Dynamics of Forster Energy Migration Across Polymer Chains in Solution

Long distance excitation energy transfer between a donor and an acceptor embedded in a polymer chain is usually assumed to occur via the Forster mechanism which predicts a R distance dependence of the transfer rate, where R is the distance between the donor and the acceptor. In solution R fluctuates with time. In this work, a Brownian dynamics simulation of a polymer chain with Forster energy transfer between the two ends is carried out and the time dependence of the survival probability SP (t) is obtained. The latter can be measured by fluorescence resonance energy transfer (FRET) technique which is now widely used to study conformations of biopolymers via single molecule spectroscopy. It is found that the survival probability is exponential-like when the Forster radius (RF ) is comparable to the root mean square radius (L) of the polymer chain. The decay is strongly non-exponential both for small and large RF , and also for large kF . Large deviations from the Wilemski-Fixman theory is obtained when RF is significantly different from L.