A New Deformation Model of Hard α-Keratin Fibers at the Nanometer Scale: Implications for Hard α-Keratin Intermediate Filament Mechanical Properties

Kreplak, Laurent; Franbourg, A.; Briki, Fatma; Leroy, Frédéric; Dallé, D.; Doucet, J.

doi:10.1016/s0006-3495(02)75572-0

Cited by 72 publications

(64 citation statements)

References 32 publications

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“…This low influence of the IF/KAP disulfide network on the follicle mechanics, despite its extremely high density, is likely a consequence of the immersion in PBS during our experiments. Due to the hygroscopic nature of the KAP matrix, it will swell in water, whereas the IFs show only little water uptake (45), causing a weakening of ionic and H-bond interactions. This swelling could minimize the mechanical contribution of the matrix in our measurements.…”

Section: Discussionmentioning

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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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: Discussionmentioning

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 the case of IFs, the shear modulus cannot be neglected because the filament is built by the longitudinal and lateral interaction of ∼45 nm long rods that have the potential to slide longitudinally past each other. 15,17,28 Hence, a cross-linker such as glutaraldehyde is able to create covalent bonds between adjacent dimer rods that should reduce the amount of sliding. As expected from equation (5), glutaraldehyde-fixed IFs exhibit a significantly higher bending stiffness of ∼900 MPa that, to first (4)).…”

Section: Discussionmentioning

confidence: 99%

“…2 Knowledge about the IF's mechanical properties and their functional role in cells has increased in the last few years thanks to a series of studies mainly performed at the filament network [11][12][13][14] and bundle levels. 15,16 The only studies at the single filament level were done by Mücke, Kreplak, and coworkers. 17,18 Mücke and colleagues used imaging by atomic force microscopy (AFM) to measure the apparent persistence length, λ, of vimentin IFs.…”

Section: Introductionmentioning

confidence: 99%

Exploring the Mechanical Properties of Single Vimentin Intermediate Filaments by Atomic Force Microscopy

Guzmán

Jeney

Kreplak

et al. 2006

Journal of Molecular Biology

Self Cite

102

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Intermediate filaments (IFs), together with actin filaments and microtubules, compose the cytoskeleton. Among other functions, IFs impart mechanical stability to cells when exposed to mechanical stress and act as a support when the other cytoskeletal filaments cannot keep the structural integrity of the cells. Here we present a study on the bending properties of single vimentin IFs in which we used an atomic force microscopy (AFM) tip to elastically deform single filaments hanging over a porous membrane. We obtained a value for the bending modulus of non-stabilized IFs between 300 MPa and 400 MPa. Our results together with previous ones suggest that IFs present axial sliding between their constitutive building blocks and therefore have a bending modulus that depends on the filament length. Measurements of glutaraldehyde-stabilized filaments were also performed to reduce the axial sliding between subunits and therefore provide a lower limit estimate of the Young's modulus of the filaments. The results show an increment of two to three times in the bending modulus for the stabilized IFs with respect to the non-stabilized ones, suggesting that the Young's modulus of vimentin IFs should be around 900 MPa or higher.

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“…X-Ray diffraction studies have revealed that the effect of water must involve a combination of a sliding and molecular stretching process. 7 Indeed, at low humidity, it is well known that the˛-helix !ˇ-sheet transition occurs as a consequence of macroscopic stress. 8 -10 Analogy with less complex, organized materials, such as polymer fibres, shall be considered in this study.…”

Section: Introductionmentioning

confidence: 99%

Nanomechanics of single keratin fibres: A Raman study of the α‐helix →β‐sheet transition and the effect of water

Paquin

Colomban

2006

J Raman Spectroscopy

111

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The use of micro-Raman spectroscopy, through chemical-bond, nano-scale probes, allows the changes in conformations (a-helix → b-sheet), chain orientation, breakage of disulfide bonds (20%) and the increase of intra-and inter-chain distances during the application of stress to be distinguished. The combination of micro-Raman spectroscopy and a Universal Fibre Tester allows a quantitative measurement of the extension of chemical bonds in the peptide chain during loading. The nano-structural transformations of keratin during strain of human hair in a dry environment (40-60% relative humidity) and saturated with water have been studied. Water permits the sliding of the chains and decreases the bond energy of the hair. Spectral analyses and 2D correlation are two coherent and independent methods to follow the structural nano-mechanical (Raman) and micro-mechanical (strain/stress) analyses, and confirm the validity of the experimental results, tools and principles used, as well as the agreement with the structural model of keratin fibres described by Chapman and Hearle.

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A New Deformation Model of Hard α-Keratin Fibers at the Nanometer Scale: Implications for Hard α-Keratin Intermediate Filament Mechanical Properties

Cited by 72 publications

References 32 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

Exploring the Mechanical Properties of Single Vimentin Intermediate Filaments by Atomic Force Microscopy

Nanomechanics of single keratin fibres: A Raman study of the α‐helix →β‐sheet transition and the effect of water

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