57 research outputs found
Electrochemical study of the intermolecular electron transfer to Pseudomonas aeruginosa cytochrome cd1 nitrite reductase
No full textThe kinetics of electron transfer reaction between cytochrome cd(1) nitrite reductase (NiR) from Pseudomonas aeruginosa and various physiological/non physiological redox partners was investigated using cyclic voltammetry at the pyrolytic graphite electrode. While NiR did not exchange electron with the electrode, cytochrome c(551) and azurin, both from Ps. aeruginosa, behaved as fast electrochemical systems. The intermolecular electron transfers between NiR and cytochrome c(551) or azurin as electron shuttles, in the presence of nitrite, were studied. Second order rate constants of 2 x 10(6) and 1.4 x 10(5) M-1 s(-1) are calculated for cytochrome c(551) and azurin, respectively. The dependence of the second-order rate constant on ionic strength and pH is discussed. Finally, the effect of the global charge of the electron shuttles was explored using differently charged species (proteins or small ions). The experimental results suggest involvement of polar interactions as well as of hydrophobic contacts in the protein recognition prior to the intermolecular electron transfer. As the cross-reaction between Ps. nautica cytochrome c(552) and Ps. aeruginosa NiR was shown to be as efficient as the catalytic reaction involving the physiological partners, it is concluded to a 'pseudo-specificity' in the recognition between NiR and the electron donor
Biohydrogène : Stratégies d'immobilisation d'hydrogénases sur électrodes
No full textInternational audienc
Editorial: Women in Science: Chemistry
No full textFollowing UNESCO’s official celebration of the International Day of Women and Girls in Science, Frontiers in Chemistry decided to run a special issue “Women in Science: Chemistry”. Indeed, although science and gender equality are essential to ensure sustainable development, less than 30% of researchers worldwide are women
Electrocatalytic reduction of uranium by bacterial cytochromes: biochemical and chemical factors influencing the catalytic process
No full textLayer‐by‐Layer Assemblies of Montmorillonite and Bacterial Cytochromes for Bioelectrocatalytic Devices
No full textRecent developments in high surface area bioelectrodes for enzymatic fuel cells
No full textInternational audienceEnzymatic fuel cells (EFC) function in a similar way to low temperature proton exchange membrane fuel cells (PEMFC) but use enzymes instead of noble metals as catalysts for fuel and oxidant transformation. The need for EFCs that deliver enhanced power has resulted in high surface/volume ratio conductive materials being considered as enzyme host matrices. While the enhanced surface has effectively led to higher catalytic currents, the use of high surface area nanomaterials (HSM) has also induced new issues related to the wiring of enzymes, the role of porosity, and the effect on stability. This review discusses the most important features reported in this area over the past three years, and proposes future directions concerning EFC applications. Recent developments in high surface area bioelectrodes for enzymatic fuel cells. Available from: https://www.researchgate.net/publication/318305120_Recent_developments_in_high_surface_area_bioelectrodes_for_enzymatic_fuel_cells [accessed Jul 19, 2017]
Enzyme electrodes based on redox hydrogels for glucose oxidation : effect of glucose oxidase deglycosylation and evidence for oxygen side reduction on the redox mediator
No full textLa possibilité de convertir l’activité catalytique d’une oxydoréductase en un courant électrique a permis le développement d’une grande diversité d’électrodes enzymatiques. Les anodes catalysant l’oxydation du glucose font partie des plus étudiées pour leurs applications dans la mesure de la glycémie ou dans des biopiles glucose/O2. Parmi les nombreuses stratégies disponibles, l’utilisation d’hydrogels à base de complexes d’osmium en guise de médiateurs rédox fournit d’excellents résultats, qui restent cependant limités en terme de densité de courant ou de sélectivité. Durant cette thèse, la glucose oxydase (GOx) a été déglycosylée. Les électrodes préparées avec la nouvelle enzyme délivraient des courants catalytiques plus élevés, ce qui laissait supposer initialement une diminution de la distance de saut d’électron entre la GOx et le médiateur rédox suite au retrait des oligosaccharides. Une étude avec des électrodes de différentes compositions suggère au contraire que la déglycosylation n’améliore pas le transfert électronique intrinsèque mais la structure globale de l’hydrogel. De fait, une enzyme plus petite et plus négativement chargée doit induire un volume d’hydrogel plus faible pour une même composition molaire. En second lieu, une réduction parasite de l’oxygène affectant ces anodes, non envisagée jusqu’à aujourd’hui, a été mise en évidence et étudiée. En effet, l’interférence de l’O2 n’est usuellement attribuée qu’à sa réactivité avec la GOx. La présente étude prouve que l’O2 se réduit aussi sur les complexes d’osmium si leur potentiel standard E°’ est inférieur à + 0,07 V vs. Ag/AgCl. La cinétique de cette réaction croît exponentiellement quand le E°’ du complexe diminue. En plus d’abaisser le courant d’oxydation et donc les performances de l’anode, la génération de peroxyde d’hydrogène pourrait aussi altérer sa stabilité. Ces résultats suggèrent que le choix d’un médiateur de E°’ donné doit aussi dépendre de l’amplitude de cette réduction.The possibility of converting the catalytic activity of oxidoreductase enzymes into electric current has led to the development of a high diversity of enzyme electrodes. Anodes catalysing glucose oxidation have been amongst the most studied, especially for their application in monitoring blood glucose or glucose/O2 biofuel cells. Although one of the numerous strategies available, the use of osmium-based hydrogels as redox mediators, has given excellent results, some limitations still remain such as rather low current densities, stability or selectivity Initially, the study focused on the deglycosylation of glucose oxidase (GOx). When most of the oligosaccharides around this glycoenzyme were removed, the ensuing increase in the electrode catalytic current seemed a priori to support the hypothesis of a decrease in the electron hopping distance between the enzyme redox centres and the redox mediator. However, a systematic study of electrode response for different compositions leads us to conclude that deglycosylation does not improve the intrinsic electron transfer but the whole hydrogel structure. This seems due to the smaller size and higher surface charge of the deglycosylated GOx inducing smaller hydrogel volumes than in the native-based GOx. The study then proceeded to examine the oxygen side reduction of commonly used osmium-based redox polymers. The interference of O2 on glucose oxidation current has generally been attributed to O2 reactivity with GOx. The present study shows that O2 reduction also occurs on osmium-based polymers if their formal potential E°’ is below + 0.07 V vs. Ag/AgCl. The kinetics of this reaction appears to increase exponentially when E°’ decreases. As well as reducing the oxidation current and, consequently, lowering anode performances, the generation of hydrogen peroxide could also modify electrode stability. These results suggest that the choice of redox mediator for a given E°'must also take into account the extent of O2 reduction
Recent advances in surface chemistry of electrodes to promote direct enzymatic bioelectrocatalysis
No full textInternational audienceRedox enzymes catalyze major reactions in microorganisms to supply energy for life. Their use in electrochemical biodevices requires their integration on electrodes, while maintaining their activity and optimizing their stability. In return, such applicative development puts forward the knowledge on involved catalytic mechanisms, providing a direct electrode connection of the enzyme is fulfilled. Enzymes being large molecules with active site embedded in an insulating moiety, direct bioelectrocatalysis supposes strategies for specific orientation of the enzyme to be developed. In this review, we summarize recent advances during the past three years in the chemical modification of electrodes favoring direct electrocatalysis. We present the different methodologies used according to the electrode materials, including metals, carbon-based electrodes or porous structures, and discuss the gained insights into bioelectrocatalysis. We especially focus on enzyme engineering which appears as an emerging strategy for enzyme anchoring. Remaining challenges will be discussed with regards to these last findings
Kinetic studies on the electron transfer between various c-type cytochromes and iron (III) using a voltammetric approach
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