Element-specific density profiles in interacting biomembrane models

Abstract

Surface interactions involving biomembranes, such as cell-cell interactions or membrane contacts inside cells play important roles in numerous biological processes. Structural insight into the interacting surfaces is a prerequisite to understand the interaction characteristics as well as the underlying physical mechanisms. Here, we work with simplified planar experimental models of membrane surfaces, composed of lipids and lipopolymers. Their interaction is quantified in terms of pressure-distance curves using ellipsometry at controlled dehydrating (interaction) pressures. For selected pressures, their internal structure is investigated by standing-wave x-ray fluorescence (SWXF). This technique yields specific density profiles of the chemical elements P and S belonging to lipid headgroups and polymer chains, as well as counter-ion profiles for charged surfaces.

Investigating the Conformation of Surface-Adsorbed Proteins with Standing-Wave X-ray Fluorescence

“…The influence of a variation of the parameters z 0 and w on the calculated curves is illustrated in the Supporting Information. As already discussed in our previous studies, 34,35 SWXF is sensitive mainly to the first and second moments of an elemental distribution. In other words, a similar fit quality would result from the assumption of a box-like elemental distribution as long as it has the same center-of-mass position and the same second moment σ 2 = ⟨(z − z 0 ) 2 ⟩ = w 2 .…”

Neutron reflectometry yields distance-dependent structures of nanometric polymer brushes interacting across water

“…In the future, valuable experimental data on brush conformations can be expected from element-specific structural investigations, 50 which are sensitive, for instance, to the endpoint-distributions in interacting brushes. 24…”

“…23 Via controlled dehydration our double-monolayer configuration enables the tunable approach of the two surfaces and the separation-dependent structural investigation. 24 The monolayers are composed of lipids and lipopolymers ( Fig. 1A), supported by a hydrophobized planar solid on one side, but free-standing on the other side ( Fig.…”

Synchrotron Scattering Methods for Nanomaterials and Soft Matter Research

“…In situ and real-time GIXF and GID study of the structural rearrangement in a model membrane (an arachidic acid monolayer) on a colloidal solution of cerium dioxide or magnetite showed that the character of the interaction of nanoparticles with the monolayer is determined by their chemical nature and size [172]. The interaction of membrane surfaces composed of lipids and lipopolymers was quantified at controlled dehydrating pressures using GIXF [173]. This technique yielded specific density profiles of the chemical elements P and S belonging to lipid headgroups and polymer chains, as well as counterion profiles for charged surfaces.…”