4- (3-Tosyl-2- (tosylmethyl) propanoyl) benzoic acid

4- (3-Tosyl-2- (tosylmethyl) propanoyl) benzoic acid (Bis-sulfone Acid) is a strong covalent linker containing a free carboxylic acid and two tosyl groups. 4- (3-Tosyl-2- (tosylmethyl) propanoyl) benzoic acid permits sequential displacement of each tosyl group by thiol or amine nucleophiles through Michael addition. 4- (3-Tosyl-2- (tosylmethyl) propanoyl) benzoic acid enables covalent “stapling” of two reduced cysteine residues on a protein to restore disulfide bridges, while the free carboxylic acid can be transformed into amides or esters, making the molecule a versatile tool for protein engineering and bioconjugation.