Stimuli responsive hierarchical assembly of supramolecular conductive fibers from coiled-coil building blocks.

Abstract

Proteins and peptides provide inspiration for synthetic stimuli-responsive nanomaterials. In this work, the assembly mechanism of a de novo designed peptide that forms α-helical coiled-coil hexamer fibers was probed through point mutations of the amino acid sequence and varying assembly solution pH. Buffer pH affects multi-scale aspects of supramolecular assembly, including peptide monomer secondary structure and interactions between α-helical coiled-coil hexamer building blocks. These higher order assembly interfaces are formed by electrostatic networks between solvent-exposed polarizable side chains, as observed by cryo-electron microscopy. One of the resulting hierarchical structures was a novel assembly of α-helical cross coiled-coils that exhibits electrical conductivity. Here, we show that pH-gated assembly can be achieved with only one amino acid mutation. This work opens materials design for more stimuli-responsive and functional materials with simple pH-gating structural motifs.