Cleavage activity assays of the env10 hatchet ribozyme and mutants. Secondary structure cartoons of the two-stranded construct used in the cleavage assays with crucial base interactions highlighted in red and respective mutants in blue. HPLC traces following cleavage activity of wild-type ribozyme (A) and mutants C20G G30C (B), C20U G30A (C), G31A C64U (D), G31c7G (E), G30c7G (F), and G30dG (G). R1 and R2 denote the substrate and ribozyme strands; C1 (orange) and C2 (green) denote cleavage products. Reaction conditions: 55 μM RNA each strand; 10 mM MgCl2, 100 mM KCl, 30 mM Hepes, pH 7.5, 23 °C. HPLC conditions: Dionex DNAPac column (4 × 250 mm2), 80 °C, 1 mL min−1, 0–60% buffer B in 45 min. Buffer A: Tris–HCl (25 mM), urea (6 M), pH 8.0. Buffer B: Tris–HCl (25 mM), urea (6 M), NaClO4 (0.5 M), pH 8.0.