Mechanical, infrared, and x-ray data all indicate the presence of a water-impenetrable phase in a-keratin fibers consisting of 25-30% of the whole dry fiber structure. This phase corresponds to the ordered two-strand α-helical ropes formed by the interaction of hydrophobic bonds between α-helices. Coulombic interactions "protected" from the action of water by the hydrophobic bonds further stabilize the α-helical ropes, which form the crystalline α-helical structure of the microfibrils.
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