Molecular Tripods Showing Fluorescence Enhancement upon Binding to Streptavidin

We introduce a new approach to biotin−streptavidin assays based on a molecular tripod which consists of biotin, a fluorophore, and a quencher. The interaction between streptavidin and molecular tripods perturbs the ground-state quencher−fluorophore dimeric conformation in the absence of streptavidin and diminishes the intrinsic self-quenching of a quencher−fluorophore pair. The emission intensity of the molecular tripods plus streptavidin is 3.5−5.2 times that of molecular tripods in the absence of streptavidin.