Distribution of peptides containing sulfhydrated cysteine residues relative to their H/L ratios as determined by the BTA analysis of cell extracts isolated from C1 and P1 patient cells (indicated in A) and C2 and P4 fibroblasts (B). Values of H/L ratios are plotted against the number of identified peptides. The gray line marks the H/L ratio >2, consisting of cysteine-containing peptides in proteins from patient cell lines that exhibited higher reactivity with H2S compared with the respective control. Indicated on the X axes are representative sensitive cysteine peptides, which are common between the ones found in the RedoxDB database, and by the BTA assay. 