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  • 1
    Language: English
    In: Plant physiology, April 2010, Vol.152(4), pp.2188-99
    Description: Carotenoid turnover was investigated in mature leaves of Arabidopsis (Arabidopsis thaliana) by 14CO2 pulse-chase labeling under control-light (CL; 130 micromol photons m(-2) s(-1)) and high-light (HL; 1,000 micromol photons m(-2) s(-1)) conditions. Following a 30-min 14CO2 administration, photosynthetically fixed 14C was quickly incorporated in beta-carotene (beta-C) and chlorophyll a (Chl a) in all samples during a chase of up to 10 h. In contrast, 14C was not detected in Chl b and xanthophylls, even when steady-state amounts of the xanthophyll-cycle pigments and lutein increased markedly, presumably by de novo synthesis, in CL-grown plants under HL. Different light conditions during the chase did not affect the 14C fractions incorporated in beta-C and Chl a, whereas long-term HL acclimation significantly enhanced 14C labeling of Chl a but not beta-C. Consequently, the maximal 14C signal ratio between beta-C and Chl a was much lower in HL-grown plants (1:10) than in CL-grown plants (1:4). In lut5 mutants, containing alpha-carotene (alpha-C) together with reduced amounts of beta-C, remarkably high 14C labeling was found for alpha-C while the labeling efficiency of Chl a was similar to that of wild-type plants. The maximum 14C ratios between carotenes and Chl a were 1:2 for alpha-C:Chl a and 1:5 for beta-C:Chl a in CL-grown lut5 plants, suggesting high turnover of alpha-C. The data demonstrate continuous synthesis and degradation of carotenes and Chl a in photosynthesizing leaves and indicate distinct acclimatory responses of their turnover to changing irradiance. In addition, the results are discussed in the context of photosystem II repair cycle and D1 protein turnover.
    Keywords: Arabidopsis -- Metabolism ; Carbon Radioisotopes -- Metabolism ; Carotenoids -- Metabolism ; Chlorophyll -- Metabolism ; Plant Leaves -- Metabolism
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 2
    Language: English
    In: Chemosphere, November 2012, Vol.89(11), pp.1376-1383
    Description: ► Oxidative and reductive degradation of xenobiotics is simulated successfully. ► Model substances for NOM are suggested and evaluated. ► Possible reactions of the model substances and the xenobiotics and/or their degradation products are elucidated. Risk assessment of xenobiotics requires a comprehensive understanding of their transformation in the environment. As most of the transformation processes usually involve a redox reaction or a hydrolysis as the first steps of the transformation, we applied an approach that uses an electrochemical cell to investigate model “redox” reactions in aqueous solutions for environmental processes. We investigated the degradation of a variety of xenobiotics from polar to nonpolar and analyzed their degradation products by on-line coupling of electrochemistry with mass spectrometry (EC–MS). Furthermore, we evaluated possible binding reactions with regard to the generation of non-extractable residues with some model substances (catechol, phthalic acid, γ- -Glutamyl- -cysteinyl-glycine (GSH) and -histidine) deduced from a natural organic matter (NOM) structure model and identified possible binding-sites. Whereas typically investigations in soil/water-systems have been applied, we used to our knowledge for the first time a bottom-up approach, starting from the chemicals of interest and different model substances for natural organic matter to evaluate chemical binding mechanisms (or processes) in the EC–MS under redox conditions. Under oxidative conditions, bindings of the xenobiotics with catechol, GSH and histidine were found, but no reactions with the model compound phthalic acid were observed. In general, no chemical binding has yet been found under reductive conditions. In some cases (i.e. benzo[a]anthracene) the oxidation product only underwent a binding reaction, whereas the xenobiotic itself did not undergo any reactions. EC–MS is a promising fast and simple screening method to investigate the environmental behavior of xenobiotics and to evaluate the potential risks of newly synthesized substances.
    Keywords: Xenobiotics ; Chemical Transformation ; Natural Organic Matter (Nom) ; Electrochemical Simulation ; Mass Spectrometry ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 3
    Language: English
    In: Applied and Environmental Microbiology, April 15, 2013, Vol.79(8), pp.2572-6
    Keywords: Lysimetry – Usage ; Mycobacteria – Research ; Mycobacteria – Physiological Aspects ; Sulfadiazine – Research
    ISSN: 0099-2240
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Analytical and Bioanalytical Chemistry, 2010, Vol.398(7), pp.2803-2811
    Description: Redox cofactors like NADH and NADPH are essential for the catalytic activity of several oxidoreductases. Here, we describe a comparative study of the thermal degradation products of both cofactors in the dry and liquid states. The degradation products were first separated, detected, and quantified by high-performance liquid chromatography (HPLC). Subsequently, selected main fractions were investigated by nanoelectrospray ionization–Fourier transform ion cyclotron resonance mass spectrometry (MS). Additionally, HPLC-MS was used to elucidate the structure of all degradation products. From these data, degradation pathways for both the liquid and the solid states were elucidated. Thermal degradation in water is significantly faster compared to degradation in the solid state. Hydrolysis and oxidative ring opening of the reduced nicotinamide adenine dinucleotide (phosphate) were shown to be the main reaction paths. Surprisingly, no significant differences were observed between the degradation of both cofactors in solution and in the solid state. Our results demonstrate that the stability of both cofactors is not limiting at moderate temperatures if they are used in the dry state (e.g., solid/gas catalysis). Significant degradation of dry cofactors was only observed under conditions, which are usually not appropriate for biocatalysis (〉95 °C). Besides, the situation is completely different in solution where degradation is already observed at moderate temperatures.
    Keywords: FTICR-MS ; HPLC-MS ; NADH ; NADPH ; Chip-based nanoelectrospray ; HILIC
    ISSN: 1618-2642
    E-ISSN: 1618-2650
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  • 5
    Language: English
    In: Chemosphere, Jan, 2014, Vol.95, p.470(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.chemosphere.2013.09.100 Byline: Stephan Sittig, Roy Kasteel, Joost Groeneweg, Diana Hofmann, Bjorn Thiele, Stephan Koppchen, Harry Vereecken Abstract: acents We show transformation and sequestration of the antibiotic sulfadiazine in two soils. acents Transformation products were found in liquid phase and extracts from the sorbed phase. acents We used a compartment model including all species and did global optimization. acents Sorption and transformation are concentration dependent. Article History: Received 12 December 2012; Revised 21 September 2013; Accepted 29 September 2013
    Keywords: Soils ; Sulfadiazine
    ISSN: 0045-6535
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: The Science of the Total Environment, Oct 1, 2013, Vol.463-464, p.395(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2013.06.044 Byline: Jesus D. Fernandez-Bayo, Carine Saison, Marc Voltz, Ulrich Disko, Diana Hofmann, Anne E. Berns Abstract: Chlordecone is a persistent organochlorine insecticide that, even decades after its ban, poses a threat to the environment and human health. Nevertheless, its environmental fate in soils has scarcely been investigated, and elementary data on its degradation and behaviour in soil are lacking. The mineralisation and sorption of chlordecone and the formation of possible metabolites were evaluated in a tropical agricultural andosol. Soil microcosms with two different soil horizons (S-A and S-B) were incubated for 215days with.sup.14C-chlordecone. At five different times (1, 33, 88, 150 and 215days) the extractability of.sup.14C-chlordecone was analysed. Mineralisation was monitored using.sup.14CO.sub.2 traps of NaOH. The appearance of metabolites was studied using thin layer and gas chromatography techniques. At the end of the experiment, the water soluble.sup.14C-activity was 2% of the remaining.sup.14C-chlordecone for S-A and 8% for S-B. Only 12% of the remaining activity was non extractable and more than 80% remained extractable with organic solvents. For the first time to our knowledge, a significant mineralisation of chlordecone was measured in a microcosm under aerobic conditions (4.9% for S-A and 3.2% for S-B of the initial.sup.14C-activity). The drastically lower emission of.sup.14CO.sub.2 in sterilised microcosms indicated the biological origin of chlordecone mineralisation in the non-sterilised microcosms. No metabolites could be detected in the soil extracts. The mineralisation rate of chlordecone decreased by one order of magnitude throughout the incubation period. Thus, the chlordecone content in the soil remained large. This study confirms the existence of chlordecone degrading organisms in a tropical andosol. The reasons why their activity is restricted should be elucidated to allow the development of bioremediation approaches. Possible reasons are a heterogeneous distribution a chlordecone between sub-compartments with different microbial activities or a degradation of chlordecone by co-metabolic processes controlled by a limited supply of nutrients. Article History: Received 20 February 2013; Revised 27 May 2013; Accepted 10 June 2013 Article Note: (miscellaneous) Editor: Mark Hanson
    Keywords: Bioremediation ; Metabolites ; Chromatography ; Organic Chlorine Compounds
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 7
    Language: English
    In: Analytical and Bioanalytical Chemistry, 2008, Vol.391(1), pp.161-169
    Description: An all-glass miniaturized light-phase rotary perforator for the enrichment of polar compounds has been modified/miniaturized and applied. Its application is demonstrated here for the analysis of nitrophenols and dinitrophenols from low-concentration/low-volume samples. For the method development of high-performance liquid chromatography–mass spectrometry (MS) four eluents were tested: (1) water–methanol, (2) acetic acid–methanol, (3) trifluoroacetic acid–methanol and (4) water–acetonitrile. The last eluent mentioned was used for the subsequent investigation of samples from field experiments. Detection limits varied between 1 ng and 50 pg. The relative standard deviation in repeated measurements was below 15%, corresponding to a good reproducibility. Recoveries ranged between 31 and 100%, showing a significant dependence on the extraction time and the final volume of the sample after evaporation. Quantification was carried out by using deuterated 4-nitrophenol and 2,4-dinitrophenol as standards and applying previously determined response factors. Structure determination of further substances under atmospheric pressure chemical ionization was performed by a first screening with a source collision-induced dissociation, followed by the definite analysis by MS n . The first results are shown for cloud water, fog water and rainwater samples from different locations.
    Keywords: High-performance liquid chromatography–mass spectrometry ; Liquid–liquid extraction ; Nitroaromatics ; Phenols ; Sample enrichment ; Water
    ISSN: 1618-2642
    E-ISSN: 1618-2650
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  • 8
    Language: English
    In: Applied and environmental microbiology, April 2013, Vol.79(8), pp.2572-7
    Description: Sulfadiazine (SDZ)-degrading bacterial cultures were enriched from the topsoil layer of lysimeters that were formerly treated with manure from pigs medicated with (14)C-labeled SDZ. The loss of about 35% of the applied radioactivity after an incubation period of 3 years was attributed to CO2 release due to mineralization processes in the lysimeters. Microcosm experiments with moist soil and soil slurries originating from these lysimeters confirmed the presumed mineralization potential, and an SDZ-degrading bacterium was isolated. It was identified as Microbacterium lacus, denoted strain SDZm4. During degradation studies with M. lacus strain SDZm4 using pyrimidine-ring labeled SDZ, SDZ disappeared completely but no (14)CO2 was released during 10 days of incubation. The entire applied radioactivity (AR) remained in solution and could be assigned to 2-aminopyrimidine. In contrast, for parallel incubations but with phenyl ring-labeled SDZ, 56% of the AR was released as (14)CO2, 16% was linked to biomass, and 21% remained as dissolved, not yet identified (14)C. Thus, it was shown that M. lacus extensively mineralized and partly assimilated the phenyl moiety of the SDZ molecule while forming equimolar amounts of 2-aminopyrimidine. This partial degradation might be an important step in the complete mineralization of SDZ by soil microorganisms.
    Keywords: Mycobacterium -- Metabolism ; Sulfadiazine -- Metabolism
    ISSN: 00992240
    E-ISSN: 1098-5336
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  • 9
    Language: English
    In: Journal of agricultural and food chemistry, 22 December 2010, Vol.58(24), pp.12869-77
    Description: To assess the potential occurrence of accelerated herbicide degradation in soils, the mineralization and persistence of (14)C-labeled and nonlabeled atrazine was evaluated over 3 months in two soils from Belgium (BS, atrazine-treated 1973-2008; BC, nontreated) and two soils from Germany (CK, atrazine-treated 1986-1989; CM, nontreated). Prior to the experiment, accelerated solvent extraction of bulk field soils revealed atrazine (8.3 and 15.2 μg kg(-1)) in BS and CK soils and a number of metabolites directly after field sampling, even in BC and CM soils without previous atrazine treatment, by means of LC-MS/MS analyses. For atrazine degradation studies, all soils were incubated under different moisture conditions (50% maximum soil water-holding capacity (WHC(max))/slurried conditions). At the end of the incubation, the (14)C-atrazine mineralization was high in BS soil (81 and 83%) and also unexpectedly high in BC soil (40 and 81%), at 50% WHC(max) and slurried conditions, respectively. In CK soil, the (14)C-atrazine mineralization was higher (10 and 6%) than in CM soil (4.7 and 2.7%), but was not stimulated by slurried conditions. The results revealed that atrazine application history dramatically influences its degradation and mineralization. For the incubation period, the amount of extractable atrazine, composed of residues from freshly applied atrazine and residues from former field applications, remained significantly greater (statistical significance = 99.5 and 99.95%) for BS and CK soils, respectively, than the amount of extractable atrazine in the bulk field soils. This suggests that (i) mostly freshly applied atrazine is accessible for a complex microbial community, (ii) the applied atrazine is not completely mineralized and remains extractable even in adapted soils, and (iii) the microbial atrazine-mineralizing capacity strongly depends on atrazine application history and appears to be conserved on long time scales after the last application.
    Keywords: Soil Microbiology ; Atrazine -- Metabolism ; Bacteria -- Metabolism ; Herbicides -- Metabolism ; Soil -- Analysis ; Soil Pollutants -- Metabolism
    ISSN: 00218561
    E-ISSN: 1520-5118
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  • 10
    Language: English
    In: Chemosphere, April 2017, Vol.172, pp.310-315
    Description: The soil-plant transfer of Cs-137 and Sr-90 in different crops was determined with respect to the present-day amendment practice of using digestate from biogas fermenters. The studies were performed using large lysimeters filled with undisturbed luvisol monoliths. In contrast to the conservative tracer, Br , neither of the studied radionuclides showed a significant vertical translocation nor effect of the applied digestate amendment compared to a non-amended control was found. Furthermore, no significant plant uptake was measured for both nuclides in wheat or oat as indicated by the low transfer factors between soil-shoot for Cs-137 (TF 0.001–0.010) and for Sr-90 (0.10–0.51). The transfer into nutritionally relevant plant parts was even lower with transfer factors for soil-grain for Cs-137 (TF 0.000–0.001) and for Sr-90 (0.01–0.06). Hence, the amendment with biogas digestate is unfortunately not an option to further reduce plant uptake of these radionuclides in agricultural crops, but it does not increase plant uptake either.
    Keywords: Radioactive Contaminants ; Undisturbed Soil Monolith ; Agro-Ecosystem ; Oat ; Wheat ; Transfer Factor ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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