||Biotin (Vitamin H) is an important biomolecule that has been widely used in Biotinylation reactions to label antibodies or other proteins of interest. Due to its low molecular weight, biotin usually does not cause any significant changes in protein conformation and biological activity. Biotinylated proteins/antibodies are widely isolated and assayed with streptavidin pull-down assay, affinity chromatography, ELISA and Western blotting etc. offers a variety of ready-to-use Biotinylation reagents (Cat. # 2346, 2345, 2347, 2322, 2326, 2323). It is often desired to determine the degree of substitution of such biotinylated biomolecules. Biotin Assay Kit is based on the differential binding of Streptavidin to Biotin and a dye, 2-(4-hydroxyazobenzene) benzoic acid (HABA). When HABA is bound to Streptavidin, addition of free biotin or biotinylated biomolecules results in its displacement in the reaction. These changes are manifested in terms of decrease in the overall absorption (OD 500 nm) and can be quantitatively correlated to the amount of biotin present in solution. The kit also provides Biotin as a Standard and Biotinylated BSA as a positive control. This kit can be used to estimate as low as 60 pmol or 15 ng of biotin in solution.