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đây là một slide được tổng hợp từ một bài báo nước ngoài của ba tác giả Karthrin schilling, Thomas M.Johnson and Wolfgang Wilke với tựa đề Isotope fractionation of selenium during fungal biomethylation by Alternaria alternata.
Isotope fractionation of Selenium during fungal biomethylation by Alternaria alternata Nguyễn Thị Lâm Number: 16 Student ID: 12000467 Outline I I Introduction There are a lot of researches about isotope of Se in plants, soils, water or sludge sewage By many different method: * GC-MS * Plasma- MS * Natural microbial consortia The aim of research: Quantifying the degree of methylation of Se[VI] and Se[IV] by the Determining the effects of there different Se fungus A.Alternata at ph and sources and pH values on 82Se/ 76Se in methylselenides Determing the initial Se isotope fraction during methylation of Se(IV) before the reaction ended, Some definitions - Methylation: In the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or groups by a methyl group Se methylselenides Methylation by fungal (Dimethylselenide,Dimethyldiselenide) Incubation: the development and growth of bacteria, etc What is the selenium elements? - - Selenium is a chemical element with symbol Se and atomic number 34 Se occurs naturally in four oxidation states (-II,0,IV,VI) Se has stable isotopes: 74Se( contribution to the total elemental mass: 0.94%), 76Se (9.37%), 77Se (7.64%), 78Se(23.77%), 80Se(49.61%) and 82Se (8.73%) Biological functions: essential trace element for animals and humans most important role for selenium is as an anti-oxidant Se is the ingredient in amino acids (selenomethionie and selencysteine) Selenoproteins play an essential role in the normal development and protection of brain cells Reduce the toxicity of the toxic metals Selenium still has a lot of others function such as prevention of cancer, electrical equipment and coloured glass ,etc Harmful Consuming large amounts of selenium can cause toxicity, but this is unlikely to occur from food alone The symptoms of selenium toxicity include hair loss, vomiting, nausea,etc… Sources of pollution include waste materials from certain mining, agricultural, petrochemical, and industrial manufacturing operations In Belews Lake North Carolina, 19 species of fish were eliminated from the lake due to 150-200 μg Se/L wastewater from a Duke Energy coal-fired power plant At the Kesterson National Wildlife Refuge in California, thousands of fish and waterbirds were poisoned by selenium in agricultural irrigation drainage what about A.Alternata Is a widely distributed filamentous fungus species Is one of the most active terrestrial Se-methylation organisms II Materials and method • Materials • • Stock standard solutions Trap methylselenides All samples were filtered through 0.45 um membrance filters • Incubation • • • The fungus was cultivated on agar plates at 30ºC for days • Adjusting the pH of liquid culture to and The medium was contained in 250-mL EF with a rotatory shaker for days to make an aerobic culture Incubations were conducted in 80-mL serum bottles containing 20mL cultured medium spiked with Se(IV) and Se(VI) to a final amount of 100 μg Se Microaerobic condition and abiotic photochemical formation of methylselenides • • Experiment • • Preparing treatments, each treatments contains Se(VI) or Se(VI) with pH and • • We collected trapped methylselenides on days 11-15 The fungal cultures were incubated for 11-15 days with Se(VI) and Se(IV), addition for 3-5 days with Se(IV) at pH On day 3-5 at pH of Se(IV) to determine separation factors ɛ of kinetic isotope fractionation of Se isotope Trapping of methylselenides • • • Gas washing bottles contain alkaline peroxide solutions Methylselenides were driven out by N2 stream Growth media and fungi were digested by HNO3 to determine the Se remaining and accumulated in the fungi Element and isotope analyses Se isotope ratios were determined with MC-ICPMS In conclusion No methylation occurred without presence of the fungus The formation of methylated compounds occurs for all Se species, however it is most rapid for Se(IV) The fungus grew better under the neutral pH conditions The average ε in the Se(VI) treatments were similar at pH (ε = -3 ± 0.26º/oo) and pH (ε = -2.72 ± 0.41º/oo) The results(VI) demonstrate that ◦ The accummulation or assimilation step of Se(VI) leads possibly to a small fractionation while the methylated Se is likely moderately fractionated In Se(IV) experiment ◦ ◦ • Methylselenides are significant enrich in 76Se compared to the supplied Se(IV) • Two parrallel main pathways were observed simultaneous, one leading to Se(0) and the other leading to methylselenides Methylselenides reflect a stronger fractionation for the methylation pathway than the reduction Se(0) For the accumulation of Se in the fungus e is estimated as -4º/oo to -5º/oo from the difference between a rough estimate In finally we conclude that the isotope composition of Se in methylselenides provides information about the sources of methylselenides but it is not so much affected by pH Future plan In the future I want to research the method to improve polluted Se in environment by faster and more efficient Thanks For Your Attention! [...]... Methylselenides reflect a stronger fractionation for the methylation pathway than the reduction Se(0) For the accumulation of Se in the fungus e is estimated as -4º/oo to -5º/oo from the difference between a rough estimate In finally we conclude that the isotope composition of Se in methylselenides provides information about the sources of methylselenides but it is not so much affected by pH Future plan In the... presence of the fungus The formation of methylated compounds occurs for all Se species, however it is most rapid for Se(IV) The fungus grew better under the neutral pH conditions The average ε in the Se(VI) treatments were similar at pH 4 (ε = -3 ± 0.26º/oo) and pH 7 (ε = -2.72 ± 0.41º/oo) The results(VI) demonstrate that ◦ The accummulation or assimilation step of Se(VI) leads possibly to a small fractionation. .. methylselenides provides information about the sources of methylselenides but it is not so much affected by pH Future plan In the future I want to research the method to improve polluted Se in environment by faster and more efficient Thanks For Your Attention! ... for 3-5 days with Se(IV) at pH On day 3-5 at pH of Se(IV) to determine separation factors ɛ of kinetic isotope fractionation of Se isotope Trapping of methylselenides • • • Gas washing bottles contain... toxicity of the toxic metals Selenium still has a lot of others function such as prevention of cancer, electrical equipment and coloured glass ,etc Harmful Consuming large amounts of selenium. .. There are a lot of researches about isotope of Se in plants, soils, water or sludge sewage By many different method: * GC-MS * Plasma- MS * Natural microbial consortia The aim of research: Quantifying