Stability of cysteine at 70°C under different experimental conditions.

(A) Time evolution of cysteine concentration during incubation in 50 mM phosphate solution at different pHs. Lines correspond with exponential decay fits. Corresponding rates are shown in (B): median ± IQR (N ≥ 3) (see S1 Data). (C) For those conditions of intermediate pH, cysteine time courses were reanalyzed both in absence and presence of increasing concentrations of the substrate, 6PG, with just very slight changes detected. Corresponding rates are shown in (D): median ± IQR (N ≥ 3) (see S1 Data). In all experiments, cysteine concentration was quantified spectrophotometrically using Ellman’s reagent (see Materials and methods and Supporting information Methods in S1 Text). 6PG, 6-phosphogluconate.

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