| 12420757 |
Turdean GL, Popescu IC, Oniciu L, Thevenot DR: Sensitive detection of organophosphorus pesticides using a needle type amperometric acetylcholinesterase-based bioelectrode. J Enzyme Inhib Med Chem. 2002 Apr;17(2):107-15.
Thiocholine electrochemistry and immobilised enzyme inhibition.. An acetylcholinesterase (AChE) based amperometric bioelectrode for a selective detection of low concentrations of organophosphorus pesticides has been developed. The amperometric needle type bioelectrode consists of a bare cavity in a PTFE isolated Pt-Ir wire, where the AChE was entrapped into a photopolymerised polymer of polyvinyl alcohol bearing styrylpyridinium groups (PVA-SbQ). Cyclic voltammetry, performed at Pt and AChE/Pt disk electrodes, confirmed the irreversible, monoelectronic thiocholine oxidation process and showed that a working potential of +0.410 V vs. Ag/AgCl, KCl (sat) was suitable for a selective and sensitive amperometric detection of thiocholine. The acetylthiocholine detection under enzyme kinetic control was found in the range of 0.01-0.3 U cm (-2) of immobilised AChE. The detection limit, calculated for an inhibition ratio of 10%, was found to reach 5 microM for dipterex and 0.4 microM for paraoxon. A kinetic analysis of the AChE-pesticide interaction process using Hanes-Woolf or Lineweaver-Burk linearisations and secondary plots allowed identification of the immobilised enzyme inhibition process as a mixed one (non/uncompetitive) for both dipterex and paraoxon. The deviation from classical Michaelis Menten kinetics induced from the studied pesticides was evaluated using Hill plots. |
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