AbstractWool fibers and cloth damaged by mechanical action such as abrading and grinding show strong EPR signals. Silk fibers after grinding also show strong EPR signals. Both wool and silk ground in a dry nitrogen atmosphere exhibit a doublet spectrum attributed to a ·CH radical on the polypeptide chain. In wool, a complex curve centered atg= 2.025 is observed. It is attributed to a CH2S· radical resulting from the rupture of the disulfide bond in the cystine residue. These radicals are stable for many months in a nitrogen atmosphere or vacuum. In dry oxygen the spectrum of the ·CH radical is transformed within a few hours from a double into a single, narrow curve, whereas the spectrum characteristic of the cystine radical disappers more slowly. In the presence of water vapor both radical species are rapidly destroyed and their spectra disappear. The mechanisms for the production of free radicals by mechanical action are believed to be direct chain rupture or localized pyrolysis, coupled with migration to specific radical traps in the pro
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