[A–I] Oxidative cysteine modification. Cysteine residues in proteins can be modified by oxidation and the negative charge may change protein function. GHS, glutathione; GSNO, S-nitrosoglutathione; S-GSH, S-glutathionylation; SH, protein thiol of cysteine; S-S, disulfide band; SOH, sulfenic acid; SO2H, sulfinic acid; SO3H, sulfonic acid; SNO, S-nitrosylation.