Probing the Molecular Structure and Dynamics of Spider Silk Proteins

Probing the Molecular Structure and Dynamics of Spider Silk Proteins Probing the Molecular Structure and Dynamics of Spider Silk Proteins Intellectual Merit Spiders produce a variety of silks with mechanical properties that can outperform other natural and synthetic fibers. A complete picture of the molecular underpinnings responsible for these highperformance materials remains unsolved, even for the most studied dragline silk fibers. The quintessential aspect that is often overlooked in silk is that the majority of this protein-based biopolymer is disordered, but contains several different secondary protein structures and nanocrystalline domains. Understanding the molecular structure and dynamics in spider silks is critical to the ultimate goal of producing a protein-based material with properties similar to natural fibers. We plan to explore the molecular structure of major and minor ampullate silks (dragline and web-building), cylindrical silk (also named tubuliform, used for egg case), aciniform silk (prey wrapping) and piriform silk (attachment disk). Our ultimate goal is to establish relationships between structural and mechanical function in a variety of natural silks from several different spiders, including orb-weaving (Nephila and Argiope) and cobweaving (Latrodectus hesperus, black widow) spiders. Elucidation of molecular structure in spider silk will primarily be done using multidimensional NMR techniques. Using 13C, 15N and 1,2H isotopically enriched silks, will allow 2D/3D carbon and nitrogen homo- and heternuclear NMR experiments for total through bond and through space correlations. These techniques, along with ultrafast 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 function (PDF) measurements on fiber x-ray diffraction and neutron diffraction will further be developed to characterize the nano-structures and short-range amorphous structures in oriented spider silk fibers. Elastic and mechanical properties will be explored using Brillouin and neutron spectroscopy. All together, these studies should produce an unprecedented level of detail into the molecular structure of natural spider silk fibers. Broader Impact 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. Our 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.