Tandem dyes are a unique class of fluorescent molecules that consist of two different covalently linked fluorophores, a donor (e.g. PE or APC) and a longer-wavelength emitting fluorescence acceptor (e.g. Texas Red, Cy5, Cy7, iFluor® 594 or iFluor® 750). PE-iFluor® 597 is a superior replacement to the commonly used PE-Texas Red tandem with significantly improved FRET efficiency and signal/background ratio. Its primary absorption peak is at 565 nm with emission peak around 610 nm. AAT Bioquest also offers a unique preactivated PE-iFluor® to facilitate the PE- iFluor® 597 tandem conjugation to antibodies and other proteins such as streptavidin and other secondary reagents. PE-iFluor® 597 has emission of ~614 nm with superior signal compared to other spectrally similar PE tandems.