A fluorometric method for determining the degree of biotinylation of proteins.

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 streptavidin/avidin are detected. The assay is simple and sensitive, requiring only 1-10 micrograms of biotinylated protein per determination.