melanin

Melanin is a name for the aromatic biopolymer and organic semiconductor responsible for human eye and skin color. The same chemical is also found in the feathers of birds, the scales of fish, the fur of animals and the chitin of insects. Melanin has been found intact in fossils. Microorganisms also contain melanin.Melanin is in the ink of cephalopods. Sepia is the Greek word for the black matter emitted by sepia officinalis, the common cuttlefish. Melanin extracted from that ink is currently worth over $350 a gram more than gold.There are three melanins. Pheomelanin is red and yellow. Eumelanin is brown and black. In plants allomelanin is also brown and black. Though some refer to a "neuromelanin," it is actually eumelanin which performs a neurological function.Melanogenesis, the name for the chemical metabolism that gives rise to melanin, is not a single universal process. Pheomelanin and eumelanin follow a similar pathway until the L-dopaquinone phase of their formation. At that stage adding L-cysteine will produce pheomelanin; the absence of L-cysteine results in eumelanin.Skin cancer rates and deaths from melanoma are highest in people with the least amount of skin melanin. The opposite is true for people with the highest amount of skin melanin.Like all polyacetylenes, melanin has high electrical conductivity. Melanin was first proven to be a semiconductor in 1973 when, by Dr. John Mcginness and Dr. Peter Proctor to manufacture a melanin bi-stable switch.