Metal-ion interactions and the structural organization of Sepia eumelanin

Yan Liu, John D. Simon

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

The structural organization of melanin granules isolated from ink sacs of Sepia officinalis was examined as a function of metal ion content by scanning electron microscopy and atomic force microscopy. Exposing Sepia melanin granules to ethelenediamine-tetraacetic acid (EDTA) solution or to metal salt solutions changed the metal content in the melanin, but did not alter granular morphology. Thus ionic forces between the organic components and metal ions in melanin are not required to sustain the natural morphology once the granule is assembled. However, when aqueous suspensions of Sepia melanin granules of varying metal content are ultra-sonicated, EDTA-washed and Fe-saturated melanin samples lose material to the solution more readily than the corresponding Ca(II) and Mg(II)-loaded samples. The solubilized components are found to be 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-rich constituents. Associated with different metal ions, Na(I), Ca(II) and Mg(II) or Fe(III), these DHICA-rich entities form distinct two-dimensional aggregation structures when dried on the flat surface of mica. The data suggest multiply-charged ions play an important role in assisting or templating the assembly of the metal-free organic components to form the three-dimensional substructure distributed along the protein scaffold within the granule.

Original languageEnglish
Pages (from-to)42-48
Number of pages7
JournalPigment Cell Research
Volume18
Issue number1
DOIs
Publication statusPublished - Feb 2005

Fingerprint

Sepia
eumelanin
Melanins
melanin
metal ions
Metal ions
Metals
granules
Ions
metals
carboxylic acids
scaffolding proteins
Sepia officinalis
mica
Acids
atomic force microscopy
acids
Ink
Carboxylic Acids
Atomic Force Microscopy

Keywords

  • Aggregation
  • Calcium
  • Chelation
  • Ethelenediaminetetraacetic acid
  • Iron
  • Magnesium
  • Sepia

ASJC Scopus subject areas

  • Cell Biology
  • Agronomy and Crop Science
  • Plant Science
  • Clinical Biochemistry
  • Developmental Biology

Cite this

Metal-ion interactions and the structural organization of Sepia eumelanin. / Liu, Yan; Simon, John D.

In: Pigment Cell Research, Vol. 18, No. 1, 02.2005, p. 42-48.

Research output: Contribution to journalArticle

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