Instability of myelin tubes under dehydration: Deswelling of layered cylindrical structures - art. no. 050903

We report experimental observations of an undulational instability of myeli n figures. Motivated by this, we examine theoretically the deformation and possible instability of concentric, cylindrical, multilamellar membrane str uctures. Under conditions of osmotic stress (swelling or dehydration), we f ind a stable, deformed state in which the layer deformation is given by del taR proportional tor(rootB A/(hB)), where B-A is the area compression modul us, B is the interlayer compression modulus, and h is the repeat distance o f layers. Also, above a finite threshold of dehydration (or osmotic stress) , we find that the system becomes unstable to undulations, first with a cha racteristic wavelength of order root xid(0), where xi is the standard smect ic penetration depth and d(0) is the thickness of dehydrated region.