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 AP (alkaline phosphatase)-streptavidin conjugate comprises streptavidin (as the biotin-binding protein) with HRP covalently attached (as the enzyme label). It is commonly used as a second step reagent for indirect immunofluorescent staining, when used in conjunction with a HRP substrate (such as our sensitive fluorogenic ADHP peroxidase substrate). It is a very valuable tool for biotin-streptavidin-based biological assays and tests. A variety of the complementary biotinylated reagents are available from numerous commercial vendors.