MSD SULFO-TAG labeled Streptavidin may be used as a secondary detection reagent to generate electrochemiluminescence in MESO SCALE DISCOVERY assays. SULFO-TAG Streptavidin is used to report biotin-labeled molecules. It allows the use of commercially available biotinylated detection antibodies in MSD assays. The average molecular weight of SULFO-TAG Streptavidin is approximately 60 kDa.