Microbial thermosensors

Temperature is among the most important of the parameters that free-living microbes monitor. Microbial physiology needs to be readjusted in response to sudden temperature changes. When the ambient temperature rises or drops to potentially harmful levels, cells mount protective stress responses—so-called heat or cold shock responses, respectively. Pathogenic microorganisms often respond to a temperature of around 37°C by inducing virulence gene expression. There are two main ways in which temperature can be measured. Often, the consequences of a sudden temperature shift are detected. Such indirect signals are known to be the accumulation of denatured proteins (heat shock) or stalled ribosomes (cold shock). However, this article focuses solely on direct thermosensors. Since the conformation of virtually every biomolecule is susceptible to temperature changes, primary sensors include DNA, RNA, proteins and lipids.     

Oxidative damages to DNA by indoor PM10s: Their relationships with trace element compositions

Plasmid DNA assay and ICP-MS analysis were conducted in order to investigate the bioreactivity of inhalable particles (PM10) and the relationship between bioreactivity and trace element compositions of PM10 in Beijing air. A total of four PM10 samples were carefully selected to represent the indoor and corresponding outdoor environments: one from urban smoker's home, two from non-smoker's homes, and the other from the outdoor. In general, the oxidative damage by indoor PM10 was slightly higher than that of outdoor. Among the four sets of samples, the PM10 from the smoker's home had a lowest TD50 (toxic dose of PM10 causing 50% DNA to be damaged), being 100 μg·mL-1, suggesting the highest bioreactivity. The heavy metals are believed to be the main reason for oxidative damage to plasmid DNA. The ICP-MS analysis combined with the DNA assay showed that the water-soluble zinc levels had better relationship with TD50 values than other elements, implying that water-soluble zinc might play an important role in the damage of DNA. It is concluded that the PM10 in smoker's home had the highest level of water-soluble zinc as well as the lowest TD50 (highest bioreactivity). Iron is considered to be one of the most bioreactive elements, but it will cause little damage to plasmid DNA, probably because iron is mainly in water-insoluble state in Beijing PM10.     

微生物之间竞争模型的全局分析

本文讨论具有再生养分流的具有质粒与不具有质粒微生物之间竞争的数学模型．假定再生养分流不具有时滞时，我们对的模型的平衡位置进行了全局分析．     

pEgr-Endostatin重组质粒联合电离辐射抗肿瘤效应的实验研究

目的研究pEgr-Endostatin辐射诱导肿瘤的表达特性及其抗肿瘤作用,为提高临床肿瘤放疗疗效提供实验证据.方法 Western blotting法检测pEgr-Endostatin重组质粒联合电离辐射诱导黑色素瘤B16细胞蛋白表达;建立动物模型,用ELISA法检测不同处理组Endostatin的剂量水平,比较不同处理方式的差异.结果 Western blotting法检测结果显示:重组质粒转染的黑色素瘤B16细胞上清中均有Endostatin蛋白表达,而未转染重组质粒的B16细胞和转染空质粒的B16细胞上清中未见Endostatin蛋白表达.ELISA法检测结果表明:体外接受2~10 Gy X射线照射,Endostatin表达水平明显增加,且照射剂量为4 Gy时Endostatin的表达水平最高.2 Gy照射8~72 h后,Endostatin表达水平与假照射组比较明显增加,在48 h时Endostatin表达水平最高.动物实验表明:荷瘤+25 Gy照射组、荷瘤+pEgr-Endostatin照射组、荷瘤+pc DNA3.1+25 Gy照射组和荷瘤+pEgr-Endostatin+25Gy照射组肿瘤生长率显著低于单纯荷瘤组(P0.05#0.01),荷瘤+pEgr-Endostatin+25 Gy照射组亦明显低于荷瘤+25 Gy照射组和荷瘤+pEgr-Endostatin组(P0.05#0.01).结论 pEgr-Endostatin重组质粒联合电离辐射能使Endostatin蛋白表达增加,从而抑制血管内皮细胞生长、发挥抗肿瘤作用.     

基于DNA计算的最大权团问题设计

介绍了最大团和最大权团的概念和国内外学者运用DNA计算解决最大团的研究成果;结合前人运用质粒、二进制、粘贴模型等方式进行DNA计算操作的原理,设计了新的用于解决最大权团问题的算法步骤,大大提高了算法效率,实现了最大团和最大权团的同步求解,对市场分析、方案选择等领域有一定的意义。     

甲酸钠的抗氧化作用

以溶血试验、红细胞还原型谷胱甘肽测定、受照南粒ＰＵＣ１８ＤＮＡ单链断裂的测定、受照小鼠肝和肾匀浆脂质过氧化物的测定作为指标，检测了甲酸钠的抗氧化作用。结果表明：甲酸钠能显著地降低受＾６０Ｃｏγ射线照射的红细胞的溶血水平；显著抑制ＶｉｔＣ／Ｆｅ＾＋＋诱导的红细胞悬液还原型谷胱甘肽的耗竭；显著抑制受质粒ＰＵＣ１８ＤＮＡ单链断裂程度；显著地抑制受照小鼠肝、肾匀浆丙二醛水平的升高，结果提示：内具有抗氧化作     

Ti质粒转化胡萝卜细胞的初步研究

本文报道了通过三亲酱将Ｐ＾ＢＩ１０１等Ｔｉ质粒从大肠杆菌（Ｅ．ｃｏｌｉＣ６００）中转移到发根农杆菌（Ａｇｒｏｂａｃｔｅｒｉｕｍ ｒｈｉｚｏｇｅｎｅｓ）中，并获得转移子，将上述转移子与胡萝卜悬浮细胞混合共培养后得到转化细胞。转化细胞在没加生长激素和细胞分裂素的情况下能知主生长，并获得愈伤组织。     

A novel salicylaldehyde dehydrogenase-NahV involved in catabolism of naphthalene from Pseudomonas putida ND6

A novel salicylaldehyde dehydrogenase involved in catabolism of naphthalene from Pseudomonas putida ND6, NahV, has been identified. NahV exhibited lower identity in amino acid sequence with the classic salicylaldehyde dehydrogenase, NahF, from P. putida ND6. This is the first report of an isofunctional enzyme of bacterial salicylaldehyde dehydrogenase. Comparison of Km and Vmax values of NahV and NahF demonstrated that NahF has a more efficient catalytic reaction than NahV, while NahV has much higher affinity for salicylaldehyde and NAD . Both enzymes exhibited broad substrate speci- ficities and catalyzed the oxidation of salicylaldehyde, 5-chlorosalicylaldehyde, formaldehyde, m-nitrobenzaldehyde, o-nitrobenzaldehyde, o-methoxybenxaldehyde, glutaraldehyde, caprylic aldehyde, and glyoxal. However, the relative rates at which the substituted analogs are transformed differ considerably. NahV activity could be enhanced by Fe2 , Cu2 and Zn2 ; whereas NahF activity could only be stimulated by Fe2 . NahF is more stable than NahV at elevated temperatures. Dot-blot hybridization analyses showed that nahF-like genes occurred in all naphthalene-degradation bacteria isolated in this study, whereas nahV-like genes were present in only some naphthalene-degrading bacteria.