Dithiothreitol (DTT), also known as Cleland's reagent, is a small-molecule redox reagent. Its oxidized form is a disulfide-bonded 6-membered ring. DTT has an epimeric ('sister') compound, dithioerythritol (DTE).

TCEP. HCl has the advantages of being odorless, a more powerful reducing agent, an irreversible reducing agent, more hydrophilic, and more resistant to oxidation in air. Near complete reduction of disulfide bonds. DTT is a protective agent for reducing –S-S TO SH groups. Used as a strong reducing agent for proteins and enzymes.