Streptavidin conjugates are widely used together with a conjugate of biotin for specific detection of a variety of proteins, protein motifs, nucleic acids and other molecules since streptavidin has a very high binding affinity for biotin. This RPE-streptavidin conjugate comprises streptavidin (as the biotin-binding protein) with RPE covalently attached (as the fluorescent label). It is commonly used as a second step reagent for indirect immunofluorescent staining, when used in conjunction with biotinylated primary antibodies. It is a very valuable tool for biotin-streptavidin-based biological assays and tests using flow cytometry, microplate reader and microarray platforms. Some of our customers have used this RPE-streptavidin conjugate with Affymetrix's microarray platform and Luminex's XMAP® and XTAG® technologies (e.g., Bio-Rad's Bioplex assay system). A variety of the complementary biotinylated reagents are available from numerous commercial vendors.