The original reported method to solubilize recombinant spider silk proteins (rSSp) in an aqueous solution involved using microwaves to quickly generate heat and pressure inside of a sealed vial containing rSSp and water. Several key obstacles exist in their production as well as in their formulation into useable products. The production of recombinant spider silk proteins continues to be a key area of interest for a number of research groups. We find that the established micelle theory of silk fiber precursor storage is incomplete and that the first steps toward liquid crystalline organization during silk spinning involve the fibrillization of nanoscale hierarchical micelle subdomains. Using a combination of solution phase diffusion NMR and cryogenic transmission electron microscopy (cryo-TEM), we reveal direct evidence that the concentrated spidroin proteins are stored in the silk glands of black widow spiders as complex, hierarchical nanoassemblies (~300 nm diameter) that are composed of micellar subdomains, substructures that themselves are engaged in the initial nanoscale transformations that occur in response to shear. Herein we determine the physical form of the natural spidroin precursor nanostructures stored within spider glands that seed the formation of their silks and reveal the fundamental structural transformations that occur during the initial stages of extrusion en route to fiber formation. This is because of an incomplete understanding of the in vivo spidroin-to-fiber spinning process and, particularly, because of a lack of knowledge of the true morphological nature of spidroin nanostructures in the precursor dope solution and the mechanisms by which these nanostructures transform more » into micrometer-scale silk fibers. Myriad approaches have been attempted to prepare artificial silks from recombinant spider silk spidroins but have each failed to achieve the advantageous properties of the natural material. Many natural silks produced by spiders and insects are unique materials in their exceptional toughness and tensile strength, while being lightweight and biodegradable–properties that are currently unparalleled in synthetic materials. Dragline major ampullate silks in both the species contract more than their minor ampullate silks. While both the crystalline and amorphous components lose preferred orientation on wetting with water, the nano-crystallites regain their orientation on wet-restretching, whereas the oriented amorphous components only partially regain their orientation. ![]() Changes in the orientation of β-sheet nanocrystallites and the oriented component of the amorphous network have been determined from wide-angle more » X-ray diffraction patterns. Synchrotron X-ray micro-fiber diffraction experiments have been performed on Nephila clavipes and Argiope aurantia major and minor ampullate dragline spider fibers in the native dry, contracted (by immersion in water) and restretched (from contracted) states. Preferred orientation or alignment of protein chains with respect to the fiber axis is extensively changed during this supercontraction process. Interaction with water causes shrinkage and significant changes in the structure of spider dragline silks, which has been referred to as supercontraction in the literature. (MagLab) Sponsoring Org.: USDOE Office of Science (SC), Basic Energy Sciences (BES) National Science Foundation (NSF) Spain Ministry of Science, Innovation and Universities (MICINN) OSTI Identifier: 1623924 Grant/Contract Number: DMR 10052129 CTQ2010-19501 Resource Type: Accepted Manuscript Journal Name: Nature Communications Additional Journal Information: Journal Volume: 4 Journal Issue: 1 Journal ID: ISSN 2041-1723 Publisher: Nature Publishing Group Country of Publication: United States Language: English Subject: 77 NANOSCIENCE AND NANOTECHNOLOGY 36 MATERIALS SCIENCE Science & Technology - Other = , Publication Date: Research Org.: Florida State Univ., Tallahassee, FL (United States). Florida A & M University, Tallahassee, FL (United States) Florida State Univ., Tallahassee, FL (United States). ![]() Institucio Catalana de Recerca I Estudis Avancats (ICREA), Barcelona (Spain).Florida State Univ., Tallahassee, FL (United States).Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Bellaterra (Spain).
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