Cy2 is the acronym for a popular cyanine dye that is a key member of a fluorophore series developed by Dr. Alan Waggoner and associates at Carnegie-Mellon University. Similar to the other cyanine reagents in the series (Cy3 and Cy5), Cy2 is intensely fluorescent and highly water-soluble. The Cy2 dye produces green emission when excited with blue light, exhibiting an absorption maximum at approximately 489 nanometers and an emission peak at approximately 506 nanometers. The signal generated by Cy2 can be readily detected using fluorescein filter combinations in fluorescence microscopy. When conjugated to primary or secondary antibodies, Cy2 and other cyanine dyes can be utilized to target specific cellular antigens, such as peroxisomal membrane protein 70 (PMP 70), which is found in high concentrations in the membranes of peroxisomes.

The Muntjac deer skin cells presented in the digital image above were members of an adherent culture stained for F-actin with Alexa Fluor 568 conjugated to phalloidin, and for DNA with 4',6-diamidino-2-phenylindole (DAPI). In addition, the culture was immunofluorescently labeled with the cyanine fluorophore, Cy2, conjugated to goat secondary antibodies that target mouse anti-peroxisomal membrane protein 70 (PMP 70), a key membrane component of peroxisomes. Images were recorded in grayscale with a QImaging Retiga Fast-EXi camera system coupled to an Olympus BX-51 microscope equipped with bandpass emission fluorescence filter optical blocks provided by Omega Optical. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.