Figure 3.

Illustration of the FRAP experiment performed on fused pairs of membrane-coated silica spheres. Scale bar, 5 μm. (A) Confocal laser scanning micrograph of two silica spheres with fused membranes. A region of interest (black circle) is chosen to cover one of the two spheres. Another region on a distant sphere (black circle, dashed line) is chosen as a reference to account for general photobleaching. (B) Region of interest is bleached with a high-intensity laser pulse. (C) Recovery of fluorescence intensity recorded in bleaching region. Fusion of membranes is clearly visible due to loss in fluorescence intensity of the second, unbleached sphere. Homogeneous fluorescence intensity before and after bleaching indicates full fusion. (D) Sketch of the experiment. One sphere of the fused pair is bleached; the fluorescence recovery is observed within the bleached area. The contact angle α is introduced as the angle between the x axis connecting sphere centers and a line connecting a sphere center and the point of delamination of the membrane from the sphere. All fluorescence micrographs are in gray scale and inverted colors. To see this figure in color, go online.