(546a) Protein-Engineered Block Copolymers for Water-Responsive Actuation

Water is ubiquitous on earth and serves as an easy-to-use trigger for stimulus-responsive materials. Natural water-responsive (WR) biological materials are abundant, having independently evolved in places such as wheat awns, pinecones, and bacterial spores. Water-responsive biomaterials are of interest for applications as high-energy actuators, especially in soft robotics. Recent work has shown that β-sheet structure correlates with WR energy density in proteins, but the design parameters for water response in proteins remain poorly understood. Here we design, synthesize, and study CEC protein block-copolymers consisting of two α-helical domains derived from cartilage oligomeric matrix protein coiled-coil (C) flanking an elastin-like peptide domain (E). We characterize the structure of these proteins using circular dichroism spectroscopy and Fourier transform infrared spectroscopy. We use these protein materials to create water-responsive actuators whose energy densities outperform mammalian muscle by two orders of magnitude and match reported spider silk actuators, the highest found in nature. To elucidate the effect of structure on water response, CEC was compared to a variant, CEC_L44A, in which the Leu at position 44 in each C domain was mutated to Ala, abolishing any α-helical structure and providing an unstructured control material. Ongoing work focuses on studying the effect of the percentage α-helicity on WR energy density in order to develop design parameters for water-responsive biomaterials.