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 iFluor® 546-streptavidin conjugate comprises streptavidin (as the biotin-binding protein) with iFluor® 546 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. iFluor® 546-streptavidin conjugates has fluorescence excitation and emission maxima essentially identical to those of Alexa Fluor® 546 conjugates. These spectral characteristics make it an excellent alternative to Alexa Fluor® 546-streptavidin conjugate (Alexa Fluor® is the trademark of Invitrogen). It is a very valuable tool for biotin-streptavidin-based biological assays and tests. Under the same conditions we tested, iFluor® 546-streptavidin conjugate is brighter and more photostable than the corresponding Alexa Fluo® 546 conjugate. These spectral and labeling characteristics make the iFluor® 546 dye family a superior alternative to Alexa Fluor® 546.