Fig. 2.
Tube formation in Sp vesicles. (A–C) Overlay of top-view confocal sections and bright field images of a vesicle (A) before deflation, (B) during phase separation, and (C) after 2.6 h of equilibration. The arrowheads in B and C indicate fluorescence from tubes in the focal plane. The droplets visible in B contain the newly formed dextran-rich phase. In C, the inner dark circle represents the contour of the dextran-rich phase, which is in focus. The out-of-focus outer dark circle is the contour of the PEG-rich phase above the dextran-rich phase. The fluorescent signal shows the membrane crossing the focal plane. (D) Confocal xy section of another vesicle showing possible three-way tube junctions indicated by arrows as in F. For C and D, the osmolarity ratio r = 1.24. (E) Vertical xz section showing adsorption of tubes onto the two-phase interface. (F) Horizontal xy section at the z position of the arrowhead in E showing tubes at the two-phase interface. (G) Vertical xz section of a vesicle with overcrowded two-phase interface; the tubes protrude into the upper PEG-rich phase. (H) 3D projection from a stack of xy sections at the two-phase interface delimited by the rectangle in G. (I) Confocal xy section of the tubes slightly above the two-phase interface. For E–I, r = 1.5. Scale bars, 15 μm.