scholarly journals Evidence of Substantial Carbon Isotope Fractionation among Substrate, Inorganic Carbon, and Biomass during Aerobic Mineralization of 1,2-Dichloroethane byXanthobacter autotrophicus

2000 ◽  
Vol 66 (11) ◽  
pp. 4870-4876 ◽  
Author(s):  
D. Hunkeler ◽  
R. Aravena
Keyword(s):  
Carbon Isotope ◽  
Isotope Effect ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Inorganic Carbon ◽  
Mechanistic Model ◽  
Fractionation Factor ◽  
Carbon Isotope Fractionation ◽  
Kinetic Isotope ◽  
Factor Α

ABSTRACT Carbon isotope fractionation during aerobic mineralization of 1,2-dichloroethane (1,2-DCA) by Xanthobacter autotrophicusGJ10 was investigated. A strong enrichment of 13C in residual 1,2-DCA was observed, with a mean fractionation factor α ± standard deviation of 0.968 ± 0.0013 to 0.973 ± 0.0015. In addition, a large carbon isotope fractionation between biomass and inorganic carbon occurred. A mechanistic model that links the fractionation factor α to the rate constants of the first catabolic enzyme was developed. Based on the model, it was concluded that the strong enrichment of 13C in 1,2-DCA arises because the first irreversible step of the initial enzymatic transformation of 1,2-DCA consists of an SN2 nucleophilic substitution. SN2 reactions are accompanied by a large kinetic isotope effect. The substantial carbon isotope fractionation between biomass and inorganic carbon could be explained by the kinetic isotope effect associated with the initial 1,2-DCA transformation and by the metabolic pathway of 1,2-DCA degradation. Carbon isotope fractionation during 1,2-DCA mineralization leads to 1,2-DCA, inorganic carbon, and biomass with characteristic carbon isotope compositions, which may be used to trace the process in contaminated environments.

scholarly journals Anaerobic methane oxidation by nitrate: kinetic isotope effect

2018 ◽  
Vol 10 (1) ◽  
Author(s):  
Vasiliy A. Vavilin
Keyword(s):  
Dynamic Model ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Effect ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Stable Carbon Isotopes ◽  
Stable Carbon ◽  
Fractionation Factor ◽  
Kinetic Isotope

The ratio of stable carbon isotopes (13C/12C) in different environments serves as a significant limitation in estimating the global balance of methane [Hornibrook et al., 2000]. In this case, the value of 13C/12C largely depends on the kinetic isotope effect associated with the metabolism of microorganisms that produce and consume CH4. The article suggests a dynamic model of the processes of methane formation and its anaerobic oxidation with nitrate by methanotrophic denitrifying microorganisms (DAOM), which allowed estimating the fractionation factor of stable carbon isotopes. In the experiment with peat from the minerotrophic bog [Smemo, Yavitt, 2007], the dynamics of the amount of methane and was measured. The dynamic model showed that the introduction of nitrate leads to a slow decrease in the partial pressure of methane. Since methane in the DAOM process is a substrate, methane is enriched with heavier carbon 13C in the system under study. This leads to an increase in the value . The carbon isotope fractionation factor during methane oxidation with nitrate was equal to 1.018 and comparable with the fraction of carbon isotope fractionation in the process of acetoclastic methanogenesis (1.01). Model calculations have shown that during incubation the apparent fractionation factor of carbon isotopes with the simultaneous formation of methane and DAOM slowly decreases. The ratio of 13C/12C isotopes in dissolved and gaseous methane practically does not differ. The model showed that an increase in the initial concentration of nitrate increases the rate of DAOM, which leads to a decrease in the concentration of dissolved methane. In this case, the value of 13C/12C increases. In field studies, Shi et al. (2017) showed that the presence of DAOM in peat bogs in which fertilizers penetrate can be controlled by the amount of nitrate used and the depth of penetration into the anoxic layer. Two MATLAB files describing DAOM are attached to the article.

Can algal photosynthetic inorganic carbon isotope fractionation be predicted in lakes using existing models?

2006 ◽  
Vol 68 (2) ◽  
pp. 142-153 ◽  
Author(s):  
Darren L. Bade ◽  
Michael L. Pace ◽  
Jonathan J. Cole ◽  
Stephen R. Carpenter
Keyword(s):  
Carbon Isotope ◽  
Isotope Fractionation ◽  
Inorganic Carbon ◽  
Carbon Isotope Fractionation

Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

2011 ◽  
Vol 75 (10) ◽  
pp. 2696-2707 ◽  
Author(s):  
Yunyan Ni ◽  
Qisheng Ma ◽  
Geoffrey S. Ellis ◽  
Jinxing Dai ◽  
Barry Katz ◽  
...  
Keyword(s):  
Natural Gas ◽  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope

scholarly journals Distribution of lipid biomarkers and carbon isotope fractionation in contrasting trophic environments of the South East Pacific

2008 ◽  
Vol 5 (3) ◽  
pp. 949-968 ◽  
Author(s):  
I. Tolosa ◽  
J.-C. Miquel ◽  
B. Gasser ◽  
P. Raimbault ◽  
C. Goyet ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Growth Rates ◽  
Isotope Fractionation ◽  
Lipid Biomarkers ◽  
Co2 Uptake ◽  
The South ◽  
Fractionation Factor ◽  
Carbon Isotope Fractionation ◽  
East Pacific ◽  
Eukaryotic Phytoplankton

Abstract. The distribution of lipid biomarkers and their stable carbon isotope composition was investigated on suspended particles from different contrasting trophic environments at six sites in the South East Pacific. High algal biomass with diatom-related lipids (24-methylcholesta-5,24(28)-dien-3β-ol, C25 HBI alkenes, C16:4 FA, C20:5 FA) was characteristic in the upwelling zone, whereas haptophyte lipids (long-chain (C37-C39) unsaturated ketones) were proportionally most abundant in the nutrient-poor settings of the centre of the South Pacific Gyre and on its easter edge. The dinoflagellate–sterol, 4α-23,24-trimethylcholest-22(E)-en-3β-ol, was a minor contributor in all of the studied area and the cyanobacteria-hydrocarbon, C17n-alkane, was at maximum in the high nutrient low chlorophyll regime of the subequatorial waters near the Marquesas archipelago. The taxonomic and spatial variability of the relationships between carbon photosynthetic fractionation and environmental conditions for four specific algal taxa (diatoms, haptophytes, dinoflagellates and cyanobacteria) was also investigated. The carbon isotope fractionation factor (εp) of the 24-methylcholesta-5,24(28)-dien-3β-ol diatom marker, varied over a range of 16% along the different trophic systems. In contrast, εp of dinoflagellate, cyanobacteria and alkenone markers varied only by 7–10‰. The low fractionation factors and small variations between the different phytoplankton markers measured in the upwelling area likely reveals uniformly high specific growth rates within the four phytoplankton taxa, and/or that transport of inorganic carbon into phytoplankton cells may not only occur by diffusion but also by other carbon concentrating mechanisms (CCM). In contrast, in the oligotrophic zone, i.e. gyre and eastgyre, relatively high εp values, especially for the diatom marker, indicate diffusive CO2 uptake by the eukaryotic phytoplankton. At these nutrient-poor sites, the lower εp values for haptophytes, dinoflagellates and cyanobacteria indicate higher growth rates or major differences on the carbon uptake mechanisms compared to diatoms.

scholarly journals CO2-dependent carbon isotope fractionation in dinoflagellates relates to their inorganic carbon fluxes

2016 ◽  
Vol 481 ◽  
pp. 9-14 ◽  
Author(s):  
Mirja Hoins ◽  
Tim Eberlein ◽  
Dedmer B. Van de Waal ◽  
Appy Sluijs ◽  
Gert-Jan Reichart ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Isotope Fractionation ◽  
Inorganic Carbon ◽  
Carbon Fluxes ◽  
Carbon Isotope Fractionation

Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream

2008 ◽  
Vol 22 (14) ◽  
pp. 2410-2423 ◽  
Author(s):  
Daniel H. Doctor ◽  
Carol Kendall ◽  
Stephen D. Sebestyen ◽  
James B. Shanley ◽  
Nobuhito Ohte ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Isotope ◽  
Isotope Fractionation ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Headwater Stream ◽  
Carbon Isotope Fractionation

Untersuchungen zur Reaktion der Alkoholdehydrogenase mit Tritium -markierten Substraten

1966 ◽  
Vol 21 (6) ◽  
pp. 547-551 ◽  
Author(s):  
Dieter Palm
Keyword(s):  
Alcohol Dehydrogenase ◽  
Isotope Effect ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Retention Volume ◽  
Deae Cellulose ◽  
Yeast Alcohol Dehydrogenase ◽  
Kinetic Isotope ◽  
Direct Indication ◽  
Rate Controlling Step

The temperature dependence of the kinetic isotope effect of NADH-T in the acetaldehyde reduction by yeast alcohol dehydrogenase showed a discontinuity which can be explained by a change of the rate controlling step. The magnitude of the isotope effect is largely dependent on the nature of the unlabelled aldehyde and increases in the order acetaldehyde, propionaldehyde, butyraldehyde. This is a direct indication that the second substrate influences the nature of the H-transfer from NADH. During substrate binding the aldehyde causes an effect on the transferable H of NADH. This effect is less pronounced for the less effective substrates propionaldehyde and butyraldehyde. Comparing the homologue aldehydes the small size of the isotope effect gives an indication that acetaldehyde is the natural substrate of yeast alcohol dehydrogenase.The purification of NADH-T on DEAE-Cellulose is connected with isotope fractionation which amounts to 0.4 — 1.1% of retention volume.

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