Ménage问题的一种粘贴DNA算法

 解决图论与排列组合难题是DNA计算领域的研究目标之一.为了使用分子生物方法解决Ménage问题,本文给出了Ménage问题的数学模型;并对解决该问题的难点进行了分析,提出一种解决方案,改进了该问题的数学模型;提出一种解决Ménage问题的粘贴DNA算法并简要分析了该算法的复杂度.为了提高效率,引入广义分离和广义多级分离操作;通过一个实例给出了实验操作步骤,对实验进行了模拟.     

霉变油炸小食品中鲜绿青霉菌的分离鉴定研究

食品安全问题是关系人体健康和国计民生的重大问题,已经引起人们的高度重视。利用稀释涂布法从霉变油炸小食品中分离获得1株菌,形态学观察初步鉴定为酵母菌。通过单因素试验及L9(34)正交试验对菌种的生长条件进行研究,确定最适培养温度38℃、培养时间75 h、摇床转速200 r/min、碳氮比5∶1。在真菌DNA提取过程中尝试了SDS法和CTAB法。除蛋白采取了酚/氯仿的方法 ,对所得样品进行DNA凝胶电泳、质量检测和PCR扩增产物。用18SrDNA ITS的直接测序法测序后构建系统发育树确定:该菌为鲜绿青霉菌(Penicillium viridicatum)。     

Role of ComEA in DNA uptake during transformation of competent Bacillus subtilis

The role of the competence protein ComEA in DNA uptake during transformation of competent Bacillus subtilis was analyzed by lysed-protoplast transformation (LP transformation). A comEA deletion mutant was constructed by a fusion polymerase chain reaction. Transformants of the mutant were obtained by LP transformation at a frequency of 1.1 × 10(2) transformants per μg DNA, representing a low relative efficiency of transformation [RET (mutant/wild type)] of 2.7 × 10(-6). This implied an important role of the protein during DNA uptake. When analyzing LP transformation of comEA with a plasmid (5.7 kb), a similar RET (mutant/wild type) of 5.6 × 10(-5) was obtained. Following addition of DNA into the comEA mutant culture, the number of transformants increased at a rate of 0.5 transformants/min, which was very low compared with the wild-type (6.9×10(4) transformants/min). However, even in the comEA mutant, DNA uptake began immediately after addition of DNA. Using co-transformation analysis of the comEA mutant, short linkages at distances of 2-156 kb could be detected, but not long linkages at distances of 671-1662 kb. Taken together, the results indicate that ComEA plays an important role in the transfer of transforming DNA into the DNA channel and in controlling the rate of DNA uptake.     

Large-scale genome reorganization in Saccharomyces cerevisiae through combinatorial loss of mini-chromosomes

A highly efficient technique, termed PCR-mediated chromosome splitting (PCS), was used to create cells containing a variety of genomic constitutions in a haploid strain of Saccharomyces cerevisiae. Using PCS, we constructed two haploid strains, ZN92 and SH6484, that carry multiple mini-chromosomes. In strain ZN92, chromosomes IV and XI were split into 16 derivative chromosomes, seven of which had no known essential genes. Strain SH6484 was constructed to have 14 mini-chromosomes carrying only non-essential genes by splitting chromosomes I, II, III, VIII, XI, XIII, XIV, XV, and XVI. Both strains were cultured under defined nutrient conditions and analyzed for combinatorial loss of mini-chromosomes. During culture, cells with various combinations of mini-chromosomes arose, indicating that genomic reorganization could be achieved by splitting chromosomes to generate mini-chromosomes followed by their combinatorial loss. We found that although non-essential mini-chromosomes were lost in various combinations in ZN92, one mini-chromosome (18kb) that harbored 12 genes was not lost. This finding suggests that the loss of some combination of these 12 non-essential genes might result in synthetic lethality. We also found examples of genome-wide amplifications induced by mini-chromosome loss. In SH6484, the mitochondrial genome, as well as the copy number of genomic regions not contained in the mini-chromosomes, was specifically amplified. We conclude that PCS allows for genomic reorganization, in terms of both combinations of mini-chromosomes and gene dosage, and we suggest that PCS could be useful for the efficient production of desired compounds by generating yeast strains with optimized genomic constitutions.     

新型肺癌压电DNA传感器的研制

在压电石英金电极上自组装半胱胺膜,通过1-乙基-3-(3-甲基氨丙基)碳二亚胺盐酸盐和N-羟基琥珀酰亚胺活化的羧基化碳纳米管交联半胱胺和DNA探针,构建新的压电DNA传感器,实现对肺癌特征DNA的压电检测。该传感器检测灵敏度为27.617Hz/(μg/mL),线性范围为0.02～7.50μg/mL,再生性能好。样本分析结果与聚合酶链式反应(PCR)法无显著差异,可用于临床检测。     

相似性度量在基因表达聚类分析中的应用研究

聚类分析是基因表达数据分析研究的主要技术之一,其算法的基本出发点在于根据对象间相似度将对象划分为不同的类,选择适当的相似性度量准则是获得有效聚类结果的关键。采用预处理过的基因数据集在不同相似性度量准则下进行的不同聚类算法的聚类分析,并得到聚类结果评价。其中算法本身的缺陷及距离相似性度量的局限性都是影响结果评价的因素,为了获得更有效的聚类结果,改进相关聚类算法并提出了一种比例相似性度量准则。     

浅谈转基因食品

利用基因工程技术生产的转基因食品的种类、数量在不断增长，转基因食品在赋予传统食品以新特性的同时其自身的安全问题也逐渐引起了人们的关注，本文就转基因食品原料的生产过程及转基因食品的特性和安全问题作了简单的论述。     

The Escherichia coli RecA protein complements recombination defective phenotype of the Saccharomyces cerevisiae rad52 mutant cells

The Saccharomyces cerevisiae rad52 mutants are sensitive to many DNA damaging agents, mainly to those that induce DNA double-strand breaks (DSBs). In the yeast, DSBs are repaired primarily by homologous recombination (HR). Since almost all HR events are significantly reduced in the rad52 mutant cells, the Rad52 protein is believed to be a key component of HR in S. cerevisiae. Similarly to the S. cerevisiae Rad52 protein, RecA is the main HR protein in Escherichia coli. To address the question of whether the E. coli RecA protein can rescue HR defective phenotype of the rad52 mutants of S. cerevisiae, the recA gene was introduced into the wild-type and rad52 mutant cells. Cell survival and DSBs induction and repair were studied in the RecA-expressing wild-type and rad52 mutant cells after exposure to ionizing radiation (IR) and methyl methanesulphonate (MMS). Here, we show that expression of the E. coli RecA protein partially complemented sensitivity and fully complemented DSB repair defect of the rad52 mutant cells after exposure to IR and MMS. We suggest that in the absence of Rad52, when all endogenous HR mechanisms are knocked out in S. cerevisiae, the heterologous E. coli RecA protein itself presumably takes over the broken DNA.     

HDA法用于检测肉中金黄色葡萄球菌的研究

本文研究了猪肉、牛肉、羊肉、鸡肉中金黄色葡萄球菌的依赖解旋酶恒温基因扩增检测方法(HDA法),以金黄色葡萄球菌耐热核酸酶nuc基因为目的基因,设计一对特异性引物,优化反应条件UvrD helicase、T4 gp32的浓度,通过赖解旋酶恒温基因扩增方法直接检测猪肉、牛肉、羊肉、鸡肉中金黄色葡萄球菌,扩增产物通过电泳进行检测。结果表明,HDA法检测肉中金黄色葡萄球菌的特异性强,试验涉及的其它菌株未发生扩增,只有金黄色葡萄球菌得到与设计序列长度一致的216 bp基因片段,检出限为101 CFU/g,优化确定UvrD helicase、T4 gp32的终浓度分别为0.1 μg、5.0 μg,该方法用于检测猪肉、牛肉、羊肉、鸡肉中金黄色葡萄球菌的灵敏度高,耗时短,为猪肉、牛肉、羊肉、鸡肉中金黄色葡萄球菌的快速检测提供了新的方法,也为其它食品中金黄色葡萄球菌的快速检测奠定了基础。