Phycobiliproteins—such as PE, APC, and PerCP—are intensely bright due to their high molar extinction coefficients and quantum yields; an enviable quality when imaging low-abundance targets. These fluorophores have extensive uses in flow cytometry and FACS, but there are some limits to their applications. Useful guidelines include:

1. Phycobiliproteins photobleach rapidly, so they are not recommended for microscopy.
2. Take experiment length into account. PerCP tandem structure may make it more photostable than PerCP alone. Choose the label best suited to time requirements.
3. PerCP tandems are highly sensitive. A long-wavelength paired fluorophore may reduce background noise. Cy5 & Cy5.5 are common options, but select based on your experimental needs.