EZ-Link Maleimide-PEG4-DBCO is a sulfhydryl-reactive hetero-bifunctional crosslinker that contains a dibenzylcyclooctyne (DBCO) group for copper-free click chemistry applications. The thiol/sulfhdryl-reactive maleimide can be used to label a variety of thiol-containing moieties such as free cystines in proteins, peptides, or other (bio)molecules. Once a protein or (bio)molecule is DBCO-labeled, it can undergo a copper-free azide-alkyne cycloaddition reaction to form a stable triazole linkage with an azide-labeled coupling partner.

EZ-Link Maleimide-PEG4-DBCO features include:
• Bioorthogonal—DBCO and azides react selectively to form triazole linkages
• Thiol reactive—reacts with sulfhydryls (-SH), such as the side chain of cysteine (C)
• Heterobifunctional—reactive towards sulfhydryls and azides
• Soluble—reagent readily dissolves in water-miscible solvents for dilution into aqueous reaction mixtures

EZ-Link Maleimide-PEG4-DBCO can be used to create diverse conjugates by means of the bioorthogonal coupling between an alkyne and azide (supplied separately). The coupling or crosslinking procedure is typically done in two steps. First, a protein- or thiol-containing molecule is labeled with a DBCO group and excess crosslinker is removed. Second, an azide-containing moiety (prepared independently) is introduced into the same system as the DBCO moiety and labeling occurs under biological conditions without the introduction of any additional reagents such as a copper catalyst.

Classic click reactions involve a copper-catalyzed azide-alkyne cyclo­addition to label or conjugate molecules. A drawback of this approach is that copper ions can impair protein function, harm cells, and reduce the fluorescence of fluorophores. DBCO is distinct in that it doesn’t require copper to catalyze the reaction with an azide for triazole formation. The strain in the eight-membered ring allows the reaction with azide-modified molecules to occur in the absence of catalysts, preventing copper-induced damage to cells or proteins.