Cu2+ probe of metal-ion binding sites in melanin using electron paramagnetic resonance spectroscopy: I. Synthetic melanins

doi:10.1016/0003-9861(80)90430-0

Archives of Biochemistry and Biophysics

Volume 202, Issue 1, June 1980, Pages 289-303

https://doi.org/10.1016/0003-9861(80)90430-0 Get rights and content

Abstract

The isotope ⁶³Cu²⁺ has been used to probe the metal-ion binding sites of synthetic (autoxidized) catechol and 3,4-dihydroxyphenylalanine melanins using electron paramagnetic resonance spectroscopy. Samples were in aqueous media over a wide range of pH values. Assignments of the structures of the melanin-copper complexes are based in part on model studies of the complexes formed with melanin precursors, catechol and 3,4-dihydroxyphenylalanine, and with phenanthroline. Nearly all complexes involve just one or two ligands from melanin. In catechol melanin below pH 5.0, complexes with carboxyl groups are formed; above 6.0, Cu²⁺ forms complexes with phenolic hydroxyl groups. These same complexes were found in 3,4-dihydroxyphenylalanine melanin and binding of Cu²⁺ at amino acid type sites also was detected. After partial reduction of copper ions bound to 3,4-dihydroxyphenylalanine melanin, a weak signal of copper with four melanin ligands (oxygen and nitrogen in various combinations) was observed.

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Citation Excerpt :
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^☆: This work was supported by National Science Foundation Grant PCM 76-14831 and by National Institutes of Health Grant 5P41 RR01008.

²: Present address: Institute of Molecular Biology, Department of Biophysics, Jagellonian University, Grodzka 53, 31-001 Krakow, Poland.

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Cu2+ probe of metal-ion binding sites in melanin using electron paramagnetic resonance spectroscopy: I. Synthetic melanins☆

Abstract

Exp. Eye Res

Biophys. J

Inorg. Chim. Acta

J. Inorg. Nucl. Chem

Arch. Biochem. Biophys

Tetrahedron

Inorg. Chem. Acta

Coord. Chem. Rev

Arch. Biochem. Biophys

Melanins

J. Amer. Chem. Soc

Science

Cu²⁺ probe of metal-ion binding sites in melanin using electron paramagnetic resonance spectroscopy: I. Synthetic melanins☆