Voltammetric monitoring of laccase-catalysed mediated reactions

Fernández‐Sánchez, César; Tzanov, Tzanko; Gübitz, Georg; Cavaco‐Paulo, Artur

doi:10.1016/s1567-5394(02)00119-6

Cited by 116 publications

(73 citation statements)

References 27 publications

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“…40%) current at 0.2 V was obtained at 37°C. These results are in agreement with previous reports where the maximal bioelectrocatalytic activity of Lc from different sources was observed in the temperature range 35 -50°C [41][42][43][44]. While the solubility of O 2 decreases with increasing temperature, the increase in the diffusion coefficient offsets this decrease, resulting in an increased response [37,[45][46] which is in agreement with the results reported for homogeneous ThLc catalysis which has a temperature optimum of 45°C [47].…”

Section: Resultssupporting

confidence: 93%

Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes

Salaj-Kośla

Pöller

Schuhmann

et al. 2013

Bioelectrochemistry

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The enzyme Trametes hirsuta laccase undergoes direct electron transfer at unmodified nanoporous gold electrodes, displaying a current density of 28 A/cm 2 . The response indicates that ThLc was immobilised at the surface of the nanopores in a manner which promoted direct electron transfer, in contrast to the absence of a response at unmodified polycrystalline gold electrodes. The bioelectrocatalytic activity of ThLc modified nanoporous gold electrodes was strongly dependent on the presence of halide ions. Fluoride completely inhibited the enzymatic response, whereas in the presence of 150 mM Cl -, the current was reduced to 50% of the response in the absence of Cl -. The current increased by 40% when the temperature was increased from 20°C to 37°C. The response is limited by enzymatic and/or enzyme electrode kinetics and is 30% of that observed for ThLc co-immobilised with an osmium redox polymer. Keywords: Laccase, direct electron transfer, nanoporous gold 2 IntroductionElectron transfer (ET) reactions are ubiquitous in nature. Controlling the rate of these reactions can be of significant benefit in developing biochemical systems that utilise redox proteins and enzymes and in particular, in applications that provide power for implanted or portable electronic devices. ET can be achieved directly (direct electron transfer, DET) or by the use of mediators (mediated electron transfer, MET) to shuttle electrons between the redox centre of the enzyme and the electrode. However, mediators are unselective and can also give rise to interfering effects [1][2][3]. DET-based devices offer high selectivity and sensitivity due to the absence of mediators. In addition, devices based on DET operate at potentials close to the redox potential of the enzyme, maximising the potential difference between the cathode and anode for biofuel cell applications [2]. Moreover, DET can be used to provide detailed information on the kinetics and thermodynamics of the ET process. However, the low stability of the enzyme layer together with the long distances over which ET occurs, represent major obstacles for DET based devices. In addition, the shielding mechanism of the enzymatic redox centre by the protein shell can disrupt DET [2,4]. One approach in optimizing and enabling rapid DET is to design the electrode surface with an architecture which promotes efficient rates of ET. In this way the electrode morphology ensures the most efficient orientation of the enzymatic redox centre and facilitates communication with the electroactive surface. Porous electrodes can be used to encapsulate the enzyme within a network of cavities, shortening the distance for electron transfer to the redox active site, which will promote more efficient and rapid rates of electron transfer [5]. However, the number of redox enzymes capable of interacting directly with the electrode while catalyzing the enzymatic reaction is limited, with estimates of approximately 5% of all enzymes exhibiting such a response [6].DET in enzymes was first described in 1978 fo...

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Section: Resultssupporting

confidence: 93%

Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes

Salaj-Kośla

Pöller

Schuhmann

et al. 2013

Bioelectrochemistry

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“…The appearance of two broad anodic peaks in the reverse scan showed two step oxidation of the AQ reduction product The cathodic peak width (E pc -E pc/2 ) of 34 mV (close to the theoretical value of 30 mV) indicated the transfer of two-electrons as reported by Bard et al [20]. The equal anodic and cathodic currents at pH 9.0, with peak potential difference of 75 mV can be attributed to the almost reversible nature of the overall redox process under these conditions [21]. The variation in voltammetric response indicated the strong dependency of the AQ redox mechanism on the pH of the medium.…”

Section: Resultssupporting

confidence: 82%

Electrochemical investigations of unexplored anthraquinones and their DNA binding

Shah¹,

Rauf²,

Ullah³

et al. 2013

J. Electrochem. Sci. Eng.

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“…The two former conditions have been confirmed with acetosyringone, since voltametric and electron paramagnetic resonance studies have shown the true reversibility of the substrate reaction (19) and the long half-life of its phenoxy radical (35). In contrast, the -NO·-radical from HBT inactivates laccase, and due to its high reactivity, decays rapidly to benzotriazole and other inactive compounds (30).…”

Section: Discussionmentioning

confidence: 89%

Lignin-Derived Compounds as Efficient Laccase Mediators for Decolorization of Different Types of Recalcitrant Dyes

Camarero

Ibarra

Martı́nez

et al. 2005

Appl Environ Microbiol

518

280

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Ten phenols were selected as natural laccase mediators after screening 44 different compounds with a recalcitrant dye (Reactive Black 5) as a substrate. Their performances were evaluated at different mediator/dye ratios and incubation times (up to 6 h) by the use of Pycnoporus cinnabarinus and Trametes villosa laccases and were compared with those of eight known synthetic mediators (including -NOH-compounds). Among the six types of dyes assayed, only Reactive Blue 38 (phthalocyanine) was resistant to laccase-mediator treatment under the conditions used. Acid Blue 74 (indigoid dye), Reactive Blue 19 (anthraquinoid dye), and Aniline Blue (triarylmethane-type dye) were partially decolorized by the laccases alone, although decolorization was much more efficient and rapid with mediators, whereas Reactive Black 5 (diazo dye) and Azure B (heterocyclic dye) could be decolorized only in the presence of mediators. The efficiency of each natural mediator depended on the type of dye to be treated but, with the only exception being Azure B (<50% decolorization), nearly complete decolorization (80 to 100%) was attained in all cases. Similar rates were attained with the best synthetic mediators, but the reactions were significantly slower. Phenolic aldehydes, ketones, acids, and esters related to the three lignin units were among the best mediators, including p-coumaric acid, vanillin, acetovanillone, methyl vanillate, and above all, syringaldehyde and acetosyringone. The last two compounds are especially promising as ecofriendly (and potentially cheap) mediators for industrial applications since they provided the highest decolorization rates in only 5 to 30 min, depending on the type of dye to be treated.Laccases are multicopper oxidases that catalyze the oneelectron oxidation of substituted phenols, anilines, and aromatic thiols to their corresponding radicals with the concomitant reduction of molecular oxygen to water. Laccases are produced by plants and fungi, including white-rot basidiomycetes responsible for lignin degradation in nature (36, 46), although some bacterial laccases have been recently described and fully characterized (17). It is because of the involvement of laccases in lignin degradation that they were first investigated for applications in the pulp and paper industry as substitutes for chlorine-containing reagents for pulp bleaching (38, 41).The broad substrate specificities of laccases, together with the fact that they use molecular oxygen as the final electron acceptor instead of the hydrogen peroxide used by ligninolytic peroxidases (38), make these enzymes highly interesting for the pulp and paper industry as well as for other industrial and environmental applications. However, the low redox potentials of laccases (0.5 to 0.8 V) compared to those of ligninolytic peroxidases (Ͼ1 V) only allow the direct degradation by laccases of low-redox-potential phenolic compounds and not the oxidation of the most recalcitrant aromatics, including different industrial dyes (49). Nevertheless, insights into lignin d...

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Voltammetric monitoring of laccase-catalysed mediated reactions

Cited by 116 publications

References 27 publications

Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes

Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes

Electrochemical investigations of unexplored anthraquinones and their DNA binding

Lignin-Derived Compounds as Efficient Laccase Mediators for Decolorization of Different Types of Recalcitrant Dyes

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