Azido-dPEG®₄-acid

Azido-dPEG®4-acid, product number QBD-10502, is a click chemistry crosslinking reagent. The azide moiety on one end of the molecule is useful for copper(I)- or ruthenium-catalyzed click chemistry or copper-free click chemistry. Between the azide moiety and the propanoic acid moiety on the other end of the molecule is a single molecular weight, discrete polyethylene glycol (dPEG®) spacer. The propanoic acid moiety can be coupled to a primary or secondary amine by an acylation reaction. The azide also functions as a masked amine. In this application, the carboxylic acid end reacts first with an amine to form a peptide bond, followed by reduction of the azide to an amine for further reaction.

Activation of the propanoic acid moiety with an acylating agent enables conjugation of azido-dPEG®4-acid to a primary or secondary amine. Popular acylating agents include such as N-hydroxysuccinimide (NHS); 2,3,5,6-tetrafluorophenol (TFP); or 2,3,4,5,6-pentafluorophenol (PFP). Alternatively, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) or another suitable carbodiimide can be used to couple the acid moiety directly to an amine without prior activation.