A note on the role of the microfibrils in the mechanical properties of α-keratins

Reassessment of data on the torsional properties of wool fibres extended in water has been made. These measurements taken together with the results on the lateral properties of other α-keratin fibers suggest that the increased stiffness in water produced as a fiber is extended longitudinally from the yield into the post-yield region arises in the microfibrils. Molecular models developed recently from x-ray diffraction data identify along the microfibrils two different zones, whose expected mechanical behavior during extension predict closely the known behavior of α-keratin fibers.