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1.
Oecologia ; 193(1): 27-51, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32393994

RESUMO

The development of the isotopic niche, an n-dimensional hypervolume (with n being the number of isotopes) occupied by a population in delta space, has revolutionized the study of animal interactions in wild populations. While the isotopic niche offers a useful means to understand interactions at many ecological resolutions (e.g., individual, population, community, ecosystem), a variety of intrinsic and extrinsic factors drive isotopic variability and influence the ultimate geometry of observed niche dimensions. Here, we provide an updated synthesis to guide the application of bulk stable isotope ratios to study ecological niches. We summarize progress in the application of bulk stable isotope ratios for evaluating niches to synthesize a formal definition of the isotopic niche. We identify six broad categories to describe drivers of isotopic variance introduced by the animal, its environment, and the researcher, and provide recommendations to account for such variations before, during, and after sample collection and data analyses. Our synthesis illustrates the considerations that should be made before employing the isotopic niche to broader ecological contexts, and offers guidance for the use and interpretation of isotopic niche dynamics in future studies.


Assuntos
Ecossistema , Isótopos , Animais , Isótopos de Carbono , Isótopos de Nitrogênio
2.
Water Res ; 176: 115750, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32272322

RESUMO

In anaerobic membrane bioreactor (AnMBR) treating organic solid waste, acetate is one of the most important precursors to CH4. However, the identity and diversity of anaerobic acetate degraders are largely unknown, possibly due to their slow growth rates and low abundances. Here, we identified acetate-degrading microorganisms in the AnMBR sludges by high-sensitivity stable isotope probing. Degradation of the amended 13C-acetate coincided with production of 13CH4 and 13CO2 during the sludge incubation. High-throughput sequencing of RNA density fractions indicated that the aceticlastic and hydrogenotrophic methanogens, i.e., Methanosaeta sp. (acetate dissimilator) and Methanolinea sp. (acetate assimilator), incorporated 13C-acetate significantly. Remarkably, 22 bacterial species incorporating 13C-acetate were identified, whereas their majority was distantly related to the cultured representatives. Only two of them were the class Deltaproteobacteria-affiliated lineages with syntrophic volatile fatty acid oxidation activities. Phylogenetic tree analysis and population dynamics tracing revealed that novel species of the hydrolyzing and/or fermenting taxa, such as the phyla Bacteroidetes, Chloroflexi and Lentisphaerae, exhibited low relative abundances comparable to that of Methanolinea sp. (0.00011%) during the AnMBR operation, suggesting that these bacteria were involved in anaerobic acetate assimilation. Meanwhile, novel species of the phyla Firmicutes, Synergistetes and Caldiserica, the candidate phyla Aminicenantes and Atribacteria and the candidate division GOUTA4-related clade, as well as the known Deltaproteobacteria members, existed at relatively high abundances (0.00031%-0.31121%) in the reactor, suggesting that these bacterial species participated in anaerobic dissimilation of acetate, e.g., syntrophic acetate oxidation. The results of this study demonstrated the unexpected diversity and ecophysiological features of the anaerobic acetate degraders in the AnMBR treating organic solid waste.


Assuntos
Metano , Resíduos Sólidos , Acetatos , Anaerobiose , Reatores Biológicos , Isótopos , Filogenia
3.
Nature ; 579(7798): 240-244, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32161386

RESUMO

The accretion of volatile-rich material from the outer Solar System represents a crucial prerequisite for Earth to develop oceans and become a habitable planet1-4. However, the timing of this accretion remains controversial5-8. It has been proposed that volatile elements were added to Earth by the late accretion of a late veneer consisting of carbonaceous-chondrite-like material after core formation had ceased6,9,10. This view could not be reconciled with the ruthenium (Ru) isotope composition of carbonaceous chondrites5,11, which is distinct from that of the modern mantle12, or of any known meteorite group5. As a possible solution, Earth's pre-late-veneer mantle could already have contained a fraction of Ru that was not fully extracted by core formation13. The presence of such pre-late-veneer Ru can only be established if its isotope composition is distinct from that of the modern mantle. Here we report the first high-precision, mass-independent Ru isotope compositions for Eoarchaean ultramafic rocks from southwest Greenland, which display a relative 100Ru excess of 22 parts per million compared with the modern mantle value. This 100Ru excess indicates that the source of the Eoarchaean rocks already contained a substantial fraction of Ru before the accretion of the late veneer. By 3.7 billion years ago, the mantle beneath southwest Greenland had not yet fully equilibrated with late accreted material. Otherwise, no Ru isotopic difference relative to the modern mantle would be observed. If constraints from other highly siderophile elements besides Ru are also considered14, the composition of the modern mantle can only be reconciled if the late veneer contained substantial amounts of carbonaceous-chondrite-like materials with their characteristic 100Ru deficits. These data therefore relax previous constraints on the late veneer and are consistent with volatile-rich material from the outer Solar System being delivered to Earth during late accretion.


Assuntos
Planeta Terra , Isótopos/análise , Rutênio/análise , Groenlândia
4.
Phys Chem Chem Phys ; 22(13): 6838-6847, 2020 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-32191250

RESUMO

The kinetic isotope effect (KIE) is arguably the most established experimental observable reflecting nuclear quantum effects in enzymatic reactions. The role of nuclear quantum effects in enzymes is rather intriguing and has long been a source of profound investigations. Herein, we present a computational study of monoamine oxidase A (MAO A) enzyme and its substrate phenylethylamine, focusing on the impact of nuclear quantum effects on the reaction free energy barrier. Two distinct schemes of quantization of nuclear motion were used, one being the established Quantum Classical Path (QCP) approach, and the other our own code for quantum treatment along the selected nuclear coordinate (hydrogen transfer coordinate) which reasonably mimics the reaction coordinate. In excellent agreement with the experimental value of 8.5 ± 0.3, H/D KIE was computed to 8.66, corresponding to the D-H barrier difference of 1.28 kcal mol-1. The magnitude of KIE implies that nuclear quantum effects probably have only a minor role in the reaction, which is in accordance with the features of potentials computed along the reaction coordinate and with the pertinent energy levels and wavefunctions. The computed H/D KIE for the same reaction in aqueous solution and in the gas phase was fairly similar to the one in the enzyme, suggesting that the role of tunneling in the catalytic function of MAO A is insignificant. The agreement between the computed and observed KIE supported by analysis of nuclear quantum effects implicitly validates the assumed hydride transfer reaction mechanism.


Assuntos
Simulação por Computador , Monoaminoxidase/metabolismo , Fenetilaminas/metabolismo , Catálise , Isótopos/química , Cinética , Teoria Quântica
6.
Isotopes Environ Health Stud ; 56(1): 69-82, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32098526

RESUMO

In this study, three chemometric models for vegetables growing system (field versus greenhouse), geographical origin and species attribution using stable isotope (δ13C, δ18O, δ2H) and elemental fingerprints of 101 samples (54 squashes and 47 radishes) commercialized on Romanian market were developed. These models were constructed and validated through linear discriminant analysis. Initial validations of 94.4% and 83% were obtained for squash and radish growing systems, respectively, such that one squash and four radish samples declared to be grown in the field were attributed to the greenhouse group. For this purpose, the most powerful differentiation markers appeared to be Sn and δ13C for radishes, and Sn, Cu for squashes. Regarding the vegetable origin, four samples, initially considered to originate from Romania (95% for initial classification) were attributed to the foreign group in the cross-validation procedure (93.1%). Romanian radishes and squashes were characterized by a higher content of Na and Cu, respectively, compared with foreign samples, while the mean values for Zn, Sr, Zr and Co concentrations were found to be higher for the vegetables from abroad.


Assuntos
Análise de Alimentos/métodos , Isótopos/análise , Minerais/análise , Verduras/química , Análise Discriminante , Geografia , Espectrometria de Massas , Romênia , Verduras/crescimento & desenvolvimento
7.
Chemosphere ; 248: 126044, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32045973

RESUMO

Source identification of environmental pollutants is critical for pollution prevention and controlling. In this work, Zn isotopic compositions and Zn spatial distribution from headwater to estuary of Erren River (ER) catchments (southern Taiwan) were systematically investigated as a potential source tracer for distinguishing natural weathering and anthropogenic activities. Industrial wastewaters/effluents including leather, printed circuit board (PCB), metal surface treatment (MST), semiconductor wafer (SCW), and electroplating (EP) industries were collected and analyzed as the potential sources of Zn isotopic database. Results implied that MST wastewaters/effluents had the lowest δ66Zn values (Zn isotopic composition) in the range of -0.40 to +0.04. Oppositely, high Zn isotopic composition was observed in leather (δ66Zn = +0.41 to +0.71) and EP wastewaters/effluents (δ66Zn = +0.54 to +1.84). Significantly, the plot of δ66Zn versus 1/Zn clearly indicates that riverine Zn isotope in the ER waters (-0.73 to 1.77‰) can be simply explained by at least three end-member mixing which contains EP, MST wastewaters, and natural component. Our data importantly proved that Zn isotopic composition is a powerful tracer for distinguishing different Zn sources of anthropogenic pollution in rivers.


Assuntos
Monitoramento Ambiental/métodos , Poluentes Químicos da Água/análise , Zinco/análise , Estuários , Água Doce , Isótopos/análise , Rios , Taiwan , Tempo (Meteorologia)
8.
Environ Pollut ; 259: 113888, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32023786

RESUMO

The contributions of contaminant sources are difficult to resolve in the sediment record using concentration gradients and flux reconstruction alone. In this study, we demonstrate that source partitioning using lead isotopes provide complementary and unique information to concentration gradients to evaluate point-source releases, transport, and recovery of metal mining pollution in the environment. We analyzed eight sediment cores, collected within 24 km of two gold mines, for Pb stable isotopes, Pb concentration, and sediment chronology. Stable Pb isotope ratios (206Pb/207Pb, 208Pb/204Pb) of mining ore were different from those of background (pre-disturbance) sediment, allowing the use of a quantitative mixing model. As previously reported for some Arctic lakes, Pb isotope ratios indicated negligible aerosol inputs to sediment from regional or long-range pollution sources, possibly related to low annual precipitation. Maximum recorded Pb flux at each site reached up to 63 mg m-2 yr-1 in the period corresponding to early years of mining when pollution mitigation measures were at a minimum (1950s-1960s). The maximum contribution of mining-derived Pb to these fluxes declined with distance from the mines from 92 ± 8% to 8 ± 4% at the farthest site. Mining-derived Pb was still present at the sediment surface within 9 km of Giant Mine more than ten years after mine closure (5-26 km, 95% confidence interval) and model estimates suggest it could be present for another ∼50-100 years. These results highlight the persistence of Pb pollution in freshwater sediment and the usefulness of Pb stable isotopes to quantify spatial and temporal trends of contamination from mining pollution, particularly as concentrations approach background.


Assuntos
Baías , Monitoramento Ambiental , Sedimentos Geológicos , Isótopos , Chumbo , Mineração , Regiões Árticas , Baías/química , Poluentes Ambientais/análise , Sedimentos Geológicos/química , Ouro , Isótopos/análise , Chumbo/análise , Territórios do Noroeste
9.
BMC Bioinformatics ; 21(1): 37, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32000676

RESUMO

BACKGROUND: DNA-stable isotope probing (DNA-SIP) links microorganisms to their in-situ function in diverse environmental samples. Combining DNA-SIP and metagenomics (metagenomic-SIP) allows us to link genomes from complex communities to their specific functions and improves the assembly and binning of these targeted genomes. However, empirical development of metagenomic-SIP methods is hindered by the complexity and cost of these studies. We developed a toolkit, 'MetaSIPSim,' to simulate sequencing read libraries for metagenomic-SIP experiments. MetaSIPSim is intended to generate datasets for method development and testing. To this end, we used MetaSIPSim generated data to demonstrate the advantages of metagenomic-SIP over a conventional shotgun metagenomic sequencing experiment. RESULTS: Through simulation we show that metagenomic-SIP improves the assembly and binning of isotopically labeled genomes relative to a conventional metagenomic approach. Improvements were dependent on experimental parameters and on sequencing depth. Community level G + C content impacted the assembly of labeled genomes and subsequent binning, where high community G + C generally reduced the benefits of metagenomic-SIP. Furthermore, when a high proportion of the community is isotopically labeled, the benefits of metagenomic-SIP decline. Finally, the choice of gradient fractions to sequence greatly influences method performance. CONCLUSIONS: Metagenomic-SIP is a valuable method for recovering isotopically labeled genomes from complex communities. We show that metagenomic-SIP performance depends on optimization of experimental parameters. MetaSIPSim allows for simulation of metagenomic-SIP datasets which facilitates the optimization and development of metagenomic-SIP experiments and analytical approaches for dealing with these data.


Assuntos
DNA/química , DNA/genética , Marcação por Isótopo/métodos , Metagenômica/métodos , Composição de Bases , Bases de Dados Genéticas , Biblioteca Gênica , Isótopos/análise , Metagenoma
10.
Chemosphere ; 247: 125884, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31978655

RESUMO

Lead (Pb)-poisoning is a serious public health concern and dogs have been useful as a sentinel-animal for Pb exposure of humans. In the present study, the blood Pb concentrations (BLC), isotope ratios (208 Pb/206 Pb and 207 Pb/206 Pb), and biochemistry of 120 domestically owned dogs living around a Pb mining area, in Kabwe, Zambia were analyzed to determine factors associated with Pb exposure. The overall mean value of Pb in dog blood in the present study was 271.6 µg/L. The BLC in the dogs from sites near the mine were significantly higher than those in the dogs from a site 4 km from the mine (352.9 ± 205.1 µg/L versus 28.0 ± 13.9 µg/L). BLC significantly decreased with both increasing age of the dogs and distance from the mine. The Pb isotope ratios in the dog that resided near the mine showed values similar to those reported at the galena mine in Kabwe, which is considered to be the source of Pb exposure. In contrast to the high metal exposure that was determined in these dogs, the mean values of most analyzed parameters in the blood biochemical analysis were surprisingly within or close to the standard reference values. Moreover, none of the dogs showed overt signs of Pb-poisoning or other clinical symptoms. The results of analysis of Pb exposure of the dogs obtained in the present study, which are similar to the previously reported results in human in this location, suggest that dogs could be useful as a sentinel animal for Pb exposure of humans in Kabwe.


Assuntos
Cães/fisiologia , Exposição Ambiental/análise , Chumbo/análise , Mineração , Poluentes do Solo/análise , Animais , Exposição Ambiental/estatística & dados numéricos , Monitoramento Ambiental , Humanos , Isótopos , Chumbo/metabolismo , Poluentes do Solo/metabolismo , Sulfetos , Zâmbia
11.
Chemosphere ; 246: 125638, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31891843

RESUMO

The concentrations of Pb & Sr in Tieguanyin tea leaves and soils from 15 tea gardens of Anxi, China, were determined and the sources of Pb & Sr in soil and leaf samples were analysed using isotope tracing technology. The results showed pH in soils had significant correlations to both acid-extractable Pb & Sr in soils and new leaves. The Pb concentration in leaves was significantly lower than that in soils, especially the acid-extractable Pb in soils. The low Bio-concentration Factor (BCF) indicated the bioavailable Pb in soils could not easily be transferred to leaves. The contribution rates of parent material were 61%-100% and 45%-100% for total Pb isotope and acid-extractable Pb isotope in soils, respectively, indicating a low impact of human activity. A sizeable influence of parent material for leaves was also observed, suggesting that Pb may be present in the dust-fall. Although Sr concentrations in leaves were not high, they exceeded that in soils. The high BCF also indicated that tea has a high capacity to accumulate Sr, with the coincidence that Sr87/Sr86 in the acid-extractable isotope in soils were similar to new leaves. A Pb-Sr joint tracer indicated that Sr in old and new leaves may be influenced by parent material and anthropogenic sources, respectively.


Assuntos
Chumbo/análise , Poluentes do Solo/análise , Solo/química , Estrôncio/análise , Chá/química , China , Jardins , Humanos , Isótopos/análise , Folhas de Planta/química
12.
Environ Sci Technol ; 54(4): 2295-2303, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-31909614

RESUMO

U isotope fractionation may serve as an accurate proxy for U(VI) reduction in both modern and ancient environments, if the systematic controls on the magnitude of fractionation (ε) are known. We model the effect of U(VI) reduction kinetics on U isotopic fractionation during U(VI) reduction by a novel Shewanella isolate, Shewanella sp. (NR), in batch incubations. The measured ε values range from 0.96 ± 0.16 to 0.36 ± 0.07‰ and are strongly dependent on the U(VI) reduction rate. The ε decreases with increasing reduction rate constants normalized by cell density and initial U(VI). Reactive transport simulations suggest that the rate dependence of ε is due to a two-step process, where diffusive transport of U(VI) from the bulk solution across a boundary layer is followed by enzymatic reduction. Our results imply that the spatial decoupling of bulk U(VI) solution and enzymatic reduction should be taken into account for interpreting U isotope data from the environment.


Assuntos
Fracionamento Químico , Cromo , Isótopos , Cinética , Oxirredução
13.
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
14.
Environ Sci Technol ; 54(5): 2744-2752, 2020 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-31995356

RESUMO

Uranium contamination in the environment is a serious public health concern. Biotic U(VI) reduction and nonreductive U(VI) uptake by microorganisms (e.g., U(VI) biosorption by cyanobacteria) are effective U remediation techniques. Variations of 238U/235U have been extensively explored to track biotic U(VI) reduction in laboratory experiments and field applications. However, U isotope fractionation during nonreductive U(VI) uptake by microorganisms is poorly constrained. To investigate U isotope fractionation in this process, we cultured freshwater plankton in the presence of U(VI) and measured 238U/235U in the culture media and biomass. We found that nonreductive U(VI) uptake by freshwater plankton fractionated U isotopes in the opposite direction compared to biotic U(VI) reduction. δ238U values in freshwater plankton were consistently ∼0.23 ± 0.06‰ lighter than those in dissolved U in the culture medium at various fractions of U removal (12-30%), consistent with equilibrium isotope fractionation in a closed system. The equilibrium isotope fractionation observed in our experiments possibly results from changes in coordination geometry between dissolved U(VI) in the culture media and adsorbed U(VI) on cell surfaces. Our experimental results highlight the need to consider U isotope fractionation during nonredox U(VI) uptake by microorganisms and organic matter when applying variations of 238U/235U to track biogeochemical processes and evaluate U remediation.


Assuntos
Urânio , Fracionamento Químico , Água Doce , Isótopos , Plâncton
15.
PLoS One ; 15(1): e0227259, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31968000

RESUMO

The paper discusses results of an interdisciplinary research project integrating lead isotope, chemical, and archaeological analysis of 20 early metal objects from central Italy. The aim of the research was to develop robust provenance hypotheses for 4th and 3rd millennia BC metals from an important, yet hitherto neglected, metallurgical district in prehistoric Europe, displaying precocious copper mining and smelting, as well as socially significant uses of metals in 'Rinaldone-style' burials. All major (and most minor) ore bodies from Tuscany and neighbouring regions were characterised chemically and isotopically, and 20 Copper Age axe-heads, daggers and halberds were sampled and analysed. The objects were also reassessed archaeologically, paying special attention to find context, typology, and chronology. This multi-pronged approach has allowed us to challenge received wisdom concerning the local character of early metal production and exchange in the region. The research has shown that most objects were likely manufactured in west-central Italy using copper from Southern Tuscany and, quite possibly, the Apuanian Alps. A few objects, however, display isotopic and chemical signatures compatible with the Western Alpine and, in one case, French ore deposits. This shows that the Copper Age communities of west-central Italy participated in superregional exchange networks tying together the middle/upper Tyrrhenian region, the western Alps, and perhaps the French Midi. These networks were largely independent from other metal displacement circuits in operation at the time, which embraced the north-Alpine region and the south-eastern Alps, respectively.


Assuntos
Arqueologia , Metalurgia/história , Mineração/história , Ligas/história , Sepultamento/história , Carvão Mineral/história , Cobre/história , Geografia , História Antiga , Isótopos/análise , Itália , Chumbo/análise
16.
Sichuan Da Xue Xue Bao Yi Xue Ban ; 51(1): 74-80, 2020 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-31950793

RESUMO

Objective: To develop an assay for determination of 8-oxo-2'-deoxyguanosine and cotinine in human urine by hydrophilic chromatography tandem mass spectrometry (HILIC-MS/MS) with isotope dilution. Methods: The urine supernatant was 1∶5 diluted with 3 mmol/L ammonium formate aqueous solution containing 15N 5-8-OHdG and D 3-cotinine as internal standard. After being filtered through a 0.22 µm water filter, the sample solution was injected into ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for analysis. Separation was performed on ACQUITY UPLC® BEH HILIC column (50 mm×3.0 mm, 1.7 µm) with isocratic elution (A∶B=10∶90) at 40 ℃. The mobile phase was composed with acetonitrile (B) and 3 mmol/L ammonium formate water soulution (A). The flow rate was 0.3 mL/min. Positive ion scan-multiple reaction monitoring (MRM) mode were used for monitoring and internal standard curves were applied for quantification. Results: Good linearity was obtained under the optimal conditions. Detection limits for 8-OHdG and cotinine were 0.064 µg/L and 0.035 µg/L respectively, the quantitation limits were 0.21 µg/L and 0.12 µg/L respectively, and the recoveries of the spiked urine samples were 92.6%-102% and 102%-106% respectively. Statistical analysis of 40 urine sample determination results obtained by using the above assay showed that there were significant differences in tobacco smoke exposure and tobacco-specific nitrosamine intake between active and passive smoker ( P<0.05). The concentration of NNAL and cotinine were higher in urine samples of active smoker. Tobacco smoke exposure was positively correlated with tobacco specific nitrosamine intake in both active and passive smokers (the correlation coefficients were 0.487 and 0.786 respectively, P<0.05). Conclusion: We successfully established a simple and fast assay for simultaneously detecting 8-oxo-2'-deoxyguanosine and cotinine in human urine. It was sensitive and accurate for quntification via the calibration by the isotope internal standards, and can meet the needs of batch analysis.


Assuntos
8-Hidroxi-2'-Desoxiguanosina , Cromatografia Líquida de Alta Pressão , Cotinina , Espectrometria de Massas em Tandem , Urinálise , 8-Hidroxi-2'-Desoxiguanosina/urina , Cotinina/urina , Humanos , Isótopos/química , Urinálise/métodos
17.
Bioresour Technol ; 302: 122815, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32000131

RESUMO

Three widely-used surfactants, rhamnolipid (RL), sophorolipid (SL) and sodium dodecyl benzene sulfonate (SDBS), were chosen to investigate their effects on the nitrification systems treating step-wised triclosan (TCS). Surfactants had little effects on nitrification. Surfactants could promote the desorption of TCS and enhance the TCS biodegradation in nitrification systems. And TCS biodegradation efficiencies obtained with RL, SL and SDBS were 1.25, 1.23 and 1.14 times higher than the control with 9.0 mg/L TCS, respectively. Illumina MiSeq sequencing showed that Amaricoccus could be resistant to TCS. And Amaricoccus, detected with RL, SL and SDBS, were more abundant than the control. DNA-based stable isotope probing assays revealed Amaricoccus was the major TCS degrader. And the addition of surfactants could obviously increase the diversity of active TCS degraders, especially for biosurfactants. It seems that the addition of surfactants showed positive effects for the nitrification systems treating TCS wastewater.


Assuntos
Triclosan , DNA , Isótopos , Nitrificação , Tensoativos
18.
Chemosphere ; 246: 125746, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31918087

RESUMO

Brominated organic compounds (BOCs), abundant in Nature, originate from its own sources or anthropogenic activity. Many of these compounds are harmful and constitute a serious threat, therefore it is important to study and understand their behavior and fate. In situ, BOCs undergo various chemical and biochemical reactions through distinctive mechanistic pathways. However, breaking C-Br specific bond is a crucial step in the transformation of brominated organic compounds. Understanding the mechanisms of debromination can be substantially enhanced by studying Br isotope effects. In this Mini-review we provide overlook of existing experimental techniques for Br isotope analysis, discuss Br kinetic isotope effects measured for selected chemical and biochemical reactions in the light of underlying reaction mechanisms, and review the outcome from computational study of performed to provide more insightful interpretation of observed findings.


Assuntos
Bromo/química , Halogenação , Isótopos/análise , Cinética
19.
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
20.
PLoS One ; 15(1): e0217665, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31923248

RESUMO

Olfactory sense remains elusive regarding the primary reception mechanism. Some studies suggest that olfaction is a spectral sense, the olfactory event is triggered by electron transfer (ET) across the odorants at the active sites of odorant receptors (ORs). Herein we present a Donor-Bridge-Acceptor model, proposing that the ET process can be viewed as an electron hopping from the donor molecule to the odorant molecule (Bridge), then hopping off to the acceptor molecule, making the electronic state of the odorant molecule change along with vibrations (vibronic transition). The odorant specific parameter, Huang-Rhys factor can be derived from ab initio calculations, which make the simulation of ET spectra achievable. In this study, we revealed that the emission spectra (after Gaussian convolution) can be acted as odor characteristic spectra. Using the emission spectrum of ET, we were able to reasonably interpret the similar bitter-almond odors among hydrogen cyanide, benzaldehyde and nitrobenzene. In terms of isotope effects, we succeeded in explaining why subjects can easily distinguish cyclopentadecanone from its fully deuterated analogue cyclopentadecanone-d28 but not distinguishing acetophenone from acetophenone-d8.


Assuntos
Percepção Olfatória/genética , Neurônios Receptores Olfatórios/metabolismo , Receptores Odorantes/genética , Olfato/genética , Benzaldeídos/farmacologia , Respiração Celular/genética , Transporte de Elétrons/genética , Humanos , Cianeto de Hidrogênio/farmacologia , Isótopos/farmacologia , Nitrobenzenos/farmacologia , Odorantes/análise , Percepção Olfatória/fisiologia , Neurônios Receptores Olfatórios/química , Receptores Odorantes/metabolismo , Olfato/fisiologia , Vibração
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