Promotion of stable triplex formation by partial incorporation of 2′,5′-phosphodiester linkages into triplex-forming oligonucleotides

Pentadecamer homopyrimidine oligonucleotides containing three or more 2',5'-phosphodiester linkages in different modes were prepared and used to evaluate the ability as a triplex-forming oligonucleotide (TFO), and it was found that discontinuous replacement of the 3',5'-phosphodiester linkages in TFO by 2',5'-linkages significantly stabilizes parallel-motif triplexes.