Send to

Choose Destination
See comment in PubMed Commons below
J Biol Chem. 1990 Jul 25;265(21):12410-6.

Bleaching of melanin pigments. Role of copper ions and hydrogen peroxide in autooxidation and photooxidation of synthetic dopa-melanin.

Author information

  • 1Biophysics Section, Medical College of Wisconsin, Milwaukee 53226.


Bleaching of eumelanin has been studied in model systems consisting of synthetic dopa-melanin and various concentrations of hydrogen peroxide, molecular oxygen, and copper(II) ions at neutral and alkaline pH. The data show that at neutral pH, in the dark, metal-ion-free melanin is very resistant to oxidation by hydrogen peroxide. However, the rate of bleaching of melanin, induced by H2O2 is significantly accelerated by illumination from UVA-visible light. Bound-to-melanin copper(II) also accelerates the bleaching of melanin with the efficiency dependent on concentration of H2O2 and oxygen. It suggests possible involvement of melanin-copper complexes in Fenton-like processes. The formation of hydroxyl radicals during melanin bleaching has been concluded on the basis of the electrochemical detection of hydroxylation products of salicylate used as OH scavenger. Redox conversion of bound-to-melanin copper ions was monitored by EPR spectroscopy and direct measurement of melanin-Cu(II) complexes. It has been shown that melanin-copper(I) complexes were readily oxidized by either oxygen or hydrogen peroxide. The data indicate that bleaching of melanin is a complex process with two distinct stages, reversible oxidation of the hydroquinone moieties of melanin followed by irreversible reactions of the monomers that lead to degradation of the melanin polymer.

[PubMed - indexed for MEDLINE]
Free full text
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire
    Loading ...
    Support Center