A disulfide bond, disulfide bridge, SS- bond or simply disulfide, is a functional group present in some proteins. It describes the covalent connection of two thiol groups, usually of cysteines, in the form of R–S–S–R’. Often, disulfides connect different parts or domains within a protein, contributing to its overall structural stability. A formation of a non-native (‘wrong’) disulfide bond usually results in a misfolded protein.

For disulfides to form and remain stable, the environment has to be oxidizing rather than reducing. Vice versa, free cysteines may require the presence of Reducing Agents for stabilization. Since the cytoplasm of eukaryotic cells is a reducing environment, cytosolic proteins rarely exhibit disulfide bonds. Some cellular compartments are oxidizing environments and contain proteins with disulfide bonds.

When designing an experiment, keeping the natural environment of the protein(s) of interest in mind, can help to select the correct Buffer conditions. The ideal method to perform buffer optimization is with the Buffer Exploration Kit (Cat# NT-B001) and the Buffer Screen experiment in DI.Control.