PE-Cy5 is a tandem dye that belongs to the phycobiliprotein conjugate family. In this type of tandem dye, the excitation energy can be transferred from PE to the Cy5, with the maximum emission wavelength being that of the Cy5. PE-Cy5 has minimal spectral overlap with FITC and PE, resulting in low fluorescence interference. Therefore, it is often used in combination with FITC and PE in experiments. It is important to note that PE-Cy5 is not suitable for pairing with APC as they have a significant spectral overlap. In contrast to PE-Cy5, PE-Cy5.5 has minimal fluorescence interference with FITC, PE, and APC, making it compatible for use in combination with these dyes. Additionally, PE-Cy5.5 exhibits higher fluorescence intensity compared to PE-Cy5. PE-Cy7 has no spectral overlap with FITC and minimal overlap with APC, allowing it to be used in combination with FITC, PE, and APC. However, it is crucial to note that PE-Cy7 is highly susceptible to photobleaching and requires a strictly light-protected environment during experiments.