Fig. 1: Transient spectral hole burning of DOPA melanin (eumelanin) and putative chromophore structures.
From: Probing the heterogeneous structure of eumelanin using ultrafast vibrational fingerprinting
a Absorption spectrum (black curve) of an aqueous solution of DOPA melanin. Profiles of excitation laser pulses (colored curves) used in femtosecond transient absorption measurements showing their spectral width (arbitrary vertical scaling). b Transient spectral holes extracted from transient absorption spectra measured 500 fs after excitation at 400, 500, or 600 nm. c Chemical structures of eumelanin building blocks. d Dimers of the building blocks, showing two major types of redox forms. e A few substructures proposed for DOPA melanin and other eumelanins. Labels indicate redox forms, which vary from least to most oxidized in the order hydroquinone<semiquinone<quinone imine/methide<quinone.
