Hydration‐Induced β‐Sheet Crosslinking of α‐Helical‐Rich Spider Prey‐Wrapping Silk
Abstract
Due to its moderate strength (≈700 MPa) and impressive extensibility before breaking (≈60–80%), orb‐weaving spider aciniform (AC) prey‐wrapping silks are actually the toughest of the spider silks but are remarkably understudied. The previous results indicate that native AC silk fibers are an α‐helix rich coiled‐coil/β‐sheet hybrid nanofiber, and that conversion of disordered or helical domains to β‐sheet aggregates is surprisingly minimal and overall β‐sheet content is low (≈15%). In this work, it is demonstrated through scanning electron microscopy that native AC silk fibers undergo matted cross‐linking upon exposure to moisture that increases silk stiffness. The unique molecular mechanism of water‐induced cross‐linking is revealed with solid‐state NMR (SSNMR) methods; water‐induced morphological changes are correlated with an increase in AC silk protein β‐sheet content, and additionally a minor unfolding of coiled‐coil regions is observed. Continued and increased β‐sheet cross‐linking is observed upon application of mechanical shear. The size of these β‐sheet domains to be 4–6 nm using Wide‐Line Separation SSNMR is determined. The observation that merely water treatment can be used to convert a protein‐based material from a flexible/extensible α‐helix‐rich fiber to a rigid crossed‐linked β‐sheet mat is a novel observation that should provide new avenues in bioinspired materials design.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jan 04, 2021
- Source ID
- 10.1002/adfm.202007161
Entities
People
- David Onofrei
- Dillan Stengel
- George Youssef
- Gregory Holland
- J. Bennett Addison
- Nha Uyen Huynh
Organizations
- Army Research Office
- Bioenergy Technologies Office
- National Renewable Energy Laboratory
- Office of Energy Efficiency and Renewable Energy
- San Diego State University
- United States Department of Defense
- United States Department of Energy