1 research outputs found
Unraveling the Molecular Requirements for Macroscopic Silk Supercontraction
Spider dragline silk is a protein
material that has evolved over
millions of years to achieve finely tuned mechanical properties. A
less known feature of some dragline silk fibers is that they shrink
along the main axis by up to 50% when exposed to high humidity, a
phenomenon called supercontraction. This contrasts the typical behavior
of many other materials that swell when exposed to humidity. Molecular
level details and mechanisms of the supercontraction effect are heavily
debated. Here we report a molecular dynamics analysis of supercontraction
in <i>Nephila clavipes</i> silk combined with <i>in
situ</i> mechanical testing and Raman spectroscopy linking the
reorganization of the nanostructure to the polar and charged amino
acids in the sequence. We further show in our <i>in silico</i> approach that point mutations of these groups not only suppress
the supercontraction effect, but even reverse it, while maintaining
the exceptional mechanical properties of the silk material. This work
has imminent impact on the design of biomimetic equivalents and recombinant
silks for which supercontraction may or may not be a desirable feature.
The approach applied is appropriate to explore the effect of point
mutations on the overall physical properties of protein based materials