Mg2+ mechanics may assist folding counter to expectations.

In summary, this work clearly reveals that [Mg2]-mediated formation of an isolated TL-R tertiary interaction (i) is of an entropic origin, directly counter to traditional expectations for the role of Mg2 in tertiary RNA folding, and (ii) involves a sig-
nificantly complex interplay between the ion atmosphere and the docked vs. undocked RNA structures along the folding pathway.

http://www.pnas.org/content/early/201…