Used as an irreversible inhibitor of cysteine proteases, particularly in biochemical research to study enzyme mechanisms. It modifies the active site by alkylating the catalytic cysteine residue, allowing scientists to probe catalytic activity and structure-function relationships in proteolytic enzymes such as cathepsins and papain. Commonly applied in the control of unwanted enzymatic degradation during protein purification. Also utilized in the development of affinity labels and in mechanistic studies of protease-dependent pathways in cell biology, including apoptosis, inflammation, and cancer cell metastasis. Additionally, employed in protein labeling to track the distribution or presence of target proteins in cells.