Figure 2.

RIBEYE-binding peptide fluorescent puncta mark the location of synaptic ribbons in living mouse bipolar cells. A, Ribbon positions (arrows) in a live synaptic terminal revealed by fluorescein-Rpep labeling in a single confocal optical section. The inset shows a projection of a series of z-axis sections through the entire terminal to illustrate the positions of ribbons in other focal planes, which contribute some of the dimmer Rpep fluorescence in the single-section in the main panel. B, The same terminal fixed and photographed by EM. Arrows indicate ribbons, and the inset shows a magnified view of the ribbon marked by a rectangle. C, Top panel shows a single confocal section with labeled synaptic ribbons. Box 1 contains a labeled synaptic ribbon that appears elongated. The synaptic ribbon in the corresponding EM section (C1) also has an elongated, plate-like structure. Box 2 in the top panel contains a broad fluorescent spot, perhaps indicating the presence of two side-by-side synaptic ribbons. Indeed, the corresponding EM image (C2) shows two adjacent synaptic ribbons.