A variety of cyanine 5 ( Cy5) dyes has been used to label biological molecules for fluorescence imaging and other fluorescence-based biochemical analysis. They are widely used for labeling peptides, proteins and oligos etc.  Cy5 dyes are one type of the most common red fluorophores. These versatile fluorophores can tolerate a pH range of 3-10 for use in a variety of applications at biologically relevant pHs. The dyes are also DMSO tolerant and photostable to enable transfer from storage to assay without loss of performance. The aqueous solubility eliminates the need for organic solvents in the assay buffers. Our Cy5 Fluors are thoroughly QC tested to ensure high levels of chromophore and reactive dye content. Mono-reactive dyes are suitable for targeted, precise labeling of proteins and oligonucleotides and bis-reactive dyes are more suitable for general labeling. NHS ester dyes are recommended for labeling amine groups and maleimide dyes are recommended for labeling thiol groups. This Cy5 amine reacts with carbonyl groups. Cy5 is the trademark of GE Healthcare.