Cy3 maleimide chloride is a Cyanine 3 (Cy3) dye derivative that includes maleimide functional groups. Cy3 exhibits fluorescence in the green to orange wavelength range. The alkyne group in Cy3 maleimide chloride facilitates a "thiol-acrylamide" reaction with sulfur-oxygen functional groups to create covalent bonds. It can attach to biological molecules like proteins and antibodies, enabling the tracking of their location and dynamic changes in biological samples.