Optical Detection of a Competitive Inhibitor of Immobilized Plant-Esterase

A novel sensing film immobilizing monosulfonate tetraphenyl porphyrin (TPPS₁)-plant-esterase was prepared for the detection of dimethyl methyl-phosphonate (DMMP). The morphology of the film was analyzed by atomic force misroscope (AFM). The interaction of TPPSi with immobilized plant-esterase yielded a characteristic absorbance peak at 422 nm. Addtion of DMMP to the immobilized TPPSi-plant-esterase complex resulted in the loss of the 422 nm absorbance band due to the displacement of the porphyrin from the active site. DMMP concentrations as low as 4.5 times 10^-10 mol/ L had been detected. Since plant-esterase is widely available and TPPSi provides a simple and convenient optical report of organophosphate neurotoxins binding to the enzyme, this sensor material described here can be applied in rapid warning and field analysis.