The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Francesco Palmisano - One of the best experts on this subject based on the ideXlab platform.
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Liquid chromatography/electrospray ionisation sequential mass spectrometric identification of the main Chlortoluron by-products during water disinfection using chlorine
Rapid Communications in Mass Spectrometry, 2000Co-Authors: Carlo Giorgio Zambonin, Ilario Losito, Francesco PalmisanoAbstract:The main degradation by-products of the herbicide Chlortoluron formed during water disinfection with HOCl/ClO− have been separated and identified by liquid chromatography/electrospray ionisation sequential mass spectrometry (LC/ESI-MSn). Chlorination and hydroxylation reactions seem to occur exclusively on the aromatic ring of Chlortoluron, leading to by-products which show characteristic fragmentation patterns. Indeed, Chlortoluron-like ESI spectra were always observed for chlorinated by-products, showing only a fragment at m/z 72. In contrast, hydroxylated and chloro/hydroxylated by-products gave a much more complex fragmentation pattern that could be elucidated by MSn (n = 1–4) experiments. A mechanistic scheme rationalising the observed fragmentation pattern is proposed and discussed. Copyright © 2000 John Wiley & Sons, Ltd.
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liquid chromatography electrospray ionisation sequential mass spectrometric identification of the main Chlortoluron by products during water disinfection using chlorine
Rapid Communications in Mass Spectrometry, 2000Co-Authors: Carlo Giorgio Zambonin, Ilario Losito, Francesco PalmisanoAbstract:The main degradation by-products of the herbicide Chlortoluron formed during water disinfection with HOCl/ClO− have been separated and identified by liquid chromatography/electrospray ionisation sequential mass spectrometry (LC/ESI-MSn). Chlorination and hydroxylation reactions seem to occur exclusively on the aromatic ring of Chlortoluron, leading to by-products which show characteristic fragmentation patterns. Indeed, Chlortoluron-like ESI spectra were always observed for chlorinated by-products, showing only a fragment at m/z 72. In contrast, hydroxylated and chloro/hydroxylated by-products gave a much more complex fragmentation pattern that could be elucidated by MSn (n = 1–4) experiments. A mechanistic scheme rationalising the observed fragmentation pattern is proposed and discussed. Copyright © 2000 John Wiley & Sons, Ltd.
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degradation of Chlortoluron in water disinfectionprocesses a kinetic study
Journal of Environmental Monitoring, 2000Co-Authors: Ilario Losito, Carlo Giorgio Zambonin, Francesco PalmisanoAbstract:The kinetics of the reaction between Chlortoluron, a phenylurea herbicide [N′-(2-hydroxy-4-methyl-5-chloro-phenyl)-N,N-dimethylurea], and hypochlorite, the active species in water disinfection processes involving chlorine, were investigated by HPLC-UV and HPLC-electrospray ionisation mass spectrometry (HPLC-ESI-MS). In particular, the concentrations of the main Chlortoluron by-products were monitored as a function of time by HPLC-ESI-MS and a kinetic model was developed to fit the relevant curves. The results showed that Chlortoluron degradation starts with two parallel pathways, namely, chlorination and hydroxylation of the aromatic ring, which are then followed by consecutive chlorination reactions, and after almost 2 weeks by ring opening and partial mineralisation, as confirmed by head-space solid-phase microextraction gas chromatography-MS (SPME-GC-MS) and total organic carbon (TOC) measurements. Kinetic constants for the first reactions of the overall process, under pseudo-first-order conditions (hypochlorite excess), were estimated by a fitting procedure.
Carlo Giorgio Zambonin - One of the best experts on this subject based on the ideXlab platform.
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Liquid chromatography/electrospray ionisation sequential mass spectrometric identification of the main Chlortoluron by-products during water disinfection using chlorine
Rapid Communications in Mass Spectrometry, 2000Co-Authors: Carlo Giorgio Zambonin, Ilario Losito, Francesco PalmisanoAbstract:The main degradation by-products of the herbicide Chlortoluron formed during water disinfection with HOCl/ClO− have been separated and identified by liquid chromatography/electrospray ionisation sequential mass spectrometry (LC/ESI-MSn). Chlorination and hydroxylation reactions seem to occur exclusively on the aromatic ring of Chlortoluron, leading to by-products which show characteristic fragmentation patterns. Indeed, Chlortoluron-like ESI spectra were always observed for chlorinated by-products, showing only a fragment at m/z 72. In contrast, hydroxylated and chloro/hydroxylated by-products gave a much more complex fragmentation pattern that could be elucidated by MSn (n = 1–4) experiments. A mechanistic scheme rationalising the observed fragmentation pattern is proposed and discussed. Copyright © 2000 John Wiley & Sons, Ltd.
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liquid chromatography electrospray ionisation sequential mass spectrometric identification of the main Chlortoluron by products during water disinfection using chlorine
Rapid Communications in Mass Spectrometry, 2000Co-Authors: Carlo Giorgio Zambonin, Ilario Losito, Francesco PalmisanoAbstract:The main degradation by-products of the herbicide Chlortoluron formed during water disinfection with HOCl/ClO− have been separated and identified by liquid chromatography/electrospray ionisation sequential mass spectrometry (LC/ESI-MSn). Chlorination and hydroxylation reactions seem to occur exclusively on the aromatic ring of Chlortoluron, leading to by-products which show characteristic fragmentation patterns. Indeed, Chlortoluron-like ESI spectra were always observed for chlorinated by-products, showing only a fragment at m/z 72. In contrast, hydroxylated and chloro/hydroxylated by-products gave a much more complex fragmentation pattern that could be elucidated by MSn (n = 1–4) experiments. A mechanistic scheme rationalising the observed fragmentation pattern is proposed and discussed. Copyright © 2000 John Wiley & Sons, Ltd.
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degradation of Chlortoluron in water disinfectionprocesses a kinetic study
Journal of Environmental Monitoring, 2000Co-Authors: Ilario Losito, Carlo Giorgio Zambonin, Francesco PalmisanoAbstract:The kinetics of the reaction between Chlortoluron, a phenylurea herbicide [N′-(2-hydroxy-4-methyl-5-chloro-phenyl)-N,N-dimethylurea], and hypochlorite, the active species in water disinfection processes involving chlorine, were investigated by HPLC-UV and HPLC-electrospray ionisation mass spectrometry (HPLC-ESI-MS). In particular, the concentrations of the main Chlortoluron by-products were monitored as a function of time by HPLC-ESI-MS and a kinetic model was developed to fit the relevant curves. The results showed that Chlortoluron degradation starts with two parallel pathways, namely, chlorination and hydroxylation of the aromatic ring, which are then followed by consecutive chlorination reactions, and after almost 2 weeks by ring opening and partial mineralisation, as confirmed by head-space solid-phase microextraction gas chromatography-MS (SPME-GC-MS) and total organic carbon (TOC) measurements. Kinetic constants for the first reactions of the overall process, under pseudo-first-order conditions (hypochlorite excess), were estimated by a fitting procedure.
Ilario Losito - One of the best experts on this subject based on the ideXlab platform.
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Liquid chromatography/electrospray ionisation sequential mass spectrometric identification of the main Chlortoluron by-products during water disinfection using chlorine
Rapid Communications in Mass Spectrometry, 2000Co-Authors: Carlo Giorgio Zambonin, Ilario Losito, Francesco PalmisanoAbstract:The main degradation by-products of the herbicide Chlortoluron formed during water disinfection with HOCl/ClO− have been separated and identified by liquid chromatography/electrospray ionisation sequential mass spectrometry (LC/ESI-MSn). Chlorination and hydroxylation reactions seem to occur exclusively on the aromatic ring of Chlortoluron, leading to by-products which show characteristic fragmentation patterns. Indeed, Chlortoluron-like ESI spectra were always observed for chlorinated by-products, showing only a fragment at m/z 72. In contrast, hydroxylated and chloro/hydroxylated by-products gave a much more complex fragmentation pattern that could be elucidated by MSn (n = 1–4) experiments. A mechanistic scheme rationalising the observed fragmentation pattern is proposed and discussed. Copyright © 2000 John Wiley & Sons, Ltd.
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liquid chromatography electrospray ionisation sequential mass spectrometric identification of the main Chlortoluron by products during water disinfection using chlorine
Rapid Communications in Mass Spectrometry, 2000Co-Authors: Carlo Giorgio Zambonin, Ilario Losito, Francesco PalmisanoAbstract:The main degradation by-products of the herbicide Chlortoluron formed during water disinfection with HOCl/ClO− have been separated and identified by liquid chromatography/electrospray ionisation sequential mass spectrometry (LC/ESI-MSn). Chlorination and hydroxylation reactions seem to occur exclusively on the aromatic ring of Chlortoluron, leading to by-products which show characteristic fragmentation patterns. Indeed, Chlortoluron-like ESI spectra were always observed for chlorinated by-products, showing only a fragment at m/z 72. In contrast, hydroxylated and chloro/hydroxylated by-products gave a much more complex fragmentation pattern that could be elucidated by MSn (n = 1–4) experiments. A mechanistic scheme rationalising the observed fragmentation pattern is proposed and discussed. Copyright © 2000 John Wiley & Sons, Ltd.
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degradation of Chlortoluron in water disinfectionprocesses a kinetic study
Journal of Environmental Monitoring, 2000Co-Authors: Ilario Losito, Carlo Giorgio Zambonin, Francesco PalmisanoAbstract:The kinetics of the reaction between Chlortoluron, a phenylurea herbicide [N′-(2-hydroxy-4-methyl-5-chloro-phenyl)-N,N-dimethylurea], and hypochlorite, the active species in water disinfection processes involving chlorine, were investigated by HPLC-UV and HPLC-electrospray ionisation mass spectrometry (HPLC-ESI-MS). In particular, the concentrations of the main Chlortoluron by-products were monitored as a function of time by HPLC-ESI-MS and a kinetic model was developed to fit the relevant curves. The results showed that Chlortoluron degradation starts with two parallel pathways, namely, chlorination and hydroxylation of the aromatic ring, which are then followed by consecutive chlorination reactions, and after almost 2 weeks by ring opening and partial mineralisation, as confirmed by head-space solid-phase microextraction gas chromatography-MS (SPME-GC-MS) and total organic carbon (TOC) measurements. Kinetic constants for the first reactions of the overall process, under pseudo-first-order conditions (hypochlorite excess), were estimated by a fitting procedure.
Hideo Ohkawa - One of the best experts on this subject based on the ideXlab platform.
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Expression of Human Cytochromes P450 1A1 and P450 1A2 as Fused Enzymes with Yeast NADPH-cytochrome P450 Oxidoreductase in Transgenic Tobacco Plants
Bioscience Biotechnology and Biochemistry, 2020Co-Authors: Noriaki Shiota, Hideyuki Inui, Susumu Kodama, Hideo OhkawaAbstract:Among 11 isoforms of the human cytochrome P450 enzymes metabolizing xenobiotics, CYP 1A1 and CYP 1A2 were major P450 species in the metabolism of the herbicides Chlortoluron and atrazine in a yeast expression system. CYP1A2 was more active in the metabolism of both herbicides than CYP1A1. The fused enzymes of CYP1A1 and CYP1A2 with yeast NADPH-cytochrome P450 oxidoreductase were functionally active in the microsomal fraction of the yeast Saccharomyces cerevisiae and showed increased specific activity towards 7-ethoxyresorufin as compared to CYP1A1 and CYP1A2 alone. Then, both fused enzymes were each expressed in the microsomes of tobacco (Nicotiana tabacum cv. Samsun NN) plants. The transgenic plants expressing the CYP1A2 fusion enzyme had higher resistance to the herbicide Chlortoluron than the plants expressing the CYP1A1 fusion enzyme did. The transgenic plants expressing the CYP1A2 fused enzyme metabolized Chlortoluron to a larger extent to its non-phytotoxic metabolites through N-demethylation and ring-methyl hydroxylation as compared to the plants expressing the CYP1A1 fused enzyme. Thus, the possibility of increasing the herbicide resistance in the transgenic plants by the selection of P450 species and the fusion with P450 reductase is discussed.
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Transgenic rice plants expressing human CYP1A1 exude herbicide metabolites from their roots
Plant Science, 2003Co-Authors: Hiroyuki Kawahigashi, Hideo Ohkawa, Sakiko Hirose, Yasunobu OhkawaAbstract:Abstract We introduced a human cytochrome P450 CYP1A1 gene into rice plants ( Oryza sativa cv. Nipponbare) to confer herbicide tolerance. In germination tests, the R 1 seeds showed tolerance to various herbicides with different modes of action, including quizalofop-ethyl (0.2 μM), norflurazon (0.5 μM), mefenacet (2.5 μM), and Chlortoluron (100 μM). We used 14 C-labeled atrazine, Chlortoluron, and norflurazon to confirm the metabolism of herbicides by the action of the introduced CYP1A1. Although both CYP1A1 plants and nontransgenic control plants metabolized these herbicides into the same set of chemical compounds, the herbicides were metabolized more rapidly in the CYP1A1 plants. We were surprised to find that the levels of the intermediate metabolites were higher in the culture medium of the CYP1A1 plants than in the plants themselves, because it is commonly accepted that herbicides are taken up, metabolized, and stored in plants. The metabolites of herbicides seemed to be exuded into the medium from the roots of the CYP1A1 plants. The introduced P450 enhanced the metabolism of the herbicides in plants. Therefore, the CYP1A1 plants became more tolerant to various herbicides than the control plants.
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Molecular Cloning of Novel Cytochrome P450 Species Induced by Chemical Treatments in Cultured Tobacco Cells
Pesticide Biochemistry and Physiology, 2000Co-Authors: Takashi Yamada, Yumiko Kambara, Hiromasa Imaishi, Hideo OhkawaAbstract:Abstract We describe the isolation of four cDNA clones from 2,4-D-treated cultured tobacco cells encoding novel P450 species inducible by chemical treatments. RNA blot analysis showed that mRNA levels corresponding to CYP71A11, CYP81B2, CYP81C1, and CYP81C2 genes were differentially increased by 2,4-D treatment. Furthermore, mRNA levels of CYP71A11, CYP81C1, and CYP81C2 were also increased by treatments with a herbicide safener, naphthalic anhydride, and a plant signaling molecule, salicylic acid, with different kinetics. CYP81B2 and CYP71A11 expressed in yeast showed monooxygenase activities toward 7-ethoxycoumarin and the herbicide Chlortoluron. These results suggested that CYP71A11, CYP81C1, and CYP81C2 are potential targets for herbicide safeners, and CYP81B2 and CYP71A11 are involved in Chlortoluron metabolism. In addition, the results suggested the possibility that 2,4-D and naphthalic anhydride may influence not only xenobiotic metabolism but also salicylic acid-dependent responses in tobacco cells.
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metabolism of the herbicide Chlortoluron in transgenic tobacco plants expressing the fused enzyme between rat cytochrome p4501a1 and yeast nadph cytochrome p450 oxidoreductase
Pesticide Biochemistry and Physiology, 1996Co-Authors: Noriaki Shiota, Hideyuki Inui, Hideo OhkawaAbstract:Abstract Metabolism of the herbicide Chlortoluron was examined in transgenic tobacco plants expressing the genetically engineered fused enzyme between rat cytochrome P4501A1 and yeast NADPH-cytochrome P450 oxidoreductase. The transgenic plants were resistant to Chlortoluron at concentrations of 10 to 50 μ M in Murashige and Skoog medium; however, 10 μ M was toxic to control plants. There were no significant differences in the uptake and the translocation of [ 14 C] Chlortoluron between transgenic and control plants. The major metabolites produced by transgenic plants were N -demethylated metabolite, 4-carboxyphenyl metabolite, and their conjugates, whereas only the N -demethylated metabolite was produced by control plants. In vitro studies also confirmed that the fused enzyme expressed in the microsomal fraction of the transgenic plants exhibited both ring-methyl hydroxylation and N -demethylation activities toward chlor-toluron. These results suggested that the transgenic tobacco plants expressing the fused enzyme metabolized Chlortoluron to yield larger amounts of nonphytotoxic metabolites, resulting in tolerance to the herbicide.
Olga Kalitowska - One of the best experts on this subject based on the ideXlab platform.
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Influence of application date and adjuvant on Chlortoluron residues and quality of winter wheat grain Wpływ terminu aplikacji oraz dodatku adiuwanta na pozostałości chlorotoluronu i jakość ziarna pszenicy ozimej
Progress in Plant Protection, 2020Co-Authors: M Kucharski, Jerzy Sadowski, Olga KalitowskaAbstract:Summary The aim of the studies was to determine the influence of herbicide application date and adjuvants on weed control efficacy, residues and quality parameters of winter wheat grain. Field experiment was conducted in the years 2010–2012. Chemical weed control in winter wheat was carried out with commercial formulation of Chlortoluron (herbicide Tolurex 500 SC). Herbicide was applied separately at recommended and reduced doses and at reduced dose in mixture with adjuvants as a preemergence application in the autumn and as a postemergence treatment in the late autumn and in the spring. Phytotoxicity and efficacy of herbicide and its mixtures with adjuvants were evaluated in the experiments. Moreover, the residue of Chlortoluron in soil and grain of winter wheat and wheat grain quality were analyzed. No phytotoxic effects of used herbicide (separately and jointly with adjuvant) and application date on winter wheat were stated. Application of herbicide with adjuvant allowed reducing the herbicide dose (without loss of weed control efficacy). The addition of adjuvants caused a significant increase in the weed control and the herbicide residues in soil and grain samples as compared to the treatments with herbicide that was used separately (at reduced dose). Application of herbicide, herbicide with adjuvant and application date did not influence quality parameters of wheat grain. The highest yield of grain and weed control efficacy was obtained after preemergence, autumn application of herbicide and the highest Chlortoluron residue level was determined in soil and grain samples from plots treated in spring.
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influence of application date and adjuvant on Chlortoluron residues and quality of winter wheat grain wplyw terminu aplikacji oraz dodatku adiuwanta na pozostalości chlorotoluronu i jakośc ziarna pszenicy ozimej
Progress in Plant Protection, 2013Co-Authors: M Kucharski, Jerzy Sadowski, Olga KalitowskaAbstract:Summary The aim of the studies was to determine the influence of herbicide application date and adjuvants on weed control efficacy, residues and quality parameters of winter wheat grain. Field experiment was conducted in the years 2010–2012. Chemical weed control in winter wheat was carried out with commercial formulation of Chlortoluron (herbicide Tolurex 500 SC). Herbicide was applied separately at recommended and reduced doses and at reduced dose in mixture with adjuvants as a preemergence application in the autumn and as a postemergence treatment in the late autumn and in the spring. Phytotoxicity and efficacy of herbicide and its mixtures with adjuvants were evaluated in the experiments. Moreover, the residue of Chlortoluron in soil and grain of winter wheat and wheat grain quality were analyzed. No phytotoxic effects of used herbicide (separately and jointly with adjuvant) and application date on winter wheat were stated. Application of herbicide with adjuvant allowed reducing the herbicide dose (without loss of weed control efficacy). The addition of adjuvants caused a significant increase in the weed control and the herbicide residues in soil and grain samples as compared to the treatments with herbicide that was used separately (at reduced dose). Application of herbicide, herbicide with adjuvant and application date did not influence quality parameters of wheat grain. The highest yield of grain and weed control efficacy was obtained after preemergence, autumn application of herbicide and the highest Chlortoluron residue level was determined in soil and grain samples from plots treated in spring.