黄鳝DEAD-box家族PL10基因的克隆与序列分析

通过PCR克隆的方法，从黄鳝(Monopterus albus)中得到两个PL10基因的cDNA片段Mo PL10A和Mo PL10B，长度均为1．127kb，推测其编码375个氨基酸的蛋白片段．结合其他PL10类同源物序列，对这两条cDNA进行了分析和初步的功能推测．根据此片段的氨基酸序列构建的系统发育树与形态分类结果一致．在不同组织中的RT—PCR结果表明Mo PL10A和Mo PL10B的mRNA在各组织中的分布有差异．     

胃瘤线虫与宿主黄鳝组织的酯酶同工酶分析

采用不连续凝胶垂直板电泳分析胃瘤线虫、线虫包囊以及黄鳝的各组织,比较样品酯酶电泳结果的异同,分析其相互之间的关系.酯酶在黄鳝的各个组织、胃瘤线虫与线虫包囊中均有表达,并且呈现出一定的特异性.电泳结果表明黄鳝心脏和肌肉的酯酶只有一条弱酶带,其它组织都有三条染色明显的条带,说明黄鳝心脏和肌肉的酯酶发挥的水解功能要低于其它组织;胃瘤线虫包囊具有与黄鳝的肠道相似的酶带,但其活性较弱,因此,推测其已经丧失了肠道组织的水解吸收营养物质的大部分功能;胃瘤线虫有4条酶带,其中2ab和2b是胃瘤线虫特有的酶带,而1a和2a是胃瘤线虫与其包囊、黄鳝的肠道、性腺、肾脏、肝脏共有的酶带,由此推测线虫与黄鳝之间也可能存在着协同进化的关系.     

甲基单胞菌GYJ3催化环氧丙烷的半连续合成

利用含有甲烷单加氢酶（MMO）的甲烷氧化细菌整催化丙烷环氧化制取环氧丙烷,其产物抑制和辅酶NADH消耗是反应难以连续进行的主要原因,采用甲烷再生NADH,研究了丙烯和甲烷共氧化和氧物氧丙烷积累对甲基单胞菌GYJ3的环氧化活性的影响,并考察了在具有产物连续收系统的两段式生物反应器中用细菌胞悬浮液半连续生产环氧丙烷的可行性,将再生和环氧化过程分开进行,以减小甲烷和丙烯的竞争抑制,通过连续抽提产物环氧丙烷,克服了产物抑制,该半连续过程分别在不同的温度下共进行了70h,产生环氧丙烷438μmol。     

A Promiscuous Halogenase for the Derivatization of Flavonoids

Halogenation often improves the bioactive properties of natural products and is used in pharmaceutical research for the generation of new potential drug leads. High regio- and stereospecificity, simple reaction conditions and straightforward downstream processing are the main advantages of halogenation using enzymatic biocatalysts compared to chemical synthetic approaches. The identification of new promiscuous halogenases for the modification of various natural products is of great interest in modern drug discovery. In this paper, we report the identification of a new promiscuous FAD-dependent halogenase, DklH, from Frankia alni ACN14a. The identified halogenase readily modifies various flavonoid compounds, including those with well-studied biological activities. This halogenase has been demonstrated to modify not only flavones and isoflavones, but also flavonols, flavanones and flavanonols. The structural requirements for DklH substrate recognition were determined using a feeding approach. The homology model of DklH and the mechanism of substrate recognition are also proposed in this paper.     

黄鳝体内新棘衣棘头虫种群季节动态与分布

通过对鄱阳湖黄鳝体内新棘衣棘头虫感染情况的调查,结果发现在870尾黄鳝中,有231尾黄鳝的消化道中有棘头虫感染,感染率为26.5%,丰盛度为9.79±13.9。不同月份之间黄鳝体内新棘衣棘头虫的感染率存在显著的差异(P<0.005);感染率在11、12和1月出现3个峰值,分别为55.7%、48.5%和44%,而2月份的感染率最低,为11.2%。5月份的丰盛度最高,达到22.71±13.90;2月份的丰盛度也最低,为3.00±1.27。不同体长组黄鳝体内棘头虫的感染率存在极显著性差异;其中体长为55.1～60.0cm的黄鳝体内棘头虫的感染率最高,体长小于21cm的黄鳝没有新棘衣棘头虫感染。棘头虫感染与未感染黄鳝之间的肥满度没有显著的差异。另外,利用比值衡量与负二项分布拟合证明棘头虫在黄鳝消化道内呈聚集分布。     

Effect of temperature and pressure on growth and methane utilization by several methanotrophic cultures

Several methanotrophic microorganisms, i.e.,Methylococcus capsulatus (Bath),Methylomonas albus (BG-8),Methylosinus trichosporium OB3b, andMethylocystis parvus (OBBP), were evaluated for growth and methane utilization. The effect of temperature was examined in the range of 25 to 45°C for growth and methane utilization. The temperature variations (25–35°C) had minimal effect on growth ofM. albus and M. parvus. Methane consumption varied at different temperatures with a maximum of 0.67 mol%/h and 0.53 mol%/h. at 30 and 35°C, respectively, forM. albus and M. parvus. The growth and methane consumption was slower forM. trichosporium OB3b as a maximum methane consumption of 0.07 mol%/h was obtained at 25°C and growth was inhibited at 35°C.M. capsulatus grew the best at 37°C and growth was affected at higher temperature of 45°C. Of the different cultures examined,M. albus andM. capsulatus grew the best and were further evaluated for the effect of pressure in the range of 10–50 psi. The results obtained usingM. albus demonstrated an enhancement in methane consumption rate by fourfold and final cell concentration by 40% at a pressure of 20 psi by injecting a methane/oxygen mixture, however further increase in the pressure up to 50 psi inhibited the growth. The inhibition was not seen with nitrogen incorporated mixture of oxygen and methane, which suggest that the high partial pressure of methane and/or oxygen are inhibitory for the growth ofM. albus. M. capsulatus was more sensitive to pressure as evidenced by inhibition at the relatively low pressure of 10 psi     

环氧丙烷的连续生物合成

 利用含有甲烷单加氧酶（MMO）的甲基单胞菌Methylomonassp．GYJ3整细胞催化丙烯环氧化制取环氧丙烷时,辅酶NADH的消耗和产物抑制是反应难以连续进行的主要原因．为解决这些问题,通过批式反应考察了丙烯－甲烷共氧化反应合成环氧丙烷的可能性,发现反应气体中甲烷含量为30％时环氧丙烷的产量较高．在搅拌式生物反应器中,通过最佳配比的混合反应气体的连续循环将产物环氧丙烷抽提出来,从而克服了产物抑制．该生物反应器最初的环氧丙烷日产量为268μmol,连续操作12d后,MMO仍保留96％的初始活性．     

Relationships between Nitrogen Translocation and Accumulation in Growing Plant Parts of Grain Legumes

Abstract

Grain legumes absorbed mineral ¹⁵N at every stage of development and transported it directedly (just as symbiotically fixed ¹⁵N₂) into the plant parts growing at the respective stage. The ¹⁵N accumulation in the grains after long-lasting ¹⁵N supply can be ascribed, for the major part, to a secondary ¹⁵N translocation after a temporary incorporation into older plant parts (leaves, stem). Inhibition experiments with antibiotics revealed no direct relation between the accumulation of amino acid ¹⁵N in growing pods and seeds and the protein synthesis in this target organs. It may include, however, processes of (active ?) uptake and transport with a possible contribution of carrier systems specific for distinct amino acids.     

新棘衣棘头虫及黄鳝组织酯酶同工酶分析

采用不连续聚丙烯酰胺垂直凝胶电泳分析新棘衣棘头虫和黄鳝的肌肉、肝胰脏、肠道、脾脏、性腺、肾脏及心脏7种组织。电泳结果表明酯酶在黄鳝各组织及新棘衣棘头虫中均有表达,并且具有明显的特异性。肌肉组织仅3条酶带,比其它组织的特异性较明显;肝胰脏组织酯酶活性最强,有12条     

固定化Methylomonas Z201细胞：甲烷单加氧酶的活性和稳定性

分别以海藻酸钙和砂子为载体，采用包埋和吸附技术固定化ＭｅｔｈｙｌｏｍｏｎａｓＺ２０１细胞．以丙烯环氧化为指标反应，系统研究固定化对ＭｅｔｈｙｌｏｍｏｎａｓＺ２０１细胞ＭＭＯ活性和稳定性的影响．结果表明，对包埋细胞，合适的负载量和粒径为保留较高ＭＭＯ活性所必需．砂子对细胞的吸附能力中等．外源性电子给体甲酸钠对游离和固定化细胞的ＭＭＯ活性影响不同．固定化细胞的最适ｐＨ值和温度与游离细胞相同，但活化能降低．固定化细胞保留游离细胞ＭＭＯ活性的６０—７０％，操作稳定性、热稳定性、贮存稳定性均有所提高．