Spectroscopic and dynamic studies of the epidermal chromophores trans-urocanic acid and eumelanin

Photoaging and skin cancer can result from the exposure of skin to ultravio let A (UV-A, 320-400 nm) radiation. The detailed chemical mechanisms by whi ch these processes occur are not known, but they must begin with the absorp tion of a UV-A photon by one or more photoreceptor(s) within the skin. The situation is complicated by the lack of understanding of the photoreactions of many of the UV-A-absorbing molecules in skin. In this Account, we descr ibe recent research efforts directed at elucidating the UVA-induced photore activity of two light-absorbing epidermal photoreceptors: trans-urocanic ac id and eumelanin.