Intermicrofibrillar Linkages in α-Keratin Fibers

The mechanical behavior of wool keratin fibers in different solutions of formic acid in water suggests that up to a solution concentration of 70% formic acid in water the microfibrils are intact. The diametral swelling of the fiber to gether with the longitudinal contraction in these solutions is compatible with the presence of intermicrofibrillar linkages spaced at a distance of the order of 10 nm longitudinally along the microfihrils. The behavior in torsion and extension of wet wool fibers with chemically-reduced disulphide contents, and with biologically-increased disulphide content, strongly points to the nonhelical "tails" of the low-sulphur protein fraction in the keratin fiber being involved in the formation of the intermicrofibrillar linkages. The presence of intermicrofihrillar linkages is also supported by the me chanical behavior of wool fibers during the period of the transient of the water front entering a fiber when a dry fiber is exposed to a wet or high humidity environment.