Figure 10.
Dependence of the maximum likelihood parameters on the relaxation rate and the acceptor dark state population (pd). Parameters were obtained from the simulated photon trajectories using various models: 2-state (blue), 4-state (green), 2-state/Ds (orange), 4-state/Ds (purple), and 2-state/Dbs (black). Photon trajectories were simulated with the four-state model for 35 combinations of k/n (0.02 – 0.6) and pd = (0.02, 0.05, 0.1, 0.15, and 0.2). EF = 0.85, EU = 0.55, pF = 0.5, and τD/τD0 = 0.2 (folded) and 0.75 (unfolded). These input parameters are shown by grey horizontal dashed lines. For each combination, 5 sets of 100 of 30 ms-long trajectories were simulated with a total (donor and acceptor) photon count rate n = 50 ms−1. The relaxation rate k is normalized to the input value of the simulation (ksim). Errors are standard deviations of the 5 data sets and error bars smaller than the symbol are not shown. Vertical dashed lines indicate k/n of three proteins: α3D (blue), gpW (green), and WW domain (red). The acceptor dark state population (pd) of the three proteins are 0.023, 0.060, and 0.12, respectively. The green horizontal dashed lines in the donor lifetime plots indicate acceptor blinking averaged values calculated as (τDF(U)pb(1 - EF(U)) + τD0pd(1 - Ed))/(1 – pbEF(U) – pdEd).