sdAbs, including the variable domain of camelid heavy-chain antibody (VHH) and the variable domain of the new antigen receptor (VNAR) in sharks, are known to be remarkably stable. For example, sdAb can be engineered to have high thermodynamic stability, stability against unfolding with chemical denaturants, or protease resistance. The high stability of sdAb is mainly attributed to its efficient refolding after chemical or thermal denaturation and to a lesser extent because of increased resistance against denaturation. The excellent biochemical and biophysical properties (e.g., high chemical and physical stability, thermal tolerance, and proteolytic resistance) lead to the successful application of sdAbs for diagnostic. Moreover, the exceptional stability of sdAb opens the possibility for nonconventional therapeutic applications and alternative routes of administration, such as oral administration. https://www.creative-biolabs.com/sdab/disulfide-bond-influence-of-single-domain-antibody-sdab-stability.htm