In the field of biomimetics, spider silk is a very attractive material for medical, textile, defense and construction applications due to a host of impressive mechanical properties rivaling (and in some cases exceeding) man-made materials as well as the potential for greener polymer chemistry. Presently, however, synthetic spider silk fibers derived from recombinant proteins have disappointing mechanical properties, far inferior to their native counterparts. Much of the problem lies in the poorly understood molecular and nanoscale fiber assembly mechanisms for the large (&gt;300 kDa) spider silk protein components and their conversion into fibers. We have applied a multi-technique approach to probe the nascent stages of spider silk assembly to better understand the biochemical mechanisms and triggers responsible for spider silk formation. Combining results from solution NMR (nuclear magnetic resonance), DLS (dynamic light scattering), cryo-TEM (cryogenic transmission electron microscopy) tomography, and coarse grain molecular dynamics simulations, we have produced a model for the early folding and organization of spider silk proteins. Spider silk protein fibroins (spidroin) assemble into hierarchical structures on the order of 200-300 nm comprised of approximately 300 silk protein monomers. These discreet micelle-like nanoparticle structures are an assembly of highly disordered (random coil) silk proteins until the application of shear force to the solution, upon which distinct fiber-like substructures appear within the larger parent nanoparticles. We believe that these micelle-like structures are one key to understanding the formation of spider silk and are critical in order to obtain the necessary mechanical properties in the final fibers. Our research team is now exploring the conditions which stabilize these particles with the goal of spinning fibers from native dope solutions. In this presentation we will report on recent protein solution NMR studies to determine the intermolecular interactions and dynamic processes responsible for silk protein nanoparticle formation, stabilization and further processing into fibers.

NMR characterization of spider silk protein nanoparticle pre-assemblies

2019 Fall National Meeting

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