A fluorometric method for determining the degree of biotinylation of proteins

Abstract A method to determine the number of biotin moieties attached to a protein has been developed based on quenching the natural fluorescence of avidin or streptavidin by biotin. The assay consists of titrating the number of biotin combining sites on streptavidin/avidin before and after adding the biotinylated protein. With this method only those biotin moieties capable of binding to strptavidin.avidin are detected. The assay is simple and sensitive, requiring only 1–10 μg of biotinylated protein per determination.