De Novo Design of a CytochromebMaquette for Electron Transfer and Coupled Reactions on Electrodes

Experimental explorations of functional mechanisms in natural electron-transfer proteins are often frustrated by their fragility and extreme complexity. We have designed and synthesized four-α-helix-bundle redox proteins, maquettes, that are much simplified and more robust than natural redox proteins and can be designed to bind onto electrode surfaces to facilitate systematic investigations. The points of interest that can be now assessed are not only the processes that govern biological assembly of equilibrium structures, electrochemistry, and electron tunneling rates but also how these factors are coupled together to effect redox driven catalysis. Here we describe maquettes that bis-histidine ligate protoporphyrin IX (heme), much like native b cytochromes, as well as contain charged surface patches, much like native cytochrome c. The positively charged residues aid adsorption to negatively charged surfaces, such as gold electrodes modified by 11-mercaptoundecanoic acid, and facilitate cyclic voltammetry...