Hierarchical Bionanotubes Formed by the Self Assembly of Microtubules with Cationic Membranes or Polypeptides

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Original Entry by Holly McIlwee, AP225 Fall 09


Uri Raviv, Daniel J, Needleman, Kai Ewert, Cyrus R. Safinya, Hierarchical Bionanotubes Formed by the Self Assembly of Microtubules with Cationic Membranes or Polypeptides Journal of Applied Crystallography. 2007, 40, s83-s87.



Soft Matter

Needleman et al. describes a generally accepted perspective for lipid self-assembly leading to nanotubule formation in mixed changed systems. An interaction between negatively charged microtubules and positively charged lipid membranes, under appropriate conditions gives rise to spontaneously forming lipid protein nanotubules.

Following are examples of lipid-biopolymer interactions previosuly studied:

- The mixing of cationic lipids and DNA complexes are formed that bring genes into cells (Koltover, 1998)

- Polyelectrolyte lipid complexes:

  - Pinched multilamellar PLCs from PGA complexed with cationic membranes (Subramanian, 2000)
  - Flat, thermally functioning, multilamellar PLCs from lambda DNA complexed with cationic     
    membranes (Radler, 1997)
  - Swollen multilamllar PLCs from filamentous actin (F-actin) is complexed with cationic membranes 
    (Wong, 2000)

All of the structures listed above are templated by the original multilamellar phase of the lipid bi-layers and the biopolymers absorb on the membranes and between the membranes. Polyelectrolyte layers hat form on cationic lipid membranes increase in order as polymer diameter and ridity are increased.

  Microtubules (MTs) are negatively charged supramolecular polymers, which self-assemble from tubulin protein subunits into hollow cylinders. MTs are critical in many functions in eukaryotic cells: for instance, they are pathways for neurotransmitter precursors and enzymes to synaptic junctions in nerve cells.
  Needleman et al study the interactions between MTs and cationic lipid bilayers to understand the interplay between electrostatic and elastic interactions governing lipids and biopolymers. In this case the electrostatic interactions of MTs dominate and MTs form the template for the complex structure.