Utility and considerations of donor-donor energy migration as a fluorescence method for exploring protein structure-function.

This review aims at surveying the use of electronic energy transport between chemically identical fluorophores (i.e. donors) in studies of various protein systems. Applications of intra- and interprotein energy migration are presented that make use of polarised steady-state and time-resolved fluorescence spectroscopic techniques. The donor-donor energy migration (DDEM) and the partial donor-donor energy migration (PDDEM) models for calculating distances between donor groups are exposed together with the most recent development of an extended Forster theory (EFT). Synthetic fluorescence depolarisation data that mimic time-correlated single photon counting experiments were generated using the EFT, and then further re-analysed by the different models. The results obtained were compared with the known parameters used to generate EFT data. Aspects on how to adopt the EFT in the analyses of time-correlated single photon counting experiments are also presented, as well as future aspects on using energy migration for examining protein structure.