Influence of end-to-end diffusion on intramolecular energy transfer as observed by frequency-domain fluorometry

We investigated the influence of end-to-end diffusion on intramolecular energy transfer between a naphthalene donor and dansyl acceptor linked by polymethylene chain. A range of viscosities from 0.6 to 200 cP were obtained using propylene glycol at different temperatures (0-80 degrees C) and methanol at 20 degrees C. The intensity decays of naphthalene were measured in the frequency domain. Several theoretical models, including distance distributions, were used to fit the data. The results indicate that end-to-end diffusion of flexible donor-acceptor pairs can be detected and quantified using frequency-domain fluorometry, even in the presence of a distribution of donor-to-acceptor distances.