The abundance of NOEs indicates significant base stacking interactions, which likely contribute to ordering of the tail. To probe the thermodynamic stability of the tail, we performed UV/Vis melting experiments to determine the melting temperature of the helix to coil transition. Consistent with previous studies of single-stranded nucleic acids, the melting profile of the ssRNA is extremely broad, characteristic of a non-cooperative transition (Figure 2A ) (37) . Previous studies of a 7 nt polyadenine ssRNA in similar buffer conditions yield analogous melting temperatures to those observed ($35 C compared to 31.7 ± 1.90 C) (37) .