Sulfo-Cyanine5.5 amine, which consists of four sulfonate groups and is highly hydrophilic, is an amine-containing fluorescent dye. The aliphatic primary amine group can be coupled with various electrophiles (activated esters, epoxides, etc.). Sulfo-Cyanine5.5 amine is utilized in far-red/NIR applications (such as in vivo imaging) and enzymatic transamination labeling [1].