Sulfo-Cyanine5.5 is a water soluble cyanine dye for far red / NIR applications such as in vivo imaging. The dye possesses four sulfonate groups that render it highly hydrophilic and water soluble. As well as other cyanines, sulfo-Cyanine5.5 has an outstanding extinction coefficient that makes it a bright fluorescent label for the far red region.

This is an amine-containing fluorescent dye. The amine group is separated from the fluorophore by a relatively long linker that facilitates conjugation. The aliphatic primary amine group can be coupled with various electrophiles (activated esters, epoxides, etc), and also be used in enzymatic transamination labeling.