Global Analysis of Myocardial Peptides Containing Cysteines With Irreversible Sulfinic and Sulfonic Acid Post-Translational

Cysteine (Cys) oxidation is a crucial post-translational modification (PTM) associated with redox signaling and oxidative stress. As Cys is highly reactive to oxidants it forms a range of post-translational modifications, some that are biologically reversible (e.g. disulfides, Cys sul-fenic acid) and others (Cys sulfinic [Cys-SO2H] and sul-fonic [Cys-SO3H] acids) that are considered “irreversible.” We developed an enrichment method to isolate Cys-SO2H/SO3H-containing peptides from complex tissue ly-sates that is compatible with tandem mass spectrometry (MS/MS). The acidity of these post-translational modifica-tion (pKa Cys-SO3H < 0) creates a unique charge distri-bution when localized on tryptic peptides at acidic pH that can be utilized for their purification. The method is based on electrostatic repulsion of Cys-SO2H/SO3H-containin