构建一种检测水中As3+的敏感型大肠杆菌

为构建一种敏感性强、特异性好的检测砷离子的大肠杆菌荧光报告菌株,本研究利用基因敲除技术,敲除了大肠杆菌中负责向胞外转运砷离子的ars B基因,构建对As~(3+)敏感的菌株;利用egfp基因作为报告基因,构建融合检测载体p ET28b-Pars-ars R-egfp。然后将检测载体p ET28b-Pars-ars R-egfp转化至ars B基因敲除菌中完成敏感型As~(3+)检测菌株的构建。接着对此微生物传感器进行了检测条件的优化,以及线性检测范围、最低检出限、特异性等性能的确定。研究结果表明,与利用野生大肠杆菌作为检测宿主相比,此敏感型砷检测菌株对检测As~(3+)的灵敏度有显著提高,最适检测As~(3+)浓度范围为0.013-42.71μmol/L,最低检出下限为5.13 nmol/L。因此,本研究利用基因敲除技术对大肠杆菌进行改造,成功地提高了砷检测微生物传感器的灵敏度,为重金属微生物传感器的优化研究工作提供了有用方案。     

TAT介导多肽药物过表达纯化和穿膜活性检测

目的:获得NR2B羧基端多肽(NR2Pep),探讨TAT-NR2Pep在细胞中的跨膜特性。方法:利用酶切连接方法构建p Waldo-TAT-pep质粒,转化大肠杆菌BL21(DE3)感受态细胞,检测不同浓度诱导剂和不同温度对蛋白质表达的影响;利用镍柱亲和层析及分子筛方法纯化TAT-NR2Pep-GFP融合蛋白,利用GFP发荧光的特性采用In-gel检测蛋白质的表达情况;以融合蛋白C端His标签特异性抗体,通过Western印迹确定融合蛋白的表达;荧光显微镜下观察TAT-NR2Pep-GFP融合蛋白在CHO和C2C12等细胞中的跨膜活性。结果:构建了TAT-NR2Pep-GFP表达载体,重组菌经0.1 mmol/L IPTG于22℃诱导20 h能够表达较多高质量的目标蛋白;In-gel荧光检测证实融合蛋白TATNR2Pep-GFP拥有正确构象,GFP能够发出绿色荧光;Western印迹分析表明融合蛋白相对分子质量符合预期;细胞穿膜实验证实TAT能够介导多肽穿过细胞膜。结论:原核表达并纯化得到TAT-NR2Pep-GFP融合蛋白,该蛋白散发绿色荧光,能够穿过细胞膜。     

FGF20原核表达载体构建及在大肠杆菌中优化表达

[目的]构建人FGF20原核表达载体并在大肠杆菌(Escherichia coli,E.coli)中优化表达。[方法]从胃癌细胞中经RT-PCR扩增FGF20基因并构建p ET28b-FGF20载体,转化E.coli,IPTG诱导表达。对诱导OD值、IPTG浓度、诱导温度、时间及溶氧量进行优化,同时采用正交试验优化培养基配方,以SDS-PAGE及Western Blot检测蛋白表达,以确定最佳表达条件。[结果]构建了p ET28b-FGF20原核表达载体,实现了FGF20蛋白的表达,确定最佳表达条件为:培养基占锥形瓶容积20%,菌体生长至OD600=0.4,加入终浓度1.0 mmol/L的IPTG,37℃诱导6 h。培养基最佳成分为:蛋白胨11 g/L、酵母提取物5 g/L、氯化钠10 g/L、葡萄糖0 g/L。[结论]实现了FGF20在大肠杆菌中的优化表达,为其基因工程药物生产及药用研究奠定了基础。     

高粱花叶病毒外壳蛋白的原核表达及其抗血清制备

高粱花叶病毒(Sorghum mosaic virus,SrMV)是世界上分布最广的侵染甘蔗的病毒之一,引起甘蔗花叶病,对甘蔗产业危害很大。根据SrMV外壳蛋白(coat protein,CP)基因序列合成一对引物,以海南(SrMV-HN)染病植株总RNA为材料,采用RT-PCR方法克隆了长约987 bp的目的片段。将CP基因与质粒pET32a(+)连接,构建了含SrMV CP基因的融合蛋白原核表达载体pET32a-SrMVCP。然后用正确的重组质粒转化大肠杆菌Rosetta(DE3),经IPTG诱导后,SDS-PAGE检测出一条约36kD的特异融合蛋白表达谱带。融合蛋白主要以可溶性蛋白形式稳定表达。通过优化诱导条件,确立了CP基因表达的最佳条件:IPTG终浓度为0.1 mmol/L,诱导时间为4 h,诱导温度为30℃。用Ni2+-NTA琼脂糖亲和层析纯化融合蛋白,免疫家兔制备出抗血清。通过酶联法(ID-ELISA)测定本试验制备的SrMV CP抗血清工作浓度为1∶1 000,Western blotting检测结果表明,抗血清与SrMV-HN诱导表达的CP蛋白发生特异性反应。对田间25个甘蔗样品进行检测,结果表明该抗血清的效价高、灵敏度高、特异性强,可以应用于田间样品的检测。     

蓝色和黄色荧光蛋白在灵芝中的表达及黄色荧光蛋白在诱导型启动子Pcbh2活性分析中的应用

本研究中通过密码子优化和内含子添加分别构建了蓝色荧光蛋白基因(bfp)表达载体PJW-EXP-intron-opbfp和黄色荧光蛋白基因(yfp)表达载体PJW-EXP-intron-opyfp,使用灵芝Ganodermalingzhi原生质体进行转化,筛选得到了表达BFP和YFP的工程菌株。工程菌株的菌丝在荧光显微镜下可分别检测到蓝色和黄色荧光信号,而野生型菌株(WT)的菌丝检测不到这2种荧光,结果显示我们在灵芝中实现了蓝色和黄色荧光蛋白的表达。基于本研究建立的荧光蛋白表达方法,我们评估了纤维二糖水解酶Ⅱ基因的启动子(Pcbh2)在微晶纤维素诱导下的活性。将黄色荧光蛋白基因插入到Pcbh2启动子的下游构建yfp-Pcbh2表达载体,经过转化获得了YFP-Pcbh2灵芝工程菌株。在微晶纤维素的诱导下,检测到YFP-Pcbh2菌丝体可发出黄色荧光信号,而不加微晶纤维素诱导时则没有检测到荧光,结果表明Pcbh2启动子在微晶纤维素诱导下具有转录活性。     

革胡子鲶GH成熟肽在大肠杆菌中表达条件的优化

将携带革胡子鲶(Clarias lazera)生长激素(GH)成熟肽cDNA序列的重组表达载体pRSET-mGH转化入大肠杆菌Escherichia.coliBL21(DE3)pLysS中进行融合蛋白的表达。表达条件优化试验表明,表达菌株接种SOB培养基,培养2-3h后可用IPTG进行融合蛋白诱导表达;IPTG最佳诱导浓度为1.5 mmol/L,最佳诱导时间为4 h。本试验构建的原核表达体系为下一步革胡子鲶生长激素促生长制剂的研制奠定了基础。     

美洲大蠊几丁质酶基因的原核表达及蛋白纯化

昆虫几丁质酶是昆虫几丁质代谢不可或缺的关键酶类。本研究旨在构建美洲大蠊几丁质酶Pa Cht1基因原核表达载体,纯化并鉴定Pa Cht1重组蛋白,为后续酶活等测定奠定基础。定向克隆Pa Cht1基因成熟肽序列至原核表达载体pET32a(+)上,将构建成功的pET32a-Cht1重组表达质粒导入大肠埃希菌Rosetta中,分别对诱导剂IPTG浓度和诱导时间进行优化,确定最佳诱导浓度和诱导时间,并对表达产物进行可溶性分析。表达产物经镍离子柱纯化后通过Western Blot鉴定。结果表明,美洲大蠊几丁质酶Pa Cht1成熟肽基因编码区长1 083 bp,编码360个氨基酸。最佳诱导浓度和诱导时间分别为0.2 mmol/L和4 h。所得重组蛋白大小约60 k D,与预期结果大小一致,重组蛋白主要以包涵体的形式存在。Western Blot鉴定重组蛋白可与6×His-tag单克隆抗体特异性结合。说明成功构建了原核表达载体pET32a-Cht1,并诱导表达获得了重组几丁质酶蛋白。     

大肠杆菌细胞裂解系统的构建及其在真菌毒素降解酶表达中的应用

目的:大肠杆菌中分泌表达重组蛋白受限于其分泌效率,为此设计构建大肠杆菌诱导裂解系统以实现胞内重组蛋白的快速高效分泌。方法:利用大肠菌素E7对细胞的裂解能力,构建共表达目标重组蛋白和E7的大肠杆菌细胞裂解系统,使目标重组蛋白在E7表达后得以释放到培养基中。结果:首先以红色荧光蛋白(red fluorescent protein,RFP)为报告基因,在pET28a(+)载体上构建大肠杆菌素E7和红色荧光蛋白两个表达盒,通过对比分析IPTG一步诱导和IPTG-阿拉伯糖分步诱导系统蛋白质的表达效果,发现分步诱导系统能够更高效地表达并释放目标蛋白到培养基。在IPTG-阿拉伯糖分步诱导裂解系统中表达玉米赤霉烯酮降解酶基因,培养基上清液中检测到玉米赤霉烯酮降解酶有较好的表达量和较高的活性,能够在37℃反应30min的条件下降解约5. 8μg玉米赤霉烯酮毒素。结论:利用大肠菌素E7成功构建大肠杆菌细胞裂解系统,并且此系统在快速释放胞内表达外源蛋白方面有适用性。     

镉和铜对嗜热四膜虫金属硫蛋白基因的诱导表达

本文在荧光定量PCR优化的基础上,利用该技术考察了不同浓度的重金属镉和铜对嗜热四膜虫金属硫蛋白基因(MTT1)诱导表达的变化规律。结果表明MTT1基因的表达对镉离子的诱导更灵敏,且在一定阈值浓度(≤35.2μmol/L)范围内,镉离子浓度升高会增加MTT1基因表达量,超过该阈值后表达量迅速下降;镉与铜同时诱导时MTT1基因的表达情况与镉单独诱导的类似,但阈值浓度减小为22μmol/L,表明二者的联合毒性为协同作用。镉离子浓度低于22μmol/L时,与铜离子的共同作用会大大增加MTT1基因的表达量,从而增强了四膜虫的解毒能力。     

可溶性泛素样特异性蛋白酶1的表达及活性鉴定

目的:高效可溶性表达泛素样特异性蛋白酶1(ULP1)。方法:根据大肠杆菌密码子的偏好性优化合成编码ULP1的基因片段序列,将其克隆到原核表达载体p GEX-6P-1中,转化大肠杆菌BL21(DE3),用0.5 mmol/L IPTG于37℃诱导表达8 h,观察重组蛋白ULP1的表达情况;优化诱导时间及IPTG浓度,并鉴定重组蛋白ULP1的生物学活性。结果:重组蛋白ULP1表达的最佳条件为37℃、0.1 mmol/L的IPTG诱导表达5 h,目的蛋白以可溶性表达为主;Western印迹结果表明,重组蛋白ULP1能够被His单克隆抗体识别,重组蛋白ULP1能够特异性酶切SUMO-GFP。结论:表达了具有生物学活性的SUMO蛋白酶ULP1。     

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.