Repeat-proteins films exhibit hierarchical anisotropic mechanical properties

Area of Science:

• Materials Science
• Biomaterials Engineering
• Protein Engineering

Background:

• Complex hierarchical structures in materials offer tunable structure-property relationships.
• Self-assembled protein-based materials are emerging as versatile platforms for engineering applications.

Purpose of the Study:

• To investigate the molecular organization and mechanical properties of self-assembled designed repeat-protein films.
• To establish the relationship between the hierarchical structure and the resulting mechanical behavior of these protein films.

Main Methods:

• Wide-angle X-ray diffraction (WAXD) for molecular orientation.
• Small-angle measurements and electron microscopy for morphology.
• Nanoindentation and dynamic mechanical analysis (DMA) for mechanical properties across length scales.

Main Results:

• The designed 18-repeat consensus tetratricopeptide repeat protein (CTPR18) self-assembles into laminar sheet-like structures with through-plane alignment.
• Self-assembly is driven by head-to-tail stacking and dipole-dipole interactions.
• Hierarchical structure predictably influences mechanics from nano- to macroscale, with axial modulus ranging from 2 to 5 GPa.

Conclusions:

• The hierarchical self-assembly of CTPR proteins creates materials with predictable structure-property relationships.
• These protein-based films demonstrate significant potential as a platform for material engineering.
• Understanding and controlling protein self-assembly is key to designing advanced functional materials.