Application 2',3'-Dideoxycytidine in cells, it is phosphorylated to the active triphosphate form, ddCTP, which acts as a substrate for HIV reverse transcriptase (Ki = 51 nM). It incorporates into viral DNA where it terminates chain elongation when the missing hydroxyl group is encountered. It is also is used as a DNA chain-terminating nucleotide for DNA sequencing methods based on the Sanger chain-termination method.