Regiodependent Luminescence Quenching of BiotinylatedN-Sulfonyl-acridinium-9-carboxamides by Avidin

[reaction: see text] Biotin was conjugated to chemiluminescent N-sulfonylacridinium-9-carboxamides at the N-10 or 9-position carboxamide. Upon binding to avidin, the light output of the N-10 derivative (8) was quenched up to 92% upon triggering with basic peroxide, while the 9-position carboxamide conjugate (9) was quenched only 33%. The utility of this effect was demonstrated in a model homogeneous chemiluminescence assay.