Fluorescence recovery after photobleaching in membraneless organelles. At time tPB, a region of interest (ROI) of the condensate is exposed to a high intensity beam that photo-bleaches all the fluorescent molecules within this area; the rapid exchange of molecules within the dense phase and between the dense and the light phase contributes to the fluorescence recovery after photobleaching. The amplitude and characteristic time of the recovery provide information on the transport properties of the condensate. However, the quantitative interpretation of FRAP data requires a careful testing of the adopted model, including contributions due to 1) the ratio between the photobleached volume/overall volume of the droplet, 2) the shape of the excitation and detection beam, 3) assumptions on fixed or infinite boundaries, and 4) diffusion- or reaction-dominated interactions between the molecules (4). To see this figure in color, go online.
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