Natural protein fibers

Abstract

Alpha keratin fibers (hairs, wools, quills, and other mammalian appendages) together with fibroin fibers such as silks and spiders webs are all highly extensible fibrous proteins for which the mechanical properties are of primary importance both to the animal from which they originate and their ultimate application by man. Similarly, the collagens are highly inextensible fibrous proteins, which form the major component of mammalian skin and connecting structures such as tendons. All these fibrous proteins are biological polymers of polypeptide chains for which the mechanical and allied physical properties, such as water absorption, relate to both their macrostructure and their molecular and near-molecular structure. Because of both their commercial application and their relatively complex structure at the molecular and near-molecular level, interpretation of the physical properties of ␣-keratin fibers represents the main component of this presentation. The mechanical properties of ␣-keratin fibers are primarily related to the two components of the elongated cortical cells, the highly ordered intermediate filaments (microfibrils) which contain the ␣-helices, and the matrix in which the intermediate filaments are embedded. The matrix consists of globular proteins plus water, the content of the latter being dependent on the fibers environment. The Extended Two-Phase Model (ETPM) has been developed and results in a detailed coverage of the bulk mechanical properties of ␣-helical fibers in terms of their known molecular and near-molecular structure. The inextensible protein fibers, the collagens and fibroins, are also briefly discussed in terms of the relationship between mechanical properties and the structure of these fibers.

Composite Materials from Natural Resources: Recent Trends and Future Potentials

“…The mechanical properties of α-keratin fibres such as hair fibres and wools are primarily related to the two components of the elongated cortical cells, the highly ordered intermediate filaments (microfibrils) which contain the α-helices, and the matrix in which the intermediate filaments are embedded (Feughelman, 2002). Chemical treatment, bleaching and dyeing is known to be one of hair cuticle and cortex damage producing and properties impairing factors (Neste & Shaker, 2001; Lewis, 1989;Wei et al, 2005).…”

Calcification provides mechanical reinforcement to whale baleen α-keratin

“…The structure and mechanical behaviour of conventional a-keratins are well described (Bendit & Feughelman 1968;Hearle 2000). Briefly, wool fibres have an initial tensile modulus (E s ) of about 2 GPa and an extensibility (or strain at fracture) (1 b ) of about 0.50, and these properties are relatively insensitive to hydration levels (Feughelman 2002). By contrast, hydrated preparations of isolated intermediate filaments or bundles in vitro are far softer (E s ¼ 7 MPa) (Fudge et al 2003) and more extensible (1 b ¼ 2.5) (Kreplak et al 2005) than wool, and these values change drastically when the fibres are dried.…”

Keratin made micro-tubes: The paradoxical thermal behavior of cortex and cuticle

“…Cortex contains 30-40% alphahelix, ordered (crystalline) material and the rest made of pretty amorphous (or low Yak @ 262 °C Merino wool @ 262 °C ordered) macromolecules [1,2,3,5], which soften and flow with temperature; the cuticle is made of some beta-sheet arranged protein and amorphous cross-linked material [3,10,16] which not only does not melt, but becomes even more rigid after thermal treatment [17]. These differences in morphology are very likely the reason for the micro-tube formation and explain also why fine fibres, lacking medulla cells, do not transform into tubes by heating.…”

“…It is made of filamentous proteins, the hard alphakeratins [1][2][3]. The keratin fibres have a composite structure, with a core-shell as well as filament-matrix arrangement on various levels of organisation, from the cortex wrapped by cuticle down to the intermediate filament (IF) surrounded by intermediate filament associated proteins (IFAP), also referred to as keratin associated protein (KAP) [1][2][3].…”