Steric Interaction of Fluid Membranes in Multilayer Systems

Abstract

The out-of-plane fluctuations of fluid membranes are sterically hindered in multilayer systems. The repulsive interaction associated with the steric or excluded-volume effect is studied theoretically by two methods. The interaction energy per unit area of membrane is derived as a function of temperature, membrane curvature elasticity and mean membrane spacing; it is inversely proportional to the square of the latter. Steric repulsion is estimated for lecithin bilayers in water. There and in other cases, it may compete with van der Waals attraction.

The structural diversity of DNA–neutral phospholipids–divalent metal cations aggregates: a small-angle synchrotron X-ray diffraction study

“…In the fully hydrated pure phospholipid bilayers, the strength of undulatory fluctuations is proportional to the square of the temperature (Helfrich, 1978). These fluctuations cause disorder in the relative position of unit cells (long-range disorder) resulting in broadening of diffraction peaks, and the magnitude of this effect increases with increasing diffraction order (Zhang et al, 1996;Petrache et al, 1998;Gordeliy et al, 2005).…”

Hydration of POPC bilayers studied by 1H-PFG-MAS-NOESY and neutron diffraction

“…NMR investigations revealed that water molecules at the lipid water interface are partially oriented due to an interaction with the lipid water interface (Gawrisch et al 1992) which could be the origin of a repulsive hydration force (Leikin and Kornyshev 1990). But the chemical potential of water may also be lowered by bilayer undulations (Helfrich 1978), by electrostatic repulsion between charged bilayers (Cowley et al 1978) and by entropically-driven movements of individual lipids or lipid segments along the bilayer normal (Israelachvili and Wennerström 1996). Repulsive forces between bilayers play a major role in cell fusion, one of the most fundamental biological processes (Arnold and Gawrisch 1993).…”

Orientation transition of defective lyotropic triblock copolymer lamellar phase

“…Ramaswamy argued that the suppression of undulations triggers the transition [13]. Lyotropic lamellar phase is stabilized by a steric repulsive force arising from undulation fluctuation [18]. As a result of the suppression of the undulation fluctuation by shear flow, reduction of the repulsive force will induce the instability.…”

“…The HelfrichHurault effect is undulation instability of the smectic phase subjected to the external electric or magnetic field [17]. In the thermal equilibrium state, the undulation fluctuation yields repulsive Helfrich interaction between membranes which stabilizes the lamellar phase [18]. Suppression of the undulation fluctuation by shearing will reduce the repulsive force and destabilize lamellar membranes which causes the reduction of layer spacing.…”