Used in bioconjugation to link biotin to proteins, peptides, or other amine-containing molecules via stable amide bonds. The PEG3 spacer enhances solubility and reduces steric hindrance, improving binding efficiency to streptavidin or avidin systems. Commonly applied in immunoassays, flow cytometry, and protein labeling for detection and purification. Suitable for surface modification in biosensors and diagnostic platforms due to its reliable coupling and low non-specific binding.