Figure 3. The numbers of tandem mass (MS/MS) spectra are shown for the 7 -SH group-containing peptides of water-soluble nuclear γB -crystallin. A shows total counts for each of the 7 peptides containing an −SH group; B shows peptides containing protein-bound glutathione (PSSG) expressed as per −SH peptide; and C shows peptides containing protein-bound cysteine (PSSC) expressed as per −SH peptide. Open bars are counts from age-matched controls and solid black bars are counts after 30 treatments of the animals with hyperbaric oxygen. There is a different vertical scale for A, compared to those for B and C, which are identical. The counts in panel A correspond to a soluble protein sample of 0.4 mg. Residue C42 showed a relatively high number of peptide counts for control and O₂-treated samples due to the peptides containing C42 being identical in sequence for γA-, γB- and γC-crystallins (A). No detectable counts were obtained for residues C33 and C79 for either the control or O₂-treated samples. Residues C16 and C23 accounted for the majority of O₂-induced PSSG (B) and PSSC (C).