Cy®3 is a bright, water-soluble, and pH insensitive orange-fluorescent dye that can be excited using the 532 nm or 555 nm laser line and visualized with TRITC (tetramethylrhodamine) filter sets. Cy3 conjugates give less background than TAMRA and most other commonly used fluorescent dyes.
The maleimide derivative of Cy®3 dye is the most popular tool for conjugating the dye to a thiol group on antibodies, cysteine-containing peptides and other thiol-containing molecules. The maleimide group specifically and efficiently reacts with reduced thiols (sulfhydryl groups, –SH) at pH 6.5 to 7.5 to form stable thioether bonds.
This sulfonated dye is also known as sulfo-Cyanine3 Maleimide. Cy®Dye is a trademark of GE Healthcare.