Asymmetric Molecular Friction in Supported Phospholipid Bilayers Revealed by NMR Measurements of Lipid Diffusion

Abstract

The bilayer−substrate coupling in fluid bilayers of dipalmitoyl phosphatidylcholine (DPPC) on a solid support of spherical silica beads was examined by measuring the lateral diffusion of the lipids in both monolayers using a deuterium NMR relaxation technique. The results obtained at 55 °C show that the lipid diffusion constant in the monolayer facing the silica surface, D = 7.5 × 10-12 m2/s, is slower by a factor of 2 than that in the monolayer exposed to the bulk water (D = 14 × 10-12 m2/s). This indicates that the monolayer−monolayer coupling in fluid bilayers must be rather weak compared to the monolayer−substrate coupling across an ultrathin water film between the bilayer and the silica surface.

Unraveling lipid/protein interaction in model lipid bilayers by Atomic Force Microscopy

“…In literature, different results can be found. Hetzer et al (1998) found that the distal leaflet has a diffusion constant which is two times faster than the proximal leaflet, pointing to an independent behavior of the two leaflets. Recent results found the same translational diffusion coefficient for both leaflets within a 10% experimental uncertainty (Zhang and Granick, 2005).…”

Model Bio‐Membranes Investigated by AFM and AFS: A Suitable Tool to Unravel Lipid Organization and their Interaction with Proteins

“…In the literature, diff erent results can be found. Hetzer et al [60] found that the outer leafl et has a diff usion constant which is two times faster than the inner leafl et, pointing to an independent behavior of the two leafl ets. Recent results found the same translational diff usion coeffi cient for both leafl ets within a 10% experimental uncertainty [61].…”

4 Electrochemistry of Biomimetic Membranes

“…Frictional or electro-static coupling between the support and at least the proximal leaflet of the lipid bilayer may induce undesirable asymmetries in compositional, structural, mechanical and dynamic properties of the lipid bilayer. 131 The lubrification effect of the water layer imparts a significant long-range lateral mobility to the lipid bilayer. However, significant frictional coupling between the bilayer and the underlying substrate slows down lateral diffusion, which may be accompanied by a breakdown of the two-dimensional fluid nature of the membrane.…”