![]() ![]() The major interactions with Fe(III) in solution are at acidic pH values: 2+ and 2+, and at neutral and alkaline pH values: and 3−, evaluated by electronic structure calculations. The sample shows the absence of sulfur-containing groups, and the infrared spectrum shows characteristic νO–H, νC–H, νC=C, νC=O, and νC–O stretches, which are confirmed by electronic structure calculations. In this study, eumelanin was extracted and purified from dark hair using a modified Prota method and characterized by elemental analysis. Melanin in the skin and in dark hair, known as eumelanin, has three main groups that serve as donors: carboxylic acid, catechol, and quinone-imine. Starting from a survey of biological roles and functions, the present review aims at providing an interdisciplinary perspective of melanin pigments and related pathway with a view to showing how it is possible to translate current knowledge about physical and chemical properties and control mechanisms into new bioinspired solutions for biomedical, dermocosmetic, and technological applications.Įumelanin is an oligomeric pigment that has a high affinity for metal ions, which induces the formation of reactive oxygen species, causing melanoma cell apoptosis due to the acceleration of intracellular or extracellular oxidative stress. A closer intersectoral interaction between research centers is essential to raise the interests and increase the awareness of the biomedical, biomaterials science and hi-tech sectors of the manifold opportunities offered by pigment cells and related metabolic pathways. Despite considerable advances, applied research on melanins and melanogenesis is still far from being mature. ![]() The burst of polydopamine-based multifunctional coatings in materials science is just one example, and the list may be expanded to include melanin thin films for organic electronics and bioelectronics, drug delivery systems, functional nanoparticles and biointerfaces, sunscreens, environmental remediation devices. Overall, these results provide, for the first time, unambiguous evidence for marked structural differences of mammalian eumelanins which may be directly related to the diversity of the sites of biosynthesis and storage, as well as to functional role of these pigments.ĭuring the past decade, melanins and melanogenesis have attracted growing interest for a broad range of biomedical and technological applications. Iris melanin proved able to promote the Fenton oxidation of deoxyribose while hair melanin was ineffective. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of the final pigment provided evidence for homologous series of DHICA oligomers, while chemical analysis allowed an estimate of 2:1 DHICA/DHI-derived units in the polymer, with a substantial proportion of intact o-diphenolic functions. ![]() For comparison, a different eumelanin isolated from black bovine irides by a similar enzymatic procedure was analyzed. ![]() HPLC analysis of pyrrole acids resulting from alkaline H2O2 degradation, carboxyl content determination, and ferricyanide titration showed that the isolated pigment is made up of 5,6-dihydroxyindole (DHI)- and 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-derived units at a 6:1 ratio, exhibiting a significant degree of oxidative degradation. Sequential digestion with protease, proteinase K and papaine in the presence of dithiothreitol afforded a pigment with a 6% w/w protein content. A new enzymatic procedure was developed for isolation of eumelanin from black human hair which might provide a substantially intact pigment for structural characterization. ![]()
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