Acrylamide quenching of Yt-base fluorescence in aqueous solution

Acrylamide was found to be an effective quencher of Yt-base (Y-4,9-dihydro-4,6-dimethyl-9-oxo-1H-imidazo-1,2a-purine) in water. In the absence of collisional quenching the decay of Yt-base in water is predominantly a single exponential. The intensity decays become increasingly heterogeneous when quenched by acrylamide. The frequency-domain data were analyzed using the radiation model, which provides estimates of molecular parameters characteristic of the system. The mutual diffusion coefficient at 20 degrees C was found to be 0.5 x 10(5) cm2/s, the Yt-base acrylamide interaction radius was 8 A, and the rate constant for quenching was 100 cm/s. These values indicate that quenching is diffusion-limited, i.e., the encounter complex is deactivated at least 2-fold faster than the rate of diffusive encounters.