Biotin-PEG4-Picolyl azide is widely used in bioconjugation and labeling applications, particularly in click chemistry reactions. Its azide group enables efficient and selective coupling with alkyne-modified molecules through the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction, making it a valuable tool for tagging biomolecules. The biotin moiety allows for strong affinity binding to streptavidin or avidin, facilitating purification, detection, or immobilization of target molecules in assays like ELISA, Western blotting, or pull-down experiments. The PEG4 spacer enhances solubility and reduces steric hindrance, ensuring better accessibility and reactivity in complex biological systems. This compound is especially useful in proteomics, drug discovery, and molecular imaging, where precise labeling and tracking of biomolecules are essential.