FIGURE 6.
Brønsted plot of the rescue data for the C75ΔC41Δ variant. For each reaction, the log of the normalized rate constants was plotted against the pKa of the base used in the reaction. The slope of the line fit to these data is 0.47 (R = 0.97). For 2-amino-1,2,4-triazole, 4-hydroxylmethylimidazole, imidazole, and 4-methylimidazole, k max values from independent pH-rate curves of the rescue reactions were used. For 3-aminopyrazole, the rate constant used was the k obs obtained from the initial slope of 24–48-h reactions at pH 7.6 (∼15% cleavage in 24 h).