COMPARATIVE MOSSBAUER AND INFRARED-ANALYSIS OF IRON-CONTAINING MELANINS

A Moessbauer study was carried out on some types of melanin. 57Fe3+ was bound to melanin from sepia ink and to that obtained by autooxidation of L-dopa and dopamine. Moessbauer spectra, performed in parallel with IR measurements, indicated that paracrystalline subunits are present, showing a superparamagnetic behavior. The preferential binding sites for Fe are different in melanins having L-dopa as precursor from those obtained starting from dopamine. In particular, the linkage to carboxylic groups is predominant in the former, and linkage to phenolic, aminic and/or indolic groups can be observed in the latter. The results also confirm the close similarity between natural sepia melanin and that obtained from an L-dopa precursor.