Learning Center – Thiol Chemistry

Thiol blockers, typically iodoacetamide (IAM) or N-ethylmaleimide (NEM), are utilized in numerous redox analytical workflows to prevent oxidative artifacts during specimen processing and to stabilize oxidative modification at cysteine residues which would otherwise react with the reduced cysteines (e.g., resolution of -SOH into disulfides, thiol-disulfide shuffling,  and other thiol-mediated reactions). Earlier work by Reisz et al ¹ discovered the lack of selectivity of IAM, NEM, and other reagents towards reduced thiols (-SH) due to the cross-reaction with sulfenylated cysteines (-SOH). This has led to new research and the discovery of MSTP (4-(5-(methylsulfonyl)-1H-tetrazol-1-yl)phenol) as a new cell membrane permeable thiol-selective reagent ².