In vitro genetic code reprogramming and expansion to study protein function and discover macrocyclic peptide ligands.

The ability to introduce non-canonical amino acids into peptides and proteins is facilitated by working within in vitro translation systems. Non-canonical amino acids can be introduced into these systems using sense codon reprogramming, stop codon suppression, and by breaking codon degeneracy. Here, we review how these techniques have been used to create proteins with novel properties and how they facilitate sophisticated studies of protein function.