Triplex forming ability of oligonucleotides containing 2'-O-methyl-2-thiouridine or 2-thiothymidine.

Abstract The triplex forming ability of oligonucleotides containing 2′- O -methyl-2-thiouridine (s 2 Um) and 2-thiothymidine (s 2 T) was studied. The UV melting experiments revealed that triplex forming oligonucleotides (TFOs) containing both s 2 Um or s 2 T stabilized significantly parallel triplexes. The main reason for stabilization of triplexes was due to the stacking effect of the 2-thiocarbonyl group. Moreover, it turned out that these modified TFOs had a high selectivity in recognition of a matched Hoogsteen base from a mismatched one.