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CECUL -Faculdade de Ciências da Universidade de Lisboa, Campo Grande, C 8 1749-016 Lisboa, Portugal





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Abstract The relevance of polyphenols in human health is a well known fact. Prompted by that, a very intensive research has been directed to get a method to detect them, wich will improve the current ones. Laccase p-diphenol:dioxygen oxidoreductase EC 1.10.3.2 is a multi-copper oxidase, wich couples catalytic oxidation of phenolic substrates with four electron reduction of dioxygen to water 1. A maximum catalytic response in oxigenated electrolyte was observed between 4.5 and 5.5 2, while for pH 6.9 the laccase was found to be inactive 3. We prepared a biosensor with laccase immobilised on a polyether sulphone membrane, at pH 4.5, wich was applied at Universal Sensors base electrode. Reduction of the product of oxidation of several polyphenols, catalysed by laccase, was done at a potential for wich the polyphenol of interest was found to respond. Reduction of catechol was found to occur at a potential of -200mV, wich is often referred to in the literature for polyphenolic biosensors. However other polyphenols did not respond at that potential. It was observed that +- catechin produced a very large cathodic current when +100mV were applied to the laccase biosensor, both in aqueous acetate and 12% ethanol acetate buffer, whereas caffeic acid responded at -50mV. Other polyphenols tested were gallic acid, malvidin, quercetin, rutin, trans-resveratrol

Keywords: Biosensor; Laccase; Polyphenol; +- catechin; Caffeic acid Biosensor; Laccase; Polyphenol; +- catechin; Caffeic acid





Autor: S. A.S.S. Gomes and M. J.F. Rebelo *

Fuente: http://mdpi.com/



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