三维石墨烯/过渡金属氧化物超级电容器复合材料的研究进展

超级电容器是一种介于电介质电容器和电池之间的储能装置,它拥有强大的输出功率、长效的使用寿命以及快速充放电能力,长期以来备受关注。作为一种新型超级电容器电极材料,三维石墨烯(3DGN)能够缩短电解质离子的扩散距离,提供快速电子输运通道,并能充当骨架与过渡金属氧化物进行复合,实现两者的协同作用。本文介绍了三维石墨烯的不同制备工艺,在此基础上,对三维石墨烯与过渡金属氧化物的复合工艺进行了进一步的总结。最后对三维石墨烯/过渡金属氧化物在超级电容器应用中的优势及目前存在的问题进行了概括分析。

Biosynthesis of clinically used antibiotic fusidic acid and identification of two short-chain dehydrogenase/reductases with converse stereoselectivity

Fusidic acid is the only fusidane-type antibiotic that has been clinically used. However,biosynthesis of this important molecule in fungi is poorly understood. We have recently elucidated the biosynthesis of fusidane-type antibiotic helvolic acid, which provides us with clues to identify a possible gene cluster for fusidic acid(fus cluster). This gene cluster consists of eight genes, among which six are conserved in the helvolic acid gene cluster except fusC1 and fusB1. Introduction of the two genes into the Aspergillus oryzae NSAR1 expressing the conserved six genes led to the production of fusidic acid. A stepwise introduction of fusC1 and fusB1 revealed that the two genes worked independently without a strict reaction order. Notably, we identified two short-chain dehydrogenase/reductase genes fusC1 and fusC2 in the fus cluster, which showed converse stereoselectivity in 3-ketoreduction. This is the first report on the biosynthesis and heterologous expression of fusidic acid.

Extensive expansion of the chemical diversity of fusidane-type antibiotics using a stochastic combinational strategy

Fusidane-type antibiotics,represented by helvolic acid,fusidic acid and cephalosporin P1,are fungi-derived antimicrobials with little cross-resistance to commonly used antibiotics.Generation of new fusidane-type derivatives is therefore of great value,but this is hindered by available approaches.Here,we developed a stochastic combinational strategy by random assembly of all the post-tailoring genes derived from helvolic acid,fusidic acid,and cephalosporin P1 biosynthetic pathways in a strain that produces their common intermediate.Among a total of 27 gene combinations,24 combinations produce expected products and afford 58 fusidane-type analogues,of which 54 are new compounds.Moreover,random gene combination can induce unexpected activity of some post-tailoring enzymes,leading to a further increase in chemical diversity.These newly generated derivatives provide new insights into the structure-activity relationship of fusidane-type antibiotics.The stochastic combinational strategy established in this study proves to be a powerful approach for expanding structural diversity of natural products.