Adduct formation of electrochemically generated reactive intermediates with biomolecules

• Electrochemistry-mass spectrometry (EC-MS) to study the oxidative metabolism.
• Studying the detoxification of reactive intermediates using EC-MS.
• Simulating the detoxification of reactive metabolites with endogenous nucleophiles.
• Protein modification achieved by electrochemically-generated reactive metabolites.
• Electrochemical tagging of cysteine moieties informs on protein identification.

Electrochemistry (EC) has turned out to be a valuable tool for the elucidation of reactive oxidation products of pharmaceuticals and ingredients of personal care products when investigating the affinity towards biomolecules, such as peptides or proteins containing nucleophilic groups. The combination of EC with liquid chromatography (LC) and mass spectrometry (MS) allows investigation of adduct formation, identification of reactive metabolites prior to binding, localization of active binding sites in a biomolecule and monitoring of isomer formation. The first part provides an overview on studies on formation of covalent conjugates. The second part presents several methods, which are dedicated to tagging cysteine moieties in biomolecules. The generation of electrophilic intermediates enables the selective reaction of these species with the nucleophilic thiol group in cysteine. Thus, counting of cysteines in proteins and mass fingerprinting of cysteine containing tryptic peptides is accomplished.