坚强芽孢杆菌β-淀粉酶基因的核苷酸序列分析

淀粉水解酶广泛用于淀粉加工业中,何秉旺等在选育产耐热β-淀粉酶菌株中得到一株坚强芽孢杆菌（Bacillusfirmus）725,该菌株产生的淀粉酶有较好的热稳定性,水解淀粉的主要产物为麦芽糖。自然菌株产生的淀粉酶往往是多种淀粉酶的混合,为进一步研究该菌株产生的淀粉酶的性质和在工业上应用的可能性,分离了三个淀粉酶基因,在大肠杆菌中克隆和表达[1]。其中重组质粒pBA150产生的淀粉酶的淀粉水解产物主要是麦芽糖［1］。β-淀粉酶（EC.3．2.1．2）水解淀粉的主要产物是麦芽糖,工业上可用于生产高麦芽糖浆,近年来又有β-淀粉酶用于啤酒工业的报道[2]。本文报道重组质粒pBA150的β-淀粉酶基因的序列分析及推导出的氨基酸序列同己知β-淀粉酶的氨基酸序列比较。     

坚强芽孢杆菌β-淀粉酶基因的核苷酸序列分析

淀粉水解酶广泛用于淀粉加工业中,何秉旺等在选育产耐热β-淀粉酶菌株中得到一株坚强芽孢杆菌（Bacillusfirmus）725,该菌株产生的淀粉酶有较好的热稳定性,水解淀粉的主要产物为麦芽糖。自然菌株产生的淀粉酶往往是多种淀粉酶的混合,为进一步研究该菌株产生的淀粉酶的性质和在工业上应用的可能性,分离了三个淀粉酶基因,在大肠杆菌中克隆和表达[1]。其中重组质粒pBA150产生的淀粉酶的淀粉水解产物主要是麦芽糖［1］。Β-淀粉酶（EC.3．2.1．2）水解淀粉的主要产物是麦芽糖,工业上可用于生产高麦芽糖浆,近年来又有β-淀粉酶用于啤酒工业的报道[2]。本文报道重组质粒pBA150的β-淀粉酶基因的序列分析及推导出的氨基酸序列同己知β-淀粉酶的氨基酸序列比较。     

嗜碱菌碱性淀粉酶的研究

分离自内蒙古自治区察汗淖碱湖的嗜碱菌株No．1 0-1,好气,运动,细胞杆状,革兰氏染色阴性。该菌生长pH范围为8．0—13．0,最适生长pH1 0.0-ll.0,为专性嗜碱菌。在含淀粉培养基中产生胞外碱性淀粉酶,最适产酶条件是： 碳源为土豆淀粉,氮源为复合蛋白胨,Nacl浓度为2．O％,Na2CO3浓度为1．0—1．5％(pH9．9-10．5)。 酶的最适反应pH为10．0,稳定pH8．0,最适反应温度为50℃。作用于直链淀粉其水解产物为β-构型,主要产物是麦芽糖,其次为麦芽三糖、葡萄糖和麦芽四糖。嗜碱菌No.10-1产生的酶为碱性β-淀粉酶。     

巨大芽孢杆菌β-淀粉酶基因的克隆、表达和酶学性质分析

从巨大芽孢杆(Bacillus megaterium)的全基因组DNA文库中筛选出一个β-淀粉酶基因amyG,分析测定了其核苷酸序列并进行了诱导表达;其中amyG编码的蛋白有545个氨基酸、分子量为60.194 kD,与已报道的巨大芽孢杆菌DSM319的β-淀粉酶序列有着94.5%的同源性.经氨基酸序列比较分析发现,AmyG从N末端到C末端依次由信号肽域、糖基水解酶催化功能域和淀粉结合域3个功能域组成.其中催化功能域里含有第14家族糖基水解酶常见的几个高度保守的酶催化活性区.经多步纯化,重组酶的比活共提高了7.4倍,获得凝胶电泳均一的蛋白样品;经SDS-PAGE电泳测定,酶AmyG的分子量为57 kD.该酶的最适反应温度为60℃,最适反应pH为7.0;在温度不超过60℃时,酶活较稳定:AmyG能迅速降解淀粉生成麦芽糖,属于外切β-糖苷酶.     

嗜热真菌 Thermomyces lanuginosus热稳定a—淀粉酶的纯化及特性

嗜热真菌Thermomyces lanuginosus在液体培养基中于50℃静止培养14d,培养液经硫酸铵分级沉淀、DEAE-Toyopearl离子交换层析、Butyl-Toyopearl疏水层析、SephacrylS-300分子筛层析和FPLC MonoQ离子交换层析,得到了凝胶电泳均一的淀粉酶。纯酶与淀粉反应不同时间后,用碘色反应法和DNS法测定淀粉和还原糖量,结果显示淀粉量在开始时迅速下降,但还原糖的量却增加很慢;产物经TLC层析分析为麦芽糖和少量葡萄糖。由此说明它为α-淀粉酶。用SDS-PAGE和Sephacryl S-300分子筛层析测定分子量为56000,不具亚基。酶反应最适温度和pH分别为65℃和4.5～5.0。在pH4.6条件下,酶在50℃是稳定的;60℃保温1h,仍保留94％的原酶活性;酶在70℃的半衰期为10min。钙离子对酶有激活作用。酶对糖原和糊精有一定的水解能力。     

嗜热真菌 Thermomyces lanuginosus热稳定a—淀粉酶的纯化及特性

嗜热真菌Thermomyces lanuginosus在液体培养基中于50℃静止培养14d,培养液经硫酸铵分级沉淀、DEAE-Toyopearl离子交换层析、Butyl-Toyopearl疏水层析、SephacrylS-300分子筛层析和FPLC MonoQ离子交换层析,得到了凝胶电泳均一的淀粉酶。纯酶与淀粉反应不同时间后,用碘色反应法和DNS法测定淀粉和还原糖量,结果显示淀粉量在开始时迅速下降,但还原糖的量却增加很慢;产物经TLC层析分析为麦芽糖和少量葡萄糖。由此说明它为α-淀粉酶。用SDS-PAGE和Sephacryl S-300分子筛层析测定分子量为56000,不具亚基。酶反应最适温度和pH分别为65℃和4.5～5.0。在pH4.6条件下,酶在50℃是稳定的;60℃保温1h,仍保留94％的原酶活性;酶在70℃的半衰期为10min。钙离子对酶有激活作用。酶对糖原和糊精有一定的水解能力。     

高温放线菌V4菌株热稳定β-淀粉酶的产生及其性质的研究

高温放线菌V₄菌株(Thermoactinomyces sp.V₄)产生的β－淀粉酶最适反应温度为70℃,最适pH为6,酶的热稳定性良好,50℃(4h)不失去酶活力,55℃(2h)保持最初活力的92％,酶对可溶性淀粉的水解率达77％,纸层析结果显示水解产物主要为麦芽糖,经旋光测定,水解产物具有β－构型。巯基抑制剂对此β－淀粉酶无抑制作用。V₄菌株同时产生异淀粉酶及少量的－菌一淀粉酶。     

嗜盐碱性淀粉酶产生条件和性质的初步研究

从我国内蒙古自治区察汗淖碱湖分离到一株能产胞外嗜盐碱性淀粉酶的极端嗜盐嗜碱杆菌(Natronobacterium sp.)C-212,该菌产酶的最适pH和NaCl浓度分别为9.5和20%,最适碳源为可溶性淀粉,氮源为复合蛋白胨.酶反应最适温度为50℃,pH为8.5,NaCl浓度为2.6mol/L,该酶在pH9.5最稳定,NaCl可增加酶的热稳定性,酶降解可溶性淀粉的主要产物为葡萄糖、麦芽糖、麦芽三糖及其他寡糖.     

巨大芽孢杆菌b-淀粉酶基因的克隆、表达和酶学性质分析

从巨大芽孢杆菌(Bacillus megaterium)的全基因组DNA文库中筛选出一个b-淀粉酶基因amyG, 分析测定了其核苷酸序列并进行了诱导表达; 其中amyG编码的蛋白有545个氨基酸、分子量为60.194 kD, 与已报道的巨大芽孢杆菌DSM319的b-淀粉酶序列有着94.5%的同源性。经氨基酸序列比较分析发现, AmyG从N末端到C末端依次由信号肽域、糖基水解酶催化功能域和淀粉结合域3个功能域组成。其中催化功能域里含有第14家族糖基水解酶常见的几个高度保守的酶催化活性区。经多步纯化, 重组酶的比活共提高了7.4倍, 获得凝胶电泳均一的蛋白样品; 经SDS-PAGE电泳测定, 酶AmyG的分子量为57 kD。该酶的最适反应温度为60oC, 最适反应pH为7.0; 在温度不超过60oC时, 酶活较稳定; AmyG能迅速降解淀粉生成麦芽糖, 属于外切b-糖苷酶。     

微生物酶拆分方法生产D-泛酸的手性中间体D-泛解酸内酯

筛选到一株产D－泛解酸内酯水解酶的串珠镰孢霉菌（Fusarium moniliforme SW-902)。产酶条件研究表明,用甘油作碳源,蛋白胨作氮源,初始pH8.0,温度26℃,摇瓶培养3d,产酶量最高。在60L和1000L发酵罐中通风发酵45－47h,产酶量为6－8g干菌体／L,D－泛解酸内酯水解酶酶活力达到0．87－0．92IU／g干菌体。该酶的最适反应温度为55℃,最适反应pH为7．0－7．5。在酶不对称水解泛解酸内酯过程中,对溶液加酶量5％－10％,底物浓度10％－20％,控制水解率20％－30％,水解效果最好。     

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.