With SF350, containing the 27-nt L2, the situation is different. In this mutant some of the triples may still form but the additional unstructured 18 nt are expected to introduce a substantial entropic penalty into the system, which increases DG and therefore reduces frameshifting. In addition, a large loop may lead to a longer refolding time of the pseudoknot once a ribosome has passed through this structure.