huang, J.; Loomis, R.; Qi, C.

2017-02-01

Nitrogen fractionation is commonly used to assess the thermal history of solar system volatiles. With ALMA it is for the first time possible to directly measure {}14{{N}}/{}15{{N}} ratios in common molecules during the assembly of planetary systems. We present ALMA observations of the {{{H}}}13{CN} and {{HC}}15{{N}} J=3-2 lines at 0.″5 angular resolution, toward a sample of six protoplanetary disks, selected to span a range of stellar and disk structure properties. Adopting a typical {}12{{C}}/{}13{{C}} ratio of 70, we find comet-like {}14{{N}}/{}15{{N}} ratios of 80-160 in five of the disks (3 T Tauri and 2 Herbig Ae disks) and lack constraints for one of the T Tauri disks (IM Lup). There are no systematic differences between T Tauri and Herbig Ae disks, or between full and transition disks within the sample. In addition, no correlation is observed between disk-averaged D/H and {}14{{N}}/{}15{{N}} ratios in the sample. One of the disks, V4046 Sgr, presents unusually bright HCN isotopologue emission, enabling us to model the radial profiles of {{{H}}}13{CN} and {{HC}}15{{N}}. We find tentative evidence of an increasing {}14{{N}}/{}15{{N}} ratio with radius, indicating that selective photodissociation in the inner disk is important in setting the {}14{{N}}/{}15{{N}} ratio during planet formation.

A priori predictions of the rotational constants for HC13N, HC15N, C5O

NASA Technical Reports Server (NTRS)

DeFrees, D. J.; McLean, A. D.

1989-01-01

Ab initio molecular orbital theory is used to estimate the rotational constant for several carbon-chain molecules that are candidates for discovery in interstellar space. These estimated rotational constants can be used in laboratory or astronomical searches for the molecules. The rotational constant for HC13N is estimated to be 0.1073 +/- 0.0002 GHz and its dipole moment 5.4 D. The rotational constant for HC15N is estimated to be 0.0724 GHz, with a somewhat larger uncertainty. The rotational constant of C5O is estimated to be 1.360 +/- 2% GHz and its dipole moment 4.4. D.

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

PubMed Central

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

2014-01-01

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

Asymmetric synthesis of [2,3-(13)C(2),(15)N]-4-benzyloxy-5,6-diphenyl-2,3,5,6-tetrahydro-4H-oxazine-2-one via lipase TL-mediated kinetic resolution of benzoin: general procedure for the synthesis of [2,3-(13)C(2),(15)N]-L-alanine.

PubMed

Aoyagi, Y; Iijima, A; Williams, R M

2001-11-30

Lipase TL-mediated kinetic resolution of benzoin proceeded to give the corresponding optically pure (R)-benzoin (R)-1. On the other hand, (S)-benzoin O-acetate (S)-7 could be hydrolyzed without epimerization to give (S)-benzoin (S)-1 under alkaline conditions. Furthermore, both enantiomers of benzoin (1) were converted to [(15)N]-(1R,2S)- and (1S,2R)- 2-amino-1,2-diphenylethanol (3a and 3b), respectively, according to the procedure reported previously. [2,3-(13)C(2),(15)N]-(5S,6R)-4-benzyloxy-5,6-diphenyl-2,3,5,6-tetrahydro-4H-oxazine-2-one (10) was synthesized from ethyl [1,2-(13)C(2)]bromoacetate and (1R,2S)-2-amino-1,2-diphenylethanol (3b) in three steps. Finally, [2,3-(13)C(2),(15)N]-L-alanine (12) was prepared via alkylation of the lactone 10 and hydrogenation of the alkylated product 11.

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

PubMed

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

2009-11-01

Accurate determinations of stable isotope ratios require a calibration using at least two reference materials with different isotopic compositions to anchor the isotopic scale and compensate for differences in machine slope. Ideally, the delta values of these reference materials should bracket the isotopic range of samples with unknown delta values. While the practice of analyzing two isotopically distinct reference materials is common for water (VSMOW-SLAP) and carbonates (NBS 19 and L-SVEC), the lack of widely available organic reference materials with distinct isotopic composition has hindered the practice when analyzing organic materials by elemental analysis/isotope ratio mass spectrometry (EA-IRMS). At present only L-glutamic acids USGS40 and USGS41 satisfy these requirements for delta13C and delta15N, with the limitation that L-glutamic acid is not suitable for analysis by gas chromatography (GC). We describe the development and quality testing of (i) four nicotine laboratory reference materials for on-line (i.e. continuous flow) hydrogen reductive gas chromatography-isotope ratio mass-spectrometry (GC-IRMS), (ii) five nicotines for oxidative C, N gas chromatography-combustion-isotope ratio mass-spectrometry (GC-C-IRMS, or GC-IRMS), and (iii) also three acetanilide and three urea reference materials for on-line oxidative EA-IRMS for C and N. Isotopic off-line calibration against international stable isotope measurement standards at Indiana University adhered to the 'principle of identical treatment'. The new reference materials cover the following isotopic ranges: delta2H(nicotine) -162 to -45 per thousand, delta13C(nicotine) -30.05 to +7.72 per thousand, delta15N(nicotine) -6.03 to +33.62 per thousand; delta15N(acetanilide) +1.18 to +40.57 per thousand; delta13C(urea) -34.13 to +11.71 per thousand, delta15N(urea) +0.26 to +40.61 per thousand (recommended delta values refer to calibration with NBS 19, L-SVEC, IAEA-N-1, and IAEA-N-2). Nicotines fill a gap as

The relative isotopic abundance (δ13C, δ15N) during composting of agricultural wastes in relation to compost quality and feedstock.

PubMed

Inácio, Caio T; Magalhães, Alberto M T; Souza, Paulo O; Chalk, Phillip M; Urquiaga, Segundo

2018-05-01

Variations in the relative isotopic abundance of C and N (δ 13 C and δ 15 N) were measured during the composting of different agricultural wastes using bench-scale bioreactors. Different mixtures of agricultural wastes (horse bedding manure + legume residues; dairy manure + jatropha mill cake; dairy manure + sugarcane residues; dairy manure alone) were used for aerobic-thermophilic composting. No significant differences were found between the δ 13 C values of the feedstock and the final compost, except for dairy manure + sugarcane residues (from initial ratio of -13.6 ± 0.2 ‰ to final ratio of -14.4 ± 0.2 ‰). δ 15 N values increased significantly in composts of horse bedding manure + legumes residues (from initial ratio of +5.9 ± 0.1 ‰ to final ratio of +8.2 ± 0.5 ‰) and dairy manure + jatropha mill cake (from initial ratio of +9.5 ± 0.2 ‰ to final ratio of +12.8 ± 0.7 ‰) and was related to the total N loss (mass balance). δ 13 C can be used to differentiate composts from different feedstock (e.g. C 3 or C 4 sources). The quantitative relationship between N loss and δ 15 N variation should be determined.

The measurement of muscle protein synthesis in broilers with a flooding dose technique: use of 15N-labelled phenylalanine, GC-MS and GC-C-IRMS.

PubMed

Dänicke, S; Böttcher, W; Simon, O; Jeroch, H

2001-01-01

An experiment was carried out to measure fractional muscle protein synthesis rates (k(s)) in broilers with injection of a flooding dose of phenylalanine (1 ml/100 g body weight of 150 mM phenylalanine; 38 atom percent excess (APE) [15N]phenylalanine). K(s) was calculated from the [15N] enrichment in phenylalanine of tissue-free and protein-bound phenylalanine using both gas chromatography mass spectrometry (GC-MS) and gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) for measurements after a 10 min isotope incorporation period. The tertiary-butyldimethylsilyl (t-BDMS) derivatives of phenylalanine were used for gas chromatographic separation in both systems. GC-MS and GC-C-IRMS were calibrated for a range of 7 to 37 [15N]APE and 0 to 0.62 [15N]APE, respectively, and for sample sizes of 0.45 to 4.5 nmol phenylalanine and 7 to 40 nmol phenylalanine, respectively. Reproducibility of standards as a measure of precision varied from 0.06 to 0.29 [15N]APE and from 0.0004 to 0.0018 [15N]APE in GC-MS and GC-C-IRMS, respectively. K(s) was measured in the m. pectoralis major of broilers fed rye based diets (56%) which were provided either unsupplemented (-) or supplemented (+) with an enzyme preparation containing xylanase. K(s) in breast muscles was significantly increased from 21.8%/d to 23.9%/d due to enzyme supplementation. It can be concluded from the study that the measurement of protein synthesis in broilers with the flooding dose technique can be carried out by using [15N]phenylalanine, GC-MS and GC-C-IRMS.

Accounting for the effects of lipids in stable isotope (δ13C and δ15N values) analysis of skin and blubber of balaenopterid whales.

PubMed

Ryan, Conor; McHugh, Brendan; Trueman, Clive N; Harrod, Chris; Berrow, Simon D; O'Connor, Ian

2012-12-15

Stable isotope values (δ(13)C and δ(15)N) of darted skin and blubber biopsies can shed light on habitat use and diet of cetaceans, which are otherwise difficult to study. Non-dietary factors affect isotopic variability, chiefly the depletion of (13)C due to the presence of (12)C-rich lipids. The efficacy of post hoc lipid-correction models (normalization) must be tested. For tissues with high natural lipid content (e.g., whale skin and blubber), chemical lipid extraction or normalization is necessary. C:N ratios, δ(13)C values and δ(15)N values were determined for duplicate control and lipid-extracted skin and blubber of fin (Balaenoptera physalus), humpback (Megaptera novaeangliae) and minke whales (B. acutorostrata) by continuous-flow elemental analysis isotope ratio mass spectrometry (CF-EA-IRMS). Six different normalization models were tested to correct δ(13)C values for the presence of lipids. Following lipid extraction, significant increases in δ(13)C values were observed for both tissues in the three species. Significant increases were also found for δ(15)N values in minke whale skin and fin whale blubber. In fin whale skin, the δ(15)N values decreased, with no change observed in humpback whale skin. Non-linear models generally out-performed linear models and the suitability of models varied by species and tissue, indicating the need for high model specificity, even among these closely related taxa. Given the poor predictive power of the models to estimate lipid-free δ(13)C values, and the unpredictable changes in δ(15)N values due to lipid-extraction, we recommend against arithmetical normalization in accounting for lipid effects on δ(13)C values for balaenopterid skin or blubber samples. Rather, we recommend that duplicate analysis of lipid-extracted (δ(13)C values) and non-treated tissues (δ(15)N values) be used. Copyright © 2012 John Wiley & Sons, Ltd.

Design of a 15N Molecular Unit to Achieve Long Retention of Hyperpolarized Spin State

NASA Astrophysics Data System (ADS)

Nonaka, Hiroshi; Hirano, Masashi; Imakura, Yuki; Takakusagi, Yoichi; Ichikawa, Kazuhiro; Sando, Shinsuke

2017-01-01

Nuclear hyperpolarization is a phenomenon that can be used to improve the sensitivity of magnetic resonance molecular sensors. However, such sensors typically suffer from short hyperpolarization lifetime. Herein we report that [15N, D14]trimethylphenylammonium (TMPA) has a remarkably long spin-lattice relaxation time (1128 s, 14.1 T, 30 °C, D2O) on its 15N nuclei and achieves a long retention of the hyperpolarized state. [15N, D14]TMPA-based hyperpolarized sensor for carboxylesterase allowed the highly sensitive analysis of enzymatic reaction by 15N NMR for over 40 min in phophate-buffered saline (H2O, pH 7.4, 37 °C).

Determination of the δ15N and δ13C of total nitrogen and carbon in solids; RSIL lab code 1832

USGS Publications Warehouse

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

2006-01-01

The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 1832 is to determine the δ(15N/14N), abbreviated as δ15N, and the δ(13C/12C), abbreviated as δ13C, of total nitrogen and carbon in a solid sample. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total nitrogen and carbon in a solid sample into N2 and CO2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines the relative difference in stable nitrogen isotope-amount ratio (15N/14N) of the product N2 gas and the relative difference in stable carbon isotope-amount ratio (13C/12C) of the product CO2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in tin capsules and loaded into a Costech Zero Blank Autosampler on the EA. Under computer control, samples then are dropped into a heated reaction tube that contains an oxidant, where combustion takes place in a helium atmosphere containing an excess of oxygen gas. Combustion products are transported by a helium carrier through a reduction furnace to remove excess oxygen and to convert all nitrous oxides into N2 and through a drying tube to remove water. The gas-phase products, mainly CO2 and N2, are separated by a gas chromatograph. The gas is then introduced into the IRMS through a Finnigan MAT (now Thermo Scientific) ConFlo II interface. The Finnigan MAT ConFlo II interface is used for introducing not only sample into the IRMS but also N2 and CO2 reference gases and helium for sample dilution. The flash combustion is quantitative; no isotopic fractionation is involved. The IRMS is a Thermo Scientific Delta V CF-IRMS. It has a universal triple collector, two wide cups with a narrow cup in the middle; it is capable of measuring mass/charge (m/z) 28, 29, 30 or with a magnet current change 44, 45, 46, simultaneously. The ion beams from these m/z values are as follows: m/z 28 = N2 = 14N/14N; m/z 29 = N2 = 14N/15N primarily; m/z 30 = NO = 14N/16O

13C and 15N natural isotope abundance reflects breast cancer cell metabolism

NASA Astrophysics Data System (ADS)

Tea, Illa; Martineau, Estelle; Antheaume, Ingrid; Lalande, Julie; Mauve, Caroline; Gilard, Francoise; Barillé-Nion, Sophie; Blackburn, Anneke C.; Tcherkez, Guillaume

2016-09-01

Breast cancer is the most common cancer in women worldwide. Despite the information provided by anatomopathological assessment and molecular markers (such as receptor expression ER, PR, HER2), breast cancer therapies and prognostics depend on the metabolic properties of tumor cells. However, metabolomics have not provided a robust and congruent biomarker yet, likely because individual metabolite contents are insufficient to encapsulate all of the alterations in metabolic fluxes. Here, we took advantage of natural 13C and 15N isotope abundance to show there are isotopic differences between healthy and cancer biopsy tissues or between healthy and malignant cultured cell lines. Isotope mass balance further suggests that these differences are mostly related to lipid metabolism, anaplerosis and urea cycle, three pathways known to be impacted in malignant cells. Our results demonstrate that the isotope signature is a good descriptor of metabolism since it integrates modifications in C partitioning and N excretion altogether. Our present study is thus a starting point to possible clinical applications such as patient screening and biopsy characterization in every cancer that is associated with metabolic changes.

A new organic reference material, l-glutamic acid, USGS41a, for δ(13) C and δ(15) N measurements - a replacement for USGS41.

PubMed

Qi, Haiping; Coplen, Tyler B; Mroczkowski, Stanley J; Brand, Willi A; Brandes, Lauren; Geilmann, Heike; Schimmelmann, Arndt

2016-04-15

The widely used l-glutamic acid isotopic reference material USGS41, enriched in both (13) C and (15) N, is nearly exhausted. A new material, USGS41a, has been prepared as a replacement for USGS41. USGS41a was prepared by dissolving analytical grade l-glutamic acid enriched in (13) C and (15) N together with l-glutamic acid of normal isotopic composition. The δ(13) C and δ(15) N values of USGS41a were directly or indirectly normalized with the international reference materials NBS 19 calcium carbonate (δ(13) CVPDB = +1.95 mUr, where milliurey = 0.001 = 1 ‰), LSVEC lithium carbonate (δ(13) CVPDB = -46.6 mUr), and IAEA-N-1 ammonium sulfate (δ(15) NAir = +0.43 mUr) and USGS32 potassium nitrate (δ(15) N = +180 mUr exactly) by on-line combustion, continuous-flow isotope-ratio mass spectrometry, and off-line dual-inlet isotope-ratio mass spectrometry. USGS41a is isotopically homogeneous; the reproducibility of δ(13) C and δ(15) N is better than 0.07 mUr and 0.09 mUr, respectively, in 200-μg amounts. It has a δ(13) C value of +36.55 mUr relative to VPDB and a δ(15) N value of +47.55 mUr relative to N2 in air. USGS41 was found to be hydroscopic, probably due to the presence of pyroglutamic acid. Experimental results indicate that the chemical purity of USGS41a is substantially better than that of USGS41. The new isotopic reference material USGS41a can be used with USGS40 (having a δ(13) CVPDB value of -26.39 mUr and a δ(15) NAir value of -4.52 mUr) for (i) analyzing local laboratory isotopic reference materials, and (ii) quantifying drift with time, mass-dependent isotopic fractionation, and isotope-ratio-scale contraction for isotopic analysis of biological and organic materials. Published in 2016. This article is a U.S. Government work and is in the public domain in the USA. Published in 2016. This article is a U.S. Government work and is in the public domain in the USA.

15 CFR 8c.60 - Communications.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Communications. 8c.60 Section 8c.60 Commerce and Foreign Trade Office of the Secretary of Commerce ENFORCEMENT OF NONDISCRIMINATION ON THE BASIS OF HANDICAP IN PROGRAMS OR ACTIVITIES CONDUCTED BY THE DEPARTMENT OF COMMERCE § 8c.60...

15 CFR 8c.40 - Employment.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Employment. 8c.40 Section 8c.40... BASIS OF HANDICAP IN PROGRAMS OR ACTIVITIES CONDUCTED BY THE DEPARTMENT OF COMMERCE § 8c.40 Employment... discrimination in employment under any program or activity conducted by the agency. The definitions, requirements...

Structural investigation of Titan tholins by solution-state 1H, 13C, and 15N NMR: one-dimensional and decoupling experiments.

PubMed

He, Chao; Lin, Guangxin; Upton, Kathleen T; Imanaka, Hiroshi; Smith, Mark A

2012-05-17

Titan, the largest moon of Saturn, is enveloped in a reddish brown organic haze. Titan haze is presumed to be formed from methane and nitrogen (CH(4) and N(2)) in Titan's upper atmosphere through energetic photochemistry and particle bombardment. Though Titan haze has been directly investigated using methods including the Cassini mission, its formation mechanism and the contributing chemical structures and prebiotic potential are still not well developed. We report here the structural investigation of the (13)C and (15)N labeled, simulated Titan haze aerosol (tholin) by solution-state NMR. The one-dimensional (1)H, (13)C, and (15)N NMR spectra and decoupling experiments indicate that the tholin sample contains amine, nitrile, imine, and N-heteroaromatic compounds of tremendous import in understanding complex organic chemistry in anaerobic, extraterrestrial environments.

Novel DNA packaging recognition in the unusual bacteriophage N15

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feiss, Michael; Geyer, Henriette, E-mail: henriettegeyer@gmail.com; Division of Viral Infections, Robert Koch Institute, Berlin

Phage lambda's cosB packaging recognition site is tripartite, consisting of 3 TerS binding sites, called R sequences. TerS binding to the critical R3 site positions the TerL endonuclease for nicking cosN to generate cohesive ends. The N15 cos (cos{sup N15}) is closely related to cos{sup λ}, but whereas the cosB{sup N15} subsite has R3, it lacks the R2 and R1 sites and the IHF binding site of cosB{sup λ}. A bioinformatic study of N15-like phages indicates that cosB{sup N15} also has an accessory, remote rR2 site, which is proposed to increase packaging efficiency, like R2 and R1 of lambda. N15more » plus five prophages all have the rR2 sequence, which is located in the TerS-encoding 1 gene, approximately 200 bp distal to R3. An additional set of four highly related prophages, exemplified by Monarch, has R3 sequence, but also has R2 and R1 sequences characteristic of cosB–λ. The DNA binding domain of TerS-N15 is a dimer. - Highlights: • There are two classes of DNA packaging signals in N15-related phages. • Phage N15's TerS binding site: a critical site and a possible remote accessory site. • Viral DNA recognition signals by the λ-like bacteriophages: the odd case of N15.« less

Effects of crop load on distribution and utilization of 13C and 15N and fruit quality for dwarf apple trees.

PubMed

Ding, Ning; Chen, Qian; Zhu, Zhanling; Peng, Ling; Ge, Shunfeng; Jiang, Yuanmao

2017-10-26

In order to define the effects of fruit crop load on the distribution and utilization of carbon and nitrogen in dwarf apple trees, we conducted three crop load levels (High-crop load, 6 fruits per trunk cross-sectional area (cm 2 , TCA)), Medium-crop load (4 fruits cm -2 TCA), Low-crop load (2 fruits cm -2 TCA)) in 2014 and 2015. The results indicated that the 15 N derived from fertilizer (Ndff) values of fruits decreased with the reduction of crop load, but the Ndff values of annual branches, leaves and roots increased. The plant 15 N-urea utilization rates on Medium and Low-crop load were 1.12-1.35 times higher than the High-crop load. With the reduction of crop load, the distribution rate of 13 C and 15 N in fruits was gradually reduced, but in contrast, the distribution of 13 C and 15 N gradually increased in annual branches, leaves and roots. Compared with High-crop load, the Medium and Low-crop load significantly improved fruit quality p < 0.05. Hence, controlling fruit load effectively regulated the distribution of carbon and nitrogen in plants, improved the nitrogen utilization rate and fruit quality. The appropriate crop load level for mature M.26 interstocks apple orchards was deemed to be 4.0 fruits cm -2 TCA.

Flotsam samples can help explain the δ13C and δ15N values of invertebrate resting stages in lake sediment

NASA Astrophysics Data System (ADS)

van Hardenbroek, Maarten; Rinta, Päivi; Wooller, Matthew J.; Schilder, Jos; Stötter, Tabea; Heiri, Oliver

2018-06-01

The stable isotopic composition of chitinous remains of Cladocera (water fleas) and freshwater Bryozoa (moss animals) preserved in lake sediment records can provide supporting insights into past environmental and ecosystem changes in lakes. Here we explore whether analyses of these remains isolated from lake flotsam can provide information on the driving variables affecting the isotopic composition of these remains. We collected flotsam in 53 lakes and found enough material in 33 lakes to measure the stable carbon and nitrogen isotope ratios (expressed as δ13C and δ15N values, respectively) of resting stages. These values were compared with lake characteristics, water chemistry measurements, and the isotopic composition of sedimentary organic matter (SOM) in the lakes. Mean δ13C values of cladoceran ephippia and SOM were correlated and both were also negatively correlated with deep water methane concentrations and indicators of lake stratification. This supports the findings of previous studies that methane-derived carbon can provide a significant proportion of carbon entering planktonic food webs. Mean δ15N values of bryozoan statoblasts and SOM were correlated, suggesting that both reflect the δ15N values of phytoplankton. Our results provide information on how environmental variables in lakes can influence the δ13C and δ15N values in resting stages, but flotsam samples can also potentially be used to assess seasonal stable isotope variability of resting stages. Both types of information are important to improve palaeoenvironmental interpretations of stable isotope records based on these remains in lake sediments.

First Measurement of the 14N/15N Ratio in the Analog of the Sun Progenitor OMC-2 FIR4

NASA Astrophysics Data System (ADS)

Kahane, Claudine; Jaber Al-Edhari, Ali; Ceccarelli, Cecilia; López-Sepulcre, Ana; Fontani, Francesco; Kama, Mihkel

2018-01-01

We present a complete census of the 14N/15N isotopic ratio in the most abundant N-bearing molecules toward the cold envelope of the protocluster OMC-2 FIR4, the best known Sun progenitor. To this scope, we analyzed the unbiased spectral survey obtained with the IRAM 30 m telescope at 3, 2, and 1 mm. We detected several lines of CN, HCN, HNC, HC3N, N2H+, and their respective 13C and 15N isotopologues. The lines’ relative fluxes are compatible with LTE conditions, and moderate line opacities have been corrected via a population diagram method or theoretical relative intensity ratios of the hyperfine structures. The five species lead to very similar 14N/15N isotopic ratios, without any systematic difference between amine- and nitrile-bearing species as previously found in other protostellar sources. The weighted average of the 14N/15N isotopic ratio is 270 ± 30. This 14N/15N value is remarkably consistent with the [250–350] range measured for the local galactic ratio but significantly differs from the ratio measured in comets (around 140). High-angular resolution observations are needed to examine whether this discrepancy is maintained at smaller scales. In addition, using the CN, HCN, and HC3N lines, we derived a 12C/13C isotopic ratio of 50 ± 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

Benchmarking theoretical formalisms for (p ,p n ) reactions: The 15C(p ,p n )14C case

NASA Astrophysics Data System (ADS)

Yoshida, K.; Gómez-Ramos, M.; Ogata, K.; Moro, A. M.

2018-02-01

Background: Proton-induced knockout reactions of the form (p ,p N ) have experienced a renewed interest in recent years due to the possibility of performing these measurements with rare isotopes, using inverse kinematics. Several theoretical models are being used for the interpretation of these new data, such as the distorted-wave impulse approximation (DWIA), the transition amplitude formulation of the Faddeev equations due to Alt, Grassberger, and Sandhas (FAGS) and, more recently, a coupled-channels method here referred to as transfer-to-the- continuum (TC). Purpose: Our goal is to compare the momentum distributions calculated with the DWIA and TC models for the same reactions, using whenever possible the same inputs (e.g., distorting potential). A comparison with already published results for the FAGS formalism is performed as well. Method: We choose the 15C(p ,p n )14C reaction at an incident energy of 420 MeV/u, which has been previously studied with the FAGS formalism. The knocked-out neutron is assumed to be in a 2 s single-particle orbital. Longitudinal and transverse momentum distributions are calculated for different assumed separation energies. Results: For all cases considered, we find a very good agreement between DWIA and TC results. The energy dependence of the distorting optical potentials is found to affect in a modest way the shape and magnitude of the momentum distributions. Moreover, when relativistic kinematics corrections are omitted, our calculations reproduce remarkably well the FAGS result. Conclusions: The results found in this work provide confidence on the consistency and accuracy of the DWIA and TC models for analyzing momentum distributions for (p ,p n ) reactions at intermediate energies.

15 CFR 8c.60 - Communications.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 1 2011-01-01 2011-01-01 false Communications. 8c.60 Section 8c.60 Commerce and Foreign Trade Office of the Secretary of Commerce ENFORCEMENT OF NONDISCRIMINATION ON THE... Communications. (a) The agency shall take appropriate steps to ensure effective communication with applicants...

15 CFR 8c.60 - Communications.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 15 Commerce and Foreign Trade 1 2013-01-01 2013-01-01 false Communications. 8c.60 Section 8c.60 Commerce and Foreign Trade Office of the Secretary of Commerce ENFORCEMENT OF NONDISCRIMINATION ON THE... Communications. (a) The agency shall take appropriate steps to ensure effective communication with applicants...

Does fertilizer (N15P15K15) amendment enhance phytoremediation of petroleum-polluted aquatic ecosystem in the presence of water hyacinth (Eichhornia crassipes [Mart.] Solms)?

PubMed

Ndimele, Prince Emeka; Jenyo-Oni, Adetola; Chukwuka, Kanayo S; Ndimele, Chinatu Charity; Ayodele, Ibukunoluwa Augustine

2015-01-01

This study investigated the effects of inorganic fertilizer (N15P15K15) amendments on crude oil uptake by water hyacinth. Experimental units (water hyacinth grown in fresh water) were spiked with 0, 20, 40 and 60 mg/L crude oil. After 24 h, they were randomly assigned fertilizer (N15P15K15) at three different concentrations; 0, 6 and 10 mg/L. Crude oil degradation and absorption were determined by measuring total petroleum hydrocarbon (TPH) in the water column and water hyacinth, respectively. The measurements were taken monthly for six months (February-August 2010). The results showed that TPH concentration in the water column in the treatment amended at 6 mg/L (0.30 ± 0.01 mg/L) was significantly lower (p < .05) than the treatment amended at 10 mg/L (0.76 ± 0.15 mg/L) but was similar to the control (0.33 ± 0.03 mg/L). The water hyacinth in the control (phytoremediation) absorbed significantly higher (p < .05) TPH than the fertilizer-amended treatments. The first-order kinetic model gave a better description of the degradation of petroleum hydrocarbons. The study showed that phytoremediation of crude oil by water hyacinth and biostimulation with fertilizer (N15P15K15) is possible.

17 CFR 240.15c1-2 - Fraud and misrepresentation.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Fraud and misrepresentation. 240.15c1-2 Section 240.15c1-2 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-2 Fraud and...

Complete Measurement of Stable Isotopes in N2O (δ15N, δ15Nα, δ15Nβ, δ18O, δ17O) Using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS)

NASA Astrophysics Data System (ADS)

Leen, J. B.; Gupta, M.

2014-12-01

Nitrate contamination in water is a worldwide environmental problem and source apportionment is critical to managing nitrate pollution. Fractionation caused by physical, chemical and biological processes alters the isotope ratios of nitrates (15N/14N, 18O/16O and 17O/16O) and biochemical nitrification and denitrification impart different intramolecular site preference (15N14NO vs. 14N15NO). Additionally, atmospheric nitrate is anomalously enriched in 17O compared to other nitrate sources. The anomaly (Δ17O) is conserved during fractionation processes, providing a tracer of atmospheric nitrate. All of these effects can be used to apportion nitrate in soil. Current technology for measuring nitrate isotopes is complicated and costly - it involves conversion of nitrate to nitrous oxide (N2O), purification, preconcentration and measurement by isotope ratio mass spectrometer (IRMS). Site specific measurements require a custom IRMS. There is a pressing need to make this measurement simpler and more accessible. Los Gatos Research has developed a next generation mid-infrared Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) analyzer to quantify all stable isotope ratios of N2O (δ15N, δ15Nα, δ15Nβ, δ18O, δ17O). We present the latest performance data demonstrating the precision and accuracy of the OA-ICOS based measurement. At an N2O concentration of 322 ppb, the analyzer quantifies [N2O], δ15N, δ15Na, δ15Nb, and δ18O with a precision of ±0.05 ppb, ±0.4 ‰, ±0.45 ‰, and ±0.6 ‰, and ±0.8 ‰ respectively (1σ, 100s; 1σ, 1000s for δ18O). Measurements of gas standards demonstrate accuracy better than ±1 ‰ for isotope ratios over a wide dynamic range (200 - 100,000 ppb). The measurement of δ17O requires a higher concentration (1 - 50 ppm), easily obtainable through conversion of nitrates in water. For 10 ppm of N2O, the instrument achieves a δ17O precision of ±0.05 ‰ (1σ, 1000s). This performance is sufficient to quantify atmospheric

A new organic reference material, L-glutamic acid, USGS41a, for δ13C and δ15N measurements − a replacement for USGS41

USGS Publications Warehouse

Qi, Haiping; Coplen, Tyler B.; Mroczkowski, Stanley J.; Brand, Willi A.; Brandes, Lauren; Geilmann, Heike; Schimmelmann, Arndt

2016-01-01

RationaleThe widely used l-glutamic acid isotopic reference material USGS41, enriched in both 13C and 15N, is nearly exhausted. A new material, USGS41a, has been prepared as a replacement for USGS41.MethodsUSGS41a was prepared by dissolving analytical grade l-glutamic acid enriched in 13C and 15N together with l-glutamic acid of normal isotopic composition. The δ13C and δ15N values of USGS41a were directly or indirectly normalized with the international reference materials NBS 19 calcium carbonate (δ13CVPDB = +1.95 mUr, where milliurey = 0.001 = 1 ‰), LSVEC lithium carbonate (δ13CVPDB = −46.6 mUr), and IAEA-N-1 ammonium sulfate (δ15NAir = +0.43 mUr) and USGS32 potassium nitrate (δ15N = +180 mUr exactly) by on-line combustion, continuous-flow isotope-ratio mass spectrometry, and off-line dual-inlet isotope-ratio mass spectrometry.ResultsUSGS41a is isotopically homogeneous; the reproducibility of δ13C and δ15N is better than 0.07 mUr and 0.09 mUr, respectively, in 200-μg amounts. It has a δ13C value of +36.55 mUr relative to VPDB and a δ15N value of +47.55 mUr relative to N2 in air. USGS41 was found to be hydroscopic, probably due to the presence of pyroglutamic acid. Experimental results indicate that the chemical purity of USGS41a is substantially better than that of USGS41.ConclusionsThe new isotopic reference material USGS41a can be used with USGS40 (having a δ13CVPDB value of −26.39 mUr and a δ15NAir value of −4.52 mUr) for (i) analyzing local laboratory isotopic reference materials, and (ii) quantifying drift with time, mass-dependent isotopic fractionation, and isotope-ratio-scale contraction for isotopic analysis of biological and organic materials. Published in 2016. This article is a U.S. Government work and is in the public domain in the USA.

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

PubMed

Junghans, Peter

2013-01-01

After oral administration of [(15)N2]urea (1.5 mmol, 95 atom% (15)N), we found that breath N2 was significantly (15)N-labelled. The result suggests that molecular nitrogen in breath must be partly produced endogenously. Based on a metabolic model, the endogenous N2 production was estimated to be 0.40±0.25 mmol kg(-1) d(-1) or 2.9±1.8 % of the total (urinary and faecal) N excretion in fasted healthy subjects (n=4). In patients infected with Helicobacter pylori (n=5), the endogenous N2 production was increased to 1.24±0.59 mmol kg(-1) d(-1) or 9.0±4.3 % of the total N excretion compared to the healthy controls (p<0.05). We conclude that N balance and gas exchange measurements may be affected by endogenously produced nitrogen, especially in metabolic situations with elevated nitrosation, for instance in oxidative and nitrosative stress-related diseases such as H. pylori infections.

Iron-Rhodium and Iron-Iridium Mixed-Metal Nitrido-Carbonyl Clusters. Synthesis, Characterization, Redox Properties, and Solid-State Structure of the Octahedral Clusters [Fe(5)RhN(CO)(15)](2)(-), [Fe(5)IrN(CO)(15)](2)(-), and [Fe(4)Rh(2)N(CO)(15)](-). Infrared and Nuclear Magnetic Resonance Spectroscopic Studies on the Interstitial Nitride.

PubMed

Della Pergola, Roberto; Cinquantini, Arnaldo; Diana, Eliano; Garlaschelli, Luigi; Laschi, Franco; Luzzini, Paola; Manassero, Mario; Repossi, Andrea; Sansoni, Mirella; Stanghellini, Pier Luigi; Zanello, Piero

1997-08-13

The cluster [Fe(5)RhN(CO)(15)](2)(-) was synthesized in 40% yield from [Fe(4)N(CO)(12)](-) and [Rh(CO)(4)](-) in refluxing tetrahydrofuran, whereas the analogous anion [Fe(5)IrN(CO)(15)](2)(-) was prepared in CH(3)CN at room temperature from [Fe(6)N(CO)(15)](3)(-) and [Ir(C(8)H(14))(2)Cl](2); the yields are higher than 60%. The monoanion [Fe(4)Rh(2)N(CO)(15)](-) was obtained in 70% yield from [Fe(5)RhN(CO)(15)](2)(-) and hydrated RhCl(3). The solid-state structures of the three anions were determined on their [PPh(4)](+) salts: the six metal atoms are arranged in octahedral cages and are coordinated to 3 edge-bridging and 12 terminal carbonyl ligands and to a &mgr;(6)-N ligand. The Rh and Ir atoms have less terminal COs than Fe, in order to equalize the excess electrons at the d(9) metal centers. The two rhodium atoms in [Fe(4)Rh(2)N(CO)(15)](-) are directly bound. The (15)N NMR spectra of the three compounds have been recorded; the signals of the nitride ligands were found at delta = 514 ppm for the dianions and 470 ppm for [Fe(4)Rh(2)N(CO)(15)](-); any group 9 atom shifts the resonance of nitrogen to higher fields. The coupling constants J((15)N-(103)Rh) are 8-9 Hz. The vibrational patterns of the metal cores have been interpreted on the basis of an idealized M(6) octahedral arrangement, subsequently modified by the perturbations given by different atomic masses and M-M stretching force constants. The motions of the nitrogen are related to the idealized symmetry of the cage; the M-N force constant values depend on the type of metal and on the charge of the anion. The dianions [Fe(5)MN(CO)(15)](2)(-) can be electrochemically oxidized at -20 degrees C to their short-lived monoanions, which can be characterized by EPR spectroscopy. In contrast, the cluster [Fe(4)Rh(2)N(CO)(15)](-) undergoes a single-step 2-electron reduction to the partially stable trianion [Fe(4)Rh(2)N(CO)(15)](3)(-), which was also characterized by EPR spectroscopy. The Fe-Rh nitride clusters are

15N nuclear magnetic resonance studies on the tautomerism of 8-hydroxy-2'-deoxyguanosine, 8-hydroxyguanosine, and other C8-substituted guanine nucleosides.

PubMed

Cho, B P; Kadlubar, F F; Culp, S J; Evans, F E

1990-01-01

The favored tautomeric and ionic structures were examined for the oxidative DNA damage adduct 8-hydroxy-2'-deoxyguanosine and its RNA analogue 8-hydroxyguanosine by 15N NMR spectroscopy. In addition, 15N chemical shifts and coupling constants from 13 different guanine nucleosides, including a wide variety of C8 substitutions (OH, SH, Br, OCH2C6H5, OCH3, SCH3, and SO2CH3), have been analyzed with respect to their tautomeric structures. A -98.5-Hz proton-nitrogen coupling constant observed for the N7 resonance of 8-hydroxyguanosine in dimethyl sulfoxide was evidence for 8-keto substitution, which is contrary to the structure implied by the generally used nomenclature. The pH dependence of 15N NMR spectra of 8-hydroxyguanosine in aqueous solution showed downfield shifts of the N1 and N7 resonances that were greater than 50 ppm, which indicated the conversion from a neutral 6,8-diketo to a 6-enolate-8-keto (pKa1 = 8.6) and finally to a 6,8-dienolate structure (pKa2 = 11.7). There was no evidence of an 8-enol substituent in the absence of ionization. It is proposed that the syn conformation of these oxidized bases in duplex DNA and RNA can be further stabilized by abnormal hydrogen bonding or mispairing that involves N7-H. The combined data show that 15N NMR is a sensitive probe to examine tautomerism of the guanine ring system. The analysis indicates that the change from a single to a double bond for the C8 substituent, and the accompanying removal of the normal double bond between N7 and C8 on the imidazole ring system, has no detectable effect on the tautomerism at the N1-O6 site of the pyrimidine ring system for both the 8-keto and 8-thio substitutions. In addition, large differences in electronegativity of the C8 substituents do not alter the N1-O6 tautomerism.

Studies of an Isolated 15N- 15N Spin Pair. Off-Angle Fast-Sample-Spinning NMR and Self-Consistent-Field Calculations for Diazo Systems

NASA Astrophysics Data System (ADS)

Challoner, Robin; Harris, Robin K.; Tossell, John A.

1997-05-01

An off-magic-angle spinning study of the nonassociated molecular solid, doubly15N-labeled 5-methyl-2-diazobenzenesulphonic acid hydrochloride (I) is reported. The validity of the off-magic-angle spinning approach under fast-spinning conditions is verified by average Hamiltonian theory. Ab initio SCF calculations were performed on the simpler molecule, C6H5N2+, to provide the shielding parameters, the dipolar coupling between the two nitrogen nuclei, and the electric field gradient existing at both the α-nitrogen and β-nitrogen sites. The calculated values are in good agreement with the shielding and effective dipolar coupling data elucidated in the present investigation, and with a previous study of the two singly15N-labeled isotopomers in which information concerning the electric field gradient at the α and β sites was deduced.

Stable isotope composition (δ(13)C and δ(15)N values) of slime molds: placing bacterivorous soil protozoans in the food web context.

PubMed

Tiunov, Alexei V; Semenina, Eugenia E; Aleksandrova, Alina V; Tsurikov, Sergey M; Anichkin, Alexander E; Novozhilov, Yuri K

2015-08-30

Data on the bulk stable isotope composition of soil bacteria and bacterivorous soil animals are required to estimate the nutrient and energy fluxes via bacterial channels within detrital food webs. We measured the isotopic composition of slime molds (Myxogastria, Amoebozoa), a group of soil protozoans forming macroscopic spore-bearing fruiting bodies. An analysis of largely bacterivorous slime molds can provide information on the bulk stable isotope composition of soil bacteria. Fruiting bodies of slime molds were collected in a monsoon tropical forest of Cat Tien National Park, Vietnam, and analyzed by continuous-flow isotope ratio mass spectrometry. Prior to stable isotope analysis, carbonates were removed from a subset of samples by acidification. To estimate the trophic position of slime molds, their δ(13) C and δ(15) N values were compared with those of plant debris, soil, microbial destructors (litter-decomposing, humus-decomposing, and ectomycorrhizal fungi) and members of higher trophic levels (oribatid mites, termites, predatory macroinvertebrates). Eight species of slime molds represented by at least three independent samples were 3-6‰ enriched in (13) C and (15) N relative to plant litter. A small but significant difference in the δ(13) C and δ(15) N values suggests that different species of myxomycetes can differ in feeding behavior. The slime molds were enriched in (15) N compared with litter-decomposing fungi, and depleted in (15) N compared with mycorrhizal or humus-decomposing fungi. Slime mold sporocarps and plasmodia largely overlapped with oribatid mites in the isotopic bi-plot, but were depleted in (15) N compared with predatory invertebrates and humiphagous termites. A comparison with reference groups of soil organisms suggests strong trophic links of slime molds to saprotrophic microorganisms which decompose plant litter, but not to humus-decomposing microorganisms or to mycorrhizal fungi. Under the assumption that slime molds are

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.

The molecular core in G34.3 + 0.2 - Millimeter interferometric observations of HCO(+), H(C-13)N, H(C-15)N, and SO

NASA Technical Reports Server (NTRS)

Carral, Patricia; Welch, William J.

1992-01-01

This study presents high-resolution observations of the molecular core in the star-forming region G34.3 + 0.2. Maps at 6-arcsec resolution of emission and absorption of the J = 1 - 0 transitions of HCO(+), H (C-13)N, H(C-15)N, and of the 2(2) - 1(1) transition of SO were obtained in addition to a map of the 3.4-mm continuum emission from the compact H II component. The HCL(+) emission toward G34.3 + 0.2 traces a warm molecular core about 0.9 pc in size. Emission from H (C-13)N is detected over about 0.3 pc. The cometary H II region lies near the edge of the molecular core. The blueshift of the radio recombination lines with respect to the molecular emission suggests that gas from the H II region is accelerated in a champagne flow caused by a steep gradient in the ambient gas density.

Biosynthesis of agmatine in isolated mitochondria and perfused rat liver: studies with 15N-labelled arginine

PubMed Central

2005-01-01

An important but unresolved question is whether mammalian mitochondria metabolize arginine to agmatine by the ADC (arginine decarboxylase) reaction. 15N-labelled arginine was used as a precursor to address this question and to determine the flux through the ADC reaction in isolated mitochondria obtained from rat liver. In addition, liver perfusion system was used to examine a possible action of insulin, glucagon or cAMP on a flux through the ADC reaction. In mitochondria and liver perfusion, 15N-labelled agmatine was generated from external 15N-labelled arginine. The production of 15N-labelled agmatine was time- and dose-dependent. The time-course of [U-15N4]agmatine formation from 2 mM [U-15N4]arginine was best fitted to a one-phase exponential curve with a production rate of approx. 29 pmol·min−1·(mg of protein)−1. Experiments with an increasing concentration (0– 40 mM) of [guanidino-15N2]arginine showed a Michaelis constant Km for arginine of 46 mM and a Vmax of 3.7 nmol·min−1·(mg of protein)−1 for flux through the ADC reaction. Experiments with broken mitochondria showed little changes in Vmax or Km values, suggesting that mitochondrial arginine uptake had little effect on the observed Vmax or Km values. Experiments with liver perfusion demonstrated that over 95% of the effluent agmatine was derived from perfusate [guanidino-15N2]arginine regardless of the experimental condition. However, the output of 15N-labelled agmatine (nmol·min−1·g−1) increased by approx. 2-fold (P<0.05) in perfusions with cAMP. The findings of the present study provide compelling evidence that mitochondrial ADC is present in the rat liver, and suggest that cAMP may stimulate flux through this pathway. PMID:15656789

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

NASA Astrophysics Data System (ADS)

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

2011-01-01

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

NMR 1H,13C, 15N backbone and 13C side chain resonance assignment of the G12C mutant of human K-Ras bound to GDP.

PubMed

Sharma, Alok K; Lee, Seung-Joo; Rigby, Alan C; Townson, Sharon A

2018-05-02

K-Ras is a key driver of oncogenesis, accounting for approximately 80% of Ras-driven human cancers. The small GTPase cycles between an inactive, GDP-bound and an active, GTP-bound state, regulated by guanine nucleotide exchange factors and GTPase activating proteins, respectively. Activated K-Ras regulates cell proliferation, differentiation and survival by signaling through several effector pathways, including Raf-MAPK. Oncogenic mutations that impair the GTPase activity of K-Ras result in a hyperactivated state, leading to uncontrolled cellular proliferation and tumorogenesis. A cysteine mutation at glycine 12 is commonly found in K-Ras associated cancers, and has become a recent focus for therapeutic intervention. We report here 1 H N, 15 N, and 13 C resonance assignments for the 19.3 kDa (aa 1-169) human K-Ras protein harboring an oncogenic G12C mutation in the GDP-bound form (K-RAS G12C-GDP ), using heteronuclear, multidimensional NMR spectroscopy. Backbone 1 H- 15 N correlations have been assigned for all non-proline residues, except for the first methionine residue.

Results from the BRACE 1.5 study: Climate change impacts of 1.5 C and 2 C warming

NASA Astrophysics Data System (ADS)

O'Neill, B. C.; Anderson, B.; Monaghan, A. J.; Ren, X.; Sanderson, B.; Tebaldi, C.

2017-12-01

In 2015, 195 countries negotiated the Paris Agreement on climate change, which set long-term goals of limiting global mean warming to well below 2 C and possibly 1.5 C. This event stimulated substantial scientific interest in climate outcomes and impacts on society associated with those levels of warming. Recently, the first set of global climate model simulations explicitly designed to meet those targets were undertaken with the Community Earth System Model (CESM) for use by the research community (Sanderson et al, accepted). The BRACE 1.5 project models societal impacts from these climate outcomes, combined with assumptions about future socioeconomic conditions according to the Shared Socioeconomic Pathways. These analyses build on a recently completed study of the Benefits of Reduced Anthropogenic Climate changE (BRACE), published as a set of 20 papers in Climatic Change, which examined the difference in impacts between two higher scenarios resulting in about 2.5 C and 3.7 C warming by late this century. BRACE 1.5 consists of a set of six papers to be submitted to a special collection in Environmental Research Letters that takes a similar approach but focuses on impacts at 1.5 and 2 C warming. We ask whether impacts differ substantially between the two climate scenarios, accounting for uncertainty in climate outcomes through the use of initial condition ensembles of CESM simulations, and in societal conditions by using alternative SSP-based development pathways. Impact assessment focuses on the health and agricultural sectors; modeling approaches include the use of a global mutli-region CGE model for economic analysis, both a process-based and an empirical crop model, a model of spatial population change, a model of climatic suitability for the aedes aegypti mosquito, and an epidemiological model of heat-related mortality. A methodological analysis also evaluates the use of climate model emulation techniques for providing climate information sufficient to

Doubly 15N-substituted diazenylium: THz laboratory spectra and fractionation models

NASA Astrophysics Data System (ADS)

Dore, L.; Bizzocchi, L.; Wirström, E. S.; Degli Esposti, C.; Tamassia, F.; Charnley, S. B.

2017-07-01

Context. Isotopic fractionation in dense molecular cores has been suggested as a possible origin of large 14N/15N ratio variations in solar system materials. While chemical models can explain some observed variations with different fractionation patterns for molecules with -NH or -CN functional groups, they fail to reproduce the observed ratios in diazenylium (N2H+). Aims: Observations of doubly 15N-substituted species could provide important constraints and insights for theoretical chemical models of isotopic fractionation. However, spectroscopic data are very scarce. Methods: The rotational spectra of the fully 15N-substituted isopologues of the diazenylium ion, 15N2H+ and 15N2D+, have been investigated in the laboratory well into the THz region by using a source-modulation microwave spectrometer equipped with a negative glow discharge cell. An extended chemical reaction network has been used to estimate what ranges of 15N fractionation in doubly 15N-substituted species could be expected in the interstellar medium (ISM). Results: For each isotopologue of the H- and D-containing pair, nine rotational transitions were accurately measured in the frequency region 88 GHz-1.2 THz. The analysis of the spectrum provided very precise rest frequencies at millimeter and sub-millimeter wavelengths, useful for the radioastronomical identification of the rotational lines of 15N2H+ and 15N2D+ in the ISM.

Comparison of halo of 11Be, 15C, and 19C

NASA Astrophysics Data System (ADS)

Kharab, R.; Kumar, R.; Singh, P.; Sharma, H. C.

2007-12-01

We have compared the halo of 11Be, 15C, and 19C nuclei by analyzing the one-neutron stripping reaction data on the Be target at 60-, 54-, and 57-MeV/ A beam energies, respectively, within the framework of the eikonal approximation approach. The determination of effective range through the comparison of the total cross section data and prediction has revealed that the halo of 19C is the well developed, while that of 15C is the least and that of 11Be lies in between these two. The longitudinal momentum distribution data also strengthen these observations.

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

Vokhshoori, Natasha L; McCarthy, Matthew D

2014-01-01

We explored δ(15)N 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 δ(15)N gradients in the California Upwelling Ecosystem (CUE), determining bulk δ(15)N 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 δ(15)N values showed a strong linear trend with latitude, increasing from North to South (from ∼ 7‰ to ∼ 12‰, R(2) = 0.759). In contrast, CSI-AA trophic position estimates showed no correlation with latitude. The δ(15)N trend is therefore most consistent with a baseline δ(15)N gradient, likely due to the mixing of two source waters: low δ(15)N nitrate from the southward flowing surface California Current, and the northward transport of the California Undercurrent (CUC), with (15)N-enriched nitrate. This interpretation is strongly supported by a similar linear gradient in δ(15)N values of phenylalanine (δ(15)NPhe), the best AA proxy for baseline δ(15)N values. We hypothesize δ(15)N(Phe) values in intertidal mussels can approximate annual integrated δ(15)N values of coastal phytoplankton primary production. We therefore used δ(15)N(Phe) values to generate the first compound-specific nitrogen isoscape for the coastal Northeast Pacific, which indicates a remarkably linear gradient in coastal primary production δ(15)N values. We propose that δ(15)N(Phe) isoscapes derived from filter feeders can directly characterize baseline δ(15)N 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.

15 CFR 8c.10 - Self-evaluation.

Code of Federal Regulations, 2014 CFR

2014-01-01

... handicaps or organizations representing individuals with handicaps, to participate in the self-evaluation... 15 Commerce and Foreign Trade 1 2014-01-01 2014-01-01 false Self-evaluation. 8c.10 Section 8c.10... BASIS OF HANDICAP IN PROGRAMS OR ACTIVITIES CONDUCTED BY THE DEPARTMENT OF COMMERCE § 8c.10 Self...

Stable nitrogen and carbon isotope (δ 15N and δ 13C) variability in shallow tropical Pacific soft coral and black coral taxa and implications for paleoceanographic reconstructions

NASA Astrophysics Data System (ADS)

Williams, Branwen; Grottoli, Andréa G.

2010-09-01

Soft corals and black corals are useful proxy tools for paleoceanographic reconstructions. However, most work has focused on deep-water taxa and few studies have used these corals as proxy organisms in shallow water (<200 m). To facilitate the use of stable nitrogen and carbon isotope (δ 15N and δ 13C) records from shallow-water soft coral and black coral taxa for paleoceanographic reconstructions, quantification of the inherent variability in skeletal isotope values between sites, across depth, and among taxa is needed. Here, skeletal δ 15N and δ 13C values were measured in multiple colonies from eleven genera of soft corals and two genera of black corals from across a depth transect (5-105 m) at two sites in Palau located in the tropical western Pacific Ocean. Overall, no difference in skeletal δ 15N and δ 13C values between sites was present. Skeletal δ 15N values significantly increased and δ 13C values decreased with depth. This is consistent with changes in isotope values of suspended particulate organic matter (POM) across the photic zone, suggesting that the primary food source to these corals is suspended POM and that the stable isotopic composition of POM controls the skeletal isotopic composition of these corals. Thus, to compare the isotope records of corals collected across a depth range in the photic zone, first order depth corrections of -0.013‰ m -1 and +0.023‰ m -1 are recommended for δ 15N and δ 13C, respectively. Average depth-corrected δ 15N values were similar between black corals and soft corals, indicating that corals in these orders feed at a similar trophic level. In contrast, average depth-corrected δ 13C values of black corals were significantly lower than that of soft corals, potentially resulting from metabolic processes associated with differing skeletal compositions among the orders (i.e., gorgonin vs. chitin based). Thus, a correction of +1.0‰ is recommended for black corals when comparing their δ 13C-based proxy

15N isotopic analyses: a powerful tool to establish links between seized 3,4-methylenedioxymethamphetamine (MDMA) tablets.

PubMed

Palhol, Fabien; Lamoureux, Catherine; Naulet, Norbert

2003-06-01

In this study the (15)N/(14)N isotopic ratios of 43 samples of 3,4-methylenedioxymethamphetamine (MDMA) samples were measured using Gas Chromatography-Combustion-Isotope-Ratio Mass Spectrometry (GC-C-IRMS). The results show a large discrimination between samples with a range of delta(15)N values between -16 and +19 per thousand. Comparison between delta(15)N values and other physical and chemical parameters shows a strong relationship between delta(15)N and brand logo or composition. Thus, it could be assumed that tablets from different seizures probably originated from the same clandestine manufacturing source. Hence, (15)N isotopic parameters provide an important additional tool to establish common origins between seizures of clandestine synthetic drugs.

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

NASA Astrophysics Data System (ADS)

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

2015-08-01

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

17 CFR 240.15c6-1 - Settlement cycle.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Settlement cycle. 240.15c6-1... Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c6-1 Settlement cycle. (a) Except... provides for payment of funds and delivery of securities later than the third business day after the date...

The crystal structure of the mixed-layer Aurivillius phase Bi 5Ti 1.5W 1.5O 15

NASA Astrophysics Data System (ADS)

Tellier, J.; Boullay, Ph.; Créon, N.; Mercurio, D.

2005-09-01

The crystal structure of the 1+2 mixed-layer Aurivillius phase Bi 5Ti 1.5W 1.5O 15 (SG I2cm n o 46: -cba, Z=4, a=5.4092(3) Å, b=5.3843(3) Å and c=41.529(3) Å) consisting of the ordered intergrowth of one and two octahedra thick perovskite-type blocks separated by [Bi 2O 2] 2+ slabs is reported. Supported by an electron diffraction investigation and, using the Rietveld analysis, it is shown that this compound should be described using a I-centering lattice in agreement with the generalised structural model of the Aurivillius type compounds recently presented by the authors. The structure of this Bi 5Ti 1.5W 1.5O 15 phase is analyzed in comparison with the related simple members (Bi 2WO 6 and Bi 3Ti 1.5W 0.5O 9). The crystal structure of Bi 3Ti 1.5W 0.5O 9 is also reported.

Neutron capture cross section of {sup 14}C of astrophysical interest studied by Coulomb breakup of {sup 15}C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, T.; Fukuda, N.; Aoi, N.

2009-03-15

The neutron capture reaction on {sup 14}C leading to the {sup 15}C ground state, which plays an important role in various nucleosynthesis processes, has been studied using the Coulomb breakup of {sup 15}C on a Pb target at 68 MeV/nucleon. The breakup cross section has been converted into the energy-dependent neutron capture cross section using the principle of detailed balance. The energy spectrum shows typical p-wave neutron capture characteristics, which is explained by the fact that the ground state of {sup 15}C possesses a strong single-particle s-wave component and a moderate-sized neutron halo structure. The capture cross section for themore » {sup 14}C(n,{gamma}){sup 15}C reaction derived from the present experiment has been found to be consistent with the most recent data, directly measured using a {sup 14}C target. This result assures the validity of the Coulomb breakup method in deriving the neutron capture cross section for neutron-rich nuclei.« less

17 CFR 240.15c1-8 - Sales at the market.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 17 Commodity and Securities Exchanges 4 2014-04-01 2014-04-01 false Sales at the market. 240.15c1-8 Section 240.15c1-8 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-8 Sales at the market...

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

PubMed Central

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

2014-01-01

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

1H, 13C and 15N assignment of the C-terminal domain of GNA2132 from Neisseria meningitidis

PubMed Central

Esposito, Veronica; Musi, Valeria; Veggi, Daniele; Pizza, Mariagrazia

2010-01-01

GNA2132 (Genome-derived Neisseria Antigen 2132) is a surface-exposed lipoprotein discovered by reverse vaccinology and expressed by genetically diverse Neisseria meningitidis strains (Pizza et al. 2000). The protein induces bactericidal antibodies against most strains of Meningococccus and has been included in a multivalent recombinant vaccine against N. meningitidis serogroup B. Structure determination of GNA2132 is important for understanding the antigenic properties of the protein in view of increased efficiency vaccine development. We report practically complete 1H, 13C and 15N assignment of the detectable spectrum of a highly conserved C-terminal region of GNA2132 (residues 245–427) in micellar solution, a medium used to improve the spectral quality. The first 32 residues of our construct up to residue 277 were not visible in the spectrum, presumably because of line broadening due to solvent and/or conformational exchange. Secondary structure predictions based on chemical shift information indicate the presence of an all β-protein with eight β strands. PMID:20300890

1H, 13C and 15N assignment of the C-terminal domain of GNA2132 from Neisseria meningitidis.

PubMed

Esposito, Veronica; Musi, Valeria; Veggi, Daniele; Pastore, Annalisa; Pizza, Mariagrazia

2010-04-01

GNA2132 (Genome-derived Neisseria Antigen 2132) is a surface-exposed lipoprotein discovered by reverse vaccinology and expressed by genetically diverse Neisseria meningitidis strains (Pizza et al. 2000). The protein induces bactericidal antibodies against most strains of Meningococccus and has been included in a multivalent recombinant vaccine against N. meningitidis serogroup B. Structure determination of GNA2132 is important for understanding the antigenic properties of the protein in view of increased efficiency vaccine development. We report practically complete (1)H, (13)C and (15)N assignment of the detectable spectrum of a highly conserved C-terminal region of GNA2132 (residues 245-427) in micellar solution, a medium used to improve the spectral quality. The first 32 residues of our construct up to residue 277 were not visible in the spectrum, presumably because of line broadening due to solvent and/or conformational exchange. Secondary structure predictions based on chemical shift information indicate the presence of an all beta-protein with eight beta strands.

Deuterium isotope effects on 13C and 15N chemical shifts of intramolecularly hydrogen-bonded enaminocarbonyl derivatives of Meldrum’s and Tetronic acid

NASA Astrophysics Data System (ADS)

Ullah, Saif; Zhang, Wei; Hansen, Poul Erik

2010-07-01

Secondary deuterium isotope effects on 13C and 15N nuclear shieldings in a series of cyclic enamino-diesters and enamino-esters and acyclic enaminones and enamino-esters have been examined and analysed using NMR and DFT (B3LYP/6-31G(d,p)) methods. One-dimensional and two-dimensional NMR spectra of enaminocarbonyl and their deuterated analogues were recorded in CDCl 3 and CD 2Cl 2 at variable temperatures and assigned. 1JNH coupling constants for the derivatives of Meldrum's and tetronic acids reveal that they exist at the NH-form. It was demonstrated that deuterium isotope effects, for the hydrogen bonded compounds, due to the deuterium substitution at the nitrogen nucleus lead to large one-bond isotope effects at nitrogen, 1Δ 15N(D), and two-bond isotope effects on carbon nuclei, 2ΔC(ND), respectively. A linear correlations exist between 2ΔC(ND) and 1Δ 15N(D) whereas the correlation with δNH is divided into two. A good agreement between the experimentally observed 2ΔC(ND) and calculated dσ 13C/dR NH was obtained. A very good correlation between calculated NH bond lengths and observed NH chemical shifts is found. The observed isotope effects are shown to depend strongly on Resonance Assisted Hydrogen bonding.

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.

Kinetic 15N-isotope effects on algal growth

NASA Astrophysics Data System (ADS)

Andriukonis, Eivydas; Gorokhova, Elena

2017-03-01

Stable isotope labeling is a standard technique for tracing material transfer in molecular, ecological and biogeochemical studies. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism metabolism and growth, which is not consistent with current theoretical and empirical knowledge on kinetic isotope effects. Here, we demonstrate profound changes in growth dynamics of the green alga Raphidocelis subcapitata grown in 15N-enriched media. With increasing 15N concentration (0.37 to 50 at%), the lag phase increased, whereas maximal growth rate and total yield decreased; moreover, there was a negative relationship between the growth and the lag phase across the treatments. The latter suggests that a trade-off between growth rate and the ability to adapt to the high 15N environment may exist. Remarkably, the lag-phase response at 3.5 at% 15N was the shortest and deviated from the overall trend, thus providing partial support to the recently proposed Isotopic Resonance hypothesis, which predicts that certain isotopic composition is particularly favorable for living organisms. These findings confirm the occurrence of KIE in isotopically enriched algae and underline the importance of considering these effects when using stable isotope labeling in field and experimental studies.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hobbie, J.E.; Fry, B.; Larsson, U.

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 Marchmore » 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.« less

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

USGS Publications Warehouse

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

2009-01-01

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

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

USGS Publications Warehouse

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

1987-01-01

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

[Dynamics of amino acid and protein metabolism of laying hens after administration of 15N-labeled wheat protein. 5. Incorporation of 15N into the blood fraction and its amino acids].

PubMed

Gruhn, K; Zander, R; Kirchner, E

1987-09-01

12 colostomized laying hens which received 15N labelled wheat over 4 days were butchered 12 h, 36 h, 60 h and 108 h (3 animals each) after the last 15N application. The intake of 15N excess (15N') from the wheat amounted to 540 mg 15N' during the application period. The 15N' in the blood plasma decreased after the last 15N' application from 0.76 atom-% to 0.55 atom-% after 108 h, the labelling of the corpuscular components at the same measuring points increased from 0.28 to 0.50 atom-% 15N'. 96.6% of the plasma 15N' and 93.8% of that in the corpuscles is precipitable in trichloric acetic acid. The atom-% 15N' of histidine in the total blood remained unchanged in dependence on the butchering time. The 15N amount in lysine and arginine and that in the non-basic amino acids decreased inconsiderably in the period between 12 h and 108 h after the last 15N' wheat feeding.

Arctic sea ice at 1.5 and 2 °C

NASA Astrophysics Data System (ADS)

Screen, James A.

2018-05-01

In the Paris Agreement, nations committed to a more ambitious climate policy target, aiming to limit global warming to 1.5 °C rather than 2 °C above pre-industrial levels. Climate models now show that achieving the 1.5 °C goal would make a big difference for Arctic sea ice.

Glacial to interglacial surface nutrient variations of Bering Deep Basins recorded by δ13C and δ15N of sedimentary organic matter

NASA Astrophysics Data System (ADS)

Nakatsuka, Takeshi; Watanabe, Kazuki; Handa, Nobuhiko; Matsumoto, Eiji; Wada, Eitaro

1995-12-01

Stable carbon and nitrogen isotopic ratios (δ13C and δ15N) of organic matter were measured in three sediment cores from deep basins of the Bering Sea to investigate past changes in surface nutrient conditions. For surface water reconstructions, hemipelagic layers in the cores were distinguished from turbidite layers (on the basis of their sedimentary structures and 14C ages) and analyzed for isotopic studies. Although δ13C profiles may have been affected by diagenesis, both δ15N and δ13C values showed common positive anomalies during the last deglaciation. We explain these anomalies as reflecting suppressed vertical mixing and low nutrient concentrations in surface waters caused by injection of meltwater from alpine glaciers around the Bering Sea. Appendix tables are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington , DC 20009. Document P95-003; $2.50. Payment must accompany order.

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Achtnich, C.; Fernandes, E.; Bollag, J.M.

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 themore » 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.« less

Kinetic commitment in the catalysis of glutamine synthesis by GS1 from Arabidopsis using 14N/15N and solvent isotope effects.

PubMed

Mauve, Caroline; Giraud, Nicolas; Boex-Fontvieille, Edouard R A; Antheaume, Ingrid; Tea, Illa; Tcherkez, Guillaume

2016-11-01

Glutamine synthetase (GS, EC 6.3.1.2) catalyzes the production of glutamine from glutamate, ammonium and ATP. Although being essential in plants for N assimilation and recycling, kinetic commitments and transition states of the reaction have not been clearly established yet. Here, we examined 12 C/ 13 C, 14 N/ 15 N and H 2 O/D 2 O isotope effects in Arabidopsis GS1 catalysis and compared to the prokaryotic (Escherichia coli) enzyme. A 14 N/ 15 N isotope effect ( 15 V/K ≈ 1.015, with respect to substrate NH 4 + ) was observed in the prokaryotic enzyme, indicating that ammonium utilization (deprotonation and/or amidation) was partially rate-limiting. In the plant enzyme, the isotope effect was inverse ( 15 V/K = 0.965), suggesting that the reaction intermediate is involved in an amidation-deamidation equilibrium favoring 15 N. There was no 12 C/ 13 C kinetic isotope effect ( 13 V/K = 1.000), suggesting that the amidation step of the catalytic cycle involves a transition state with minimal alteration of overall force constants at the C-5 carbon. Surprisingly, the solvent isotope effect was found to be inverse, that is, with a higher turn-over rate in heavy water ( D V ≈ 0.5), showing that restructuration of the active site due to displacement of H 2 O by D 2 O facilitates the processing of intermediates. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chace, D.H.

1989-01-01

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

δ15N as a Potential Paleoenvironmental Proxy for Nitrogen Loading in Chesapeake Bay

NASA Astrophysics Data System (ADS)

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

2013-12-01

Stable isotope analysis of Eastern Oyster (Crassostrea virginica) and other mollusk shells from archaeological sites is a useful means of acquiring paleoenvironmental data. Recently, nitrogen isotopes have been identified as a potential new proxy in these shells. δ15N content in mollusk shells is affected by numerous anthropogenic and natural influences and may be used as an environmental proxy for nitrogen loading conditions. Chesapeake Bay is well known for both historic and modern pollution problems from numerous anthropogenic sources, such as fertilizer runoff, sewage discharge, and densely populated land use and serves as an ideal study location for long-term nitrogen loading processes. Longer records of these processes may be recorded in abundant archaeological remains around the bay, however, little is known about the stability of δ15N and %N in shell material over recent geologic time. In this study, 90 archaeological C. virginica shells were collected by the Smithsonian Institution from the Rhode River Estuary within Chesapeake Bay and range in age from ~150 to 3200 years old. Twenty-two modern C. virginica shells were also collected from nearby beds in the bay. All shell samples were subsampled from the resilifer region of the calcitic shell using a hand-held micro drill and were analyzed using EA-IRMS analysis to determine the potential temporal variability of δ15N and %N as well as creating a baseline for ancient nitrogen conditions in the bay area. Modern POM water samples and C. virginica soft tissues were also analyzed in this study to determine the degree of seasonal variation of δ15N and %N in Chesapeake Bay.

On the differences between 1.5oC and 2oC of global warming

NASA Astrophysics Data System (ADS)

King, A.

2017-12-01

The Paris Agreement of 2015 has resulted in a drive to limit global warming to 2oC with an aim for a lower 1.5oC target. It is therefore vital that we understand some of the differences we would expect between these two levels of global warming. My research uses coupled climate model projections to investigate where and for what variables we can differentiate between worlds of 1.5oC and 2oC global warming. I place a particular focus on climate extremes and population exposure to those extremes. I have found that there are perceptible benefits in limiting global warming to 1.5oC as opposed to 2oC through reduced frequency and intensity of heat extremes, both over land and in ocean areas where thermal stress on coral has resulted in bleaching. Differences in high and low precipitation extremes between the 1.5oC and 2oC global warming levels are projected for some regions. I have also examined how "scalable" changes from the 1.5oC to 2oC level are. In areas of the world such as Eastern China I find that changes in anthropogenic aerosol concentrations will influence the level of change projected at 1.5oC and 2oC, such that past warming is likely to be a poor indicator of future changes. Overall, my research finds clear benefits to limiting global warming to 1.5oC relative to higher levels.

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.

15N Abundance of Nodules as an Indicator of N Metabolism in N2-Fixing Plants 1

PubMed Central

Shearer, Georgia; Feldman, Lori; Bryan, Barbara A.; Skeeters, Jerri L.; Kohl, Daniel H.; Amarger, Nöelle; Mariotti, Françoise; Mariotti, André

1982-01-01

This paper expands upon previous reports of 15N elevation in nodules (compared to other tissues) of N2-fixing plants. N2-Fixing nodules of Glycine max (soybeans), Vigna unguiculata (cowpea), Phaseolus vulgaris (common bean), Phaseolus coccineus (scarlet runner bean), Prosopis glandulosa (mesquite), and Olneya tesota (desert ironwood) were enriched in 15N. Nodules of Vicia faba (fava beans), Arachis hypogaea (peanut), Trifolium pratense (red clover), Pisum sativum (pea), Lathyrus sativus (grass pea), Medicago sativa (alfalfa), and Lupinus mutabilis (South American lupine) were not; nor were the nodules of nine species of N2-fixing nonlegumes. The nitrogen of ineffective nodules of soybeans and cowpeas was not enriched in 15N. Thus, 15N elevation in nodules of these plants depends on active N2-fixation. Results obtained so far on the generality of 15N enrichment in N2-fixing nodules suggest that only the nodules of plants which actively fix N2 and which transport allantoin or allantoic acid exhibit 15N enrichment. PMID:16662517

N-15 tracing helps explaining N leaching losses from contrasting forest ecosystems

NASA Astrophysics Data System (ADS)

Staelens, J.; Rütting, T.; Huygens, D.; Müller, C.; Verheyen, K.; Boeckx, P.

2009-04-01

Despite chronically enhanced nitrogen (N) deposition to forest ecosystems in Europe and NE America, considerable N retention by forests has been observed, reducing N leaching losses. Organic and mineral soil layers typically immobilize more N than the aboveground biomass, but it is unclear which factors determine N retention in forest ecoystems. However, this knowledge is crucial to assess the impact of changing anthropogenic N emissions on future N cycling and N loss of forests. For coniferous and deciduous forest stands at comparable sites, it is known that both N deposition onto the forest floor as well as N loss by leaching below the rooting zone are significantly higher in coniferous stands. In addition, the N loss in coniferous stands is often more enhanced than can be explained by the higher N input only. This suggests lower N retention by coniferous stands, and may be related to differences in litter and soil characteristics, microbial activity, and N uptake by plant roots. To test this hypothesis, we studied the effect of forest type on N retention using 15N tracing techniques: a field tracer experiment and a combination of in situ isotope pool dilution and a tracing model. The N dynamics were examined for two adjacent forest stands (pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.)) on a well-drained sandy soil and with a similar stand history, located in a region with high N deposition (Belgium). Input-output N budgets were established by quantifying atmospheric deposition and leaching below the rooting zone, and confirmed the above finding of higher N deposition and disproportionately higher N loss for the pine stand compared to the oak stand. First, the fate of inorganic N within the ecosystems was studied by spraying three pulses of dissolved 15N, either as ammonium or as nitrate, onto the forest floor in 12 plots of 25 m2. The organic and mineral soil layers, tree roots, soil water percolate, ferns, and tree foliage were sampled

The "Speedy" Synthesis of Atom-Specific (15)N Imino/Amido-Labeled RNA.

PubMed

Neuner, Sandro; Santner, Tobias; Kreutz, Christoph; Micura, Ronald

2015-08-10

Although numerous reports on the synthesis of atom-specific (15)N-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 (15)N(1) adenosine and (15)N(1) guanosine amidites, which are the much needed counterparts of the more straightforward-to-achieve (15)N(3) uridine and (15)N(3) cytidine amidites in order to tap full potential of (1)H/(15)N/(15)N-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. © 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

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

PubMed

Ferreira, M João G; García, A; Leonardi, D; Salomon, Claudio J; Lamas, M Celina; Nunes, Teresa G

2015-06-05

(13)C and (15)N solid-state nuclear magnetic resonance (NMR) spectra were recorded from albendazole (ABZ) and from ABZ:β-cyclodextrin, ABZ:methyl-β-cyclodextrin, ABZ:hydroxypropyl-β-cyclodextrin and ABZ:citrate-β-cyclodextrin, which were prepared by the spray-drying technique. ABZ signals were typical of a crystalline solid for the pure drug and of an amorphous compound obtained from ABZ:cyclodextrin samples. Relevant spectral differences were correlated with chemical interaction between ABZ and cyclodextrins. The number and type of complexes revealed a strong dependence on the cyclodextrin group substituent. Solid-state NMR data were consistent with the presence of stable inclusion complexes. Copyright © 2015 Elsevier Ltd. All rights reserved.

17 CFR 240.15c3-1a - Options (Appendix A to 17 CFR 240.15c3-1).

Code of Federal Regulations, 2013 CFR

2013-04-01

... Regulations Under the Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c3-1a... and down) in the current market value of the underlying instrument equal to the percentage... life of the option; and (6) The current term structure of interest rates. (C) The term major market...

17 CFR 240.15c3-1a - Options (Appendix A to 17 CFR 240.15c3-1).

Code of Federal Regulations, 2010 CFR

2010-04-01

... Regulations Under the Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c3-1a... and down) in the current market value of the underlying instrument equal to the percentage... life of the option; and (6) The current term structure of interest rates. (C) The term major market...

17 CFR 240.15c3-1a - Options (Appendix A to 17 CFR 240.15c3-1).

Code of Federal Regulations, 2011 CFR

2011-04-01

... Regulations Under the Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c3-1a... and down) in the current market value of the underlying instrument equal to the percentage... life of the option; and (6) The current term structure of interest rates. (C) The term major market...

Delta(13)C, delta(15)N and delta(2)H isotope ratio mass spectrometry of ephedrine and pseudoephedrine: application to methylamphetamine profiling.

PubMed

Collins, Michael; Cawley, Adam T; Heagney, Aaron C; Kissane, Luke; Robertson, James; Salouros, Helen

2009-07-01

Conventional chemical profiling of methylamphetamine has been used for many years to determine the synthetic route employed and where possible to identify the precursor chemicals used. In this study stable isotope ratio analysis was investigated as a means of determining the origin of the methylamphetamine precursors, ephedrine and pseudoephedrine. Ephedrine and pseudoephedrine may be prepared industrially by several routes. Results are presented for the stable isotope ratios of carbon (delta(13)C), nitrogen (delta(15)N) and hydrogen (delta(2)H) measured in methylamphetamine samples synthesized from ephedrine and pseudoephedrine of known provenance. It is clear from the results that measurement of the delta(13)C, delta(15)N and delta(2)H stable isotope ratios by elemental analyzer/thermal conversion isotope ratio mass spectrometry (EA/TC-IRMS) in high-purity methylamphetamine samples will allow determination of the synthetic source of the ephedrine or pseudoephedrine precursor as being either of a natural, semi-synthetic, or fully synthetic origin. Copyright (c) 2009 Commonwealth of Australia.

δ15N Values in Crassostrea virginica Shells Provides Early Direct Evidence for Nitrogen Loading to Chesapeake Bay

NASA Astrophysics Data System (ADS)

Black, H. D.; Andrus, C. F. T.; Lambert, W. J.; Rick, T. C.; Gillikin, D. P.

2017-03-01

Crassostrea virginica is one of the most common estuarine bivalves in the United States’ east coast and is frequently found in archaeological sites and sub-fossil deposits. Although there have been several sclerochronological studies on stable carbon and oxygen isotopes in the shells of this species, less is known about δ15N values within their shells, which could be a useful paleoenvironmental proxy to assess estuarine nitrogen dynamics. Modern C. virginica samples were collected in Chesapeake Bay for comparison with archaeological shells from nearby sites ranging in age from ~100 to 3,200 years old. Left valves were sampled by milling the hinge area and the resulting powder was analyzed for %N and δ15N values. Comparison of δ15N values between C. virginica shells shows relatively constant values from ~1250 BC to ~1800 AD. After ~1800 AD, there are rapid increases in 15N enrichment in the shells, which continue to increase in value up to the modern shell values. The increase in δ15N values is evidence of early anthropogenic impact in Chesapeake Bay. These results corroborate the observation that coastal nitrogen pollution occurred earlier than the 19th century and support the use of oyster shell δ15N values as a useful environmental proxy.

Seasonal variation in natural abundance of δ13C and 15N in Salicornia brachiata Roxb. populations from a coastal area of India.

PubMed

Chaudhary, Doongar R; Seo, Juyoung; Kang, Hojeong; Rathore, Aditya P; Jha, Bhavanath

2018-05-01

High and fluctuating salinity is characteristic for coastal salt marshes, which strongly affect the physiology of halophytes consequently resulting in changes in stable isotope distribution. The natural abundance of stable isotopes (δ 13 C and δ 15 N) of the halophyte plant Salicornia brachiata and physico-chemical characteristics of soils were analysed in order to investigate the relationship of stable isotope distribution in different populations in a growing period in the coastal area of Gujarat, India. Aboveground and belowground biomass of S. brachiata was collected from six different populations at five times (September 2014, November 2014, January 2015, March 2015 and May 2015). The δ 13 C values in aboveground (-30.8 to -23.6 ‰, average: -26.6 ± 0.4 ‰) and belowground biomass (-30.0 to -23.1 ‰, average: -26.3 ± 0.4 ‰) were similar. The δ 13 C values were positively correlated with soil salinity and Na concentration, and negatively correlated with soil mineral nitrogen. The δ 15 N values of aboveground (6.7-16.1 ‰, average: 9.6 ± 0.4 ‰) were comparatively higher than belowground biomass (5.4-13.2 ‰, average: 7.8 ± 0.3 ‰). The δ 15 N values were negatively correlated with soil available P. We conclude that the variation in δ 13 C values of S. brachiata was possibly caused by soil salinity (associated Na content) and N limitation which demonstrates the potential of δ 13 C as an indicator of stress in plants.

Identifying N fertilizer regime and vegetable production system in tropical Brazil using (15) N natural abundance.

PubMed

Inácio, Caio T; Urquiaga, Segundo; Chalk, Phillip M; Mata, Maria Gabriela F; Souza, Paulo O

2015-12-01

This study was conducted in areas of vegetable production in tropical Brazil, with the objectives of (i) measuring the variation in δ(15)  N in soils, organic N fertilizer sources and lettuce (Lactuca sativa L.) from different farming systems, (ii) measuring whether plant δ(15)  N can differentiate organic versus conventional lettuce and (iii) identifying the factors affecting lettuce δ(15)  N. Samples of soil, lettuce and organic inputs were taken from two organic, one conventional and one hydroponic farm. The two organic farms had different N-sources with δ(15)  N values ranging from 0.0 to +14.9‰ (e.g. leguminous green manure and animal manure compost, respectively), and differed significantly (P < 0.05) in lettuce δ(15)  N (+9.2 ± 1.1‰ and +14.3 ± 1.0‰). Conventional lettuce δ(15)  N (+8.5 ± 2.7‰) differed from hydroponic lettuce δ(15)  N (+4.5 ± 0.2‰) due to manure inputs. The N from leguminous green manure made a small contribution to the N nutrition of lettuce in the multi-N-source organic farm. To differentiate organic versus conventional farms using δ(15)  N the several subsets of mode of fertilization should be considered. Comparisons of δ(15)  N of soil, organic inputs and lettuce allowed a qualitative analysis of the relative importance of different N inputs. © 2015 Society of Chemical Industry.

Resolution enhancement in 13C and 15N magic-angle turning experiments with TPPM decoupling.

PubMed

McGeorge, G; Alderman, D W; Grant, D M

1999-03-01

Many solid-state spectra have been shown to have problems related to the poor proton decoupling of carbon nuclei in methylene groups under conditions of slow magic-angle turning. Two-pulse phase-modulation (TPPM) decoupling during the 2D PHORMAT chemical shift separation experiment is shown to be more effective in comparison to that obtainable at much higher spin rates using conventional CW decoupling. TPPM decoupling can also alleviate similar inadequacies when observing the 15N nucleus, particularly with NH2 groups. This is demonstrated in the 15N resonances of fully labeled l-arginine hydrochloride, where a line narrowing of about a factor of two was observed at moderate rotation rates. This significant advantage was also obtained at turning frequencies as low as 500 Hz. Copyright 1999 Academic Press.

Backbone amide 15N chemical shift tensors report on hydrogen bonding interactions in proteins: A magic angle spinning NMR study.

PubMed

Paramasivam, Sivakumar; Gronenborn, Angela M; Polenova, Tatyana

2018-08-01

Chemical shift tensors (CSTs) are an exquisite probe of local geometric and electronic structure. 15 N CST are very sensitive to hydrogen bonding, yet they have been reported for very few proteins to date. Here we present experimental results and statistical analysis of backbone amide 15 N CSTs for 100 residues of four proteins, two E. coli thioredoxin reassemblies (1-73-(U- 13 C, 15 N)/74-108-(U- 15 N) and 1-73-(U- 15 N)/74-108-(U- 13 C, 15 N)), dynein light chain 8 LC8, and CAP-Gly domain of the mammalian dynactin. The 15 N CSTs were measured by a symmetry-based CSA recoupling method, ROCSA. Our results show that the principal component δ 11 is very sensitive to the presence of hydrogen bonding interactions due to its unique orientation in the molecular frame. The downfield chemical shift change of backbone amide nitrogen nuclei with increasing hydrogen bond strength is manifested in the negative correlation of the principal components with hydrogen bond distance for both α-helical and β-sheet secondary structure elements. Our findings highlight the potential for the use of 15 N CSTs in protein structure refinement. Copyright © 2018 Elsevier Inc. All rights reserved.

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. Copyright (c) 2009 Elsevier Inc. All rights reserved.

δ13C and δ15N Values of Sediment-trap Particles in the Japan and Yamato Basins and Comparison with the Core-top Values in the East/Japan Sea

NASA Astrophysics Data System (ADS)

Khim, Boo-Keun; Otosaka, Shigeyoshi; Park, Kyung-Ae; Noriki, Shinichiro

2018-03-01

Investigation of sediment-trap deployments in the East/Japan Sea (EJS) showed that distinct seasonal variations in particulate organic carbon (POC) fluxes of intermediate-water sediment-traps clearly corresponded to changes in chlorophyll a concentrations estimated from SeaWiFS data. The prominent high POC flux periods (e.g., March) were strongly correlated with the enhanced surface-water phytoplankton blooms. Deep-water sedimenttraps exhibited similar variation patterns to intermediate-water sediment-traps. However, their total flux and POC flux were higher than those of intermediate-water sediment-traps during some months (e.g., April and May), indicating the lateral delivery of some particles to the deep-water sediment-traps. Distinct seasonal δ13C and δ15N variations in settling particles of the intermediate-water sediment-traps were observed, strongly supporting the notion of seasonal primary production. Seasonal variations in δ13C and δ15N values from the deep-water sediment-traps were similar to those of the intermediate-water sediment-traps. However, the difference in δ13C and δ15N values between the intermediate-water and the deepwater sediment-traps may be attributed to degradation of organic matter as it sank through the water column. Comparison of fluxweighted δ13C and δ15N mean values between the deep-water sediment-traps and the core-top sediments showed that strong selective loss of organic matter components (lipids) depleted in 13C and 15N occurred during sediment burial. Nonetheless, the results of our study indicate that particles in the deep-water sediment-trap deposited as surface sediments on the seafloor preserve the record of surface-water conditions, highlighting the usefulness of sedimentary δ13C and δ15N values as a paleoceanographic application in the EJS.

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. Copyright © 2016 John Wiley & Sons, Ltd.

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. Copyright © 2013 Wiley Periodicals, Inc.

Functional Single-Cell Approach to Probing Nitrogen-Fixing Bacteria in Soil Communities by Resonance Raman Spectroscopy with 15N2 Labeling.

PubMed

Cui, Li; Yang, Kai; Li, Hong-Zhe; Zhang, Han; Su, Jian-Qiang; Paraskevaidi, Maria; Martin, Francis L; Ren, Bin; Zhu, Yong-Guan

2018-04-17

Nitrogen (N) fixation is the conversion of inert nitrogen gas (N 2 ) to bioavailable N essential for all forms of life. N 2 -fixing microorganisms (diazotrophs), which play a key role in global N cycling, remain largely obscure because a large majority are uncultured. Direct probing of active diazotrophs in the environment is still a major challenge. Herein, a novel culture-independent single-cell approach combining resonance Raman (RR) spectroscopy with 15 N 2 stable isotope probing (SIP) was developed to discern N 2 -fixing bacteria in a complex soil community. Strong RR signals of cytochrome c (Cyt c, frequently present in diverse N 2 -fixing bacteria), along with a marked 15 N 2 -induced Cyt c band shift, generated a highly distinguishable biomarker for N 2 fixation. 15 N 2 -induced shift was consistent well with 15 N abundance in cell determined by isotope ratio mass spectroscopy. By applying this biomarker and Raman imaging, N 2 -fixing bacteria in both artificial and complex soil communities were discerned and imaged at the single-cell level. The linear band shift of Cyt c versus 15 N 2 percentage allowed quantification of N 2 fixation extent of diverse soil bacteria. This single-cell approach will advance the exploration of hitherto uncultured diazotrophs in diverse ecosystems.

Nitrogen removal through N cycling from sediments in a constructed coastal marsh as assessed by 15N-isotope dilution.

PubMed

Ro, Hee-Myong; Kim, Pan-Gun; Park, Ji-Suk; Yun, Seok-In; Han, Junho

2018-04-01

Constructed coastal marsh regulates land-born nitrogen (N) loadings through salinity-dependent microbial N transformation processes. A hypothesis that salinity predominantly controls N removal in marsh was tested through incubation in a closed system with added- 15 NH 4 + using sediments collected from five sub-marshes in Shihwa marsh, Korea. Time-course patterns of concentrations and 15 N-atom% of soil-N pools were analyzed. Sediments having higher salinity and lower soil organic-C and acid-extractable organic-N exhibited slower rates of N mineralization and immobilization, nitrification, and denitrification. Rates of denitrification were not predicted well by sediment salinity but by its organic-C, indicating heterotrophic denitrification. Denitrification dominated N-loss from this marsh, and nitrogen removal capacity of this marsh was estimated at 337 kg N day -1 (9.9% of the daily N-loadings) considering the current rooting depth of common reeds (1.0 m). We showed that sediment N removal decreases with increasing salinity and can increase with increasing organic-C for heterotrophic denitrification. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sum-over-states density functional perturbation theory: Prediction of reliable 13C, 15N, and 17O nuclear magnetic resonance chemical shifts

NASA Astrophysics Data System (ADS)

Olsson, Lars; Cremer, Dieter

1996-11-01

Sum-over-states density functional perturbation theory (SOS-DFPT) has been used to calculate 13C, 15N, and 17O NMR chemical shifts of 20 molecules, for which accurate experimental gas-phase values are available. Compared to Hartree-Fock (HF), SOS-DFPT leads to improved chemical shift values and approaches the degree of accuracy obtained with second order Møller-Plesset perturbation theory (MP2). This is particularly true in the case of 15N chemical shifts where SOS-DFPT performs even better than MP2. Additional improvements of SOS-DFPT chemical shifts can be obtained by empirically correcting diamagnetic and paramagnetic contributions to compensate for deficiencies which are typical of DFT.

Spatial variations in δ13C and δ15N values of primary consumers in a coastal lagoon

NASA Astrophysics Data System (ADS)

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

2012-12-01

The analysis of the contribution of a food source to a consumer's diet or the trophic position of a consumer is highly sensitive to the variability of the isotopic values used as input data. However, little is known in coastal lagoons about the spatial variations in the isotopic values of primary consumers considered 'end members' in the isotope mixing models for quantifying the diet of secondary consumers or as a baseline for estimating the trophic position of consumers higher up in the food web. We studied the spatial variations in the δ13C and δ15N values of primary consumers and sedimentary organic matter (SOM) within a selected area of the Cabras lagoon (Sardinia, Italy). Our aim was to assess how much of the spatial variation in isotopic values of primary consumers was due to the spatial variability between sites and how much was due to differences in short distances from the shore. Samples were collected at four stations (50-100 m apart) selected randomly at two sites (1.5-2 km apart) chosen randomly at two distances from the shore (i.e. in proximity of the shore -Nearshore - and about 200 m away from the shore -Offshore). The sampling was repeated in March, May and August 2006 using new sites at the two chosen distances from the shore on each date. The isotopic values of size-fractionated seston and macrophytes were also analyzed as a complementary characterization of the study area. While δ15N did not show any spatial variations, the δ13C values of deposit feeders, Alitta (=Neanthes) succinea, Lekanesphaera hookeri, Hydrobia acuta and Gammarus aequicauda, were more depleted Offshore than Nearshore. For these species, there were significant effects of distance or distance × dates in the mean δ13C values, irrespective of the intrinsic variation between sites. SOM showed similar spatial variations in δ13C values, with Nearshore-Offshore differences up to 6‰. This indicates that the spatial isotopic changes are transferred from the food sources to the

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.

δ15N constraints on long-term nitrogen balances in temperate forests

USGS Publications Warehouse

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

2011-01-01

Biogeochemical theory emphasizes nitrogen (N) limitation and the many factors that can restrict N accumulation in temperate forests, yet lacks a working model of conditions that can promote naturally high N accumulation. We used a dynamic simulation model of ecosystem N and δ15N to evaluate which combination of N input and loss pathways could produce a range of high ecosystem N contents characteristic of forests in the Oregon Coast Range. Total ecosystem N at nine study sites ranged from 8,788 to 22,667 kg ha−1 and carbon (C) ranged from 188 to 460 Mg ha−1, with highest values near the coast. Ecosystem δ15N displayed a curvilinear relationship with ecosystem N content, and largely reflected mineral soil, which accounted for 96–98% of total ecosystem N. Model simulations of ecosystem N balances parameterized with field rates of N leaching required long-term average N inputs that exceed atmospheric deposition and asymbiotic and epiphytic N2-fixation, and that were consistent with cycles of post-fire N2-fixation by early-successional red alder. Soil water δ15NO3 − patterns suggested a shift in relative N losses from denitrification to nitrate leaching as N accumulated, and simulations identified nitrate leaching as the primary N loss pathway that constrains maximum N accumulation. Whereas current theory emphasizes constraints on biological N2-fixation and disturbance-mediated N losses as factors that limit N accumulation in temperate forests, our results suggest that wildfire can foster substantial long-term N accumulation in ecosystems that are colonized by symbiotic N2-fixing vegetation.

Chlorophyll a-specific Δ14C, δ13C and δ15N values in stream periphyton: implications for aquatic food web studies

NASA Astrophysics Data System (ADS)

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

2015-11-01

Periphytic algae attached to a streambed substrate (periphyton) are an important primary producer in stream ecosystems. We determined the isotopic composition of chlorophyll a in periphyton collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and natural radiocarbon abundances (Δ14C) were measured in chlorophyll a (δ13Cchl, δ15Nchl and Δ14Cchl) and bulk (δ13Cbulk, δ15Nbulk and Δ14Cbulk) for periphyton, a pure aquatic primary producer (Cladophora sp.) and a terrestrial primary producer (Quercus glauca). Periphyton δ13Cbulk and δ13Cchl values did not necessarily correspond to δ13Cbulk for an algal-grazing specialist (Epeorus latifolium). Periphyton Δ14Cchl values (-258 ‰ in April and -190 ‰ in October) were slightly lower than Δ14Cbulk values (-228 ‰ in April and -179 ‰ in October) but were close to the Δ14C value for dissolved inorganic carbon (DIC; -217 ± 31 ‰), which is a mixture of weathered carbonates (Δ14C = -1000 ‰), CO2 derived from aquatic and terrestrial organic matters (variable Δ14C) and dissolved atmospheric CO2 (Δ14C approximately +30 ‰ in 2013). Δ14Cchl values were also close to Δ14Cbulk for E. latifolium (-215 ‰ in April and -199 ‰ in October) and Cladophora sp. (-210 ‰), whereas the Δ14Cbulk value for Q. glauca (+27 ‰) was closer to Δ14C for atmospheric CO2. Although the bulk isotopic composition of periphyton is recognised as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89 to 95 % algal carbon (derived from 14C-depleted DIC) and 5 to 11 % terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).

Chlorophyll a specific Δ14C, δ13C and δ15N values in stream periphyton: implications for aquatic food web studies

NASA Astrophysics Data System (ADS)

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

2015-07-01

We determined the isotopic composition of chlorophyll a in periphytic algae attached to a streambed substrate (periphyton). The samples were collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and natural radiocarbon abundances (Δ14C) were measured in chlorophyll a (δ13Cchl, δ15Nchl and Δ14Cchl) and bulk (δ13Cbulk, δ15Nbulk and Δ14Cbulk) for periphyton, pure aquatic primary producer (Cladophora sp.) and terrestrial primary producer (Quercus glauca). Periphyton δ13Cbulk and δ13Cchl values did not necessarily correspond to δ13Cbulk for an algal-grazing specialist (Mayfly larva, Epeorus latifolium), suggesting that periphyton δ13C values do not faithfully trace carbon transfer between primary producers and primary consumers. Periphyton Δ14Cchl values (-258 ‰ in April and -190 ‰ in October) were slightly lower than Δ14Cbulk values (-228 ‰ in April and -179 ‰ in October), but were close to the Δ14C value for dissolved inorganic carbon (DIC) (-217 ± 31 ‰), which is a mixture of weathered carbonates (Δ14C = -1000 ‰) and dissolved atmospheric CO2 (Δ14C approximately +30 ‰ in 2013). Δ14Cchl values were also close to Δ14Cbulk for E. latifolium (-215 ‰ in April and -199 ‰ in October) and Cladophora sp. (-210 ‰), whereas the Δ14Cbulk value for Q. glauca (+27 ‰) was closer to Δ14C for atmospheric CO2. Although the bulk isotopic composition of periphyton is recognised as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89 to 95 % algal carbon (derived from 14C-depleted DIC) and 5 to 11 % terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).

Arctic Sea Ice in a 1.5°C Warmer World

NASA Astrophysics Data System (ADS)

Niederdrenk, Anne Laura; Notz, Dirk

2018-02-01

We examine the seasonal cycle of Arctic sea ice in scenarios with limited future global warming. To do so, we analyze two sets of observational records that cover the observational uncertainty of Arctic sea ice loss per degree of global warming. The observations are combined with 100 simulations of historical and future climate evolution from the Max Planck Institute Earth System Model Grand Ensemble. Based on the high-sensitivity observations, we find that Arctic September sea ice is lost with low probability (P≈ 10%) for global warming of +1.5°C above preindustrial levels and with very high probability (P> 99%) for global warming of +2°C above preindustrial levels. For the low-sensitivity observations, September sea ice is extremely unlikely to disappear for +1.5°C warming (P≪ 1%) and has low likelihood (P≈ 10%) to disappear even for +2°C global warming. For March, both observational records suggest a loss of 15% to 20% of Arctic sea ice area for 1.5°C to 2°C global warming.

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

Diabetes induced renal urea transport alterations assessed with 3D hyperpolarized 13 C,15 N-Urea.

PubMed

Bertelsen, Lotte B; Nielsen, Per M; Qi, Haiyun; Nørlinger, Thomas S; Zhang, Xiaolu; Stødkilde-Jørgensen, Hans; Laustsen, Christoffer

2017-04-01

In the current study, we investigated hyperpolarized urea as a possible imaging biomarker of the renal function by means of the intrarenal osmolality gradient. Hyperpolarized three-dimensional balanced steady state 13 C MRI experiments alongside kidney function parameters and quantitative polymerase chain reaction measurements was performed on two groups of rats, a streptozotocin type 1 diabetic group and a healthy control group. A significant decline in intrarenal steepness of the urea gradient was found after 4 weeks of untreated insulinopenic diabetes in agreement with an increased urea transport transcription. MRI and hyperpolarized [ 13 C, 15 N]urea can monitor the changes in the corticomedullary urea concentration gradients in diabetic and healthy control rats. Magn Reson Med 77:1650-1655, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

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.

15N-metabolic labeling for comparative plasma membrane proteomics in Arabidopsis cells.

PubMed

Lanquar, Viviane; Kuhn, Lauriane; Lelièvre, Françoise; Khafif, Mehdi; Espagne, Christelle; Bruley, Christophe; Barbier-Brygoo, Hélène; Garin, Jérôme; Thomine, Sébastien

2007-03-01

An important goal for proteomic studies is the global comparison of proteomes from different genotypes, tissues, or physiological conditions. This has so far been mostly achieved by densitometric comparison of spot intensities after protein separation by 2-DE. However, the physicochemical properties of membrane proteins preclude the use of 2-DE. Here, we describe the use of in vivo labeling by the stable isotope 15N as an alternative approach for comparative membrane proteomic studies in plant cells. We confirm that 15N-metabolic labeling of proteins is possible and efficient in Arabidopsis suspension cells. Quantification of 14N versus 15N MS signals reflects the relative abundance of 14N and 15N proteins in the sample analyzed. We describe the use of 15N-metabolic labeling to perform a partial comparative analysis of Arabidopsis cells following cadmium exposure. By focusing our attention on plasma membrane proteins, we were able to confidently identify proteins showing up to 5-fold regulation compared to unexposed cells. This study provides a proof of principle that 15N-metabolic labeling is a useful technique for comparative membrane proteome studies.

Isotope (δ13C, δ15N, δ2H) diet-tissue discrimination in African grey parrot Psittacus erithacus: implications for forensic studies.

PubMed

Symes, Craig; Skhosana, Felix; Butler, Mike; Gardner, Brett; Woodborne, Stephan

2017-12-01

Diet-tissue isotopic relationships established under controlled conditions are informative for determining the dietary sources and geographic provenance of organisms. We analysed δ 13 C, δ 15 N, and non-exchangeable δ 2 H values of captive African grey parrot Psittacus erithacus feathers grown on a fixed mixed-diet and borehole water. Diet-feather Δ 13 C and Δ 15 N discrimination values were +3.8 ± 0.3 ‰ and +6.3 ± 0.7 ‰ respectively; significantly greater than expected. Non-exchangeable δ 2 H feather values (-62.4 ± 6.4 ‰) were more negative than water (-26.1 ± 2.5 ‰) offered during feather growth. There was no positive relationship between the δ 13 C and δ 15 N values of the samples along each feather with the associated samples of food offered, or the feather non-exchangeable hydrogen isotope values with δ 2 H values of water, emphasising the complex processes involved in carbohydrate, protein, and income water routing to feather growth. Understanding the isotopic relationship between diet and feathers may provide greater clarity in the use of stable isotopes in feathers as a tool in determining origins of captive and wild-caught African grey parrots, a species that is widespread in aviculture and faces significant threats to wild populations. We suggest that these isotopic results, determined even in controlled laboratory conditions, be used with caution.

13C and 15N—Chemical Shift Anisotropy of Ampicillin and Penicillin-V Studied by 2D-PASS and CP/MAS NMR

NASA Astrophysics Data System (ADS)

Antzutkin, Oleg N.; Lee, Young K.; Levitt, Malcolm H.

1998-11-01

The principal values of the chemical shift tensors of all13C and15N sites in two antibiotics, ampicillin and penicillin-V, were determined by 2-dimensionalphaseadjustedspinningsideband (2D-PASS) and conventional CP/MAS experiments. The13C and15N chemical shift anisotropies (CSA), and their confidence limits, were evaluated using a Mathematica program. The CSA values suggest a revised assignment of the 2-methyl13C sites in the case of ampicillin. We speculate on a relationship between the chemical shift principal values of many of the13C and15N sites and the β-lactam ring conformation.

Comparative study of the interaction of meso-tetrakis (N-para-trimethyl-anilium) porphyrin (TMAP) in its free base and Fe derivative form with oligo(dA.dT)15 and oligo(dG.dC)15.

PubMed

Bathaie, S Zahra; Ajloo, Davood; Daraie, Marzieh; Ghadamgahi, Maryam

2015-01-01

Interaction between a cationic porphyrin and its ferric derivative with oligo(dA.dT)15 and oligo(dG.dC)15 was studied by UV-vis spectroscopy, resonance light scattering (RLS), and circular dichroism (CD) at different ionic strengths; molecular docking and molecular dynamics simulation were also used for completion. Followings are the observed changes in the spectral properties of meso-tetrakis (N-para-trimethyl-anilium) porphyrin (TMAP), as a free-base porphyrin with no axial ligand, and its Fe derivative (FeTMAP) upon interaction with oligo(dA.dT)15 and oligo(dG.dC)15: (1) the substantial red shift and hypochromicity at the Soret maximum in the UV-vis spectra; (2) the increased RLS intensity by increasing the ionic strength; and (3) an intense bisignate excitonic CD signal. All of them are the reasons for TMAP and FeTMAP binding to oligo(dA.dT)15 and oligo(dG.dC)15 with the outside binding mode, accompanied by the self-stacking of the ligands along the oligonucleotide helix. The CD results demonstrated a drastic change from excitonic in monomeric behavior at higher ionic strengths, which indicates the groove binding of the ligands with oligonucleotides. Molecular docking also confirmed the groove binding mode of the ligands and estimated the binding constants and energies of the interactions. Their interaction trend was further confirmed by molecular dynamics technique and structure parameters obtained from simulation. It showed that TMAP reduced the number of intermolecular hydrogen bonds and increased the solvent accessible surface area in the oligonucleotide. The self-aggregation of ligands at lower concentrations was also confirmed.

49 CFR 15.15 - SSI disclosed by DOT.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Transportation Office of the Secretary of Transportation PROTECTION OF SENSITIVE SECURITY INFORMATION § 15.15 SSI... Freedom of Information Act (5 U.S.C. 552), the Privacy Act (5 U.S.C. 552a), and other laws, records... persons without a need to know. (b) Disclosure under the Freedom of Information Act and the Privacy Act...

49 CFR 15.15 - SSI disclosed by DOT.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Transportation Office of the Secretary of Transportation PROTECTION OF SENSITIVE SECURITY INFORMATION § 15.15 SSI... Freedom of Information Act (5 U.S.C. 552), the Privacy Act (5 U.S.C. 552a), and other laws, records... persons without a need to know. (b) Disclosure under the Freedom of Information Act and the Privacy Act...

26 CFR 1.381(c)(15)-1 - Indebtedness of certain personal holding companies.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 26 Internal Revenue 4 2010-04-01 2010-04-01 false Indebtedness of certain personal holding companies. 1.381(c)(15)-1 Section 1.381(c)(15)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES Insolvency Reorganizations § 1.381(c)(15...

Plant δ15 N reflects the high landscape-scale heterogeneity of soil fertility and vegetation productivity in a Mediterranean semiarid ecosystem.

PubMed

Ruiz-Navarro, Antonio; Barberá, Gonzalo G; Albaladejo, Juan; Querejeta, José I

2016-12-01

We investigated the magnitude and drivers of spatial variability in soil and plant δ 15 N across the landscape in a topographically complex semiarid ecosystem. We hypothesized that large spatial heterogeneity in water availability, soil fertility and vegetation cover would be positively linked to high local-scale variability in δ 15 N. We measured foliar δ 15 N in three dominant plant species representing contrasting plant functional types (tree, shrub, grass) and mycorrhizal association types (ectomycorrhizal or arbuscular mycorrhizal). This allowed us to investigate whether δ 15 N responds to landscape-scale environmental heterogeneity in a consistent way across species. Leaf δ 15 N varied greatly within species across the landscape and was strongly spatially correlated among co-occurring individuals of the three species. Plant δ 15 N correlated tightly with soil δ 15 N and key measures of soil fertility, water availability and vegetation productivity, including soil nitrogen (N), organic carbon (C), plant-available phosphorus (P), water-holding capacity, topographic moisture indices and normalized difference vegetation index. Multiple regression models accounted for 62-83% of within-species variation in δ 15 N across the landscape. The tight spatial coupling and interdependence of the water, N and C cycles in drylands may allow the use of leaf δ 15 N as an integrative measure of variations in moisture availability, biogeochemical activity, soil fertility and vegetation productivity (or 'site quality') across the landscape. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Deuterium and 15N fractionation in N2H+ during the formation of a Sun-like star

NASA Astrophysics Data System (ADS)

De Simone, M.; Fontani, F.; Codella, C.; Ceccarelli, C.; Lefloch, B.; Bachiller, R.; López-Sepulcre, A.; Caux, E.; Vastel, C.; Soldateschi, J.

2018-05-01

Although chemical models predict that the deuterium fractionation in N2H+ is a good evolutionary tracer in the star formation process, the fractionation of nitrogen is still a poorly understood process. Recent models have questioned the similar evolutionary trend expected for the two fractionation mechanisms in N2H+, based on a classical scenario in which ion-neutral reactions occurring in cold gas should have caused an enhancement of the abundance of N2D+, 15NNH+, and N15NH+. In the framework of the ASAI IRAM-30m large program, we have investigated the fractionation of deuterium and 15N in N2H+ in the best known representatives of the different evolutionary stages of the Sun-like star formation process. The goal is to ultimately confirm (or deny) the classical `ion-neutral reactions' scenario that predicts a similar trend for D and 15N fractionation. We do not find any evolutionary trend of the 14N/15N ratio from both the 15NNH+ and N15NH+ isotopologues. Therefore, our findings confirm that, during the formation of a Sun-like star, the core evolution is irrelevant in the fractionation of 15N. The independence of the 14N/15N ratio with time, found also in high-mass star-forming cores, indicates that the enrichment in 15N revealed in comets and protoplanetary discs is unlikely to happen at core scales. Nevertheless, we have firmly confirmed the evolutionary trend expected for the H/D ratio, with the N2H+/N2D+ ratio decreasing before the pre-stellar core phase, and increasing monotonically during the protostellar phase. We have also confirmed clearly that the two fractionation mechanisms are not related.

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

NASA Astrophysics Data System (ADS)

Renner, Christian; Holak, Tad A.

2000-08-01

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

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

Heterogeneous Microtesla SABRE Enhancement of 15 N NMR Signals.

PubMed

Kovtunov, Kirill V; Kovtunova, Larisa M; Gemeinhardt, Max E; Bukhtiyarov, Andrey V; Gesiorski, Jonathan; Bukhtiyarov, Valerii I; Chekmenev, Eduard Y; Koptyug, Igor V; Goodson, Boyd M

2017-08-21

The hyperpolarization of heteronuclei via signal amplification by reversible exchange (SABRE) was investigated under conditions of heterogeneous catalysis and microtesla magnetic fields. Immobilization of [IrCl(COD)(IMes)], [IMes=1,3-bis(2,4,6-trimethylphenyl), imidazole-2-ylidene; COD=cyclooctadiene] catalyst onto silica particles modified with amine linkers engenders an effective heterogeneous SABRE (HET-SABRE) catalyst that was used to demonstrate a circa 100-fold enhancement of 15 N NMR signals in 15 N-pyridine at 9.4 T following parahydrogen bubbling within a magnetic shield. No 15 N NMR enhancement was observed from the supernatant liquid following catalyst separation, which along with XPS characterization supports the fact that the effects result from SABRE under heterogeneous catalytic conditions. The technique can be developed further for producing catalyst-free agents via SABRE with hyperpolarized heteronuclear spins, and thus is promising for biomedical NMR and MRI applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Measurement of 15N longitudinal relaxation rates in 15NH4+ spin systems to characterise rotational correlation times and chemical exchange

NASA Astrophysics Data System (ADS)

Hansen, D. Flemming

2017-06-01

Many chemical and biological processes rely on the movement of monovalent cations and an understanding of such processes can therefore only be achieved by characterising the dynamics of the involved ions. It has recently been shown that 15N-ammonium can be used as a proxy for potassium to probe potassium binding in bio-molecules such as DNA quadruplexes and enzymes. Moreover, equations have been derived to describe the time-evolution of 15N-based spin density operator elements of 15NH4+ spin systems. Herein NMR pulse sequences are derived to select specific spin density matrix elements of the 15NH4+ spin system and to measure their longitudinal relaxation in order to characterise the rotational correlation time of the 15NH4+ ion as well as report on chemical exchange events of the 15NH4+ ion. Applications to 15NH4+ in acidic aqueous solutions are used to cross-validate the developed pulse sequence while measurements of spin-relaxation rates of 15NH4+ bound to a 41 kDa domain of the bacterial Hsp70 homologue DnaK are presented to show the general applicability of the derived pulse sequence. The rotational correlation time obtained for 15N-ammonium bound to DnaK is similar to the correlation time that describes the rotation about the threefold axis of a methyl group. The methodology presented here provides, together with the previous theoretical framework, an important step towards characterising the motional properties of cations in macromolecular systems.

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

2016-03-09

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.

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.

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

Isotopic fractionation of nitrogen and carbon in Paleoarchean cherts from Pilbara craton, Western Australia: Origin of 15N-depleted nitrogen

NASA Astrophysics Data System (ADS)

Pinti, Daniele L.; Hashizume, Ko; Sugihara, Akiyo; Massault, Marc; Philippot, Pascal

2009-07-01

Nitrogen and carbon isotopic compositions, together with mineralogy and trace element geochemistry, were studied in a few kerogen-rich Paleoarchean cherts, a barite and a dolomitic stromatolite belonging to the eastern (Dixon Island Formation) and western (Dresser and Strelley Pool Chert Formations; North Pole Dome and Marble Bar) terranes of Pilbara Craton, Western Australia. The aim of the study was to search for 15N-depleted isotopic signatures, often found in kerogens of this period, and explain the origin of these anomalies. Trace elements suggest silica precipitation by hydrothermal fluids as the main process of chert formation with a contamination from volcanoclastic detritus. This is supported by the occurrence of hydrothermal-derived minerals in the studied samples indicating precipitation temperatures up to 350 °C. Only a dolomitic stromatolite from Strelley Pool shows a superchondritic Y/Ho ratio of 72 and a positive Eu/Eu * anomaly of 1.8, characteristic of chemical precipitates from the Archean seawater. The bulk δ 13C vs. δ 15N values measured in the cherts show a roughly positive co-variation, except for one sample from the North Pole (PI-85-00). The progressive enrichment in 15N and 13C from a pristine source having δ 13C ⩽ -36‰ and δ 15N ⩽ -4‰ is correlated with a progressive depletion in N content and to variations in Ba/La and Co/As ratios. These trends have been interpreted as a progressive hydrothermal alteration of the cherts by metamorphic fluids. Isotopic exchange at 350 °C between NH 4+(rock) and N 2(fluid) may explain the isotopic and elemental composition of N in the studied cherts. However, we need to assume isotopic exchange at 350 °C between carbonate C and graphite to explain the large 13C enrichment recorded. Only sample PI-85-00 shows a large N loss (90%) with a positive δ 15N value (+11‰), while C (up to 120 ppm and δ 13C -38‰) seems to be unaffected. This pattern has been interpreted as the result of

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.

Provenancing Archaeological Wool Textiles from Medieval Northern Europe by Light Stable Isotope Analysis (δ13C, δ15N, δ2H)

PubMed Central

von Holstein, Isabella C. C.; Walton Rogers, Penelope; Craig, Oliver E.; Penkman, Kirsty E. H.; Newton, Jason; Collins, Matthew J.

2016-01-01

We investigate the origin of archaeological wool textiles preserved by anoxic waterlogging from seven medieval archaeological deposits in north-western Europe (c. 700–1600 AD), using geospatial patterning in carbon (δ13C), nitrogen (δ15N) and non-exchangeable hydrogen (δ2H) composition of modern and ancient sheep proteins. δ13C, δ15N and δ2H values from archaeological wool keratin (n = 83) and bone collagen (n = 59) from four sites were interpreted with reference to the composition of modern sheep wool from the same regions. The isotopic composition of wool and bone collagen samples clustered strongly by settlement; inter-regional relationships were largely parallel in modern and ancient samples, though landscape change was also significant. Degradation in archaeological wool samples, examined by elemental and amino acid composition, was greater in samples from Iceland (Reykholt) than in samples from north-east England (York, Newcastle) or northern Germany (Hessens). A nominal assignment approach was used to classify textiles into local/non-local at each site, based on maximal estimates of isotopic variability in modern sheep wool. Light element stable isotope analysis provided new insights into the origins of wool textiles, and demonstrates that isotopic provenancing of keratin preserved in anoxic waterlogged contexts is feasible. We also demonstrate the utility of δ2H analysis to understand the location of origin of archaeological protein samples. PMID:27764106

COVALENT BINDING OF REDUCED METABOLITES OF [15N3] TNT TO SOIL ORGANIC MATTER DURING A BIOREMEDIATION PROCESS ANALYZED BY 15N NMR SPECTROSCOPY. (R826646)

EPA Science Inventory

Evidence is presented for the covalent binding of
biologically reduced metabolites of 2,4,6-¹⁵N₃-trinitrotoluene
(TNT) to different soil fractions (humic acids, fulvic
acids, and humin) using liquid ¹⁵N NMR spectroscopy. A
silylation p...

17 CFR 240.15c3-2 - Customers' free credit balances.

Code of Federal Regulations, 2011 CFR

2011-04-01

... balances. 240.15c3-2 Section 240.15c3-2 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... Customers' free credit balances. No broker or dealer shall use any funds arising out of any free credit balance carried for the account of any customer in connection with the operation of the business of such...

17 CFR 240.15c3-2 - Customers' free credit balances.

Code of Federal Regulations, 2010 CFR

2010-04-01

... balances. 240.15c3-2 Section 240.15c3-2 Commodity and Securities Exchanges SECURITIES AND EXCHANGE... Customers' free credit balances. No broker or dealer shall use any funds arising out of any free credit balance carried for the account of any customer in connection with the operation of the business of such...

Interferometric Imaging of Titan’s HC3N, H13CCCN, and HCCC15N

NASA Astrophysics Data System (ADS)

Cordiner, M. A.; Nixon, C. A.; Charnley, S. B.; Teanby, N. A.; Molter, E. M.; Kisiel, Z.; Vuitton, V.

2018-05-01

We present the first maps of cyanoacetylene isotopologues in Titan’s atmosphere, including H13CCCN and HCCC15N, detected in the 0.9 mm band using the Atacama Large Millimeter/submillimeter array (ALMA) around the time of Titan’s (southern winter) solstice in 2017 May. The first high-resolution map of HC3N in its v 7 = 1 vibrationally excited state is also presented, revealing a unique snapshot of the global HC3N distribution, free from the strong optical depth effects that adversely impact the ground-state (v = 0) map. The HC3N emission is found to be strongly enhanced over Titan’s south pole (by a factor of 5.7 compared to the north pole), consistent with rapid photochemical loss of HC3N from the summer hemisphere combined with production and transport to the winter pole since the 2015 April ALMA observations. The H13CCCN/HCCC15N flux ratio is derived at the southern HC3N peak, and implies an HC3N/HCCC15N ratio of 67 ± 14. This represents a significant enrichment in 15N compared with Titan’s main molecular nitrogen reservoir, which has a 14N/15N ratio of 167, and confirms the importance of photochemistry in determining the nitrogen isotopic ratio in Titan’s organic inventory.

Ammonia 15N/14N Isotope Ratio in the Jovian Atmosphere

NASA Technical Reports Server (NTRS)

Mahaffy, P.R.; Niemann, H. B.; Atreya, S. K.; Wong, M. H.; Owen, T. C; Einaudi, Franco (Technical Monitor)

2000-01-01

Data from the Galileo Probe Mass Spectrometer has been used to derive the N-15/N-14 isotope ratio in ammonia at Jupiter. Although the mass spectral interference from the water contribution to 18 amu makes an accurate derivation of the (N-15)H3/(N-14)H3 ratio difficult from measurements of the singly ionized signals at 18 and 17 amu, this interference is not present in the doubly charged 8.5 and 9.0 amu signals from (N-14)H3++ and (N-15)H3++ respectively. Although the count rate from the 9 amu signal is low during the direct sampling of the atmosphere, the ammonia signal was considerably enhanced during the first enrichment cell (EC1) experiment that measured gas sampled between 0.8 and 2.8 bar. Count rates at 9 amu in the EC1 experiment reach 60/second and measure ammonia sampled from 0.88 to 2.8 bar. In the EC1 measurements the 8.5 amu signal is not measured directly, but can be calculated from the ammonia contribution to 17 amu and the ratio of NH3 ions of a double to single charged observed during a high resolution mass scan taken near the end of the descent. The high resolution scan gives this ratio from ammonia sampled much deeper in the atmosphere. These results are described and compared with Infrared Space Observatory-Short Wavelength Spectrometer (ISO-SWS) observations that give this ratio at 400 mbar.

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.

Stable Isotopes (δ13C and δ15N) in Two Depth-Segregated Species of Deep-Sea Gorgonian Octocorals from the Eastern Pacific

NASA Astrophysics Data System (ADS)

Barnes, S.; Williams, B.; Etnoyer, P. J.

2016-02-01

Found across the world's oceans and with ages up to hundreds of years, deep-sea gorgonian octocorals represent valuable archives of past oceanic climate change. Similar to the rings of trees, deep-sea gorgonian octocorals form their skeletons in distinct growth increments, and the chemical composition of these growth bands record changes in their environment over time. The ratios of carbon and nitrogen stable isotopes in the sinking particulate organic matter (POM) that the corals feed upon drive the δ13C and δ15N of the organic material in their growth bands. Changes in the coral skeletal δ13C and δ15N therefore reflect changes in surface water nutrient levels and primary productivity. Here, we measured δ13C and δ15N across the growth bands of three Acanthogorgia sp. and two Eugoria rubens specimens collected from the Channel Islands National Marine Sanctuary in California in 2015 to study inter- and intraspecies variability and develop these species as archives of surface water processes. The taxa represent two different depth strata in the Southern California Bight; Acanthogorgia are typically observed 150-400 meters deep, while Eugorgia corals occur in relatively shallower waters between 50-100 meters deep. Results will be interpreted in the context of eastern Pacific POM values and local environmental influences to examine changes in the corals' food source. Results will also provide information on subsequent alteration of carbon and nitrogen after their incorporation into Acanthogorgia and Eugoria skeletons to aid future study of these corals as proxy records of oceanic climate change.

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.

Evidence for genetic variation of Eurasian avian influenza viruses, subtype H15: The first report of an H15N7 virus

USDA-ARS?s Scientific Manuscript database

Since the first detection of H15 avian influenza viruses (AIVs) in Australia in 1979, only seven H15 strains have been reported. A new H15 AIV was detected in Ukraine in 2010, carrying the unique HA-NA subtype combination H15N7. This virus replicated efficiently in chicken eggs, and antisera against...

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

NASA Astrophysics Data System (ADS)

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

2015-08-01

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

17 CFR 240.15c3-1a - Options (Appendix A to 17 CFR 240.15c3-1).

Code of Federal Regulations, 2014 CFR

2014-04-01

... Regulations Under the Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c3-1a... from an assumed movement (both up and down) in the current market value of the underlying instrument...) The term major market foreign currency shall mean the currency of a sovereign nation whose short-term...

The Pneumococcal Serotype 15C Capsule Is Partially O-Acetylated and Allows for Limited Evasion of 23-Valent Pneumococcal Polysaccharide Vaccine-Elicited Anti-Serotype 15B Antibodies

PubMed Central

Spencer, Brady L.; Shenoy, Anukul T.; Orihuela, Carlos J.

2017-01-01

ABSTRACT As a species, Streptococcus pneumoniae (the pneumococcus) utilizes a diverse array of capsular polysaccharides to evade the host. In contrast to large variations in sugar composition and linkage formation, O-acetylation is a subtle capsular modification that nonetheless has a large impact on capsular shielding and recognition of the capsule by vaccine-elicited antibodies. Serotype 15B, which is included in the 23-valent pneumococcal polysaccharide vaccine (PPV23), carries the putative O-acetyltransferase gene wciZ. The coding sequence of wciZ contains eight consecutive TA repeats [(TA)8]. Replication slippage is thought to result in the addition or loss of TA repeats, subsequently causing frameshift and truncation of WciZ to yield a nonacetylated serotype, 15C. Using sensitive serological tools, we show that serotype 15C isolates whose wciZ contains seven or nine TA repeats retain partial O-acetylation, while serotype 15C isolates whose wciZ contains six TA repeats have barely detectable O-acetylation. We confirmed by inhibition enzyme-linked immunosorbent assay that (TA)7 serotype 15C is ∼0.1% as acetylated as serotype 15B, while serotype 15X is nonacetylated. To eliminate the impact of genetic background, we created isogenic serotype 15B, (TA)7 serotype 15C, and 15BΔwciZ (15X) strains and found that reduction or absence of WciZ-mediated O-acetylation did not affect capsular shielding from phagocytes, biofilm formation, adhesion to nasopharyngeal cells, desiccation tolerance, or murine colonization. Sera from PPV23-immunized persons opsonized serotype 15B significantly but only slightly better than serotypes 15C and 15X; thus, PPV23 may not result in expansion of serotype 15C. PMID:28637806

The Pneumococcal Serotype 15C Capsule Is Partially O-Acetylated and Allows for Limited Evasion of 23-Valent Pneumococcal Polysaccharide Vaccine-Elicited Anti-Serotype 15B Antibodies.

PubMed

Spencer, Brady L; Shenoy, Anukul T; Orihuela, Carlos J; Nahm, Moon H

2017-08-01

As a species, Streptococcus pneumoniae (the pneumococcus) utilizes a diverse array of capsular polysaccharides to evade the host. In contrast to large variations in sugar composition and linkage formation, O-acetylation is a subtle capsular modification that nonetheless has a large impact on capsular shielding and recognition of the capsule by vaccine-elicited antibodies. Serotype 15B, which is included in the 23-valent pneumococcal polysaccharide vaccine (PPV23), carries the putative O-acetyltransferase gene wciZ The coding sequence of wciZ contains eight consecutive TA repeats [(TA) 8 ]. Replication slippage is thought to result in the addition or loss of TA repeats, subsequently causing frameshift and truncation of WciZ to yield a nonacetylated serotype, 15C. Using sensitive serological tools, we show that serotype 15C isolates whose wciZ contains seven or nine TA repeats retain partial O-acetylation, while serotype 15C isolates whose wciZ contains six TA repeats have barely detectable O-acetylation. We confirmed by inhibition enzyme-linked immunosorbent assay that (TA) 7 serotype 15C is ∼0.1% as acetylated as serotype 15B, while serotype 15X is nonacetylated. To eliminate the impact of genetic background, we created isogenic serotype 15B, (TA) 7 serotype 15C, and 15BΔ wciZ (15X) strains and found that reduction or absence of WciZ-mediated O-acetylation did not affect capsular shielding from phagocytes, biofilm formation, adhesion to nasopharyngeal cells, desiccation tolerance, or murine colonization. Sera from PPV23-immunized persons opsonized serotype 15B significantly but only slightly better than serotypes 15C and 15X; thus, PPV23 may not result in expansion of serotype 15C. Copyright © 2017 American Society for Microbiology.

Extreme heat waves under 1.5 °C and 2 °C global warming

NASA Astrophysics Data System (ADS)

Dosio, Alessandro; Mentaschi, Lorenzo; Fischer, Erich M.; Wyser, Klaus

2018-05-01

Severe, extreme, and exceptional heat waves, such as those that occurred over the Balkans (2007), France (2003), or Russia (2010), are associated with increased mortality, human discomfort and reduced labour productivity. Based on the results of a very high-resolution global model, we show that, even at 1.5 °C warming, a significant increase in heat wave magnitude is expected over Africa, South America, and Southeast Asia. Compared to a 1.5 °C world, under 2 °C warming the frequency of extreme heat waves would double over most of the globe. In a 1.5 °C world, 13.8% of the world population will be exposed to severe heat waves at least once every 5 years. This fraction becomes nearly three times larger (36.9%) under 2 °C warming, i.e. a difference of around 1.7 billion people. Limiting global warming to 1.5 °C will also result in around 420 million fewer people being frequently exposed to extreme heat waves, and ~65 million to exceptional heat waves. Nearly 700 million people (9.0% of world population) will be exposed to extreme heat waves at least once every 20 years in a 1.5 °C world, but more than 2 billion people (28.2%) in a 2 °C world. With current emission trends threatening even the 2 °C target, our study is helpful to identify regions where limiting the warming to 1.5 °C would have the strongest benefits in reducing population exposure to extreme heat.

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

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.

Abrupt recent shift in δ13C and δ15N values in Adélie penguin eggshell in Antarctica

PubMed Central

Emslie, Steven D.; Patterson, William P.

2007-01-01

Stable isotope values of carbon (δ13C) and nitrogen (δ15N) in blood, feathers, eggshell, and bone have been used in seabird studies since the 1980s, providing a valuable source of information on diet, foraging patterns, and migratory behavior in these birds. These techniques can also be applied to fossil material when preservation of bone and other tissues is sufficient. Excavations of abandoned Adélie penguin (Pygoscelis adeliae) colonies in Antarctica often provide well preserved remains of bone, feathers, and eggshell dating from hundreds to thousands of years B.P. Herein we present an ≈38,000-year time series of δ13C and δ15N values of Adélie penguin eggshell from abandoned colonies located in three major regions of Antarctica. Results indicate an abrupt shift to lower-trophic prey in penguin diets within the past ≈200 years. We posit that penguins only recently began to rely on krill as a major portion of their diet, in conjunction with the removal of baleen whales and krill-eating seals during the historic whaling era. Our results support the “krill surplus” hypothesis that predicts excess krill availability in the Southern Ocean after this period of exploitation. PMID:17620620

(15)N and (13)C group-selective techniques extend the scope of STD NMR detection of weak host-guest interactions and ligand screening.

PubMed

Kövér, Katalin E; Wéber, Edit; Martinek, Tamás A; Monostori, Eva; Batta, Gyula

2010-10-18

Saturation transfer difference (STD) is a valuable tool for studying the binding of small molecules to large biomolecules and for obtaining detailed information on the binding epitopes. Here, we demonstrate that the proposed (15)N/(13)C variants of group-selective, "GS-STD" experiments provide a powerful approach to mapping the binding epitope of a ligand even in the absence of efficient spin diffusion within the target protein. Therefore, these experimental variants broaden the scope of STD studies to smaller and/or more-dynamic targets. The STD spectra obtained in four different experimental setups (selective (1)H STD, (15)N GS-STD, (13)C(Ar) and (13)C(aliphatic) GS-STD approaches) revealed that the signal-intensity pattern of the difference spectra is affected by both the type and the spatial distribution of the excited "transmitter" atoms, as well as by the efficiency of the spin-diffusion-mediated magnetization transfer. The performance of the experiments is demonstrated on a system by using the lectin, galectin-1 and its carbohydrate ligand, lactose.

17 CFR 240.15c1-8 - Sales at the market.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Sales at the market. 240.15c1... Securities Exchange Act of 1934 Rules Relating to Over-The-Counter Markets § 240.15c1-8 Sales at the market... securities exchange that such security is being offered to such customer “at the market” or at a price...

Enhanced plant growth at reduced N2O emissions: 15N dynamics confirm nitrate capture and release of co-composted biochar

NASA Astrophysics Data System (ADS)

Kammann, Claudia; Schmidt, Hans-Peter; Williams, Anne; Hagemann, Nikolas; Marhan, Sven; Clough, Tim; Mueller, Christoph

2017-04-01

Pyrogenic carbon (biochar) produced from biomass may be used as a soil amendment to sequester biomass-C and to mitigate climate change. Moreover, biochar may increase soil fertility and optimize nutrient cycling in agro-ecosystems. However, according to meta-studies large additions (>10 t ha-1) of pure biochar, may only lead to moderate yield increases. Thus, there are no economic benefits for farmers to use biochar. Recently, it has been suggested that biochar may be used as an on-farm nutrient management tool (feed additive, liquid manure treatment, composting) to deliver small doses of nutrients and biochar to the soil each year. It may also be used as a carrier for (organic) nutrients in small doses (0.5 - 2 t ha-1) in the root zone; recent studies reported considerably increased yields. The mechanisms, however, are not well understood. Co-composted biochar was recently shown to promote plant growth due to its nutrient delivery and release capabilities, particularly nitrate (NO3-). To gain further insights into biochar-nitrogen (N) interactions, we conducted a 15N labelling-tracing study under controlled conditions with treatments consisting of a non-biochar amended control, 2% (wt/wt) of untreated biochar particles (BCpure ,no intrinsic content of nitrate) and a 2% co-composted biochar (BCcomp, 5.3 g NO3-N kg-1 as a result of composting), replicated thrice. Biochars were added to a sandy loam soil in jars (200 g) planted with barley (Hordeum vulgare L.) seedlings. Fertilizer (NH4NO3) was homogenously added with either the ammonium (NH4+) or the nitrate (NO3-) pools 15N labelled (60 atom% 15N) hours before planting the seedlings. Sets of 18 jars were harvested on days 1, 3, 8, 15 and 29 and nitrogen pools were analysed to trace 15N fertilizer fate (soil mineral N, plant biomass, biochar particles, nitrous oxide (N2O) emissions). Interestingly, both BCpure and BCcomp captured fertilizer 15N from the soil matrix within hours of addition, with higher capture of 15

An evaluation of sources of nitrogen in shallow groundwater using (15)N abundance technique.

PubMed

Alva, A K; Dou, H; Paramasivam, S; Wang, F L; Graetz, D A; Sajwan, K S

2006-01-01

A (15)N abundance technique was employed to identify the source of NO(3)-N in groundwater under three commercial citrus production sites in central Florida. Water samples were collected from 0 to 300 and 300 to 600 cm depths in the surficial aquifer and analyzed for NO(3)-N and delta N-15 (delta (15)N). Groundwater samples were also collected in a residential area adjacent to one of the citrus groves and analyzed for NO(3)-N and delta (15)N. The delta (15)N values were in the range of (+)1 to (+)10% in both depths underneath the citrus groves. The range of delta (15)N measured in this study represents the range expected for groundwater that was impacted by NO(3)-N originated from mineralization of organic N from the soil as well as from the crop residue. There are occasional high delta (15)N values which are indicative of the effects of NH(3) volatilization losses of applied fertilizer N. The range of delta (15)N values for groundwater samples collected from the residential area adjacent to the citrus groves was very similar to that from the groundwater underneath the citrus groves. Thus, the source of NO(3)-N that impacted the groundwater under the citrus groves also impacted the groundwater in the adjacent residential area.

Nitrogen retention across a gradient of 15N additions to an unpolluted temperate forest soil in Chile

USGS Publications Warehouse

Perakis, Steven S.; Compton, J.E.; Hedin, L.O.

2005-01-01

Accelerated nitrogen (N) inputs can drive nonlinear changes in N cycling, retention, and loss in forest ecosystems. Nitrogen processing in soils is critical to understanding these changes, since soils typically are the largest N sink in forests. To elucidate soil mechanisms that underlie shifts in N cycling across a wide gradient of N supply, we added 15NH415NO3 at nine treatment levels ranging in geometric sequence from 0.2 kg to 640 kg NA? ha-1A? yr-1 to an unpolluted old-growth temperate forest in southern Chile. We recovered roughly half of tracers in 0-25 cm of soil, primarily in the surface 10 cm. Low to moderate rates of N supply failed to stimulate N leaching, which suggests that most unrecovered 15N was transferred from soils to unmeasured sinks above ground. However, soil solution losses of nitrate increased sharply at inputs > 160 kg NA? ha-1A? yr-1, corresponding to a threshold of elevated soil N availability and declining 15N retention in soil. Soil organic matter (15N in soils at the highest N inputs and may explain a substantial fraction of the 'missing N' often reported in studies of fates of N inputs to forests. Contrary to expectations, N additions did not stimulate gross N cycling, potential nitrification, or ammonium oxidizer populations. Our results indicate that the nonlinearity in N retention and loss resulted directly from excessive N supply relative to sinks, independent of plant-soil-microbial feedbacks. However, N additions did induce a sharp decrease in microbial biomass C:N that is predicted by N saturation theory, and which could increase long-term N storage in soil organic matter by lowering the critical C:N ratio for net N mineralization. All measured sinks accumulated 15N tracers across the full gradient of N supply, suggesting that short-term nonlinearity in N retention resulted from saturation of uptake kinetics, not uptake capacity, in plant, soil, and microbial pools.

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Tightly regulated, high-level expression from controlled copy number vectors based on the replicon of temperate phage N15.

PubMed

Mardanov, Andrey V; Strakhova, Taisia S; Smagin, Vladimir A; Ravin, Nikolai V

2007-06-15

A new Escherichia coli host/vector system has been developed to allow a dual regulation of both the plasmid copy number and gene expression. The new pN15E vectors are low copy number plasmids based on the replicon of temperate phage N15, comprising the repA replicase gene and cB repressor gene, controlling the plasmid copy number. Regulation of pN15E copy number is achieved through arabinose-inducible expression of phage N15 antirepressor protein, AntA, whose gene was integrated into the chromosome of the host strain under control of the PBAD promoter. The host strain also carried phage N15 partition operon, sop, allowing stable inheritance of pN15E vectors in the absence of selection pressure. In the first vector, pN15E4, the same PBAD promoter controls expression of a cloned gene. The second vector, pN15E6, carries the phage T5 promoter with a double lac operator repression module thus allowing independent regulation of promoter activity and copy number. Using the lacZ gene to monitor expression in these vectors, we show that the ratio of induction/repression can be about 7600-fold for pN15E4 and more than 15,000-fold for pN15E6. The low copy number of these vectors ensures very low basal level of expression allowing cloning genes encoding toxic products that was demonstrated by the stable maintenance of a gene encoding a restriction endonuclease in pN15E4. The tight control of transcription and the potential to regulate gene activities quantitatively over wide ranges will open up new approaches in the study of gene function in vivo and controlled expression of heterologous genes.

Identifying carbon sources and trophic position of coral reef fishes using diet and stable isotope (δ15N and δ13C) analyses in two contrasted bays in Moorea, French Polynesia

NASA Astrophysics Data System (ADS)

Letourneur, Y.; Lison de Loma, T.; Richard, P.; Harmelin-Vivien, M. L.; Cresson, P.; Banaru, D.; Fontaine, M.-F.; Gref, T.; Planes, S.

2013-12-01

Stable isotope ratios (δ15N and δ13C) and diet of three fish species, Stegastes nigricans, Chaetodon citrinellus and Epinephelus merra, were analyzed on the fringing coral reefs of two bays that are differentially exposed to river runoff on Moorea Island, French Polynesia. S. nigricans and C. citrinellus relied mostly on turf algae and presented similar trophic levels and δ15N values, whereas E. merra fed on large invertebrates (crabs and shrimps) and had higher trophic levels and δ15N values. Discrepancies existed between stomach content and stable isotope analyses for the relative importance of food items. Bayesian mixing models indicated that sedimented organic matter was also an important additional food for S. nigricans and C. citrinellus, and fishes for E. merra. The main sources of organic matter involved in the food webs ending with these species were algal turfs and surface sediments, while water particulate organic matter was barely used. Significant spatial differences in C and N isotopic ratios for sources and fishes were found within and between bays. Lower 13C and higher 15N values were observed for various compartments of the studied trophic network at the end of each bay than at the entrance. Differences were observed between bays, with organic sources and consumers being, on average, slightly more 13C-depleted and 15N-enriched in Cook's Bay than in Opunohu Bay, linked with a higher mean annual flow of the river at Cook's Bay. Our results suggest that rivers bring continental material into these two bays, which is partly incorporated into the food webs of fringing coral reefs at least close to river mouths. Thus, continental inputs can influence the transfer of organic matter within coral reef food webs depending on the diet of organisms.

Minimum Thickness of Concrete Pavement for the F-15 and C-17 Aircraft

DTIC Science & Technology

2013-07-01

Gravity Portland Cement II Holcim 3.15 Fly Ash C Headwaters 2.59 GGBFS ( Slag ) Admixtures Name Supplier Dosage, Fl. Oz. Type A 322 N BASF 1-3 per cwt... Slag , lb. Comments: 650 Flex Coarse Aggr., lb. 1850 11.06 Fine Aggr., lb. 1225 7.55 Air Content, % 4.5 1.22 Designed by: Andrew Lester Title: Regional

Spin-State-Dependent Ion-Molecule Chemistry as the Origin of N-15 and D Isotopic Anomalies in Primitive Matter.

NASA Technical Reports Server (NTRS)

Wirstrom, E. S.; Charnley, S. B.; Cordiner, M. A.; Milam, S. N.

2012-01-01

Many meteoritic and interplanetary dust particle (IDP) samples contain bulk enhancements and hotspots rich in N-15. Similarly low C(14)N/C(15)N ratios have been observed in numerous comets, An almost constant enrichment factor in comets from disti'nct formation zones in the nebular disk (i.e. both Jupiter Family and Oort Cloud comets), strongly suggests that this fractionation is primordial and was set in the protsolar cloud core. Deuterium enrichment is observed in both meteorites and IDPs

Infrared spectra and anharmonic coupling of proton-bound nitrogen dimers N2-H+-N2, N2-D+-N2, and 15N2-H+-15N2 in solid para-hydrogen.

PubMed

Liao, Hsin-Yi; Tsuge, Masashi; Tan, Jake A; Kuo, Jer-Lai; Lee, Yuan-Pern

2017-08-09

The proton-bound nitrogen dimer, N 2 -H + -N 2 , and its isotopologues were investigated by means of vibrational spectroscopy. These species were produced upon electron bombardment of mixtures of N 2 (or 15 N 2 ) and para-hydrogen (p-H 2 ) or normal-D 2 (n-D 2 ) during deposition at 3.2 K. Reduced-dimension anharmonic vibrational Schrödinger equations were constructed to account for the strong anharmonic effects in these protonated species. The fundamental lines of proton motions in N 2 -H + -N 2 were observed at 715.0 (NH + N antisymmetric stretch, ν 4 ), 1129.6 (NH + N bend, ν 6 ), and 2352.7 (antisymmetric NN/NN stretch, ν 3 ) cm -1 , in agreement with values of 763, 1144, and 2423 cm -1 predicted with anharmonic calculations using the discrete-variable representation (DVR) method at the CCSD/aug-cc-pVDZ level. The lines at 1030.2 and 1395.5 cm -1 were assigned to combination bands involving nν 2 + ν 4 (n = 1 and 2) according to theoretical calculations; ν 2 is the N 2 N 2 stretching mode. For 15 N 2 -H + - 15 N 2 in solid p-H 2 , the corresponding major lines were observed at 710.0 (ν 4 ), 1016.7 (ν 2 + ν 4 ), 1124.3 (ν 6 ), 1384.8 (2ν 2 + ν 4 ), and 2274.9 (ν 3 ) cm -1 . For N 2 -D + -N 2 in solid n-D 2 , the corresponding major lines were observed at 494.0 (ν 4 ), 840.7 (ν 2 + ν 4 ), 825.5 (ν 6 ), and 2356.2 (ν 3 ) cm -1 . In addition, two lines at 762.0 (weak) and 808.3 cm -1 were tentatively assigned to be some modes of N 2 -H + -N 2 perturbed or activated by a third N 2 near the proton.

Heteronuclear transverse and longitudinal relaxation in AX4 spin systems: Application to 15N relaxations in 15NH4+

PubMed Central

Werbeck, Nicolas D.; Hansen, D. Flemming

2014-01-01

The equations that describe the time-evolution of transverse and longitudinal 15N magnetisations in tetrahedral ammonium ions, 15NH4+, are derived from the Bloch-Wangsness-Redfield density operator relaxation theory. It is assumed that the relaxation of the spin-states is dominated by (1) the intra-molecular 15N–1H and 1H–1H dipole–dipole interactions and (2) interactions of the ammonium protons with remote spins, which also include the contribution to the relaxations that arise from the exchange of the ammonium protons with the bulk solvent. The dipole–dipole cross-correlated relaxation mechanisms between each of the 15N–1H and 1H–1H interactions are explicitly taken into account in the derivations. An application to 15N-ammonium bound to a 41 kDa domain of the protein DnaK is presented, where a comparison between experiments and simulations show that the ammonium ion rotates rapidly within its binding site with a local correlation time shorter than approximately 1 ns. The theoretical framework provided here forms the basis for further investigations of dynamics of AX4 spin systems, with ammonium ions in solution and bound to proteins of particular interest. PMID:25128779

Natural Abundance 15 N and 13 C Solid-State NMR Chemical Shifts: High Sensitivity Probes of the Halogen Bond Geometry.

PubMed

Cerreia Vioglio, Paolo; Catalano, Luca; Vasylyeva, Vera; Nervi, Carlo; Chierotti, Michele R; Resnati, Giuseppe; Gobetto, Roberto; Metrangolo, Pierangelo

2016-11-14

Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a versatile characterization technique that can provide a plethora of information complementary to single crystal X-ray diffraction (SCXRD) analysis. Herein, we present an experimental and computational investigation of the relationship between the geometry of a halogen bond (XB) and the SSNMR chemical shifts of the non-quadrupolar nuclei either directly involved in the interaction ( 15 N) or covalently bonded to the halogen atom ( 13 C). We have prepared two series of X-bonded co-crystals based upon two different dipyridyl modules, and several halobenzenes and diiodoalkanes, as XB-donors. SCXRD structures of three novel co-crystals between 1,2-bis(4-pyridyl)ethane, and 1,4-diiodobenzene, 1,6-diiodododecafluorohexane, and 1,8-diiodohexadecafluorooctane were obtained. For the first time, the change in the 15 N SSNMR chemical shifts upon XB formation is shown to experimentally correlate with the normalized distance parameter of the XB. The same overall trend is confirmed by density functional theory (DFT) calculations of the chemical shifts. 13 C NQS experiments show a positive, linear correlation between the chemical shifts and the C-I elongation, which is an indirect probe of the strength of the XB. These correlations can be of general utility to estimate the strength of the XB occurring in diverse adducts by using affordable SSNMR analysis. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Monitoring the refinement of crystal structures with {sup 15}N solid-state NMR shift tensor data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalakewich, Keyton; Eloranta, Harriet; Harper, James K.

The {sup 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 {sup 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 thanmore » 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 {sup 15}N tensors at natural abundance is challenging and this limitation is overcome by improved {sup 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 {sup 15}N tensors are at least 5 times more sensitive to crystal structure than {sup 13}C tensors due to nitrogen’s greater polarizability and larger range of chemical shifts.« less

Comparing isotope signatures of prey fish: does gut removal affect δ13C or δ15N?

USGS Publications Warehouse

Chipps, Steven R.; Fincel, Mark J.; VanDeHey, Justin A.; Wuestewald, Andrew

2011-01-01

Stable isotope analysis is a quick and inexpensive method to monitor the effects of food web changes on aquatic communities. Traditionally, whole specimens have been used when determining isotope composition of prey fish or age-0 recreational fishes. However, gut contents of prey fish could potentially alter isotope composition of the specimen, especially when recent foraging has taken place or when the gut contains non-assimilated material that would normally pass through fishes undigested. To assess the impacts of gut content on prey fish isotope signatures, we examined the differences in isotopic variation of five prey fish species using whole fish, whole fish with the gut contents removed, and dorsal muscle only. We found significant differences in both δ15N and δ13C between the three tissue treatments. In most cases, muscle tissue was enriched compared to whole specimens or gut-removed specimens. Moreover, differences in mean δ15N within a species were up to 2‰ among treatments. This would result in a change of over half a trophic position (TP) based on a 3.4‰ increase per trophic level. However, there were no apparent relationships between tissue isotope values in fish with increased gut fullness (more prey tissue present). We suggest that muscle tissue should be used as the standard tissue for determining isotope composition of prey fish or age-0 recreational fishes, especially when determining enrichment for mixing models, calculating TP, or constructing aquatic food webs.

Site-specific 15N isotopic signatures of abiotically produced N2O

NASA Astrophysics Data System (ADS)

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

2014-08-01

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

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.

15 CFR 8c.49 - Program accessibility: Discrimination prohibited.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Program accessibility: Discrimination prohibited. 8c.49 Section 8c.49 Commerce and Foreign Trade Office of the Secretary of Commerce ENFORCEMENT OF NONDISCRIMINATION ON THE BASIS OF HANDICAP IN PROGRAMS OR ACTIVITIES CONDUCTED BY THE DEPARTMENT OF COMMERCE § 8c.49...

15 CFR 8c.30 - General prohibitions against discrimination.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false General prohibitions against discrimination. 8c.30 Section 8c.30 Commerce and Foreign Trade Office of the Secretary of Commerce ENFORCEMENT OF NONDISCRIMINATION ON THE BASIS OF HANDICAP IN PROGRAMS OR ACTIVITIES CONDUCTED BY THE DEPARTMENT OF COMMERCE § 8c.30...

Multiyear fate of a 15 N tracer in a mixed deciduous forest: retention, redistribution, and differences by mycorrhizal association.

PubMed

Goodale, Christine L

2017-02-01

The impact of atmospheric nitrogen deposition on forest ecosystems depends in large part on its fate. Past tracer studies show that litter and soils dominate the short-term fate of added 15 N, yet few have examined its longer term dynamics or differences among forest types. This study examined the fate of a 15 N-NO3- tracer over 5-6 years in a mixed deciduous stand that was evenly composed of trees with ectomycorrhizal and arbuscular mycorrhizal associations. The tracer was expected to slowly mineralize from its main initial fate in litter and surface soil, with some 15 N moving to trees, some to deeper soil, and some net losses. Recovery of added 15 N in trees and litterfall totaled 11.3% both 1 and 5-6 years after the tracer addition, as 15 N redistributed from fine and especially coarse roots into cumulative litterfall and small accumulations in woody tissues. Estimates of potential carbon sequestration from tree 15 N recovery amounted to 12-14 kg C per kg of N deposition. Tree 15 N acquisition occurred within the first year after the tracer addition, with no subsequent additional net transfer of 15 N from detrital to plant pools. In both years, ectomycorrhizal trees gained 50% more of the tracer than did trees with arbuscular mycorrhizae. Much of the 15 N recovered in wood occurred in tree rings formed prior to the 15 N addition, demonstrating the mobility of N in wood. Tracer recovery rapidly decreased over time in surface litter material and accumulated in both shallow and deep soil, perhaps through mixing by earthworms. Overall, results showed redistribution of tracer 15 N through trees and surface soils without any losses, as whole-ecosystem recovery remained constant between 1 and 5-6 years at 70% of the 15 N addition. These results demonstrate the persistent ecosystem retention of N deposition even as it redistributes, without additional plant uptake over this timescale. © 2016 John Wiley & Sons Ltd.

13C and 15N CP/MAS, 1H-15N SCT CP/MAS and FTIR spectroscopy as tools for qualitative detection of the presence of zwitterionic and non-ionic forms of ansa-macrolide 3-formylrifamycin SV and its derivatives in solid state.

PubMed

Przybylski, Piotr; Pyta, Krystian; Klich, Katarzyna; Schilf, Wojciech; Kamieński, Bohdan

2014-01-01

(13)C, (15)N CP/MAS, including (1)H-(13)C and (1)H-(15)N short contact time CP/MAS experiments, and FTIR methods were applied for detailed structural characterization of ansa-macrolides as 3-formylrifamycin SV (1) and its derivatives (2-6) in crystal and in powder forms. Although HPLC chromatograms for 2/CH3 OH and 2/CH3 CCl3 were the same for rifampicin crystals dissolved in respective solvents, the UV-vis data recorded for them were different in 300-375 nm region. Detailed solid state (13)C and (15)N CP/MAS NMR and FTIR studies revealed that rifampicin (2), in contrast to 3-formylrifamycin SV (1) and its amino derivatives (3-6), can occur in pure non-ionic or zwitterionic forms in crystal and in pure these forms or a mixture of them in a powder. Multinuclear CP/MAS and FTIR studies demonstrated also that 3-6 derivatives were present exclusively in pure zwitterionic forms, both in powder and in crystal. On the basis of the solid state NMR and FTIR studies, two conformers of 3-formylrifamycin SV were detected in powder form due to the different orientations of carbonyl group of amide moiety. The PM6 molecular modeling at the semi-empirical level of theory, allowed visualization the most energetically favorable non-ionic and zwitterionic forms of 1-6 antibiotics, strongly stabilized via intramolecular H-bonds. FTIR studies indicated that the originally adopted forms of these type antibiotics in crystal or in powder are stable in standard laboratory conditions in time. The results presented point to the fact that because of a possible presence of two forms of rifampicin (compound 2), quantification of the content of this antibiotic in relevant pharmaceuticals needs caution. Copyright © 2013 John Wiley & Sons, Ltd.

[Dynamics of amino acid and protein metabolism in laying hens after the administration of 15N-labeled wheat protein. 11. Incorporation of 15N in the tissues and the amino acids of the muscles].

PubMed

Gruhn, K; Zander, R

1989-03-01

Over a period of 4 days 12 colostomized laying hens daily received 36 g 15N labelled wheat with 15N excess (15N') of 14.37 atom-% together with a conventional feed mixture for laying hens. The labelling of the lysine N in the wheat was 13.58 atom-%, that of histidine N 14.38 and that of arginine 15N' 13.63 atom-% 15N'. Three hens each were butchered 12, 36, 60 and 108 h after the last 15N' feeding. The first three hens did not receive any feed before being butchered. The following three hens each received the unlabelled feed ration for another 1, 2 or 4 days resp. after the main period until they were butchered. The total of skeleton muscles, the heart and the stomach muscle (without inner skin) of each hen were combined into one sample, cut thinly, drenched with fluid nitrogen and pulverized. N, 15N' and the basic and non-basic amino acids as well as their 15N' were determined in the individual samples. In contrast to the organs, the proteins in the muscle tissue have a long half life so that a slight decrease of atom-% 15N' in the muscles could only be detected after 108 h. The 14N and 15N' quota of the non-basic amino acids in the total nitrogen of the muscles is 50%. The 14N quota of the basic amino acids is 30% and the 15N' quota only 22.5% in the total muscle N. The heavy nitrogen of the free lysine in the TCA soluble N fraction is hardly detectable 36 h and 60 h after the last 15N' supply and not at all after 108 h. In contrast to this, the other two free basic amino acids remain significantly higher labelled in dependence on the last butchering time.

Isolated spinach ribulose-1,5-bisphosphate carboxylase/oxgenase large subunit .epsilon. n-methyltransferase and method of inactivating ribulose-1,5-bishosphatase .epsilon. n-methyltransferase activity

DOEpatents

Houtz, Robert L.

2001-01-01

The gene sequence for ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) large subunit (LS) .sup..epsilon. N-methyltansferase (protein methylase III or Rubisco LSMT) from a plant which has a des(methyl) lysyl residue in the LS is disclosed. In addition, the full-length cDNA clones for Rubisco LSMT are disclosed. Transgenic plants and methods of producing same which have the Rubisco LSMT gene inserted into the DNA are also provided. Further, methods of inactivating the enzymatic activity of Rubisco LSMT are also disclosed.

Alkaline hydrolysis/polymerization of 2,4,6-Trinitrotoluene:  Characterization of products by 13C and 15N NMR

USGS Publications Warehouse

Thorn, Kevin A.; Thorne, Philip G.; Cox, Larry 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% sp3- and 86% sp2-hybridized, the precipitate fraction from hydrolysis of unlabeled TNT contained 33% sp3- and 67% sp2-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

Adsorption and wetting characterization of hydrophobic SBA-15 silicas.

PubMed

Bernardoni, Frank; Fadeev, Alexander Y

2011-04-15

This work describes adsorption and wetting characterization of hydrophobic ordered mesoporous silicas (OMSs) with the SBA-15 motif. Three synthetic approaches to prepare hydrophobic SBA-15 silicas were explored: grafting with (1) covalently-attached monolayers (CAMs) of C(n)H(2)(n+1)Si(CH(3))(2)N(CH(3))(2), (2) self-assembled monolayers (SAMs) of C(n)H(2)(n+1)Si(OEt)(3), and (3) direct ("one-pot") co-condensation of TEOS with C(n)H(2)(n+1)Si(OEt)(3) in presence of P123 (n=1-18). The materials prepared were characterized by nitrogen adsorption, TEM, and chemical analysis. The surface properties of the materials were assessed by water contact angles (CAs) and by BET C constants. The results showed that, while loadings of the alkyl groups (%C) were comparable, the surface properties and pore ordering of the materials prepared through different methods were quite different. The best quality hydrophobic surfaces were prepared for SBA-15 grafted with CAMs of alkylsilanes. For these materials, the water CAs were above ∼120°/100° (adv/rec) and BET C constants were in the range of ∼15-25, indicating uniform low-energy surfaces of closely packed alkyl groups on external and internal surfaces of the pores respectively. Moreover, surfaces grafted with the long-chained (C(12)-C(18)) silanes showed super-hydrophobic behavior (CAs∼150-180°) and extremely low adhesion for water. The pore uniformity of parental SBA-15 was largely preserved and the pore volume and pore diameter were consistent with the formation of a single layer of alkylsilyl groups inside the pores. Post-synthesis grafting of SBA-15 with SAMs worked not as well as CAMs: the surfaces prepared demonstrated lower water CAs and higher BET C constants, thereby indicating a small amount of accessible polar groups (Si-OH) related to packing constrains for SAMs supported on highly curved surfaces of mesopores. The co-condensation method produced substantially more disordered materials and less hydrophobic

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.

15. Photocopy of photograph (from 'The California Advertiser', c. 1880) ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

15. Photocopy of photograph (from 'The California Advertiser', c. 1880) EXTERIOR, GENERAL VIEW OF MISSION AND CONVENTO, C. 1880 - Mission San Francisco Solano de Sonoma, First & Spain Streets, Sonoma, Sonoma County, CA

Dark Septate Endophytic Fungi Increase Green Manure-15N Recovery Efficiency, N Contents, and Micronutrients in Rice Grains.

PubMed

Vergara, Carlos; Araujo, Karla E C; Urquiaga, Segundo; Santa-Catarina, Claudete; Schultz, Nivaldo; da Silva Araújo, Ednaldo; de Carvalho Balieiro, Fabiano; Xavier, Gustavo R; Zilli, Jerri É

2018-01-01

An understanding of the interaction between rice and dark septate endophytic (DSE) fungi, under green fertilization, may lead to sustainable agricultural practices. Nevertheless, this interaction is still poorly understood. Therefore, in this study, we aimed to evaluate the accumulation of macro- and micronutrients, dry matter, and protein and N recovery efficiency from Canavalia ensiformis (L.)- 15 N in rice inoculated with DSE fungi. An experiment under greenhouse conditions was conducted in a randomized complete block design comprising split-plots, with five replicates of rice plants potted in non-sterilized soil. Rice (Piauí variety) seedlings were inoculated with DSE fungi, A101 and A103, or left uninoculated (control) and transplanted into pots containing 12 kg of soil, which had previously been supplemented with dry, finely ground shoot biomass of C. ensiformis enriched with 2.15 atom % 15 N. Two collections were performed in the experiment: one at 54 days after transplanting (DAT) and one at 130 DAT (at maturation). Growth indicators (at 54 DAT), grain yield, nutrient content, recovery efficiency, and the amount of N derived from C. ensiformis were quantified. At 54 DAT, the N content, chlorophyll content, and plant height of inoculated plants had increased significantly compared with the control, and these plants were more proficient in the use of N derived from C. ensiformis . At maturation, plants inoculated with A103 were distinguished by the recovery efficiency and amount of N derived from C. ensiformis and N content in the grain and shoot being equal to that in A101 inoculation and higher than that in the control, resulting in a higher accumulation of crude protein and dry matter in the full grain and panicle of DSE-rice interaction. In addition, Fe and Ni contents in the grains of rice inoculated with these fungi doubled with respect to the control, and in A103 inoculation, we observed Mn accumulation that was three times higher than in the other

Isotopic discrimination of stable isotopes of nitrogen (δ15N) and carbon (δ13C) in a host-specific holocephalan tapeworm.

PubMed

Navarro, J; Albo-Puigserver, M; Coll, M; Saez, R; Forero, M G; Kutcha, R