Electron spin resonance study of gamma-irradiated hair and nails

In this work, the properties of radicals produced in human hair and fingernail by irradiation and mechanical degradation have been investigated by using Electron Spin Resonance (ESR) technique. Different hair and nail samples were irradiated by using UV and Y-sources (Co) and the time dependence of decaying of the radicals produced by irradiation have been investigated. The effect of the sun was also examined for hair samples. From the recorded ESR spectra of hair samples collected from a large number of volunteers, it was shown that the signal intensities and the spectroscopic splitting factors g determined from recorded spectra were color dependent. The line width for hair samples are found to be nHPP 4.7 G and the g-factors for different colors of hair vary for fair hair in the range of 2.0037-2.0041, for dark hair 2.0040-2.0043 and for red hair 2.0050-2.0052. Also, dark hairs show greater signal intensity than fair hairs. Nail samples were observed to have spectroscopic splitting factor g=2.0040 and line width u1HPP=4.5 G. By cutting the hair and the nail samples, the effect ot mechanical degradation due to cutting on properties and time variation of the radicals were examined. The decay constants for the 3 lines observed in the nail sample spectra after mechanical degradation were determined to be 6x10-5 s, 1.4x10s-1 and 12x10a s-1 respectively, for low, central and high fields. Spectra of samples were also recorded at liquid nitrogen (77 K) and in the high temperatures 300-470 K. In 300 - 470 K temperature range, the signal intensities for hair samples were found to increase. When the temperature was decreased from 470 K back to 300 K, signal intensity of the hair sample remained constant. By also using the data recorded from DSC technique, it was decided that the variation in the line intensities of the samples were related to the water content found in the structure. Activation energy for nail samples were determined to be 15.4 kcal/mol by using variable temperature data for nail samples. The simulation procedure was carried out at room and liquid nitrogen temperature for nail samples. Upon irradiation of the samples in 15-40 Gy dose ranges, hair samples show a lineer dose-response curve. As for fingernail samples, due to the fact that they show a broad, non-resolved ESR spectra, it was not possible to get an appropriate dose-response curve for these samples. Upon these results, a discussion was made whether or not nail and hair samples could be use as dosimetric material