Fig. 6.

Comparison of the thermal unfolding of the WT*, ΔA35, ΔA35/U33C, ΔA35/C34U, and ΔA35/A36U SL1 RNAs. The experimental optical melting profiles show every fifth data point collected at 260 nm (•) and 280 nm (○), with the calculated fits (dashed lines) shown. For the ΔA35 RNA, the nonlinear least-squares simultaneous composite fit to a single transition unfolding model, and the transition is shown in solid line. For the WT* model and three recovered SL1 mutant ΔA35/U33C, ΔA35/C34U, and ΔA35/A36U RNAs, a nonlinear least-squares simultaneous composite fit to a two-transition unfolding model, and component transitions 1 and 2 (solid lines) are shown. The thermodynamic parameters derived from these fits are compiled in Table 2.