Sulfo-Cyanine 5-PEG3-Biotin

Sulfo-Cyanine 5 is a far-red fluorophore widely used for biomolecule labeling, with excitation maximum at 646 nm and emission maximum at 662 nm. Far-red fluorescent tags with excitation above 600 nm and emission further than 650 nm are valuable for imaging techniques because of the lower background autofluorescence at these wavelengths. Besides, far-red fluorescent labels can be imaged simultaneously with near-red, orange, green, and blue tags, which is advantageous for multicolor imaging. Biotin, or the water-soluble vitamin H, is well known not only for playing essential roles in various crucial metabolic cellular reactions but also for its extremely high affinity for avidin, a glycoprotein of egg white. Avidin, streptavidin (bacterial analogue of avidin), and neutravidin (deglycosylated avidin) bind non-cooperatively to biotin with high affinity. Thus, sulfo-Cyanine 5 biotin conjugate can be used for detecting and quantifying biotin binding sites of avidin, streptavidin, and neutravidin in samples of different origin. Sulfo-Cyanine 5 biotin conjugate is a water-soluble reagent and its fluorescence is pH independent from pH 4 to pH 10. A flexible PEG3 linker between biotin moiety and fluorescent tag provides binding to avidin, streptavidin, or neutravidin without steric troubles. The major applications of sulfo-Cyanine 5 biotin conjugate include imaging (e.g. primary and secondary antibody labeling for Western Blotting, immunoassay, cyto- and histochemistry, flow cytometry), affinity and dissociation constant measuring, streptavidin-based sensors, etc.