2-Nitro-5-thiocyanatobenzoic Acid

2-Nitro-5-thiocyanatobenzoic Acid (CAS No.: 30211-77-9) is a highly reactive thiocyanating reagent widely employed in biochemical and chemical biology research for the selective modification of thiol-containing biomolecules. Functionally categorized as a sulfhydryl-reactive probe, it rapidly transfers a cyano group to nucleophilic thiolate moieties, enabling the conversion of cysteine residues in proteins into S-cyano derivatives, a transformation that can induce predictable alterations in protein conformation, stability, and activity. This reactivity underpins its utility in probing thiol-dependent regulatory mechanisms, investigating redox-sensitive signaling pathways, and performing site-specific protein modification in vitro. Although it does not act through classical receptor-mediated pathways, its mechanism directly targets accessible thiol groups, making it a valuable tool for studying post-translational modifications and protein structure–function relationships. Reported activity is typically observed at low micromolar to millimolar concentrations depending on substrate accessibility and experimental conditions, with outcomes influenced by protein context and buffer composition. In laboratory settings, it is frequently applied in protein engineering, peptide mapping, and biochemical assay development, including studies in purified protein systems and cell lysates, where concentrations and exposure conditions are optimized according to specific experimental objectives.