Fluorescein biotin, 5-((N-(5-(N-(6-(biotinoyl)amino)hexanoyl)amino)pentyl)thioureidyl)fluorescein

Fluorescein biotin was developed as an alternative to radioactive biotin for detecting and quantitating biotin-binding sites by either fluorescence or absorbance. Upon binding to avidin or streptavidin, the fluorescence or absorbance of this molecule is quenched.