为探究不同取代度(Degree of Substitution,DS)对苹果酸大米淀粉酯理化特性及对面条品质的影响,制备不同取代度(DS=0~0.603)苹果酸大米淀粉酯,考察了苹果酸大米淀粉酯溶解度、溶胀度、糊化特性和流变特性,以及对面条蒸煮特性、质构特性...为探究不同取代度(Degree of Substitution,DS)对苹果酸大米淀粉酯理化特性及对面条品质的影响,制备不同取代度(DS=0~0.603)苹果酸大米淀粉酯,考察了苹果酸大米淀粉酯溶解度、溶胀度、糊化特性和流变特性,以及对面条蒸煮特性、质构特性和感官特性的改善作用。结果表明,苹果酸淀粉酯的红外光谱分析显示在光谱波数约1720 cm-1处出现一个新的吸收峰。淀粉发生酯化反应后溶解度显著升高(P<0.05),但溶胀度有所下降。糊化和流变实验结果表明,低酯化淀粉(DS=0.141~0.442)的加入显著降低(P<0.05)了淀粉的峰值黏度,降低了苹果酸淀粉酯的储能模量G′和损耗模量G″,高酯化淀粉(DS=0.603)的添加不利于改善苹果酸淀粉酯的糊化和流变特性。利用相关性分析对苹果酸淀粉酯部分理化指标(溶解度、溶胀度和糊化特性)和面条的品质(蒸煮特性、质构特性和感官特性)进行了综合分析。苹果酸大米淀粉酯可以显著提升面条的整体品质,在本实验中,取代度为0.442时,小麦粉制备的面条品质较佳。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 ...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 mol 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 B12 injection.展开更多
Objective: α-ketoglutarate(α-KG) is the substrate to hydroxylate collagen and hypoxia-inducible factor-1α(HIF-1α), which are important for cancer metastasis. Previous studies have shown that the upregulation of co...Objective: α-ketoglutarate(α-KG) is the substrate to hydroxylate collagen and hypoxia-inducible factor-1α(HIF-1α), which are important for cancer metastasis. Previous studies have shown that the upregulation of collagen prolyl 4-hydroxylase in breast cancer cells stabilizes the expression of HIF-1α by depleting α-KG levels. We hypothesized that mitochondrial malic enzyme 2(ME2) might also affect HIF-1α expression via modulating α-KG levels in breast cancer cells.Methods: We evaluated ME2 protein expression in 100 breast cancer patients using immunohistochemistry and correlated with clinicopathological indicators. The effect of ME2 knockout on cancer metastasis was evaluated using an orthotopic breast cancer model. The effect of ME2 knockout or knockdown on the levels of α-KG and HIF-1α proteins in breast cancer cell lines was determined both in vitro and in vivo.Results: ME2 was found to be upregulated in the human breast cancerous tissues compared with the matched precancerous tissues(P<0.001). The elevated expression of ME2 was associated with a poor prognosis(P=0.019).ME2 upregulation was also related to lymph node metastasis(P=0.016), pathological staging(P=0.033), and vascular cancer embolus(P=0.014). Also, ME2 knockout significantly inhibited lung metastasis in vivo. In the tumors formed by ME2 knockout cells, the levels of α-KG were significantly increased and collagen hydroxylation level did not change significantly but HIF-1α protein expression was significantly decreased, compared to the control samples. In cell culture, cells with ME2 knockout or knockdown demonstrated significantly higher α-KG levels but significantly lower HIF-1α protein expression than control cells under hypoxia. Exogenous malate and α-KG exerted similar effect on HIF-1α in breast cancer cells to ME2 knockout or knockdown. Additionally,treatment with malate significantly decreased 4 T1 breast cancer lung metastasis. ME2 expression was associated with HIF-1α levels in human breast cancer samples(P=0.008).Conclusions: Our results provide evidence that upregulation of ME2 is associated with a poor prognosis of breast cancer patients and propose a mechanistic understanding of a link between ME2 and breast cancer metastasis.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
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
文摘为探究不同取代度(Degree of Substitution,DS)对苹果酸大米淀粉酯理化特性及对面条品质的影响,制备不同取代度(DS=0~0.603)苹果酸大米淀粉酯,考察了苹果酸大米淀粉酯溶解度、溶胀度、糊化特性和流变特性,以及对面条蒸煮特性、质构特性和感官特性的改善作用。结果表明,苹果酸淀粉酯的红外光谱分析显示在光谱波数约1720 cm-1处出现一个新的吸收峰。淀粉发生酯化反应后溶解度显著升高(P<0.05),但溶胀度有所下降。糊化和流变实验结果表明,低酯化淀粉(DS=0.141~0.442)的加入显著降低(P<0.05)了淀粉的峰值黏度,降低了苹果酸淀粉酯的储能模量G′和损耗模量G″,高酯化淀粉(DS=0.603)的添加不利于改善苹果酸淀粉酯的糊化和流变特性。利用相关性分析对苹果酸淀粉酯部分理化指标(溶解度、溶胀度和糊化特性)和面条的品质(蒸煮特性、质构特性和感官特性)进行了综合分析。苹果酸大米淀粉酯可以显著提升面条的整体品质,在本实验中,取代度为0.442时,小麦粉制备的面条品质较佳。
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 mol 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 B12 injection.
基金supported in part by the China Natural Sciences Foundation projects (No. 81772947)。
文摘Objective: α-ketoglutarate(α-KG) is the substrate to hydroxylate collagen and hypoxia-inducible factor-1α(HIF-1α), which are important for cancer metastasis. Previous studies have shown that the upregulation of collagen prolyl 4-hydroxylase in breast cancer cells stabilizes the expression of HIF-1α by depleting α-KG levels. We hypothesized that mitochondrial malic enzyme 2(ME2) might also affect HIF-1α expression via modulating α-KG levels in breast cancer cells.Methods: We evaluated ME2 protein expression in 100 breast cancer patients using immunohistochemistry and correlated with clinicopathological indicators. The effect of ME2 knockout on cancer metastasis was evaluated using an orthotopic breast cancer model. The effect of ME2 knockout or knockdown on the levels of α-KG and HIF-1α proteins in breast cancer cell lines was determined both in vitro and in vivo.Results: ME2 was found to be upregulated in the human breast cancerous tissues compared with the matched precancerous tissues(P<0.001). The elevated expression of ME2 was associated with a poor prognosis(P=0.019).ME2 upregulation was also related to lymph node metastasis(P=0.016), pathological staging(P=0.033), and vascular cancer embolus(P=0.014). Also, ME2 knockout significantly inhibited lung metastasis in vivo. In the tumors formed by ME2 knockout cells, the levels of α-KG were significantly increased and collagen hydroxylation level did not change significantly but HIF-1α protein expression was significantly decreased, compared to the control samples. In cell culture, cells with ME2 knockout or knockdown demonstrated significantly higher α-KG levels but significantly lower HIF-1α protein expression than control cells under hypoxia. Exogenous malate and α-KG exerted similar effect on HIF-1α in breast cancer cells to ME2 knockout or knockdown. Additionally,treatment with malate significantly decreased 4 T1 breast cancer lung metastasis. ME2 expression was associated with HIF-1α levels in human breast cancer samples(P=0.008).Conclusions: Our results provide evidence that upregulation of ME2 is associated with a poor prognosis of breast cancer patients and propose a mechanistic understanding of a link between ME2 and breast cancer metastasis.
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.
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.
