Incorporation of a Novel Nucleobase Allows Stable Oligonucleotide‐Directed Triple Helix Formation at the Target Sequence Containing a Purine×Pyrimidine Interruption.

Thermal denaturation experiments have established that an oligonucleotide incorporating the artificial nucleobase S, does form a stable triplex with a double stranded DNA which exhibits a pyrimidine interruption within the oligopurine sequence.