Structural and functional studies of Sepia and human melanins

Initial investigations were focused on defining a source of human melanin that is of sufficient quantity and quality to facilitate structural and functional studies of the pigment. By carrying out a detailed investigation of human hair eumelanin, we find that enzymatic extraction techniques yield a melanin that is biologically relevant and is used in the following studies. Using this well-defined human melanin and the accepted animal model melanin from Sepia officinalis, a new technique was developed to chemically label and solubilize these melanins. Covalent modification is an attractive route to access the structure of these pigments since the reactivity of the label allows rationalization of starting material structure.; A commonly mentioned property of melanin is the ability to bind a diversity of metal cations. As this is believed to be of biological importance, a detailed investigation of the capacity and strength of the interaction was warranted. A method was developed to remove the metal cations present in Sepia melanin and replace them with increasing amounts of a metal of interest. Competitive experiments suggest that Fe3+ occupies a different binding site than Ca2+ and Mg2+ ions, which can displace each other. The interaction of Ca2+ with melanin was investigated further due to the importance of that ion's level in controlling keratinocyte fate and the implication that melanin participates in Ca2+ regulation.