Organic acid content is one of the most important factors influencing fruit flavors.The predominant organic acid in most pear cultivars is malic acid,but the mechanism controlling its accumulation remains unclear.In t...Organic acid content is one of the most important factors influencing fruit flavors.The predominant organic acid in most pear cultivars is malic acid,but the mechanism controlling its accumulation remains unclear.In this study,by comparing gene expression levels and organic acid contents,we found that the expression of PbPH5,which encodes a P_(3A)-ATPase,is highly correlated with malic acid accumulation in four different pear species,with correlation coefficients of 0.932**,0.656*,0.900**,and 0.518*(*,P<0.05;**,P<0.01)for Pyrus bretschneideri Rehd.,P.communis Linn.,P.pyrifolia Nakai.,and P.ussuriensis Maxim.,respectively.Moreover,the overexpression of PbPH5 in pear significantly increased the malic acid content.In contrast,silencing PbPH5 via RNA interference significantly decreased both its transcript level and the pear fruit malic acid content.A subcellular localization analysis indicated that PbPH5 is located in the tonoplast.Additionally,a phylogenetic analysis indicated that PbPH5 is a PH5 homolog gene that is clustered with the Petunia hybrida,Malus domestica,and Citrus reticulata genes.Considered together,these findings suggest that PbPH5 is a functionally conserved gene.Furthermore,the accumulation of malic acid in pear fruit is at least partly related to changes in the PbPH5 transcription levels.展开更多
A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated.The method is based on adding malic acid into classical Belousov-Zhabotinskii(B-Z)oscillating chemical system to form ...A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated.The method is based on adding malic acid into classical Belousov-Zhabotinskii(B-Z)oscillating chemical system to form a double substrate one.The results showed that when the concentration of cobalt ion was in the range of 5.27×10^(-8)to 5.37×10^(-12)mol L^(-1),the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration.The sensitivity and precision of the developed method were quite satisfactory.The limit of detection was down to 5.20×10^(-13)tool L^(-1)which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far.Some factors influencing the determination were also examined.The method has been successfully used to determine cobalt ion in vitamin Bl2 injection.展开更多
The catalyst preparation strategy was based on a strict introduction sequence of rhenium and platinum precursors and their strong interaction with carbon support resulted in the formation of 0.5 nm Pt-Re Ox species of...The catalyst preparation strategy was based on a strict introduction sequence of rhenium and platinum precursors and their strong interaction with carbon support resulted in the formation of 0.5 nm Pt-Re Ox species of atomic dispersion, where platinum is metallic, while monolayer rhenium is partially oxidized(Re2+). The reaction kinetics was studied taking into account the process of L-malic acid association leading to the formation of inactive cyclic oligomeric species. High TOFs(ca. 50 h-1), selectivities(ca. 99%)and stability of Pt-Re Ox/C catalysts in aqueous-phase hydrogenation of L-malic acid, which are close to those of the homogeneous pincer type complexes, were revealed at mild conditions(T = 90–130 °C). Taking into account that(i) hydrogenation reaction occurred 2–3 orders of magnitude faster than its racemization and(ii) association of L-malic acid dominates at low temperatures and in a concentrated solution,special reaction conditions that allow obtaining chemically and optically(ee > 99%) pure(S)-3-hydroxy-γ-butyrolactone and(S)-1,2,4-butanetriol were found. Basing on HAADF-STEM, EDX, XPS, and kinetic studies, the structure of active species and basic reaction pathways are proposed.展开更多
Terpolymer of 1, 8-octanediol, adipic acid, and L-malic acid was synthesized via a lipase-catalyzed direct polycondensation. The products were characterized by GPC and 1H NMR. The results indicated that the molecular ...Terpolymer of 1, 8-octanediol, adipic acid, and L-malic acid was synthesized via a lipase-catalyzed direct polycondensation. The products were characterized by GPC and 1H NMR. The results indicated that the molecular weight of the prepared polymers decreased with increasing L-malic acid content in the monomer feed ratio, and that change in the L-malic acid content from 0 to 20 mol % did not remarkably influenced on the molecular weight distribution Mw /Mn of the prepared samples. The 1H NMR spectra of the obtained copolymer samples showed that hydroxyl groups of L-malic acid did not take part in the polymerization reaction.展开更多
A synthesis of methyl 2-hydroxy-4-oxo-4-(substituted phenyl)butanoates has been accomplished using Friedel-Crafts acylation of substituted benzenes with 2-acetoxybutanoyl chloride.The key feature of this strategy is t...A synthesis of methyl 2-hydroxy-4-oxo-4-(substituted phenyl)butanoates has been accomplished using Friedel-Crafts acylation of substituted benzenes with 2-acetoxybutanoyl chloride.The key feature of this strategy is that various 4-arylbutanoates can be obtained conveniently,which are important intermediates for the synthesis of biologically active compounds including ACE inhibitors.展开更多
In order to create a functionalized biodegradable polymer for vascular tissue engineering application,poly(DL- lactide-co-RS-β-malic acid)(PDLLMAc)was synthesized.PDLLMAc was obtained after hydrogenolysis of poly(DL-...In order to create a functionalized biodegradable polymer for vascular tissue engineering application,poly(DL- lactide-co-RS-β-malic acid)(PDLLMAc)was synthesized.PDLLMAc was obtained after hydrogenolysis of poly(DL- lactide-co-RS-β-benzyl malolactonate)(PDLLMA),which was from the ring-opening polymerization of DL-lactide(DLLA) and RS-β-benzyl malolactonate(MA)using stannous octoate as catalyst.The copolymers were characterized by ~1H-NMR, FTIR,GPC and DSC.The tensile strength and water uptake of the cop...展开更多
Extraction equilibrium features of succinic acid,malic acid,maleic acid and fumaric acid were investigated systematically with trioctylamine (TOA) in chloroform,4-methyl-2-pentanone (MIBK) and 1-octanol.Fourier transf...Extraction equilibrium features of succinic acid,malic acid,maleic acid and fumaric acid were investigated systematically with trioctylamine (TOA) in chloroform,4-methyl-2-pentanone (MIBK) and 1-octanol.Fourier transform-infrared(FTIR) spectroscopic analysis of organic samples loaded with the acid show that amine forms 1:1 complex of ion-pair association with succinic acid,malic acid and maleic acid,and 1:1,2:1 complex of ion-pair association with fumaric acid.It is proposed that the complex forms depend on the second dissociation constant of the dibasic acid,pKa2.Results of equilibrium experiments show that diluents affects extraction behavior,and depend on the solute concentration.Protic diluents,chloroform and 1-octanol,are more effective than the others when the equilibrium solute concentration.Protic diluents,chloroform and 1-octanol,are more effective tthan the others when the equilibrium solute concentration is lower than 1:1 stoichiometry of TOA to acid,otherwise the extraction ability shows that MIBK>1-octanol>chloroform for malic and maleic acids,and 1-octanol>MIBK>chloroform for succinic acid.Overloading(Solute concentration in organic phase is lager than TOA concentration) appears for all of the studied acids, and the sequence of overloading amount is the same as that of distribution constant of diluent.The results show that the sequence of extraction ability of different acid is the same as that of acidity at low equilibrium solute concentrations,while it is the same as the sequence of hydrophobicity at high equilibrium concentrations.展开更多
Crystals of the chiral malic acid hydrate (C 4H 6O 5·H 2O) were unexpectedly obtained from an ethanol/water solution containing racemic D,L-malic acid and L-asparagine. The crystal belongs to orthorhombic space g...Crystals of the chiral malic acid hydrate (C 4H 6O 5·H 2O) were unexpectedly obtained from an ethanol/water solution containing racemic D,L-malic acid and L-asparagine. The crystal belongs to orthorhombic space group P2 12 12 1 with cell dimensions of a=0.5576(1), b=0.9818(2), c=1.1793(2) nm, V=0.6455(2) nm 3, Z=4, μ(Mo K α)=0.152 mm -1, F(000)=320, D c=1.565 g·cm -3, R=0.051, wR=0.136 for 657 observed reflections . The significant difference in bond distances for carboxyl groups suggests that the crystal consist of malate anion and protonized crystalline water. This is a report for direct separation of racemic mixture, i.e., without the formation of a molecular complex of raceme with a chiral separating reagent.展开更多
基金funded by the National Key Research and Development Program of China (2019YFD1001400)the National Natural Science Foundation of China (31601715)
文摘Organic acid content is one of the most important factors influencing fruit flavors.The predominant organic acid in most pear cultivars is malic acid,but the mechanism controlling its accumulation remains unclear.In this study,by comparing gene expression levels and organic acid contents,we found that the expression of PbPH5,which encodes a P_(3A)-ATPase,is highly correlated with malic acid accumulation in four different pear species,with correlation coefficients of 0.932**,0.656*,0.900**,and 0.518*(*,P<0.05;**,P<0.01)for Pyrus bretschneideri Rehd.,P.communis Linn.,P.pyrifolia Nakai.,and P.ussuriensis Maxim.,respectively.Moreover,the overexpression of PbPH5 in pear significantly increased the malic acid content.In contrast,silencing PbPH5 via RNA interference significantly decreased both its transcript level and the pear fruit malic acid content.A subcellular localization analysis indicated that PbPH5 is located in the tonoplast.Additionally,a phylogenetic analysis indicated that PbPH5 is a PH5 homolog gene that is clustered with the Petunia hybrida,Malus domestica,and Citrus reticulata genes.Considered together,these findings suggest that PbPH5 is a functionally conserved gene.Furthermore,the accumulation of malic acid in pear fruit is at least partly related to changes in the PbPH5 transcription levels.
基金the Project of International Cooperation between China and Ukraine(No.043-05)National Natural Science Foundation and Key Lab of Polymer Materials of Gansu Province for their financial supports.
文摘A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated.The method is based on adding malic acid into classical Belousov-Zhabotinskii(B-Z)oscillating chemical system to form a double substrate one.The results showed that when the concentration of cobalt ion was in the range of 5.27×10^(-8)to 5.37×10^(-12)mol L^(-1),the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration.The sensitivity and precision of the developed method were quite satisfactory.The limit of detection was down to 5.20×10^(-13)tool L^(-1)which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far.Some factors influencing the determination were also examined.The method has been successfully used to determine cobalt ion in vitamin Bl2 injection.
基金the framework of budget project No.0303-2016-0006 for Boreskov Institute of Catalysis
文摘The catalyst preparation strategy was based on a strict introduction sequence of rhenium and platinum precursors and their strong interaction with carbon support resulted in the formation of 0.5 nm Pt-Re Ox species of atomic dispersion, where platinum is metallic, while monolayer rhenium is partially oxidized(Re2+). The reaction kinetics was studied taking into account the process of L-malic acid association leading to the formation of inactive cyclic oligomeric species. High TOFs(ca. 50 h-1), selectivities(ca. 99%)and stability of Pt-Re Ox/C catalysts in aqueous-phase hydrogenation of L-malic acid, which are close to those of the homogeneous pincer type complexes, were revealed at mild conditions(T = 90–130 °C). Taking into account that(i) hydrogenation reaction occurred 2–3 orders of magnitude faster than its racemization and(ii) association of L-malic acid dominates at low temperatures and in a concentrated solution,special reaction conditions that allow obtaining chemically and optically(ee > 99%) pure(S)-3-hydroxy-γ-butyrolactone and(S)-1,2,4-butanetriol were found. Basing on HAADF-STEM, EDX, XPS, and kinetic studies, the structure of active species and basic reaction pathways are proposed.
文摘Terpolymer of 1, 8-octanediol, adipic acid, and L-malic acid was synthesized via a lipase-catalyzed direct polycondensation. The products were characterized by GPC and 1H NMR. The results indicated that the molecular weight of the prepared polymers decreased with increasing L-malic acid content in the monomer feed ratio, and that change in the L-malic acid content from 0 to 20 mol % did not remarkably influenced on the molecular weight distribution Mw /Mn of the prepared samples. The 1H NMR spectra of the obtained copolymer samples showed that hydroxyl groups of L-malic acid did not take part in the polymerization reaction.
基金supported by the Seoul Research and Business Development Program(No.10524).One of theauthors M.N.A.Khan is a recipient of Post-Doctoral fellowship from the post-BK2 1 program,Korea.
文摘A synthesis of methyl 2-hydroxy-4-oxo-4-(substituted phenyl)butanoates has been accomplished using Friedel-Crafts acylation of substituted benzenes with 2-acetoxybutanoyl chloride.The key feature of this strategy is that various 4-arylbutanoates can be obtained conveniently,which are important intermediates for the synthesis of biologically active compounds including ACE inhibitors.
文摘In order to create a functionalized biodegradable polymer for vascular tissue engineering application,poly(DL- lactide-co-RS-β-malic acid)(PDLLMAc)was synthesized.PDLLMAc was obtained after hydrogenolysis of poly(DL- lactide-co-RS-β-benzyl malolactonate)(PDLLMA),which was from the ring-opening polymerization of DL-lactide(DLLA) and RS-β-benzyl malolactonate(MA)using stannous octoate as catalyst.The copolymers were characterized by ~1H-NMR, FTIR,GPC and DSC.The tensile strength and water uptake of the cop...
基金ACKNOWLEDGMENTS This work was supported by the Program for New Century Excellent Talents in University, the Science and Technology Foundation for Young Scholars in Sichuan Province, and the National Natural Science Foundation of China （No.10774104）.
文摘脲 L 苹果酸的酸，一份新秒订单非线性的光水晶，用密度被学习功能的理论(DFT ) 。PBEPBE/6-31+G (d， p ) 方法，为从几个 DFT 方法比较结果的最佳的方法，被选择学习分子的结构。红外线、紫外可见的系列被获得并且与实验相比。紫外可见的光谱被分子的轨道的人口也分析。几何学，和水里的红外线、紫外可见的系列与极化的连续统模型一起在联合用 DFT 方法被学习由溶剂效果预言不安。
基金Supported by the National Natural Science Foundation of China (No. 29836130).
文摘Extraction equilibrium features of succinic acid,malic acid,maleic acid and fumaric acid were investigated systematically with trioctylamine (TOA) in chloroform,4-methyl-2-pentanone (MIBK) and 1-octanol.Fourier transform-infrared(FTIR) spectroscopic analysis of organic samples loaded with the acid show that amine forms 1:1 complex of ion-pair association with succinic acid,malic acid and maleic acid,and 1:1,2:1 complex of ion-pair association with fumaric acid.It is proposed that the complex forms depend on the second dissociation constant of the dibasic acid,pKa2.Results of equilibrium experiments show that diluents affects extraction behavior,and depend on the solute concentration.Protic diluents,chloroform and 1-octanol,are more effective than the others when the equilibrium solute concentration.Protic diluents,chloroform and 1-octanol,are more effective tthan the others when the equilibrium solute concentration is lower than 1:1 stoichiometry of TOA to acid,otherwise the extraction ability shows that MIBK>1-octanol>chloroform for malic and maleic acids,and 1-octanol>MIBK>chloroform for succinic acid.Overloading(Solute concentration in organic phase is lager than TOA concentration) appears for all of the studied acids, and the sequence of overloading amount is the same as that of distribution constant of diluent.The results show that the sequence of extraction ability of different acid is the same as that of acidity at low equilibrium solute concentrations,while it is the same as the sequence of hydrophobicity at high equilibrium concentrations.
文摘Crystals of the chiral malic acid hydrate (C 4H 6O 5·H 2O) were unexpectedly obtained from an ethanol/water solution containing racemic D,L-malic acid and L-asparagine. The crystal belongs to orthorhombic space group P2 12 12 1 with cell dimensions of a=0.5576(1), b=0.9818(2), c=1.1793(2) nm, V=0.6455(2) nm 3, Z=4, μ(Mo K α)=0.152 mm -1, F(000)=320, D c=1.565 g·cm -3, R=0.051, wR=0.136 for 657 observed reflections . The significant difference in bond distances for carboxyl groups suggests that the crystal consist of malate anion and protonized crystalline water. This is a report for direct separation of racemic mixture, i.e., without the formation of a molecular complex of raceme with a chiral separating reagent.
