The Post-Yield Region and the Structure of Keratin

Feughelman, M.

doi:10.1177/004051756403400609

Cited by 26 publications

(3 citation statements)

References 15 publications

(12 reference statements)

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“…For simplicity in referring to these material properties, the initial stiff portion of the stress-strain curve is termed the 'Hookean' region, due to its linear elastic response. Following the Hookean region is the plateau-like, or 'yield' region, so called due to the zone of apparent yield that precedes it, a convention used previously (Feughelman, 1964) to describe the similar response to strain found in hard alpha-keratin (Fig.·2). Although similar responses to strain are generated in both materials, significant differences in mechanical parameters exist between WECB and hard alpha-keratin.…”

Section: Introductionmentioning

confidence: 99%

Reversibly labile, sclerotization-induced elastic properties in a keratin analog from marine snails: whelk egg capsule biopolymer (WECB)

Rapoport

Shadwick

2007

Journal of Experimental Biology

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SUMMARY Egg capsules from two caenogastropod whelks, Busycon canaliculatumand Kelletia kelletii, were studied to investigate the genesis of mechanical properties of nascent capsules and to formulate a biomechanical model of this material. Scanning electron microscopy revealed that the capsules possess fibrous hierarchical arrangements at all stages during processing while the mechanical integrity is developing. This suggests that an as yet uncharacterized sclerotization mechanism occurring in the ventral pedal gland primarily binds these fibrous components together. Decomposing the mechanical behavior of WECB through various physical and chemical treatments led us to develop a model for the structure and mechanical properties of this material that supports its designation as a keratin analog. Keratin mechanical models were applied to WECB in its representation as an intermediate state between matrix-free intermediate filament (IF)-type proteins and the more complex composite materials incorporating IFs such as keratin.

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Section: Introductionmentioning

confidence: 99%

Reversibly labile, sclerotization-induced elastic properties in a keratin analog from marine snails: whelk egg capsule biopolymer (WECB)

Rapoport

Shadwick

2007

Journal of Experimental Biology

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“…The cluestion whether this effect is due to increased accessibility or to changes in stress relaxation hehavior must remain unanswered at this time. It is known that a reduction of disulfide content reduces the stress necessary to maintain equilibrium between the a and configuration in an extended wool fiber ( 3,5,6 ] . I t appears obvious, however, that the effect of f ree SH groups is a catalytic one on the interchange hetween disulfide & d q u o ; cross links, which occurs under stress as Mason suggested recently 1151.…”

Section: Methodsmentioning

confidence: 99%

“…10. Extension at turn-over point of reduced BA Fleece wool fibers in buffer pH 6.98 + NEMI. respondingly low and high water contents, then it is conceivable that certain regions of the matrix exist in a glassy state.…”

Section: Methodsmentioning

confidence: 99%

A Transition Temperature in Wool Fibers Under Stress in Relation to Structure

Weigmann

Rebenfeld

Dansizer

1965

Textile Research Journal

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The temperature dependence of the mechanical properties of wool fibers was investigated in relation to sulfhydryl concentration and disulfide bond decrease. It was shown that only the highest level of modification (200 μ mole SH/g) influences the properties in the Hookean and yield regions. This effect could be assigned partly to the increase in SH content and partly to the decrease in disulfide content. In the post-yield region. the influence of chemical modification was much more pronounced and became evident even at the lower levels of fiber modification.The "turn-over point" between the yield and post-yield regions underwent a transition at 72° C for the untreated fibers. The transition temperature was found to be strongly dependent upon the SH content, decreasing with increasing sulfhydryl concentration. In the absence of SH groups, the transition temperature was increased to approximately 85° C and was independent of the disulfide content. This transition is discussed in terms of the stability of the disulfide bond, which is closely connected with the probability of an interchange between disulfide bonds and SH groups. It is suggested that the transition indicates the onset of a chemical flow region in the matrix rather than a glass transition as proposed by other workers.

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Natural protein fibers

Feughelman

2001

J of Applied Polymer Sci

122

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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.

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The Post-Yield Region and the Structure of Keratin

Cited by 26 publications

References 15 publications

Reversibly labile, sclerotization-induced elastic properties in a keratin analog from marine snails: whelk egg capsule biopolymer (WECB)

Reversibly labile, sclerotization-induced elastic properties in a keratin analog from marine snails: whelk egg capsule biopolymer (WECB)

A Transition Temperature in Wool Fibers Under Stress in Relation to Structure

Natural protein fibers

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