Cy3 Protein Labeling Kit is an innovative technology that enables direct labeling of proteins, peptides or other biomolecules. Cyanine dyes are commonly used as fluorescent labels for proteins, nucleic acids and small molecules. Cyanine Dye 3 (Cy3) has a strong absorption peak at 550nm and a secondary absorption peak at 520nm. The maximum emission peak is at 570nm, with an excitation coefficient of 1.5 x105 cm-1 M-1.