X-rays interact strongly with biological organisms. Synchrotron radiation 
sources deliver very intense X-ray photon fluxes within micro- or submicro 
cross-section beams, resulting in doses larger than the MGy. The relevance of 
synchrotron radiation analyses of biological materials is therefore questionable 
since such doses, million times higher than the ones used in radiotherapy, can 
cause huge damages in tissues, with regard to not only DNA, but also proteic and 
lipid organizations. Very few data concerning the effect of very high X-ray 
doses in tissues are available in the literature. We present here an analysis of 
the structural phenomena which occur when the model tissue of human hair is 
irradiated by a synchrotron X-ray micro-beam. The choice of hair is supported by 
its hierarchical and partially ordered keratin structure which can be analysed 
inside the tissue by X-ray diffraction. To assess the damages caused by hard 
X-ray micro-beams (1 microm(2) cross-section), short exposure time scattering 
SAXS/WAXS patterns have been recorded at beamline ID13 (ESRF) after various 
irradiation times. Various modifications of the scattering patterns are 
observed, they provide fine insight of the radiation damages at various 
hierarchical levels and also unexpectedly provide information about the 
stability of the various hierarchical structural levels. It appears that the 
molecular level, i.e. the alpha helices which are stabilized by hydrogen bonds 
and the alpha-helical coiled coils which are stabilized by hydrophobic 
interactions, is more sensitive to radiation than the supramolecular 
architecture of the keratin filament and the filament packing within the keratin 
associated proteins matrix, which is stabilized by disulphide bonds.