FIG 7.
SPIM-FCCS data analysis showing codiffusion and DNA binding of Fos homodimers. (A) ACFs and CCFs from SPIM-FCCS measurements. Green, EGFP ACF; red, mRFP1 ACF. Solid lines indicate the experimental data, whereas dashed lines are fits assuming two diffusing components (ACF curves) or one component (CCFs). The red horizontal line is the cross talk-corrected red ACF amplitude, and the blue horizontal line is the level of cross-correlation due to cross talk. Cross-correlation above this value is due to the codiffusion of green and red molecules. (B) The first two columns are fluorescence intensity maps of EGFP or mRFP1 from a selected cell. The third column is a map of the fraction of GR dimers among all of the molecules detected [cGR/(cG-only + cR-only + cGR)], determined from the fits, and the histograms show their distributions. (C and D) Average fractions of GR dimers (C) and diffusion coefficients, Dcross (D), from the cross-correlation fits (mean ± SD; n > 20 for each sample). Fits were carried out on a pixel-by-pixel basis, and the median of the respective parameter from each cell was then averaged. ***, P < 0.0001 (t test).