Taxadiene synthase, a diterpene cyclase, catalyzes the conversion of geranylgeranyl diphosphate (GGPP) to taxadiene, a key intermediate in Taxol biosynthesis in yew. A 2 151 bp cDNA fragment encoding taxadiene synthas...Taxadiene synthase, a diterpene cyclase, catalyzes the conversion of geranylgeranyl diphosphate (GGPP) to taxadiene, a key intermediate in Taxol biosynthesis in yew. A 2 151 bp cDNA fragment encoding taxadiene synthase of Taxus chinensis (Pilg.) Rehd. was cloned by homology-based PCR and cDNA library screening. The 5′-terminal 611 bp cDNA fragment of taxadiene synthase was isolated by PCR. The two fragments were ligated together and gave a 2*!712 bp cDNA fragment with a 2*!586 bp open reading frame (ORF), encoding 862 amino acid residues including a presumptive plastidial transit peptide. The taxadiene synthase of T. chinensis most closely resembles the one from T. brevifolia (97% identity). Heterologous overexpression of 2.5 kb cDNA fragment from T. chinensis was obtained using a fusion expression vector pET-32a and the Escherichia coli strain BL21trxB. The expressed proteins from E. coli BL21trxB were present as inclusion bodies. After the inclusion bodies were denatured, renatured and refolded, the recombinant enzyme was purified by a single step with a His-binding metal affinity column. The catalytic product of taxadiene synthase of T. chinensis was detected by capillary gas chromatography-mass spectrometry (GC-MS) and identified as taxa-4(5),11(12)-diene.展开更多
A high taxol yield cell line of Taxus yunnanensis Cheng et L. K. Fu keeps a high taxol_producing level after successive subcultures for more than eight years. In this study, eight taxanes were isolated from the su...A high taxol yield cell line of Taxus yunnanensis Cheng et L. K. Fu keeps a high taxol_producing level after successive subcultures for more than eight years. In this study, eight taxanes were isolated from the suspension cell cultures of this cell line. Based on NMR and MS analyses, and comparison with literature data and standards, their structures were determined to be 2α,5α,10β_triacetoxy_14β_propionyloxy_4(20),11_taxadiene (1), 2α,5α,10β_triacetoxy_14β_(2′_methyl)_butyryloxy_4(20),11_taxadiene (2), 2α,5α,10β_14β_tetra_acetoxy_4 (20),11_taxadiene (3, taxuyunnanine C), 2α,5α,10β_triacetoxy_14β_(2′_methyl_3′_hydroxy)_butyryloxy_4(20),11_taxadiene (4, yunnanxane) and its 3′_epimer (5), baccatin Ⅳ (6), baccatin Ⅲ (7) and taxol (8), respectively. Among those compounds, 3, 5, 6 and 7 were reported to be isolated from the suspension cell cultures of T. yunnanensis for the first time. TLC and HPLC analyses indicated that the chemical constituents of the culture solution were similar to those of cultured cells. Moreover, the highest taxol content of this cell line reached 0.3% and the cell line could be applied for a large_scale culture.展开更多
Highly dispersed tungsten carbide（WC） nanoparticles（NPs） sandwiched between few-layer reduced graphene oxide（RGO） have been successfully synthesized by using thiourea as an anchoring and inducing reagent.The met...Highly dispersed tungsten carbide（WC） nanoparticles（NPs） sandwiched between few-layer reduced graphene oxide（RGO） have been successfully synthesized by using thiourea as an anchoring and inducing reagent.The metatungstate ion,[H2W（12）O（40）]^6-,is assembled on thiourea-modified graphene oxide（GO） by an impregnation method.The WC NPs,with a mean diameter of 1.5 nm,are obtained through a process whereby ammonium metatungstate first turns to WS2,which then forms an intercalation compound with RGO before growing,in situ,to WC NPs.The Pt/WC-RGO electrocatalysts are fabricated by a microwave-assisted method.The intimate contacts between Pt,WC,and RGO are confirmed by X-ray diffraction,scanning electron microscope,transmission electron microscope,and Raman spectroscopy.For methanol oxidation,the Pt/WC-RGO electrocatalyst exhibited an electrochemical surface area value of 246.1 m^2/g Pt and a peak current density of1364.7 mA/mg Pt,which are,respectively,3.66 and 4.77 times greater than those of commercial Pt/C electrocatalyst（67.2 m^2/g Pt,286.0 mA/mg Pt）.The excellent CO-poisoning resistance and long-term stability of the electrocatalyst are also evidenced by CO stripping,chronoamperometry,and accelerated durability testing.Because Pt/WC-RGO has higher catalytic activity compared with that of commercial Pt/C,as a result of its intercalated structure and synergistic effect,less Pt will be required for the same performance,which in turn will reduce the cost of the fuel cell.The present method is facile,efficient,and scalable for mass production of the nanomaterials.展开更多
Aim Isolation and structural elucidation of the constituents from the aerialpart of Hypericum perforatum L. Methods Column chromatography and TLC were used to isolate chemicalconstituents. Physico-chemical characteriz...Aim Isolation and structural elucidation of the constituents from the aerialpart of Hypericum perforatum L. Methods Column chromatography and TLC were used to isolate chemicalconstituents. Physico-chemical characterization and spectroscopic analysis were employed forstructural identification. Results Three flavonols were isolated and identified. Conclusion Compound1 is a novel natural product and its structure has been characterized to be 3, 5, 7-trihydroxy-3',4'-isopropyldioxy-flavone.展开更多
A series of bifunctional catalysts composed of a component for higher alcohol synthesis （Cu-CoMn oxides, CCM） and an acidic zeolite （SAPO-34, ZSM-5, Y, MCM-41） were prepared for production of liquid hydrocarbon di...A series of bifunctional catalysts composed of a component for higher alcohol synthesis （Cu-CoMn oxides, CCM） and an acidic zeolite （SAPO-34, ZSM-5, Y, MCM-41） were prepared for production of liquid hydrocarbon directly from a bio-syngas through a one-stage pro-cess. The effects of zeolite type, zeolite content, Si/Al ratio and preparation method on catalyst texture and its reaction performance were investigated. Higher selectivities and yields of liquid products were obtained by using bifunctional catalysts. The yields of liquid hydrocarbons decreased in the order CCM-ZSM-5〉CCM-SAPO-34〉CCM-Y〉CCM-MCM-41. CCM-ZSM-5 （20wt%, Si/Al=100） prepared by coprecipitation method displayed the optimal catalytic performance with the highest CO conversion （76%） and yield of liquid products （30%）. The catalysts were characterized by N2 adsorption/desorption, NH3-TPD, XRD, and H2-TPR analysis. The results showed that higher speci c surface areas and pore volumes of bifunctional catalysts were achieved by adding zeolites into CuCoMn precursors. Medium pore dimension and moderate acidity in CCM-ZSM-5 were observed, which proba-bly resulted in its excellent reaction performance. Additionally, a higher number of weaker acid sites （weak and/or medium acid sites） were formed by increasing ZSM-5 content in CCM-ZSM-5 or decreasing Si/Al ratio in ZSM-5. It was also seen that metal dispersion was higher and reducibility of metal ions was easier on the CCM-ZSM-5 catalyst prepared by coprecipitation. The higher alcohols-to-hydrocarbon process provides a promising route to hydrocarbon fuels via higher alcohols from syngas or biobased feedstocks.展开更多
A dual-reactor, assembled with the on-line syngas conditioning and methanol synthesis, was successfully applied for high efficient conversion of rich CO2 bio-oil derived syngas to bio-methanol. In the forepart catalys...A dual-reactor, assembled with the on-line syngas conditioning and methanol synthesis, was successfully applied for high efficient conversion of rich CO2 bio-oil derived syngas to bio-methanol. In the forepart catalyst bed reactor, the catalytic conversion can effectively adjust the rich-CO2 crude bio-syngas into the CO-containing bio-syngas using the CuZnA1Zr catalyst. After the on-line syngas conditioning at 450℃, the CO2/CO ratio in the blo- syngas significantly decreased from 6.3 to 1.2. In the rearward catalyst bed reactor, the conversion of the conditioned bio-syngas to bio-methanol shows the maximum yield about 1.21 kg/（kgcatarh） MeOH with a methanol selectivity of 97.9% at 260 ~C and 5.05 MPa using conventional CuZnA1 catalyst, which is close to the level typically obtained in the conventional methanol synthesis process using natural gas. The influences of temperature, pressure and space velocity on the bio-methanol synthesis were also investigated in detail.展开更多
The rules on regulating aromatic compounds production was investigated by aqueous cat- alytic reforming of sorbitol. It was found that aromatics, ketones, furans, organic acids were main compounds in organic phase. Th...The rules on regulating aromatic compounds production was investigated by aqueous cat- alytic reforming of sorbitol. It was found that aromatics, ketones, furans, organic acids were main compounds in organic phase. The obvious effect of metal content showed that the highest carbon selectivity of aromatics was 34.36% when 3wt% Ni content was loaded on HZSM-5 zeolite modified by MCM-41. However, it was decreased only to 4.82% when Ni content was improved to 20wt%. Meanwhile, different reaction parameters also displayed important impacts on carbon selectivity. It was improved with the increase of temperature, while it was decreased as liquid hourly space velocity and hydrogen pressure was increased. The results showed that appropriate higher temperature, longer contact time and lower hy- drogen pressure were in favor of aromatics information, which suggested a feasible process to solve energy crisis.展开更多
new aristolane sesquiterpenoid named rulepidol was isolated from the fruiting body of Russula lepida Fr. Its structure was elucidated as (1a alpha ,5 alpha ,7 alpha ,7a alpha, 7b alpha)-1, 1a,4,5,6,7,7a, 7b-octahydro-...new aristolane sesquiterpenoid named rulepidol was isolated from the fruiting body of Russula lepida Fr. Its structure was elucidated as (1a alpha ,5 alpha ,7 alpha ,7a alpha, 7b alpha)-1, 1a,4,5,6,7,7a, 7b-octahydro-5-hydroxy-1,1,7,7a-tetramethyl-5H-cyclopropa [alpha] naphthalen-2-one mainly by 1D and 2D-NMR techniques.展开更多
文摘Taxadiene synthase, a diterpene cyclase, catalyzes the conversion of geranylgeranyl diphosphate (GGPP) to taxadiene, a key intermediate in Taxol biosynthesis in yew. A 2 151 bp cDNA fragment encoding taxadiene synthase of Taxus chinensis (Pilg.) Rehd. was cloned by homology-based PCR and cDNA library screening. The 5′-terminal 611 bp cDNA fragment of taxadiene synthase was isolated by PCR. The two fragments were ligated together and gave a 2*!712 bp cDNA fragment with a 2*!586 bp open reading frame (ORF), encoding 862 amino acid residues including a presumptive plastidial transit peptide. The taxadiene synthase of T. chinensis most closely resembles the one from T. brevifolia (97% identity). Heterologous overexpression of 2.5 kb cDNA fragment from T. chinensis was obtained using a fusion expression vector pET-32a and the Escherichia coli strain BL21trxB. The expressed proteins from E. coli BL21trxB were present as inclusion bodies. After the inclusion bodies were denatured, renatured and refolded, the recombinant enzyme was purified by a single step with a His-binding metal affinity column. The catalytic product of taxadiene synthase of T. chinensis was detected by capillary gas chromatography-mass spectrometry (GC-MS) and identified as taxa-4(5),11(12)-diene.
文摘A high taxol yield cell line of Taxus yunnanensis Cheng et L. K. Fu keeps a high taxol_producing level after successive subcultures for more than eight years. In this study, eight taxanes were isolated from the suspension cell cultures of this cell line. Based on NMR and MS analyses, and comparison with literature data and standards, their structures were determined to be 2α,5α,10β_triacetoxy_14β_propionyloxy_4(20),11_taxadiene (1), 2α,5α,10β_triacetoxy_14β_(2′_methyl)_butyryloxy_4(20),11_taxadiene (2), 2α,5α,10β_14β_tetra_acetoxy_4 (20),11_taxadiene (3, taxuyunnanine C), 2α,5α,10β_triacetoxy_14β_(2′_methyl_3′_hydroxy)_butyryloxy_4(20),11_taxadiene (4, yunnanxane) and its 3′_epimer (5), baccatin Ⅳ (6), baccatin Ⅲ (7) and taxol (8), respectively. Among those compounds, 3, 5, 6 and 7 were reported to be isolated from the suspension cell cultures of T. yunnanensis for the first time. TLC and HPLC analyses indicated that the chemical constituents of the culture solution were similar to those of cultured cells. Moreover, the highest taxol content of this cell line reached 0.3% and the cell line could be applied for a large_scale culture.
基金supported by the International Science & Technology Cooperation Program of China(2010DFB63680)the National Natural Science Foundation of China(21376220)Zhejiang Provincial Natural Science Foundation of China(LY16B060009,LY12B03008)~~
文摘Highly dispersed tungsten carbide（WC） nanoparticles（NPs） sandwiched between few-layer reduced graphene oxide（RGO） have been successfully synthesized by using thiourea as an anchoring and inducing reagent.The metatungstate ion,[H2W（12）O（40）]^6-,is assembled on thiourea-modified graphene oxide（GO） by an impregnation method.The WC NPs,with a mean diameter of 1.5 nm,are obtained through a process whereby ammonium metatungstate first turns to WS2,which then forms an intercalation compound with RGO before growing,in situ,to WC NPs.The Pt/WC-RGO electrocatalysts are fabricated by a microwave-assisted method.The intimate contacts between Pt,WC,and RGO are confirmed by X-ray diffraction,scanning electron microscope,transmission electron microscope,and Raman spectroscopy.For methanol oxidation,the Pt/WC-RGO electrocatalyst exhibited an electrochemical surface area value of 246.1 m^2/g Pt and a peak current density of1364.7 mA/mg Pt,which are,respectively,3.66 and 4.77 times greater than those of commercial Pt/C electrocatalyst（67.2 m^2/g Pt,286.0 mA/mg Pt）.The excellent CO-poisoning resistance and long-term stability of the electrocatalyst are also evidenced by CO stripping,chronoamperometry,and accelerated durability testing.Because Pt/WC-RGO has higher catalytic activity compared with that of commercial Pt/C,as a result of its intercalated structure and synergistic effect,less Pt will be required for the same performance,which in turn will reduce the cost of the fuel cell.The present method is facile,efficient,and scalable for mass production of the nanomaterials.
文摘Aim Isolation and structural elucidation of the constituents from the aerialpart of Hypericum perforatum L. Methods Column chromatography and TLC were used to isolate chemicalconstituents. Physico-chemical characterization and spectroscopic analysis were employed forstructural identification. Results Three flavonols were isolated and identified. Conclusion Compound1 is a novel natural product and its structure has been characterized to be 3, 5, 7-trihydroxy-3',4'-isopropyldioxy-flavone.
文摘A series of bifunctional catalysts composed of a component for higher alcohol synthesis （Cu-CoMn oxides, CCM） and an acidic zeolite （SAPO-34, ZSM-5, Y, MCM-41） were prepared for production of liquid hydrocarbon directly from a bio-syngas through a one-stage pro-cess. The effects of zeolite type, zeolite content, Si/Al ratio and preparation method on catalyst texture and its reaction performance were investigated. Higher selectivities and yields of liquid products were obtained by using bifunctional catalysts. The yields of liquid hydrocarbons decreased in the order CCM-ZSM-5〉CCM-SAPO-34〉CCM-Y〉CCM-MCM-41. CCM-ZSM-5 （20wt%, Si/Al=100） prepared by coprecipitation method displayed the optimal catalytic performance with the highest CO conversion （76%） and yield of liquid products （30%）. The catalysts were characterized by N2 adsorption/desorption, NH3-TPD, XRD, and H2-TPR analysis. The results showed that higher speci c surface areas and pore volumes of bifunctional catalysts were achieved by adding zeolites into CuCoMn precursors. Medium pore dimension and moderate acidity in CCM-ZSM-5 were observed, which proba-bly resulted in its excellent reaction performance. Additionally, a higher number of weaker acid sites （weak and/or medium acid sites） were formed by increasing ZSM-5 content in CCM-ZSM-5 or decreasing Si/Al ratio in ZSM-5. It was also seen that metal dispersion was higher and reducibility of metal ions was easier on the CCM-ZSM-5 catalyst prepared by coprecipitation. The higher alcohols-to-hydrocarbon process provides a promising route to hydrocarbon fuels via higher alcohols from syngas or biobased feedstocks.
基金This work was supported by the National High Tech Research and Development Program （No.2009AA05Z435）, the National Basic Research Program of Ministry of Science and Technology of China （No.2007CB210206）, and the National Natural Science Foundation of China （No.50772107）.
文摘A dual-reactor, assembled with the on-line syngas conditioning and methanol synthesis, was successfully applied for high efficient conversion of rich CO2 bio-oil derived syngas to bio-methanol. In the forepart catalyst bed reactor, the catalytic conversion can effectively adjust the rich-CO2 crude bio-syngas into the CO-containing bio-syngas using the CuZnA1Zr catalyst. After the on-line syngas conditioning at 450℃, the CO2/CO ratio in the blo- syngas significantly decreased from 6.3 to 1.2. In the rearward catalyst bed reactor, the conversion of the conditioned bio-syngas to bio-methanol shows the maximum yield about 1.21 kg/（kgcatarh） MeOH with a methanol selectivity of 97.9% at 260 ~C and 5.05 MPa using conventional CuZnA1 catalyst, which is close to the level typically obtained in the conventional methanol synthesis process using natural gas. The influences of temperature, pressure and space velocity on the bio-methanol synthesis were also investigated in detail.
文摘The rules on regulating aromatic compounds production was investigated by aqueous cat- alytic reforming of sorbitol. It was found that aromatics, ketones, furans, organic acids were main compounds in organic phase. The obvious effect of metal content showed that the highest carbon selectivity of aromatics was 34.36% when 3wt% Ni content was loaded on HZSM-5 zeolite modified by MCM-41. However, it was decreased only to 4.82% when Ni content was improved to 20wt%. Meanwhile, different reaction parameters also displayed important impacts on carbon selectivity. It was improved with the increase of temperature, while it was decreased as liquid hourly space velocity and hydrogen pressure was increased. The results showed that appropriate higher temperature, longer contact time and lower hy- drogen pressure were in favor of aromatics information, which suggested a feasible process to solve energy crisis.
文摘new aristolane sesquiterpenoid named rulepidol was isolated from the fruiting body of Russula lepida Fr. Its structure was elucidated as (1a alpha ,5 alpha ,7 alpha ,7a alpha, 7b alpha)-1, 1a,4,5,6,7,7a, 7b-octahydro-5-hydroxy-1,1,7,7a-tetramethyl-5H-cyclopropa [alpha] naphthalen-2-one mainly by 1D and 2D-NMR techniques.
