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11.
《Analytical letters》2012,45(11):1703-1719
Abstract A novel method of extraction has been developed to avoid the presence of heavy metals during the measurement of pesticides based on acetylcholinesterase (AchE) inhibition. Heavy metals have been in fact demonstrated in this article to interfere when the assay is performed by using the classic spectrophotometric Ellman's method. We present the results obtained with an assay system using two different phases, one organic and the other aqueous, in which the pesticide and the enzyme are, respectively, solubilized. In a first step, the concentration of the substrate acetylthiocholine (1 mM), of the enzyme (7 mU mL?1), and the reaction time (20 min) for measurement of enzyme activity were optimized in aqueous solution. Next, the effect of an organic phase on the enzyme activity was studied by the addition of various solvents with the activity being evaluated after 10 min of mixing. It was found that by using hexane, the enzyme retained almost 100% of its activity, and this solvent was chosen for further development of the pesticide assay. Hexane was spiked with different concentrations of pesticides and then added to the enzyme aqueous phase. The pesticides were shown to be able to inhibit the enzyme by interaction at the interface between the two solutions. The degree of inhibition obtained with increasing amounts of pesticide was evaluated. A 50% inhibition was observed for a paraoxon solution of 9×10?7 M. 相似文献
12.
Five Tyr residues present in the native organophosphate hydrolase (OPH) containing a hexahistidine tag at the N-terminus of
the protein molecule (His6-OPH) were replaced by fluorine-containing analogs using a biosynthetic approach. The modified enzyme had an extended pH-optimum
of action shifted to acidic pH and an enhanced thermal stability in the alkaline pH region.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 357–361, February, 2006. 相似文献
13.
The rate-surfactant concentration profiles for the reaction of the insecticide paraoxon with hydroxamate ions (R(CO)·NHO−, R = CH3, R = C6H5, R = 2-HOC6H4) in aqueous solutions of cetyltrimethylammonium salts, CTAX (X− = Br−, Cl−, SO3H−) have been measured at pH 11.0 at 30 °C. All these profiles are typical of micelle-assisted bimolecular reactions involving interfacial ion exchanges. The salicylhydroxymic acid-CTACl combination is most reactive. 相似文献