Thiol catalysis of selenosulfide bond cleavage by a triarylphosphine

The arylthiol 4-mercaptophenylacetic acid (MPAA) is a powerful catalyst of selenosulfide bond reduction by the triarylphosphine 3,3′,3′′-phosphanetriyltris(benzenesulfonic acid) trisodium salt (TPPTS). Both reagents are water-soluble at neutral pH and are particularly adapted for working with unprotected peptidic substrates. Contrary to trialkylphosphines such as tris(2-carboxyethyl)phosphine hydrochloride (TCEP), TPPTS has the advantage of not inducing deselenization reactions. We believe that the work reported here will be of value for those manipulating selenosulfide bonds in peptidic or protein molecules.