5-F-dU (Figure 1) can pair with purine bases (so, A and G). Importantly, the pairs A:(5-F-dU)and G:(5-F-dU) are more stable than A:T and G:T, the latter being a mismatched base pair. Thanks to this characteristic, insertion of 5-F-dU in hybridization probes allows the creation of unique, highly selective probes, which can be used for cDNA library screening.
Figure 1. Structure of 5-Fluoro-dU at the 5'-end (R = sequence).
metabion offers 5-Fluoro-dU as a modification in its DNA and RNA portfolio:
Habener JF., Vo CD., Le DB., Gryan GP., Ercolani L., Wang AH. 5-Fluorodeoxyuridine as an alternative to the synthesis of mixed hybridization probes for the detection of specific gene sequences. Proc Natl Acad Sci U S A. 1988 Mar;85(6):1735-9.