Figure 4: L-cysteine and Na₂S HPLC chromatograms and calibration curves.

A) Representative elution pattern of L-cysteine standards. B) Elution pattern of 0 – 25 μM Na2S standards incubated with 60 μM CysM and 1 mM OAS. Standards were run in triplicate and aligned to the largest peak marked with *. C) Comparison of L-cysteine and CysM-derived L-cysteine calibration curves plotting peak area versus sulfide/L-cysteine concentration. D) Low sulfide calibration curves (0–2 μM), Error bars reported as +/− the standard deviation of the three replicate samples. See Figure S2 for 0–2 μM chromatographs and unaligned chromatographs.