FIGURE 1.

The dependence of (M⁻¹ s⁻¹) for hydration (S = CO₂, Eq. 5) catalyzed by H64W HCA II on the concentration of (•) 1,2-dimethylimidazole at pH 8.3; (□) 4-methylimidazole at pH 7.9; (♦) 3,4-dimethylpyridine at pH 6.7; (▵) 4-methylpyridine at pH 6.1; and (▪) 3-methylpyridine at pH 5.8. Data were obtained by ¹⁸O exchange using solutions at 25°C containing 25 mM of all species of CO₂, with ionic strength maintained at a minimum of 0.2 M with sodium sulfate. No other buffers were added.