Fig. 6: Experimental test of FRET correlation functions.

a Scheme of the Holliday junction labeled with donor (D) and acceptor (A) switching between low and high FRET efficiency states (top). Experimental FRET efficiency histograms (measured with PIE)⁴⁸ at different concentrations (indicated) of MgCl₂ (bottom). The number of bursts (n) is indicated in the histograms. b Correlation ratios (indicated) at 0.1 mM MgCl₂. c FRET correlation functions (color as in a) together with the global fit to a sum of two exponentials with an offset (black lines). The MgCl₂ concentrations are indicated. d Comparison of the kinetic rates of the fast decay (dashed line) and the slow decay (red circles) with the total rate obtained from a previously published H²MM analysis (gray circles). Error bars represent the error from the fit. e FRET efficiency histograms of U2AF2 in apo- and holo-state. The number of bursts (n) is indicated. f Filtered FCS autocorrelation functions (ACF) and cross-correlation function (CCF) for apo (blue) and holo (red) state together with a fit containing two exponential decays and a diffusion component. The timescale of diffusion is indicated as gray shaded area. g FRET correlation functions for the data in (e, f). The black line is a fit with three exponential decays. Light colors in the FRET correlation functions in (b, f, g) are the data with a lag time binning of 1 \({\rm{\mu}}\)s and dark colors are for a 10 \({\rm{\mu}}\)s binning.