Förster Resonance Energy Transfer between Fluorescent Proteins: Efficient Transition Charge-Based Study

Abstract

Toward a better understanding of the Forster resonance energy transfer (FRET) utilized in genetically encoded biosensors we theoretically examined the excitonic coupling between cyan fluorescent protein (CFP) and yellow FP (YFP) with time-dependent density functional theory (TD-DFT). Going beyond the dipole–dipole (dd) approximation in the original Forster theory, we adopted a transition charge from the electrostatic potential (TrESP) method that approximates the excitonic coupling as classical Coulomb interaction between the transition charges derived from the transition density for each FP fluorophore. From the TD-DFT calculations with embedded point charges for the trajectory generated by classical molecular dynamics (MD) simulations we found that the thermal fluctuation of the fluorophore geometry in FP and the protein electrostatic interactions do not significantly affect the Coulomb interaction between the FP pairs. The TrESP calculations utilizing the Poisson equation indicate that the screening an...