PARK7 and Parkinson disease: Researchers used a novel quantitative mass spectrometry approach to measure relative changes in oxidation at specific sites in mutant DJ-1 compared to the wild-type protein and found that the M26I familial substitution and methionine oxidation characteristic of sporadic PD may disrupt DJ-1 function by disfavoring a site-specific modification required for optimal neuroprotective activity, indicating the effect of a single amino acid substitution on oxidative modifications of the PD-related protein DJ-1 [65].