棕色固氮菌缺失nifZ基因的突变种固氮酶MoFe蛋白的纯化和性质

采用 52℃下加热 6 min,后经 DEAE- 52、Sephacryls S- 2 0 0和 Q- Sepharose等柱层析方法 ,分离纯化了棕色固氮菌 (Azotobacter vinelandii)缺失 nif Z基因突变种固氮酶 Mo Fe(Δnif Z Mo Fe)蛋白 ,其纯度达到电泳纯。Δnif Z Mo Fe蛋白的固氮活性为 2 83nmol C2 H2 还原 / (min·mg蛋白 ) ,远低于野生种 Mo Fe蛋白。Δnif Z Mo Fe蛋白对氧更敏感 ;热稳定性略低于野生种。Δnif Z Mo Fe蛋白的可见光吸收光谱与野生种 Mo Fe蛋白极为相似。其圆二色谱和磁圆二色谱在 450～ 550 nm与野生种 Mo Fe蛋白显著不同 ,表明其 P- cluster及其周围环境与野生种 Mo Fe蛋白有所差异。这亦可能是造成缺失 nif Z突变种 Mo Fe蛋白固氮活性低的原因。     

Interactions between the ankyrin repeat-containing protein Akr1p and the pheromone response pathway in Saccharomyces cerevisiae.

Akr1p, which contains six ankyrin repeats, was identified during a screen for mutations that displayed synthetic lethality with a mutant allele of the bud emergence gene BEM1. Cells from which AKR1 had been deleted were alive but misshapen at 30 degrees C and inviable at 37 degrees C. During a screen for mutants that required one or more copies of wild-type AKR1 for survival at 30 degrees C, we isolated mutations in GPA1, which encodes the G alpha subunit of the pheromone receptor-coupled G protein. (The active subunit of this G protein is G beta gamma, and G alpha plays an inhibitory role in G beta gamma-mediated signal transduction.) AKR1 could serve as a multicopy suppressor of the lethality caused by either loss of GPA1 or overexpression of STE4, which encodes the G beta subunit of this G protein, suggesting that pheromone signaling is inhibited by overexpression of Akr1p. Mutations in AKR1 displayed synthetic lethality with a weak allele of GPA1 and led to increased expression of the pheromone-inducible gene FUS1, suggesting that Akr1p normally (and not just when overexpressed) inhibits signaling. In contrast, deletion of BEM1 resulted in decreased expression of FUS1, suggesting that Bem1p normally facilitates pheromone signaling. During a screen for proteins that displayed two-hybrid interactions with Akr1p, we identified Ste4p, raising the possibility that an interaction between Akr1p and Ste4p contributes to proper regulation of the pheromone response pathway.     

包囊游仆虫皮层和营养核的超微结构研究

为研究纤毛虫在不同生理条件下结构的分化及其调节机理,本文应用透射电镜术显示,营养期包囊游仆虫背、腹面皮层表膜下含３种方式排列组成的纵微管层以及深部微管;口区皮层内含高电子密度的杆状小体;口围带小腹基部含电子致密带和小腹托架,棘毛基体基部及基体下微管束形成围棘纤维篮;背纤毛基体下方也含微管结构;大核染色质附着在核膜上,核膜其他区域有规则排列的核孔。     

细小病毒非结构蛋白转基因小鼠模型建立

将小鼠乳腺癌病毒启动子控制的细小病毒非结构蛋白基因(长5.7kb)氯化铯超速离心,纯化透析后用显微注射法导入C57BL/SJL F_1小鼠受精卵雄核,植入假孕母鼠输卵管,得成活小鼠15只。抽取鼠尾DNA,对其中10只小鼠作PCR和southern blot鉴定,其中4只(40％)整合有目的基因。对首建者B_6()的8只子代小鼠鉴定,3只(37.5％)整合有目的基因。说明导入的目的基因能传代。     

Two Chains of Rhamnogalacturonan II Are Cross-Linked by Borate-Diol Ester Bonds in Higher Plant Cell Walls

Polysaccharide moiety of the boron-polysaccharide complex (T. Matoh, K. Ishigaki, K. Ohno, J. Azuma [1993] Plant Cell Physiol 34: 639-642) isolated from radish (Raphanus sativus) roots has been shown to be rhamnogalacturonan II by glycosyl-linkage analysis and the presence of diagnostic monosaccharides, including apiose, aceric acid, 2-O-methylfucose, and 3-deoxy-D-manno-2-octulosonic acid. Removal of boron from the complex reduced the molecular weight by one-half without causing a significant increase in the number of reducing end groups, indicating that boron, as boric acid, links two rhamnogalacturonan II chains together to form the boron-polysaccharide complex.     

Organization of telomeric and subtelomeric chromatin in the higher plant Nicotiana tabacum

We have examined the structure and chromatin organization of telomeres in Nicotiana tabacum. In tobacco the blocks of simple telomeric repeats (TTTAGGG)_n are many times larger than in other plants, e.g., Arabidopsis thatiana or tomato. They are resolved as multiple fragments 60–160 kb in size (in most cases 90–130 kb) on pulsed-field gel electrophoresis (PFGE) of restriction endonuclease-digested DNA. The major subtelomeric repeat of the HRS60 family forms large homogeneous blocks of a basic 180 by motif having comparable lengths. Micrococcal nuclease (MNase) cleaves tobacco telomeric chromatin into subunits with a short repeat length of 157±5 bp; the subtelomeric heterochromatin characterized by tandemly repeated sequences of the HRS60 family is cut by MNase with a 180 by periodicity. The monomeric and dimeric particles of telomeric and subtelomeric chromatin differ in sensitivity to MNase treatment: the telomeric particles are readily digested, producing ladders with a periodicity of 7 bp, while the subtelomeric particles appear to be rather resistant to intranucleosomal cleavage. The results presented show apparent similarities in the organization of telomeric chromatin in higher plants and mammals.     

应用流式细胞仪研究抗IL-8单抗对IL-8激活人颗粒细胞活力的中和作用(英文)

以IL-8免疫的BALB/C小鼠脾细胞与Sp2/0或653小鼠骨髓瘤细胞融合构建了淋巴细胞杂交瘤克隆I8-S2和I8-63。ELISA叠加试验(ELISA Additivity Test)表明这两杂交瘤克隆分泌的单抗分别识别IL-8分子的不同表位。IL-8能激活人颗粒细胞,引起细胞内Ca~(2 )浓度([Ca~(2 )]_i)上升。通过流式细胞仪分析[Ca~(2 )]_i的变化,发现两个克隆单抗对IL8激活细胞的活力具有不同的中和作用。克隆I8-S2具有很强的中和作用,而克隆18-63则不然。上述结果提示IL-8的激活细胞活力局限于该分子的某表位。