CF® Dye Amines can be used to conjugate CF® dyes to carboxylic acids groups in biological molecules. Carboxylic acids can be activated using water soluble carbodiimides to react with amine-functionalized dyes to form a stable amide bond. CF® dyes are Biotium's line of next-generation fluorescent dyes with advantages in brightness, photostability, and conjugate specificity compared to other fluorescent dyes. Far-red fluorescent CF®640R dye has excitation/emission at 642/662 nm.