| The genetic engineering of protein-based materials has become a powerful tool d by materials scientists, biomedical engineers, and structural biologists. By using genetic engineering, one can design and synthesize polypeptides with predetermined and precisely controlled molecular architectures. The ability to control the molecular weight, sequence, and structure in this manner far surpasses the capabilities of conventional chemical synthesis.;The work described herein is a result of rigorous efforts to develop functional biomaterials with chemical and physical properties derived from vertebrate elastin. The biosynthesis of the polypeptides was a continued effort to perfect a gene concatemerization protocol previously developed for the production of high molecular weight protein polymers. The protein sequences were based on the tetra- (APGG) and pentapeptide (VPGVG) repeats found in native vertebrate elastin. The polypentapeptide has been shown to have an inverse temperature transition that can be adjusted by nonconservative amino acid substitutions in the fourth position. It has also been noted that substitutions in the first and third positions change the mechanical properties of the protein. By combining polypeptide blocks with different inverse temperature transition values due to hydrophobicity differences and different mechanical properties because of amino acid substitutions, amphiphilic polypeptides capable of self-assembly into hydrogels were produced.;The resultant precursor di- and final triblock copolymers based on BAB triblock copolymers in which the A blocks are hydrophilic and the B blocks are hydrophobic, formed structures consisting of a solvent-swollen network of spherical particles (micelles) of the insoluble end block that were linked together through the soluble midblock. Variable temperature 1D and 2D High-Resolution-NMR, Rheology, Differential Scanning Calorimetry, and High Resolution Electron Microscopy techniques were employed for the characterization of the hydrogels in aqueous solution.;Future modifications and applications of these materials in medicine are discussed at the end of this dissertation. |
