Selective cross-linking to the adenine of the TA interrupting site within the triple helix

The triplex-forming oligonucleotide incorporating the new nucleoside derivative (Figure 1 and Figure 3) that connects the 2-amino-6-vinylpurine moiety to the 2-deoxyribose unit with an ethyl spacer has exhibited highly selective cross-linking reaction to the adenine of the TA interrupting site within the triple helix.