Figure 1.

The principle of FRAP. FRAP experiments have been used to analyze the mobility of proteins in the nuclei of living cells. Color-coded fluorescence intensity in the nuclei of two living cells expressing the pre-mRNA splicing factor SF2/ASF fused to GFP is shown. The red peaks represent nuclear speckles, where GFP-SF2/ASF is concentrated in vivo. The blue 'holes' in the cell background represent the bleached area. The recovery of fluorescence as a consequence of protein mobility is followed over time. Images courtesy of Tom Misteli.