Photo-oxidation of proteinaceous fibres correlates directly to lowered appearance retention and performance, with particular commercial significance for wool and human hair. We here outline the first detailed proteomic evaluation of differential photo-oxidation occurring in the cuticle and cortex of wool fibres. After exposure of whole wool to UVB irradiation, physical disruption techniques designed to minimise further oxidative modification were utilised to prepare enriched cuticle and cortex fractions. This was followed by comprehensive redox proteomic analyses of photo-oxidation via the location within the fibre components of modifications to aromatic residues. An oxidative classification system was developed and applied to provide further insight into differential photo-oxidation. These results were compared with coloration changes observed within the cuticular and cortical components of the fibre. In this study, although the cuticle was observed to have a higher level of baseline oxidation, the cortex exhibited significantly higher levels of photo-oxidation under UVB irradiation. These proteomic results were supported by the observation of significantly higher photoyellowing within the cortex than within the cuticle. It has been assumed that fibre photo-oxidation was predominantly confined to the wool cuticle, and that changes within the cuticle had the greatest effect on appearance retention. These results provide new insight into the contribution of the cortex to photo-induced discoloration of proteinaceous animal fibres.
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