Figure 2.

(Top) A schematic illustration of the process of CG docking and fusion and (bottom) the corresponding fluorescent time traces of a CG docking and fusion event on an s-PSM. The event starts with a DiD-C₁₈-labeled CG docked to an Atto488-DPPE-doped PSM (i). At this stage, the CG appears red. Upon fusion, DiD-C₁₈ diffuses out of the CG membrane into the PSM and is quenched, while Atto488-DPPE simultaneously diffuses into the CG membrane and is dequenched (ii and iii). At this stage, the CG appears green and remains in a three-dimensional structure, which might be attributed to a hemifusion state or a transient opening and closing fusion pore. However, from the pure lipid labeling, it cannot be distinguished between hemifusion and fusion pore formation (see “?” in ii and iii, top). The subsequent decrease in the green fluorescence intensity is caused by a collapse of the three-dimensional CG post-lipid-mixing structure into the planar PSM (iv and v). To see this figure in color, go online.