Coaxial Stacking
From Eterna Wiki
Coaxial stacking is a tertiary interaction where separate stacks in an RNA align along a common axis.
Flush vs. Mismatch-Mediated Stacking ===
n flush stacking, the coaxially-stacked helices are not separated by any unpaired bases. This is depicted in panel C to the right.
In mismatch-mediated stacking, the coaxially-stacked helices are separated by one or more unpaired bases. This is depicted in panels B and D in the figure at right.