The effect of copper on eumelanin photophysics and morphology

Birch, David J S and Sutter, Jens; Farkas, Daniel L. and Nicolau, Dan V and Leif, Robert C, eds. (2013) The effect of copper on eumelanin photophysics and morphology. In: Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues XI. Progress in biomedical optics and imaging, 8587 . SPIE, San Francisco, California. ISBN 9780819493569

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Despite being an important pigment in skin, hair, the eye and the brain, melanin remains one of the most enigmatic of pigments. Although the main constituents of melanin are known to be dihydroxyindoles, its photophysics is complex and its detailed structure remains unknown. In this work we have arrested prior to completion the usual synthesis of eumelanin formed via auto-oxidation of 3, 4-dihydroxy-L-phenylalanine (L-DOPA), by the addition of copper ions. Using fluorescence techniques we report how copper modifies the self assembly of eumelanin by reducing the time to the onset of aggregation at pH 10 and yet produces simplified photophysics in terms of a clearly-defined fluorescence spectrum and a fluorescence decay that is described well by a dominant single lifetime of ~ 6ns. This behavior isconsistent with copper inducing an enhanced abundance of 5,5-dihydroxyindole-2-carboxylic acid (DHICA). Metal ion binding to melanin is of particular importance to neurology and has potential applications in optoelectronics.


Birch, David J S ORCID logoORCID: and Sutter, Jens ORCID logoORCID:; Farkas, Daniel L., Nicolau, Dan V and Leif, Robert C