Fig. 2.
Mean transfer efficiencies from single-molecule measurements (filled red circles) and ensemble time-correlated single-photon measurements (open red circles) as a function of the contour lengths of the peptides (Gly-Pron-Cys) assuming the geometry of polyproline found in the crystal structure (28) in comparison to the dependences calculated for a rod-like spacer assuming isotropic averaging (solid curve) or a random, but static angular distribution of the dipoles of donor and acceptor (dashed curve) (A) and in comparison to the dependences calculated for the different dynamic regimes according to Eqs. 4 (dark-gray squares), 5 (black squares), and 6 (light-gray squares) using the normalized end-to-end distance distributions from the molecular dynamics simulations of the peptides (Fig. 3) (B). The corresponding lines are empirical fits of the data to the equation E = 1/[1 + (r/C)4], where C is the fit parameter. (Inset) The growing deviation of the transfer efficiency measured in the single-molecule experiment (Em) from the prediction of Eq. 1 (EF) as the peptide contour length is increased beyond R0.