Biotin-PEG2-azide *CAS 945633-30-7*

Biotin-PEG2-Azide *CAS 945633-30-7* is a non-cleavable, azide-activated biotinylation reagent designed for use in bioconjugation applications. It selectively reacts with terminal alkynes to form stable triazole linkages, either via copper-catalyzed click reactions or Cu-free click reactions with strained cyclooctynes (e.g., DBCO or BCN compounds). Additionally, it can react with phosphine-labeled molecules through Staudinger chemistry. These reactions are bioorthogonal, meaning they do not interfere with biological systems. The inclusion of a hydrophilic PEG2 spacer in Biotin-PEG2-Azide enhances its aqueous solubility and reduces steric hindrance, particularly when binding to avidin molecules. This reagent is particularly useful for detecting cellular alkyne cholesterol analogs and for preparing multifunctional benzophenone linkers used in pull-down assays, photoaffinity labeling, and double-click stapling techniques.