Figure 3: Basic monomeric units and oligomeric structure of melanin.

Monomeric units of melanin; (a) 5,6-dihydroxyindole (DHI) and (b) 5,6-dihydroxyindole-2-carboxylic acid (DHICA) (modified from ref. 33). (c) Proposed oligomeric structure model of melanin (modified from ref. 36).