Isotope-coded chemical reporter and acid-cleavable affinity reagents for monitoring protein sulfenic acids

We have developed an approach that allows relative quantification of protein sulfenic acids using a pair of light and heavy isotope labled probes, DAz-2 and d6-DAz-2. In conjunction with a new complementary acid-cleavable linker, Yn-ACL, we demonstrate that tagged peptides are successfully labeled, enriched, and fully characterized by LC-MS/MS analysis. Overall, this method can be applied to map sites of cysteine oxidation and compare protein sulfenylation in normal and disease states.