DEPENDENCE OF THE KINETICS OF SINGLET-SINGLET ENERGY TRANSFER ON SPECTRAL OVERLAP
Abstract
The energy donor was an N-methylindole moiety, and the acceptor was a ketone. These chromophores were fused to a rigid steroid that separated them by 10.2 à . Rate constants for singlet-singlet energy transfer in this system were obtained by nanosecond flash spectroscopy. J was varied over a 40-fold range simply by altering the solvent. We found that the transfer rate is proportional to J, as predicted by Förster's theory. The results bear on the potential use of this energy transfer process to measure distances in biological macromolecules. It is evident that the length of such a spectroscopic ruler can readily be controlled by varying the magnitude of the spectral overlap integral of the energy donor-acceptor pair.