The effect of copper on eumelanin photophysics and morphology

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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.
Original languageEnglish
Title of host publicationImaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues XI
EditorsDaniel L. Farkas, Dan V Nicolau, Robert C Leif
Place of PublicationSan Francisco, California
Number of pages6
Publication statusPublished - 2013

Publication series

NameProgress in biomedical optics and imaging


  • thioflavin T
  • aggregation
  • fluorescence
  • L-DOPA
  • copper ions
  • 4-dihydroxy-L-phenylalanine

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