Underlying Polymorphism: Superhelical Crystallization Induces Architectural and Functional Diversity

Crystallized peptide assemblies have demonstrated useful physicochemical and electromechanical features due to the highly ordered supramolecular packing driven by efficient and extensive non-covalent interactions. However, the structural polymorphism of the bioinspired self-assemblies poses challenges for their rational design and scale production as sustainable, eco-friendly, and tailorable materials for technology applications. Here, it is demonstrated that peptide polymorphic crystallization is a hierarchical process, evolving from initially flexible, twisted nanofibrils bundling to form ribbons, then ripening to robust, plate-like crystals composed of superhelices, as observed using high-resolution microscopy and crystallography supported by molecular dynamics simulations and quantum mechanical calculations. The hierarchical process accounts for the known morphological diversity of peptide crystals and provides a mechanism of controllably restricting the assembly to create only specific supramolecular structures as demanded. Especially, the superhelical organization enables high-efficiency energy transformation, resulting in tremendous photoluminescent, optical waveguiding, and electromechanical energy-harvesting potential. These findings endorse the feasibility of connecting the bioinspired flexible aggregations and robust crystallizations.