蔬菜中农药残留检测技术研究进展

对目前蔬菜中农药残留分析检测方法及其前处理过程以及快速检测技术作了综述。固相萃取(SPE)、超临界流体萃取(SFE)等新的萃取方法已逐渐代替了液-液萃取(LLE)等传统提取方法。色谱技术是农药残留分析中的重要手段。毛细管气相色谱(CGC)、高效液相色谱(HPLC)及其联用技术是现阶段农药残留分析中的主要检测方法。并指出了今后该领域的研究方向。     

微生物酶法消除黄酒中氨基甲酸乙酯研究进展

氨基甲酸乙酯(Ethyl carbamate,EC)具有致癌性,广泛存在于酒精饮料中。我国的黄酒因EC含量高而带来的食品安全问题越来越受到人们的关注。微生物酶法消除黄酒中的EC具有直接、高效的特性而被深入研究。文中从黄酒中EC的形成机制、酸性脲酶研究现状、氨基甲酸乙酯水解酶研究现状等方面概述了微生物酶法消除黄酒中EC的研究进展及存在的问题。并针对这些问题,提出了寻找新型氨基甲酸乙酯水解酶、Fe~(3+)依赖型双功能酸性脲酶食品级表达与定向进化及双酶并用将尿素和EC一起消除的策略。     

γ-羟基丁酸的分析研究进展

作为高效能的中枢神经抑制剂,γ-羟基丁酸（GHB）其相关物质γ-丁内酯（GBL）和1,4-丁二醇（1,4-BD）的滥用现象越来越严重,由于它们强烈的镇静及健忘效果常常被用作迷奸药,带来了严重的社会问题。由于在体内天然存在GHB,而且其在摄入后消除迅速,这增加了体内GHB及其相关物质的检测和分析评价难度。本文在对GHB及其相关物质的理化性质阐述基础上,综述了它们的提取技术及分析方法研究进展,主要阐述了液．液提取、固相萃取等提取方法与气相色谱法、气相色谱-质谱联用法、高效液相色谱法、液相色谱．质谱联用法、毛细管电泳法等在分析不同检材中GHB及其相关物质的应用,这也为国内法庭案件中GHB及其相关物质的滥用及相关案件提供了可供参考的法庭科学检测、分析研究方法。     

Agrobacterium tumefaciens OAH-01产脲酶发酵培养基优化

氨基甲酸乙酯( EC)是大多数发酵制品中的潜在致癌物,而尿素是EC的最主要前体物质之一,因此需要采取相关措施控制发酵制品中尿素的含量。向酒体中添加脲酶具有安全、高效和处理条件温和等优点,是FDA推荐的降低EC 含量的优先方法。微生物是脲酶的主要来源,可利用其实现脲酶的大规模生产。本文以产脲酶根癌农杆菌Agrobacterium tumefaciens OAH-01为研究对象,考察了该菌株的生长曲线和产酶曲线,证明该菌株产脲酶属生长关联型,且能在较短时间内达到最大产酶量,此外还研究了发酵培养基组成对该菌发酵产酶的影响,通过单因素及正交试验优化确定了最佳发酵培养基组成(g/L)：蛋白胨20,酵母粉5,葡萄糖5,FeCl30.54,Na2HPO40.5, KH2 PO40.5,NiSO40.1,起始 pH 7.0。在最适条件下发酵16 h,菌悬液中脲酶酶活可达1.077 U/mL,为优化前的2.4倍。超声破碎后细胞上清中的脲酶活性为0.419 U/mL,为优化前的4.4倍。     

金针菇中棒曲霉素高效液相色谱检测法的研究

对金针菇中棒曲霉素的分析检测方法进行了研究,旨在建立一种以液-液萃取为前处理方法,采用高效液相色谱(HPLC)分析检测金针菇中棒曲霉素含量的方法。主要研究结果如下:通过组织破碎,制备金针菇汁,采用乙酸乙酯重复萃取,用碳酸钠溶液净化萃取液,制备金针菇供试品。该方法处理和测定棒曲霉素精密度高,检出限低。棒曲霉素标准品的标准曲线为y=112.8x-14.23,R2=0.998 4,标准曲线范围为0.01~25μg/m L。     

定点突变提高解淀粉芽孢杆菌JP-21脲酶应用特性

氨基甲酸乙酯(Ethylcarbamate,EC)是一种存在于发酵食品和酒精饮料中的可致癌物,过量摄入可能会影响人体健康。酶法降解是减少发酵食品中氨基甲酸乙酯及其前体尿素含量的有效方法之一。脲酶具有氨基甲酸乙酯水解酶和尿素酶两种活性,因此在减少发酵食品中氨基甲酸乙酯及其前体尿素方面具有良好的应用前景。目前脲酶降解发酵酒精饮料中氨基甲酸乙酯面临的主要问题是脲酶对氨基甲酸乙酯的催化活性及亲和力较低,因而其降解效果不理想。文中成功在大肠杆菌Escherichia coli中表达了来源于解淀粉芽孢杆菌Bacillus amyloliquefaciens JP-21的脲酶,表达水平为尿素酶3 291.74 U/L,氨基甲酸乙酯水解酶227.26 U/L。通过模拟脲酶中催化亚基UreC与氨基甲酸乙酯对接的结构,确定了M326和M374这两个影响酶与底物结合的位点。采用点饱和突变获得了3株氨基甲酸乙酯水解酶活性提高的突变体M374A、M374T和M326V,以EC为底物时的Km分别为101.84mmol/L、129.49 mmol/L和121.67 mmol/L,比野生型分别降低了37.47%–50.82%。突变体可以降解黄酒中97%的尿素,M374T对黄酒中EC的降解效果最好,可将黄酒中EC从513.90μg/L降至393.57μg/L,降解率是野生脲酶的1.97倍。研究结果对今后改造脲酶催化特性和改善其应用特性具有重要意义,可为开发减控发酵食品中的微生物代谢氨(胺)类危害物策略提供参考。     

微滤技术提高黄酒胶体稳定性的探讨

对黄酒酒液及沉淀物进行分析,确定高分子蛋白质在蛋白质沉淀中所起的作用。进而应用０．４５μｍ微滤膜处理酒液,发现微滤能大量去除形成大颗粒的前驱物质－高分子蛋白质,明显改善黄酒稳定性。     

高效液相色谱-荧光检测法分析酱油中的氨基甲酸乙酯

建立了高效液相色谱-荧光法检测酱油中氨基甲酸乙酯的分析方法.首先用乙酸乙酯萃取酱油中的氨基甲酸乙酯,再经减压旋转蒸发浓缩得待测样品.其次确定了衍生化反应条件:取1.0 mL待测样品,加入200 μL 0.02 mol/L占吨醇,再加入100 μL 1.5 mol/L盐酸于暗处反应30min.实验结果表明:该方法标准曲线良好,线性范围为10～200 μg/L,相关系数为R2=0.988,氨基甲酸乙酯的出峰时间为14.882 min,平均回收率为100.12％.最低检测限为5μg/L,比已经发表的最低检测限(20 μg/L)要低.最后对市售酱油S1～S6样品中的氨基甲酸乙酯含量进行了检测,表明市售酱油S1～S6中氨基甲酸乙酯的含量为31.25～114.78μg/L.本文所建立的方法具有简便快捷、灵敏度高的特点,可满足对酱油中氨基甲酸乙酯含量检测的需要.     

解淀粉芽孢杆菌诱变育种及其突变株在降低酱油中氨基甲酸乙酯的应用

【目的】通过诱变育种提高解淀粉芽孢杆菌JY06利用精氨酸的能力,并将其用于降低酱油中的氨基甲酸乙酯及前体,从而提高酿造酱油的安全性。【方法】采用等离子诱变和紫外诱变两种诱变育种方法对解淀粉芽孢杆菌JY06进行突变,应用高通量筛选手段获得具有高精氨酸利用能力的突变株,验证突变株降低酱油中氨基甲酸乙酯的能力。【结果】获得了12株精氨酸利用能力提高的突变株,与出发菌株JY06相比,突变株C12和E6可使酱油中瓜氨酸含量分别降低了15.6%和14.7%,EC的含量分别降低了19.3%和13.1%。【结论】通过等离子诱变和紫外诱变进一步提高了解淀粉芽孢杆菌JY06降低酱油中EC及其前体瓜氨酸的能力,具有控制或减少酱油中生物危害物的应用潜力。     

微藻胞间植物激素甄别方法与研究进展

植物激素是一类微量的内源化合物,可能是微藻生命活动过程中的通用"语言"。植物激素甄别是认知微藻群体感应和胞间通讯机制的关键。然而,由于植物激素具有超微量、性质复杂和干扰物质共存的特点,选择适宜的提取浓缩方法、提高检测灵敏度、减小基质效应和区分同分异构体仍是甄别植物激素的难点问题。本文综述了植物激素提取与检测的研究现状,关注了各类样品制备植物激素的方法和案例,重点阐释了固相萃取法、液液萃取法、磁性固相萃取法、液液微萃取法等提取方法以及液相色谱、液相色谱串联质谱、毛细管电泳等检测方法的优缺点,展望了利用串联固相萃取法从藻液提取痕量植物激素的前景,以及采用超高效液相色谱-线性离子阱-静电场轨道阱组合式高分辨质谱检测植物激素的方法,以期为藻际微生物生态相关研究提供方法参考。     

萜烯类与苯丙酸类花香挥发物的生物合成与调节

随着花香挥发物提取和检测技术的不断发展以及该技术与分子生物学研究的结合,花香挥发物的生物合成途径和调节机制的研究取得了较大进展,为花香的遗传控制和育种研究奠定了良好的基础。萜烯类和苯丙酸类/苯环型化合物是植物花香挥发物的重要化学成分,它们分别由甲羟戊酸-甲基赤藓醇磷酸途径、莽草酸途径等途径生成,调节机制较为复杂,但以前体物生物合成调节为主。两类花香物质在许多行业得到了应用广泛,但相关研究有待于进一步深入。     

拟南芥表皮毛发育的分子机制

拟南芥(Arabidopsis thaliana)表皮毛是存在于地上部分表皮组织的一种特化的、典型的单细胞结构。近几年, 对其发育的分子调控机制的研究取得了很大进展, 已克隆出大量的控制表皮毛不同发育阶段的基因, 通过对这些基因的功能解析揭示出表皮毛发育及生长调节的内在分子机制。该文对拟南芥表皮毛发育的最新研究进展进行综述, 并展望了关于表皮毛的研究方向及潜在的应用价值。     

植物物种形成的模式与机制

物种形成是指由已有的物种通过各种进化机制进化出新物种的过程。持续不断的物种形成产生了地球上灿烂的生物物种多样性。然而,研究人员对物种形成的模式与机制的了解却非常有限。一直以来,谱系分裂被认为是最重要的物种形成模式,但在植物中,谱系融合,即通过杂交形成新物种的过程,也是一个非常重要的物种形成模式。经过几十年的研究才逐渐认识到,生殖隔离是差异适应和遗传漂变的副产品,而不是物种形成的前提。相比合子形成后隔离,合子形成前的隔离在物种形成过程中更早地发挥作用。合子形成前的隔离,尤其是生态地理的隔离是植物中最重要的隔离机制。一些基于QTLs分析的研究发现,基因组中的少数主效位点在物种形成中起了关键作用,并且这些位点往往受到自然选择的作用。适应性辐射往往发生在隆起的山脉和新形成的岛屿上,很可能与这些地方能够提供很多可利用的生态位有关。最新的物种形成理论认为,基因是物种形成的基本单位,不同的物种可以在非控制物种差异适应性状的位点上存在基因流。这一观点为植物物种形成的研究提供了新的思路。随着植物物种形成研究的深入,越来越多植物物种形成基因被分离,包括花色素苷合成通路和S-基因座上的一些关键基因,揭示了植物物种形成的分子机制。前期的研究主要集中在模式植物和农作物上,许多生态上非常有趣的非模式植物还未得到广泛的研究。在未来的研究中,还需要更多来自非模式植物的例子以全面理解植物物种形成的多样化机制。     

Wood formation in Angiosperms

Wood formation is a complex biological process, involving five major developmental steps, including (1) cell division from a secondary meristem called the vascular cambium, (2) cell expansion (cell elongation and radial enlargement), (3) secondary cell wall deposition, (4) programmed cell death, and (5) heartwood formation. Thanks to the development of genomic studies in woody species, as well as genetic engineering, recent progress has been made in the understanding of the molecular mechanisms underlying wood formation. In this review, we will focus on two different aspects, the lignification process and the control of microfibril angle in the cell wall of wood fibres, as they are both key features of wood material properties.     

拟南芥表皮毛发育的分子机制

拟南芥（Arabidopsis thaliana）表皮毛是存在于地上部分表皮组织的一种特化的、典型的单细胞结构。近几年,对其发育的分子调控机制的研究取得了很大进展,已克隆出大量的控制表皮毛不同发育阶段的基因,通过对这些基因的功能解析揭示出表皮毛发育及生长调节的内在分子机制。该文对拟南芥表皮毛发育的最新研究进展进行综述,并展望了关于表皮毛的研究方向及潜在的应用价值。     

Statistical Analysis of Uniparental Disomy Data Using Hidden Markov Models

Genetic studies of uniparental disomy (UPD) employing many markers have helped geneticists to gain a better understanding of the molecular mechanisms underlying nondisjunction. However, most existing methods cannot simultaneously analyze all genetic markers and consistently incorporate crossover interference; they thus fail to make the most use of genetic information in the data. In the present article, we describe a hidden Markov model for multilocus uniparental disomy data. This method is based on the chi-square model for the crossover process and can simultaneously incorporate all marker information including untyped and uninformative markers. We then apply this novel method to analyze a set of UPD15 data.     

Mammalian hybrid zones: a review

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Analysis of Nephron Composition and Function in the Adult Zebrafish Kidney

The zebrafish model has emerged as a relevant system to study kidney development, regeneration and disease. Both the embryonic and adult zebrafish kidneys are composed of functional units known as nephrons, which are highly conserved with other vertebrates, including mammals. Research in zebrafish has recently demonstrated that two distinctive phenomena transpire after adult nephrons incur damage: first, there is robust regeneration within existing nephrons that replaces the destroyed tubule epithelial cells; second, entirely new nephrons are produced from renal progenitors in a process known as neonephrogenesis. In contrast, humans and other mammals seem to have only a limited ability for nephron epithelial regeneration. To date, the mechanisms responsible for these kidney regeneration phenomena remain poorly understood. Since adult zebrafish kidneys undergo both nephron epithelial regeneration and neonephrogenesis, they provide an outstanding experimental paradigm to study these events. Further, there is a wide range of genetic and pharmacological tools available in the zebrafish model that can be used to delineate the cellular and molecular mechanisms that regulate renal regeneration. One essential aspect of such research is the evaluation of nephron structure and function. This protocol describes a set of labeling techniques that can be used to gauge renal composition and test nephron functionality in the adult zebrafish kidney. Thus, these methods are widely applicable to the future phenotypic characterization of adult zebrafish kidney injury paradigms, which include but are not limited to, nephrotoxicant exposure regimes or genetic methods of targeted cell death such as the nitroreductase mediated cell ablation technique. Further, these methods could be used to study genetic perturbations in adult kidney formation and could also be applied to assess renal status during chronic disease modeling.     

Origin, Persistence and Biological Activity of Genetic Material in Prebiotic Habitats

Molecules which store genetic information (i.e. RNA and DNA) are central to all life on Earth. The formation of these complex molecules, and ultimately life, required specific conditions, including the synthesis and concentration of precursors (nucleotides), the joining of these monomers into larger molecules (polynucleotides), their protection in critical conditions (like those probably existing in primeval habitats), and the expression of the biological potential of the informational molecule (its capacity to multiply and evolve). Determining how these steps occurred and how the earliest genetic molecules originated on Earth is a problem that is far from being resolved. Recent observations on the polymerization of nucleotides on clay surfaces and on the resistance of clay-adsorbed nucleic acids to environmental degradation suggest that clay minerals could have acted as a resting place for the formation and preservation of prebiotic genetic molecules, whatever they were, and for the self-organization of the first auto-replicating systems. In the present work, the molecular characteristics and biological activity of different nucleic acids (DNA, RNAs) adsorbed/bound on clay minerals are discussed in the light of their possible role in ancestral environments.     

Tocopherol biosynthesis: chemistry, regulation and effects of environmental factors

Tocopherols are lipophilic antioxidants and together with tocotrienols belong to the vitamin-E family. The four forms of tocopherols (??-, ??-, ??- and ??-tocopherols) consist of a polar chromanol ring and lipophilic prenyl chain with differences in the position and number of methyl groups. The biosynthesis of tocopherols takes place mainly in plastids of higher plants from precursors derived from two metabolic pathways: homogentisic acid, an intermediate of degradation of aromatic amino acids, and phytyldiphosphate, which arises from methylerythritol phosphate pathway. The regulation of tocopherol biosynthesis in photosynthetic organisms occurs, at least partially, at the level of key enzymes as such including p-hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27), homogentisate phytyltransferase (HPT, EC 2.5.1.-), tocopherol cyclase (TC, EC 5.4.99.-), and two methyltransferases. Tocopherol biosynthesis changes during plant development and in response toward different stresses induced by high-intensity light, drought, high salinity, heavy metals, and chilling. It is supposed that scavenging of lipid peroxy radicals and quenching of singlet oxygen are the main functions of tocopherols in photosynthetic organisms. The antioxidant action of tocopherols is related to the formation of tocopherol quinone and its following recycling or degradation. However, until now, the mechanisms of tocopherol degradation in plants have not been established in detail. This review focuses on mechanisms of tocopherols biosynthesis and its regulation in photosynthetic organisms. In addition, available information on tocopherol degradation is summarized.