| Natural materials, such as the muscle protein titin, have generated great interest due to their extraordinary strength, toughness and elasticity, currently unmatched in synthetic materials. The specific aim of this dissertation was to address this challenge by designing biopolymers possessing precise higher-ordered complexity inherent in proteins for combined strength and toughness. Such materials have a wide range of potential applications in biomedical research. Our method involved an interdisciplinary approach that merged molecular dynamics, chemical biology and materials science. First, proteins were analyzed by steered molecular dynamics (SMD) to determine their potential as mechanically resistant modular domains. SMD simulations provide a means of measuring the relative mechanical stability of a protein under an applied force, analogous to atomic force microscopy single-molecule experiments, prior to actual protein synthesis. Second, upon identification of mechanically stable proteins, genetic engineering and protein engineering techniques, coupled with chemical functionalization, were used to obtain linear biopolymers with precisely controlled polymer chain length, composition, sequence, and stereochemistry. Using bacterial expression systems to synthesize the biopolymers offers a unique advantage over chemical synthesis in the ability to control these properties, making it feasible to readily fine tune the materials for select applications. Finally, single-molecule force spectroscopy (SMFS) experiments and nano-mechanical studies were performed to probe the effect of forces applied to the macromolecules, and to further study their structure-property relationships. SMFS has become an invaluable tool in the field of biophysics and supramolecular chemistry, yielding vital information on the secondary interactions of the macromolecules at the single-molecule level, and revealing potential mechanisms of unfolding under an applied force. |
