Genetically encoding phenyl azide chemistry: new uses and ideas for classical biochemistry.

Introducing new physicochemical properties into proteins through genetically encoded Uaa (unnatural amino acid) incorporation can lead to the generation of proteins with novel properties not normally accessible with the 20 natural amino acids. Phenyl azide chemistry represents one such useful addition to the protein repertoire. Classically used in biochemistry as a non-specific photochemical protein cross-linker, genetically encoding phenyl azide chemistry at selected residues provides more powerful routes to post-translationally modify protein function in situ. The two main routes are modulation by light (optogenetics) and site-specific bio-orthogonal modification (bioconjugation) via Click chemistry. In the present article, we discuss both approaches and their influence on protein function.