Tris(2-carboxyethyl)phosphine hydrochloride, 98%+ Cas 51805-45-9 - used as a reducing agent to break disulfide bonds within and between proteins as a preparatory step for gel electrophoresis.  Tris(2-carboxyethyl)phosphine hydrochloride, 98%+ Cas 51805-45-9 - used for this purpose (dithiothreitol and β-mercaptoethanol), TCEP has the advantages of being odorless, a more powerful reducing agent, an irreversible reducing agent (in the sense that TCEP does not regenerate—the end product of TCEP-mediated disulfide cleavage is in fact two free thiols/cysteines), more hydrophilic, and more resistant to oxidation in air. It also does not reduce metals used in immobilized metal affinity chromatography.