Effect of Melanomal Proteins on Sepia Melanin Assembly

Melanins are phenol-based pigments with the potential for widespread applications, including bioelectronics and tissue engineering. The concentration-dependent structural transition of sepia melanin in water is analyzed. This biopolymer at high concentration gives the well-known nanospheres, whereas sample dilution gives unforeseen nanofibres exhibiting the structural features of mature amyloid fibrils. We propose a mechanism of pigment self-assembly dependent on the interaction of residual melanosomal protein(s) with eumelanin heteropolymer. Our results contribute to understanding the peculiar physicochemical properties of this ubiquitous pigment.