Tris2carboxyethylphosphine

Tris(2-carboxyethyl)phosphine, commonly abbreviated as TCEP, is a phosphine-based reducing agent used to break disulfide bonds in proteins, peptides, and other biomolecules. It is widely employed in protein purification, sample preparation for electrophoresis, and various labeling or stabilization workflows because it efficiently reduces disulfides under mild conditions.

TCEP is highly water-soluble and notably stable in air, making it convenient for routine use in aqueous buffers. It functions effectively over a broad pH range and at room temperature, and it does not rely on thiol groups to act as a reducing agent. Because it lacks sulfur in its active moiety, TCEP does not introduce thiols into samples and is often described as odorless compared to some thiol-based reagents. It is commonly used in the free base form or as the hydrochloride salt (TCEP·HCl).

In practical terms, working concentrations are typically in the low millimolar range, such as 0.5–5 mM, depending on the application. Compared with dithiothreitol (DTT), TCEP is more resistant to oxidation and more stable during storage, but it can interact with certain downstream assays or reagents that are sensitive to phosphines or heavy buffers, so compatibility checks are advised.

TCEP is widely available from chemical suppliers and is valued for its robustness in laboratory workflows that require reliable disulfide reduction without introducing additional thiols. See also: DTT, disulfide reduction, reducing agents.