Cy3 biotin conjugate

This bifunctional Cy3 biotin conjugate demonstrates excellent avidin binding and strong fluorescence upon binding to a protein or nucleic acid target. It has avidin-binding properties similar to native biotin in terms of high affinity, fast association, and non-cooperative binding to avidin and streptavidin tetramers. Cy3 Biotin can be used for detecting and quantifying biotin binding sites of avidin, streptavidin or neutravidin. This reagent overcomes major shortcomings of commonly used Biotin-4-fluorescein, e.g., poor solubility in aqueous media and pH dependent absorbance and emission. Cy3 Biotin is a water-soluble reagent and its red fluorescence is pH independent from pH 4 to pH 10. A flexible PEG spacer between biotin moiety and fluorescent tag minimizes the steric hindrance involved in binding to avidin, streptavidin or neutravidin.