DBCO-PEG4-Butyraldehyde is a click chemistry PEG reagent containing a terminal butylraldehyde group. Butyraldehyde reacts with hydrazide to form a stable hydrazone linkage or with alkoxyamines to form a stable oxime bond. The hydrophilic PEG spacer arm improves water solubility and provides a long and flexible connection that minimizes steric hindrance involved with ligation. DBCO is commonly used for copper-free Click Chemistry reactions. Reagent grade, for research use only.