Significant Enhancement of Proton Transport in Bioinspired Peptide Fibrils by Single Acidic or Basic Amino Acid Mutation

Bioinspired materials are extremely suitable for the development of bio-compatible and environmentally friendly functional materials. Peptide-based assemblies are remarkably attractive for such tasks, since they provide a simple way to fuse together functional and structural protein motifs in artificial materials. Motivated by this idea, it is shown here that the introduction of a single acidic, or basic, amino acid into the side chain of a heptameric self-assembling peptide increases proton conduction in the resulting fibers by two orders of magnitude. This self-doping effect is much more pronounced than the effect induced by the peptide's acidic and basic termini groups. Furthermore, the self-doping process is found to be significantly more effective for acidic side chains than for basic ones due to both much more effective self-doping process, resulting in an order of magnitude larger concentration of charge carriers for the acidic assemblies, and higher mobility of the formed charge carriers - almost threefolds in this case. This work facilitates the realization of unique bioinspired self-assembled proton conducting materials that may find uses in the emerging bioprotonic technology. The presented design flexibility and, in particular, the ability to introduce both proton and proton holes further extend the usefulness of these materials.