Figure 2.
Molecular crowding overcomes destabilizing RNA mutations. Folding transitions from the unfolded state (U) to the compact native-like intermediate (IC) were measured by SAXS at different [Mg2+]. Filled symbols indicate experimental data on the WT ribozyme; lines show the best fit of the data to a 3-state partition function (Equation 1). Light lines indicate fitted transitions for one of the seven possible single, double or triple L2, TH and L9 mutants; see data in Supplementary Figure S3. No PEG, blue/light blue; 18% PEG1000, red/pink. All experiments were done with 0.4 mg/ml RNA equilibrated in 20 mM Tris–HCl, pH 7.5 plus the desired [MgCl2] at 37°C. (b) Normalized P(r) of the folded RNAs in 2 mM MgCl2 in water or in 18% PEG1000. Colors as in (a).