2-Ethynyl-ATP (2-EATP) is a modified nucleotide that is commonly used in enzymatic assays intended to analyse the binding of ATP to proteins or it can be used to investigate ATP-depended enzymes in various pathological conditions. 2-EATP is also suitable for in vitro polyadenylation of natural RNA by recombinant poly(A) polymerase. The click reaction can be performed under the same conditions as before.