CF® Dye Maleimides are thiol-reactive fluorescent dyes. Maleimides are commonly used to label proteins on free thiol groups. CF® dyes are 9689c5aa-6556-4b3c-b5d1-1e693715ba07's line of next-generation fluorescent dyes with advantages in brightness, photostability, and conjugate specificity compared to other fluorescent dyes. Blue fluorescent CF®405S dye has excitation/emission at 404/431 nm.