| 18423389 |
Morou E, Ismail HM, Dowd AJ, Hemingway J, Labrou N, Paine M, Vontas J: A dehydrochlorinase-based pH change assay for determination of DDT in sprayed surfaces. Anal Biochem. 2008 Jul 1;378(1):60-4. Epub 2008 Apr 8.
A glutathione S-transferase (GST) from the mosquito Aedes aegypti (aagste2), selected in the field as a major metabolic resistance enzyme for this parasite vector, was employed to produce a highly specific assay for the determination of DDT [1,1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene]. Detection is based on the pH change occurring in an appropriate buffer system by the concomitant release of H (+) during the aagste2-catalyzed dehydrochlorination reaction and is monitored potentiometrically or colorimetrically in the presence of a pH marker. The theoretical limit of detection (LOD) of the assay is 3.8 microg/ml, and the linear range of quantification is 12 to 250 microg/ml. The method does not recognize biologically inactive DDT analogues or major DDT photodegradants and breakdown molecules, and it is highly specific for the insecticidal p.p'DDT [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane]. The biosensor was validated with a number of insecticide swabs from DDT-sprayed surfaces and found to be reproducible and reliable as compared with high-performance liquid chromatography (HPLC) (correlation coefficient R (2)=0.98). Given the current expansion of DDT residual sprayings in many regions of Africa as a key strategic intervention for malaria vector control, this simple assay to monitor DDT levels for vector control spraying programs could have an important impact on malaria control. |
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