Application Trifluorothymidine (Trifluridine, TFT) is a substrate used to study the specificity and kinetics of thymidine kinase(s). TFT after phosphorylation may be incorporated into DNA where is induces DNA-damage, consequently TFT is useful for studies of DNA repair mechanisms. TFT may also be used to study mechanisms of inhibition of thymidylate synthase(s).