R ) and ( S ) (2 benzyloxyethyl)oxirane 1 were prepared from ( S ) and ( R ) aspartic acid by modification of the procedure described by Rapoport. Aspartic acid was converted into bromosuccinic acid 2 by treatment wit...R ) and ( S ) (2 benzyloxyethyl)oxirane 1 were prepared from ( S ) and ( R ) aspartic acid by modification of the procedure described by Rapoport. Aspartic acid was converted into bromosuccinic acid 2 by treatment with sodium nitrite/potassium bromide/sulfuric acid,the diacid 2 was then reduced with freshly prepared boron trifluoride ethyl ether complex to bromodiol 3, which was further treated with sodium hydride and benzylbromide/TBAI(tetrabutylammonium iodide) to afford (2 benzyloxyethyl)oxirane. This procedure has shown the good yield, mild condition and excellent enantiomeric purity of the product.展开更多
Methyl 3-hydroxypropanoate was synthesized via hydroesterification of ethylene oxide with CO in the presence of dicobalt octacarbonyl catalyst and methanol solvent. The catalyst exhibited high catalytic activity. The ...Methyl 3-hydroxypropanoate was synthesized via hydroesterification of ethylene oxide with CO in the presence of dicobalt octacarbonyl catalyst and methanol solvent. The catalyst exhibited high catalytic activity. The effect of reaction temperature, CO pressure, methanol dosage, catalyst dosage and reaction time on catalytic reaction was investigated. The test results revealed that this reaction was greatly affected by reaction temperature, but it was not significantly affected by the CO pressure, the methanol dosage, the catalyst dosage and the reaction time. Under the optimal conditions, the conversion of ethylene oxide was equal to 92.24%, while the selectivity and yield of methyl 3-hydroxypropanoate reached 88.99% and 84.35%, respectively.展开更多
In this paper, poly(amide-6-β-ethylene oxide) (PEBA1657) copolymer was used to prepare multilayer polyetherimide (PEI)/polydimethylsiloxane (PDMS)/PEBA1657/PDMS composite membranes by dip-coating method. Permeation b...In this paper, poly(amide-6-β-ethylene oxide) (PEBA1657) copolymer was used to prepare multilayer polyetherimide (PEI)/polydimethylsiloxane (PDMS)/PEBA1657/PDMS composite membranes by dip-coating method. Permeation behaviors of ethylene, ethane, propylene, propane, n-butane, methane and nitrogen through the multilayer composite membranes were investigated over a range of operating temperature and pressure. The permeances of light hydrocarbons through PEI/PDMS/PEBA1657/PDMS composite membranes increase with their increasing condensability, and the olefins are more permeable than their corresponding paraffins. For light hydrocarbons, the gas permeances increase significantly as temperature increasing. When the transmembrane pressure difference increases, the gas permeance increases moderately due to plasticization effect, while their apparent activation energies for permeation decrease.展开更多
Objective:This study aimed to clone and characterize the oxiranedicarboxylate hydrolase(ORCH) from Labrys sp.WH-1.Methods:Purification by column chromatography,characterization of enzymatic properties,gene cloning by ...Objective:This study aimed to clone and characterize the oxiranedicarboxylate hydrolase(ORCH) from Labrys sp.WH-1.Methods:Purification by column chromatography,characterization of enzymatic properties,gene cloning by protein terminal sequencing and polymerase chain reaction(PCR),and sequence analysis by secondary structure prediction and multiple sequence alignment were performed.Results:The ORCH from Labrys sp.WH-1 was purified 26-fold with a yield of 12.7%.It is a monomer with an isoelectric point(pl) of 8.57 and molecular mass of 30.2 kDa.It was stable up to 55℃with temperature at which the activity of the enzyme decreased by 50% in 15 min(T5015) of 61℃and the half-life at 50℃(t1/2,50℃) of 51 min and was also stable from pH 4 to 10,with maximum activity at 55℃and pH 8.5.It is a metal-independent enzyme and strongly inhibited by Cu2+,Ag+,and anionic surfactants.Its kinetic parameters(Km,kcat,and kcat/Km) were 18.7 mmol/L,222.3 s-1,and 11.9 mmol/(L s),respectively.The ORCH gene,which contained an open reading frame(ORF) of 825 bp encoding 274 amino acid residues,was overexpressed in Escherichia coli and the enzyme activity was 33 times higher than that of the wild strain.Conclusions The catalytic efficiency and thermal stability of the ORCH from Labrys sp.WH-1 were the best among the reported ORCHs,and it provides an alternative catalyst for preparation of L(+)-2,3-dihydrobutanedioic acid.展开更多
文摘R ) and ( S ) (2 benzyloxyethyl)oxirane 1 were prepared from ( S ) and ( R ) aspartic acid by modification of the procedure described by Rapoport. Aspartic acid was converted into bromosuccinic acid 2 by treatment with sodium nitrite/potassium bromide/sulfuric acid,the diacid 2 was then reduced with freshly prepared boron trifluoride ethyl ether complex to bromodiol 3, which was further treated with sodium hydride and benzylbromide/TBAI(tetrabutylammonium iodide) to afford (2 benzyloxyethyl)oxirane. This procedure has shown the good yield, mild condition and excellent enantiomeric purity of the product.
基金supported by the Guangdong Province Natural Science Foundation (No. 10152500002000019)the Maoming City Science and Technology Planning Project (NO.2008024)
文摘Methyl 3-hydroxypropanoate was synthesized via hydroesterification of ethylene oxide with CO in the presence of dicobalt octacarbonyl catalyst and methanol solvent. The catalyst exhibited high catalytic activity. The effect of reaction temperature, CO pressure, methanol dosage, catalyst dosage and reaction time on catalytic reaction was investigated. The test results revealed that this reaction was greatly affected by reaction temperature, but it was not significantly affected by the CO pressure, the methanol dosage, the catalyst dosage and the reaction time. Under the optimal conditions, the conversion of ethylene oxide was equal to 92.24%, while the selectivity and yield of methyl 3-hydroxypropanoate reached 88.99% and 84.35%, respectively.
基金Supported by Key Projects in the National Science & Technology Pillar Program (2011BAC08B00)
文摘In this paper, poly(amide-6-β-ethylene oxide) (PEBA1657) copolymer was used to prepare multilayer polyetherimide (PEI)/polydimethylsiloxane (PDMS)/PEBA1657/PDMS composite membranes by dip-coating method. Permeation behaviors of ethylene, ethane, propylene, propane, n-butane, methane and nitrogen through the multilayer composite membranes were investigated over a range of operating temperature and pressure. The permeances of light hydrocarbons through PEI/PDMS/PEBA1657/PDMS composite membranes increase with their increasing condensability, and the olefins are more permeable than their corresponding paraffins. For light hydrocarbons, the gas permeances increase significantly as temperature increasing. When the transmembrane pressure difference increases, the gas permeance increases moderately due to plasticization effect, while their apparent activation energies for permeation decrease.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(No.LQ19C200001)the Education Department of Zhejiang Province Scientific Research Project(No.Y201737925)+1 种基金the Zhejiang Provincial Key Laboratory for Chemical and Biological Processing Technology of Farm Products(No.2016KF0048)the Key Laboratory of Bioorganic Synthesis of Zhejiang Province(No.20170110),China
文摘Objective:This study aimed to clone and characterize the oxiranedicarboxylate hydrolase(ORCH) from Labrys sp.WH-1.Methods:Purification by column chromatography,characterization of enzymatic properties,gene cloning by protein terminal sequencing and polymerase chain reaction(PCR),and sequence analysis by secondary structure prediction and multiple sequence alignment were performed.Results:The ORCH from Labrys sp.WH-1 was purified 26-fold with a yield of 12.7%.It is a monomer with an isoelectric point(pl) of 8.57 and molecular mass of 30.2 kDa.It was stable up to 55℃with temperature at which the activity of the enzyme decreased by 50% in 15 min(T5015) of 61℃and the half-life at 50℃(t1/2,50℃) of 51 min and was also stable from pH 4 to 10,with maximum activity at 55℃and pH 8.5.It is a metal-independent enzyme and strongly inhibited by Cu2+,Ag+,and anionic surfactants.Its kinetic parameters(Km,kcat,and kcat/Km) were 18.7 mmol/L,222.3 s-1,and 11.9 mmol/(L s),respectively.The ORCH gene,which contained an open reading frame(ORF) of 825 bp encoding 274 amino acid residues,was overexpressed in Escherichia coli and the enzyme activity was 33 times higher than that of the wild strain.Conclusions The catalytic efficiency and thermal stability of the ORCH from Labrys sp.WH-1 were the best among the reported ORCHs,and it provides an alternative catalyst for preparation of L(+)-2,3-dihydrobutanedioic acid.
