Utilizing fluorescence, we generated excitation-emission matrices, which provided us with a map of fluorophores present in keratin tissues. Our findings suggest that all of the tested keratin substrates have features in common. We monitor the quantity of tryptophan as well as some of its metabolic and degradation products, the kynurenines. The peak due to kynurenine fluorescence is dominant and is a conglomerate of several molecular species including L-kynurenine, 3-hydroxykynurenine and N-formylkynurenine. The ratio of tryptophan to the kynurenines depends on the type of tissue and the amount of pigmentation present. The emission wavelength also greatly depends on these factors.
