Fig. 2.

Inactivation of CrHydA1 by O₂ by simultaneous gas exchange and injection of O₂-saturated buffers. Experiments were carried out under (A) different concentrations of O₂ and (B) different concentrations of H₂. (A) Gas mixtures in the headspace contain 80% H₂ and the remaining 20% are as indicated. For the experiments in which inactivation was induced by 10% and 5% O₂, injections of 2 mL and 0.67 mL buffer saturated with 20% O₂ and 80% H₂ (respectively) were performed into the cell containing 2 mL at the beginning of the experiment. For the experiments in which inactivation was induced by 0.5% O₂, an injection of 0.5 mL buffer saturated with 2.5% O₂ and 80% H₂ was performed into the cell containing 2 mL at the beginning of the experiment. (B) Inactivation was achieved with 5% O₂ in the headspace and the solid and dashed lines represent experiments performed with 8% and 80% H₂, respectively. For the experiments in which inactivation was induced by 5% O₂ in 8% H₂, an injection of 0.67 mL buffer saturated with 20% O₂ and 8% H₂ was performed into the cell initially containing 2 mL. Other conditions: pH 6.0, 20 °C, electrode rotation rate 3,000 rpm, −0.05 V vs. SHE.