Fluorescence Dye 620-M with Streptavidin conjugate. All the Fluorescent Dye M series products are designed to be maximally excited by one of the major light sources equipped in flow cytometers. Besides, in comparison with phycobiliprotein tandems, Fluorescent Dye M series possesses better photostability, higher conjugation yields, and little pH sensitivity making it an ideal choice in fluorescence imaging applications.