Abstract
Electron spin resonance (ESR) spectra were determined for three preparations of amylose irradiated at a dose rate of 10/sup 5/ r/hr with Co/sup 60/ gamma rays to total doses of 1.8 x 10/sup 7/ r a t room temperature in vacuo. The starting materials were amylose with a helical structure, deuterated amylose, and heated amylose (lacking a helical structure). The concentration of the free radicals produced by irradiation was determined by comparison of the ESR spectra with that of a known quantity of alpha , alpha -diphenylpicrylhydrazine. The ESR tracings changed their shape and height during the storage of the specimens at room temperature after irradiation. These results indicated that gamma -irradiated amylose having the helical structure contains two or more kinds of free radicals having different lives at room temperature. Different spectra were obtained for deuterated amylose. If the spectra reflect only related R-O radicals, no significant difference would be expected between deuterated amylose and amylose having the helical structure. Therefore, the principal difference between these spectra would be based on the altered interaction between an unpaired electron of the alpha -carbon atom and hydrogen or deuterium of hydroxyl groups. X-ray-diffraction patterns showed that the crystalline helical structure ofmore » the amylose was damaged by the heat treatment during deuteration. These results suggest that the crystalline helical structure of amylose acts as a radical trap. Previous ESR studies on uvirradiated amylose in the presence of H/ sub 2/O/sub 2/ at --195 deg C showed a spectra consisting of a triple-line which disappeared immediately when the samples were brought to -130 deg C. An identical spectrum was obtained in the case of deuterated amylose, indicating that different species of free radicals were formed between gamma - and uv-irradiated amyloses.« less
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