Electronic signals are the default carriers of information in solid-state devices, while biology mainly traffics in chemical and ionic signals. Materials that can transduce biological and electronic signals are key to bridging living systems with synthetic devices such as soft robotics, therapeutic and prosthetic implants, bioenergy technologies, and wearable sensors. Ideal materials should mimic not only the soft mechanics and biomolecularly defined interfaces of cells and tissue, but also the dynamic nature of biological systems in response to stimuli. This talk will cover our progress in understanding the structural basis for conductivity in natural and synthetic protein wires, and the development of sequence-encoded designs for stimuli-responsive behavior:
(1) Nature has evolved protein assemblies that conduct electronic charge over nanometer to centimeter distances as part of an anaerobic respiratory metabolic pathway called extracellular electron transfer. Our findings show that such assemblies in the model anaerobe, Geobacter sulfurreducens, are fibers made of cytochrome (heme-containing protein) polymers that array heme in one-dimensional chains along the fiber axes. This alignment of redox active heme supports long-range electron transport along the nanowires to facilitate oxidation of remote electron acceptors. Our work seeks to understand structural determinants of their biochemical and electron transport properties.
(2) We design heme-free and heme-binding peptides (short proteins) that self-assemble into conducting filaments and mimic the environmental responsiveness of other biological filaments. To address this challenge, we developed a platform for the programmable assembly of de novo peptides by balancing order and disorder inducing peptide sequence motif. This approach provides control over the hierarchical assembly of complex supramolecular peptide nanostructures. The gating of supramolecular interactions in response to pH, redox, and biochemical stimuli represent key advances towards the interconversion of biological signals across bionic interfaces and the integration of synthetic biology with a synthetic materials toolkit.