I review the results of an experimental and theoretical study of the effects of polymers having a number of hydrophobic anchors grafted along a hydrophilic backbone on phospholipid vesicles of different geometries. Pearling of tubular vesicles, tubulation at the rim of highly oblate vesicles, and finally a coiling instability in highly multilamellar tubes have been observed, above threshold polymer concentrations. These instabilities can be accounted for within a single framework in which the local polymer concentration is coupled to local membrane curvature, and in which polymers effect these changes by inducing curvature in the bilayers on which they anchor. Curvature is induced by two mechanisms: a local deformation due to anchoring, and an increase in the area of one leaflet of a bilayer with respect to the other.
