RESUMO
Click reactions are used for chemoselective functionalization in many research fields. Despite the utility of small, bioinert azide groups as a counterpart, applications of strain-promoted alkyne-azide cycloaddition (SPAAC) reactions for this purpose are still limited by slow reaction kinetics. Here, we report ion-pair-guided reaction rate enhancement by the use of water-soluble cyclooctadiynes (WS-CODYs) composed of bifunctional strained alkynes and polar side chains. Arrhenius plot analysis revealed that the rate enhancement by WS-CODYs is due to a kinetic salt effect between the polar substituents and the target azide. We demonstrate the utility of these compounds for rapid protein labelling and isoelectric point-dependent labelling.
RESUMO
Bio-orthogonal ligations that crosslink living cells with a substrate or other cells require high stability and rapid kinetics to maintain the nature of target cells. In this study, we report water-soluble cyclooctadiyne (WS-CODY) derivatives that undergo an ion-pair enhanced double-click reaction. The cationic side chain of WS-CODY accelerated the kinetics on the azide-modified cell surface due to proximity effect. Cationic WS-CODY was able to crosslink azide-modified, poorly adherent human lung cancer PC-9 cells not only to azide-grafted glass substrates but also to other cells within 5-30 min. We discovered that cell-substrate crosslinking induced the ITGA5 gene expression, whereas cell-cell crosslinking induced the CTNNA1 gene, according to the adhesion partner. Ion-pair-enhanced WS-CODY can be applied to a wide range of cells with established azide modifications and is expected to provide a powerful tool to regulate cell-substrate and cell-cell interactions.
