Pigments supernatants

A melanin-like pigment (far left) can assume a range of colours depending on the specific amino acid added to it. Credit: Ayala Lampel

Chemistry

Chemists’ riff on melanin makes a rainbow

An adaptation to the body’s pigment formula produces particles that outshine melanin.

A laboratory method that mimics how melanin is made in the skin yields pigments in a wide range of brilliant colours.

Just one pigment — melanin — serves as the basis for the diversity of hair, skin and eye colour in humans. The most abundant form of melanin is black or brown and is made from a single chemical building block, the amino acid tyrosine.

To synthesize similar pigments that outperform melanin, Ayala Lampel at Tel Aviv University in Israel, Rein Ulijn at City University of New York and their colleagues started with a peptide — a short string of amino acids — containing tyrosine, lysine and phenylalanine. The researchers adjusted the peptide’s pH to induce its organization into tiny fibres. Then, the researchers added an enzyme to facilitate the same key chemical reaction that triggers melanin formation in the body. As a result, the fibres slowly reconfigured into melanin-like particles.

As the particles grew, they took on a colour when the authors added another amino acid: yellow with cysteine, deep red with phenylalanine and greenish brown with isoleucine.

The researchers hope that these melanin-inspired pigments could one day colour paints and cosmetics.