Synthesis and biological evaluation of 3-arylcoumarin derivatives as potential anti-diabetic agents

A variety of substituted 3-arylcoumarin derivatives were synthesised through microwave radiation heating. The method has characteristics of environmental friendliness, economy, simple separation, and purification process, less by-products and high reaction yield. Those 3-arylcoumarin derivatives were screened for antioxidant, α-glucosidase inhibitory and advanced glycation end-products (AGEs) formation inhibitory. Most compounds exhibited significant antioxidant and AGEs formation inhibitory activities. Anti-diabetic activity studies showed that compounds 11 and 17 were equipotent to the standard drug glibenclamide in vivo. According to the experimental results, the target compound 35 can be used as a lead compound for the development of new anti-diabetic drugs. The whole experiment showed that anti-diabetic activity is prevalent in 3-arylcoumarins, which added a new natural skeleton to the development of anti-diabetic active drugs.     

Fluorescent sensing platform based on polyethyleneimine-protected copper nanoclusters for detection of chromium(VI) in real samples

A new type of polyethyleneimine-protected copper nanoclusters (PEI-CuNCs) is favorably developed by a one-pot method under mild conditions. The obtained PEI-CuNCs is characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Fourier-transform infrared (FTIR) spectroscopy and other techniques. It is worth noting that the proposed PEI-CuNCs demonstrate a selective response to chromium(VI) over other competitive species. Fluorescence quenching of PEI-CuNCs is determined to be chromium(VI) concentrations dependence with a low limit of detection of 8.9 nM. What is more, the as-developed PEI-CuNCs is further employed in building a detection platform for portable recognition of chromium(VI) in real samples with good accuracy. These findings may offer a distinctive strategy for the development of methods for analyzing and monitoring chromium(VI) and expand their application in real sample monitoring.     

氨氮对3种吸附态亚硝化单胞菌的抑制动力学

[背景] 氨氮浓度会明显影响亚硝化单胞菌的活性,但氨氮浓度对吸附态亚硝化单胞菌菌种的抑制动力学尚缺乏研究。[目的] 研究氨氮浓度对3种吸附态亚硝化单胞菌（Nitrosomonas eutropha CZ-4、Nitrosomonas halophila C-19和Nitrosomonas europaea SH-3）的影响。[方法] 以碳酸钙作为吸附基质,设定氨氮浓度为25-1 000 mg/L,测定3种亚硝化单胞菌（N.eutropha CZ-4、N. halophila C-19和N. europaea SH-3）的亚硝氮积累速率与最大比生长速率,并通过Edwares2模型建立氨氧化的抑制动力学方程。[结果] N. halophila C-19在初始氨氮浓度为50-100 mg/L时的亚硝氮积累最快,N. europaea SH-3的亚硝氮积累则在初始氨氮浓度为50-200 mg/L时最快,而N. eutropha CZ-4则适于在初始氨氮浓度为50-400 mg/L时积累亚硝氮;N. eutropha CZ-4的最大比生长速率出现在初始氨氮浓度为50-400 mg/L时,明显高于N. halophila C-19（25-100 mg/L）,而N. europaea SH-3的生长速度在初始氨氮浓度为50-800 mg/L区间内无显著差异;N. europaea SH-3的K_I（922.76 mg/L）显著高于N. eutropha CZ-4（597.88 mg/L）,而CZ-4的K_I又显著高于N. halophila C-19（186.24 mg/L）,N. europaea SH-3的K_m（72.06 mg/L）显著高于N. halophila C-19（23.23 mg/L）。[结论] 3种吸附态亚硝化单胞菌的生长和氨氧化对氨氮浓度变化的响应存在明显差异,对于认识不同亚硝化单胞菌在不同氨氮浓度污水中的功能并开发相应的工程技术具有重要意义。     

乳链菌肽自身免疫基因nisI的表达对乳链菌肽产量的影响

【目的】通过基因工程手段增加乳链菌肽(nisin)自身免疫基因nisI在nisin产生菌Lactococcus lactisNZ9800/pHJ201中的表达水平,增强该菌对nisin的抗性,从而达到提高nisin产量的目的。【方法】将带有强组成型启动子P59的免疫基因nisI克隆到nisin表达质粒pHJ201上,将重组质粒引入L.lactis NZ9800中,使nisI基因过量表达,得到重组菌株L.lactis NZ9800/pHMI,并比较该重组菌株与对照菌株L.lactis NZ9800/pHJ201的生长曲线、对nisin的抗性水平、抑菌活性及nisin产量的差异。【结果】nisI的表达对重组菌的生长速度没有明显的影响,却能促使重组菌株对nisin的抗性水平提高25%、在发酵6h和8h时,nisin的产量分别提高32%和25%。【结论】增加乳链菌肽自身免疫基因nisI的表达可以提高产生菌对nisin的抗性,从而提高乳链菌肽产量。     

Inhibition of acetate accumulation leads to enhanced production of (R,R)-2,3-butanediol from glycerol in Escherichia coli

This work describes the production of (R,R)-2,3-butanediol in Escherichia coli using glycerol by metabolic engineering approaches. The introduction of a synthetic pathway converting pyruvate to (R,R)-2,3-butanediol into wild-type E. coli strain BW25113 led to the production of (R,R)-2,3-butanediol at a titer of 3.54?g/l and a yield of 0.131?g product/g glycerol (26.7?% of theoretical maximum) with acetate (around 3.00?g/l) as the dominant by-product. We therefore evaluated the impacts of deleting the genes ackA or/and poxB that are responsible for the major by-product, acetate. This increased production of (R,R)-2,3-butanediol to 9.54?g/l with a yield of 0.333?g product/g glycerol (68.0?% of theoretical maximum) in shake flask studies. The utilization of low-priced crude glycerol to produce value-added chemicals is of great significance to the economic viability of the biodiesel industry.     

前导肽二级结构对bovicin HJ50修饰和加工的影响

[目的]阐明羊毛硫细菌素bovicin HJ50前导肽的二级结构对原肽修饰和加工的影响规律.[方法]采用半体外生物合成系统构建boviein HJ50前导肽突变体,然后利用MALDI-TOF质谱鉴定成熟肽的修饰情况.同时,结合HPLC和抑菌活性分析其对成熟肽加工效率的影响.[结果]我们构建了6个bovicin HJ50前导肽二级结构相关的突变体(F-16A,V-15E,E-14L,E-8P,L-7D,L-4K).F-16A,V-15E,L-4K几乎不影响修饰和加工;E-14L和E-8P的修饰则发生了变化;另发现L-7D导致加工过程受到强烈抑制.[结论]Bovicin HJ50前导序列中保守的螺旋结构区对修饰酶BovM和蛋白酶BovT150活性都有不同程度影响,其二级结构的维持对bovicin HJ50的修饰和加工具有重要作用.     

Targeted deletion of mouse Rad1 leads to deficient cellular DNA damage responses

The Rad1 gene is evolutionarily conserved from yeast to human. The fission yeast Schizosaccharomyces pombeRad1 ortholog promotes cell survival against DNA damage and is required for G₂/M checkpoint activation. In this study, mouse embryonic stem (ES) cells with a targeted deletion of Mrad1, the mouse ortholog of this gene, were created to evaluate its function in mammalian cells. Mrad1^-/- ES cells were highly sensitive to ultraviolet-light (UV light), hydroxyurea (HU) and gamma rays, and were defective in G₂/M as well as S/M checkpoints. These data indicated that Mrad1 is required for repairing DNA lesions induced by UV-light, HU and gamma rays, and for mediating G₂/M and S/M checkpoint controls. We further demonstrated that Mrad1 plays an important role in homologous recombination repair (HRR) in ES cells, but a minor HRR role in differentiated mouse cells.