Scientists have used an unnatural amino acid and a catalytic copper complex to create a new, artificial enzyme. For this study, they added a copper complex to a protein that had no enzymatic properties and inserted an unnatural amino acid into the protein. The structure of the LmrR protein (green), with the two added catalytic groups binding to their substrates. In 2018, they created a non-enzymatic protein, the bacterial transcription factor LmrR, which could form non-biological hydrazone structures after the insertion of the unnatural amino acid p aminophenylalanine. This was the first enzyme created using an unnatural amino acid as a catalytic group.