TCEP (tris(2-carboxyethyl)phosphine) is a reducing agent frequently used in biochemistry and molecular biology applications.

It is soluble in water and available as a stabilized solution at neutral pH and immobilized onto an agarose support to facilitate removal of the reducing agent.

[1] TCEP is often used as a reducing agent to break disulfide bonds within and between proteins as a preparatory step for gel electrophoresis.

TCEP can keep the cysteines from forming di-sulfide bonds and, unlike dithiothreitol and β-mercaptoethanol, it will not react as readily with the maleimide.

Reduction of biomolecules with trialkyphosphines received little attention for decades because historically available phosphines were extremely malodorous and/or insoluble in water.