Merck, A9275-100MG, Avidin from egg white

Avidin protein is a homotetrameric protein (68kDa) that is obtained from egg whites. This egg protein binds strongly to biotin. Thus, avidin-biotin association has been utilized in immunoassays to detect the localization of antigens in tissues. The use of avidin-biotin immunoassay enhances the sensitivity of the technique and facilitates the detection of antigens in low quantities.