Changes in liposome morphology induced by actin polymerization in submicrometer liposomes

A morphological change in actin-containing liposomes produced via extrusion across a 400 nm pore diameter polycarbonate membrane in low ionic strength buffer (G-buffer) is induced by the addition of high ionic strength buffer (F-buffer). The change in conformation is due to the polymerization of monomeric G-actin within the inner compartment of the liposome and the subsequent deformation of the initially spherical liposome into a disklike geometry. This result was elucidated by applying various form factors corresponding to different geometries to light scattering data derived from actin-containing liposome dispersions. The results of this analysis showed that empty (no actin) liposomes in G-buffer and F-buffer, as well as actin-containing liposomes in G-buffer, were all spherelike objects between 250 and 450 nm in diameter, depending on osmotic conditions. The findings further showed that the actin-containing liposomes in F-buffer took on a thin, disklike shape, a result of the internal polymerization of the actin monomers into filaments.