New Aspects of the α-Helix to β-Sheet Transition in Stretched Hard α-Keratin Fibers

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

doi:10.1529/biophysj.103.036749

Cited by 215 publications

(199 citation statements)

References 29 publications

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“…The constant band near 1655 cm À1 is assigned to alpha-helical structure. The peak related to the beta sheet conformation was always located between 1610 and 1635 cm À1 [16][17][18][19]. The infrared spectral decomposition of Amide bands of elastin has been previously reported using vibrational spectroscopy [20].…”

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confidence: 68%

FTIR protein secondary structure analysis of human ascending aortic tissues

Bonnier

Rubin

Debelle

et al. 2008

Journal of Biophotonics

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Journal of BIOPHOTONICSThe advent of moderate dilatations in ascending aortas is often accompanied by structural modifications of the main components of the aortic tissue, elastin and collagen. In this study, we have undertaken an approach based on FTIR microscopy coupled to a curve-fitting procedure to analyze secondary structure modifications in these proteins in human normal and pathological aortic tissues. We found that the outcome of the aortic pathology is strongly influenced by these proteins, which are abundant in the media of the aortic wall, and that the advent of an aortic dilatation is generally accompanied by a decrease of parallel b-sheet structures. Elastin, essentially composed of b-sheet structures, seems to be directly related to these changes and therefore indicative of the elastic alteration of the aortic wall. Conventional microscopy and confocal fluorescence microscopy were used to compare FTIR microscopy results with the organization of the elastic fibers present in the tissues. This in-vitro study on 6 patients (three normal and three pathologic), suggests that such a spectroscopic marker, specific to aneurismal tissue characterization, could be important information for surgeons who face the dilemma of moderate aortic tissue dilatation of the ascending aortas.Infrared spectroscopy and imaging was applied to analyse Human thoracic ascending aortas with the aim to highlight the protein secondary structure reorganisation after an aneurism outcome. We used a curve-fitting procedure to visualise modifications in the protein spectral profile where alteration of b structures in pathological aortas could be detected. Our spectroscopic observations on tissue sections corroborated with confocal fluorescence microscopy clearly demonstrating that elastic fibres of aortic wall are strongly altered. Elastin appears as the privileged target during the pathological process.

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confidence: 68%

FTIR protein secondary structure analysis of human ascending aortic tissues

Bonnier

Rubin

Debelle

et al. 2008

Journal of Biophotonics

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“…It is of importance to first understand the mechanical behavior of a-and b-keratins at the nano and microscales, which is summarized in Table 7. The b-sheet has a higher stiffness than a-helix [100], and it has been long recognized that under tensile load the a-helices change the structure into b-pleated sheets [23,[101][102][103]. In addition, mineralization with calcium and other salts can contribute to the hardening of keratins [104].…”

Section: Mechanical Properties Of A-and B-keratinsmentioning

confidence: 99%

“…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: 99%

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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“…This is in agreement with the findings by Fraser et al, in which the microfibril that exists in the cortex region is mainly composed of a-helical protein. 4,11 On the other hand, the amide I peak maxima for the cuticle region (depth of 1 lm from the fiber surface) was found to be at 1672 cm 21 , assigned to the b-sheet and/or random coil forms, but the skeletal CÀ ÀC stretch (a) band, assigned to the a-helical backbone did not appear. Also, the amide III (unordered) band intensity, assigned to the random coil form, at 1250 cm 21 for the cuticle region was higher than that for the cortex region.…”

Section: Raman Spectra Of Virgin Black Human Hair Keratin Fibersmentioning

confidence: 99%

“…The direct characterization of keratin fibers has been performed using X-ray diffraction, 1,[7][8][9][10][11][12] solid state NMR, 8,13 Raman, [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and Infrared spectroscopy. 14,16,17 Information about the amorphous region (the cuticle and matrix) of…”

Section: Introductionmentioning

confidence: 99%

Analysis of internal structure changes in black human hair keratin fibers with aging using Raman spectroscopy

Kuzuhara¹,

Fujiwara²,

Hori³

2007

Biopolymers

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To investigate the internal structure changes in virgin black human hair keratin fibers due to aging, the structure of cross‐sections at various depths of virgin black human hair (sections of new growth hair: 2 mm from the scalp) from a group of eight Japanese females in their twenties and another group of eight Japanese females in their fifties were analyzed using Raman spectroscopy. For the first time, we have succeeded in recording the Raman spectra of virgin black human hair, which had been impossible due to high melanin granule content. The key points of this method are to cross‐section hair samples to a thickness of 1.50‐μm, to select points at various depths of the cortex with the fewest possible melanin granules, and to optimize laser power, cross slit width as well as total acquisition time. The reproducibility of the Raman bands, namely the α‐helix (α) content, the β‐sheet and/or random coil (β/R) content, the disulfide (SS) content, and random coil content of two adjoining cross‐sections of a single hair keratin fiber was clearly good. The SS content of virgin black human hair from the Japanese females in their fifties for the cortex region decreased compared with that of the Japanese females in their twenties. On the other hand, the β/R and α contents of the cortex region did not change. © 2007 Wiley Periodicals, Inc. Biopolymers 87: 134–140, 2007.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

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New Aspects of the α-Helix to β-Sheet Transition in Stretched Hard α-Keratin Fibers

Cited by 215 publications

References 29 publications

FTIR protein secondary structure analysis of human ascending aortic tissues

FTIR protein secondary structure analysis of human ascending aortic tissues

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

Analysis of internal structure changes in black human hair keratin fibers with aging using Raman spectroscopy

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