水杨醛缩酪氨酸还原Schiff碱铜配合物的合成、结构及其与DNA键合作用的光谱学研究

利用水杨醛缩酪氨酸还原schiff碱(H2styr),合成了一个具有一维螺旋链结构的铜配合物,解析了其单晶结构,并用电子光谱、荧光光谱研究了该配合物和小牛胸腺DNA之间的相互作用.结果表明,当加入一定量的DNA时,电子光谱的最大吸收峰明显红移,产生减色效应;同时配合物也能较大程度地淬灭EB-DNA复合物的荧光,表明配合物与DNA存在插入结合作用     

DNA methylation status of H19 and Xist genes in lungs of somatic cell nuclear transfer bovines

In somatic cell nuclear transfer （SCNT） technologies, the donor cell＇s nuclei need to be epigenetically reprogrsmmed for embryonic development. The incomplete reprogramming of donor cell nuclei has been Implicated as s primary reason for the low efficiency of SCNT. DNA methylstion is s major epigenetic modification of the genome that regulates crucial aspects of genome function, including establishment of genomic imprinting. In order to make sure whether the DNA methylstion reprogramming is efficient in SCNT animals, we analyzed the DNA methylstion status of two imprinting genes, H19 and Xist, in lungs of deceased SCNT bovines that died within 48 h of birth using bisulfite sequencing analysis. Our findings demonstrated that cloned bovines showed significantly lower DNA methylstion of H19 than controls （P〈0.05）, and three tested CpGs sites （1, 2, 3） exhibited unmethylstion in one cloned bovine （9C3）; however, Xist showed similar DNA methylation levels between clones and controis, and both showed hypermethylstion （96.11% and 86.67%）.     

五种提取草珊瑚叶片总DNA方法的比较研究

运用五种方法提取草珊瑚叶片总DNA。结果证明,加入PVP（聚乙烯吡咯烷酮）的改良CTAB法可以有效地提取产量高、质量高的草珊瑚叶片的总DNA。为草珊瑚及其它草珊瑚属植物的起源、分类、亲缘关系分析及品种特征图谱的建立提供可借鉴的依据。     

Isolation and identification of Sclerotinia stem rot causal pathogen in Arabidopsis thaliana

A new stem rot disease is found to occur naturally on Arabidopsis plants in greenhouses of Fuzhou, China. In order to identify its pathogen, we conducted a series of fungal isolation and purification, plant reinoculation, and ascus and ascospore induction from the sclerotia. The isolate caused typical water-soaked lesions after reinoculation and produced sclerotia both on Arabidopsis plants and culture medium plates, and the sclerotia could be induced to produce discal apothecia and 8 binucleate ascospores per ascus. These disease symptom and fungal morphology data revealed that the fungus Sclerotinia sclerotiorum （Lib.） de Bary was the pathogen for Arabidopsis stem rot. To confirm this, we further amplified its large subunit ribosomal DNA （LSU rDNA） by polymerase chain reaction （PCR）, and compared the sequence with the known LSU rDNA sequences in GenBank. The results show that the sequence shares the highest identities with the LSU rDNAs of different S. sclerotiorum strains. Taking all these data together, we concluded that the fungus that caused the Arabidopsis stem rot is S. sclerotiorum （Lib.） de Bary. This is the first report that Arabidopsis is naturally infected by S. sclerotiorum.     

新课程背景下高中生物思想模型的建构探讨

本文结合自身的教学实际,以DNA分子的双螺旋结构模型为例,探讨了生物思想模型的建构过程和方法,论述了生物思想模型的教育价值。     

Gene association study with SVM, MLP and cross validation for diagnosis of diseases

Gene association study is one of the major challenges of biochip technology both for gene diagnosis where only a gene subset is responsible to some diseases, and for treatment of curse of dimensionality which occurs especially in DNA microarray datasets where there are more than thousands of genes and only a few number of experiments (samples). This paper presents a gene selection method by training linear support vector machine (SVM)/nonlinear MLP (multi-layer perceptron) classifiers and testing them with cross validation for finding a gene subset which is optimal/suboptimal for diagnosis of binary/multiple disease types. Genes are selected with linear SVM classifier for the diagnosis of each binary disease types pair and tested by leave-one-out cross validation; then, genes in the gene subset initialized by the union of them are deleted one by one by removing the gene which brings the greatest decrease of the generalization power, for samples, on the gene subset after removal, where generalization is measured by training MLPs with leave-one-out and leave-4-out cross validations. The proposed method was tested with experiments on real DNA microarray MIT data and NCI data. The result shows that it outperforms conventional SNR method in separability of the data with expression levels on selected genes. For real DNA microarray MIT/NCI data, which is composed of 7129/2308 effective genes with only 72/64 labeled samples belonging to 2/4 disease classes, only 11/6 genes are selected to be diagnostic genes. The selected genes are tested by classification of samples on these genes with SVM/MLP with leave-one-out/both leave-one-out and leave-4-out cross validations. The result of no misclassification indicates that the selected genes can be really considered as diagnostic genes for the diagnosis of the corresponding diseases.     

Type II restriction endonucleases: structure and mechanism

Type II restriction endonucleases are components of restriction modification systems that protect bacteria and archaea against invading foreign DNA. Most are homodimeric or tetrameric enzymes that cleave DNA at defined sites of 4–8 bp in length and require Mg²⁺ ions for catalysis. They differ in the details of the recognition process and the mode of cleavage, indicators that these enzymes are more diverse than originally thought. Still, most of them have a similar structural core and seem to share a common mechanism of DNA cleavage, suggesting that they evolved from a common ancestor. Only a few restriction endonucleases discovered thus far do not belong to the PD...D/ExK family of enzymes, but rather have active sites typical of other endonuclease families. The present review deals with new developments in the field of Type II restriction endonucleases. One of the more interesting aspects is the increasing awareness of the diversity of Type II restriction enzymes. Nevertheless, structural studies summarized herein deal with the more common subtypes. A major emphasis of this review will be on target site location and the mechanism of catalysis, two problems currently being addressed in the literature.Received 15 November 2004; accepted 9 December 2004     

几种番茄品种基因组DNA的相似指数初步分析

用４种随机引物（１０ｂｐ）,对普通番茄５个品种的基因组ＤＮＡ进行了ＰＣＲ扩增,并对其ＲＡＰＤ带谱进行了统计处理,发现不同随机引物扩增出来的ＲＡＰＤ标记所表现的相似指数有所不同,综合考虑,普通番茄种内不同品种同ＤＮＡ多态性保持了较高的稳定性。     

菠萝DNA导入黄瓜的初步研究

以菠萝为供体,黄瓜为受体,应用花粉管通道导入外源ＤＮＡ技术,在黄瓜自花授粉后直接导入菠萝ＤＮＡ,导入后代在产量、糖分含量等性状上产生了变异。结果表明：利用花粉管通道直接导入外源ＤＮＡ是改良黄瓜品种的有效技术,这一技术将在作物品种改良及远缘杂交方面起着非常重要的作用。