8,12-sesquiterpene lactones(STLs)are an important class of natural products with unique pharmaceutical activities.For years the pathway leading to 8,12-STLs remains an enigma.Xanthium strumarium accumulates abundant 8...8,12-sesquiterpene lactones(STLs)are an important class of natural products with unique pharmaceutical activities.For years the pathway leading to 8,12-STLs remains an enigma.Xanthium strumarium accumulates abundant 8,12-STLs,and xanthatin is a characteristic 8,12-STL in it.Xanthatin has been previously postulated to be derived from germacrene A,but the steps from germacrene A to xanthatin are unknown.As part of an effort to understand the xanthatin biosynthetic pathway.This study reports the characterization of a unique germacrene A oxidase(XsGAO)from X.strumarium.Unlike a classical GAO enzyme,which is known to catalyze a three-step oxidation of germarene A to yield germacrene A acid(GAA),surprisingly,XsGAO catalyzed only one-step conversion of germacrene A to germacrene A alcohol.We discussed that GAO may be pressured to acquire a novel activity during the evolutionary path for the biosynthesis of 8,12-STLs.展开更多
The Daqin Railway is China’s first electrified double-track heavy-haul railway line dedicated to coal transportation.Over the years of operation,the tunnels have been covered with a thick layer of coal dust,which als...The Daqin Railway is China’s first electrified double-track heavy-haul railway line dedicated to coal transportation.Over the years of operation,the tunnels have been covered with a thick layer of coal dust,which also pervades in the air.Worse is that the coal dust has even buried the rail joints in some sections,making the repair and maintenance of the line difficult.This paper introduces a coal-dust removal device for railway tunnels that integrates pipeline transportation with dust-collection techniques.The device is mainly composed of a power system,a conveying system,a dust-filtration and collection system,and a control and protection system.The key technical elements of the system,such as the dust-extraction method and dust-filtration and collection parameters,are optimized based on the characteristics of the coal dust in the tunnel(obtained via field trials),which greatly enhances the adaptability of the device.Coal-dust removal efficiency reached over 20 t/h,which improves the working environment,reduces the intensity of manual work required and solves the problem of coal-dust removal from the most polluted area—within 500 m of the tunnel entrance.展开更多
基金This work was supported by a grant from the National Natural Science Foundation of China(31370339).
文摘8,12-sesquiterpene lactones(STLs)are an important class of natural products with unique pharmaceutical activities.For years the pathway leading to 8,12-STLs remains an enigma.Xanthium strumarium accumulates abundant 8,12-STLs,and xanthatin is a characteristic 8,12-STL in it.Xanthatin has been previously postulated to be derived from germacrene A,but the steps from germacrene A to xanthatin are unknown.As part of an effort to understand the xanthatin biosynthetic pathway.This study reports the characterization of a unique germacrene A oxidase(XsGAO)from X.strumarium.Unlike a classical GAO enzyme,which is known to catalyze a three-step oxidation of germarene A to yield germacrene A acid(GAA),surprisingly,XsGAO catalyzed only one-step conversion of germacrene A to germacrene A alcohol.We discussed that GAO may be pressured to acquire a novel activity during the evolutionary path for the biosynthesis of 8,12-STLs.
文摘The Daqin Railway is China’s first electrified double-track heavy-haul railway line dedicated to coal transportation.Over the years of operation,the tunnels have been covered with a thick layer of coal dust,which also pervades in the air.Worse is that the coal dust has even buried the rail joints in some sections,making the repair and maintenance of the line difficult.This paper introduces a coal-dust removal device for railway tunnels that integrates pipeline transportation with dust-collection techniques.The device is mainly composed of a power system,a conveying system,a dust-filtration and collection system,and a control and protection system.The key technical elements of the system,such as the dust-extraction method and dust-filtration and collection parameters,are optimized based on the characteristics of the coal dust in the tunnel(obtained via field trials),which greatly enhances the adaptability of the device.Coal-dust removal efficiency reached over 20 t/h,which improves the working environment,reduces the intensity of manual work required and solves the problem of coal-dust removal from the most polluted area—within 500 m of the tunnel entrance.
