937 resultados para 2,3-butanedione
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The behavior of the photosensitized cis-trans isomerization of 2,3-diphenylbutene-2 was studied as a function of sensitizer energy by previously established methods. In addition, certain sensitizers for which parameters other than energy transfer are operative in inducting isomerizations, were studied in more detail. Sensitization of various stilbenes and substituted stilbenes by triphenylene is discussed in terms of excited state complex formation with stilbene. Sensitization by quinones, halogen-containing aromatics and 1,2-diketones is discussed in terms of attack by photolytically produced free radicals, either by addition to and elimination from the double bond, or in the cases of 1,2-diphenylpropene and 2,3-diphenylbutene-2, by hydrogen abstraction from one of the methyl groups and reversible abstraction by the allylic radical to produce cis-trans isomerized substrate and the structurally isomerized products, 2,3-diphenylpropene and 2,3-diphenylbutene-1.
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276 p.
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国科图
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植物通过异戊二烯代谢途径合成多种具有生物活性和功能的三萜及甾醇类化合物,它们在调节植物生长发育、维持膜的完整和功能、抵抗病原微生物侵染中发挥着重要的作用。2,3-氧化鲨烯为三萜和甾醇合成途径的分枝点,参与这一关键步骤的酶被通称为2,3-氧化鲨烯环化酶(OSCs)。本研究系统分了水稻基因组中全部11个OSC基因序列,发现其中四个可能为假基因。亚种间非同义替换率Ka和同义替换率Ks的比值(Ka/Ks)以及进化树的分析表明OsOSC8是单子叶植物特有的功能保守基因,而OsOSC9在水稻两个亚种间发生了功能快速进化,这种快速进化的基因往往参与植物和病原菌相互作用的代谢途径。 根据基因结构、表达谱以及与其它植物已知功能的OSC酶氨基酸序列的比对推测OsOSC3可能具有环阿屯醇合成酶的功能,参与植物甾醇的合成,而OsOSC7、OsOSC10和OsOSC11可能具有β-香树素合成酶的功能,其余OSCs可能参与合成其它三萜化合物。为了进一步分析和验证OSCs酶的功能,将水稻7个OSC基因的开放阅读框(ORF)构建到酵母表达载体并在pichia酵母中表达,发现仅有OsOSC9和OsOSC12能够将酵母内源的2,3-氧化鲨烯分别环化为四环三萜化合物Parkeol和植物中稀有的五环三萜化合物Isoarborinol,目前还未在其它植物中发现参与这两种三萜化合物的基因。另外,水稻所有的OSC基因均不能互补酵母羊毛甾醇缺陷型菌株,表明水稻OSCs不具有合成羊毛甾醇的功能。 RNAi沉默以及启动子融合GUS的表达实验发现OsOSC8可能参与花粉的发育,该基因的下调影响水稻的育性,暗示水稻中存在一个可能与雄性不育有关的三萜代谢途径。水稻其它OSC基因RNAi植株可能在逆境环境和病原菌侵染下才会显现出表型。
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Meeting to develop environmental indicators to measure overall health of BOBLME; identify important coastal water pollution issues: produce conclusions and recommendations to form an action plan.
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The objective of the workshop was the first assessment of marine coastal ecosystems in the BOBLME environment. The workshop: endorsed the report assessing, demonstrating and capturing the economic value of marine & coastal ecosystem services; acknowledged further data was was needed for ecosystem valuation analysis; recommended information from this report be added to the BOBLME Strategic Action Programme; identified economic instruments that might be used in conservation and sustainable management, and proposed future work.
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The objectives of the workshop included: an overview of the biophysical characteristics of the Myeik Archipelago; strengthen understanding of Marine Protected Areas (MPAs) management to mitigate resource use conflicts; share lessons and experiences of MPA management from the Asia-Pacific region; and to identify a road map for developing MPA management in the Myeik Archipelago.
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A new program of K-isomer research has been initiated with the 8π spectrometer sited at the ISAC facility of TRIUMF. We discuss in this paper the identification of a new 2.3 s isomer in 174Tm and its implications. © Società Italiana di Fisica / Springer-Verlag 2005.
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2甲-基-3-甲氧基-4-苯基丁酸(MMPB)法是检测微囊藻毒素(Microcystins,MC)的重要方法之一。本文研究了温度、pH值、反应时间和氧化剂浓度等实验参数的影响,并在优化条件下采用气相色谱法对水中的微囊藻毒素进行检测。实验得到的最佳反应条件为:pH=9,初始反应温度2℃反应1 h,再升温至25℃反应2 h;KMnO4的初始浓度为0.0156 mol/L。本法对水溶液中的微囊藻的检出限为0.0225μg,回收率为93.5%。
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通过测定原代培养鲫鱼(Carassius auratus)肝细胞中雌激素受体所介导的卵黄蛋白原(Vtg)生成以及芳香烃受体所介导的CYP1A1基因转录水平的变化, 建立了一种类雌激素体外实验模型. 实验结果表明, Vtg和Vtg mRNA的表达与己烯雌酚(DES)之间均有很好的剂量-效应关系, Vtg和Vtg mRNA均可作为指示类雌激素毒性的生物标志物. TCDD, B[a]P可显著抑制鱼肝细胞中DES诱导的Vtg和Vtg mRNA的表达, 呈明显的抗雌激素效应, 并同时激活了CYP1A1 基因的表达;