Elucidating the Molecular and Hierarchical Structure of Spider Silk

Elucidating the Molecular and Hierarchical Structure of Spider Silk Elucidating the Molecular and Hierarchical Structure of Spider Silk Overview A single orb-weaving spider produces up to 6 different types of biopolymer fibers that we commonly call silk. These silk fibers produced by spiders are protein-based biopolymers and span a large range of physical and mechanical properties. To date, we do not have a complete picture of the molecular and hierarchical protein structures responsible for the high-performance mechanical properties of spider silks. The critical component of spider silk fibers is the fact that they are almost completely protein based, and clearly contain a complex set of secondary protein structures, nanocrystalline domains and hierarchical organizations of these molecular level structures. Understanding the molecular structure and the hierarchical organizations in spider silk proteins is critical to the ultimate goal of producing a protein-based material with properties similar to natural spider silk fibers. Our research group plans to explore the molecular structure, protein-protein interactions, and hierarchical structures formed in major and minor ampullate silk proteins (dragline and web-building). Our ultimate goal is to establish relationships between hierarchical structure and mechanical function in a variety of natural silk proteins from several evolutionarily different spiders, including orb-weaving (Araneus), cob-weaving (Latrodectus) and jumping (Peucetia) spiders. Intellectual Merit Determining molecular and hierarchical structures in spider silk proteins will primarily be done using a combination of x-ray diffraction (XRD) and solid-state Nuclear Magnetic Resonance (ssNMR) techniques. Pair distribution function (PDF) measurements using fiber XRD will further be developed to characterize the nano-structures and short-range amorphous structures in oriented spider silk fibers. To further elucidate hierarchical ordered structures in spider silk fibers, small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) will be employed. XRD will be combined with ssNMR to provide a more complete picture of the molecular structure of spider silk fibers. 2D/3D proton-carbon-nitrogen homo- and hetero-nuclear NMR experiments will be used to determine through bond and through space correlations. Also, ultrafast magic angle spinning (MAS) and advanced 1H homonuclear decoupling NMR should allow for complete assignment of spider silk spectra and elucidate all secondary structure elements in spider silk fibers that have been isotopically (13C/15N) enriched. Furthermore, we will use our recently developed 2H/13C 2D NMR techniques to interrogate the molecular dynamics of spider silk proteins. All together, these studies should produce an unprecedented level of detail into the molecular and hierarchical structures of natural spider silk fibers. Broader Impacts Our long-term goal is to duplicate spider silk fiber properties in synthetic biopolymers. A first critical step in this process is understanding the structure-function relationships in natural spider silk fibers. The proposed work will develop a more complete understanding of the structural and hierarchical design in several natural spider silk fibers. The proposed research project will involve scientists from Arizona State University (ASU) and Argonne National Laboratory (ANL). This multi-institutional and multi-disciplinary research will expose graduate, undergraduate and high school students to modern transdisciplinary research and modern communication and teamwork tools for building and maintaining research across multiple labs and institutes. The research team will be exposed to scientific research and instrumentation at ASU and ANL. Our collaborative research group will also participate in Science and Engineering Experience (SCENE) for high school students (scene.asu.edu). Specific emphasis will be placed on outreach to underrepresented Hispanic and Native American schools, which is an institutional initiative at ASU. Keywords Hierarchical Structures, Spider Silk, X-ray Diffraction, NMR Spectroscopy, Protein-Based Biopolymers