Figure 3.
Short-term viscoelastic deformation of the membrane tube as a function of pulling force. (A) Crossover length Lcross for bulk and cortex liposomes as the pulling force is increased in steps. Blue and red curves correspond to bulk and cortex liposomes, respectively. The radius of the bulk and the cortex liposomes is R0 = 10 ± 0.5 μm. (B) Lcross for several liposomes as a function of Fh – F0, where F0 is the tube initiation force. (Inset) All data together. Linear regression demonstrates a mean slope for bulk and cortex liposomes proportional to the inverse of an effective bending modulus k (see text). (C) Histogram of k = f/Lcross for all data points, giving k = (4.4 ± 0.4) × 10−8 N/m (mean ± SE) for bulk and k = (38 ± 6) × 10−8 N/m (mean ± SE) for cortex liposomes; p < 10−14. (D) Critical extrusion force F0 for bulk and cortex liposomes obtained by both direct (∗p < 0.1) and extrapolation approaches (∗∗p < 0.5).