Membrane Adhesion via Homophilic Saccharide-Saccharide Interactions Investigated by Neutron Scattering

Abstract

Solid-supported membrane multilayers doped with membrane-anchored oligosaccharides bearing the LewisX motif (Le(X) lipid) were utilized as a model system of membrane adhesion mediated via homophilic carbohydrate-carbohydrate interactions. Specular and off-specular neutron scattering in bulk aqueous electrolytes allowed us to study multilayer structure and membrane mechanics at full hydration at various Ca(2+) concentrations, indicating that membrane-anchored Le(X) cross-links the adjacent membranes. To estimate forces and energies required for cross-linking, we theoretically modeled the interactions between phospholipid membranes and compared this model with our experimental results on membranes doped with Le(X) lipids. We demonstrated that the bending rigidity, extracted from the off-specular scattering signals, is not significantly influenced by the molar fraction of Le(X) lipids, while the vertical compression modulus (and thus the intermembrane confinement) increases with the molar fraction of Le(X) lipids.

Influence of length and conformation of saccharide head groups on the mechanics of glycolipid membranes: Unraveled by off-specular neutron scattering

“…Note that the cutoff radius R, corresponding to the finite size of the sample, was found from the data fitting to be 1.8 µm, which is in good agreement with the values reported in our previous studies. [19][20][21] The best fit results (Fig. 7, red lines) yielded λ = 12 Å and η = 1.8 × 10 −2 , corresponding to κ = 17 k B T and B = 8.4 MPa according to Eqs.…”

“…difference between κ D−Gent and κ D−Lac1 = 32 k B T can instead be interpreted in terms of the decrease in intra-membrane interactions between the head groups caused by the entropic contribution derived from less ordered lateral packing due to their "bent" structure, which could be identified from a clear difference in T m ; T m Lac1 = 74 • C and T m Gent = 45 • C. 3,19 Second, the mechanical parameters of D-Gb3 membranes were compared with DPPC membranes measured under identical conditions (60 • C, h rel ∼ 95%). 21 The compression modulus of D-DPPC B D−DPPC = 48 MPa is more than 5-fold that of D-Gb3. Although the comparison under osmotic pressure (and thus not in the presence of bulk water) must be discussed carefully, the significant difference observed here suggests a distinct contribution of saccharide groups to intermembrane interactions.…”

“…[19][20][21] B reflects the sharpness of the inter-membrane interaction potential that determines membrane confinement, while κ reflects the intramembrane interaction between Gb3 glycolipid molecules. For systematic comparison, all the values presented here are obtained from molecules whose hydrophobic chains are fully deuterated dihexadecyl chains in the fluid Lα phase.…”

“…Electronic addresses: ayamamoto@icems.kyoto-u.ac.jp and tanaka@uni-heidelberg.de protectors to sustain the structural integrity as well as specific ligands for proteins and complementary saccharides, 17,18 we have previously proposed more realistic model systems based on synthetic and natural glycolipids. [19][20][21] We demonstrated that the introduction of finite size effects, the so-called "cut-off radius," 22 allows full calculation of the scattering functions in reciprocal space and quantification of the vertical compression modulus B and the bending rigidity κ of the membranes. We reported that small changes in the molecular structures of the saccharide chains, such as the position and stereochemistry of the glycosidic bonds, significantly influence the mechanical properties of its membrane multilayer.…”

“…19 This strategy has been further extended to understand the impact of genetic mutation on the mechanics of membranes composed of bacterial lipopolysaccharides 20 as well as to quantify the physical role of weak saccharide-saccharide interactions in modulating membrane adhesion processes, namely, intermembrane potentials. 21 In this account, we physically model the impact of glycolipid on the membrane mechanics which leads to human diseases, such as toxin uptake and metabolic disorders. As a model of glycolipid, we synthesized a lipid with a globotriaose (α-galactose(1-4)-β-galactose(1-4)-β-glucose, Gb3) head group.…”