水-有机溶剂两相体系中甲基单胞菌Z201催化丙烯环氧化的初步研究

Lanne于1987年提出了生物催化剂工程（Biocatalyst engimeering）和介质工程（Medium enineering）的概念^[1].有机相生物催化中溶剂的选择也是介质工程的内容之一。纯酶在有机相中的催化作用已有大量报道^[2],但对完整细胞研究甚少。本文以甲基单胞菌（Methylomonos）Z201完整细胞为生物催化剂,丙烯环氧化为指标反应,研究有机溶剂对活性的影响并对催化活性-溶剂疏水性进行了相关性分析。研究了水-十六烷两相体系中十六烷含量和搅拦速度对丙烯环氧化速度的影响和细胞的操作稳定性。     

东亚大都市学生头型的比较研究

为了研讨居住区域的气候条件和社会经济环境对头型的影响,采用国际通用的人体测量法,调查测量了东亚三个国家四个集团３４７２名６－１７岁学生的头长和头宽,经统计学处理求得其平均值、头指数,回归方程,并作性差和地区差检验,其结果表明：中国大连学生为特圆头型,菲律宾马尼拉学生为圆头型,地理位置在大连和马尼拉之间的日本东京的学生的头型也位于二者之间,生活富裕集团的头长和头宽明显大于生活贫穷集团的学生,但头型二     

中国Btken-Ag的特性及其杀虫毒肽的研究

苏芸金芽孢杆菌肯尼亚亚种Ag株(Bacillus thuringiensis serovar.kenyae strainAg,以下简称为Btken-Ag)是血清型H4a-4c中对棉铃虫、粘虫等多种夜蛾科害虫具有高毒力的优良品系,经生理生化、H抗原、酯酶谱、抗生谱和质粒谱等性状比较分析,与标准株肯尼亚亚种023大体相同,但其质粒谱及伴孢晶体多肽组分与023明显有别.该菌株伴孢晶体多形,其主要杀虫成分为61000多肽,经ELISA同源分析,此毒肽与同血清型中的023、7501晶体蛋白高度同源,与商品生产株H3a-3b—HD-1株部分同源,与对蚊虫高效的H14-1897及球形芽孢杆菌Ts-1无同源性.此外,对H4中10株相关株、H7-5、HD-1及1897共13株进行了对棉铃虫、粘虫及蚊虫的杀虫毒力比较测定,其中Btken-Ag的优选株H4-1及b1-4对棉铃虫的毒力高于023株及HD-1株.     

Mutations of surface residues in Anabaena vegetative and heterocyst ferredoxin that affect thermodynamic stability as determined by guanidine hydrochloride denaturation.

The stability properties of oxidized wild-type (wt) and site-directed mutants in surface residues of vegetative (Vfd) and heterocyst (Hfd) ferredoxins from Anabaena 7120 have been characterized by guanidine hydrochloride (Gdn-HCl) denaturation. For Vfd it was found that mutants E95K, E94Q, F65Y, F65W, and T48A are quite similar to wt in stability. E94K is somewhat less stable, whereas E94D, F65A, F65I, R42A, and R42H are substantially less stable than wt. R42H is a substitution found in all Hfds, and NMR comparison of the Anabaena 7120 Vfd and Hfd showed the latter to be much less stable on the basis of hydrogen exchange rates (Chae YK, Abildgaard F, Mooberry ES, Markley JL, 1994, Biochemistry 33:3287-3295); we also find this to be true with respect to Gdn-HCl denaturation. Strikingly, the Hfd mutant H42R is more stable than the wt Hfd by precisely the amount of stability lost in Vfd upon mutating R42 to H (2.0 kcal/mol). On the basis of comparison of the X-ray crystal structures of wt Anabaena Vfd and Hfd, the decreased stabilities of F65A and F65I can be ascribed to increased solvent exposure of interior hydrophobic groups. In the case of Vfd mutants E94K and E94D, the decreased stabilities may result from disruption of a hydrogen bond between the E94 and S47 side chains. The instability of the R42 mutants is also most probably due to decreased hydrogen bonding capabilities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Molecular genetic analysis of the response of three soil microbial communities to the application of 2, 4-D

The responses of three different soil microbial communities to the experimental application of 2, 4-dichlorophenoxyacetic acid (2, 4-D) were evaluated with a variety of molecular genetic techniques. Two of the three soil communities had histories of prior direct exposure to 2, 4-D, and one had no prior direct application of any herbicide. Dominant 2, 4-D degrading strains isolated from these soils the previous year were screened for hybridization with three catabolic genes (tfdA, tfdAII, and tfdB) cloned from the well-studied 2, 4-D degradative plasmid, pJP4, revealing varying degrees of similarity with the three genes. Hybridization of total community DNA from the three soils with the tfd gene probes also indicated that pJP4-like tfd genes were not harboured by a significant percentage of the community. Community level response was evaluated by the comparison of different treatments by Random Amplified Polymorphic DNA (RAPD) fingerprints and by community DNA cross-hybridization. No differences between treatments within the same soil were detected in any of the RAPD fingerprints generated with 17 primers. Community DNA cross-hybridization also indicated that the application of 2, 4-D at the applied rates did not quantitatively affect the structure of the soil microbial communities present in the three soils during the time-frame studied.     

Haemodynamic and renin responses to prostacyclin infusion in Na depleted and Na restricted sheep

The haemodynamic and renin responses to prostacyclin (PGI2) infusion were examined in sheep during sodium depletion and dietary sodium restriction. The haemodynamic effects of PGI2 infusion in sodium depleted and sodium restricted sheep were similar to those obtained in the sodium replete animal. The renin proportionate response to PGI2 was not altered by sodium restriction but blunted by sodium depletion, compatible with the hypothesis that endogenous PGI2 is high in Na depletion.     

药用野生稻GBSS基因的系统发育及组织特异性表达

淀粉作为主要的碳水化合物在储藏能量方面发挥至关重要的作用。颗粒结合型淀粉合酶(GBSS)与直链淀粉的合成息息相关。尽管该酶的编码基因已在许多栽培植物中被分离和确定, 但有关它们在作物野生近缘种中的序列分歧和表达的研究却相对较少。该研究以药用野生稻(Oryza officinalis)为研究对象, 定性和定量地分析了GBSS编码基因的序列特点、与其它植物同源基因的进化关系以及在叶和种子中的表达情况。系统发育分析表明, 该酶在禾本科植物中分别由GBSSI和GBSSII基因编码。在药用野生稻中, 这2种基因所编码蛋白的氨基酸序列一致性为62%, 并且它们在不同器官内呈现时空分化表达, 其中GBSSI在种子中超强表达, GBSSII则主要在叶片表达。     

开启防御之门: 植物抗病小体

NLR蛋白是存在于植物和动物中的一个免疫受体大家族, 具有核苷酸结合域并富含亮氨酸重复序列。植物NLR通过识别病原菌特异效应子开启免疫信号转导。第1个植物NLR抗性蛋白于25年前克隆, 但其激活机制仍不清楚, 至今仍未获得一个完整的NLR蛋白结构。最近, 柴继杰、周俭民和王宏伟实验室合作解析了第一个植物完整NLR ZAR1激活前后的结构, 研究成果以两篇论文形式发表在“科学”杂志上, 填补了NLR介导的免疫信号转导研究领域的空白。该文简要总结了相关研究进展, 讨论了NLR免疫信号转导研究领域尚需解决的问题。     

走马胎的组织培养与快速繁殖

以走马胎(Ardisia gigantifolia)幼嫩茎段为外植体, 通过腋芽增殖的方式进行组织培养和快速繁殖研究。结果表明, 培养基MS+1.0 mg·L ^-1 6-BA+0.2 mg·L ^-1NAA和MS+0.5 mg·L ^-1 ZT均可用于腋芽的诱导和前期继代培养, 诱导率分别为89.3%和85.7%; 芽增殖最佳培养基为MS+0.5 mg·L ^-16-BA+0.1 mg·L ^-1ZT+0.1 mg·L ^-1NAA, 增殖系数为4.3倍; 根诱导最佳培养基为1/2MS+1.5 mg·L ^-1 IAA+1.0 mg·L ^-1 NAA, 生根率达92.3%, 且根系发达, 植株健壮; 生根苗在混合基质园土:泥炭:珍珠岩=3:1:1 (v/v/v )中移栽成活率为82%。该研究建立了走马胎种苗的组织培养快速繁殖技术体系, 且可应用于规模化生产。     

猕猴桃品种‘金桃’采收指标与果实软熟品质相关性研究

分别对河南省27个果园的中华猕猴桃（Actinidia chinensis Planch.）品种‘金桃’果实的5项采收生理指标及果实软熟时的8项品质性状进行测定,采用主成分分析法对果实软熟时的品质指标进行综合评分,并对果实的采收生理指标、果实软熟品质指标及综合分值间进行相关性分析。结果显示,采收时的生理指标（干物质、色度角、硬度和可溶性固形物）均与果实软熟品质综合分值间呈极显著相关,其中干物质相关系数最高,为0.437。干物质与体现果实软熟品质的关键指标（可溶性固形物、总糖和糖酸比）均呈极显著性相关。研究结果表明‘金桃’果实采收时,干物质含量是果实软熟时品质的重要评价指标,而可溶性固形物和色度角是评判采收期的辅助指标。