For the first time, researchers have incorporated unnatural amino acids into an animal, the nematode worm Caenorhabditis elegans (J. Am. Chem. Soc., DOI: 10.1021/ja2054034). The results could lead to new tools for dissecting the biochemistry of living things. Unnatural amino acids have been placed in bacteria and mammalian cells in several ways. To put the extra amino acids tert-butoxycarbonyl lysine or alkyne-functionalized lysine into worms, postdoc Sebastian Greiss and Jason W. Chin of the Medical Research Council Laboratory of Molecular Biology, in England, turned to established technology—specially designed protein translation machinery from a microbe. They also used mutant worms lacking part of a biochemical surveillance mechanism that would normally destroy unnatural-amino-acid-encoding RNA. The duo confirmed the presence of alkynyl lysine in the worm by selective labeling with biotin azide. They also used a fluorescent reporter that glows red only after successful incorporation. Greiss and Chin say they cannot yet rule out that the worm removes the tert-butoxycarbonyl group from lysine after incorporation. They are producing more protein with the unnatural amino acid so they can determine whether it stays intact.