Activator solution, containing powerful activators like 4,5-dicyanoimidazole(DCI), 5-(3,5-bis(trifluoromethyl)phenyl)-1H-tetrazole (Activator 42) or5-(Ethylthio)-1H-tetrazole (ETT) in acetonitrile, are mixed with solutions ofphosphoramidites during the extension step. The activator reacts with theamidite group to form a highly reactive intermediate. The intermediate thenforms an internucleotide bond with the detritylated 5′hydroxyl group of thegrowing oligonucleotide chain.

• Preparation Note: Dicycanoimidazole/Acetonitrile 6/100 (w/v)