Fig. 2.

Analysis of bleaching steps of single TβRII-GFP molecules imaged with the fixed HeLa cells. (A) A typical image shows the diffraction-limited fluorescent spots of TβRII-GFP on the fixed cell membrane. The spots enclosed with the green circles (3 × 3 pixels) were chosen for single molecule bleaching analysis. (Scale bar, 2 μm.) (B) Two representative time courses of GFP emission after background correction show one step bleaching. (C) Frequency of one-, two-, and three-step bleaching events (n = 262) revealed TβRII-GFP monomer. (D) Distribution of the fluorescence dwell time of individual fluorescent spots (n = 130). The decay time constant is 3.1 ± 0.6 s determined by the single exponential decay fitting function.