4,4′-Diisothiocyanatostilbene-2,2′-disulfonic acid is an anionic alkylating agent containing isothiocyanate residue. It is a negatively charged homobifunctional cross-linking reagent. 4,4′-Diisothiocyanatostilbene-2,2′-disulfonic acid is a specific inhibitor of cellular anion permeability used in cell transport studies. The isothiocyanate groups react with primary amines at pH 9.0-10.0. 4,4′-Diisothiocyanatostilbene-2,2′-disulfonic acid alkylates lysine residues and inhibits apoptosis indirectly by targeting membrane based anion transporters.In addition, it also inhibits calcium transport in vesicles.