Figure 4.

Beacon binds an oligomer more tightly than misfolded ribozyme. Equilibrium titrations of MB-P3 with complementary target RNA in splicing buffer without MgCl₂ at 37°C. RNA oligomer target (closed circle), 15 nt oligomer plus 2 nM MB-P3, K_d = 4.0 ± 0.4 nM; (closed square), L-21 ribozyme plus 50 nM MB-P3, K_d ≈ 400 nM. The fraction of bound probe is proportional to the change in fluorescence, ΔF. For ribozyme titration, the maximum fluorescence was adjusted so that the fitted curve saturated near 1.