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Acetylcholinesterase (AChE) plays a key role in the pesticide determination. However, the extraction of AChE from natural materials has the disadvantages of low yield, complex purification and poor stability. Therefore, the preparation of recombinant AChE with high performance becomes the hot topic of researchers in recent years. In this article we summarize the progress in the expression of recombinant AChE and the improvement of its analytical characteristic. Finally, we point out that the directed evolution strategy combined with surface display technology is the future trend on improving recombinant AChE activity.

Objective: To evaluate the effect of dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) on urine superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in rats., Methods: According to 2×2 factorial analysis, 60 adult male SD rats were randomized into 10 groups (n=6), including a control group (fed with sesame oil), 3 DBP groups (fed with DBP at the doses of 30, 100 and 300 mg/kg), 3 DEHP groups (with DEHP at 50, 150, and 450 mg/kg), and 3 DBP+DEHP groups (with 30 mg/kg DBP+50 mg/kg DEHP, 100 mg/kg DBP+150 mg/kg DEHP, and 300 mg/kg DBP +450 mg/kg DEHP). The agents were administered in a single dose through gavage in a volume of 2 ml. After the treatments, the 24, 48, 72, and 96 h urine samples were collected to determine the SOD activity and MDA content., Results: DBP and DEHP, either alone or in combination, significantly decreased SOD activity and increased MDA content in the urine collected at 24 h but not at the other time points. Such changes were gradually reversed with time., Conclusion: DBP or DEHP treatment alone can result in significant oxidative damage in the kidney of rats, and the toxic effect of the combined exposure is even more obvious.

Based on the invasive plasmid antigen H gene (ipaH) of S. dysenteriae, one pair of specific primers was designed for PCR assays in this study. The concentrations of dNTP, Mg2+ and primer, dosage of Taq DNA polymerase, annealing temperature and circulating parameter in the PCR amplification system were optimized. In this way, a rapid and stable method of PCR assay for the detection of S. dysenteriae was established. The specificity and sensitivity of PCR were also analyzed. The detection limits of pure culture and genomic DNA in the PCR assay were 1.06 x 10(2) cfu/ml and 106.34 pg/PCR system, respectively. The detection limit for S. dysenteriae in artificially contaminated food samples was 3.21 x 10(4) cfu/ml. These results indicated that the PCR method for S. dysenteriae detection was simple, rapid, high in specificity and sensitivity and suitable for the detection of pathogens in foods caused by Shigella dysenteriae.

To construct the recombinant vector pBV220-scFv and express anti-clenbuterol (CBL) scFv antibody in Escherichia coli, we amplified the scFv gene using plasmid pCANTABSE-CBL as a template, recombined it with pPICZalphaA, then amplified the scFv-His-tag gene from plasmid pPICZalphaA-scFv and linked it with expression plasmid pBV220. We identified the recombinant plasmid by restrictive enzyme digestion, PCR amplification and sequence analysis. Finally, we transformed the recombinant vector into E. coli DH5alpha that was temperature-induced and expressed recombinant protein. We identified the recombinant protein by SDS-PAGE, Western blotting and indirect competitive ELISA. The results show that recombinant plasmid pBV220-scFv contained the inserted fragment with highest homology about 99.8%. The expression of scFv induced by temperature show 37 kD Mw and anti-His-tag mAb recognized-activity by SDS-PAGE and Western blotting respectively, and could competitively combine with CBL, the IC50 is 4.55 ng/mL. The recombinant plasmid pBV220-scFv is constructed and expresses the scFv gene of CBL in E. coli successfully. This study suggests the corresponding immunoassay methods could be set up by the recombinant scFv.