All proteins produced by living cells are made from the 20 amino acids that are programmed by the genetic code.

The MIT team came up with a way to assemble proteins from amino acids not used in nature, including many that are mirror images of natural amino acids.

"There is no other technological platform that can be used to create these xenoproteins because people haven't worked through the ability to use completely nonnatural sets of amino acids throughout the entire shape of the molecule," says Brad Pentelute, an MIT associate professor of chemistry and the senior author of the paper, which appears in the Proceedings of the National Academy of Sciences the week of May 21.

Zachary Gates, an MIT postdoc, is the lead author of the paper.

Timothy Jamison, head of MIT's Department of Chemistry, and members of his lab also contributed to the paper.

Pentelute and Jamison launched this project four years ago, working with the Defense Advanced Research Projects Agency (DARPA), which asked them to come up with a way to create molecules that mimic naturally occurring proteins but are made from nonnatural amino acids.

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