Melanin from a physicochemical point of view

Melanin has an ambivalent nature; it can act as a protective or anti-protective agent, depending on its previous history. In this article we briefly review the current state of understanding of melanin structure and biosynthesis, its binding with drugs and metals, its adsorption and (photo)semiconductive properties, and its ability to couple redox reactions There is now a greater appreciation of the structural and spectroscopic differences between 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid melanins and a greater knowledge of the kinetics of eumelanin to pheomelanin and neuromelanin transformations and the molecular links among them. The scope of drug and metal binding to melanin has expanded. Recent work has shown that melanin can act as an electronic-ionic conductor. Melanin can couple redox reactions for biologically and commercially relevant solid and gaseous systems. (c) 2016 Society of Chemical Industry