白细胞介素—2分子α螺旋B中的活性相关区域

根据人白细胞介素－２（ＩＬ－２）α螺旋Ｂ中氨基酸残基的空间分布选择性地突变了一些氨基酸残基,结果发现：５７Ｇｌｎ→Ｇｌｕ,６２Ｇｌｕ→Ｌｅｕ,６２Ｇｌｕ→Ａｒｇ和６５Ｐｒｏ→Ａｒｇ这些替换均使ＩＬ－２活性显著降低或丧失,而６３Ｌｅｕ→Ｓｅｒ或６４Ｌｙｓ→Ａｌａ对ＩＬ－２活性影响不大。从受体竞争抑制结合实验结果可知,上述不表现活性的突变体也同时丧夫了与高亲和力受体的结合能力,这说明α螺旋Ｂ中这些位点     

IL—2部分拮抗剂可用于IL—2突变体对受体亚基结合能…

用定点突变法分别得到了两个人白细胞介素－２（ＩＬ－２）的部分拮抗剂１５Ｖａｌ－ＩＬ－２和１２６Ａｓｐ－ＩＬ－２以及一个为ＩＬ－２受体ａ亚基结合缺陷型的突变体６２Ｌｅｕ－ＩＬ－２,当将１５Ｖａｌ－ＩＬ－２或１２６Ａｓｐ－ＩＬ－２与６２Ｌｅｕ－Ｉｌ－２共同保温时,６２Ｌｅｕ－ＩＬ－２的活性受到明显抑制,对此现象机理的分析表明１５Ｖａｌ－ＩＬ－２或１２６Ａｓｐ－ＩＬ－２可用于ＩＬ－２受体亚基结合缺陷型突     

人白细胞介素－2第20位残基局部空间结构稳定位对活性的影响

用寡核苷酸诱导的基因定位突变法,将人白细胞介素－２（ＩＬ－２）第２０位Ａｓｐ分别突变为Ａｒｇ、Ｌｙｓ．和Ａｓｎ,比较第２０位残基碱性基因对ＩＬ－２活力的影响,结果２０Ａｓｐ突变为碱性残基时,ＩＬ－２活性急剧下降,但突变为Ａｒｇ时所导致的活性下降较突变为Ｌｙｓ严重３０００倍以上,从空间结构变化上对这２个碱性残基造成的如此大的活性差异进行了分析,发现２０Ａｒｇ突变后对。１２１Ｔｒｐ的微环境有极为显著的影响。结果提示２０Ａｓｐ在与β亚基作用的同时,其局部空间结构的稳定对维持ＩＬ－２的生物学活性也有重要作用。     

白细胞介素－2中某些残基替换对活性的影响

用基因定点突变法研究了白细胞介素－２（ＩＬ－２）中某些氨基酸对生物活性的影响。将ＩＬ－２中３９Ｍｅｔ和４３Ｌｙｓ分别改为Ｐｒｏ,企图破坏此处α螺旋,突变体的ＣＤ图谱和生物活性均,不变,说明此处可能原来就不存在α螺旋．而将５２Ｇｌｕ．５３Ｌｅｕ,５４Ｌｙｓ分别改为Ｐｒｏ后,ＣＤ谱发生了变化,生物活性也显著下降。表明这些氨基酸处在α螺旋中,将它们改为Ｐｒｏ后,影响了ＩＬ－２的结构,并导致活性下降     

α－苦瓜子蛋白晶体结构中的次级相互作用的研究──Ⅰ结构中氢键相互作用的分析

α－苦瓜子蛋白是一种单链核糖体失活蛋白,具有Ｎ－糖苷酶活性,２．０Ａ分辨率的三维结构已经测定。α－苦瓜子蛋白中总共有３５３个氢键,其中主链原子间氢键１６５个,主链原子与侧链原子间氢键５４个,侧链原子间氢键２１个,蛋白分子中原子与溶水剂的氢键１１３个,主链Ｃ＝Ｏ,主链ＮＨ及侧链分子结构中有９５％的残基能生成氢键,Ａｓｐ．Ｇｌｕ、Ａｓｎ、Ｇｌｎ具有较强的生成多个氢键的能力,并对１３个没有任何氢键的残基作了分析。Ａｎ、Ｌｅｕ、Ｉｌｅ、ＧｌＵ、Ｇｌｎ在α螺旋中出现税率较大,Ｖａｌ、Ｌｅｕ、Ｔｙｒ、Ｉｌｅ、Ｔｈｒ在β结构中占了一半以上,Ａｒｇ容易形成远程的氢键,而Ｓｅｒ、Ｔｈｒ则容易形成近程氢键。某些氢键,特别是保守残基间的氢键,对形成蛋白分子局部特征构象和活性部位的特征构象有影响,α－苦瓜子蛋白的特定折叠方式对其与溶剂水分子成氢键有影响。     

α－苦瓜子蛋白晶体结构中的次级相互作用的研究──Ⅰ结构中氢键相互作用的分析

α－苦瓜子蛋白是一种单链核糖体失活蛋白,具有Ｎ－糖苷酶活性,２．０Ａ分辨率的三维结构已经测定。α－苦瓜子蛋白中总共有３５３个氢键,其中主链原子间氢键１６５个,主链原子与侧链原子间氢键５４个,侧链原子间氢键２１个,蛋白分子中原子与溶水剂的氢键１１３个,主链Ｃ＝Ｏ,主链ＮＨ及侧链分子结构中有９５％的残基能生成氢键,Ａｓｐ．Ｇｌｕ、Ａｓｎ、Ｇｌｎ具有较强的生成多个氢键的能力,并对１３个没有任何氢键的残基作了分析。Ａｎ、Ｌｅｕ、Ｉｌｅ、ＧｌＵ、Ｇｌｎ在α螺旋中出现税率较大,Ｖａｌ、Ｌｅｕ、Ｔｙｒ、Ｉｌｅ、Ｔｈｒ在β结构中占了一半以上,Ａｒｇ容易形成远程的氢键,而Ｓｅｒ、Ｔｈｒ则容易形成近程氢键。某些氢键,特别是保守残基间的氢键,对形成蛋白分子局部特征构象和活性部位的特征构象有影响,α－苦瓜子蛋白的特定折叠方式对其与溶剂水分子成氢键有影响。     

白细胞介素—2中枢镇痛作用途径的作用

抗ＩＬ－２受体α亚基的单克隆抗体不能阻断ＩＬ－２的中枢镇痛作用,以及丧失与ＩＬ－２受体β亚基结合能力的ＩＬ－２突变体仍具有提高大鼠阈的能力,这表明ＩＬ－２的中枢镇痛作用并不是通过ＩＬ－２受体所介导,亦表示ＩＬ－２的免疫和镇痛作用是通过不同的受体途径实现的。     

神经活性甾体与GABAA受体

中枢内存在的神经活性甾体能快速改变神经元兴奋性,它们不是与甾体受体发生作用,而是与脑内主要的抑制性神经递质γ－氨基丁酸（ＧＡＢＡ）受体相互作用,调制基介导的突触抑制功能,引发中枢抑制或兴奋性效应的变化,大多数甾体能增强ＧＡＢＡ受体活化ＣＩ＾－通道的通透性,引发中枢抑制或兴奋性效应的变化。该效应与特定的ＧＡＢＡＡ受体亚基α３和γ２有关,有些甾体具与ＧＡＢＡＡ受体拮抗剂类似的惊厥效应,总之,神经活性甾     

重组人蛋白激酶CK2β亚基cDNA的克隆与测序

蛋白激酶ＣＫ２是一种存在的信使非依赖性丝／苏氨酸蛋白激酶．它是由两个催化亚基（α或α′）和两个调节亚基（β）组成的不均一四聚体．用反转录ＰＣＲ从ＨＬ－６０细胞中获得了人蛋白激酶ＣＫ２β亚基编码区ｃＤＮＡ,将ＮｄｅⅠ／ＨｉｎｄⅢ双酶切ＰＣＲ产物连接到表达载体ｐＴ７－７的ＮｄｅⅠ／ＨｉｎｄⅢ双酶切位点中．转化感受态细菌ＤＨ５α获得转化子,阳性筛选率为７２％．限制性酶切分析结果表明,插入片段和重组质粒的大小与理论推测值相符．随机挑选４个阳性质粒测定其插入片段ＤＮＡ序列,结果显示有２个含有正确插入的人蛋白激酶ＣＫ２βｃＤＮＡ,命名为ｐＴＣＫＢ．其余２个克隆分别存在１个和２个点突变,即在其编码区ｃｏｎｄｏｎ１４８的ＴＣＡ→ＴＴＡ,结果Ｓｅｒ→Ｌｅｕ;另一个则在Ｃｏｎｄｏｎ１４３ＧＴＧ→ＡＴＧ,Ｖａｌ→Ｍｅｔ;Ｃｏｎｄｏｎ１７０ＧＴＧ→ＧＣＧ,Ｖａｌ→Ａｌａ．重组质粒（ｐＴＣＫＢ）克隆的成功,将为在原核细胞中表达蛋白激酶ＣＫ２β亚基以及利用ＣＫ２βｃＤＮＡ作为探针进行深入研究打下基础．并为利用ｐＴ７－７表达载体构建其他重组质粒建立了一套成功的方法     

人白细胞介素—2第20位残基局部空间结构稳定性对活性的影响

用寡核苷酸诱导的基因定位突变法,将人白细胞介素－２（ＩＬ－２）第２０位Ａｓｐ分别突变为Ａｒｇ,Ｌｙｓ和Ａｓｎ,比较第２０位残基碱性基团对ＩＬ－２活力的影响,结果＾２０Ａｓｐ突变为碱性残基时,ＩＬ－２活性急剧下降,但突变为Ａｒｇ时所导致的活性下降较突变为Ｌｙｓ时所导致的活性下降较突变为Ｌｙｓ严重３０００倍以上。从空间结构变化上对这２个碱性残基造成的如此大的活性差异进行了分析,发现＾２０Ａｒｇ突变后对     

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.