Existence of various structural zones in keratinous tissues revealed by X-ray microdiffraction

Keratinous tissues play two major roles in the adaptation of vertebrates to their environment: a strong mechanical support and a chemical barrier. In order to determine whether these properties may originate from different zones in the tissues, microdiffraction experiments on the micrometre scale have been carried out on feather shaft, horse and human hair, and porcupine quill samples. The existence of several structural layers has been revealed in all the tissues, some corresponding to highly ordered α- or β-type keratin and the others to more or less amorphous keratin. The existence of lipid granules has also been evidenced, mainly in the outer layers. This study shows one of the possibilities which are now offered by third-generation synchrotron sources for the structural microanalysis of biological tissues.