Extended Data Figure 5: FRET efficiency histograms of α3D at various solvent viscosities.
From: Single-molecule fluorescence probes dynamics of barrier crossing
The FRET efficiency histograms were constructed from 1-ms bins in the trajectories with the mean photon count rate >50 ms−1 for 2.25 M and 3.2 M GdmCl and from 2-ms bins in the trajectories with the mean photon count rate >30 ms−1 for 4.6 M, 4.3 M and 3.8 M GdmCl concentrations. At the relative viscosity (η/η0) 1, 10 and 38, the higher concentration of GdmCl was used to counteract the stabilization of proteins by glycerol to maintain the ratio of folded to unfolded molecules as close to unity as practically possible. The similar ratio of the integral of the folded (high FRET) and the unfolded (low FRET) distributions indicates that the equilibrium constant is unchanged at these conditions, as shown more precisely in the maximum likelihood analysis.
