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Daniel R. Thevenot - One of the best experts on this subject based on the ideXlab platform.
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sensitive detection of organophosphorus pesticides using a needle type amperometric acetylcholinesterase based bioelectrode thiocholine electrochemistry and Immobilised Enzyme inhibition
Journal of Enzyme Inhibition and Medicinal Chemistry, 2002Co-Authors: Graziella L. Turdean, Ionel Catalin Popescu, Liviu Oniciu, Daniel R. ThevenotAbstract: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 μM for dipterex and 0.4 μM for paraoxon. A kinetic analysis of the AChE-pesticide interaction process using Hanes-Woolf or Lineweaver-B...
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Sensitive Detection of Organophosphorus Pesticides Using a Needle Type Amperometric Acetylcholinesterase-based Bioelectrode. Thiocholine Electrochemistry and Immobilised Enzyme Inhibition
Journal of Enzyme Inhibition and Medicinal Chemistry, 2002Co-Authors: Graziella L. Turdean, Ionel Catalin Popescu, Liviu Oniciu, Daniel R. ThevenotAbstract:An acetylcholinesterase (AChE) based amperometric bioelectrode for a selective detection of low concen¬ trations 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, KClSat was suitable for a selective and sensitive amperometric detection of thiocholine. The acetylthio-choline detection under Enzyme kinetic control was found in the range of 0.01-0.3 U cm~" of Immobilised AChE. The detection limit, calculated for an inhibition ratio of 10%, was found to reach 5 jxM for dipterex and 0.4 jaIVI 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.
Graziella L. Turdean - One of the best experts on this subject based on the ideXlab platform.
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sensitive detection of organophosphorus pesticides using a needle type amperometric acetylcholinesterase based bioelectrode thiocholine electrochemistry and Immobilised Enzyme inhibition
Journal of Enzyme Inhibition and Medicinal Chemistry, 2002Co-Authors: Graziella L. Turdean, Ionel Catalin Popescu, Liviu Oniciu, Daniel R. ThevenotAbstract: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 μM for dipterex and 0.4 μM for paraoxon. A kinetic analysis of the AChE-pesticide interaction process using Hanes-Woolf or Lineweaver-B...
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Sensitive Detection of Organophosphorus Pesticides Using a Needle Type Amperometric Acetylcholinesterase-based Bioelectrode. Thiocholine Electrochemistry and Immobilised Enzyme Inhibition
Journal of Enzyme Inhibition and Medicinal Chemistry, 2002Co-Authors: Graziella L. Turdean, Ionel Catalin Popescu, Liviu Oniciu, Daniel R. ThevenotAbstract:An acetylcholinesterase (AChE) based amperometric bioelectrode for a selective detection of low concen¬ trations 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, KClSat was suitable for a selective and sensitive amperometric detection of thiocholine. The acetylthio-choline detection under Enzyme kinetic control was found in the range of 0.01-0.3 U cm~" of Immobilised AChE. The detection limit, calculated for an inhibition ratio of 10%, was found to reach 5 jxM for dipterex and 0.4 jaIVI 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.
Dean Brady - One of the best experts on this subject based on the ideXlab platform.
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production of self Immobilised Enzyme microspheres using microfluidics
Process Biochemistry, 2018Co-Authors: Mesuli B Mbanjwa, Kevin Land, Thobile Windvoel, Prince M Papala, Louis Fourie, Jan G Korvink, Daniel F Visser, Dean BradyAbstract:Abstract Background Self-immobilisation of Enzymes is a useful way of producing particulate biocatalysts that are easy to recover while still retaining high specific activity. The spherezyme microsphere immobilisation technique is useful in that it provides structured Enzyme micro-particles within a specific size range. Herein an alternative micro-fluidics spherezyme production technology is evaluated. Results Spherezymes of Pseudomonas fluorescens lipase were successfully produced using a new continuous microfluidic method involving the two sequential steps of emulsion formation and subsequent protein cross-linking. The microchannel design with two flow-focussing junctions provided uniform Enzyme microspheres with a particle diameter of 50 μm and a size distribution within 3% as determined by a microscopic image analysis method. The size of the particles could be finely controlled as a function of the microreactor flow rate and monitored in real time. The structure of the particles were analysed using focused ion beam scanning electron microscopy (FIB-SEM), which showed that the external structure was less porous, with pores of up to 492 nm, while internal structure had a much greater porosity with a maximum pore size of 1735 nm. The activity retention of the lipase after immobilisation was 65% on hydrolysis of p-nitrophenyl butyrate (PNPB) and the micro-particle biocatalyst could be recycled multiple times. Conclusion Using microfluidics provides a superior method to scale up production of lipase spherezymes with a very narrow size distribution.
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Spherezymes: A novel structured self-immobilisation Enzyme technology
BMC Biotechnology, 2008Co-Authors: Dean Brady, Justin Jordaan, Clinton Simpson, Avashnee Chetty, Cherise Arumugam, Francis S MoolmanAbstract:Background Enzymes have found extensive and growing application in the field of chemical organic synthesis and resolution of chiral intermediates. In order to stabilise the Enzymes and to facilitate their recovery and recycle, they are frequently Immobilised. However, immobilisation onto solid supports greatly reduces the volumetric and specific activity of the biocatalysts. An alternative is to form self-Immobilised Enzyme particles. Results Through addition of protein cross-linking agents to a water-in-oil emulsion of an aqueous Enzyme solution, structured self-Immobilised spherical Enzyme particles of Pseudomonas fluorescens lipase were formed. The particles could be recovered from the emulsion, and activity in aqueous and organic solvents was successfully demonstrated. Preliminary data indicates that the lipase tended to collect at the interface. Conclusion The Immobilised particles provide a number of advantages. The individual spherical particles had a diameter of between 0.5–10 μm, but tended to form aggregates with an average particle volume distribution of 100 μm. The size could be controlled through addition of surfactant and variations in protein concentration. The particles were robust enough to be recovered by centrifugation and filtration, and to be recycled for further reactions. They present lipase Enzymes with the active sites selectively orientated towards the exterior of the particle. Co-immobilisation with other Enzymes, or other proteins such as albumin, was also demonstrated. Moreover, higher activity for small ester molecules could be achieved by the Immobilised Enzyme particles than for free Enzyme, presumably because the lipase conformation required for catalysis had been locked in place during immobilisation. The Immobilised Enzymes also demonstrated superior activity in organic solvent compared to the original free Enzyme. This type of self-Immobilised Enzyme particle has been named spherezymes.
Ionel Catalin Popescu - One of the best experts on this subject based on the ideXlab platform.
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sensitive detection of organophosphorus pesticides using a needle type amperometric acetylcholinesterase based bioelectrode thiocholine electrochemistry and Immobilised Enzyme inhibition
Journal of Enzyme Inhibition and Medicinal Chemistry, 2002Co-Authors: Graziella L. Turdean, Ionel Catalin Popescu, Liviu Oniciu, Daniel R. ThevenotAbstract: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 μM for dipterex and 0.4 μM for paraoxon. A kinetic analysis of the AChE-pesticide interaction process using Hanes-Woolf or Lineweaver-B...
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Sensitive Detection of Organophosphorus Pesticides Using a Needle Type Amperometric Acetylcholinesterase-based Bioelectrode. Thiocholine Electrochemistry and Immobilised Enzyme Inhibition
Journal of Enzyme Inhibition and Medicinal Chemistry, 2002Co-Authors: Graziella L. Turdean, Ionel Catalin Popescu, Liviu Oniciu, Daniel R. ThevenotAbstract:An acetylcholinesterase (AChE) based amperometric bioelectrode for a selective detection of low concen¬ trations 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, KClSat was suitable for a selective and sensitive amperometric detection of thiocholine. The acetylthio-choline detection under Enzyme kinetic control was found in the range of 0.01-0.3 U cm~" of Immobilised AChE. The detection limit, calculated for an inhibition ratio of 10%, was found to reach 5 jxM for dipterex and 0.4 jaIVI 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.
Liviu Oniciu - One of the best experts on this subject based on the ideXlab platform.
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sensitive detection of organophosphorus pesticides using a needle type amperometric acetylcholinesterase based bioelectrode thiocholine electrochemistry and Immobilised Enzyme inhibition
Journal of Enzyme Inhibition and Medicinal Chemistry, 2002Co-Authors: Graziella L. Turdean, Ionel Catalin Popescu, Liviu Oniciu, Daniel R. ThevenotAbstract: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 μM for dipterex and 0.4 μM for paraoxon. A kinetic analysis of the AChE-pesticide interaction process using Hanes-Woolf or Lineweaver-B...
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Sensitive Detection of Organophosphorus Pesticides Using a Needle Type Amperometric Acetylcholinesterase-based Bioelectrode. Thiocholine Electrochemistry and Immobilised Enzyme Inhibition
Journal of Enzyme Inhibition and Medicinal Chemistry, 2002Co-Authors: Graziella L. Turdean, Ionel Catalin Popescu, Liviu Oniciu, Daniel R. ThevenotAbstract:An acetylcholinesterase (AChE) based amperometric bioelectrode for a selective detection of low concen¬ trations 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, KClSat was suitable for a selective and sensitive amperometric detection of thiocholine. The acetylthio-choline detection under Enzyme kinetic control was found in the range of 0.01-0.3 U cm~" of Immobilised AChE. The detection limit, calculated for an inhibition ratio of 10%, was found to reach 5 jxM for dipterex and 0.4 jaIVI 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.
