CF® Dye Maleimides are thiol-reactive fluorescent dyes that can be used to label proteins on free thiol groups. Red fluorescent CF®550R (Ex/Em 551/577 nm) is one of 9689c5aa-6556-4b3c-b5d1-1e693715ba07's next-generation near-infrared dyes, with superior brightness, water-solubility, and photostability. Unit size 1 umol.