  We study experimentally a coiling instability of cylindrical multilamellar
stacks of phospholipid membranes, induced by polymers with hydrophobic anchors
grafted along their hydrophilic backbone. We interpret our experimental results
in terms of a model, in which local membrane curvature and polymer
concentration are coupled. The model predicts the occurence of maximally tight
coils above a threshold anchor occupancy. Indeed, only maximally tight coils
are observed experimentally. Our system is unique in that coils form in the
absence of twist.
