The same radical, g=2.0046, was detected in UV-irradiated natural fibers, spider's strings or silk, origining in their peptide structures. Their fibers structure are respectively diffrent, but they seem to have the same structure damaged by UV-irradiation.
In the case of UV-irradlated silk, radicals produced in raw silk were very strong, but deduced by alkaline treatment with 0.01 mol/l NaOH for 1 hr.. Othreside, radicals for silk strings were increased by alkaline treatment under the same condition. This fact seems to suggest an adequate alkaline treatment protects natural fibers as silk against UV-irradiation.