DL-Dithiothreitol

DL-Dithiothreitol is capable of maintaining monothiols completely in the reduced state and of reducing disulfides quantitatively. Thiol groups such as those of coenzyme A are readily oxidized in air to disulfides. To maintain these groups in the reduced state, another thiol is often added so that interchange takes place. Since DL-dithiothreitol is a highly alcohol- and water-soluble solid with little odor and little tendency to be oxidized directly by air, it proves much superior to the thiols currently used as protective reagents for sulfhydryl groups. DL-Dithiothreitol is commonly used in a variety of experiments that involve peptides or proteins, protecting sulfhydryl groups from oxidation and reducing disulfide bonds between cysteines. DL-Dithiothreitol also acts as an "antidote" enabling the activity of detoxification systems, and is used in the treatment approach of diseases like cystinosis or medical conditions resulting from ion or metal toxicity. 

References:

1. Cleland WW. Dithiothreitol, a new protective reagent for SH groups. Biochemistry, 1964, 3: 480-482.

2. Lopes de Almeida JP, Saldanha C. Dithiothreitol revisited in red cells: a new head for an old hat. Clinical Hemorheology and Microcirculation, 2010, 46(1): 51-56.