FIGURE 2.

RNA phase transition is dependent on RNA identity and magnesium concentration. (A) 2.5 µM Guanidine riboswitch (CF-647-labeled, ∼13% labeled RNA) was renatured in the presence of 10 mM HEPES (pH 7.0) and the indicated amounts of Mg²⁺. Contrast of the images was increased to aid in visualization at lower Mg²⁺ levels. (B) Same as A but with Guanine riboswitch (CF-488-labeled, ∼10% labeled RNA). Note that the CF-647 label is essential to visualization: When 10 µM Gdn RNA was used (Fig. 1B) as opposed to 2.5 µM (A), no condensates were visible in the absence of PEG 8K at the 10 mM Mg²⁺ with DIC visualization (Fig. 1B, panel 5).