On the structure of human hair melanins from an infrared spectroscopy analysis of their interactions with Cu2+ ions

Melanins were isolated from dark and red human hair and complexed with copp er ions at various pH values in a complexing medium. IR spectra of melanins and their Cu2+ -complexes for pellets with KBr were obtained. The IR spect ra indicate that Cu2+ ions bound to melanins are fixed by different carboxy l and hydroxyl (phenolic and/or alcoholic) groups in the macromolecule. Fro m these results it is concluded that, generally, melanin carboxyl groups ar e responsible for interactions of metal ions with the melanin molecule. Com plexes of melanins isolated from dark and red human hair show structural di fferences when analysed by IR spectroscopy. Conclusions from these investig ations assist in the differentiation of structures of analysed hair melanin s. IR spectral analysis of melanin samples and their complexes suggest that melanin samples obtained from red hair may contain eumelanin. (C) 2001 Els evier Science B.V. All rights reserved.