May 2005
Volume 46, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2005
Comparison of the Structural Patterns Between Different Kinds of Melanin by MALDI–TOF Mass Spectrometry
Author Affiliations & Notes
  • A. Szczurowski
    Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL
  • J. Dillon
    Department of Ophthalmology, Columbia University, College of Physicians and Surgeons, New York, NY
  • E.R. Gaillard
    Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL
  • Footnotes
    Commercial Relationships  A. Szczurowski, None; J. Dillon, None; E.R. Gaillard, None.
  • Footnotes
    Support  NIH Grant EY12344
Investigative Ophthalmology & Visual Science May 2005, Vol.46, 1612. doi:
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      A. Szczurowski, J. Dillon, E.R. Gaillard; Comparison of the Structural Patterns Between Different Kinds of Melanin by MALDI–TOF Mass Spectrometry . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1612.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: The purpose of the study is to determine if the fragmentation pattern of different kinds of melanin obtained via MALDI–TOF–MS can be used to distinguish them structurally. Methods: Four samples of melanins were analyzed: synthetic melanin (soluble and insoluble fractions) from polymerized L–DOPA, sepiamelanin that was purchased from Sigma–Aldrich and ocular melanins, which were isolated from calf and human RPE. The optimal ionization conditions were established for each kind of melanin by varying the matrix (3–indoleacrylic acid [IAA], 1,8,9–anthracenetriol [Dithranol] or α–cyano–4–hydroxycinnamic acid [CHCA]), the solvents and solvent concentration (TFA, THF) and the laser power (from 60% to 80%). A series of analyses were carried out by MALDI–TOF–MS (Bruker Omniflex). Results: The spectra of the melanins exhibit regular peak distributions. Molecular weight differences between the peaks are very similar for each specific melanin but vary between different melanins. These data allow for monomer building block structures to be proposed for each type of melanin. The major proposed building blocks are dihydroxyindoleacetic acid (fragment m/z = 186, 191, 192) for synthetic melanin, pyrrhole tetracarboxylate (fragment m/z = 207, 208, 209, 210) for sepia melanin and sulfur containing quinoline analog (fragment m/z = 282) for mammalian ocular melanin. Conclusions: Different types of melanin can be distinguished based on their fragmentation pattern obtained via MALDI–TOF–MS thus providing a spectroscopic signature unique to the type of melanin.

Keywords: retinal pigment epithelium • oxidation/oxidative or free radical damage • radiation damage: light/UV 
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