Interactions of loop 2 nucleotides with stem 1 base pairs (carbon atoms colored in blue and yellow, respectively). Formation of the minor groove triplex is RNA-specific as 2’-hydroxyl groups are involved at every level. a, A20 interacts with two base pairs of stem 1 (G3:C16 and C4:G15), and multiple hydrogen bonds involving 2’-hydroxyl groups can be clearly seen. b, interactions between A21/C22 and C4:G15. c, Interaction between A23 and G5:C14. d, interaction between A24 and G6:C13. Note that loop 2 (blue) moves from one strand of stem 1 to the other between A21 and A24.