Selenium helps synthetic melanin prevent radiation damage

Melanin biopolymers bring color to the natural world, from the brilliance of bird feathers to the hues of our own skin. These molecules also protect organisms from harmful radiation. A team of researchers led by Nathan Gianneschi, a chemist at Northwestern University, were inspired to upgrade melanin and help it do this job even better, potentially allowing chemists to formulate shielding materials that could protect people from the harsher radiation in outer space. Their new synthetic analogue, called selenomelanin, can be made by genetically engineered microbes or by synthetic chemistry, and outperforms its naturally occurring family members (J. Am. Chem. Soc. 2020, DOI: 10.1021/jacs.0c05573). The lowest dose of radiation tested—the equivalent of a cancer radiotherapy treatment—caused DNA damage in human epithelial cells treated with other melanin analogues. But selenomelanin-treated cells remained viable even after exposure to radiation at levels that would kill an adult. Gianneschi wonders if a biotic form of selenomelanin remains to be discovered. “Maybe we can go into nature and find it,” he says. His team is now collaborating with biologists to search for evidence of naturally occurring selenomelanin in the Salton Sea—a selenium-contaminated lake in Southern California.