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Support and challenges to the melanosomal casing model based on nanoscale distribution of metals within iris melanosomes detected by X ‐ray fluorescence analysis
Author(s) -
Gorniak Thomas,
Haraszti Tamás,
Suhonen Heikki,
Yang Yang,
HedbergBuenz Adam,
Koehn Demelza,
Heine Ruth,
Grunze Michael,
Rosenhahn Axel,
Anderson Michael G.
Publication year - 2014
Publication title -
pigment cell and melanoma research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.618
H-Index - 105
eISSN - 1755-148X
pISSN - 1755-1471
DOI - 10.1111/pcmr.12278
Subject(s) - melanosome , iris (biosensor) , fluorescence , nanoscopic scale , casing , nanotechnology , materials science , biophysics , chemistry , biology , physics , optics , computer science , artificial intelligence , biochemistry , melanin , geophysics , biometrics
Summary Melanin within melanosomes exists as eumelanin or pheomelanin. Distributions of these melanins have been studied extensively within tissues, but less often within individual melanosomes. Here, we apply X‐ray fluorescence analysis with synchrotron radiation to survey the nanoscale distribution of metals within purified melanosomes of mice. The study allows a discovery‐based characterization of melanosomal metals, and, because Cu is specifically associated with eumelanin, a hypothesis‐based test of the ‘casing model’ predicting that melanosomes contain a pheomelanin core surrounded by a eumelanin shell. Analysis of Cu, Ca, and Zn shows variable concentrations and distributions, with Ca/Zn highly correlated, and at least three discrete patterns for the distribution of Cu vs. Ca/Zn in different melanosomes – including one with a Cu‐rich shell surrounding a Ca/Zn‐rich core. Thus, the results support predictions of the casing model, but also suggest that in at least some tissues and genetic contexts, other arrangements of melanin may co‐exist.