Figure 5.

Experimental and simulated decay times and amplitudes of the autocorrelations of donor intensity time traces at different fluorescent ATP concentrations. (a) Schematic representation of the four-state model used for the simulations. Each state has its own intensity, due to differences in FRET efficiency. One full cycle consists of two 8 nm steps and two nucleotide turnovers. Both steps/turnovers are built up of the same transitions, characterized by lifetimes T₁ and T₂. Only T₁ depends on the concentration of fluorescent ATP. (b) Average (mean ± SE) decay times obtained from exponential fits to the experimental (solid squares with error bars) and simulated autocorrelations of the donor fluorescence intensity (colored lines). For all simulations the v_max and K_m values obtained from the fit of Fig. 3b were used to determine T₁ and T₂. Shown are simulations calculated according to the four-state model shown in panel a, with intensities for the respective states as indicated. (c) Average (mean ± SE) amplitude obtained from exponential fits to the experimental (solid squares with error bars) and simulated autocorrelations of the donor fluorescence intensity (colored lines).