Conjugates prepared with the thiol-reactive Alexa Fluor® 680 C₅ maleimide are spectrally similar to the Cy5.5 dye. With an emission maximum at 702 nm, the Alexa Fluor® 680 dye is well separated from that of other commonly used red fluorophores, such as the tetramethylrhodamine, Texas Red®, R-phycoerythrin (R-PE) and Alexa Fluor® 594 dyes.