Self-association of cyclic oligonucleotides through G:T:G:T minor groove tetrads.

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.