Dataset Information

Intrinsic Curvature-Mediated Transbilayer Coupling in Asymmetric Lipid Vesicles.

ABSTRACT: We measured the effect of intrinsic lipid curvature, J₀, on structural properties of asymmetric vesicles made of palmitoyl-oleoyl-phosphatidylethanolamine (POPE; J₀<0) and palmitoyl-oleoyl-phosphatidylcholine (POPC; J₀?0). Electron microscopy and dynamic light scattering were used to determine vesicle size and morphology, and x-ray and neutron scattering, combined with calorimetric experiments and solution NMR, yielded insights into leaflet-specific lipid packing and melting processes. Below the lipid melting temperature we observed strong interleaflet coupling in asymmetric vesicles with POPE inner bilayer leaflets and outer leaflets enriched in POPC. This lipid arrangement manifested itself by lipids melting cooperatively in both leaflets, and a rearrangement of lipid packing in both monolayers. On the other hand, no coupling was observed in vesicles with POPC inner bilayer leaflets and outer leaflets enriched in POPE. In this case, the leaflets melted independently and did not affect each other's acyl chain packing. Furthermore, we found no evidence for transbilayer structural coupling above the melting temperature of either sample preparation. Our results are consistent with the energetically preferred location of POPE residing in the inner leaflet, where it also resides in natural membranes, most likely causing the coupling of both leaflets. The loss of this coupling in the fluid bilayers is most likely the result of entropic contributions.

SUBMITTER: Eicher B

PROVIDER: S-EPMC5773765 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Intrinsic Curvature-Mediated Transbilayer Coupling in Asymmetric Lipid Vesicles.

Eicher Barbara B Marquardt Drew D Heberle Frederick A FA Letofsky-Papst Ilse I Rechberger Gerald N GN Appavou Marie-Sousai MS Katsaras John J Pabst Georg G

Biophysical journal 20180101 1

We measured the effect of intrinsic lipid curvature, J0, on structural properties of asymmetric vesicles made of palmitoyl-oleoyl-phosphatidylethanolamine (POPE; J0<0) and palmitoyl-oleoyl-phosphatidylcholine (POPC; J0∼0). Electron microscopy and dynamic light scattering were used to determine vesicle size and morphology, and x-ray and neutron scattering, combined with calorimetric experiments and solution NMR, yielded insights into leaflet-specific lipid packing ...[more]

PMID: 29320681

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Project description:Using Förster resonance energy transfer, raft/liquid-ordered-domain formation was assessed in asymmetric vesicles containing outer leaflets composed of high-Tm (melting temperature) saturated phosphatidylcholines (diC18:0PC, diC16:0PC, diC15:0PC, or diC14:0PC), low-Tm unsaturated dioleoylphosphatidylcholine (DOPC) and cholesterol, and inner leaflets composed of lipids that by themselves would not form ordered domains (DOPC and cholesterol). Ordered-domain formation in the outer leaflet was compared to that in symmetric vesicles with the same lipid composition as the asymmetric vesicle outer leaflets. The difference between ordered-domain thermal stability in asymmetric and symmetric vesicles was highly dependent on high-Tm PC acyl-chain length. At one extreme, in diC14:0PC-containing asymmetric vesicles, the outer leaflet did not segregate to form ordered domains over the entire experimental temperature range even though ordered domains formed in the symmetric vesicles, indicating the inner leaflet dominated outer-leaflet physical behavior in the asymmetric vesicles. At the other extreme, in diC18:0PC-containing asymmetric vesicles, ordered domains formed over the entire temperature range at which they were present in symmetric vesicles, indicating the inner leaflet did not dominate outer-leaflet physical behavior. DiC15:0PC- and diC16:0PC-containing vesicles exhibited intermediate behaviors. A different set of vesicles was prepared with high-Tm lipid sphingomyelin (SM) in place of saturated phosphatidylcholine, and the % SM was varied. The thermal stability of outer-leaflet ordered domains in asymmetric vesicles was found to decrease more than in symmetric vesicles as SM levels decreased, indicating that the inner leaflet increasingly dominated outer leaflet physical state as SM levels decreased. Overall, inhibition of outer-leaflet ordered-domain formation in asymmetric vesicles by inner-leaflet lipids decreased as the ability of outer-leaflet lipids to form an ordered state by themselves increased, i.e., when outer-leaflet high-Tm lipid content or acyl-chain length increased. This has implications for how ordered-domain formation may be controlled in vivo.

Dataset Information

Intrinsic Curvature-Mediated Transbilayer Coupling in Asymmetric Lipid Vesicles.

Publications

Intrinsic Curvature-Mediated Transbilayer Coupling in Asymmetric Lipid Vesicles.

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