Fig. 4. YFP-Kv2.1HA exhibits limited mobility after photobleach. (A) Images from a FRAP time series in a YFP-Kv2.1HA-expressing HEK cell. The region highlighted by the white box was bleached and recovery in that region was followed by scanning every 15 seconds for 20 minutes (see Materials and Methods). The inset shows enlargement of the bleach region and shows that recovery of YFP fluorescence does not occur via lateral diffusion of YFP-Kv2.1 from adjacent nonbleached membrane. (B) Average recovery after photobleach for YFP-Kv2.1HA. Fluorescence at each time point after bleach (bleach=time 0) was normalized to the prebleach intensity and averaged for all cells (n=25). The solid line through the data is a two-exponential fit to the average data (see Materials and Methods). Fit parameters: ₁=36.1 seconds, A₁=0.13; ₂=308 seconds, A₂=0.24, M_f=0.41±0.04. Bar, 10 µm.