Degree of polymerization of 5, 6‐dihydroxyindole‐derived eumelanin from chemical degradation study. (12th May 2014)

• Record Type: Journal Article
• Authors: Okuda, Hidekazu; Yoshino, Kyoji; Wakamatsu, Kazumasa; Ito, Shosuke; Sota, Takayuki
• Is Part Of: Pigment cell & melanoma research. Volume 27:Number 4(2014:Jul.)
• Page Start: 664
• Page End: 667
• Publication Date: 2014-05-12
• Subjects: Melanoma -- Periodicals; Chromatophores -- Periodicals; Animal pigments -- Periodicals; 616.99477
• DOI: 10.1111/pcmr.12254
• Languages: English
• ISSNs: 1755-1471

Abstract

<abstract abstract-type="main" id="pcmr12254-abs-0001"> <title>Summary</title> <p>Eumelanin is a brown‐black pigment comprising 5, 6‐dihydroxyindole (DHI) and its 2‐carboxy derivative (DHICA), but the detailed structure of eumelanin is unclear. Chemical degradation is a powerful tool for analyzing melanin. H₂O₂ oxidation degradation of eumelanin affords pyrrole‐2, 3, 5‐tricarboxylic acid (PTCA) and pyrrole‐2, 3‐dicarboxylic acid (PDCA). The ratio of PDCA to PTCA provides information about the eumelanin structure. In this article, we propose simple equations on the basis of previous experimental results on dimer yields for evaluating the yields of PTCA and PDCA from any DHI oligomers. Assuming the chemical disorder model of DHI‐melanin, we solve an equation where a theoretical expression for the ratio of PDCA to PTCA is set to the corresponding experimental value to obtain a plausible Poisson distribution of DHI oligomers. The results demonstrate that the main contributors to DHI‐melanin are tetramers and pentamers as shown by the mass spectrometry.</p> </abstract>