Improved electrical conductance through self-assembly of bioinspired peptides into nanoscale fibers

• We designed a novel peptide sequence from natural amino acids which forms nanofibers in water.
• The nanofibers were investigated by AFM, fluorescence and CD spectroscopy.
• A film of self-assembled peptide shows conductivity in air and vacuum.
• We propose that stacking of phenylalanine between peptides leads to conductivity.

We investigated the electrical conductance of films consisting of bio-inspired peptide molecules and of their extended form, self-assembled nanoscale fibers. Here, the entirely natural and novel peptide sequence, GFPRFAGFP, was designed based on naturally occurring fibrous proteins. To attain electrical conductance, we implemented phenylalanine residues in the sequence such that the aromatic rings are present along face of the molecule. We confirmed self-assembly of nanoscale fibers in pure water after incubating the peptides at 37 °C by AFM. The morphology and conformation of the incubated peptide fibers were studied using AFM, fluorescence spectroscopy and circular dichroism spectroscopy. It was shown that very thin fibers with a single-molecule-level diameter form. The helical feature of the peptide backbone and enhanced stacking of aromatic residues were also investigated. This aromatic stacking is important to our electrical measurements as, even in vacuum environment, films of non-incubated GFPRFAGFP sometimes show apparent conductance while those containing self-assembled nanoscale fibers show stable and improved conductance. We propose that this effect may be due to extended stacking of aromatic residues providing π – π conjugation along the fiber.

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