Study on the mechanism of action between dimethyl phthalate and herring sperm DNA at molecular level

Dimethyl phthalate (DMP), a typical phthalic acid ester, is widespread in the environment and causes extensive concern due to its adverse effects on human health. To understand the genotoxicity of DMP at molecular level, the toxic interaction of DMP with herring sperm (hs) deoxyribonucleic acid (DNA; hs-DNA) was investigated in vitro under simulated physiological conditions using multi-spectroscopic techniques and a molecular modeling method. The results of Ultraviolet-Visible absorption spectroscopy, fluorescence emission spectroscopy, and circular dichroism spectra indicated that DMP interacts with hs-DNA in a groove-binding mode that changes the double helical structure of DNA. The binding constant and the number of binding sites calculated from the fluorescence quenching data were 565.718 L mol^?1 and 0.7872, respectively. A molecular modeling study revealed that DMP tends to bind with DNA in the A-T-rich regions of minor groove and that hydrogen bonding and van der Waals forces play main roles in the interaction. This research can help to elucidate the mechanism of DMP toxicity in vivo.     

In vivo and in vitro metabolism of tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), by the freshwater planarian, Dugesia japonica

Cigarette smoke is a risk factor for human health, and many studies were conducted to investigate its adverse effects on humans and other mammals. However, since large amounts of cigarette products are produced and consumed, it is possible that tobacco chemicals can end up in aquatic environments through several routes, thus influencing aquatic organisms. In this study, the presence of tobacco-specific nitrosamine (TSNA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in aquatic environment was demonstrated. Since toxic effects on and distribution patterns of tobacco chemicals in aquatic organisms were rarely studied, after results of an acute toxicity pretest were obtained, experiment was conducted to investigate the bioaccumulation pattern of NNK and distribution patterns of its metabolites, mainly 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), in NNK-treated freshwater planarians, Dugesia japonica. Results from in vivo and in vitro studies showed that NNK was readily converted to NNAL through the carbonyl reduction in bodies of NNK-treated planarians. Tissue concentrations of both chemicals increased in time- and dose-dependent manners. Furthermore, we examined the end products of NNK/NNAL α-hydroxylation in NNK-treated planarians, but only 1-(3-pyridyl)-1,4-butanediol was detected, suggesting that NNK metabolism in planarians partially differs from that in mammalian systems. This is the first report on NNK metabolism in an aquatic organism and can be used as a foundation for developing freshwater planarians as a new in vivo model for the study of NNK toxicology in the future.     

液化气脱硫醇装置碱渣减排的探索及实践

为减少碱渣排放量,液化气碱洗脱硫醇装置大都设计有碱液催化氧化再生设施。由于传统碱液氧化再生工艺存在副产物二硫化物与再生碱液分离效果差等技术缺陷,其成为液化气脱硫质量的技术瓶颈。从碱液氧化再生原理、二硫化物分离原理等方面寻找突破口,实现了二硫化物大部分的分离回收,系统碱液可长周期循环用于液化气脱硫醇,液态烃碱渣排量减少80%以上。     

气相色谱法测定氨气中的甲硫醇及甲硫醚

建立了测定氨气中甲硫醇及甲硫醚的气相色谱分析方法。样品充入高纯氮气后，通过磷酸吸收液脱除氨气，有机硫化物由氨气转移到高纯氮气中，收集这部分气体，取1．0～2．0mL采用火焰光度检测填充柱气相色谱法进行分析。方法的相对标准偏差小于7％，甲硫醇和甲硫醚的加标回收率分别为92．1％和87．6％，最低检出量分别为0．11ng和0．17ng，最低检出质量浓度分别为0．11μg／L和0．17μg/L。     

固相萃取-气相色谱法检测水中的邻苯二甲酸酯

利用固相萃取技术富集了水中4种邻苯二甲酸酯类（PAEs）化合物：邻苯二甲酸二甲酯（DMP）、邻苯二甲酸二乙酯（DEP）、邻苯二甲酸二丁酯（DBP）、邻苯二甲酸二（2-乙基己基）酯（DEHP）。借助均匀设计法及计算机回归建模优化技术对4种PAEs的固相萃取条件进行了设计与优化，得到的最佳固相萃取条件：洗脱剂配比（正己烷与丙酮的体积比）30：1，洗脱体积2mL，洗脱速率4mL／min，上样速率8mL／min。富集后的试样用带电子捕获器的毛细管气相色谱仪检测，方法的线性范围为1～1000μg／L（DMP，DEP），0．2—100μg／L（DBP，DEHP），线性回归方程的相关系数为0．9970～1．0000，检出限为0．02-0．4μg／L，4种PAEs的回收率为69％～117％，相对标准偏差为2．5％～9．5％。[关键词]     

Biochemical Cooperation Between Klebsiella oxytoca Sc and Methylobacterium mesophilium Sr for Complete Degradation of Dimethyl Isophthalate

Klebsiella oxytoca Sc and Methylobacterium mesophilicum Sr were isolated from enrichment cultures using dimethyl isophthalate (DMI) as the sole carbon and energy source and mangrove sediment as an inoculum. Complete degradation of DMI required both species of bacteria at different biochemical transformation steps. The biochemical degradation pathway was DMI to monomethyl isophthalate (MMI) by K. oxytoca Sc, MMI to isophthalate (IPA) by M. mesophilium Sr, and IPA by both K. oxytoca Sc and M. mesophilium Sr sequentially. The consortium comprising of K. oxytoca Sc and M. mesophilicum Sr was effective in complete degradation of DMI in eight days. Our results suggest that a consortium of microorganisms indigenous to the mangrove environment is responsible for mineralization of environmental pollutant DMI through biochemical cooperation.     

表面活性剂光催化降解动力学研究

为了研究光催化法对不同电荷类型表面活性剂的降解性能,在紫外光照射下,用TiO2光催化剂对阴离子表面活性剂十二烷基磺酸钠(SDS)、阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)和两性表面活性剂十八烷基甜菜碱(BS18)进行降解试验.同时,探讨了TiO2光催化剂加入量、表面活性剂初始质量浓度及初始pH对光降解的影响及其动力学过程.结果表明,3种表面活性剂的降解行为符合准一级动力学规律,3种表面活性剂降解速率快慢顺序为:BS18CTABSDS.SDS和BS18的最佳TiO2催化剂用量为1 g.L-1,而CTAB的最优用量为2g.L-1;CTAB和BS18的光降解速率随着活性剂初始质量浓度的增大而线性减小,SDS的降解速率则随活性剂初始质量浓度的增加而缓慢增大;CTAB和BS18在偏碱性条件下降解最快,而SDS在弱酸条件下具有最大的动力学降解速率.     

利用邻苯二甲酸二甲酯培养好氧颗粒污泥研究

以活性污泥为接种污泥,葡萄糖为共代谢基质,通过控制有机负荷、污泥沉降时间,在序批式反应器(sequencing batchreactor,SBR)内培养得到具有邻苯二甲酸二甲酯(dimethyl phthalate,DMP)降解性能的好氧颗粒污泥.结果表明,好氧颗粒污泥对DMP具有很好的去除效果,驯化75 d后,DMP与COD去除率分别达到92.3%与90.6%.好氧颗粒污泥降解DMP的中间产物为邻苯二甲酸单酯(monomethyl phthalate,MMP)和邻苯二甲酸(phthalic acid,PA).动力学研究表明,DMP降解过程符合haldane抑制模型,Vmax为643.2 mg.(g.h)-1,Ks和Ki分别171.0 mg.L-1和337.5 mg.L-1.电镜观察表明,颗粒污泥表面粗糙,微生物相丰富,含有丝状菌、球菌和短杆菌.     

HS-SPME-GC-MS法测定黑臭河流中二甲基三硫醚

该研究在优化分析条件的基础上,采用顶空固相微萃取(HS-SPME)和气相色谱/质谱(GC-MS)联用方法测定了黑臭河流水体中二甲基三硫醚的含量。通过研究萃取头涂层、萃取温度、萃取时间、水样体积和气相色谱进样口温度对二甲基三硫醚萃取效率的影响,得到了二甲基三硫醚最佳预处理和检测条件为:采用CAR-PDMS(75μm)萃取头,取20 mL待测水样在45℃恒温搅拌下顶空萃取30 min,进样口温度为250℃。采用优化后的方法对实际城市黑臭河流水样进行了检测,测得的二甲基三硫醚的浓度范围为5 853～8 939 ng/L。     

邻苯二甲酸二甲酯在颗粒活性炭中的穿透特性

在25℃条件下,研究了颗粒活性炭(GAC)对水中邻苯二甲酸二甲酯（DMP）的动态吸附特性及其影响因素.在不同进水流量（0.65～4 mL·min^-1）、GAC粒径（550～1　250　μm）、DMP初始浓度（50～400　mg·L^-1）和GAC炭量（0.75～1.4 g）条件下,考察了DMP在GAC柱中的穿透特性.研究表明,GAC对DMP的吸附容量较大,Yoon-Nelson模型能够很好地拟合各种工况下的动态穿透曲线;动态吸附容量随着进水流量和GAC粒径的增大而减小,相反,随着DMP初始浓度和GAC炭量的增大而增大.根据试验数据和Yoon-Nelson模型计算出穿透参数K′、T和穿透点t₁以及平衡点t₂.在建立了各影响因素与Yoon-Nelson穿透模型参数之间的关系基础上,得到了活性炭柱出水浓度与穿透时间和各影响因素之间的动态关系模型.