Azides of amino acids can be labeled with terminal Alkyne or strained Alkyne (e.g. DBCO)-tagged reporter molecules via a Cu(I)-catalyzed Alkyne-Azide (CUAAC) or Cu(I)-free strain-promoted Alkyne-Azide Click Chemistry (SPAAC) reaction, respectively.
A number of cell-permeable Click-functionalized amino acids are randomly incorporated instead of methionine during translation and are therefore suitable for residue selective protein synthesis monitoring.