RESUMEN
An artificial amyloid-based redox hydrogel was designed for mediating electron transfer between a [NiFeSe] hydrogenase and an electrode. Starting from a mutated prion-forming domain of fungal protein HET-s, a hybrid redox protein containing a single benzyl methyl viologen moiety was synthesized. This protein was able to self-assemble into structurally homogenous nanofibrils. Molecular modeling confirmed that the redox groups are aligned along the fibril axis and are tethered to its core by a long, flexible polypeptide chain that allows close encounters between the fibril-bound oxidized or reduced redox groups. Redox hydrogel films capable of immobilizing the hydrogenase under mild conditions at the surface of carbon electrodes were obtained by a simple pH jump. In this way, bioelectrodes for the electrocatalytic oxidation of H2 were fabricated that afforded catalytic current densities of up to 270â µA cm-2 , with an overpotential of 0.33â V, under quiescent conditions at 45 °C.
Asunto(s)
Amiloide/metabolismo , Hidrogeles/metabolismo , Hidrógeno/metabolismo , Hidrogenasas/metabolismo , Amiloide/química , Biocatálisis , Electrodos , Transporte de Electrón , Hidrogeles/química , Hidrógeno/química , Hidrogenasas/química , Modelos Moleculares , Oxidación-Reducción , Tamaño de la PartículaRESUMEN
We propose the very first "Nernstian biosupercapacitor", a biodevice based on only one redox polymer: poly(vinyl imidazole-co-allylamine)[Os(bpy)2 Cl], and two biocatalysts. At the bioanode PQQ-dependent glucose dehydrogenase reduces the Os3+ moieties at the polymer to Os2+ shifting the Nernst potential of the Os3+ /Os2+ redox couple to negative values. Concomitantly, at the biocathode the reduction of O2 by means of bilirubin oxidase embedded in the same redox polymer leads to the oxidation of Os2+ to Os3+ shifting the Nernst potential to higher values. Despite the use of just one redox polymer an open circuit voltage of more than 0.45â V was obtained during charging and the charge is stored in the redox polymer at both the bioanode and the biocathode. By connecting both electrodes via a predefined resistor a high power density is obtained for a short time exceeding the steady state power of a corresponding biofuel cell by a factor of 8.