A simple and sensitive ion-paring HPLC-MS/MS method with negative ion mode has been developed and validated for the quantification of SA in milk.The separation was performed on C18 column with a mobile phase consistin...A simple and sensitive ion-paring HPLC-MS/MS method with negative ion mode has been developed and validated for the quantification of SA in milk.The separation was performed on C18 column with a mobile phase consisting of 4 mmol/L tetrabutylammonium hydroxide-methanol at a flow rate of 0.2 mL/min under the gradient elution.The retention time of SA was 6.1 min.Triple-quadrupole MS/MS detection was operated in negative mode by monitoring the transition of m/z 308.1>87.1 for SA.Validation results indicated that the lower limit of quantification was 0.060 mg/L and the assay showed a linear range of 0.1-100 mg/L and gave a correlation coefficient(r) of 0.998.The relative standard deviations were less than 10% at all tested concentration levels.The method has been successfully applied to the analysis of SA in milk,milk powder and breast milk.展开更多
It has been found that Ser His could cleave bovine serum albumin(BSA), with the most suitable pH around 6.0. The kinds of buffers have different influences on the cleavage activity. The phosphate buffer and BR buffer ...It has been found that Ser His could cleave bovine serum albumin(BSA), with the most suitable pH around 6.0. The kinds of buffers have different influences on the cleavage activity. The phosphate buffer and BR buffer are the most effective. The hydroxyl group of the serine residue is the essential functional group for the cleavage, while the amide bond, imidazole, and carboxyl group of Ser His increase the cleavage activity.展开更多
目的研究人肝癌细胞中Pokemon对Shp2表达的影响。方法通过RT-PCR、Real time PCR和Western blot方法检测人肝癌细胞系QGY-7703和人正常肝细胞系HL-7702中Pokemon和Shp2的mRNA和蛋白表达水平差异;并通过瞬时转染si-Pokemon RNA沉默QGY-7...目的研究人肝癌细胞中Pokemon对Shp2表达的影响。方法通过RT-PCR、Real time PCR和Western blot方法检测人肝癌细胞系QGY-7703和人正常肝细胞系HL-7702中Pokemon和Shp2的mRNA和蛋白表达水平差异;并通过瞬时转染si-Pokemon RNA沉默QGY-7703细胞中Pokemon使其低表达,再检测Shp2的mRNA和蛋白水平变化。结果 Pokemon在人肝癌细胞系QGY-7703中的表达水平高于人正常肝细胞系HL-7702,Shp2的表达水平高低与Pokemon表达一致;在QGY-7703细胞中沉默Pokemon表达之后,Shp2的表达也相应降低。结论原癌基因Pokemon作为一种转录因子,可能调控Shp2的表达。展开更多
文摘A simple and sensitive ion-paring HPLC-MS/MS method with negative ion mode has been developed and validated for the quantification of SA in milk.The separation was performed on C18 column with a mobile phase consisting of 4 mmol/L tetrabutylammonium hydroxide-methanol at a flow rate of 0.2 mL/min under the gradient elution.The retention time of SA was 6.1 min.Triple-quadrupole MS/MS detection was operated in negative mode by monitoring the transition of m/z 308.1>87.1 for SA.Validation results indicated that the lower limit of quantification was 0.060 mg/L and the assay showed a linear range of 0.1-100 mg/L and gave a correlation coefficient(r) of 0.998.The relative standard deviations were less than 10% at all tested concentration levels.The method has been successfully applied to the analysis of SA in milk,milk powder and breast milk.
文摘It has been found that Ser His could cleave bovine serum albumin(BSA), with the most suitable pH around 6.0. The kinds of buffers have different influences on the cleavage activity. The phosphate buffer and BR buffer are the most effective. The hydroxyl group of the serine residue is the essential functional group for the cleavage, while the amide bond, imidazole, and carboxyl group of Ser His increase the cleavage activity.
