Optical Detection of Dimethyl Methyl-Phosphonate with Monosulfonate Tetraphenyl Porphyrin-Plant-Esterase Complex
We have developed a method for spectrophotometric detection of organophosphate neurotoxins based on the spectrophotometric changes of the monosulfonate tetraphenyl porphyrin (TPPS1)-plant-esterase complex. Using TPPS1 that binds to plant-esterase specifically as a spectral reporter, the absorbance intensity at the characteristic peak of the TPPS1-plant-esterase complex decreases when the complex interacts with dimethyl methyl-phosphonate (DMMP), a common chemical warfare nerve agent simulant. These spectral changes in the presence of DMMP are more pronounced in the difference spectra (TPPS1 + plant-esterase + DMMP) − (TPPS1 + plant-esterase), and can be observed both in solution and when immobilized on a surface. In solution, the difference spectrum has a trough at 420 nm. On the integrated surface, the difference spectrum has a trough at 422 nm. The absorbance changes show linear dependence on DMMP concentration within 4.5 × 10−10 to 9 × 10−7 mol/L range, with a detection limit of 9 × 10−11 mol/L when measured in solution, and 4.5 × 10−10 mol/L when immobilized on a surface. Since the plant-esterase is widely available and the TPPS1 provides a simple and convenient optical report of organophosphate neurotoxins binding to the enzyme, the method described here can be applied in rapid warning and field analysis.
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Document Type: Research Article
Publication date: February 1, 2009
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