37 resultados para Oxymethylene ethers

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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Ten single benzyl phenyl ethers were synthesized and evaluated as human immunodeficiency virus-1 (HIV-1) inhibitors in vitro for the first time. Among these compounds, especially 4-nitrobenzyl phenyl ether (3h) exhibited the highest anti-HIV-1 activity wi

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To investigate the environmental levels and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs), tree bark samples (n = 22) were collected from Luqiao, an E-waste recycling area, in east China in July 11-13, 2006. The average concentrations of PCDD/Fs, PBDEs, and PCBs determined by isotope dilution-high resolution gas chromatography (HRGC) coupled with high resolution mass spectrometer (HRMS) were 0.1 +/- 0.0, 1.4 +/- 0.2, and 6.5 +/- 0.8 lg g (1) lipid weight, respectively. PCDD/F-toxic equivalent (TEQ, WHO-1998), PCB-TEQs, and total dioxin-like TEQs were 1.3 +/- 0.1, 0.5 +/- 0.0, and 1.8 +/- 0.2 ng g (1) lipid weight, respectively. The profiles of these pollutants in the tree bark were also discussed. Tetra-CDFs, deca-BDE and tri-CBs were the main homologues and accounted for 47% of total PCDD/Fs, 79.3% of total PBDEs, and 33.2% of total PCBs, respectively; As for TEQs, 2,3,4,7,8-PeCDF and PCB126 were the main contributors and accounted for 36% of the total PCDD/F-TEQs and 81.2% of the total PCB-TEQs, respectively. High accumulation of PCDD/Fs, PBDEs, and PCBs detected in the tree bark indicated heavy contaminations of these pollutants in Luqiao area. (C) 2008 Elsevier Ltd. All rights reserved.

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To investigate the occupational exposure levels to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs), indoor dust (n = 3) in workshops and hair samples from male workers (n = 64) were collected at two electrical and electronic equipment waste (E-waste) dismantling factories located in the LQ area in east China in July 11-13, 2006. Pre- and postworkshift urines (64 of each) were also collected from the workers to study oxidative damage to DNA using 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a biomarker. The concentrations of PCDD/Fs, PCDD/F-WHO-TEQs, PBDEs, PCBs and PCB-WHO-TEQs were (50.0 +/- 8.1) x 10(3), 724.1 +/- 249.6, (27.5 +/- 5.8) x 10(6), (1.6 +/- 0.4) x 10(9), (26.2 +/- 3.0) x 10(3) pg/g dry weight (dw) in dust, and (2.6 +/- 0.6) x 10(3), 42.4 +/- 9.3, (870.8 +/- 205.4) x 10(3), (1.6 +/- 0.2) x 10(6), 41.5 +/- 5.5 pg/g dw in hair, respectively. The homologue and congener profiles in the samples demonstrated that high concentrations of PCDD/Fs, PBDEs, and PCBs were originated from open burning of E-waste. The 8-OHdG levels were detected at 6.40 +/- 1.64 mu mol/mol creatinine in preworkshift urines. However, the levels significantly increased to 24.55 +/- 5.96 mu mol/mol creatinine in postworkshift urines (p < 0.05). Then, it is concluded that there is a high cancer risk originated from oxidative stress indicated by the elevated 8-OHdG levels in the E-waste dismantling workers exposed to high concentrations of PCDD/Fs, PBDEs, and PCBs.

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Polybrominated diphenyl ethers (PBDEs) have been detected for the first time at a range from 231.58 to 685.61 ng g(-1) lipid weight in the muscles of tilapia ( Oreochromis mossambicus) collected from O'ahu, an island of the geographically isolated Hawaiian archipelago.

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Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis), a protected endangered species, is the sole freshwater subspecies of finless porpoise, living only in the middle and lower reaches of the Yangtze River, China, and its appended lakes. Its population has decreased sharply to 1,400 because of human activities, including environmental contamination. In the present study, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in the blubber, liver, kidney, stomach, small intestine, and brains of five individual Yangtze finless porpoises collected from 1998 to 2004. The results showed PCB concentrations ranged from 0.06 to 1.89 mu g/g lipid weight in the organs and consisted mainly of penta-, hexa-. and decachlorinated biphenyls. The PBDE concentrations were between 5.32 and 72.76 ng/g lipid weight. Tetra-, penta-, and hexabrominated diphenyl ethers were the major homologues. The PCDD/F concentrations ranged from 65 to 1,563 pg/g lipid weight, and their predominant homologues were penta- and hexachlorinated dibenzofurans and hepta- and octachlorinated dibenzo-p-dioxins. The hazard quotients (HQs) based on toxic equivalency were determined to be greater than one in all individuals for PCBs, for PCDD/Fs, and for PCBs and PCDD/Fs In addition, HQs would be higher if PBDEs were included. The results suggest that reduction of environmental contamination may contribute greatly to protecting this highly endangered species.

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A simple, sensitive, and accurate method for determination of polybrominated diphenyl ethers (PBDEs) in soil has been developed based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). Permethylated-beta-cyclodextrin/hydroxyl-termination silicone oil (PM-beta-CD/OH-TSO) fiber was first prepared by sol-gel technology and employed in SPME procedure. By exploiting the superiorities of sot-gel coating technique and the advantages of the high hydrophobic doughnut-shaped cavity of PM-beta-CD, the novel fiber showed desirable operational stability and extraction ability. After optimization on extraction conditions like water addition, extraction temperature, extraction time, salts effect, and solvents addition, the method was validated in soil samples, achieving good linearity (r>0.999), precision (R.S.D. < 10%), accuracy (recovery>78%), and detection limits (S/N =3) raging from 13.0 to 78.3 pg/g. (c) 2007 Published by Elsevier B.V.

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A new class of ionophores with troponoid and thiocrown ether units was prepared. Cation-binding properties of troponoid dithiocrown ethers were characterized using UV and NMR spectroscopies. They have affinity with metal ions; in particular, they showed high affinity with Hg2+. Transport of Hg2+ through a CHCl3 liquid membrane with troponoid dithiocrown ethers was examined in a U-type cell. From an aqueous solution of HgCl2 and CuCl2, Hg2+ is transferred selectively and smoothly, while the Cu2+ remained quantitatively in the original solution. The cavity size of dithiocrown ethers is one of the requirements for effective extraction and transport of Hg2+. However, derivatives with a smaller cavity still extract and transport Hg2+. A polymer-supported troponoid dithiocrown ether was prepared to transport Hg2+ effectively and repeatedly. Comparing the troponoid dithiocrown ether with the benzenoid dithiocrown ether with a similar cavity size, the former was more effective for the transport of Hg2+. It is proposed that the tropone ring assisted the release of Hg2+ from the complex by Coulomb repulsion between the protonated tropone ring and Hg2+.

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The polymeric films have been prepared based on blends of chitosan with two cellulose ethers-hydroxypropylmethylcellulose and methylcellulose by casting from acetic acid solutions. The films were transparent and brittle in a dry state but an immersion of the samples in deionized water for over 24 h leads to their disintegration or partial dissolution. The miscibility of the polymers in the blends has been assessed by infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis. It was shown that although weak hydrogen bonding exists between the polymer functional groups the blends are not fully miscible in a dry state.

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The gas-phase ion-molecule reactions of C-60 with the methoxymethyl ion [CH3O=CH2](+) and the 1-hydroxyethyl ion [CH3CH=OH](+) generated under the self-chemical-ionization (self-CI) conditions of alkyl methyl ethers and primary alcohols were studied in the ion source of a mass spectrometer. The adduct ions [C60C2H5O](+) and protonated molecules [C60H](+) were observed as the major products of C-60 with the plasma of alkyl methyl ethers. On the contrary, the reactions of C-60 With the plasmas of primary alcohols produced few corresponding adduct ions. The AM1 semiempirical molecular orbital calculations were carried out on 14 possible structures. The calculated results showed that the most stable structure among the possible isomers of [C60C2H5O](+) is the [3+2] cycloadduct. According to experimental and theoretical results, the pathway for the formation of the adduct was presented.

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Gas-phase ion-molecule reactions of buckminsterfullerene (C-60) with the ion systems generated from the self-chemical-ionization of alkyl methyl ethers(CH3OCnH2n+1, n =2 , 3, 4) were studied in the ion source of a mass spectrometer. The adduct cation [C60C2H5O](+) and protonated molecular ion [C60H](+) were observed as the major products, The former was produced by the reactions.of C-60 with the methoxymethyl ion [CH3O = CH2](+) , the latter corresponded to the proton transfer reactions from the protonated alkyl methyl ethers to C60 It is suggested that the [3+2] cycloadduct is the most favorable structure among the probable isomers with special chemical properties, Our investigation provides the guidance for the synthesis of this compound in condensed phase.

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Gas-phase ion-molecule reactions of buckminsterfullerene (C-60) with the ion systems generated from the self-chemical ionization of alkyl methyl ethers (CH3OR, R = n-C2H5, n-C3H7, n-C4H9) were studied in the ion source of a mass spectrometer. The adduct cation [C60C2H5O](+) and protonated molecule [C60H](+) were observed as the major products. The former adduct ion was produced by the reactions of C-60 with the methoxymethyl ion [CH3OCH2](+), and the latter resulted from the proton transfer reactions from protonated alkyl methyl ethers to C-60 It is suggested that the [3+2] cycloadduct to a 6-6 bond of C-60 (a C-C bond common to two annulated six-membered rings) is the most favorable structure among the probable isomers of [C60C2H5O](+). (C) 1998 John Wiley & Sons, Ltd.

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The crystallinity of two series of uniform oligo(oxyethylene) mono-n-alkyl ethers has been investigated: alpha-alkyl,omega-hydroxyoligo(oxyethylene)s, H(CH2)n(OCH2CH2)mOH, and alpha-alkyl,omega-methoxyoligo(oxyethylene)s, H(CH2)n(OCH2CH2)mOCH3. The hydroxy-ended oligomers formed bilayer crystals, and the methoxy-ended oligomers formed monolayer crystals. The helical oxyethylene blocks were oriented normal to the layer-crystal end-group plane, whilst the trans-planar alkyl blocks were generally tilted at an angle delta = 60-degrees. The melting temperature and enthalpy of fusion were higher for hydroxy-ended oligomers than for corresponding methoxy-ended oligomers.

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本研究建立了沉积物中氯化石蜡(CPs)的分析方法,对莱州湾和该区域主要河流的表层沉积物中多氯萘(PCNs),多溴联苯醚(PBDEs)和CPs进行了分析,获得了他们在研究区域的含量水平、空间分布和单体分布模式,并初步探讨了它们在环境中的来源和迁移规律,估算了这三类污染物在莱州湾表层沉积物中的储量,初步评估了莱州湾沿岸的工业排放与人类活动对海洋生态环境的影响。 莱州湾海洋和河流沉积物PCNs的含量分别为65-470 pg/g dw,52-5100 pg/g dw,平均值分别为260 pg/g dw,1100 pg/g dw。莱州湾沉积物中PCNs的含量较低,与发达国家的背景值相当,主要河流沉积物与其他地区的近海、海湾、湖泊沉积物的含量相当。该区域的PCNs主要以5-Cl和6-Cl为主,为工业来源,主要受化工行业的影响。石化工厂热过程产生的低氯组分可能也是该区域PCNs的一个重要来源。莱州湾的PCNs主要来自水体颗粒的输入,而大气沉降来源的贡献不明显。 河流沉积物ΣPBDEs(不包括BDE-209)的含量分别为0.01- 53 ng/g dw,BDE-209的含量为0.74- 280 ng/g dw,平均值分别为4.4 ng/g dw,51 ng/g dw。在组成上,BDE-209占绝对优势,比低溴代BDEs高1-2个数量级,这是由于我国市场上十溴联苯醚是最主要的溴代阻燃剂。ΣPBDEs与亚洲一些地区含量相当,比北美和欧洲一些地区要低;BDE-209含量含量高出北美和欧洲一些地区,处于较高的水平。河流沉积物中BDE-47与-99,BDE-183与-153、-154具有很好的相关性,而且这几种单体质量分数相当,说明莱州湾区域存在五溴和八溴两种工业BDE阻燃剂来源。海洋沉积物中ΣPBDEs的含量为nd- 0.66 ng/g dw,平均值为0.32 ng/g dw,处于较低水平,BDE-209的含量为0.66- 12 ng/g dw,平均值为5.1 ng/g dw,与欧美一些地区相当,主要来自水体颗粒的输入。 本研究用电子捕获低分辨质谱(ECNI-LRMS)建立了沉积物中CPs的分析方法。该方法基于ECNI质谱对SCCP的响应与其氯含量在一定范围内呈线性关系的特性,建立SCCP的总响应因子与氯含量的工作曲线,从而建立定量方法。重点改进了传统方法中由于SCCP标准品和样品中氯含量不同所造成的响应因子的差别,不再要求标准品的含氯量与样品一致,从而提高了SCCP的分析效率与方法准确性。实验发现,当SCCP的实际氯含量在51%-63%之间时,二者线性关系良好(r2>0.96)。用不同氯含量的标准参考品测试,误差为8%-43%。仪器检测限和方法检测限分别为25-400 μg/L,20 ng/g。类似地,建立了中链氯化石蜡(MCCP)的分析方法,工作曲线的实际氯含量范围为44-57%,仪器检测限40-600 μg/L,方法检测限为6 ng/g。通过对比样品与标准品的峰形特征,严格控制保留时间来辨别SCCP与MCCP,实验证明由于二者叠加导致的误差:SCCP为8%,MCCP为14%,总体来说,用该方法得到的CPs数据是可靠的。本文所使用的净化方法能实现CPs与大部分有机氯化合物的分离。 用该方法对莱州湾的沉积物的CPs进行定量,除了两个河流样品MCCP的计算含氯量低于工作曲线以外,其他样品的SCCP和MCCP的计算氯含量都在工作曲线的范围之内。河流沉积物中SCCP和MCCP的含量分别为1-1200 ng/g dw,1-3300 ng/g dw,MCCP/SCCP均值为1.2;含量分布变化较大,一些河段受到工业排放的影响,CPs浓度高出均值1-2个数量级,MCCP/SCCP值也显著高出平均值。莱州湾区域大部分河流的CPs含量与欧洲、北美和日本一些地区相当,而一些受到点源污染的河段则处于较高的水平。河流中SCCP的质量分布在不同的站位不一样,在受到点源影响的样品中,C13的质量分数明显增大,占优势地位,可能是由MCCP携带的SCCP组分所致。MCCP的质量分布在河流和海洋中没有区别,都是C14占绝对优势。从氯取代的组分来讲,所有样品都是以6-8氯取代为主。海洋沉积物中SCCP和MCCP的含量分别为3-18 ng/g dw,1-13 ng/g dw, MCCP/SCCP均值为0.68,显著低于河流沉积物;SCCP的质量分布较为一致,都是以C10和C11为主。研究发现莱州湾区域SCCP与MCCP来源相似,但迁移规律有的不同。海洋环境中的MCCP可能主要来自水体颗粒的输入,而溶解态输入也是海洋环境中SCCP的重要来源。 对这三类污染物在莱州湾表层沉积物中的储量估算得到PCNs、ΣPBDEs、BDE-209、SCCP和MCCP在莱州湾表层0-10 cm沉积物中的储量分别为0.20t,0.25t,3.95t,6.52t,4.30t。拥有10%的渤海海域面积的莱州湾ΣPBDEs和BDE-209的储量分别占渤海海区总量的18-23%,18-32%,远远超过渤海的平均值。

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Polybrominated diphenyl ethers (PBDEs) are used extensively as flame-retardants and are ubiquitous in the environment and in wildlife and human tissue. Recent studies have shown that PBDEs induce neurotoxic effects in vivo and apoptosis in vitro. However, the signaling mechanisms responsible for these events are still unclear. In this study, we investigated the action of a commercial mixture of PBDEs (pentabrominated diphenyl ether, DE-71) on a human neuroblastoma cell line, SK-N-SH. A cell viability test showed a dose-dependent increase in lactate dehydrogenase leakage and 3-(4,5-dimethylthia-zol-2-yl)-2,5-diphenyl-tetrazolium bromide reduction. Cell apoptosis was observed through morphological examination, and DNA degradation in the cell cycle and cell apoptosis were demonstrated using flow cytometry and DNA laddering. The formation of reactive oxygen species was not observed, but DE-71 was found to significantly induce caspase-3, -8, and -9 activity, which suggests that apoptosis is not induced by oxidative stress but via a caspase-dependent pathway. We further investigated the intracellular calcium ([Ca2+](i)) levels using flow cytometry and observed an increase in the intracellular Ca2+ concentration with a time-dependent trend. We also found that the N-methyl d-aspartate (NMDA) receptor antagonist MK801 (3 mu M) significantly reduced DE-71-induced cell apoptosis. The results of a Western blotting test demonstrated that DE-71 treatment increases the level of Bax translocation to the mitochondria in a dose-dependent fashion and stimulates the release of cytochrome c (Cyt c) from the mitochondria into the cytoplasm. Overall, our results indicate that DE-71 induces the apoptosis of ([Ca2+](i)) in SK-N-SH cells via Bax insertion, Cyt c release in the mitochondria, and the caspase activation pathway.