5-(4,6-dichlorotriazinyl)aminofluorescein (5-DTAF) is a reactive dye with absorption/emission maxima of ∼492/516 nm. Dichlorotriazines readily modify amines in proteins, and are among the few reactive groups that are reported to react directly with polysaccharides and other alcohols in aqueous solution, provided that the pH is >9 and that other nucleophiles are absent.