ESR studies on free radicals in γ-irradiated silk fibroin

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  • γ線照射絹に生成するラジカル
  • γ‐線照射絹に生成するラジカル
  • ガンマ セン ショウシャ キヌ ニ セイセイスル ラジカル

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ESR spectrum of free radicals in fibroin γ-irradiated was observed to be a broad singlet at -195°C. Its intensity decreased with increasing temperature until the spectrum completely disappeared at -40°C. The decay of singlet spectum was ascribed to conversion from cation radicals to glycyl radicals by hydrogen adstraction from Cα positon. ESR spectrum observed at room temperature was a quartet and its couplig constant was in a good agreement with that of the free radicals in γ-irradiated poly (gly-L-ala). It is found that the radicals in silk consist of the overlaps of glycyl and alanyl radicals formed by hydrogen abstraction from Cα position. The difference in spectra for the γ-irradiated silk depependent on fiber axis in the magnetic field seemed to be related to the contribution of the anisotropy coupling constants of α-proton and the free radicals generated in the highly ordered and oriented regions to the silk fiber. When the ESR spectra of the glycyl radicals were added to that of alanyl radicals according to the propotion of their amino acid composition in silk fibroin, the constructed spectra were similar to the spectra of γ-irradiataed silk fibroin. From these fact, it is concluded that the free radicals in silk were produced at random by γ-irradiation.

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