微生物转谷氨酰胺酶的纯化方法和酶学性质研究

由Streptoverticillium mobaTaense发酵生产的转谷氨酰胺酶经过除茵体、超滤浓缩、乙醇沉淀、干燥后得到粗酶产品,其活力回收率约70％。又经Superdex-75凝胶过滤和Source 30S阳离子交换两步纯化后得到纯酶,最终酶活力收率约37％。酶最适温度为50℃,在40℃以下稳定性良好;最适pH为6．0,pH4．0～8．0时比较稳定。离子强度对酶影响很小。     

竹笋脚料过氧化物酶的提纯及酶学性质的研究

竹笋经加工成食品后,大量脚料被丢弃,严重浪费资源,污染环境。文中采用水抽提、硫酸铵分级沉淀、丙酮分级沉淀和CM-52离子交换层析三步法从竹笋脚料中快速提取并纯化该酶;同时对该酶部分的酶学性质（温度、pH对酶促反应的影响、酶的热稳定性、酸碱稳定性）进行了考查。结果表明经过纯化后的过氧化物酶的Rz值达到2．5,纯化倍数为12倍,回收率为28％。最适反应温度为55℃,最适pH为6．8,且其温度和pH的适用范围均较宽,热稳定性和酸碱稳定性均较高的中性同工酶。这些优越的酶学性质能为竹笋脚料过氧化物酶的应用提供依据。     

黄瓜几丁质酶的诱导,提取纯化及其基本性质（简报）

3周龄黄瓜幼苗经乙烯利处理后,诱导了几丁质酶活力。叶片提取液经20％和60％饱和度的两步硫酸铵沉淀,通过再生几丁质亲和层析后,纯化制备的SDS－PAGE显示单一谱带。酶学特性呈现pH2.7和pH7．1两个最适反应pH和50℃的最适反应温度。纯化的酶对几种病原菌的生长有一定的抑制作用。     

对硫磷真菌降解酶的分离纯化和性质

黑曲霉AspergillusnigerY－8在液体培养基中30℃培养5d,其菌体用超声波破碎后,经硫酸铵沉淀、DEAE-纤维素层析、Sephadex－100凝胶过滤,得到凝胶电泳均一的对硫磷降解酶,其比活为6.94,提纯倍数为13.6倍,收率为17．4％。酶作用的最适温度是50℃,最适pH为7.5,在40℃以下和pH6.0～9.0之间稳定,此酶为单亚基蛋白,凝胶过滤法测得分子量为42000,含糖14.6％,SDS、Hg2+、Ag+、Fe3+对酶有强烈的抑制作用,金属螫合剂EDTA对酶活无影响。此酶对甲基对硫磷、敌敌畏、亚胺硫磷也有较好的降解作用,当以对硫磷为底物时,Km为0.43mmol／L,Vmax为1.24μmol·mg-1·min-1。     

以Fe(III) 改性胶原纤维为载体固定过氧化氢酶

将胶原纤维用三价铁改性后作为载体,通过戊二醛的交联作用将过氧化氢酶固定在该载体上。制备的固定化过氧化氢酶蛋白固载量为16.7 mg/g,酶活收率为35％。研究了固定化酶与自由酶的最适pH、最适温度、热稳定性、贮存稳定性及操作稳定性。结果表明：过氧化氢酶经此法固定化后,最适pH及最适温度与自由酶相同,分别为pH 7.0和25 ℃;但固定化酶的热稳定性显著提高,在75 ℃保存5 h后,仍能保留30％的活力,而自由酶则完全失活;固定化酶在室温下保存12 d后,酶活力仍保持在88％以上,而自由酶在此条件下则完全失     

外来入侵植物空心莲子草几丁质酶特性研究

外来入侵植物空心莲子草因其强抗逆性而迅速蔓延,成为有害杂草.拟研究其病程相关蛋白--几丁质酶酶学性质,为探讨该植物的抗逆机理和入侵机制提供理论依据.空心莲子草经乙烯利处理后,其叶片蛋白质提取液在4℃经40～60%饱和硫酸铵溶液沉淀,SephadexG-75洗脱后得几丁质酶液.结果表明:空心莲子草几丁质酶最适反应pH为5.7左右,在pH4.0～8.0均表现稳定,当pH小于4.0和大于8.0时酶活力丧失50%以上,在pH2.0和10.0时没有活力;在30℃-80℃范围内,酶均具较高活性,最适反应温度为70℃左右,温度高于80℃后,酶稳定性下降;当底物浓度小于1.25%时,酶活力随底物浓度的增加而增加,在底物浓度大于1.25%浓度时,活力增加的趋势减缓.结果提示:也许空心莲子草的强抗逆性是因为其几丁质酶具较高的温度耐受性和较大的pH作用范围.     

以Fe(Ⅲ)改性胶原纤维为载体固定过氧化氢酶

将胶原纤维用三价铁改性后作为载体,通过戊二醛的交联作用将过氧化氢酶固定在该载体上.制备的固定化过氧化氢酶蛋白固载量为16.7 mg/g,酶活收率为35％.研究了固定化酶与自由酶的最适pH、最适温度、热稳定性、贮存稳定性及操作稳定性.结果表明:过氧化氢酶经此法固定化后,最适pH及最适温度与自由酶相同,分别为pH 7.0和25℃;但固定化酶的热稳定性显著提高,在75℃保存5 h后,仍能保留30％的活力,而自由酶则完全失活;固定化酶在室温下保存12 d后,酶活力仍保持在88％以上,而自由酶在此条件下则完全失活;此外,固定化过氧化氢酶还表现出了良好的操作稳定性,在室温下连续反应26次后,相对活力为57％.该研究表明胶原纤维可作为固定化过氧化     

谷胱甘肽硫转移酶(GST)的固定化及酶学特性研究

对谷胱甘肽硫转移酶的固定化、游离酶和固定化酶的酶学特性进行了研究,通过试验,确定谷胱甘肽硫转移酶的最佳固定化条件为先用2％壳聚糖吸附酶,然后再加戊二醛交联,交联用戊二醛浓度为1．2％,交联时间6h;游离酶的最适温度为45—55℃,最适pH值为6．5-7．0：固定化酶的最适温度为45-50℃,最适pH值为7．0;游离酶和固定化酶的最适酶促反应时间为30min。     

特异腐质霉纤维素酶的研究

由腐植土中分离到一株嗜热真菌,经鉴定为特异腐质霉(Humicola insolens Cooney etEmerson)。研究了这株菌纤维素酶的产生条件和一般性质。菌在含麦麸5％、NaNO0.3％的液体培养基(灭菌前pH7.5,灭菌后pH7.2)中,于45℃培养4天,以羧甲基纤维素钠为底物,每ml滤液酶活力为20个单位。酶作用的最适条件为:pH6.0,温度为65—70℃。该纤维素酶是一种耐热酶,热稳定性较强,70℃保温5分钟后,酶活力剩余88％。底物对该酶的热钝化有较强的保护作用,无底物存在条件下,70℃保温6小时后,酶活力仅剩余1％,而在同样的处理温度和时间,在有底物存在条件下,酶活力可剩余30％。该酶在45℃保温15小时的条件下,pH稳定范围为6.0—9.0。     

马特链霉菌7-木糖紫杉烷糖基水解酶初步研究

酶法转化7-木糖紫杉烷(7-XDT)为10-脱乙酰基紫杉醇(10-DAT)是目前合成紫杉醇的最主要途径.本研究分离到一株具有产生7-木糖紫杉烷(7-XDT)糖基水解酶能力的马特链霉菌(Streptomyces matensi YUCM 410051),通过酶的最适反应温度、硫酸铵分级沉淀、最适反应pH和酶的有机试剂耐受等研究,发现最适反应温度为25～30℃,硫酸铵分级沉淀酶活在20％～70％的盐浓度时活性最高;粗酶液最适反应pH在6.0～7.5,酶的甲醇耐受浓度和DMSO耐受浓度均为10％.深入研究该酶对开发具有水解7-木糖紫杉烷(7-XDT)中木糖基的酶资源和提高红豆杉中的紫杉烷类化合物的利用率具有重要价值.     

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.