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Synthetic melanin is a model for soluble natural eumelanin in UVA-photosensitised superoxide production

Paper ID Volume ID Publish Year Pages File Format Full-Text
30881 44511 2006 12 PDF Available
Title
Synthetic melanin is a model for soluble natural eumelanin in UVA-photosensitised superoxide production
Abstract

Studies to UV-irradiate natural eumelanins in vitro have used insoluble pigment obtained by acid hydrolysis, which lacks melanoprotein. Eumelanin synthesised in the presence of a protein is not insoluble, and the insoluble form of melanin from acid hydrolysis may not have the same physicochemical properties as the natural pigment synthesised in vivo in the melanosome. Here we investigated radical production by three natural eumelanins exposed to solar levels of UVA; sepia melanin from Sepia officinalis, and eumelanins isolated from Oriental human and domestic cat hair. UVA irradiation of sepia melanin in solution at pH 4.5 in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) gave hydroperoxyl and hydroxyl radical-adducts, maximal at 0.6–2.5 mg/ml melanin concentrations. Hydroperoxyl radical production was relatively low in acetate buffer, but detected in aqueous suspensions of sepia melanin. Hair eumelanins were photoreactive with hydroperoxyl radical-adduct production at low concentrations (0.1–0.4 mg/ml melanin). Synthetic pigment after synthesis undergoes photo-oxidation (producing superoxide) at low concentrations (⩽0.3 mg/ml) and its oxidation increases the photoreactivity at higher melanin concentrations. These findings may be physiologically relevant to the properties and function of eumelanin in vivo when it is at low concentration (found in a small proportion of Caucasian melanocytes), and suggest that synthetic melanin has the potential for the basis of a model for natural eumelanin.

Keywords
Electron spin resonance spectroscopy; Free radicals; Eumelanin; Spin trapping; Melanocyte; Photoprotection; UV radiation
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Synthetic melanin is a model for soluble natural eumelanin in UVA-photosensitised superoxide production
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 82, Issue 3, 1 March 2006, Pages 224–235
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us