N-(Azido-PEG4)-biocytin is widely used in bioconjugation and labeling applications due to its unique properties. The azide group enables click chemistry reactions, particularly with alkyne-containing molecules, making it valuable for attaching biotin to various biomolecules. This compound is extensively utilized in proteomics and cellular studies for labeling proteins, peptides, or other biomolecules with biotin, which can then be detected or isolated using streptavidin-based systems. Its PEG4 spacer enhances solubility and reduces steric hindrance, improving binding efficiency. Researchers often employ it in fluorescence microscopy, pull-down assays, and affinity purification to study protein interactions, localization, and dynamics. Additionally, it serves as a versatile tool in drug delivery systems and diagnostic applications, where precise biotinylation is required.