Unraveling double stranded ?-helical coiled coils: An x-ray diffraction study on hard ?-keratin fibers

Kreplak, Laurent; Doucet, J.; Briki, Fatma

doi:10.1002/1097-0282(20010415)58:5<526::aid-bip1028>3.0.co;2-l

Cited by 50 publications

(54 citation statements)

References 31 publications

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“…Due to the need in textile industry, intensive studies have examined this class of proteins from the 1930s onwards [7][8][9][10][11] , aiming at understanding the explaining the mechanical behavior of keratinbased fibers and the link between the structural change and the mechanical properties. As a result of experimental work, several deformation models were proposed to interpret the shape of stressstrain curves, and to correlate with the fiber structure to explain the mechanical behavior of keratin fibers [12][13][14][15][16][17][18][19][20][21] .…”

Section: Introductionsupporting

confidence: 81%

Mechanics of trichocyte alpha-keratin fibers: Experiment, theory, and simulation

et al. 2015

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ABSTRACT:The mechanical behavior of human hair is determined by interaction of trichocyte alpha keratin protein, matrix and disulfide bonds crosslinking between alpha-keratin and matrix. Much effort has been spent to understand the link between the microscopic structure and the macroscopic fiber properties. Here we apply a mesoscopic coarse-grained model of the keratin macrofilament fibril and an analytical solution based on the concept of entropic hyperelasticity of the protein helix to investigate the link between the microscopic structure and the macroscopic properties of keratin fibres. The mesoscopic model provides good agreement with a wide range of experimental results. Based on the mesoscopic model, the predicted stress-strain curve of hair fibers agrees well with our own experimental measurements. The disulfide crosslink the microfibril-matrix and matrix-matrix contributes to the initial modulus and provides stiffening at larger deformation of trichocyte keratin fibers. The results show that the disulfide bonds reinforce the macrofilament and enhance the robustness of the macrofilament by facilitating the microfilaments to deform cooperatively. The availability of a mesoscopic model of this protein opens the possibility to further explore the relationship between microscopic chemical structure and macroscopic performance for a bottom-up description of soft materials.

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Section: Introductionsupporting

confidence: 81%

Mechanics of trichocyte alpha-keratin fibers: Experiment, theory, and simulation

et al. 2015

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“…Figure 6B shows atomistic-level details of the a-b transition process, illustrating the mechanisms by which beta-sheet are formed due to uncoiling of pairs of alpha-helical domains (results shown for the right part of the 1A segment). The a-b transition as observed here has also been observed in experiment, where it was shown that the secondary structure of double-stranded coiled coil proteins gradually transform into beta-sheets under applied tensile load [34,41,42]. Figure 7A shows the structural characteristics of the tetramer under tensile deformation, showing molecular structure snapshots as the tetramer is being stretched.…”

Section: Multi-scale Deformation and Failure Mechanismssupporting

confidence: 65%

“…4A agree closely with experimental modulus measurements in bending. We find that large deformation of both the dimer and the tetramer is accompanied by an a-b transition, a phenomenon that has been observed for other long coiled-coil protein filaments such as a-keratin IF fibers [39,41,42], myosin [37] and IF hagfish slime threads [6,34]. Our results further suggest that the hierarchical makeup of IFs is elementary in defining their characteristic mechanical properties through a cascaded activation of deformation mechanisms, each associated with a specific level of filament strain as shown in Table 1.…”

Section: Discussionmentioning

confidence: 99%

Hierarchical Structure Controls Nanomechanical Properties of Vimentin Intermediate Filaments

Buehler

Qin

2010

ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology

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Intermediate filaments (IFs), in addition to microtubules and microfilaments, are one of the three major components of the cytoskeleton in eukaryotic cells, playing a vital role in mechanotransduction and in providing mechanical stability to cells. Despite the importance of IF mechanics for cell biology and cell mechanics, the structural basis for their mechanical properties remains unknown. Specifically, our understanding of fundamental filament properties, such as the basis for their great extensibility, stiffening properties, and their exceptional mechanical resilience remains limited. This has prevented us from answering fundamental structure-function relationship questions related to the biomechanical role of intermediate filaments, which is crucial to link structure and function in the protein material's biological context. Here we utilize an atomistic-level model of the human vimentin dimer and tetramer to study their response to mechanical tensile stress, and describe a detailed analysis of the mechanical properties and associated deformation mechanisms. We observe a transition from alpha-helices to beta-sheets with subsequent interdimer sliding under mechanical deformation, which has been inferred previously from experimental results. By upscaling our results we report, for the first time, a quantitative comparison to experimental results of IF nanomechanics, showing good agreement. Through the identification of links between structures and deformation mechanisms at distinct hierarchical levels, we show that the multi-scale structure of IFs is crucial for their characteristic mechanical properties, in particular their ability to undergo severe deformation of <300% strain without breaking, facilitated by a cascaded activation of a distinct deformation mechanisms operating at different levels. This process enables IFs to combine disparate properties such as mechanosensitivity, strength and deformability. Our results enable a new paradigm in studying biological and mechanical properties of IFs from an atomistic perspective, and lay the foundation to understanding how properties of individual protein molecules can have profound effects at larger length-scales.

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“…12c shows schematically the a-helix to b-sheet transition in stretched a-keratin fibers (black arrows indicate tensile loading), in which the hydrogen bonds are reformed. X-ray diffraction patterns and spatial infrared microspectroscopy of horse hair [103,113] indicate that the process includes the progressive unraveling of the a-helical coiled coil domains, the refolding of the stretched a-helices into b-sheets, and the spatial expansion of the b-structured zones. The tensile stress-strain curve (Fig.…”

Section: Two-phase Model For A-keratinmentioning

confidence: 94%

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Wang

Yang

McKittrick

et al. 2016

Progress in Materials Science

617

474

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a b s t r a c tA ubiquitous biological material, keratin represents a group of insoluble, usually high-sulfur content and filament-forming proteins, constituting the bulk of epidermal appendages such as hair, nails, claws, turtle scutes, horns, whale baleen, beaks, and feathers. These keratinous materials are formed by cells filled with keratin and are considered 'dead tissues'. Nevertheless, they are among the toughest biological materials, serving as a wide variety of interesting functions, e.g. scales to armor body, horns to combat aggressors, hagfish slime as defense against predators, nails and claws to increase prehension, hair and fur to protect against the environment. The vivid inspiring examples can offer useful solutions to design new structural and functional materials.Keratins can be classified as a-and b-types. Both show a characteristic filament-matrix structure: 7 nm diameter intermediate filaments for a-keratin, and 3 nm diameter filaments for b-keratin.Both are embedded in an amorphous keratin matrix. The molecular unit of intermediate filaments is a coiled-coil heterodimer and that of b-keratin filament is a pleated sheet. The mechanical response of a-keratin has been extensively studied and shows linear Hookean, yield and post-yield regions, and in some cases, a high reversible elastic deformation. Thus, they can be also be considered 'biopolymers'. On the other hand, b-keratin has not been investigated as comprehensively. Keratinous materials are strain-rate sensitive, and the effect of hydration is significant.Keratinous materials exhibit a complex hierarchical structure: polypeptide chains and filament-matrix structures at the nanoscale, Progress in Materials Science 76 (2016) 229-318 Contents lists available at ScienceDirect Progress in Materials Sciencej o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p m a t s c i organization of keratinized cells into lamellar, tubular-intertubular, fiber or layered structures at the microscale, and solid, compact sheaths over porous core, sandwich or threads at the macroscale. These produce a wide range of mechanical properties: the Young's modulus ranges from 10 MPa in stratum corneum to about 2.5 GPa in feathers, and the tensile strength varies from 2 MPa in stratum corneum to 530 MPa in dry hagfish slime threads. Therefore, they are able to serve various functions including diffusion barrier, buffering external attack, energy-absorption, impact-resistance, piercing opponents, withstanding repeated stress and aerodynamic forces, and resisting buckling and penetration.A fascinating part of the new frontier of materials study is the development of bioinspired materials and designs. A comprehensive understanding of the biochemistry, structure and mechanical properties of keratins and keratinous materials is of great importance for keratin-based bioinspired materials and designs. Current bioinspired efforts including the manufacturing of quill-inspired aluminum composites, animal horn-inspired SiC composites, and feather-i...

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Unraveling double stranded ?-helical coiled coils: An x-ray diffraction study on hard ?-keratin fibers

Cited by 50 publications

References 31 publications

Mechanics of trichocyte alpha-keratin fibers: Experiment, theory, and simulation

Mechanics of trichocyte alpha-keratin fibers: Experiment, theory, and simulation

Hierarchical Structure Controls Nanomechanical Properties of Vimentin Intermediate Filaments

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

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