Fluorescent dye that is water-soluble and forms stable thioether bond with free thiol groups. In comparison with Alexa Fluor 700, Fluorescent Dye 700-I Maleimide are brighter with stronger absorption at 633nm. Fluorescence emission of Fluorescent Dye 700-I Maleimide is well separated from that of other commonly used red fluorophores, such as TAMRA, Fluorescent Dye 647-I and R-phycoerythrin, making it ideal for multi-color labeling.