Regularities in the E. coli promoters composition in connection with the DNA strands interaction and promoter activity

INTRODUCTION It is well known that the physical properties, namely DNA strands interaction in promoter are connected with their activity. As it was established the two promoter regions ?35 and ?10 are the most important for the promoter functioning, all bases in the ?35 (TTGACA) and ?10 (TATAAT) hexamers were highly conserved (Harley and Reynolds, 1987; Hawley and McClure, 1983). The functional impor- tance of these sequences was proved in many inves- tigations (Record et al., 199…     

RNAi的革命

通过实验手段向细胞内导入长的双链RNA或者转基因可以产生一些短片段的双链RNA,这些短片段的双链RNA可以通过促使特定基因的mRNA降解来高效、特异地阻断体内特定基因的表达,使细胞出现特定基因缺失的表型,称为RNA干扰(RNA interference,RNAi)。SiRNA(small interference RNA)就是这种短片段双链RNA分子,能够以序列同源互补的mRNA为靶目标,降解特定的mRNA。基本上所有的生物体内也都存在一种内源的小分子RNA,为单链RNA,由基因组转录生成,但是不编码蛋白质,它们的功能在于调节mRNA的翻译,称为miRNA,是由具有发夹结构的前体剪切产生的。RNAi的发现具有划时代的意义,它不仅揭示了细胞内基因沉默的机制,而且有望成为后基因组时代基因功能分析的有力工具,极大地促进了人类揭示生命奥秘的进程。     

Dependence of nucleotide physical properties on their placement in codons and determinative degree

INTRODUCTION It is well-known from the genetic code structure that there exists a connection between codons and physical and chemical amino acid properties (Lewin, 1983). Codon properties in turn are defined by physical properties of the nucleotides from which they are compounded (Ratner, 1985; 2000). The most important properties of nucleotides as complex three-dimensional molecules are their dipole moment, heat of formation and energy of the most stable con- formation (Schneider and Be…     

DNA sequence representation by trianders and determinative degree of nucleotides

INTRODUCTION Genomic DNA sequence analysis using wide range of statistical methods (Torney et al., 1999; Bulmer, 1987; Luo et al., 1998; Nieselt-Struwe, 1997; Fickett et al., 1992; Buldyrev et al., 1998; Azbel, 1995) and various symmetry investigations (Findley et al., 1982; Hornos and Hornos, 1993; Bashford et al., 1997; Bhry et al., 1998; Forger and Sachse, 1998; Frappat et al., 1998) is an extremely important tool for extracting hidden information on the dynamic process of evolu…     

用于表达多肽抗原融合基因的杆状病毒系统

以含翻译起始密码子ATG的质粒pSⅪⅤⅥ Ⅹ3/4为转移载体,将多角体蛋白及切除部分5′和3′端的乙型肝炎核心抗原(HBcAg)基因同时插入粉纹夜蛾核型多角体病毒(TnNPV)基因组中,构建了形成多角体的重组毒株。该毒株能利用合成—多角体ⅪⅤ串联启动子,表达由截短的HBcAg序列及其上下游多接头与杆状病毒DNA部分序列组成的融合蛋白基因。SDS-聚丙烯酰胺凝胶电泳、Wcstern印迹与免疫电镜观察的结果表明,融合蛋白基因表达产物的分子量约20.5KD,与理论计算值相符,并保留了HBcAg的抗原性,亦能形成典型的HBcAg颗粒。组建含多克隆点及截去两端序列的HBcAg基因转移载体质粒,使编码多肽抗原的寡聚核苷酸易于克隆,以HBcAg融合蛋白方式在杆状病毒载体系统中表达,并能形成HBcAg为蛋白载体的抗原颗粒结构。     

解脂耶氏酵母杂合启动子的构建

目的：构建一系列新的用于解脂耶氏酵母的杂合启动子。方法：采用PCR技术将pXPR2的一段上游激活序列(UAS-1B)进行了离体串联重复，得到了一系列拷贝数不同的串联重复体，并将其克隆到了pTEF启动子的上游．结果：通过酶切鉴定，确证得到了含有UAS-1B重复单元数目不等的杂合启动子．结论：本方法实用可行，并构建了一系列杂合启动子，为进一步构建高表达水平的解脂耶氏酵母表达栽体奠定了良好的基础。     

A food-grade industrial arming yeast expressing β-1,3-1,4-glucanase with enhanced thermal stability

The aim of this work was to construct a novel food-grade industrial arming yeast displaying β-1,3-1,4-glucanase and to evaluate the thermal stability of the glucanase for practical application. For this purpose, a bi-directional vector containing galactokinase (GAL1) and phosphoglycerate kinase 1 (PGK1) promoters in different orientations was constructed. The β-1,3-1,4-glucanase gene from Bacillus subtilis was fused to α-agglutinin and expressed under the control of the GAL1 promoter. α-galactosidase induced by the constitutive PGK1 promoter was used as a food-grade selection marker. The feasibility of the α-galactosidase marker was confirmed by the growth of transformants harboring the constructed vector on a medium containing melibiose as a sole carbon source, and by the clear halo around the transformants in Congo-red plates owing to the expression of β-1,3-1,4-glucanase. The analysis of β-1,3-1,4-glucanase activity in cell pellets and in the supernatant of the recombinant yeast strain revealed that β-1,3-1,4-glucanase was successfully displayed on the cell surface of the yeast. The displayed β-1,3-1,4-glucanase activity in the recombinant yeast cells increased immediately after the addition of galactose and reached 45.1 U/ml after 32-h induction. The thermal stability of β-1,3-1,4-glucanase displayed in the recombinant yeast cells was enhanced compared with the free enzyme. These results suggest that the constructed food-grade yeast has the potential to improve the brewing properties of beer.     

杆状病毒后期启动子在大肠杆菌中启动CAT基因表达的研究

以CAT基因为报道基因,探讨了杆状病毒后期启动子在大肠杆菌中启动表达CAT基因的活性。结果显示在不含多角体基因及其启动子的质粒中,具合成启动子的表达量最高,野生型多角体启动子的表达量次之,而含ⅩⅣ多角体启动子的最低;具相同CAT基因启动子的质粒中,含多角体蛋白基因及其野生型启动子者较不含者强,含合成与ⅩⅣ启动子串联组合者与单纯ⅩⅣ启动子者表达量近乎一致,但均较前者为弱。以上结果表明,杆状病毒后期启动子在大肠杆菌与在昆虫细胞中的启动表达的能力并非完全一致。     

Emergence of a new satellite RNA from cucumber mosaic virus isolate P1

The cucumber mosaic virus (CMV) isolate P1 caused very mild symptoms on many plant species After serial passages by mechanical inoculation over five years, CMV P1 caused severe symptoms on several tobacco cultivars and tomato. A specific band of approximately 0.3 kb in length was amplified by RT-PCR with primers synthesized based on reported CMV satellite RNA (satRNA) sequences. Sequence analysis showed there were two satRNAs (Sat-P1-1 and Sat-P1-2). Sat-P1-1 contained 335 nucleotides, and Sat-P1-2 contained 394 nucleotides. These two satRNAs shared 64% overall nucleotide sequence homology, and differences between the two satRNAs included mutations as well as deletions. Sat-P1-1 was identical to a satRNA (Z96099) reported in 1995 in CMV P1. Based on differences in the sequence and secondary structure between these two satRNAs, we conclude that Sat-P1-2 represents the emergence of a new satellite (necrotic satellite) from attenuated satRNA populations. The possible effect of the emergence of this new satRNA is discussed. Project supported by research grants from the Teaching and Research Award Program for Outstanding Teachers in Higher Education Institutes of the Ministry of Education of China and by the National Outstanding Youth Foundations of National Natural Science Foundation of China (No. 30125032). PhD student in Zhejiang University, from Agrarian University of Havana, Cuba.     

The development of visual expectations in the first year

The development of expectations was investigated by using the Visual Expectations Procedure. In Experiment 1, 128 infants aged 6-, 9-, and 12-months-old saw two 40-trial sequences of a videotaped mechanical toy appearing in various locations. The sequences represented an alternation pattern (i.e., ABAB) or a complex pivot pattern (i.e., ABCBABCB). In Experiment 2, 76 infants aged 4-, 8-, and 12-months-old saw either a left-right alternation or a top-bottom alternation. Reaction time improved and the percentage of anticipations increased between 6 and 9 months in Experiment 1 and between 4 and 8 months in Experiment 2 but not thereafter. Anticipations for the pivot sequence and for younger infants on both sequences were often incorrect (i.e., gaze shifts occurred before stimulus onset but were not directed toward the upcoming stimulus). We conclude that young infants have expectations that reflect some degree of general or procedural knowledge, but it is not clear that this behavior implies specific, articulated expectations about upcoming events.     

基于多Agent的风光互补发电场控制系统研究

研究基于用多Agent技术的风光互补发电系统,设计一种风光互补发电电场控制系统,使系统能量输出最优化。     

偏振模色散对光孤子传输系统的影响

从考虑偏振模色散的光孤子的非线性薛定谔方程角度出发,用分步傅立叶方法对非线性耦合薛定谔方程进行求解。研究了偏振模色散效应对于光孤子传输系统的影响:首先在单个孤子脉冲的情况下,讨论了光孤子的自俘获效应对于偏振模色散的自适应能力,进而考虑更有意义的脉冲序列的情况,即因PMD引起的两个光孤子之间的相互作用以及能量损失而带来的系统损耗的问题。     

高等植物启动子功能和结构研究进展

启动子是植物基因工程中一个重要的研究对象，文章简述了启动子的定义、分类和启动子的研究策略。并着重从组成型启动子、组织特异型启动子和诱导型启动子3个方面介绍了它们的功能和结构的研究现状。提出了植物基因工程中启动子研究存在的问题与展望。     

C3H6/C3H8在AgCl、CuCl上吸附作用的量子化学计算研究

用ZINDO/ 1和abinitio/STO -6G 方法 ,对C3H6 、C3H8与AgCl、CuCl间的吸附态优化构型、原子净电荷、吸附能、前沿轨道能量作了计算。计算结果表明 ,C3H6 /C3H8在AgCl、CuCl上吸附作用机理为 :C3H6 在AgCl、CuCl上发生了强相互作用 ,为化学吸附 ;而C3H8与AgCl、CuCl仅发生了较弱的物理吸附 ,因此C3H6 /C3H8在AgCl、CuCl上具有较大的吸附选择性 ,比较而言 ,CuCl较AgCl更适合于作为C3H6 /C3H8分离吸附剂的活性组分     

Properties of frictional bridging in fiber pull-out for fiber-reinforced composites

Stress equilibrium equations, boundary-and continuity-conditions were used to establish a theoretical model of progressive debonding with friction at the debonded interface. On a basis of the minimum complementary energy principle, an expression for the energy release rateG was derived to explore the interfacial fracture properties. An interfacial debonding criterionG≥Γ _i was introduced to determine the critical debond length and the bridging law. Numerical calculation results for fiber-reinforced composite SCS-6/Ti-6A1-4V were compared with those obtained by using the shear-lag models.