Characterization of the Fe(III)-binding site in Sepia eumelanin by resonance Raman confocal microspectroscopy.
The resonance Raman spectrum of Sepia eumelanin is discussed by analogy to model compounds containing catechol (CAT)-like structural units. These data are then compared with the analogous data on Fe(III)-enriched Sepia eumelanin. In contrast to the natural eumelanin, the Fe(III)-enriched samples exhibit absorption features in the visible and near-IR spectral regions, which are attributed to ligand-to-metal charge-transfer (LMCT) bands. Resonance Raman spectra collected by exciting these LMCT bands reveal bands at 580 and 1470 cm(-1); the intensity of these features increases with increasing Fe(III) content. The 580 and 1470 cm(-1) bands are assigned to Fe-OR stretching and ring deformation modes, respectively. These data further substantiate that the Fe(III)-melanin-binding site in melanin is composed of CAT-like structural units.
Samokhvalov
Alexander
A
Department of Chemistry, Duke University, Durham, NC 27708-0346, USA.
Liu
Yan
Y
Simon
John D
JD
D000818:Animals; D001665:Binding Sites; D007501:Iron / Q000378:metabolism*; D008543:Melanins / Q000737:chemistry / Q000378:metabolism*; D018613:Microscopy, Confocal; D008974:Mollusca; D013059:Spectrum Analysis, Raman
D008543:Melanins; C041877:eumelanin; D007501:Iron