Laboratoire de Physique des Solides - UMR 8502

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Intermediate filaments in hair

Hair fiber is a biological composite material mainly composed of keratin embedded in a peptide-matrix. Keratin is the intermediate filament (IF) specific of hair and skin. IFs are the main mechanical supports of their specific host tissues : keratin in hair and skin, desmin in muscle for example.
Using X-ray diffraction we can reveal the structure of keratin molecules inside hair and monitor the impact of physical or chemical treatments on the molecular structure. For example hereafter we can see how the molecule and their assemblies are changing their structure during stretching or heating the whole fiber : for this study a combined study with imaging-IR and X-ray synchrotron techniques after mechanical (Kreplak 2004).

On the top images, two WAXS patterns from hard keratin in horsehair :alpha-keratin with a fine 0.52-nm arc from coiled coil molecules, and beta-keratin from horsehair stretched to 100% extension in steam. With 0.333-nm from beta sheets. The down images show absorption IR-maps of the 1631 cm-1 peak from beta-sheets in a horsehair sections stretched to 20, 40, and 60%. In green is the region rich in alpha-helices and in red is the region containing beta-sheets. We see the spatial distribution of the molecular structures during stretching.

Another example is shown below where cell differentiation and hair growth are presented in a model built from monitoring keratin organization (Er-rafik 2006).