Based on an experiment treating benzene and 2-chloroethyl ethyl sulfide （CEES） by pulse corona induced-plasma, the simiarities and differences found in the experimental data and analytical results are analyzed in a ...Based on an experiment treating benzene and 2-chloroethyl ethyl sulfide （CEES） by pulse corona induced-plasma, the simiarities and differences found in the experimental data and analytical results are analyzed in a comparative manner in this paper. The theory applied is also discussed.展开更多
Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than ten solvents were determined using both Abbe refractometer and polarized microscopy. Critical concentration C-crit of forming Liquid ...Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than ten solvents were determined using both Abbe refractometer and polarized microscopy. Critical concentration C-crit of forming Liquid crystal phase decreased with increasing solubility parameter delta of solvent until approaching the delta of polymer. Although the alcohols used as solvents had the same variation rule, the critical concentration values of their solutions were much higher, due to their excessive large hydrogen bond component of delta. The experiments of using mixed solvents which showed good linear relation between C-crit and delta also proved this rule. A technique of Transmission Optical Analysis was first used to estimate the concentration dependence of critical phase transition temperature T-crit of EC, and a T-C phase diagram could be drawn.展开更多
N-Methyl bis(2-(alkyloxy-alkylphosphoryloxy)ethyl)amines, which are abbreviated as PNPs, are a series of new skeleton chemicals belonging to schedule 2.B.04 chemicals of Chemical Weapons Convention (CWC). PNPs are imp...N-Methyl bis(2-(alkyloxy-alkylphosphoryloxy)ethyl)amines, which are abbreviated as PNPs, are a series of new skeleton chemicals belonging to schedule 2.B.04 chemicals of Chemical Weapons Convention (CWC). PNPs are important markers of chemical warfare agents because they are structurally relative to both nerve agents and N-mustards. In this study, fragmentation pathways of the most characteristic fragment ions in Q-TOF mass spectrometry were proposed based on the information from accurate mass and secondary fragmentations of product ions scan experiments. Results indicated that the base ion in LC/HRMS was the quasi-molecular ion [M+H]+. In LC-HRMS/MS, it was [M+H-CnH2n+1P(O)(OH)CmH2m+1O]+ fragment ion which was formed by losing an alkyloxy alkylphosphoryloxy group from the quasi-molecular ion. The diagnostic ion m/z84.0814 was identified as [C5H10N]+, which was the group of (CH2=CH)2N+(H)CH3. PNPs have two protonated centers. One is on the N atom, the other is on the O atom (P=O). O-n-propyl PNPs generally exhibited two fragmentation pathways. Firstly, the quasi-molecular ion [M+H]+ lost a propoxy alkylphosphoryloxy group to produce [R1P(OH+)(O-n-C3H7)OCH2CH2N(CH3)CH=CH2]+, which could be fragmented further to produce [C5H10N]+ ion. Secondly, [R1P(OH+)(O-n-C3H7) OCH=CH2]+ ions were produced from [M+H]+ and fragmented further to produce the abundant ions [R1P(OH+)(OH)OCH =CH2]. However, O-isopropyl PNPs characteristically produced weak fragment ions [M+H-C3H6]+, which were presumably formed via loss of CH3CH=CH2 from [M+H]+. Other PNPs showed similar fragmentation pathways as O-n-propyl PNPs. On the summarization of the MS fragmentation pathways of PNPs, LC-HRMS/MS quantitative and qualitative methods were developed and applied to analyze N-Methyl bis(2-(butoxy-methylphosphoryloxy)ethyl]amine in high background organic samples. The analytical results had successfully supported the sample preparation for the 33rd official proficiency test of Organization for Prohibition of Chemical Weapons (OPCW).展开更多
氨基甲酸乙酯(ethyl carbamate,EC)是泡菜发酵过程中可能产生的一类2A级致癌物质,发酵温度可通过影响微生物代谢进而影响EC的积累。研究测定了10、20、30℃条件下泡萝卜发酵过程中EC含量及其前体物质、理化指标、挥发性物质、微生物数...氨基甲酸乙酯(ethyl carbamate,EC)是泡菜发酵过程中可能产生的一类2A级致癌物质,发酵温度可通过影响微生物代谢进而影响EC的积累。研究测定了10、20、30℃条件下泡萝卜发酵过程中EC含量及其前体物质、理化指标、挥发性物质、微生物数量及结构变化。结果表明,10℃下EC含量先增加再降低,发酵3 d达到最高值79.64μg/L,且发酵7 d后仍高于联合国粮农组织(Food and Agriculture Organization of the United Nations,FAO)最高允许量(20μg/L),而20和30℃在发酵3 d后低于标准。在理化指标和挥发性物质方面,随温度增加,还原糖消耗、总酸积累以及pH降低明显加快,且10、20、30℃下泡萝卜挥发性物质呈现较大差异;在菌群结构方面,随温度增加,乳杆菌属丰度增加,而片球菌属丰度下降;Pearson相关性分析表明,Pediococcus ethanolidurans(r=0.52)和Lactobacillus nagelii(r=0.59)与EC含量呈正相关。综上,发酵温度可能通过影响乳酸菌生长及其结构进而对EC的积累有较大影响,因此适当提高温度有助于控制泡萝卜发酵过程中EC的含量。展开更多
As an important building block for the synthesis of angiotensin-converting enzyme inhibitors,ethyl(R)-2-hy-droxyl-4-phenylbutanoate[(R)-HPBE]has attracted increasing attention.The key to industrial biosynthesis of(R)-...As an important building block for the synthesis of angiotensin-converting enzyme inhibitors,ethyl(R)-2-hy-droxyl-4-phenylbutanoate[(R)-HPBE]has attracted increasing attention.The key to industrial biosynthesis of(R)-HPBE is a biocatalyst that efficiently reduces ethyl 2-oxo-4-phenylbutanoate(OPBE)with high R-enantiose-lectivity.This paper proposed a strategy for identifying key residues involved in enantioselectivity control based on per-residue free energy decomposition and sequence conservatism analysis.Using this strategy,4 noncon-servative sites with high energy contribution to binding of OPBE were chosen as engineering targets,generating variant Mu27 with 99%conversion and 98%(R)ee value at substrate loading of up to 500 mmol/L.MD simu-lations suggested the higher stability and formation probability of Mu27-OPBEproR prereaction state as key rea-sons for the excellent R-enantioselectivity of Mu27 towards OPBE.The success in this study provides a viable approach for rational design of alcohol dehydrogenases with high enantioselectivity towards unnatural substrates.展开更多
基金This project supported by the Dean's Research Foundation of the Institute of Chemical Defense
文摘Based on an experiment treating benzene and 2-chloroethyl ethyl sulfide （CEES） by pulse corona induced-plasma, the simiarities and differences found in the experimental data and analytical results are analyzed in a comparative manner in this paper. The theory applied is also discussed.
基金The project was supported by Return Student Foundation of the State Education Commission of China
文摘Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than ten solvents were determined using both Abbe refractometer and polarized microscopy. Critical concentration C-crit of forming Liquid crystal phase decreased with increasing solubility parameter delta of solvent until approaching the delta of polymer. Although the alcohols used as solvents had the same variation rule, the critical concentration values of their solutions were much higher, due to their excessive large hydrogen bond component of delta. The experiments of using mixed solvents which showed good linear relation between C-crit and delta also proved this rule. A technique of Transmission Optical Analysis was first used to estimate the concentration dependence of critical phase transition temperature T-crit of EC, and a T-C phase diagram could be drawn.
文摘N-Methyl bis(2-(alkyloxy-alkylphosphoryloxy)ethyl)amines, which are abbreviated as PNPs, are a series of new skeleton chemicals belonging to schedule 2.B.04 chemicals of Chemical Weapons Convention (CWC). PNPs are important markers of chemical warfare agents because they are structurally relative to both nerve agents and N-mustards. In this study, fragmentation pathways of the most characteristic fragment ions in Q-TOF mass spectrometry were proposed based on the information from accurate mass and secondary fragmentations of product ions scan experiments. Results indicated that the base ion in LC/HRMS was the quasi-molecular ion [M+H]+. In LC-HRMS/MS, it was [M+H-CnH2n+1P(O)(OH)CmH2m+1O]+ fragment ion which was formed by losing an alkyloxy alkylphosphoryloxy group from the quasi-molecular ion. The diagnostic ion m/z84.0814 was identified as [C5H10N]+, which was the group of (CH2=CH)2N+(H)CH3. PNPs have two protonated centers. One is on the N atom, the other is on the O atom (P=O). O-n-propyl PNPs generally exhibited two fragmentation pathways. Firstly, the quasi-molecular ion [M+H]+ lost a propoxy alkylphosphoryloxy group to produce [R1P(OH+)(O-n-C3H7)OCH2CH2N(CH3)CH=CH2]+, which could be fragmented further to produce [C5H10N]+ ion. Secondly, [R1P(OH+)(O-n-C3H7) OCH=CH2]+ ions were produced from [M+H]+ and fragmented further to produce the abundant ions [R1P(OH+)(OH)OCH =CH2]. However, O-isopropyl PNPs characteristically produced weak fragment ions [M+H-C3H6]+, which were presumably formed via loss of CH3CH=CH2 from [M+H]+. Other PNPs showed similar fragmentation pathways as O-n-propyl PNPs. On the summarization of the MS fragmentation pathways of PNPs, LC-HRMS/MS quantitative and qualitative methods were developed and applied to analyze N-Methyl bis(2-(butoxy-methylphosphoryloxy)ethyl]amine in high background organic samples. The analytical results had successfully supported the sample preparation for the 33rd official proficiency test of Organization for Prohibition of Chemical Weapons (OPCW).
文摘氨基甲酸乙酯(ethyl carbamate,EC)是泡菜发酵过程中可能产生的一类2A级致癌物质,发酵温度可通过影响微生物代谢进而影响EC的积累。研究测定了10、20、30℃条件下泡萝卜发酵过程中EC含量及其前体物质、理化指标、挥发性物质、微生物数量及结构变化。结果表明,10℃下EC含量先增加再降低,发酵3 d达到最高值79.64μg/L,且发酵7 d后仍高于联合国粮农组织(Food and Agriculture Organization of the United Nations,FAO)最高允许量(20μg/L),而20和30℃在发酵3 d后低于标准。在理化指标和挥发性物质方面,随温度增加,还原糖消耗、总酸积累以及pH降低明显加快,且10、20、30℃下泡萝卜挥发性物质呈现较大差异;在菌群结构方面,随温度增加,乳杆菌属丰度增加,而片球菌属丰度下降;Pearson相关性分析表明,Pediococcus ethanolidurans(r=0.52)和Lactobacillus nagelii(r=0.59)与EC含量呈正相关。综上,发酵温度可能通过影响乳酸菌生长及其结构进而对EC的积累有较大影响,因此适当提高温度有助于控制泡萝卜发酵过程中EC的含量。
基金This study is financially supported by the National Key Research and Development Program of China(No.2018YFA0901800 to H.Yu and L.Ye)Zhejiang Provincial Natural Science Foundation of China(No.LY18B060001 to L.Ye and No.LZ20B060002 to H.Yu)Natural Science Foundation of China(No.21776244 to H.Yu).We are grateful to the constructive suggestions from academician Fen-Er Chen(Department of Chemistry,Fudan University,Shanghai,China)and the support of Discovery Studio software from Fuzhou University platform.
文摘As an important building block for the synthesis of angiotensin-converting enzyme inhibitors,ethyl(R)-2-hy-droxyl-4-phenylbutanoate[(R)-HPBE]has attracted increasing attention.The key to industrial biosynthesis of(R)-HPBE is a biocatalyst that efficiently reduces ethyl 2-oxo-4-phenylbutanoate(OPBE)with high R-enantiose-lectivity.This paper proposed a strategy for identifying key residues involved in enantioselectivity control based on per-residue free energy decomposition and sequence conservatism analysis.Using this strategy,4 noncon-servative sites with high energy contribution to binding of OPBE were chosen as engineering targets,generating variant Mu27 with 99%conversion and 98%(R)ee value at substrate loading of up to 500 mmol/L.MD simu-lations suggested the higher stability and formation probability of Mu27-OPBEproR prereaction state as key rea-sons for the excellent R-enantioselectivity of Mu27 towards OPBE.The success in this study provides a viable approach for rational design of alcohol dehydrogenases with high enantioselectivity towards unnatural substrates.
