This is an up-close look at "smart" bio-nanotubes. Lipid protein nanotubes are made of microtuble protein (with the tubulin protein subunits shown as red-blue-yellow-green objects) that is coated by a lipid bilayer (drawn with yellow tails and green and white spherical heads.) The bilayer, in turn, is coated by tubulin protein rings or spirals. By controlling the relative amount of lipid and protein it is possible to switch between two states of nanotubes with either open ends (shown in the center) or closed ends with lipid caps (shown on the left), a process which forms the basis for controlled chemical and drug encapsulation and release. A top view of the nanotubes and a magnified region is shown on the right.
Credit: Peter Allen, University of California, Santa Barbara