This amine-reactive reagent can be used to create blue-fluorescent bioconjugates with excitation/emission maxima ~410/455 nm that are excitable by the 405 nm spectral line of the blue diode (violet) laser. Used in highly sensitive analyses of amines, amino acids and dipeptides. Amine-reactive reagents react with non-protonated aliphatic amine groups, including the amine terminus of proteins and the є-amino group of lysines.