An excellent reagent for maintaining SH groups in reduced state; quantitatively reduces disulfides. DTT is effective in sample buffers for reducing protein disulfide bonds prior to SDS-PAGE. DTT can also be used for reducing the disulfide bridge of the cross-linker N,N′-bis(acryloyl)cystamine to break apart the matrix of a polyacrylamide gel. DTT is less pungent and is less toxic than 2-mercaptoethanol. Typically, a seven fold lower concentration of DTT (100 mM) is needed than is used for 2-mercaptoethanol (5% v/v, 700 mM).