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The surface oxidation potential of human neuromelanin reveals a spherical architecture with a pheomelanin core and a eumelanin surface.

Publication ,  Journal Article
Bush, WD; Garguilo, J; Zucca, FA; Albertini, A; Zecca, L; Edwards, GS; Nemanich, RJ; Simon, JD
Published in: Proceedings of the National Academy of Sciences of the United States of America
October 2006

Neuromelanin (NM) isolated from the substantia nigra region of the human brain was studied by scanning probe and photoelectron emission microscopies. Atomic force microscopy reveals that NM granules are comprised of spherical structures with a diameter of approximately 30 nm, similar to that observed for Sepia cuttlefish, bovine eye, and human eye and hair melanosomes. Photoelectron microscopy images were collected at specific wavelengths of UV light between 248 and 413 nm, using the spontaneous-emission output from the Duke OK-4 free electron laser. Analysis of the data establishes a threshold photoionization potential for NM of 4.5 +/- 0.2 eV, which corresponds to an oxidation potential of -0.1 +/- 0.2 V vs. the normal hydrogen electrode (NHE). The oxidation potential of NM is within experimental error of the oxidation potential measured for human eumelanosomes (-0.2 +/- 0.2 V vs. NHE), despite the presence of a significant fraction of the red pigment, pheomelanin, which is characterized by a higher oxidation potential (+0.5 +/- 0.2 V vs. NHE). Published kinetic studies on the early chemical steps of melanogenesis show that in the case of pigments containing a mixture of pheomelanin and eumelanin, of which NM is an example, pheomelanin formation occurs first with eumelanin formation predominantly occurring only after cysteine levels are depleted. Such a kinetic model would predict a structural motif with pheomelanin at the core and eumelanin at the surface, which is consistent with the measured surface oxidation potential of the approximately 30-nm constituents of NM granules.

Duke Scholars

Published In

Proceedings of the National Academy of Sciences of the United States of America

DOI

EISSN

1091-6490

ISSN

0027-8424

Publication Date

October 2006

Volume

103

Issue

40

Start / End Page

14785 / 14789

Related Subject Headings

  • Ultraviolet Rays
  • Surface Properties
  • Substantia Nigra
  • Sepia
  • Oxidation-Reduction
  • Microscopy, Electron, Scanning
  • Microscopy, Atomic Force
  • Melanins
  • Humans
  • Cattle
 

Citation

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Bush, W. D., Garguilo, J., Zucca, F. A., Albertini, A., Zecca, L., Edwards, G. S., … Simon, J. D. (2006). The surface oxidation potential of human neuromelanin reveals a spherical architecture with a pheomelanin core and a eumelanin surface. Proceedings of the National Academy of Sciences of the United States of America, 103(40), 14785–14789. https://doi.org/10.1073/pnas.0604010103
Bush, William D., Jacob Garguilo, Fabio A. Zucca, Alberto Albertini, Luigi Zecca, Glenn S. Edwards, Robert J. Nemanich, and John D. Simon. “The surface oxidation potential of human neuromelanin reveals a spherical architecture with a pheomelanin core and a eumelanin surface.Proceedings of the National Academy of Sciences of the United States of America 103, no. 40 (October 2006): 14785–89. https://doi.org/10.1073/pnas.0604010103.
Bush WD, Garguilo J, Zucca FA, Albertini A, Zecca L, Edwards GS, et al. The surface oxidation potential of human neuromelanin reveals a spherical architecture with a pheomelanin core and a eumelanin surface. Proceedings of the National Academy of Sciences of the United States of America. 2006 Oct;103(40):14785–9.
Bush, William D., et al. “The surface oxidation potential of human neuromelanin reveals a spherical architecture with a pheomelanin core and a eumelanin surface.Proceedings of the National Academy of Sciences of the United States of America, vol. 103, no. 40, Oct. 2006, pp. 14785–89. Epmc, doi:10.1073/pnas.0604010103.
Bush WD, Garguilo J, Zucca FA, Albertini A, Zecca L, Edwards GS, Nemanich RJ, Simon JD. The surface oxidation potential of human neuromelanin reveals a spherical architecture with a pheomelanin core and a eumelanin surface. Proceedings of the National Academy of Sciences of the United States of America. 2006 Oct;103(40):14785–14789.
Journal cover image

Published In

Proceedings of the National Academy of Sciences of the United States of America

DOI

EISSN

1091-6490

ISSN

0027-8424

Publication Date

October 2006

Volume

103

Issue

40

Start / End Page

14785 / 14789

Related Subject Headings

  • Ultraviolet Rays
  • Surface Properties
  • Substantia Nigra
  • Sepia
  • Oxidation-Reduction
  • Microscopy, Electron, Scanning
  • Microscopy, Atomic Force
  • Melanins
  • Humans
  • Cattle