Structure and biochemistry of mammalian hard keratin

Marshall, Robert C.; Orwin, D.F.G.; Gillespie, J. M.

doi:10.1016/0892-0354(91)90016-6

Cited by 240 publications

(194 citation statements)

References 140 publications

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“…2A and Fig. S2) (30). The observed appearance of the IF network is consistent with previous reports on the formation of keratins such as K35 and K85 (32,33), together with high-glycine-tyrosine and highsulfur KAPs in the early zone I, just above the dermal papilla (19).…”

Section: Discussionsupporting

confidence: 80%

“…AFM enables high-resolution images to be recorded without the ultrathin sectioning or staining required for transmission electron microscopy (TEM) (Figs. S2 and S3), which already revealed profound changes in the IF network (29,30). The topographic images were obtained using the peak force quantitative nanomechanical mapping (QNM) mode of the AFM on dried follicles that retain the fibernetwork architecture (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Keratin network modifications lead to the mechanical stiffening of the hair follicle fiber

Bornschlögl

Bildstein

Thibaut

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The complex mechanical properties of biomaterials such as hair, horn, skin, or bone are determined by the architecture of the underlying fibrous bionetworks. Although much is known about the influence of the cytoskeleton on the mechanics of isolated cells, this has been less studied in tridimensional tissues. We used the hair follicle as a model to link changes in the keratin network composition and architecture to the mechanical properties of the nascent hair. We show using atomic force microscopy that the soft keratinocyte matrix at the base of the follicle stiffens by a factor of ∼360, from 30 kPa to 11 MPa along the first millimeter of the follicle. The early mechanical stiffening is concomitant to an increase in diameter of the keratin macrofibrils, their continuous compaction, and increasingly parallel orientation. The related stiffening of the material follows a power law, typical of the mechanics of nonthermal bending-dominated fiber networks. In addition, we used X-ray diffraction to monitor changes in the (supra)molecular organization within the keratin fibers. At later keratinization stages, the inner mechanical properties of the macrofibrils dominate the stiffening due to the progressive setting up of the cystine network. Our findings corroborate existing models on the sequence of biological and structural events during hair keratinization.atomic force microscopy | elastic modulus | human hair follicle | biomechanics | X-ray diffraction B iological tissues are structurally complex materials with remarkable mechanics and elastic moduli that can range from a few pascals to several gigapascals (1-3). An active field aims at understanding how the local structural and mechanical properties of bionetworks define its macroscopic mechanics from a molecular scale toward a cellular and tissue scale (4-6). One challenge is that the properties of these networks have to be considered over multiple length and force scales with macroscopic mechanical forces being transduced from the whole tissue scale down to the cellular and molecular level and vice versa.At the cellular level, the last decades witnessed for a considerable advancement toward a better understanding of how the cytoskeleton composed of actin, microtubules, and intermediate filaments (IFs) determines cellular mechanics (1,(6)(7)(8). In vitro studies on isolated cells (6) and reconstituted in vitro bionetworks with controllable architecture and composition (9-12) considerably advanced our knowledge of cytoskeletal mechanics. However, these models are only approximations of the complex tridimensional architecture of most tissues. At the tissue level, the mechanical anisotropy together with the variety of mechanically different constituents usually hamper direct correlations between network architecture and mechanical properties (3, 13). Analytical models and computer modeling allow to theoretically link the macroscopic mechanical properties of the network with parameters of the local network architecture (5, 14, 15).The human hair follicle was used here...

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Section: Discussionsupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Keratin network modifications lead to the mechanical stiffening of the hair follicle fiber

Bornschlögl

Bildstein

Thibaut

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…In muscles, myosins reaching from bipolar filaments to actin filaments result in contractile muscle functionality. sheets possessing extraordinary hardness 15 . In fibrin and vimentin-like proteins (Fig.…”

Section: Bottom-up Assemblymentioning

confidence: 99%

The role of mechanics in biological and bio-inspired systems

et al. 2015

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Natural systems frequently exploit intricate multiscale and multiphasic structures to achieve functionalities beyond those of man-made systems. Although understanding the chemical make-up of these systems is essential, the passive and active mechanics within biological systems are crucial when considering the many natural systems that achieve advanced properties, such as high strength-to-weight ratios and stimuli-responsive adaptability. Discovering how and why biological systems attain these desirable mechanical functionalities often reveals principles that inform new synthetic designs based on biological systems. Such approaches have traditionally found success in medical applications, and are now informing breakthroughs in diverse frontiers of science and engineering. N atural biological systems are constrained by a limited number of chemical building blocks, yet through practical material organization and mechanics 1 , fulfil the functional needs of diverse organisms by methods that often exceed what is currently achievable using man-made approaches 2 . Synthetic systems are often limited by trade-offs where improving one property comes at the expense of another, as observed when utilizing ceramics in place of metals where a higher elastic modulus is accompanied by lower fracture toughness. However, many natural systems and materials have evolved 3 solutions that result in a number of improved properties simultaneously (for example, high modulus with high fracture toughness), and often produce systems that fulfil multiple functions concurrently. For example, stomatopod dactyl clubs 4 tolerate exceptional amounts of damage through multiphasic material interfaces, and efficient blood-clotting mechanisms are achieved through platelet shape adaptability 5 . These intricate mechanics phenomena, relating material organization and adaptability, are implemented in a structurally minimalistic fashion that is difficult to emulate through artificial manufacturing approaches 6 . Such mechanical functions (that is, mechanofunctionality) of biological systems are not isolated cases-multiscale structural organization also contributes to the hardness of nacre 7 and toughness of toucan beaks 8 , while shape changing commonly drives behaviour in many sea creatures 9 and plants 10 . As such recurrent, mechanically based organizational features throughout biology are discovered and analysed, they provide insight for building exceptional mechanofunctionalities into synthetic, bio-inspired technologies.The survival of organisms is often heightened by structures and materials with favourable properties (for example, load-bearing capacity) or mechanofunctionalities that are passive

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“…Wool fiber characteristics, such as diameter, crimps, and length, are essential parameters of the wool trait, as well as important indications of the spinning efficiency of the wool (Plowman et al, 2009). Previous studies have shown that variations in the protein compositions of the orthocortex and paracortex, which make up nearly the whole wool fiber, were highly related with wool trait parameters (Marshall et al, 1991;Plowman et al, 2000). Particularly, the formation of KAP composites gives the wool special mechanical attributes of strength, inertness, and rigidity (Parry and Steinert, 1992;Plowman, 2003;Plowman et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Polymorphisms of KAP6, KAP7, and KAP8 genes in four Chinese sheep breeds

et al. 2014

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ABSTRACT. High glycine-tyrosine proteins (HGTPs), also known as keratin-associated proteins (KAPs), play a key role in the major structures and mechanical properties of wool fiber. Sheep HGTPs consist of three multigene families: KAP6, KAP7, and KAP8 genes. Polymorphisms of these three genes have been proposed to have important effects on wool fiber traits. The aim of the present study was to identify polymorphisms of the KAP6, KAP7, and KAP8 genes in four sheep breeds, including Chinese Merino superfine wool sheep, Hu sheep, a Merino x Hu crossed breed, and Romney sheep. Polymerase chain reaction (PCR) product direct sequencing, PCR-single-strand conformation polymorphism, and cloned sequencing methods were used to find genetic variation and identify polymorphisms in these genes. The Mutation Surveyor v3.97 software was used to analyze the sequences. These methods revealed six different sequences of the KAP6 gene, two different sequences of the KAP7 gene, and five different sequences of the KAP8 gene. Accordingly, 3439©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (2): 3438-3445 (2014) Polymorphisms of sheep wool keratin-associated protein genes three (with frequencies >1%) single nucleotide polymorphisms (SNPs) of the KAP6 gene, one SNP of the KAP7 gene, and five SNPs of the KAP8 gene were detected. Interestingly, some of these sequences were present in only certain sheep breeds, thereby suggesting that these special allele sequences could be used as candidate genes of wool characteristics in further studies.

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Structure and biochemistry of mammalian hard keratin

Cited by 240 publications

References 140 publications

Keratin network modifications lead to the mechanical stiffening of the hair follicle fiber

Keratin network modifications lead to the mechanical stiffening of the hair follicle fiber

The role of mechanics in biological and bio-inspired systems

Polymorphisms of KAP6, KAP7, and KAP8 genes in four Chinese sheep breeds

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