Guanosine 5'-triphosphate-5'-adenosine (GpppA) triammonium, a 5′ cap analog, can be used for RNA synthesis in vitro. Guanosine 5'-triphosphate-5'-adenosine triammonium is a fluorescent substrate analog.
Guanosine 5'-triphosphate-5'-adenosine (GpppA) triammonium labeled with pyrene at the 3′-O position of adenosine acts as an artificial substrate. Fluorescently labeled GpppA triammonium and GpppG analogs as potential substrates that represent a reasonable compromise between the structural complexity and requirements of the enzyme[1].