Organization of microfibrils in keratin fibers studied by X-ray scattering

Briki, Fatma; Busson, Bertrand; Doucet, J.

doi:10.1016/s0167-4838(98)00216-7

Cited by 60 publications

(81 citation statements)

References 14 publications

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“…All these features are superimposed on a continuously decreasing background signal that is due to other (nonlipid) constituents of the SC. This signal is similar to that observed for hair, another keratinous tissue ( 10 ) ) plotted on a linear scale ( Fig. 2C , black curve) confi rms the peak positions given above.…”

Section: Sample Preparationsupporting

confidence: 87%

Micron-scale assessment of molecular lipid organization in human stratum corneum using microprobe X-ray diffraction

Doucet

Potter

Baltenneck

et al. 2014

Journal of Lipid Research

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This article is available online at http://www.jlr.org complex and specifi c architecture of the inter-corneocyte lipid matrix ( 2 ) composed of a mixture of ceramides, cholesterol, and long-chain fatty acids. Ultrastructural studies, using electron microscopy and diffraction techniques, have revealed that these lipids are organized in stacked bilayers that are predominantly parallel to the skin surface ( 3-5 ). Part of the lipids is covalently bound to the corneocytes whereas another part represents the "free lipids" removable by solvent extraction.X-ray diffraction is an excellent technique for studying the spatial organization of the intercellular matrix because the lipid molecules are highly ordered and oriented in a crystalline structure. This technique has provided a number of important results with regard to the SC structure. In particular, small-angle X-ray scattering (SAXS) gives information on the inter-bilayer distance in the multi-lamellar lipid structures, whereas the wide-angle X-ray scattering (WAXS) data contain information about the in-plane crystalline arrangement of lipids (lattice type).Most of the SAXS studies of human SC fi nd refl ections corresponding to ‫ف‬ 4.5 nm and ‫ف‬ 6.5 nm inter-bilayer spacings ( 4, 6, 7 ). Some studies have also detected a refl ection corresponding to a spacing of 11-13.5 nm ( 6, 8 ), referred to as the "long periodicity phase" ( 6 ). These data indicate that the SC lipid matrix has a complex organization into multiple sublayers or even phase-separated domains with different lamellar repeat distances.Similar complexity is found at the molecular level using WAXS, where two sets of peaks are found, corresponding to orthorhombic (peaks at 0.41 and 0.37 nm) and hexagonal (peak at 0.41 nm) packing of the lipid chains. In addition, a fraction of lipids might exist in a fl uid or amorphous state, which would then contribute to the broad band corresponding to an average distance of 0.46 nm. Abstract Lipid and protein components of the stratum corneum (SC) are organized in complex supramolecular arrangements. Exploring spatial relations between various possible substructures is important for understanding the barrier function of this uppermost layer of epidermis. Here, we report the fi rst study where micro-focus X-ray scattering was used for assessing fi ne structural variations of the human skin barrier with micrometer resolution. We found that the scattering profi les were unchanged when scanning in the direction parallel to the SC surface. Furthermore, small-angle scattering profi les did not change as a function of depth in the SC, confi rming that the lipid lamellar spacings remained the same throughout the SC. However, the wide-angle scattering data showed that the orthorhombic phase was more abundant in the middle layers of the SC, whereas the hexagonal phase dominated in the surface layers both at the external and the lowest part of the SC; i.e., the lipids were most tightly packed in the middle region of the SC. Taken together, our results demonstrate that micro...

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Section: Sample Preparationsupporting

confidence: 87%

Micron-scale assessment of molecular lipid organization in human stratum corneum using microprobe X-ray diffraction

Doucet

Potter

Baltenneck

et al. 2014

Journal of Lipid Research

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“…where S H (Q, a, ∆r, ∆t) is the structure factor for a two-dimensional hexagonal paracrystal [34][35][36][37] with lattice parameter a and distortion parameters ∆r and ∆t. The full model is presented in the supporting information.…”

Section: Observations and Modelmentioning

confidence: 99%

An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

et al. 2016

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This paper presents a detailed analysis of the structure of the hexagonal phase of poly(ferrocenylsilane) (PFS)-based cylindrical micelles found at concentrations above ca. 5 wt. % in non-polar solvents such as decane. Small angle X-ray scattering indicated that the hexagonal order is not long-range. In all samples, deviations in the lower order peak positions were observed with respect to those expected for a perfect hexagonal lattice, with the degree of deviation correlating with the micelle length. Furthermore, analysis of the peak shapes and peak widths suggest that the phase possesses intermediate translational order similar to the hexatic phase. The observed features can be reproduced by amending Hosemann's paracrystal theory to include a distribution of lattice parameters to model well and poorly condensed regions. It is proposed that this distribution arises due to the bending and intertwining of individual micelles in a hexagonal lattice resulting in a kinetically-trapped phase that is initially neither perfectly hexagonal nor canonically hexatic but which anneals over time towards a perfect hexagonal lattice.

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“…The three signals can be modelled by It is well established that when human hair absorbs moisture, the water mostly accumulates in the matrix leading to a displacement of the 90 Å peak to larger distances (matrix swelling) and a decrease of intensity of the 47 and 27 Å peaks due to a loss of contrast between the matrix and IF [5]. So within this scenario, the loss of intensity that we observed for the patients compared with their parents may point towards an increase in water uptake by the matrix of the patients.…”

Section: Model Describing Structure Of the Intermediate Filamentsmentioning

confidence: 99%

Giant axonal neuropathy alters the structure of keratin intermediate filaments in human hair

Soomro

Alsop

Negishi

et al. 2017

J. R. Soc. Interface.

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Giant axonal neuropathy (GAN) follows an autosomal recessive genetic inheritance and impedes the peripheral and central nervous system due to axonal swellings that are packed with neurofilaments. The patients display a number of phenotypes, including hypotonia, muscle weakness, decreased reflexes, ataxia, seizures, intellectual disability, pale skin and often curled hair. We used X-ray diffraction and tensile testing to determine potential changes to the structure of keratin intermediate filaments (IFs) in the hair of patients with GAN. A statistically significant decrease in the 47 and the 27 Å diffraction signals were observed. Tensile tests determined that the hair was slightly stiffer, stronger and more extensible in GAN patients. These results suggest that the structure of keratin IFs in hair is altered in GAN, and the findings are compatible with an increased positional disorder of the keratin tetramers within the hair fibres.

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Organization of microfibrils in keratin fibers studied by X-ray scattering

Cited by 60 publications

References 14 publications

Micron-scale assessment of molecular lipid organization in human stratum corneum using microprobe X-ray diffraction

Micron-scale assessment of molecular lipid organization in human stratum corneum using microprobe X-ray diffraction

An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

Giant axonal neuropathy alters the structure of keratin intermediate filaments in human hair

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