ReadiLeave™ Reversible (RLR) Biotin is a newly developed biotin derivative that has significantly reduced affinity to avidin (including streptavidin) to make the binding of RLR biotin and streptavidin readily reversible when needed. It is complimentary to the regular biotin and has a moderate affinity to streptavidin to ensure a tight binding but not too tight to be reversed in contrast with the regular non-reversible biotin. ReadiLeave™ Reversible Biotin Azide is an excellent building block to develop reversible biotin probes and products for biological detections and purification using the well-known click reactions (CuAAC). It readily reacts with an alkyne-modified biomolecule under mild conditions. The affinity between streptavidin and biotin might be the strongest non-covalent interactions known in biological interactions. Streptavidin, a homotetrameric protein, exhibits an extraordinarily high affinity for biotin. Each streptavidin monomer can bind one biotin molecule, allowing a streptavidin protein to maximally bind four biotins. The streptavidin-biotin interaction is highly specific and remains robust under a wide range of conditions. Biotin can readily be attached to proteins, nucleic acids, or even nanoparticles. Once formed, the bond between biotin and streptavidin is unaffected by extremes of pH, temperature, organic solvents, and other denaturing agents. This powerful interaction has been exploited for various applications such as ELISA, Western blotting, Northern blotting, Southern blotting, immunohistochemistry (IHC), cell surface labeling, Fluorescence-Activated Cell Sorting (FACS), and electrophoretic Mobility Shift Assays (EMSA) etc.