Oral communication, GL3

Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011

Photochemistry and excited state dynamics of eumelanin building blocks

During the last decade significant work has been devoted to the nature of UV-induced processes in eumelanin. All this work has been carried out on the whole pigment-complex. Assigning the observed phenomena to specific UV-induced processes is however complicated because of the large variety of oligomers present in the in-vivo pigment complex. The complexity of such analysis has motivated us to initiate a systematic study of smaller building blocks with a well-defined structure. Using time resolved spectroscopy we have succeeded in identifying several of the excited state processes of DHICA, DHI as well as of oligomers and polymers of these units. Thus, we have found that excited state Intramolecular Proton Transfer is the mechanism of excited state energy dissipation in DHICA monomers. Oligomers of DHICA have extremely efficient excited state dissipation, reminiscent of full melanin pigment. The mechanism of this very efficient energy dissipation is probably excited state inter-unit proton transfer within an oligomer. The two building blocks of melanin DHICA and DHI have very different photochemistry, which may be related to their suggested photoprotective and phototoxic properties, respectively.

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