Conformational changes in complex macromolecules studied by single donor–acceptor pair fluorescence
Abstract
A single donor–acceptor (D–A) pair with a fluctuating FRET rate F is studied theoretically in the frame of a “two-state model” in which the FRET rate F fluctuates taking two values, F1 and F2, with average rates B for the forward and b for the backward transitions. Theoretical expressions are derived for the autocorrelation function g(2)DA(τ) and for the Mandel parameter QD,A(τ) allowing for background emission. Fluctuating intensities ID,A(t) and FRET efficiency E(t) = IA(t)/[IA(t) + ID(t)] are calculated with the help of the Monte Carlo technique. The probability wD,AN(T) of finding N