Boc-protected Cy5 hydrazide is a reactive dye for the labeling of aldehydes and ketones with high aqueous solubility. Trifluoroacetic acid or other strong acid can remove the Boc-(tert-butoxycarbonyl) protective group. Reactive hydrazide can couple with various carbonyl groups yielding Cy5-labeled molecules. 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.
