TY - JOUR
T1 - Hierarchical spidroin micellar nanoparticles as the fundamental precursors of spider silks
AU - Parent, Lucas R.
AU - Onofrei, David
AU - Xu, Dian
AU - Stengel, Dillan
AU - Roehling, John D.
AU - Bennett Addison, J.
AU - Forman, Christopher
AU - Amin, Samrat A.
AU - Cherry, Brian
AU - Yarger, Jeffery
AU - Gianneschi, Nathan C.
AU - Holland, Gregory P.
N1 - Funding Information:
ACKNOWLEDGMENTS. We thank Prof. Timothy Baker for access to the instrument, and we thank Dr. James Bower for his assistance with the cryo-TEM experiments. The DLS work was performed with the assistance of David Pullman at SDSU. L.R.P. was supported by the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health under Award F32EB021859. D.O. is supported by an SDSU Graduate Research Fellowship. J.D.R.’s work was performed under the auspices of the US Department of Energy, by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Grants that supported this work include: Department of Defense - Air Force Office of Scientific Research (DOD-AFOSR) FA9550-17-1-0282 (to G.P.H.), DOD Defense University Research Instrumentation Program (DURIP) FA9550-17-1-0409 (to G.P.H.), National Science Foundation - Division of Materials Research - Biomaterials (NSF-DMR-BMAT) 1809645 (to J.L.Y.), and Army Research Office (ARO) Multidisciplinary University Research Initiative (MURI) W911NF-15-1-0568 (to N.C.G.). The cryo-TEM work was performed at the cryo-electron microscopy facility at the University of California, San Diego, which is supported by our colleague Prof. Timothy Baker (University of California, San Diego) and funded by the National Institutes of Health.
Publisher Copyright:
© 2018 National Academy of Sciences. All rights reserved.
PY - 2018/11/6
Y1 - 2018/11/6
N2 - 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. 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. 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 into micrometer-scale silk fibers. 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. 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. 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.
AB - 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. 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. 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 into micrometer-scale silk fibers. 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. 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. 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.
KW - Biomimetic materials
KW - Hierarchical micelles
KW - Natural protein nanostructures
KW - Spider silk formation
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U2 - 10.1073/pnas.1810203115
DO - 10.1073/pnas.1810203115
M3 - Article
C2 - 30348773
AN - SCOPUS:85056080228
VL - 115
SP - 11507
EP - 11512
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 45
ER -