The serine/threonine protein kinase B(PKB) is related to cellular survival and regulation. PKB is composed of PH domain, catalytic domain and carboxyl terminal regulator domain. The PH domain of PKB is crucial to the ...The serine/threonine protein kinase B(PKB) is related to cellular survival and regulation. PKB is composed of PH domain, catalytic domain and carboxyl terminal regulator domain. The PH domain of PKB is crucial to the activation of kinase. In order to investigate the function and the structure function relationship of PKB, the cDNA coding fragment of PKB PH domain was amplified from human dental pulp mRNA by RT PCR and cloned into pMD18 T vector to analyze the sequence. The result showed that DNA sequence of cloned human PKB PH domain was consistent with that reported previously. To express PKB PH domain, the cDNA was subcloned into expression vector pRSET A which was then transformed into E.coli BL21(DE3) pLysS, and the strain highly expressing soluble 6His PKB PH domain in minimal medium was obtained. The fusion protein was purified by Ni 2+ NTA agarose beads. The secondary structure of the purified 6His PKB PH domain fusion protein was analysed by circular dichroism. The results indicated that the PH domain was composed of α helix 1 7%,β pleated sheet 80 5% and radom coli 17 8%.展开更多
A determination method has been optimized and validated for the simultaneous analysis of tetracycline （TC）, oxytetracycline （OTC）, chlortetracycline （CTC） and doxycycline （DC） in honey. Tetracyclines （TCs） w...A determination method has been optimized and validated for the simultaneous analysis of tetracycline （TC）, oxytetracycline （OTC）, chlortetracycline （CTC） and doxycycline （DC） in honey. Tetracyclines （TCs） were removed from honey samples by chelation with metal ions bound to small Chelating Sepharose Fast Flow columns and eluted with Na2EDTA-Mcllvaine pH 4.0 buffers. Extracts were further cleaned up by Oasis HLB solid-phase extraction （SPE）, while other solid-phase extraction cartridges were compared. Chromatographic separation was achieved using a polar end-capped C 18 column with an isocratic mobile phase consisting of oxalic acid, acetonitrile and methanol. LC with ultraviolet absorbance at 355 nm resulted in the quantitation of all four tetracycline residues from honey samples fortified at 15, 50, and 100 ng/g, with liner ranges for tetracyclines of 0.05 to 2 μg/mL. Mean recoveries for tetracyclines were greater than 50% with R.S.D. values less than 10% （n= 18）. Detection limits of 5, 5, 10, 10 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline, respectively and quantitation limits of 15 ng/g for all the four tetracyclines were determined. Direct confirmation of the four residues in honey （2-50 ng/g） was realized by liquid chromatography-tandem mass spectrometry （LC/MS/MS）. The linear ranges of tetracyclines determined by LC/MS/MS were between 5 to 300 ng/mL, with the linear correlation coefficient r〉 0.995. The limits of detection of 1 to 2 ng/g were obtained for the analysis of the TCs in honey.展开更多
文摘The serine/threonine protein kinase B(PKB) is related to cellular survival and regulation. PKB is composed of PH domain, catalytic domain and carboxyl terminal regulator domain. The PH domain of PKB is crucial to the activation of kinase. In order to investigate the function and the structure function relationship of PKB, the cDNA coding fragment of PKB PH domain was amplified from human dental pulp mRNA by RT PCR and cloned into pMD18 T vector to analyze the sequence. The result showed that DNA sequence of cloned human PKB PH domain was consistent with that reported previously. To express PKB PH domain, the cDNA was subcloned into expression vector pRSET A which was then transformed into E.coli BL21(DE3) pLysS, and the strain highly expressing soluble 6His PKB PH domain in minimal medium was obtained. The fusion protein was purified by Ni 2+ NTA agarose beads. The secondary structure of the purified 6His PKB PH domain fusion protein was analysed by circular dichroism. The results indicated that the PH domain was composed of α helix 1 7%,β pleated sheet 80 5% and radom coli 17 8%.
文摘A determination method has been optimized and validated for the simultaneous analysis of tetracycline （TC）, oxytetracycline （OTC）, chlortetracycline （CTC） and doxycycline （DC） in honey. Tetracyclines （TCs） were removed from honey samples by chelation with metal ions bound to small Chelating Sepharose Fast Flow columns and eluted with Na2EDTA-Mcllvaine pH 4.0 buffers. Extracts were further cleaned up by Oasis HLB solid-phase extraction （SPE）, while other solid-phase extraction cartridges were compared. Chromatographic separation was achieved using a polar end-capped C 18 column with an isocratic mobile phase consisting of oxalic acid, acetonitrile and methanol. LC with ultraviolet absorbance at 355 nm resulted in the quantitation of all four tetracycline residues from honey samples fortified at 15, 50, and 100 ng/g, with liner ranges for tetracyclines of 0.05 to 2 μg/mL. Mean recoveries for tetracyclines were greater than 50% with R.S.D. values less than 10% （n= 18）. Detection limits of 5, 5, 10, 10 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline, respectively and quantitation limits of 15 ng/g for all the four tetracyclines were determined. Direct confirmation of the four residues in honey （2-50 ng/g） was realized by liquid chromatography-tandem mass spectrometry （LC/MS/MS）. The linear ranges of tetracyclines determined by LC/MS/MS were between 5 to 300 ng/mL, with the linear correlation coefficient r〉 0.995. The limits of detection of 1 to 2 ng/g were obtained for the analysis of the TCs in honey.
