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1.
J Environ Manage ; 258: 110030, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31929066

RESUMO

The greenhouse effect is closely related to elevated atmospheric CO2 concentrations and therefore, carbon capture and storage (CCS) has attracted attention worldwide as a method for preventing the release of CO2 into the atmosphere, which highlights the importance of monitoring CO2 released from subsurface deposits. In this study, CO2 gas with a δ13C value of -30‰ was injected into soil through pipes installed at a depth of 2.5 m, and samples of CO2 gas released from the soil surface and three soil depths were collected from September 2015 to March 2016 to estimate subsurface CO2 movement. Before and after CO2 injection, the δ13C values of CO2 released from the soil surface ranged from -24.5 to -13.4‰ (average -20.2 ± 2.1‰, n = 25) and from -31.6 to -11.9‰ (average -23.2 ± 4.3‰, n = 49), respectively. The results indicated that the leakage of injected CO2 was successfully detected at the surface. The δ13C values were visualized using an interpolation map to estimate the subsurface CO2 distribution, which confirmed that diffusion of the injected CO2 gas extended to the soil zone where CO2 was not injected. Additionally, variation in δ13C for soil CO2 was detected at the three soil depths (15, 30, and 60 cm), where the values were -16.1, -20.0, and -22.1‰, respectively. Different δ13C values horizontally and vertically indicated that soil heterogeneity led to different CO2 migration pathways and rates. We suggest that the carbon isotope ratio of CO2 is an effective tool for concurrently monitoring CO2 leakage on and under surface in a soil zone if a thorough baseline study is carried out in the field.


Assuntos
Dióxido de Carbono , Solo , Atmosfera , Isótopos de Carbono , República da Coreia
2.
J Agric Food Chem ; 68(6): 1546-1554, 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-31986047

RESUMO

Bromoxynil is an increasingly applied nitrile herbicide. Under aerobic conditions, hydration, nitrilation, or hydroxylation of the nitrile group commonly occurs, whereas under anaerobic conditions reductive dehalogenation is common. This work studied the isotope effects associated with these processes by soil cultures. The aerobic soil enrichment culture presented a significant increase in Stenotrophomonas, Pseudomonas, Chryseobacterium, Achromobacter, Azospirillum, and Arcticibacter, and degradation products indicated that nitrile hydratase was the dominant degradation route. The anaerobic culture was dominated by Proteobacteria and Firmicutes phyla with a significant increase in Dethiosulfatibacter, and degradation products indicated reductive debromination as a major degradation route. Distinct dual-isotope trends (δ13C, δ15N) were determined for the two routes: a strong inverse nitrogen isotope effect (εN = 10.56 ± 0.36‰) and an insignificant carbon isotope effect (εC = 0.37 ± 0.36‰) for the aerobic process versus a negligible effect for both elements in the anaerobic process. These trends differ from formerly reported trends for the photodegradation of bromoxynil and enable one to distinguish between the processes in the field.


Assuntos
Bactérias/metabolismo , Herbicidas/química , Nitrilos/química , Poluentes do Solo/química , Aerobiose , Anaerobiose , Biodegradação Ambiental , Isótopos de Carbono/química , Isótopos de Nitrogênio/química , Solo/química , Microbiologia do Solo
3.
J Environ Radioact ; 213: 106156, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31983456

RESUMO

Conventional beta counting technique based radiocarbon dating facility at Birbal Sahni Institute of Palaeosciences- Lucknow was established in 1974 (Rajagopalan,1978). In 2017-18, BSIP received an upgrade with installation of an Automated Graphitization Equipment (AGE) coupled with an Elemental Analyser, a Carbonate Handling System (CHS) along with an in-line stable isotope mass-spectrometer (IRMS). Using this combo, stable Carbon (C), Nitrogen (N) and Sulfur (S) isotopic measurements could be carried out in both organic and inorganic type samples followed by graphite preparation (~1 mg) for 14C measurement by Accelerator Mass Spectrometry (AMS). This communication addresses details of pre-processing, processing, and quality checks adopted for achieving acceptable and demonstrable accuracy and precision of measured Δ14C, δ13C, δ15N, and δ34S measurements. Information regarding chemical preparation of samples for aforesaid stable and radio isotopic analysis is provided in succinct manner. Overall, average coefficient of variation determining precision of our graphite powders for 14C measurements is ~2.4%. The mean age of blank (anthracite) processed using established EA-IRMS-AGE unit comes as 42,100 ± 300 years.


Assuntos
Espectrometria de Massas , Isótopos de Carbono , Grafite , Índia , Isótopos , Monitoramento de Radiação
4.
Food Chem ; 313: 126093, 2020 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31927205

RESUMO

Multivariate stable isotope analysis combined with chemometrics was used to investigate and discriminate rice samples from six rice producing provinces in China (Heilongjiang, Jilin, Jiangsu, Zhejiang, Hunan and Guizhou) and four other Asian rice producing countries (Thailand, Malaysia, Philippines, and Pakistan). The stable isotope characteristics were analyzed for rice of different species cultivated with varied farming methods at different altitudes and latitudes/longitudes. The index groups of δ13C, δ15N, δ18O, 207/206Pb and 208/207Pb were screened and established for the selected samples with different geographical features by means of principal component analysis (PCA) and discriminant analysis (DA), which would provide a sound technical solution for rice traceability and serve as a template for further research on the traceability of other agricultural products, especially plant-derived products.


Assuntos
Marcação por Isótopo , Oryza/química , Isótopos de Carbono/análise , China , Análise Discriminante , Isótopos/análise , Chumbo/análise , Malásia , Espectrometria de Massas , Isótopos de Nitrogênio/análise , Oryza/metabolismo , Paquistão , Filipinas , Análise de Componente Principal , Tailândia
5.
Chemphyschem ; 21(3): 251-256, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31922367

RESUMO

The promise of hyperpolarized glucose as a non-radioactive imaging agent capable of reporting on multiple metabolic routes has led to recent advances in its dissolution-DNP (dDNP) driven polarization using UV-light induced radicals and trityl radicals at high field (6.7 T) and 1.1 K. However, most preclinical dDNP polarizers operate at the field of 3.35 T and 1.4-1.5 K. Minute amounts of Gd3+ complexes have shown large improvements in solid-state polarization, which can be translated to improved hyperpolarization in solution. However, this Gd3+ effect seems to depend on magnetic field strength, metal ion concentration, and sample formulation. The effect of varying Gd3+ concentrations at 3.35 T has been described for 13 C-labeled pyruvic acid and acetate. However, it has not been studied for other compounds at this field. The results presented here suggest that Gd3+ doping can lead to various concentration and temperature dependent effects on the polarization of [13 C6 ,2 H7 ]glucose, not necessarily similar to the effects observed in pyruvic acid or acetate in size or direction. The maximal polarization for [13 C6 ,2 H7 ]glucose appears to be at a Gd3+ concentration of 2 mM, when irradiating for more than 2 h at the negative maximum of the DNP intensity profile. Surprisingly, for shorter irradiation times, higher polarization levels were determined at 1.50 K compared to 1.45 K, at a [Gd3+ ]=1.3 mM. This was explained by the build-up time constant and maximum at these temperatures.


Assuntos
Gadolínio/química , Glucose/química , Isótopos de Carbono , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos , Deutério , Ácido Pirúvico/química
6.
J Agric Food Chem ; 68(6): 1678-1683, 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-31957422

RESUMO

During submerged cultivation, the edible basidiomycete Fomitopsis betulina (previously Piptoporus betulinus) developed a fruity odor, strongly reminding of pineapple. Olfactometric analysis showed that this impression was mainly caused by the two (5E/Z,7E,9)-decatrien-2-ones. At the time of maximum concentration on the 5th day, the (5E/5Z)-ratio was 94:6. Three hypotheses were experimentally examined to shed light onto the genesis of the uncommon volatiles: first, an indirect effect of agro-industrial side-streams, such as cabbage cuttings, supporting good growth; second, an unsaturated odd-numbered fatty acid precursor; and third, a polyketide-like pathway. In the presence of 1-13C- or 2-13C-acetate up to five acetates were incorporated into the molecular ions of the C10-body. Addition of 1-13C-pyruvate or 1-13C-lactate did not confirm an odd-numbered starter of the polyketide chain. None of the methylketones was found in pineapple or any other food before.


Assuntos
Coriolaceae/química , Odorantes/análise , Compostos Orgânicos Voláteis/química , Acetatos/análise , Isótopos de Carbono/análise , Coriolaceae/crescimento & desenvolvimento , Coriolaceae/metabolismo , Cetonas/química , Compostos Orgânicos Voláteis/metabolismo
7.
Ying Yong Sheng Tai Xue Bao ; 31(1): 301-308, 2020 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-31957408

RESUMO

We measured the ratio of δ13C and δ15N values to estimate the trophic level of main organisms based on a fisheries resource survey in coastal water of Lyusi fishing ground carried out in September 2018. The results showed that δ13C values of the main organisms ranged from -24.27‰ to -13.24‰, with an average of (-17.15±1.85)‰. The δ15N values ranged from 4.30‰ to 14.61‰, with an average of (11.21±1.90)‰. Results from cluster analysis demonstrated that the main organisms in the coastal water of Lyusi fishery ground could be divided into four trophic groups. The first group was consisted mainly by middle and small fishes, shrimps and other invertebrates. The second group included the small-sized fishes like Konosirus punctatus, Mugil cephalus, etc. and shrimps like Exopalaemon annandalei, Exopalamon carincauda, etc. The phytoplankton belonged to the third group. The fourth group was zooplankton. In the trophic spectrum, the trophic levels of fish, shrimps and crabs, shellfish were 3.2-4.7, 3.2-4.2 and 2.0-4.1, respectively. Most species belonged to the category of middle and high-level consumers. In this survey, the average trophic level of the same species in the coastal waters of Lyusi fishing ground was 0.6, which was higher than that in the East China Sea and Yellow Sea. There was niche overlap of most fish, shrimps and crabs. Those results indicated the growth environment and nutrient structure of most living organisms in this area were generally similar.


Assuntos
Cadeia Alimentar , Zooplâncton , Animais , Isótopos de Carbono , China , Peixes , Isótopos de Nitrogênio
8.
J Agric Food Chem ; 68(5): 1213-1225, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31903748

RESUMO

Organically farmed rice is believed to be healthier, safer, and eco-friendlier than its conventionally farmed counterparts and sells for a premium price in global markets. Deliberate mislabeling of organic rice has become a critical consumer concern in China and elsewhere, and there is an increased risk of buying fraudulent organic rice in the market place. In this study, stable isotopic and multielemental analysis combined with chemometrics was used to differentiate organically farmed rice from green and conventional rice in a 4-year experimental field trial from 2014 to 2017. A total of 108 rice samples and their associated soils were collected during the study from three farming (fertilization) systems to investigate whether there are long-term changes in the rice farming classification accuracy from climate effects. Stable carbon and nitrogen isotopic ratios (i.e., δ13C and δ15N) and 27 elemental contents (e.g., Na, K, Ca, Fe, and Zn) of rice and soil samples were determined and then evaluated using statistical analysis [i.e., one-way analysis of variance, multivariable correlation analysis, and modeling of partial least-squares discriminant analysis]. Although δ15N values can be an effective indicator for organic rice authentication during one crop rotation, both δ13C and δ15N values of rice were easily affected by rice cultivar and interannual soil fertilization and localized agroclimatic variations. These two isotopes were not able to separate organic rice from green and conventional rice accurately. Elemental contents of green and conventional rice (especially K and Ca) were found at higher levels due to the abundant application of synthetic fertilizers (e.g., KNO3, KH2PO4, and CaHPO4), unlike organically farmed rice, which primarily used animal manure and composts. Partial least-squares discriminant analysis modeling combined isotopic and elemental signatures to correctly differentiate organic rice from green and conventional counterparts, with an accuracy up to 100% over the 4-year study. Therefore, this multi-isotope and -element strategy proposes a more rigorous, alternative tool to combat fraudulent mislabeling of organic rice, increasing the trust of organically labeled rice products and supporting the integrity of the organic sector worldwide.


Assuntos
Isótopos de Carbono/análise , Contaminação de Alimentos/análise , Alimentos Orgânicos/análise , Isótopos de Nitrogênio/análise , Oryza/química , Oligoelementos/análise , China , Análise Discriminante , Fertilizantes/análise , Oryza/classificação , Solo/química
9.
Chemosphere ; 242: 125130, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31669996

RESUMO

Identifying co-metabolic TCE oxidation in polluted groundwater is challenging due to lack of indicative by-products. This challenge may theoretically be resolved if the oxidation process can be characterized by a distinct dual isotope enrichment. In this work, we aimed to explore the carbon and chlorine isotope effects associated with TCE oxidation by a variety of oxygenases. These included pure strains and enrichment cultures of methane, toluene and ammonia oxidizers, as well as experiments with crude extracts. Isotope effects determined for TCE oxidation by toluene and ammonia oxidizers were mostly in line with expected values for epoxidation mechanism (ϵ13C -11.0 ±â€¯0.7 to -24.8 ±â€¯0.2‰ and ϵ37Cl +0.9 ± 0.5 to +1.0 ± 0.4‰), whereas, the methanotrophs resulted in distinctively different isotope effects (ϵ13C -2.4 ±â€¯0.4 to -3.4 ±â€¯0.8‰ and ϵ37Cl -1.8 ±â€¯0.2 to -2.9 ±â€¯0.9‰). It is suggested that in TCE oxidation by methanotrophs, substrate binding rather than bond cleavage is rate limiting, leading to this unexpected isotope effect. On the environmental level, our results imply that the oxidative process can be differentiated if catalyzed by toluene and ammonia oxidizers or by methanotrophs. Additionally, the oxidative process can be distinguished from the reductive one. However, using dual isotope analysis in the field may result in an under-estimation of the overall co-metabolic process if methanotrophs are to be excluded due to low isotope effects.


Assuntos
Biodegradação Ambiental , Cloro/metabolismo , Tricloroetileno/metabolismo , Poluentes Químicos da Água/metabolismo , Carbono , Isótopos de Carbono/análise , Respiração Celular , Fracionamento Químico , Cloro/química , Poluição Ambiental/análise , Água Subterrânea/química , Metano , Tricloroetileno/química , Poluentes Químicos da Água/química
10.
J Sci Food Agric ; 100(4): 1625-1634, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31802505

RESUMO

BACKGROUND: Walnuts (Juglans regia L.) are considered of high value for human nutrition and are cultivated worldwide. With globalization, however, the demand for regional products has increased. Isotopic fingerprints (δ2 H-, δ15 N- and δ13 C-values (‰)) created by means of stable isotope ratio mass spectrometry provide the possibility of tracing the geographical provenance of plant foods. RESULTS: Authentic walnut samples from different geographical regions in Germany could be separated from each other by means of their bulk δ2 H-values (‰) with samples from northern regions being more enriched in 2 H than samples collected from southern Germany. Next to precipitation data, the topography of the surrounding landscape of the sampling sites was taken into account for data interpretation by the creation of approximate elevation profiles. Moreover, German walnuts could be separated from French walnuts which showed significantly higher δ2 H-values (‰). Variations in annual total precipitation was reflected by the shift in δ2 H-ranges (‰) depending on the harvesting year. Additionally, organic walnuts could be well separated from conventionally produced walnuts due to their distinct δ15 N-values (‰) which could be ascribed to a cultivation practice common for organic farming. CONCLUSIONS: The data presented here outlined the potential of determining isotopic fingerprints of walnuts from different sites within one country for tracing their regional origin and revealing their cultivation conditions. Including topographic characteristics between the sampling locations as well as precipitation data helped to even differentiate walnuts from two adjoining countries. © 2019 The Authors. Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.


Assuntos
Isótopos de Carbono/análise , Deutério/análise , Juglans/química , Isótopos de Nitrogênio/análise , Análise Discriminante , Alemanha , Espectrometria de Massas , Nozes/química
11.
Sci Total Environ ; 704: 135461, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-31810680

RESUMO

Stable carbon isotope ratios (δ13C) are widely used as climate proxies for assessing and predicting climatic information at an annual resolution. However, the detailed information in the isotopes that results from intra-annual climate scenarios and is associated with mineral accumulation remains unclear. Combined with investigations of elements and ash contents, variations in foliar δ13C in relation to annual, winter and summer climate scenarios were investigated in a dendroclimatologically important tree species Sabina przewalskii Kom. Foliar δ13C exhibited a significant negative correlation with mean annual temperature, mean annual precipitation and mean annual relative humidity as well as significant positive correlations with elevation. Climatic factors in winter and summer have opposite effects on the variation of δ13C. The beneficial mineral element Si had a significant positive correlation with foliar δ13C, whereas the essential mineral elements K, Ca, and Mg did not. Specifically, Si and δ13C have similar correlations with climate factors and elevation. These results suggest that measurement of Si content has a similar potential to δ13C for use as an alternative climate indicator when detailed climatic information may otherwise be limited and provide a basis for understanding the integration of δ13C in plant responses to climate.


Assuntos
Clima , Monitoramento Ambiental , Silício/análise , Isótopos de Carbono/análise , Folhas de Planta/química , Tibet , Árvores
12.
Chemistry ; 26(1): 102-113, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31454110

RESUMO

Ribonucleic acid oligonucleotides (RNAs) play pivotal roles in cellular function (riboswitches), chemical biology applications (SELEX-derived aptamers), cell biology and biomedical applications (transcriptomics). Furthermore, a growing number of RNA forms (long non-coding RNAs, circular RNAs) but also RNA modifications are identified, showing the ever increasing functional diversity of RNAs. To describe and understand this functional diversity, structural studies of RNA are increasingly important. However, they are often more challenging than protein structural studies as RNAs are substantially more dynamic and their function is often linked to their structural transitions between alternative conformations. NMR is a prime technique to characterize these structural dynamics with atomic resolution. To extend the NMR size limitation and to characterize large RNAs and their complexes above 200 nucleotides, new NMR techniques have been developed. This Minireview reports on the development of NMR methods that utilize detection on low-γ nuclei (heteronuclei like 13 C or 15 N with lower gyromagnetic ratio than 1 H) to obtain unique structural and dynamic information for large RNA molecules in solution. Experiments involve through-bond correlations of nucleobases and the phosphodiester backbone of RNA for chemical shift assignment and make information on hydrogen bonding uniquely accessible. Previously unobservable NMR resonances of amino groups in RNA nucleobases are now detected in experiments involving conformational exchange-resistant double-quantum 1 H coherences, detected by 13 C NMR spectroscopy. Furthermore, 13 C and 15 N chemical shifts provide valuable information on conformations. All the covered aspects point to the advantages of low-γ nuclei detection experiments in RNA.


Assuntos
Ressonância Magnética Nuclear Biomolecular , RNA/química , Isótopos de Carbono/química , Marcação por Isótopo , Isótopos de Nitrogênio/química , Prótons
13.
J Sci Food Agric ; 100(3): 995-1003, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31646635

RESUMO

BACKGROUND: New techniques are required to guarantee the authenticity of food, especially for PDO (Protected Designation of Origin) trademarks. The genuineness of a product is directly related to the raw material and to the production process used. In this article, the traceability of the Mozzarella di Bufala Campana PDO was investigated, using carbon, nitrogen and oxygen stable isotopes ratios, measured on buffalo feeding, milk and mozzarella, from Caserta and Salerno farms. Furthermore, 37 mozzarella brands were analyzed (carbon, nitrogen and oxygen isotopes) from the different production areas, to characterize their origin. RESULTS: The results of this work showed no changes in carbon and nitrogen isotopic ratios of milk and mozzarella, indicating no fractionation in the production process. The δ13 C of milk was influenced by feeding signal; while, milk δ15 N was regulated by fractionation occurring during ruminant metabolism. Mozzarella oxygen isotopic signal depleted with respect to the milk one. Regarding brand samples, it was found that the geographical differentiation is based more on carbon isotopes than on the nitrogen and oxygen ones. CONCLUSION: This work gives an important contribution to the knowledge regarding the traceability of such a particular cheese as mozzarella. © 2019 Society of Chemical Industry.


Assuntos
Isótopos de Carbono/análise , Queijo/análise , Contaminação de Alimentos/análise , Isótopos de Nitrogênio/análise , Isótopos de Oxigênio/análise , Ração Animal/análise , Animais , Búfalos/metabolismo , Leite/química , Leite/metabolismo
14.
Environ Pollut ; 256: 113401, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753639

RESUMO

This study reveals the impact of biomass burning (BB) on secondary organic aerosols (SOA) formation in the North China Plain (NCP). Filter samples were analyzed for secondary inorganic aerosols (SIA), oxalic acid (C2) and related aqueous-phase SOA compounds (aqSOA), stable carbon isotope composition of C2 (δ13C(C2)) and aerosol liquid water content (ALWC). Based on the PM2.5 loadings, BB tracer concentrations, wildfire spots and air-mass back trajectories, we distinguished two episodes from the whole campaign, Episode I and Episode II, which were characteristic of regional and local BB, respectively. The abundances of PM2.5 and organic matter in the two events were comparable, but concentrations and fractions of SIA, aqSOA during Episode I were much higher than those during Episode II, along with heavier δ13C(C2), suggesting an enhanced aqSOA formation in the earlier period. We found that the enhancement of aqSOA formation during Episode I was caused by an increased ALWC, which was mainly driven by SIA during the regional BB event. Our work showed that intensive burning of crop residue in East Asia can sharply enhance aqSOA production on a large scale, which may have a significant impact on the regional climate and human health.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Monitoramento Ambiental , Biomassa , Carbono/análise , Isótopos de Carbono/análise , China , Clima , Extremo Oriente , Compostos Orgânicos/análise , Material Particulado/análise , Estações do Ano , Água , Incêndios Florestais
16.
J Chem Ecol ; 46(1): 10-20, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31845137

RESUMO

Female moths release sex pheromone to attract mates. In most species, sex pheromone is produced in, and released from, a specific gland. In a previous study, we used empirical data and compartmental modeling to account for the major pheromone gland processes of female Chloridea virescens: synthesis, storage, catabolism and release; we found that females released little (20-30%) of their pheromone, with most catabolized. The recent publication of a new pheromone collection method led us to reinvestigate pheromone release and catabolism in C. virescens on the basis that our original study might have underestimated release rate (thereby overestimating catabolism) due to methodology and females not calling (releasing) continuously. Further we wished to compare pheromone storage/catabolism between calling and non-calling females. First, we observed calling intermittency of females. Then, using decapitated females, we used the new collection method, along with compartmental modeling, gland sampling and stable isotope labeling, to determine differences in pheromone release, catabolism and storage between (forced) simulated calling and non-calling females. We found, (i) intact 1 d females call intermittently; (ii) pheromone is released at a higher rate than previously determined, with simulations estimating that continuously calling females release ca. 70% of their pheromone (only 30% catabolized); (iii) extension (calling)/retraction of the ovipositor is a highly effective "on/off' mechanism for release; (iv) both calling and non-calling females store most pheromone on or near the gland surface, but calling females catabolize less pheromone; (v) females are capable of producing and releasing pheromone very rapidly. Thus, not only is the moth pheromone gland efficient, in terms of the proportion of pheromone released Vs. catabolized, but it is highly effective at shutting on/off a high flux of pheromone for release.


Assuntos
Mariposas/fisiologia , Atrativos Sexuais/metabolismo , Comportamento Sexual Animal , Aldeídos/análise , Aldeídos/farmacologia , Animais , Isótopos de Carbono/química , Feminino , Cromatografia Gasosa-Espectrometria de Massas , Glucose/química , Glucose/metabolismo , Marcação por Isótopo , Masculino , Glândulas Odoríferas/metabolismo , Atrativos Sexuais/análise , Atrativos Sexuais/farmacologia , Comportamento Sexual Animal/efeitos dos fármacos
17.
Geobiology ; 18(1): 14-30, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31496070

RESUMO

The formation of carbonate concretions is a cementation process which passively infills the pore spaces within sediments. They record the original environments of deposition and diagenetic conditions of the host rocks. Little is known about the precise mechanisms responsible for the precipitation of carbonate concretions. The most common host rocks are mudstones/shales, sandstones, and limestones. This study presents an example of large carbonate concretions from an unusual host rock, the black bedded cherts of the Gufeng Formation (Guadalupian) at Enshi on the northern Yangtze Platform, South China. Petrographic observations (X-ray diffraction, optical microscopy, scanning electron microscopy) and multiple geochemical analyses (pyrite- and carbonate-associated-sulfate (CAS)-sulfur isotopes, carbon isotopes) indicate that (a) the studied carbonate concretion are mainly composed of micritic calcite with subordinate dolomite; (b) the concretions may have been mainly formed in the bacterial sulfate reduction (BSR) zone during very early diagenesis near the sediment-water surface; (c) the paleo-bottom water overlying the sediments during formation of the concretions was mainly euxinic; and (d) the growth of the studied concretions proceeded via a pervasive model, where later cementation phase initiated in the lower part of the concretions and progressed upward.


Assuntos
Carbonatos/análise , Isótopos de Carbono , China , Sedimentos Geológicos , Isótopos de Enxofre
18.
Environ Sci Technol ; 54(3): 1593-1602, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31880148

RESUMO

Kinetic isotope effects have been used successfully to prove and characterize organic contaminant transformation on various scales including field and laboratory studies. For tetrachloroethene (PCE) biotransformation, however, causes for the substantial variability of reported isotope enrichment factors (ε) are still not deciphered (εC = -0.4 to -19.0‰). Factors such as different reaction mechanisms and masking of isotope fractionation by either limited intracellular mass transfer or rate-limitations within the enzymatic multistep reaction are under discussion. This study evaluated the contribution of these factors to the magnitude of carbon and chlorine isotope fractionation of Desulfitobacterium strains harboring three different PCE-transforming enzymes (PCE-RdhA). Despite variable single element isotope fractionation (εC = -5.0 to -19.7‰; εCl = -1.9 to -6.3‰), similar slopes of dual element isotope plots (ΛC/Cl values of 2.4 ± 0.1 to 3.6 ± 0.1) suggest a common reaction mechanism for different PCE-RdhAs. Cell envelope properties of the Desulfitobacterium strains allowed to exclude masking effects due to PCE mass transfer limitation. Our results thus revealed that different rate-limiting steps (e.g., substrate channel diffusion) in the enzymatic multistep reactions of individual PCE-RdhAs rather than different reaction mechanisms determine the extent of PCE isotope fractionation in the Desulfitobacterium genus.


Assuntos
Desulfitobacterium , Tetracloroetileno , Tricloroetileno , Biodegradação Ambiental , Biotransformação , Isótopos de Carbono , Fracionamento Químico
19.
Environ Sci Technol ; 54(3): 1634-1645, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31880153

RESUMO

Chloromethane (CH3Cl) is an important source of chlorine in the stratosphere, but detailed knowledge of the magnitude of its sources and sinks is missing. Here, we measured the stable chlorine isotope fractionation (εCl) associated with the major abiotic and biotic CH3Cl sinks in the environment, namely, CH3Cl degradation by hydroxyl (·OH) and chlorine (·Cl) radicals in the troposphere and by reference bacteria Methylorubrum extorquens CM4 and Leisingera methylohalidivorans MB2 from terrestrial and marine environments, respectively. No chlorine isotope fractionation was detected for reaction of CH3Cl with ·OH and ·Cl radicals, whereas a large chlorine isotope fractionation (εCl) of -10.9 ± 0.7‰ (n = 3) and -9.4 ± 0.9 (n = 3) was found for CH3Cl degradation by M. extorquens CM4 and L. methylohalidivorans MB2, respectively. The large difference in chlorine isotope fractionation observed between tropospheric and bacterial degradation of CH3Cl provides an effective isotopic tool to characterize and distinguish between major abiotic and biotic processes contributing to the CH3Cl sink in the environment. Our findings demonstrate the potential of emerging triple-element isotopic approaches including chlorine to carbon and hydrogen analysis for the assessment of global cycling of organochlorines.


Assuntos
Cloreto de Metila , Carbono , Isótopos de Carbono , Fracionamento Químico , Cloro
20.
J Pharm Biomed Anal ; 177: 112889, 2020 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-31568966

RESUMO

This work presents the development of a methodology for the accurate and precise quantification of the renal biomarker Cystatin C in human urine by Isotope Dilution Mass Spectrometry (IDMS). The procedure is based on the addition of a known quantity of the proteotypic peptide ALDFAVG*EYNK labelled with 13C2-glycine to the urine sample followed by protein hydrolysis using trypsin. Then, preconcentration and purification of the isotope diluted peptide was carried out by a selective monoclonal antibody bound to magnetic beads and final measurement was done after injection of the sample in a HPLC-MS/MS triple quadrupole instrument. The isotopic distribution of the isotope diluted proteotypic peptide was measured by low resolution selected reaction monitoring. Using this aquisition mode, the bandpass of the first quadrupole was widened (FWHM =13 u) so the whole isotopic clusters for both the natural abundance and the labelled peptides entered the collision cell. The proposed acquisition mode provided similar accuracy and precision than the regular SRM mode (FWHM =0.7 u) but a higher sensitivity was observed. The purification of the sample by antibody based enrichment of the target peptide was shown to remove interfering compounds more efficiently in comparison with a sample purification based on semipreparative liquid chromatography. Using 5 ng of the labelled peptide it was possible to quantify Cystatin C in human urine in patients with normal and impaired renal function. Recoveries from 100 to 104% were obtained in samples containing from 90 to 700 µg L-1 of Cystatin C with relative standard deviations from 0.5 to 6%. The stability of Cystatin C in urine samples was evaluated under different storage conditions showing that only when the urine samples were stored at room temperature during more than 10 days, a significant degradation of Cystatin C was observed.


Assuntos
Cistatina C/urina , Nefropatias/diagnóstico , Manejo de Espécimes/efeitos adversos , Espectrometria de Massas em Tandem/métodos , Biomarcadores/química , Biomarcadores/urina , Isótopos de Carbono/química , Cromatografia Líquida de Alta Pressão , Cistatina C/química , Taxa de Filtração Glomerular/fisiologia , Humanos , Técnicas de Diluição do Indicador , Rim/fisiopatologia , Nefropatias/fisiopatologia , Nefropatias/urina , Estabilidade Proteica , Manejo de Espécimes/métodos , Temperatura Ambiente , Fatores de Tempo
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