A new bioorthogonal cross-linker with alkyne and hydrazide end groups for chemoselective ligation. Application to antibody labelling

We describe here the synthesis of the first bioorthogonal cross-linking reagent based on aminocaproic acid core with a hydrazide function at one end to react with glycoproteins and an alkyne group at the other end for Cu(I)-catalyzed click chemistry to azide-derivatized probes. As an application, this cross-linker was used to orthogonally conjugate profluorescent 3-azido-7-hydroxycoumarin to immunoglobulin G (IgG). An immunoassay showed that IgG was mostly not affected by the Cu(I)-catalyzed click chemistry conditions. Successful conjugations and retained immunoreactivity demonstrate the potential of this new bioorthogonal cross-linker in chemoselective ligation.