This Cy5.5 is a labeling reagent that ready for the use in Click Chemistry reaction which available as 10 mM solution in DMSO. As Cy5.5 azide is a far-red emitting dye, it can replace Alexa Fluor 680, and DyLight 680. Most derivatives of non-sulfonated cyanines have low aqueous solubility except for hydrochlorides of hydrazides and amines. For biomolecule labeling, the labeling reagent has low aqueous solubility, using of organic co-solvent to dissolve this molecular is necessary for efficient reaction. First, Cyanine dye should be dissolved in organic solvent and then added to a solution of biomolecule in appropriate aqueous buffer.