Improved precision of coupled δ13C and δ15N measurements from single samples using an elemental analyzer/isotope ratio mass spectrometer combination with a post‐column six‐port valve and selective CO2 trapping; improved halide robustness of the combustion reactor using CeO2

Brooks, P. D.; Geilmann, Heike; Werner, Roland A.; Brand, Willi A.

doi:10.1002/rcm.1134

Cited by 63 publications

(59 citation statements)

References 7 publications

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“…All samples were analyzed at the University of California at Berkeley Center for Stable Isotope Biogeochemistry. δ 15 N and %N were determined by using a Europa 2020 mass spectrometer coupled to an automatic elemental analyzer (48). The isotopic abundance parameters are defined as follows: Calculations.…”

Section: Methodsmentioning

confidence: 99%

Mechanism for nitrogen isotope fractionation during ammonium assimilation by Escherichia coli K12

Inwood

Hayes

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Organisms that use ammonium as the sole nitrogen source discriminate between [ 15 N] and [ 14 N] ammonium. This selectivity leaves an isotopic signature in their biomass that depends on the external concentration of ammonium. To dissect how differences in discrimination arise molecularly, we examined a wild-type (WT) strain of Escherichia coli K12 and mutant strains with lesions affecting ammonium-assimilatory proteins. We used isotope ratio mass spectrometry (MS) to assess the nitrogen isotopic composition of cell material when the strains were grown in batch culture at either high or low external concentrations of NH 3 (achieved by controlling total NH 4 Cl and pH of the medium). At high NH 3 (≥0.89 μM), discrimination against the heavy isotope by the WT strain (−19.2‰) can be accounted for by the equilibrium isotope effect for dissociation of NH 4 + to NH 3 + H + . NH 3 equilibrates across the cytoplasmic membrane, and glutamine synthetase does not manifest an isotope effect in vivo. At low NH 3 (≤0.18 μM), discrimination reflects an isotope effect for the NH 4 + channel AmtB (−14.1‰). By making E. coli dependent on the low-affinity ammonium-assimilatory pathway, we determined that biosynthetic glutamate dehydrogenase has an inverse isotope effect in vivo (+8.8‰). Likewise, by making unmediated diffusion of NH 3 across the cytoplasmic membrane rate-limiting for cell growth in a mutant strain lacking AmtB, we could deduce an in vivo isotope effect for transport of NH 3 across the membrane (−10.9‰). The paper presents the raw data from which our conclusions were drawn and discusses the assumptions underlying them.

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Section: Methodsmentioning

confidence: 99%

Mechanism for nitrogen isotope fractionation during ammonium assimilation by Escherichia coli K12

Inwood

Hayes

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…The instrument was modified in two ways to reduce background and improve sensitivity of nitrogen isotope analysis. First, an automated six-port valve fitted with an ascarite trap was installed in between the EA and IRMS in order to trap CO 2 during elution of the N 2 peak and therefore reduce formation of CO in the source and variation in mass 28, 29, and 30 backgrounds, as done by Brooks et al (2003). Second, the IRMS was set to high-gain amplification to increase signal as done by Osburn and St-Jean (2007).…”

Section: Sampling and Analytical Methodsmentioning

confidence: 99%

Late Miocene through early Pleistocene nutrient utilization and export production in the Antarctic Zone of the Southern Ocean

Billups

Aufdenkampe

Hays

2013

Global and Planetary Change

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“…To determine carbon isotope ratios (δ 13 C) and nitrogen concentrations, the most abundant species were sampled at Chamau (Agrostis stolonifera L., Alopecurus pratensis L., (Brooks et al, 2003), a ConFlo III (Werner et al, 1999) and an additional Nafion-trap backed by a conventional Mg(ClO 4 ) 2 -trap followed by a 4-port valve between reduction tube and GC column. Post-run offline calculations (blank, offset and possibly drift corrections) were performed to assign the final δ-values on the V-PDB and AIR-N 2 scales according to Werner and Brand (2001).…”

Section: Carbon Isotope and Nitrogen Concentration Measurementsmentioning

confidence: 99%

Response of temperate grasslands at different altitudes to simulated summer drought differed but scaled with annual precipitation

2009

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Abstract.Water is an important resource for plant life. Since climate scenarios for Switzerland predict an average reduction of 20% in summer precipitation until 2070, understanding ecosystem responses to water shortage, e.g. in terms of plant productivity, is of major concern. Thus, we tested the effects of simulated summer drought on three managed grasslands along an altitudinal gradient in Switzerland from 2005 to 2007, representing typical management intensities at the respective altitude. We assessed the effects of experimental drought on above-and below-ground productivity, stand structure (LAI and vegetation height) and resource use (carbon and water). Responses of community above-ground productivity to reduced precipitation input differed among the three sites but scaled positively with total annual precipitation at the sites (R 2 =0.85). Annual community above-ground biomass productivity was significantly reduced by summer drought at the alpine site receiving the least amount of annual precipitation, while no significant decrease (rather an increase) was observed at the pre-alpine site receiving highest precipitation amounts in all three years. At the lowland site (intermediate precipitation sums), biomass productivity significantly decreased in response to drought only in the third year, after showing increased abundance of a drought tolerant weed species in the second year. No significant change in below-ground biomass productivity was observed at any of the sites in response to simulated summer drought. However, vegetation carbon isotope ratios increased under drought conditions, indicating an increase in water use efficiency. We conclude that there is no general drought response of Swiss grasslands, but that sites with lower annual precipitation seem to be more vulnerable to summer drought Correspondence to: A. K. Gilgen (anna.gilgen@ips.unibe.ch) than sites with higher annual precipitation, and thus sitespecific adaptation of management strategies will be needed, especially in regions with low annual precipitation.

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Improved precision of coupled δ¹³C and δ¹⁵N measurements from single samples using an elemental analyzer/isotope ratio mass spectrometer combination with a post‐column six‐port valve and selective CO₂ trapping; improved halide robustness of the combustion reactor using CeO₂

Cited by 63 publications

References 7 publications

Mechanism for nitrogen isotope fractionation during ammonium assimilation by Escherichia coli K12

Mechanism for nitrogen isotope fractionation during ammonium assimilation by Escherichia coli K12

Late Miocene through early Pleistocene nutrient utilization and export production in the Antarctic Zone of the Southern Ocean

Response of temperate grasslands at different altitudes to simulated summer drought differed but scaled with annual precipitation

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