The gene cluster cfaABCED’ of enterotoxigenic Escherichia coli, encoding the fimbriae which is called colonization factor antigen located on a plasmid. It is positively regulated by cfaR, a member of the AraC family,...The gene cluster cfaABCED’ of enterotoxigenic Escherichia coli, encoding the fimbriae which is called colonization factor antigen located on a plasmid. It is positively regulated by cfaR, a member of the AraC family, and the cfaD’ gene region, which is located downstream of cfaE and is homologous to cfaR, had been described as a truncated cryptic gene. In the present study we observed that the CFA/ fimbriae subunit, cfaB, was expressed in lower amount by the cfaABCED’ clone pNTP513 in host E. coli HB101. The expression of CFA/ diminished by deletion of cfaD’ gene region from pNTP513, and was restored by acquisition of cfaD’ in trans. Furthermore, CFA/ expression by cfaD’ deletion mutant, the cfaABCE clone, was remarkably increased by the presence of cfaD’ in trans in a topoisomerase A deficient strain of E. coli DM800. These data suggest that cfaD’ region is a functional region of gene, that regulates the CFA/ expression with cfaR by unknown mechanism.展开更多
捕集剂-C用一定量的甲醇溶剂溶解后,在催化剂作用下,对经过富集的辛·癸酸甲酯中的2-十一酮进行捕集,使之生成大分子化合物,此时,2-十一酮的转化率可达到96.8%。然后通过减压蒸馏,蒸出辛·癸酸甲酯。再对蒸馏残渣中的2-十一酮...捕集剂-C用一定量的甲醇溶剂溶解后,在催化剂作用下,对经过富集的辛·癸酸甲酯中的2-十一酮进行捕集,使之生成大分子化合物,此时,2-十一酮的转化率可达到96.8%。然后通过减压蒸馏,蒸出辛·癸酸甲酯。再对蒸馏残渣中的2-十一酮化合物在一定的酸性条件下进行水解,碱洗后,以一定量的溶剂萃取,取上层油相萃取液,减压蒸馏,收集1.1 k Pa,136~139℃馏分,得含量99%以上的比较纯净的2-十一酮。总回收率可以达到96%以上。展开更多
文摘The gene cluster cfaABCED’ of enterotoxigenic Escherichia coli, encoding the fimbriae which is called colonization factor antigen located on a plasmid. It is positively regulated by cfaR, a member of the AraC family, and the cfaD’ gene region, which is located downstream of cfaE and is homologous to cfaR, had been described as a truncated cryptic gene. In the present study we observed that the CFA/ fimbriae subunit, cfaB, was expressed in lower amount by the cfaABCED’ clone pNTP513 in host E. coli HB101. The expression of CFA/ diminished by deletion of cfaD’ gene region from pNTP513, and was restored by acquisition of cfaD’ in trans. Furthermore, CFA/ expression by cfaD’ deletion mutant, the cfaABCE clone, was remarkably increased by the presence of cfaD’ in trans in a topoisomerase A deficient strain of E. coli DM800. These data suggest that cfaD’ region is a functional region of gene, that regulates the CFA/ expression with cfaR by unknown mechanism.
文摘捕集剂-C用一定量的甲醇溶剂溶解后,在催化剂作用下,对经过富集的辛·癸酸甲酯中的2-十一酮进行捕集,使之生成大分子化合物,此时,2-十一酮的转化率可达到96.8%。然后通过减压蒸馏,蒸出辛·癸酸甲酯。再对蒸馏残渣中的2-十一酮化合物在一定的酸性条件下进行水解,碱洗后,以一定量的溶剂萃取,取上层油相萃取液,减压蒸馏,收集1.1 k Pa,136~139℃馏分,得含量99%以上的比较纯净的2-十一酮。总回收率可以达到96%以上。
