Enzyme-free dual-amplification assay for colorimetric detection of tetracycline based on Mg2+-dependent DNAzyme assisted catalytic hairpin assembly.

Detection of ultralow concentration of tetracycline (TC) plays a key role in food safety and human health. Herein, we fabricated an enzyme-free dual-amplification assay for sensitive detection of TC in milk. The sensing system ingeniously combined Mg2+-dependent DNAzyme (MNAzyme) cleavage and catalytic hairpin assembly (CHA). Through the binding of TC and specific aptamer (Apt), DNA1 was released from the Apt-DNA1 complex. Then the separated DNA1 would hybridize with DNA2 to activate the catalytic activity of MNAzyme, which subsequently cleaved the substrate H0 and generated a new unit to trigger the following CHA reaction between H1 and H2, thereby releasing the G-rich sequence of H1 to induce the formation of G-quadruplex-hemin DNAzyme as a colorimetric signal readout. Under optimal conditions, the absorption intensity exhibited a significant linear correlation with the logarithm of the target TC concentration over a range of 4 orders of magnitude dynamic range from 1 pM to 10 nM. The limit of detection was calculated to be 0.89 pM and the method showed high selectivity for TC. More impressively, the proposed method was employed for TC determination in the milk sample.

Parameters optimization in Heparin affinity chromatography purification of human coagulation factor Ⅸ / 中国输血杂志

【Objective】 To optimize the purification conditions of heparin affinity chromatography in the purification of human coagulation factor Ⅸ by response surface method and establish the optimal chromatography process parameters. 【Methods】 The effect of sample loading temperature on purification efficiency was analyzed through single factor test. Three-factor three-level response surface method was used to optimize the chromatographic elution conditions. The Folin phenol method and the automatic hemagglutination analyzer were used to determine the total protein content and human coagulation factor Ⅸ titer, respectively. The purification effect was evaluated by activity index and process recovery rate. 【Results】 The optimized optimal chromatographic conditions were loading at 5 ℃, washing 4 CV, eluent formulation of sodium citrate 20 mmol/L, arginine hydrochloride 18.7 mmol/L, NaCl 611.6 mmol/L and pH 7.5; under this optimal setting, the recovery rate of the chromatographic process was (46.6±2.9) %, titer of factor Ⅸ rated to (68.4±4.7) IU/mL and specific activity was (62.8±3.3) IU/mg. 【Conclusion】 The optimized parameters of heparin affinity chromatography process by response surface method can produce better purification effect on human coagulation factor Ⅸ.

Analyse selective non-operative management of closed splenic injuries in 98 cases / 重庆医学

Objective To discusses the methods of the case selection and monitoring and diagnosis and treatment to selective non-operative management of closed splenic injuries .Methods The clinical data and results of 98 cases from October 1999 to Octo-ber 2011 with closed splenic injuries managed non-operative treatment were analyzed retrospectively .Results There were 90 cases (91 .8% ) conservative successfully ,5 cases(5 .1% ) transit operation because hematoma increase and bleeding continuously during therapeutic observation and 2 cases(3 .1% ) died from multiple injuries merge infection and multiple organ failure .Conclusion Most of the closed splenic injuries below level Ⅱcan be treated by non-operative management ,the effect and prognosis determined by the reasonable case selection and monitoring conditions and diagnosis and treatment .