The addition of a reducing agent to an assay may be important to prevent the oxidation of cysteines in the proteins being studied and thus the formation of disulfides. The most commonly used reducing agents are dithiothreitol (DTT), β-mercaptoethanol (β-ME) and tris(2-carboxyethyl)phosphine (TCEP).

2-mercaptoethanol or β-mercaptoethanol or BME is a chemical compound of the formula HOCH2CH2SH, a "hybrid" of ethylene glycol and ethanedithiol. At room temperature it is a liquid with a foul-smelling odor. The presence of the thiol -SH function makes 2-mercaptoethanol a reducing agent widely used in biochemistry to protect proteins against oxidation.

The denaturation of proteins requires the reduction of disulfide bridges, which are crucial for the tertiary or quaternary structure of certain proteins. It is commonly used to reduce disulfide bridges present in proteins and can play a role as a biological antioxidant. It is also used because of its hydroxyl group, which makes it miscible in water and reduces the volatility (and therefore the odor) of thiol.

2-Mercaptoethanol is a powerful reducing agent used in cell culture media to prevent toxic levels of oxygen radicals.