Nanostructured functional films from engineered repeat proteins.

Fundamental advances in biotechnology, medicine, environment, electronics and energy require methods for precise control of spatial organization at the nanoscale. Assemblies that rely on highly specific biomolecular interactions are an attractive approach to form materials that display novel and useful properties. Here, we report on assembly of films from the designed, rod-shaped, superhelical, consensus tetratricopeptide repeat protein (CTPR). We have designed three peptide-binding sites into the 18 repeat CTPR to allow for further specific and non-covalent functionalization of films through binding of fluorescein labelled peptides. The fluorescence signal from the peptide ligand bound to the protein in the solid film is anisotropic, demonstrating that CTPR films can impose order on otherwise isotropic moieties. Circular dichroism measurements show that the individual protein molecules retain their secondary structure in the film, and X-ray scattering, birefringence and atomic force microscopy experiments confirm macroscopic alignment of CTPR molecules within the film. This work opens the door to the generation of innovative biomaterials with tailored structure and function.