Cyanobenzothiazole is a small molecule that can react very fast with 1,2-aminiothiol and also in a lesser extent with 1,2-diamine. Cyanobenzothiazole are not naturally present on biomolecules making it a good substrate for bioorthogonal reaction. On the other hand, 1,2-aminothiol is present in nature, being the motif of the rare aminoacid cysteine (Cys). It is noteworthy that endogenous Cys in peptides and proteins would react with CBT derivatives only when it is present at the N-terminal position (since the amino group is needed free for the reaction). The reaction proceeds under aqueous conditions at physiological temperatures and pressures. The CBT/1,2-aminothiol combination is thus a bioorthogonal reaction (Figure 1).1-3
Figure 1: Bioorthogonal reaction between CBT and 1,2-aminothiol
The Hydroxy group present on Hydroxy-CBT offers you the possibility to derivatize the CBT moiety with any molecule of interest.
Hydroxy-CBT can also be used for bioluminescence purposes since the reaction of Hydroxy-CBT with D-cysteine allows the formation of D-luciferin, a substrate for Firefly Luciferase.1