Cy3 maleimide is a selective and efficient fluorophore dye with low aqueous solubility. This labeling reagent can be used to attach Cy3 fluorophore to proteins and peptides which contain cysteine residues, as well as to other thiolate molecules (such as thiol-containing oligonucleotides). Before the labeling reactions, Cystines should be reduced with TCEP (tris-carboxyethylphosphine). 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.
