Influence of NaCl on the Structure and Dynamics of Phospholipid Layers

Abstract

We present a structural and dynamical analysis of the influence of NaCl on multilayer stacks of phospholipids on a solid surface. To this end, multilayer stacks of phospholipids (L-α-phosphatidylcholine, abbreviated as SoyPC) are investigated with neutron reflectometry, grazing-incidence small-angle neutron scattering (GISANS) and grazing-incidence neutron-spin echo spectroscopy (GINSES). We show both that the NaCl influence on the structure is predominantly on water-head group interface and also, that the change in dynamics is restricted to an associated change in the inter-plane viscosity. Using this knowledge, it is possible to model the dynamical behavior of a phospholipid membrane in response to a salt concentration of the solvent using only a single parameter, namely the in-plane viscosity. The excellent agreement with our previously published model also strongly supports the existence of a thermally excited surface mode in phospholipid membranes for close-to-physiological conditions.

MembraneDyn: simulating the dynamics of supported membrane stacks on the nanosecond timescale

“…In contrast to the layer compression modulus, the layer sliding viscosity cannot be determined from X-ray or neutron reflectivity measurements. In a recent GINSES study of the effects of salt concentration on the behaviour of a lipid membrane stack, the MembaneDyn program was used to show that the layer sliding viscosity decreases with the addition of NaCl (Jaksch et al, 2021).…”

Using Grazing-Incidence Small-Angle Neutron Scattering to Study the Orientation of Block Copolymer Morphologies in Thin Films

“…GISANS has since been widely used to study micelles − and other nanomaterials near surfaces and interfaces . GISANS has also been used to study phospholipid membranes. − Microphase-separated morphologies of block copolymers were investigated by GISANS with depth sensitivity. , The morphologies near the film interfaces were also selectively probed. − Time-of-flight GISANS allowed scattering at different wavelengths to be collected during one single measurement with a white beam, providing new measurement opportunities. − Besides developing experimental methods, theories and software that allowed background subtraction and quantitative analysis of GISANS data also evolved during the same time. , …”

Lateral diffusion of lipids in the DMPG membrane across the anomalous melting regime: effects of NaCl

“…Hence, it is not surprising to find many studies focusing on the effects of salt on the biophysical properties of the lipid membrane using various experimental as well as computational techniques. [21][22][23][24][25][26][27] It is, however, interesting to note that, despite such extensive investigations, the effects of salts on the dynamics of the lipid membrane remain controversial even at present. For example, quasielastic neutron scattering (QENS), 28 as well as fluorescence correlation spectroscopy (FCS) experiment with molecular dynamics (MD) simulation, 22 has shown that addition of salt restricts the dynamics of the zwitterionic PC lipid bilayer.…”