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 amino group present on amino-CBT offers you the possibility to reversibly couple to aldehydes and ketones to form a Schiff base which can be reduce to generate stable amine derivative. Carboxylic acid or isothiocyanate can be coupled to this molecule in aqueous solution.
Amino-CBT can also be used for bioluminescence purposes since the reaction of Amino-CBT with D-cysteine allows the formation of D-aminoluciferin, a substrate for Firely Luciferase.1