Wiring of heme enzymes by methylene-blue labeled dendrimers

Redox-modified branched 3D dendrimeric nanostructures may be considered as perspective wires for electrical connection between redox enzymes and electrodes. Here, we studied electron transfer (ET) reactions and bioelectrocatalysis of heme-containing horseradish peroxidase (HRP) and heme-and molibdopterin-containing sulfite oxidase (SOx), wired to gold by the methylene blue (MB)-labeled polyamidoamine (PAMAM) dendrimers. The enzymes' electrochemical transformation and bioelectrocatalytic function could be followed at both unlabeled and MB-labeled dendrimer-modified electrodes with the formal redox potentials of the heme centers being at -341 mV for HRP and -185 mV for SOx. In contrast to the HRP-dendrimer and HRP-MB-dendrimer systems, which demonstrated very close bioelectrocatalytic patterns, multicofactor SOx wired to MB-dendrimer showed a bioelectrocatalysis superior to that based on direct ET reaction. This can be correlated with a statistically larger number of positively charged MB sites on the dendrimer surface able to electrically connect the negatively charged heme domain of SOx and the electrode. In this perspective, redox-labeled dendrimers appear to be useful tools for wiring, optimization of bioelectrocatalysis of complex intermembrane and, possibly, membrane enzymes. (C) 2017 Elsevier Ltd. All rights reserved.