Probing the building blocks of eumelanins using scanning electron microscopy

Scanning electron microscopy (SEM) is used to examine the structure of natu ral and synthetic melanins. Eumelanin from Sepia officinalis and synthetic eumelanin are found to be structurally dissimilar. The natural sample has a significant structural order with subunits that have a lateral dimension o f similar to 15 nm. The synthetic samples, on the other hand, appear to be amorphous solids. These results lend support for the existence of fundament al structural units proposed from the analyses of wide-angle X-ray diffract ion measurements and previous mass-spectrometry results. These findings als o provide insight into the disparate photophysical behavior of Sepia and sy nthetic eumelanin.