The structure of neuromelanin and its iron binding site studied by infrared spectroscopy

The binding of neuromelanin (NM) to iron is of interest due to its role in brain aging and Parkinson's disease. In the present work, infrared spectra of both NM isolated from huma brain and of synthetic NM analogues are reported with the aim of identifying the main functional groups and their chelating ability for iron. It is observed that a peptide and an aliphatic chain are present in the NM structure. The coordination of iron in NM occurs through -OH phenolic units. In synthetic melanin samples, the preferred sites for iron binding are -OH phenolic and [symbol: see text]NH indolic groups. Amino acid analysis confirmed the presence of a peptide component in NM and synthetic melanin incubated in putamen homogenate. In addition, the elemental analysis demonstrated the presence of an aliphatic component specific of NM.