Synthesis of and triplex formation in oligonucleotides containing 2'-deoxy-6-thioxanthosine.

This study aimed to synthesize triplex-forming oligonucleotides (TFOs) containing 2'-deoxy-6-thioxanthosine (s ⁶ X) and 2'-deoxy-6-thioguanosine (s ⁶ Gs) residues and examined their triplex-forming ability. Consecutive arrangement of s ⁶ X and s ⁶ Gs residues increased the triplex-forming ability of the oligonucleotides more than 50 times, compared with the unmodified TFOs. Moreover, the stability of triplex containing a mismatched pair was much lower than that of the full-matched triplex, though s ⁶ X could form a s ⁶ X-GC mismatched pair via tautomerization of s ⁶ X. The present results reveal excellent properties of modified TFOs containing s ⁶ Xs and s ⁶ Gs residues, which may be harnessed in gene therapy and DNA nanotechnology.
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