采用聚焦离子束定点切割技术(Focused ion beam,FIB),透射电镜(Transmission electron microscopy,TEM)、高角度环形暗场扫描透射电镜(High angle annular dark field scanning transmission electron microscopy,HAADF-STEM)和扫描电镜...采用聚焦离子束定点切割技术(Focused ion beam,FIB),透射电镜(Transmission electron microscopy,TEM)、高角度环形暗场扫描透射电镜(High angle annular dark field scanning transmission electron microscopy,HAADF-STEM)和扫描电镜(Scanning electron microscopy,SEM)等技术手段,对Mg-7Gd-5Y-1Nd-2Zn-0.5Zr合金铸态及(515℃,48 h)均匀化态的组织形貌进行观察分析。结果表明:铸态合金晶界共晶组织中含有(Mg,Zn)_(3)RE相(FCC,a=0.72 nm)、Mg_(5)(RE,Zn)相(FCC,a=2.24 nm)及块状长周期堆垛有序(Long-period stacking ordered,LPSO)相。其中LPSO相主要为18R结构,存在少量14H结构,局部区域存在少量不完整周期的LPSO结构;此外合金中存在分布于共晶相附近的微米级富RE相以及分布于晶粒内部的微米级富Zr颗粒。经过(515℃,48 h)均匀化热处理,晶界(Mg,Zn)_(3)RE相和Mg_(5)(RE,Zn)相完全回溶,残留相主要为14H-LPSO相,局部区域存在具有不同晶体结构的LPSO过渡相。在铸态合金的晶粒内部,沿[1120]_(a)晶带轴观察,发现存在几个原子面至纳米尺度的LPSO构建块,由不同数量的LPSO构建块单元(4个RE/Zn原子层)及Mg原子层交替堆垛构成,RE/Zn与Mg原子层堆垛次序不具备完整周期性;均匀化热处理后,晶内的LPSO构建块几乎回溶,仅剩下极少量单个LPSO构建块单元。沿[0001]_(a)晶带轴观察,晶粒内部存在多种分布方式的富RE/Zn原子柱,为Mg-Gd-Y系镁合金时效过程β′析出序列中GP区的早期结构。展开更多
The implementation of multiple enzymes for chemical production in a cell‐free scenario is an emerging field in biomanufacturing.It enables the redesign and reconstitution of new enzymatic routes for producing chemica...The implementation of multiple enzymes for chemical production in a cell‐free scenario is an emerging field in biomanufacturing.It enables the redesign and reconstitution of new enzymatic routes for producing chemicals that may be hard to obtain from natural pathways.Although the construction of a cell‐free multienzyme system is highly flexible and adaptable,it is challenging to make all enzymatic reactions act in concert.Recently,modular construction has been conceptual‐ized as an effective way to harmonize diverse enzymatic reactions.In this review,we introduce the concept of a multienzyme module and exemplify representative modules found in Nature.We then categorize recent developments of synthetic multienzyme modules into main‐reaction modules and auxiliary modules according to their roles in reaction routes.We highlight four main‐reaction mod‐ules that can perform carbon metabolism,carbon assimilation,protein glycosylation and nonribo‐somal peptide synthesis,and exemplify auxiliary modules used for energy supply,protection and reinforcement for main reactions.The reactor‐level modularization of multienzyme catalysis is also discussed.展开更多
文摘采用聚焦离子束定点切割技术(Focused ion beam,FIB),透射电镜(Transmission electron microscopy,TEM)、高角度环形暗场扫描透射电镜(High angle annular dark field scanning transmission electron microscopy,HAADF-STEM)和扫描电镜(Scanning electron microscopy,SEM)等技术手段,对Mg-7Gd-5Y-1Nd-2Zn-0.5Zr合金铸态及(515℃,48 h)均匀化态的组织形貌进行观察分析。结果表明:铸态合金晶界共晶组织中含有(Mg,Zn)_(3)RE相(FCC,a=0.72 nm)、Mg_(5)(RE,Zn)相(FCC,a=2.24 nm)及块状长周期堆垛有序(Long-period stacking ordered,LPSO)相。其中LPSO相主要为18R结构,存在少量14H结构,局部区域存在少量不完整周期的LPSO结构;此外合金中存在分布于共晶相附近的微米级富RE相以及分布于晶粒内部的微米级富Zr颗粒。经过(515℃,48 h)均匀化热处理,晶界(Mg,Zn)_(3)RE相和Mg_(5)(RE,Zn)相完全回溶,残留相主要为14H-LPSO相,局部区域存在具有不同晶体结构的LPSO过渡相。在铸态合金的晶粒内部,沿[1120]_(a)晶带轴观察,发现存在几个原子面至纳米尺度的LPSO构建块,由不同数量的LPSO构建块单元(4个RE/Zn原子层)及Mg原子层交替堆垛构成,RE/Zn与Mg原子层堆垛次序不具备完整周期性;均匀化热处理后,晶内的LPSO构建块几乎回溶,仅剩下极少量单个LPSO构建块单元。沿[0001]_(a)晶带轴观察,晶粒内部存在多种分布方式的富RE/Zn原子柱,为Mg-Gd-Y系镁合金时效过程β′析出序列中GP区的早期结构。
文摘The implementation of multiple enzymes for chemical production in a cell‐free scenario is an emerging field in biomanufacturing.It enables the redesign and reconstitution of new enzymatic routes for producing chemicals that may be hard to obtain from natural pathways.Although the construction of a cell‐free multienzyme system is highly flexible and adaptable,it is challenging to make all enzymatic reactions act in concert.Recently,modular construction has been conceptual‐ized as an effective way to harmonize diverse enzymatic reactions.In this review,we introduce the concept of a multienzyme module and exemplify representative modules found in Nature.We then categorize recent developments of synthetic multienzyme modules into main‐reaction modules and auxiliary modules according to their roles in reaction routes.We highlight four main‐reaction mod‐ules that can perform carbon metabolism,carbon assimilation,protein glycosylation and nonribo‐somal peptide synthesis,and exemplify auxiliary modules used for energy supply,protection and reinforcement for main reactions.The reactor‐level modularization of multienzyme catalysis is also discussed.
