What are tandem dyes? What is the advantage of using tandem dyes?

Tandem dyes are composed of two covalently attached fluorophores or fluorescent molecules. One of the molecules serves as a donor, the other serves as the acceptor. Tandem dyes behave as unique fluorophores with the excitation properties of the donor and the emission properties of the acceptor. This is possible through the phenomenon of fluorescence resonance energy transfer (FRET), which involves the transmission of energy between two fluorescent molecules placed in close proximity. Examples of tandem dyes include PE-Cy5, PE-Cy7, APC-Cy7, and PE-Atto 594.

The advantage of using tandem dyes is that they allow for more markers to be assessed in a single experiment.