Elemental labelling and mass spectrometry for the specific detection of sulfenic acid groups in model peptides: a proof of concept.

Oxidative transformation of cysteine thiol groups into different functional groups is considered a significant posttranslational modification of great importance in pathological and physiological processes. A cysteine sulfenic acid (SA) residue is the transient state for thiol group oxidation and it can react with free thiols to form disulfide bonds or can be further oxidized with reactive oxygen/reactive nitrogen species (ROS/RNS) to form sulfinic and sulfonic acids. The increase in ROS/RNS concentrations is correlated to age-related diseases such as cancer and Alzheimer's disease. Since the formation of SA represents a transient state of oxidation of thiols, its formation can be considered a redox-sensitive sensor for the presence of ROS/RNS. Thereby, the detection of the short-lived SA will provide greater insight into the redox-mediated events that alter the structure and function of peptides and proteins. The aim of this study is to provide a new strategy for the highly sensitive and specific detection of SA in peptides as a proof of concept. For this aim, SA was firstly generated in model peptides on oxidation with H