Self-association of cyclic oligonucleotides through G:T:G:T minor groove tetrads Original Research Article

Minor groove aligned tetrads resulting from the association of Watson–Crick base pairs stabilize a distinct class of four-stranded DNA structures, different from G-quadruplexes or i-motifs. These tetrads can be formed by several arrangements of G–C or A–T base pairs. Here we prove that minor groove tetrads can be also formed by G–T mismatches. In this manuscript we describe the dimeric solution structures of two cyclic oligonucleotides stabilized by intermolecular G–T non-canonical base pairs. In the dimeric structure of d, these mismatches interact to each other giving rise to minor groove aligned G:T:G:T or mixed G:T:G:C tetrads. Interestingly, the stability conferred by mismatched G–T containing tetrads is similar to that of minor groove tetrads solely formed by G–C Watson–Crick base pairs.