生物信息学的形成与发展

1　什么是生物信息学 ?生物信息学是近 1 0年迅速发展起来的一门新兴交叉学科。“生物信息学”是英文单词“Ｂｉｏｉｎ ｆｏｒｍａｔｉｃｓ”的中文译名 ,美籍马来西亚裔学者ＨｗａＡ .Ｌｉｍ在 1 991年发表的文章中首次使用 ,但至今尚无完善的科学定义。笔者综合大量文献认为如下叙述可以作为生物信息学的定义 :生物信息学是应用计算机技术管理生物信息 ,交叉了生物学、数学、物理学、化学、计算机科学等众多学科的新兴学科。以核酸、蛋白质等生物大分子数据库为主要研究对象 ,以数学、信息学、计算机科学等为主要研究方法和手段 ,以计算机…     

A new class of endogenous human retroviral genomes

Human DNA contains multiple copies of a novel class of endogenous retroviral genomes. Analysis of a human recombinant DNA clone (HLM-2) containing one such proviral genome revealed that it is a mosaic of retroviral-related sequences with the organization and length of known endogenous retroviral genomes. The HLM-2 long terminal repeat hybridized with the long terminal repeat of the squirrel monkey virus, a type D retrovirus. The HLM-2 gag and pol genes share extensive nucleotide sequence homology with those of the M432 retrovirus (a type A-related retrovirus), mouse mammary tumor virus (a type B retrovirus), and the avian Rous sarcoma virus (a type C retrovirus). Nucleotide sequence analysis revealed regions in the HLM-2 pol gene that were as much as 70 percent identical to the mouse mammary tumor virus pol gene. A portion of the putative HLM-2 env gene hybridized with the corresponding region of the M432 viral genome.     

兼顾家具的形式与功能

木制家具的颁奖项目——Wood Awards（木材奖）一直以来都吸引着众多的目光。今年的Wood Awards（木材奖）吸引了大量各种各样的设计方案,包括从独立的单人作坊作品到零售商主推商品,从简单而优雅的设计方案到彻头彻尾的稀奇古怪的创意作品等等。     

Genomic heterogeneity of AIDS retroviral isolates from North America and Zaire

In an analysis of the genomic variation of AIDS retroviral isolates from patients living in New York, Alabama, and Zaire, restriction maps were constructed by using seven enzymes, each known to cleave the proviral DNA more than once, in conjunction with Southern blot analysis. The maps of LAV, HTLV-III, and ARV-2 as deduced from their published nucleotide sequences were included in this analysis. The results demonstrated that (i) several "signature" restriction sites were common to all isolates; (ii) with the exception of LAV and HTLV-III, the North American and European isolates were all different from one another and showed no geographical specificity; (iii) the African isolates as a group were more diverse than those from North America and Europe; and (iv) the genomic variability was concentrated within the env gene.     

A role for DNA-PK in retroviral DNA integration

Retroviral DNA integration is catalyzed by the viral protein integrase. Here, it is shown that DNA-dependent protein kinase (DNA-PK), a host cell protein, also participates in the reaction. DNA-PK-deficient murine scid cells infected with three different retroviruses showed a substantial reduction in retroviral DNA integration and died by apoptosis. Scid cell killing was not observed after infection with an integrase-defective virus, suggesting that abortive integration is the trigger for death in these DNA repair-deficient cells. These results suggest that the initial events in retroviral integration are detected as DNA damage by the host cell and that completion of the integration process requires the DNA-PK-mediated repair pathway.     

X chromosome-linked transmission and expression of retroviral genomes microinjected into mouse zygotes

A genomic clone consisting of the Moloney leukemia proviral genome with moderately repetitive mouse sequences was microinjected into the pronucleus of a mouse zygote. An animal was derived that carried multiple copies of proviral DNA in a tandem array. No evidence for homologous recombination was obtained. The viral genome was expressed in this animal and was transmitted as a single unit to its offspring. Subsequent breeding studies revealed that the proviral DNA had integrated on an X chromosome.     

Integrase inhibitors and cellular immunity suppress retroviral replication in rhesus macaques

We describe the efficacy of L-870812, an inhibitor of HIV-1 and SIV integrase, in rhesus macaques infected with the simian-human immunodeficiency virus (SHIV) 89.6P. When initiated before CD4 cell depletion, L-870812 therapy mediated a sustained suppression of viremia, preserving CD4 levels and permitting the induction of virus-specific cellular immunity. L-870812 was also active in chronic infection; however, the magnitude and durability of the effect varied in conjunction with the pretreatment immune response and viral load. These studies demonstrate integrase inhibitor activity in vivo and suggest that cellular immunity facilitates chemotherapeutic efficacy in retroviral infections.     

Distinctive termini characterize two families of human endogenous retroviral sequences

Human DNA contains many copies of endogenous retroviral sequences. Characterization of molecular clones of these structures reveals the existence of two related families. One family consists of full-length (8.8 kilobases) proviral structures, with typical long terminal repeates (LTR's). The other family consists of structures, which contain only 4.1 kilobases of gag-pol sequences, bounded by a tandem array of imperfect repeats 72 to 76 base pairs in length. Typical LTR sequences that exist as solitary elements in the genome were cloned and characterized.     

小鼠H1foo逆转录病毒载体的构建及表达

【目的】构建小鼠pMX-H1foo逆转录病毒载体,并使其在小鼠胚胎成纤维细胞(MEF)中异位表达,为进一步研究H1foo在重编程方面的作用奠定理论基础。【方法】根据NCBI公布的小鼠H1foo基因的mRNA序列设计引物,以小鼠卵巢组织总RNA为模板,RT-PCR扩增小鼠H1foo CDS序列,并连接到逆转录病毒载体pMX上。经双酶切鉴定和测序比对正确后,利用磷酸钙转染包装细胞plat-E的方法制备H1foo病毒液并感染MEF细胞,进一步收集感染的细胞进行半定量RT-PCR和免疫荧光染色检测,分析其在细胞中的表达情况。【结果】克隆得到915bp的H1foo基因,构建得到逆转录病毒载体pMX-H1foo。该载体制备的病毒能够感染MEF细胞,并且H1foo在MEF细胞中与细胞核共定位,而对照组绿色荧光蛋白(GFP)遍布整个细胞。【结论】成功构建了pMX-H1foo逆转录病毒载体,并在MEF中进行表达。     

设施葡萄观光园的树形与修剪

针对中国迅速发展设施葡萄观光园,提出了水平棚架、倾斜式小棚架和Y型架3种架形,并介绍了各种架形相应变化的树形,以及各种树形定植方法、幼苗管理、更新修剪的技术措施,为设施观光葡萄园的标准化建园和葡萄的稳产高效提供了一条新途径。     

Construction and recovery of viable retroviral genomes carrying a bacterial suppressor transfer RNA gene

The integration of retroviral genomes into cellular DNA can induce mutations by altering the expression of nearby cellular genes and can serve to identify the gene affected. The construction of a retrovirus that stably carries a suppressor transfer RNA gene from Escherichia coli has allowed facile recovery of the viral genome in vectors marked with amber mutations. This virus can be used for rapid isolation of cellular sequences at the site of proviral insertion.     

透视图的改造和新形式

提出了目前的透视图不能作效果图的新论点,并从理论上进行了证明。同时也列出了改造目前透视图的几种方法,通过比较,确立了在透视图上增加带有标尺的图框线和指引线为最好形式。改造后的透视图不但可作效果图,而且也有反求功能。同时也使透视图的形式与其它工程图样相统一。     

幂零矩阵的标准形

利用幂零矩阵的概念,在一般数域上讨论了幂零矩阵的一些性质,给出了矩阵是幂零矩阵的一个充要条件,最后利用幂零线性变换的概念,在一般数域上讨论了幂零线性变换一定存在一组基使其在这组基下的矩阵是若当形矩阵,从而给出幂零矩阵的若当标准形.     

钻尖磨损形态

In this paper, we study the wear form of a conventional HSS W18Cr4V drill in drilling the quenched steel with middle hardness(HRC36-40).The drilling conditions and the optimization of the drill point are discussed.