mFluor™ Blue 659 SE is a succinimidyl ester derivative of mFluor™ Blue 659, a water-soluble fluorescent dye designed for blue laser excitation and red fluorescence emission. The dye is optimally excited with a 488 nm blue laser and emits at approximately 659 nm, providing a large Stokes shift that distinguishes it from many conventional blue laser-excited fluorophores. This spectral profile makes mFluor™ Blue 659 useful for flow cytometry, particularly in spectral flow cytometry workflows where distinct emission patterns can help expand panel design options.

The succinimidyl ester reactive group enables covalent labeling of primary amines, including lysine residues on proteins or antibodies and amine-modified biomolecules. At pH 7–9, the SE group reacts efficiently with primary amines to form stable amide bonds, supporting preparation of fluorescent protein, antibody, oligonucleotide, and surface conjugates. Compared with R-phycoerythrin, mFluor™ Blue 659 dye conjugates are described as more photostable, supporting their use in fluorescence imaging workflows. mFluor™ Blue 659 SE is suitable for preparing fluorescent conjugates for flow cytometry, spectral flow cytometry, fluorescence imaging, and other fluorescence-based detection applications.