Cationic Liposome-Microtubule Complexes: Lipid-Protein Bio-Nanotubes with Open or Closed Ends

In this work we explored the structured that form when cationic liposomes are mixed with microtubules (MTs). Using synchrotron small angle X-ray diffraction (SAXRD) and transmission electron microscopy (TEM), we find two novel structures(1). For soft and intermediate rigid membranes we find that the cationic liposomes spread and coat the MTs and the external lipid layer is decorated by tubulin oligomers, forming a novel lipid-protein nanotube (LPN). By controlling the cationic lipid/tubulin stoichiometry, RCL/T, of the complex the LPN can switch between a state with open ends (Sketch 1A) to a state with closed ends with lipid caps (Sketch 1B). This form the basis for controlled drug encapsulation and release.