Abstract
The dielectric method has been applied to study the relaxation mechanisms of non-irradiated and gamma-irradiated keratin-water systems in the electric field frequency range of 10(1)-10(5) Hz and at temperatures from 22 to 190 degrees C. Measurements were performed for keratin samples containing 3% water by mass at room temperature. The doses of gamma-irradiation were 5, 50 and 200 kGy. The influence of water and gamma-irradiation on the dielectric behaviour of keratin was negligible up to 120 degrees C but significant in the temperature range of 140-190 degrees C. In the first temperature range, the motion of polar side chains was characterised by a low activation energy of 11 kJ mol(-1), while longer relaxation times varied from 418 to 155 ms. In the range 140-190 degrees C, the release of the strongly bound water in keratin samples irradiated with doses of 0-50 kGy was evidenced by the high value of the activation energy of 84 kJ mol(-1) and shorter relaxation times varying from 43 to 3 ms. The value of the activation energy decreased to 55 kJ mol(-1) for keratin samples irradiated with 200 kGy as a result of degradation of the hydrogen bond between the water and polar groups of the main chain of the macromolecule. The results presented may be useful in bio-electrical impedance analysis, for physiological and clinical research. The method applied in vivo should permit detection of changes in the stratum corneum induced by water, ionising radiation, cosmetics and diseases such as fibromyalagia or diabetic foot ulcers.