FCCS measurements on HeLa cells expressing RpL26-eGFP and NCp7-mCherry.

<p>The green, red and black curves denote the autocorrelation curve of RpL26-eGFP in the green channel, the autocorrelation curve of NCp7-mCherry in the red channel, and the cross-correlation curve between the two channels, respectively. As a negative control, the blue curve corresponds to the cross-correlation between eGFP and mCherry proteins co-expressed in HeLa cells. The close to zero value of the FCCS curve of the negative control not only shows that the two fluorescent proteins do not diffuse together, but also that there is marginal spectral bleed-through between the green and red channels. The solid lines correspond to the fit of the curves to the anomalous 3 D diffusion model. Diffusion constants of 5.6 (+/- 0.7) μm²/s, 6 (+/- 3) μm²/s and 4 (+/- 3) μm²/s were obtained for RpL26-eGFP (green), NCp7-mCherry (red) and the RPL26-eGFP/NCp7-mCherry complex (black), respectively.