粪肠球菌精氨酸脱亚胺酶酶学性质研究

经硫酸铵分级沉淀、Q-Sepharose Fast Flow阴离子交换层析、SephadexG-75凝胶柱层析从NJ402自溶细胞超声破碎液中提纯得到精氨酸脱亚胺酶(ADI),纯化倍数为34.5,活力回收率为31.4%,经SDS-PAGE以及Native-PAGE测定结果表明,ADI亚基分子量约为46 kD,该酶非变性情况下的分子量约为190 kD左右,该酶为同四聚体结构.酶学,胜质研究结果表明:ADI催化最适温度和最适pH分别为50℃和6.5,在45℃以下和pH 5～8之间有很好的稳定性.ADI是L-型脱亚胺酶,具有严格的光学选择性,适当浓度的Mn2 、Mg2 、Co2 对ADI催化活力的促进作用较大,高浓度的Zn2 和Co2 对酶有一定程度的抑制作用,L-瓜氨酸对酶无抑制作用而L-鸟氨酸却表现出较强的抑制作用.ADI在最佳催化条件下作用于L-精氨酸的米氏常数为3.2686 mmol/L,最大反应速度为2.44 μmol/min.     

木霉GXC产β-葡聚糖酶条件和酶学性质

研究了木霉GXC产β-葡聚糖酶的条件.结果表明,最适产酶碳源为麸皮,氮源为硫酸铵;产酶的最适条件为初始pH为4.0～5.0,30℃培养44h.粗酶液经硫酸铵沉淀、Sephadex G-25、Sephadex G-100和DEAE-Sehadex A-50柱层析得到纯β-葡聚糖酶,SDS-PAGE凝胶电泳显示一条带,测得分子量为35kD.该酶最适反应pH5.0,最适反应温度为60℃,在40℃以下、pH4.0～5.0酶活力相对稳定.5.0mmol/L以下的Ca2+、Zn2+和Fe2+,以及10.0mmol/L以下的Co2+对酶活力有激活作用;而Cu2+和Fe3+具有抑制作用.     

重组钝齿棒杆菌全细胞转化生产L-瓜氨酸条件优化

实现了精氨酸脱亚胺酶(ADI)首次在钝齿棒杆菌Corynebacterium crenatum SYPA 5-5中的高效表达。通过Ni-NTA亲和层析纯化得到纯化ADI,经SDS-PAGE测定其分子量约为46.8 k Da,酶学性质研究发现ADI的最适催化温度为37℃,最适pH为6.5,ADI在最佳催化条件下作用于L-精氨酸的米氏常数为12.18 mmol/L,最大反应速率为0.36μmol/(min·mL)。优化了重组菌全细胞转化产L-瓜氨酸的工艺条件,在最优条件下可一次转化300 g/L L-精氨酸,转化速率达8 g/(L·h)。进行重组菌5 L罐发酵并进行罐上全细胞转化300 g/L L-精氨酸,一批菌体可进行多次转化,累计产量达1 900 g以上。     

豇豆几丁质酶部分酶学特性的研究

该文测定了纯化的豇豆几丁质酶部分酶学特性。结果表明,该酶在pH5-8,温度低于60℃的范围内稳定性较好,酶活力最适pH为65,最适温度为50℃。10mmol/L浓度的Hg2 、Mn2 、Mg2 、Co2 等金属离子对酶活力有一定抑制作用,其中Hg2 离子抑制率最高(6883%)。Km(胶状几丁质)值为1662mg/ml;以SDS-PAGE电泳和SephadexG-100柱层析两种方法分别测得分子量为34kD、325kD;IEF电泳测得等电点为83。     

鲫鱼酸性磷酸酶酶学特性及不同效应物对酶活力的影响

经NaAc-HAc缓冲液(pH5.0)抽提,正丁醇处理,硫酸铵分级沉淀,DEAE-32离子交换层析,SephadexG-150凝胶过滤纯化,从鲫鱼内脏中分离纯化出电泳纯的酸性磷酸酶。该酶提纯倍数为30.82,比活力195.06U/mg。研究表明,该酶催化对硝基苯磷酸二钠水解反应,最适pH4.8,pH小于4和大于7时不稳定;最适温度45℃,温度高于50℃不稳定;米氏常数为0.23mmol/L,利用SDS-PAGE测定酶亚基分子量为33.3kD。化学修饰剂SUAN、PMSF、DTT、NBS对该酶活力影响不大,BrAc和IAc有明显抑制作用。金属离子对该酶催化活力有不同影响,Na+、K+、Ni2+、Co2+影响不显著,Mg2+、Ca2+、Ba2+、Mn2+有激活作用,Ag+、Cu2+、Pb2+、Cd2+有抑制作用,其中Mg2+、Ca2+、Pb2+、Cd2+对鲫鱼酸性磷酸酶荧光光谱的影响表明金属离子对酶活力的影响与酶构象改变有关。       

黑木耳漆酶纯化及部分漆酶特性的研究

黑木耳漆酶研究可为漆酶的进一步分离纯化、基因克隆表达和大规模生产应用奠定基础。对黑木耳"黑29"菌株漆酶粗酶液进行硫酸铵分级沉淀后,通过Native SDS-PAGE电泳检测,存在3种漆酶LacA、LacB、LacC,分子量分别为60,34,19 kD。经硫酸铵分级沉淀和DEAE-Sephacel柱层析技术分离得一纯化成分LacC,纯化倍数7.60,酶活性回收4.28%。对LacC的pH、温度、金属离子和Km值等部分酶学性质进行研究发现,该酶氧化ABTS的Km值为1.18×10-6mol/L,催化氧化底物ABTS的最适pH为3.8,在pH 3.0~4.6表现出较强的稳定性;最适反应温度为55℃,低于50℃时有较好的热稳定性;金属离子Ag+对漆酶有激活作用,而Fe3+、Mn2+、Co2+则有抑制作用。     

酸性α-淀粉酶的分离纯化与酶学性质研究

纯化了枯草芽胞杆菌xm-1菌株酸性α-淀粉酶,并对其酶学性质进行了研究。通过硫酸铵沉淀和Sephadex G-75凝胶层析将酸性α-淀粉酶粗酶液纯化了32.5倍,活力回收率为10.0%。酶性质测定结果表明,该酸性α-淀粉酶分子量约为60kD,最适反应温度为45℃、最适作用pH5.0,该酶在pH3.4-6.0下稳定,高温耐受性差。Cu2+、Zn2+、EDTA对酶有不同程度的抑制作用,Ca2+和Mn2+对酶具有较强的激活作用。     

木霉GXC产β—葡聚糖条件和酶学性质

研究了木霉GXC产β－葡聚糖糖的条件,结果表明,最适产酶碳源的麸皮,氮源为硫酸铵,产酶的最适条件为,初始pH为4.0-5.0,30℃培养44h,粗酶液经硫酸铵沉淀,SephadexG-25,Sephadx G-100和DEAE－Sephadex A-50柱层析得到纯β－葡聚糖酶,SDS－PAGE凝胶电泳显示－条带,测得分子量为35kD,该酶最适反应pH5.0,最适反应温度为60℃,在40℃以下,pH4.0-5.0酶活力相对稳定,5.0mmol/L以下的Ca^2 ,Zn^2 和Fe2 ,以及10.0mmol/L以下的Co^2 对酶活力有激活作用,而Cu^2 和Fe^ 具有抑制作用。     

绿色糖单孢菌-木素过氧化物酶的纯化及酶学性质研究

实验以一株耐热耐碱放线菌--绿色糖单孢菌(Saccharomonospora viridis)为研究对象,从其液体发酵产物中提取木素过氧化物酶(Lignin Peroxidases / LiP),粗酶液经硫酸铵分级沉淀、透析浓缩,最后经过Sephadex G-75柱色谱得到单一的LiP,酶纯度提高了11.06 倍;经SDS-聚丙烯酰胺凝胶电泳测定该酶的分子量约为28.8kD.同时对纯酶的酶学性质进行了初步研究,发现LiP 酶的最适反应温度为50℃,最适反应为7.0 ;在75℃下具有良好的热稳定性,在pH7 ～ 10 范围内有较强的耐受力,保温30min 时酶的半衰期温度为75℃ ;该酶在高温、偏碱性的造纸工业中具有一定应用潜力.金属离子Cu2+、Fe2+、Co2+ 对酶具有明显促进作用,Ca2+、SDS 具有抑制作用;糖含量测定发现该酶为小分子量的糖基化蛋白,含有6.59% 的糖;酶动力学反应测定发现该酶对底物2,4-二氯苯酚(2,4-DCP)的Km 值为0.1057mmol/L.     

重组磷脂酰丝氨酸合成酶的分离纯化及酶学性质研究

利对重组枯草芽孢杆菌(pBES-pss)表达的磷脂酰丝氨酸合成酶进行分离纯化及酶学性质研究.pBES-pss发酵后的粗酶液经硫酸铵盐析、中空纤维膜除盐浓缩、SP-Sepharose HP离子交换层析和Sephadex G-75凝胶层析,基本获得电泳纯的重组磷脂酰丝氨酸合成酶,比活力可达13.62 U/mg,分子量约为53 kD.酶学性质研究表明,该酶催化卵磷脂水解反应的最适pH8.0,最适温度为35℃.稳定性研究表明:该酶在pH 6.5～9.5 区间和低于45℃温度下稳定.表面活性剂及金属离子对该酶水解活性的影响结果表明,SDS、Tween20、Tween80对该酶有抑制作用,Triton X-100对该酶有增强作用;Mg2+、Zn2+、K+对该酶有抑制作用,Ca2+、Mn2+和EDTA对该酶有增强作用.     

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.