Exploiting Long-Lived Molecular Fluorescence

Fluorophores based on the azo chromophore 2,3-diazabicyclo[2.2.2]oct-2-ene, referred to as fluorazophores, display an exceedingly long fluorescence lifetime. Besides the use in time-resolved screening assays, where the long-lived fluorescence can be time-gated, thereby improving the signal to background ratio, a distinct application of fluorazophores lies in the area of biopolymer dynamics. For this purpose, one chain end is labeled with a fluorazophore and the other one with an efficient fluorescence quencher. The fluorescence lifetime of the probe/quencher-labeled peptide then reflects the kinetics of intramolecular end-to-end collision. Applications to polypeptides are described and control experiments which establish the nature of the quenching mechanism as a diffusive process requiring intimate probe/quencher contact are described