A new type of NaCS/PDMDAAC polyelectrolyte complex membrane prepared by interfacial reaction of sodium cellulose sulfate as polyanions and poly(dimethylallylammonium chloride)as polycations was proposed.The static con...A new type of NaCS/PDMDAAC polyelectrolyte complex membrane prepared by interfacial reaction of sodium cellulose sulfate as polyanions and poly(dimethylallylammonium chloride)as polycations was proposed.The static contact angle of the polyelectrolyte complex(PELC)membrane surface was measured to characterize membrane wettability.The effects of concentration of polyelectrolyte,molecular weight,and reaction time on contact angle were investigated.It was found that NaCS/PDMDAAC PELC membrane was hydrophilic.Its contact angle decreased with the increasing concentration of NaCS and molecular weight of PDMDAAC,and increased with the increasing concentration of PDMDAAC and reaction time.展开更多
In general,productions of natural pigment in submerged microorganism culture were much less than that in solid-state fermentation,because the solid-state culture can provide a support carrier for the mycelium. To impr...In general,productions of natural pigment in submerged microorganism culture were much less than that in solid-state fermentation,because the solid-state culture can provide a support carrier for the mycelium. To improve natural pigment production,the cultivation of Monascus purpureus in submerged encapsulated cell was investigated. Monascus purpureus immobilized in polyelectrolyte complex(PEC) microcapsules,which were pre-pared by sodium cellulose sulphate(NaCS) and poly-dimethyl-diallyl-ammonium chloride(PDMDAAC),was a good substitute for submerged cell culture because it mimicked the solid-state environment. The repeated-batch process with encapsulated cells was studied in flasks and a bubble column. The results indicated that the bubble column was more suitable for the encapsulation culture than the shaking flasks because of its good mass transfer performance and minor shear stress on cells. Owing to the protection of the microcapsule's membrane,Monascus purpureus in microcapsules increased approximately three times over that in free cell culture with negligible cell leakage to the medium. The pigment production in the bubble column finally reached 3.82(OD500) ,which was two times higher than in free cell culture. In addition,the duration of each batch was shortened to 15% of that in free cell culture.展开更多
Nascent polypeptide associated complex(NAC)and its two isolated subunits,αNAC and βNAC,play important roles in nascent peptide targeting.We determined a 1.9Åresolution crystal structure of the interaction core ...Nascent polypeptide associated complex(NAC)and its two isolated subunits,αNAC and βNAC,play important roles in nascent peptide targeting.We determined a 1.9Åresolution crystal structure of the interaction core of NAC heterodimer and a 2.4Åresolution crystal structure ofαNAC NAC domain homodimer.These structures provide detailed information of NAC heterodimerization and αNAC homodimerization.We found that the NAC domains of αNAC and βNAC share very similar folding despite of their relative low identity of amino acid sequences.Furthermore,different electric charge distributions of the two subunits at the NAC interface provide an explanation to the observation that the heterodimer of NAC complex is more stable than the single subunit homodimer.In addition,we successfully built a βNAC NAC domain homodimer model based on homologous modeling,suggesting that NAC domain dimerization is a general property of the NAC family.These 3D structures allow further studies on structurefunction relationship of NAC.展开更多
Plants use sophisticated mechanisms of gene expression to control senescence in response to environmental stress or aging.ORE1(Arabidopsis thaliana NAC092)is a master regulator of senescence that belongs to the plant-...Plants use sophisticated mechanisms of gene expression to control senescence in response to environmental stress or aging.ORE1(Arabidopsis thaliana NAC092)is a master regulator of senescence that belongs to the plant-specific NAC transcription factor protein family.ORE1 has been reported to bind to multiple DNA targets to orchestrate leaf senescence,yet the mechanistic basis for recognition of the cognate gene sequence remains unclear.Here,we report the crystal structure of the ORE1-NAC domain alone and its DNA-binding form.The structure of DNA-bound ORE1-NAC revealed the molecular basis for nucleobase recognition and phosphate backbone interactions.We showthat local versatility in the DNA-binding site,in combination with domain flexibility of the ORE-NAC homodimer,is crucial for the maintenance of binding to intrinsically flexible DNA.Our results provide a platformfor understanding other plant-specific NAC protein-DNA interactions as well as insight into the structural basis of NAC regulators in plants of agronomic and scientific importance.展开更多
文摘A new type of NaCS/PDMDAAC polyelectrolyte complex membrane prepared by interfacial reaction of sodium cellulose sulfate as polyanions and poly(dimethylallylammonium chloride)as polycations was proposed.The static contact angle of the polyelectrolyte complex(PELC)membrane surface was measured to characterize membrane wettability.The effects of concentration of polyelectrolyte,molecular weight,and reaction time on contact angle were investigated.It was found that NaCS/PDMDAAC PELC membrane was hydrophilic.Its contact angle decreased with the increasing concentration of NaCS and molecular weight of PDMDAAC,and increased with the increasing concentration of PDMDAAC and reaction time.
基金Supported by the National Basic Research Program of China（2007CB707805） the National Natural Science Foundation of China（20876139）
文摘In general,productions of natural pigment in submerged microorganism culture were much less than that in solid-state fermentation,because the solid-state culture can provide a support carrier for the mycelium. To improve natural pigment production,the cultivation of Monascus purpureus in submerged encapsulated cell was investigated. Monascus purpureus immobilized in polyelectrolyte complex(PEC) microcapsules,which were pre-pared by sodium cellulose sulphate(NaCS) and poly-dimethyl-diallyl-ammonium chloride(PDMDAAC),was a good substitute for submerged cell culture because it mimicked the solid-state environment. The repeated-batch process with encapsulated cells was studied in flasks and a bubble column. The results indicated that the bubble column was more suitable for the encapsulation culture than the shaking flasks because of its good mass transfer performance and minor shear stress on cells. Owing to the protection of the microcapsule's membrane,Monascus purpureus in microcapsules increased approximately three times over that in free cell culture with negligible cell leakage to the medium. The pigment production in the bubble column finally reached 3.82(OD500) ,which was two times higher than in free cell culture. In addition,the duration of each batch was shortened to 15% of that in free cell culture.
基金This work was supported by the National Natural Science Foundation of China(grant No.30730022)the National Basic Research Program(973 Program)(grant Nos.2006CB806503 and 2007CB914304)+1 种基金the National Programs for High Technology Research and Development Program(863 Program)(grant Nos.2006AA02A322 and 2006AA020502)the CAS(China)grant KSCX2-YW-R-05 to Z.R.
文摘Nascent polypeptide associated complex(NAC)and its two isolated subunits,αNAC and βNAC,play important roles in nascent peptide targeting.We determined a 1.9Åresolution crystal structure of the interaction core of NAC heterodimer and a 2.4Åresolution crystal structure ofαNAC NAC domain homodimer.These structures provide detailed information of NAC heterodimerization and αNAC homodimerization.We found that the NAC domains of αNAC and βNAC share very similar folding despite of their relative low identity of amino acid sequences.Furthermore,different electric charge distributions of the two subunits at the NAC interface provide an explanation to the observation that the heterodimer of NAC complex is more stable than the single subunit homodimer.In addition,we successfully built a βNAC NAC domain homodimer model based on homologous modeling,suggesting that NAC domain dimerization is a general property of the NAC family.These 3D structures allow further studies on structurefunction relationship of NAC.
基金supported by the Korean Ministry of Science,Information/Communication Technology and Future Planning(NRF-2021R1A4A1031754,NRF-2019M3E5D6066058,and NRF-2022R1F1A1068269)I.C.was funded by BK21 Plus(4120200313623)of the Ministry of Education,Korea.
文摘Plants use sophisticated mechanisms of gene expression to control senescence in response to environmental stress or aging.ORE1(Arabidopsis thaliana NAC092)is a master regulator of senescence that belongs to the plant-specific NAC transcription factor protein family.ORE1 has been reported to bind to multiple DNA targets to orchestrate leaf senescence,yet the mechanistic basis for recognition of the cognate gene sequence remains unclear.Here,we report the crystal structure of the ORE1-NAC domain alone and its DNA-binding form.The structure of DNA-bound ORE1-NAC revealed the molecular basis for nucleobase recognition and phosphate backbone interactions.We showthat local versatility in the DNA-binding site,in combination with domain flexibility of the ORE-NAC homodimer,is crucial for the maintenance of binding to intrinsically flexible DNA.Our results provide a platformfor understanding other plant-specific NAC protein-DNA interactions as well as insight into the structural basis of NAC regulators in plants of agronomic and scientific importance.
