Figure 4. Short membrane nanotubes coated with high density of I-BAR are semi-flexible with L_p ~L and do not move laterally on the GUV membrane.

(A) From top to bottom panel, (i) example of a tube fixed on the GUV membrane (ii) the corresponding maximum projection of the intensity of a series of images of the same tube (iii) the corresponding average intensity from the entire time series and (iv) line profile parallel to the GUV membrane at a distance corresponding to L/3 from the GUV membrane. (B–D) More examples of short tubes plotted in the same sequence as in (A). (E) Theoretical calculation of the probability of a fluctuating rod which is fixed at one end. Top image shows a rod which has L_p/L = 20, in the middle image L_p/L = 1.7 and in the bottom image L_p/L = 0.7. x and y axes range from 0 to L and –L to L, respectively. The graph below the images corresponds to line profiles along the depicted lines in the three images, L_p/L = 20 (blue), L_p/L = 1.7 (green) and L_p/L = 0.7 (red). All images in (A–D) present intensities from YFP labeled I-BAR. Membrane composition DOPC:DOPS:TR-DHPE 59.7:40:0.3. The figure shows representative examples of the (N_short > 100) short tubes observed in this work. All scale bars are 2 μm.