Wittig reagents for chemoselective sulfenic acid ligation enables global site stoichiometry analysis and redox-controlled mitochondrial targeting

This study introduces a class of Wittig alkyne (WYne) reagents for chemoselective and quantitative detection of cysteine sulfenic acids (Cys–SOH) in proteins. These triphenylphosphonium-based reagents react rapidly and selectively with sulfenic acids under physiological conditions, forming stable adducts suitable for mass spectrometric analysis. The authors demonstrate that WYne probes outperform traditional dimedone analogs in reactivity—up to 1,500-fold faster—while maintaining high selectivity and cellular compatibility. Their modular design also allows mitochondria-targeted variants, enabling site-specific analysis of redox regulation within this organelle. Using quantitative proteomics, the team measured global sulfenylation stoichiometry and identified redox-sensitive cysteines involved in metabolic control and stress response. This work expands the chemical toolkit for studying oxidative post-translational modifications, establishing Wittig reagents as versatile probes for mapping cysteine oxidation dynamics and uncovering mechanisms of redox signaling and mitochondrial regulation in living systems.