Bright, far-red fluorescent water-soluble dye ideally suited for the 633nm or 647nm laser line. A significant advantage of using long wavelength dyes over other fluorophores is the low autofluorescence of biological specimens in this region of the spectrum. Reactive dye for the labeling of amino-groups in peptides, proteins and oligonucleotides, commonly used for imaging, flow cytometry and genomic applications. It is also the basis for the classic lipophilic tracer DiD and its variants. Suitable for use in applications such as fluorescence resonance energy transfer (FRET), time resolved- fluorescence resonance energy transfer (TR-FRET) and fluorescence polarization (FP). Spectral data: lambdaex 649nm| lambdaem 666nm.