Magnetic phospholipid tubes connected to magnetoliposomes: Pearling instability induced by a magnetic field.

We propose here a method to modify the membrane tension of phospholipid tubes with an applied magnetic field. The tubes are connected to giant liposomes capping the tubes at both ends. Tubes and liposomes are all filled with a magnetic fluid. The tension of the tube membrane is tuned by the deformation of the ending liposomes under the applied field. We modelize the magnetoliposome deformation and we are then able to describe the tube evolution. At low magnetic fields, the tube remains at equilibrium with a cylindrical shape and a uniform radius. It responds to an increase of membrane tension by a diameter reduction. Above a magnetic-field threshold, the cylindrical shape becomes unstable with respect to a pearling deformation. The tube shape then selected by the system is an unduloid, with a constant mean curvature equal to C 0, the spontaneous curvature of the membrane.