Spider's Silk: From Protein-rich Gland Fluids to Diverse Biopolymer Fibers

Spider's Silk: From Protein-rich Gland Fluids to Diverse Biopolymer Fibers Spider's Silk: From Protein-rich Gland Fluids to Diverse Biopolymer Fibers The ability to synthetically produce spider silk in the laboratory continues to elude researchers. We believe that this is due to a lack of fundamental understanding with regards to the molecular level details involved in converting the isotropic liquid in the spiders gland to an insoluble super fiber with a diverse range of mechanical properties at the spiders spinnerets. This proposal describes a schedule of research designed to elucidate the molecular structure, dynamics and interactions of the silk proteins in the gland fluid and the physical mechanisms and chemistries involved to convert this viscous isotropic liquid to super fibers with unmatched and diverse mechanical properties. The need for such an understanding has been noted in the recent AFOSR funding opportunity, BAA-AFOSR-2012-0001, Natural Materials and Systems section, where an understanding of the underlying mechanisms of natural materials production was noted (pp. 45- 46). We propose to use a combination of nuclear magnetic resonance (NMR) approaches including solid-state NMR, high-resolution NMR spectroscopy and micro-imaging (MRI) techniques in conjunction with X-ray diffraction at Argonne National Laboratory (ANL) to study the various spider silk producing glands in their native state and under various chemical and physical processing conditions such as dehydration, pH, salt concentration gradients and mechanical stress. We will use these approaches to interrogate the structure of the spider silk proteins in the various glands and detect changes in protein folding when the gland is exposed to different processing conditions. In addition to probing structure, we aim to characterize the dynamics of the silk proteins within the glands with a combination of relaxation, nuclear Overhauser enhancement (NOE) and pulse field gradient (PFG) diffusion measurements. We will study the interaction of the various gland fluids with solvents such as water, ionic liquids and hexfluoroisopropanol (HFIP) since, the later has become a popular solvent for dissolving silk proteins for fiber and film production. We plan to move beyond understanding the major ampullate gland fluid and begin studying the other spider silk producing processes that are applied to produce egg case and prey wrap silks (tubuliform and aciniform) and minor ampullate silks. It is our hope that this work will bolster our understanding of the underlying interactions, mechanisms and dynamics at the molecular level for the conversion of solubilized silk proteins to fibers with outstanding and diverse mechanical properties.