产乙醇酸氧化酶的重组毕赤酵母的构建及催化合成乙醛酸的研究

乙醇酸氧化酶（Go）是植物光呼吸途径中的一种关键酶,可以催化乙醇酸生产乙醛酸。从新鲜菠菜叶中提取总RNA,利用RT-PCR技术获得编码GO基因的cDNA片断。通过基因重组将GO基因克隆到载体pA0815中,构建了胞内表达载体pA0815／GO,重组质粒经电转整合至甲醇营养酵母GS115染色体。在混合碳源为10g/L山梨醇和0．5g/L甲醇的培养条件下,细胞的GO酶活达到474IU／g（DCW）。利用该重组毕赤酵母作为催化剂生产乙醛酸,结果表明：在乙醇酸浓度为0．25mol／L,重组酵母湿菌体为10dL,黄素单核苷酸（FMN）浓度为0．01mmol／L,pH8．0,20℃,反应18h后乙醛酸的产率达到51．8％。     

乙醇酸氧化酶在蕨类植物中的分布及其特性

试验证明在12科17种蕨类植物叶片中都存在乙醇酸氧化酶活性,但不同种植物的酶活性相差甚大,从10~(-5)～10~(-3)mmol乙醛酸·mg~(-1)蛋白质·10~(-1)min,相差100倍左右。蕨类植物乙醇酸氧化酶的K_m(乙醇酸)值为0.36×10~(-3)mol/l,最适pH值为8.2;HPMS(α-羟基-2-/吡啶甲磺酸)对其活性具有强烈抑制作用,抑制率为92.3～93.6％。这些结果表明,蕨类植物乙醇酸氧化酶的特性与种子植物(如菠菜)的十分相似。     

五味子甲素对大鼠成骨细胞增殖分化的影响

目的　探讨五味子甲素体外对大鼠成骨细胞增殖与分化的影响。方法　用改良的组织块法分离培养新生大鼠颅骨成骨细胞 ,五味子甲素以不同浓度加入细胞培养体系 ,作用不同时间后 ,用MTT法检测成骨细胞的增殖情况 ;用对硝基苯二钠基质动力学法 (PNPP)测定细胞内碱性磷酸酶的活性 ,用改良的Lowry法测蛋白含量。 结果　五味子甲素在 0 75× 10 -5mol/L及 0 75× 10 -9mol/L浓度范围内 2 4h ,72h ,0 75× 10 -4 ～ 0 75× 10 -7mol/L 48h促进成骨细胞增殖 ,在 0 75× 10 -5～ 0 75× 10 -6mol/L浓度范围内 48h提高成骨细胞内碱性磷酸酶的活性。结论　五味子甲素体外能促进成骨细胞的增殖与分化。     

荞麦与大豆叶片乙醇酸氧化酶的纯化和性质比较研究

分别从荞麦与大豆叶片中部分纯化了乙醇酸氧化酶 (GO ,EC1 .1 .3 .1 ) ,并研究其部分性质。结果显示荞麦与大豆叶片中GO的催化特性有明显差异 :大豆叶片中GO对乙醇酸Km值为 0 .3 1mmol/L ,对乙醛酸Km值为 1 .98mmol/L。外源草酸对GO氧化乙醇酸活性影响很小 ,但对其氧化乙醛酸活性抑制明显 ,5mmol/L草酸可抑制 44%。而荞麦叶片中GO性质有所不同 :GO对乙醇酸Km为 0 .46mmol/L ,对乙醛酸Km为 0 .85mmol/L。草酸对荞麦GO氧化乙醇酸活性影响也很小 ,对其氧化乙醛酸活性的抑制作用明显小于大豆 ,5mmol/L草酸只抑制 2 4%。上述研究结果表明 ,荞麦GO对乙醛酸的亲和力明显强于大豆 ,并且草酸对其GO氧化乙醛酸活性影响较小。因此相对于大豆而言 ,GO可能在荞麦叶片草酸合成中起重要作用。     

菠菜叶片乙醇酸氧化酶的氧化甘油酸活性

首先从菠菜叶片中纯化了乙醇酸氧化酶（GO）。通过鉴定反应中氧的消耗以及反应产物H2O2的生成,证实菠菜GO具有氧化光呼吸途径中间代谢物甘油酸的活性。该氧化活性依赖于辅因子FMN和FAD,而不依赖核黄素和光黄素;其最适反应pH值为8．0,Km（甘油酸）值为7．14mmol／L,kcat值为1．04s^-1,活化能为17．29kJ／mol;草酸和丙酮酸对该氧化活性有明显的抑制作用,其中前者为典型的竞争性抑制。进一步通过两底物竞争作图表明：菠菜叶片GO氧化甘油酸反应和氧化乙醇酸反应为同一活性中心所催化。     

不同菌株白僵菌代谢产物对大鼠肝线粒体单胺氧化酶的抑制作用研究

对8株白僵菌[Beauveriasp.]代谢产物的抑制单胺氧化酶的活性进行测定,发现菌株Ba02和Ba05的乙酸乙酯提取物在终浓度为55μg/mL时,对单胺氧化酶A型(MAO＿＿A)有较强的抑制活性,其抑制率分别为95.9%和83.4%;Ba02及Ba03菌株脂溶性成分在终浓度为55μg/mL时对单胺氧化酶B型(MAO＿B)有较强的抑制活性,其抑制率分别为94.8%和84.1%。浓度和抑制活性关系研究表明在一定浓度范围内Ba02菌株脂溶性成分对MAO的抑制活性呈量效关系,经计算得出其对MAO＿A、MAO＿B抑制的IC50分别为18.3μg/mL、28.2μg/mL;抑制特征曲线表明Ba02菌株脂溶性成分对MAO＿A呈竞争型抑制,对MAO＿B为混合型抑制,Km值分别为0.47×10-5mol/L,0.11×10-5mol/L。     

植物的乙醇酸氧化酶

乙醇酸氧化酶存在于植物细胞过氧物酶体中,是一种黄素蛋白,以FMN为辅基,含8个亚基。催化乙醇酸氧化为乙醛酸和乙醛酸氧化为草酸。受光活化。硫化钠和氰化物促进其活性:巯基抑制剂、α-羟基磺酸类、α-羟基丁炔酸抑制其活性。多种代谢物对其活性有调节作用。为光呼吸的关键酶之一,其活性随植物发育、矿质营养及感病而发生变化。     

乙醇酸氧化酶纯化方法的改进

乙醇酸氧化酶（GO）是光呼吸的关键酶。但目前报道的GO的Mr和等电点等基本参数相差很大,重复性也不好[2,3,5～11]。本实验拟改进其纯化方法以期提高其重复性。材料与方法菠菜（Spinaciaoleracea）和菜心（Brassicacampestris）均购自市场。GO的提纯基本按文献2、3、6,只作添加FMN一项改进。具体操作如下：绿叶用100mmol·L－－‘的磷酸缓冲液（pH8．0）提取粗蛋白,过滤,4000Xg离心取上清液,加10％HAC调到PH53;然后以4000Xg离心取上清液,经15％～30％（NH;）iS04分步沉淀;高GO活性的沉淀蛋白用5mmol·L‘Tris－HCI（pH…     

螺旋藻过氧化氢酶的比较研究

采用碘量法对毛乌素沙地碱湖的钝顶螺旋藻S1 与国外引进的钝顶螺旋藻S2 和极大螺旋藻S3 的过氧化氢酶 (CAT)进行了比较研究。结果表明 :S1 、S2 和S3CAT活性在 2 5℃、pH 7 0时分别为 41 0 7U/g·FW、 550 4U/g·FW和 370 3U/g·FW ;Km值分别为 5 0× 1 0 - 2mol/L、 5 4× 1 0 - 2 mol/L和 3 8× 1 0 - 2 mol/L ;最适温度分别为 2 5℃、 2 5℃和 40℃ ;最适pH值分别为 7 2、 7 6和 7 8。内蒙古特有的S1 CAT对温度和pH适应范围宽 ,且在低温、高温和强碱下的活性比引进种的高。     

螺旋藻过氧化氢酶的比较研究*

采用碘量法对毛乌素沙地碱湖的钝顶螺旋藻S1 与国外引进的钝顶螺旋藻S2 和极大螺旋藻S3 的过氧化氢酶 (CAT)进行了比较研究。结果表明 :S1 、S2 和S3CAT活性在 2 5℃、pH 7 0时分别为 41 0 7U/g·FW、 550 4U/g·FW和 370 3U/g·FW ;Km值分别为 5 0× 1 0 ^{- 2}mol/L、 5 4× 1 0 ^{- 2} mol/L和 3 8× 1 0 ^{- 2} mol/L ;最适温度分别为 2 5℃     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.