To improve the recruitment of the catalytically active Ce(IV) ion to the DNA cleavage site in the ARCUT (Artificial Restriction DNA Cutter) system, two phosphonate ligands, nitrilotris(methylenephosphonic acid) (NTP) and N,N,N',N'-ethylenediaminetetra-(methylenephosphonic acid) (EDTP), have been linked to the 5'- or 3'-end of oligonucleotides complementary to the target DNA. Compared to their counterparts bearing a terminal monophosphate, these new modified oligonucleotides exhibit a modest to significant increase in the cleavage activity, depending on the target.