A real-time qPCR assay for the detection of the nifH gene of Methanobrevibacter smithii, a potential indicator of sewage pollution

Aims: To degrade ether‐type polyurethane (ether‐PUR), ether‐PUR–degrading micro‐organism was isolated. Moreover, ether‐PUR–degrading mechanisms were analysed using model compounds of ether‐PUR. Methods and Results: A fungus designated as strain PURDK2, capable of changing the configuration of ether‐PUR, has been isolated. This isolated fungus was identified as Alternaria sp. Using a scanning electron microscope, the grid structure of ether‐PUR was shown to be melted and disrupted by the fungus. The degradation of ether‐PUR by the fungus was analysed, and the ether‐PUR was degraded by the fungus by about 27·5%. To analyse the urethane‐bond degradation by the fungus, a degraded product of ethylphenylcarbamate was analysed using GC/MS. Aniline and ethanol were detected by degradation with the supernatant, indicating that the fungus secreted urethane‐bond–degrading enzyme(s). PURDK2 also degraded urea bonds when diphenylmethane‐4,4′‐dibutylurea was used as a substrate. Conclusions: The enzyme(s) from PURDK2 degraded urethane and urea bonds to convert the high molecular weight structure of ether‐PUR to small molecules; and then the fungus seems to use the small molecules as an energy source. Significance and Impact of the Study: Ether‐PUR–degrading fungus, strain PURDK2, was isolated, and the urethane‐ and urea‐bonds–degrading enzymes from strain PURDK2 could contribute to the material recycling of ether‐PUR.     

A divalent FHA/BRCT‐binding mechanism couples the MRE11–RAD50–NBS1 complex to damaged chromatin

The MRE11–RAD50–NBS1 (MRN) complex accumulates at sites of DNA double‐strand breaks in large chromatin domains flanking the lesion site. The mechanism of MRN accumulation involves direct binding of the Nijmegen breakage syndrome 1 (NBS1) subunit to phosphorylated mediator of the DNA damage checkpoint 1 (MDC1), a large nuclear adaptor protein that interacts directly with phosphorylated H2AX. NBS1 contains an FHA domain and two BRCT domains at its amino terminus. Here, we show that both of these domains participate in the interaction with phosphorylated MDC1. Point mutations in key amino acid residues of either the FHA or the BRCT domains compromise the interaction with MDC1 and lead to defects in MRN accumulation at sites of DNA damage. Surprisingly, only mutation in the FHA domain, but not in the BRCT domains, yields a G2/M checkpoint defect, indicating that MDC1‐dependent chromatin accumulation of the MRN complex at sites of DNA breaks is not required for G2/M checkpoint activation.     

无选择标记和载体骨干序列的Xa21转基因水稻的获得

利用双右边界T-DNA载体通过根癌农杆菌介导法将水稻白叶枯病广谱抗性基因Xa21导入杂交稻重要恢复系C418中。T0代共获得27个独立转基因株系,通过田间抗性鉴定与PCR分析,有17个株系的Xa21基因分子鉴定为阳性,且对白叶枯病原菌P6生理小种具有抗性。通过对17个株系的后代植株进行田间抗性鉴定,分子标记辅助选择及Southern杂交分析,结果显示4个株系的T1代植株中能分离出无潮霉素标记基因的Xa21转基因植株。无选择标记Xa21转基因株系的获得率为15%。PCR检测还表明,这些无选择标记的Xa21转基因植株不带有载体骨架序列。通过对转基因后代进一步的抗性鉴定与PCR辅助选择,获得了无选择标记和载体骨架序列的转基因Xa21纯合的抗白叶枯病水稻。     

心脏特异性高度表达的抗凋亡蛋白——ARC

与凋亡(apoptosis)相关的许多心脏疾病如心肌梗死、心肌病及心衰等严重威胁着人类的健康和生命.寻找有效手段防治这些心脏病是当前医学研究的热点.ARC(带有caspase富集功能域的凋亡抑制因子)是新近发现的唯一在心脏大量且特异表达的抗凋亡蛋白,其全称是带有caspase富集功能域的凋亡抑制因子.ARC可被持续性磷酸化并参与阻断凋亡发生途径的多个层面.因此,ARC是一种强大的抗心肌凋亡蛋白.     

Colominic acid inhibits the proliferation of cultured bovine aortic endothelial cells and injures their monolayers: cell density-dependent effects prevented by sulfation

Colominic acid (CA), produced by Escherichia coli K1, is a polymer of sialic acid linked through alpha (2-->8) glycosidic linkages. Although there are several studies on the biological activities of chemically sulfated CA, the activity of CA has been incompletely understood. In the present study, we investigated the effects of CA, prepared as an alpha2,8-linked homopolymer of N-acetylneuraminic acid, on the proliferation and monolayer maintenance of bovine aortic endothelial cells in culture. The results indicate that CA potently inhibits the proliferation of sparse endothelial cells without nonspecific cell damage. The inhibitory effect of CA was markedly stronger than those of sodium spirulan and calcium spirulan, known polysaccharides that inhibit endothelial cell proliferation. On the other hand, in dense endothelial cells, CA induced nonspecific cell damage and markedly injured the monolayer. These results indicate that CA has two distinct effects on vascular endothelial cells: one is the inhibition of proliferation when the cell density is low, and the other is the nonspecific cytotoxicity when the cell density is high. Interestingly, these cell density-dependent effects of CA could be prevented by sulfation of the CA chains. Therefore, it is concluded that CA not only inhibits the proliferation of sparse endothelial cells without nonspecific cell damage but also injures dense cells in a monolayer by nonspecific cytotoxicity, which can be prevented by sulfation of the polysaccharide.     

喜树碱的碱水法提取新工艺

本文根据喜树碱在一定条件下开环和闭环的可逆性,设计了喜树碱的水法提取工艺。