The photolytic production of chromophores and fluorescence in wool keratin

Abstract

The differential reflectance and three‐dimensional fluorescence spectra of wet and dry wool following UVB irradiation at 303 nm in the presence and absence of oxygen were measured. Fluorescence originating from tryptophan residues was reduced under all irradiation conditions and a nonfluorescent chromophore with a maximum at 320 nm was produced. These findings suggest that neither singlet oxygen nor triplet states are involved in the formation of the chromophore. Following irradiation of wool at 303 nm in the absence of oxygen, fluorescence with an excitation maximum between 360 and 380 nm and an emission maximum at 440 nm appeared. Fluorescence with an excitation maximum between 410 and 420 nm and an emission maximum at 470 nm from a different species was produced by photolysis in the presence of oxygen. The presence of water accelerates the formation of the latter fluorophore and this observation suggests that singlet oxygen is not involved in its formation.