Biotin Labeling Kit-SH is mainly used for the preparation of biotin-labeled IgG for enzyme immunoassay (EIA). SH reactive biotin, a component of this kit, reacts with sulfhydryl groups of proteins or other molecules (Fig.1). The kit contains all the reagents necessary for the labeling. The reducing agent included in this kit creates sulfhydryl groups in the IgG molecule. Because the reducing agent is a water-soluble phosphine compound, it can be removed by a filtration tube with a simple process. An average of 5 to 8 biotin molecules conjugate to each IgG molecule. The number of biotin molecules per protein can be determined by HABA assay. Excess biotin molecules can be removed by a filtration tube.
Fig. 1 IgG labeling reaction with SH-reactive biotin
♦ The molecular weight of the reduced protein to be labeled with this kit should be greater than 50,000.
♦ IgG or biotin-conjugated IgG is always on the membrane of the filtration tube during the labeling process.
♦ If the IgG solution contains other proteins with molecular weights larger than 10,000, such as BSA or gelatin, purify the IgG solution before labeling biotin with this kit. IgG solution can be purified by IgG Purification Kits (not included in this kit).
♦ If the IgG solution contains small insoluble materials, centrifuge the solution and use the supernatant for the labeling.