Probing the Molecular Structure and Dynamics of Spider Silk Proteins

Arizona State University, Scottsdale AZ

Investigators

Abstract

ID: MPS/DMR/BMAT(7623) 1264801 PI: Yarger, Jeffrey ORG: Arizona State University Title: Probing the Molecular Structure and Dynamics of Spider Silk Proteins Technical: Spiders produce a variety of proteins, which are pulled into silk fibers possessing mechanical properties that can outperform other natural and synthetic fibers. A full molecular level understanding of the physical properties of these fibers has not yet been achieved. The fibers contain a complex set of secondary protein structures and nanocrystalline domains. The PI will explore the molecular structure and protein-protein dynamics of major and minor ampullate silk proteins (dragline and web-building), cylindrical silk proteins (also named tubuliform, used for egg case) and aciniform silk proteins (prey wrapping). The ultimate goal is to establish relationships between structural features and mechanical function in a variety of natural silk proteins from several different spiders, including orb-weaving (Nephila and Argiope) and cobweaving (Latrodectus hesperus) spiders. Elucidation of molecular structure will primarily be carried out using multidimensional solid-state NMR (ssNMR) techniques. Use of 13C, 15N and 1,2H isotopically enriched silks will allow 2D/3D carbon and nitrogen homo- and heternuclear NMR experiments to determine extensive through-bond and through-space correlations. These techniques, along with ultrafast magic angle spinning (MAS) and advanced 1H homonuclear decoupling, should allow for complete assignment of spider silk spectra and elucidate all secondary structure elements in these biopolymers. Pair distribution functions (PDF) obtained from fiber x-ray and neutron diffraction will further be developed to characterize the nano-structures and short-range amorphous structures in oriented spider silk fibers. The PI will also develop and use 2H/13C 2D NMR techniques to interrogate molecular dynamics of spider silk proteins. Taken together, these studies should produce an unprecedented level of detail regarding the molecular structure and dynamics of natural spider silk fibers. Non-Technical: Spiders produce various protein-based polymers that we call silk. Understanding silk at a molecular level is critical to utilizing this material and reverse engineering its properties. The ability to duplicate spider silk properties in man-made protein-based materials is the key to using these high-performance biopolymers in 'real-world' applications. A first step in this process is giving engineers the molecular level detailed information about the structure and dynamics in the natural material in order to reproduce this in recombinant or synthetic constructs. The proposed project will develop new understandings into the structural design of several natural spider silks. Accomplishment of the objectives outlined above will provide new methodologies to determine protein fiber structures and correlate these structures with mechanical properties as well as provide broad training in molecular structure analysis to students. These research projects will involve a student research team consisting of graduate, undergraduate, and high-school students. The research team will be exposed to scientific research and instrumentation at both Arizona State University and Argonne National Laboratory. The research group will also participate in NSF sponsored K-12 teacher summer research programs and will provide demonstrations of spider silk research to local area K-12 schools. Specific emphasis will be placed on outreach to underrepresented Hispanic and Native American schools and neighborhoods.