Elastin is nature's most abundant elastomer. It is the durable, self-assembling protein that is responsible for the elasticity of skin, veins, arteries and lungs. It has stimulated the design of proteins that perform a variety of functions that include protein purification, targeted drug delivery, matrices for tissue engineering and hydrogels with strain-dependent conductivities. The goal of this project is to understand the principles that account for elastin's mechanical properties and to use this knowledge to design new elastomeric materials with properties that can be optimized for a particular use. To achieve this, this project spans three academic disciplines (chemistry, physics and mechanical engineering) and uses a range of contemporary methodologies including spectroscopy, structural biology and materials characterization. This provides a multidisciplinary training environment for three graduate and four high school students at the University of Louisville and the City College of New York. Both institutions draw on students from urban locations with significant percentages of minority undergraduates.
The objectives of this research are to understand the principles that account for elastin's essential property, recoil, and to design new elastomers. We will apply a combination of NMR and thermo-mechanics to natural elastin and to expressed polyproteins that mimic elastin's modular structure, (HX)n, where H and X are hydrophobic and cross-link modules. To simplify NMR and mutational studies, expressed proteins have modules with repeat sequences based on naturally occurring quasi-repeats. To study stretch induced solvent ordering at the protein surface, we use MQ NMR, and to study stretch induced ordering of the protein, we measure NMR relaxation times and residual shielding anisotropies at labeled sites in the protein backbone. To characterize macroscopic properties, the Young's modulus and the free energy or entropy of stretch will be measured thermo-mechanically and these are related to the NMR studies with statistical mechanical modeling to guide the design of new elastomers with altered sequences. Three graduate and four high school students will be trained and introduced to contemporary techniques that span physics, chemistry and engineering.
